Measuring the velocity of small moving objects such as cells

• US 6,507,391 B2
• Filed: 08/24/2001
• Issued: 01/14/2003
• Est. Priority Date: 08/25/2000
• Status: Expired due to Term

• Current Assignee: Cytek Biosciences Inc
• Original Assignee: Amnis Corporation (DiaSorin S.p.A.)
• Inventors: Perry, David J., Bauer, Richard A., Basiji, David A., Ortyn, William E., Frost, Keith L., Riley, James K.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/939,049
• Publication Number:
  US 20020122167A1
• Time in Patent Office: 508 Days
• Field of Search: 356/28, 356/28.5, 356/39
• US Class Current: 356/28
• CPC Class Codes: G01N 15/1012 Calibrating particle analysers; References therefor
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 15/147 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2015/1014 Constitution of reference particles
• CPC Class Codes: G01N 2015/1016 Particle flow simulating, e.g. liquid crystal cell
• CPC Class Codes: G01N 2015/1027 Determining speed or velocity of a particle
• CPC Class Codes: G01N 2015/144 Imaging characterised by its optical setup
• CPC Class Codes: G01N 2015/1443 Auxiliary imaging
• CPC Class Codes: G01N 2015/1447 Spatial selection
• CPC Class Codes: G01N 2015/1452 Adjustment of focus; Alignment
• CPC Class Codes: G01N 2015/1497 Particle shape
• CPC Class Codes: G02B 27/0012 Optical design, e.g. procedures, algorithms, optimisation routines
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51

Abstract

Frequency domain velocity measurements and time domain velocity measurements are made using light from cells or other objects. An optical grating is used to modulate the light from an object so that it has a frequency proportional to the velocity of the object. Depending upon the embodiment, the pitch of the optical grating is uniform or varying. The modulated light is detected, producing an analog signal that is then digitally sampled. Time domain signal processing techniques are used to determine the velocity of the object from the digital samples. Preferably, the velocity measured is applied in determining a timing signal employed for synchronization of an image of the object and an detector signal in an optical analysis system that uses a time delay integration (TDI) detector to determine characteristics of the object in response to light from the object.

Claims

1. A velocity measurement system for determining an indication of a velocity of an object passing through a field of view, comprising:

(a) an optical element disposed to direct light traveling from an object passing through the field of view along a collection path;

(b) at least one optical grating of substantially uniform pitch disposed in the collection path, said at least one optical grating modulating the light traveling along the collection path to produce modulated light having a modulation frequency proportional to a velocity of an object passing through the field of view;

(c) at least one light sensitive detector on which the modulated light is incident, said at least one light sensitive detector producing an electrical signal responsive to the modulated light;

(d) means for processing the electrical signal in the time domain to determine the indication of the velocity.

2. The measurement system of claim 1, wherein a pitch of the optical grating is varied to compensate for distortion due to the optical element.

3. A velocity measurement system for determining an indication of a velocity of an object passing through a field of view, comprising:

(a) an optical element disposed so that light traveling from an object passing through the field of view is directed along a collection path;

(b) an optical grating disposed in the collection path, said optical grating modulating the light traveling along the collection path, to produce modulated light having a modulation frequency corresponding to a velocity of an object passing through the field of view;

(c) a light sensitive detector disposed to receive the modulated light, said light sensitive detector responding to the modulated light by producing a corresponding electrical signal;

(d) means coupled to said light sensitive detector, for converting the electrical signal into a sequence of digital samples; and

(e) means in receipt of the sequence of digital samples, for processing the sequence of digital samples in the time domain to determine the indication of the velocity of an object.

4. The measurement system of claim 3, wherein said means for converting the electrical signal into a sequence of digital samples comprises an analog-to-digital converter.

5. The measurement system of claim 3, further comprising an amplifier coupled to said light sensitive detector, for amplifying the electrical signal before it is converted into the sequence of digital samples.

6. The measurement system of claim 3, further comprising a bandpass filter coupled to the light sensitive detector, for filtering the electrical signal before it is converted into the sequence of digital samples.

7. The measurement system of claim 3, wherein said means for processing the sequence of digital samples comprises at least one of a programmed computing device, an application specific integrated circuit, and a digital oscilloscope.

8. The measurement system of claim 3, further comprising a system controller that is coupled to and controls the means for converting the electrical signal into the sequence of digital samples, and the means for processing the sequence of digital samples, said system controller comprising at least one of a programmed computing device and an application specific integrated circuit.

9. The measurement system of claim 8, wherein said system controller includes means for performing at least one of the following functions:

(a) regulating an amplitude of said electrical signal;

(b) determining a signal-to-noise ratio of the electrical signal and rejecting any indication of the velocity determined if the signal-to-noise ratio is less than a predetermined threshold; and

(c) regulating a local oscillation frequency employed by the means for processing in response to variations in the indication of the velocity of an object that is determined.

10. The measurement system of claim 3 in which the light from an object passing through the field of view comprises at least one of light scattered by an object, an unstimulated emission from an object, and a stimulated emission from an object.

11. The measurement system of claim 3, wherein said optical grating comprises an optical grating having a substantially uniform pitch, and wherein said means for converting the electrical signal into a sequence of digital samples comprises:

(a) an amplifier having an input that is coupled to said light sensitive detector and an output, said amplifier amplifying the electrical signal, produces an amplified electrical signal at its output;

(b) a bandpass filter coupled to the output of the amplifier, said bandpass filter filtering the amplified electrical signal to produce a passband signal; and

(c) a first analog baseband converter and analog-to-digital converter that converts the passband signal to a first sequence of digital samples, such that the first sequence of digital samples represents a real part of the electrical signal; and

(d) a second analog baseband converter and analog-to-digital converter that converts the passband signal to a second sequence of digital samples, such that the second sequence of digital samples represents an imaginary part of the electrical signal.

12. The measurement system of claim 3, wherein said optical grating has a uniform pitch, and wherein said means for processing the sequence of digital samples determines the indication of the velocity from a first derivative of a time series of phase samples of the electrical signal, after calculating those phase samples from a baseband complex representation of the electrical signal.

13. The measurement system of claim 3, wherein said optical grating has a non uniform pitch.

14. The measurement system of claim 13, wherein said optical grating comprises a plurality of alternating opaque bars and transparent gaps, widths of which vary in a linear progression in a direction perpendicular to a longitudinal extent of the plurality of alternating opaque bars and transparent gaps.

15. The measurement system of claim 13, wherein said optical grating comprises a plurality of alternating opaque bars and transparent gaps, widths of which vary in a non-linear pattern in a direction perpendicular to a longitudinal extent of the plurality of alternating opaque bars and transparent gaps.

16. The measurement system of claim 13, wherein said optical grating comprises two substantially identical sections, each section having a non-uniform pattern of bar and gap widths, disposed along an axis of motion of an object, such that an object traverses said sections sequentially.

17. The measurement system of claim 13, further comprising:

(a) a beam splitter that is disposed in the collection path, such that a portion of the light traveling from an object along the collection path is diverted along a second collection path;

(b) another optical grating disposed in the second collection path, said other optical grating having a non uniform pitch and modulating the light traveling along the second collection path, to produce modulated light having a modulation frequency corresponding to a velocity of an object passing through the field of view; and

(c) another light sensitive detector disposed in the second collection path, said other light sensitive detector converting the modulated light from said at least one other optical grating into a second electrical signal.

18. The measurement system of claim 17, wherein said means for converting the electrical signal into a sequence of digital samples comprises:

(a) a first amplifier having an input that is coupled to said at least one light sensitive detector disposed in the collection path to receive the electrical signal, and an output, said first amplifier amplifying the electrical signal, producing an amplified electrical signal at its output;

(b) a first bandpass filter coupled to the output of the first amplifier, said first bandpass filter filtering the amplified electrical signal to produce a passband signal;

(c) a first analog-to-digital converter that converts the passband signal to a first sequence of digital samples;

(d) a second amplifier having an input that is coupled to said other light sensitive detector disposed in the second collection path, and an output, said second amplifier amplifying the second electrical signal, producing a second amplified electrical signal at its output;

(e) a second bandpass filter coupled to the output of the second amplifier, said second bandpass filter filtering the second amplified electrical signal to produce a second passband signal; and

(f) a second analog-to-digital converter that converts the second passband signal to a second sequence of digital samples.

19. The measurement system of claim 17, wherein said means for converting the electrical signal into a sequence of digital samples comprises:

(a) a first amplifier having an input that is coupled to said light sensitive detector disposed in the collection path, and an output, said first amplifier amplifying the electrical signal, producing an amplified electrical signal at its output;

(b) a first analog-to-digital converter that converts the amplified electrical signal to a first sequence of digital samples;

(c) a first digital bandpass filter for rejecting a direct current bias and a high frequency noise component from the first sequence of digital samples;

(d) a second amplifier having an input that is coupled to said other light sensitive detector disposed in the second collection path, and an output, said second amplifier amplifying the second electrical signal, producing a second amplified electrical signal at its output;

(e) a second analog-to-digital converter that converts the second amplified electrical signal to a second sequence of digital samples; and

(f) a second digital bandpass filter for rejecting a direct current bias and a high frequency noise component from the second sequence of digital samples.

20. The measurement system of claim 17, wherein each optical grating is aligned in series along an axis of motion of an object, and wherein said means for processing the sequence of digital samples to determine the indication of the velocity of an object calculates an amplitude peak of a cross-correlogram generated by a convolution of the electrical signal from said light sensitive detector disposed in the collection path with the second electrical signal from said other light sensitive detector disposed in the second collection path.

21. The measurement system of claim 17, further comprising a control system controllably connected to said means for converting the electrical signal into a sequence of digital samples and said means for processing the sequence of digital samples.

22. The measurement system of claim 21, wherein said control system regulates:

(a) a gain of the first amplifier and the second amplifier in response to varying levels of the electrical signal and the second electrical signal, respectively; and

(b) an upper and a lower limit of time shifting in a cross-correlation operation in response to variations in the velocity of an object.

23. The measurement system of claim 3, further comprising at least one light source for illuminating the field of view.

24. The measurement system of claim 23, wherein said at least one light source is disposed to provide an incident light that illuminates an object passing through the field of view.

25. The measurement system of claim 24, wherein said incident light stimulates at least one of an emission and a fluorescence from an object passing through the field of view, and the light from the object passing through the field of view comprises one of an emitted light and a fluoresced light.

26. The measurement system of claim 24, wherein the incident light is at least partially absorbed by an object passing through the field of view, so that the light from an object has been changed due to the absorption by an object.

27. The measurement system of claim 24, wherein the light is reflected from an object passing through the field of view toward the optical element.

28. The measurement system of claim 23, wherein the light source comprises at least one of a coherent light source, a non-coherent light source, a pulsed light source, a continuous light source, a continuous wave laser, a pulsed laser, a continuous wave incandescent lamp, a strobe arc lamp, and an optical filter that provides a limited spectrum of light for illuminating an object.

29. The measurement system of claim 3, further comprising a source of a reference field light, wherein an intensity of the light from an object passing through the field of view is modulated by a phase interference with the reference field light.

30. The measurement system of claim 3, wherein a flow of a fluid in which objects are entrained passes through the field of view, such that an indication of a velocity of an object entrained in the fluid is determined by the means for processing.

31. The measurement system of claim 3, wherein a support on which a plurality of objects are disposed passes through the field of view, such that an indication of a velocity of an object on the support and thus, of the support, is determined by the means for processing.

32. The measurement system of claim 3, wherein said optical element comprises a lens.

33. The measurement system of claim 3, wherein the other light sensitive detector and a dispersing element that directs the light from the optical element to each of the light sensitive detectors.

34. The measurement system of claim 33, wherein the other light sensitive detector is employed to determine a characteristic of an object passing through the field of view, other than an indication of a velocity of an object.

35. The measurement system of claim 3, wherein an object passes through another field of view, further comprising:

(a) another optical element disposed to direct light from an object passing through the other field of view along another collection path; and

(b) another light sensitive detector disposed to receive the light traveling along the other collection path and employed to determine a characteristic of an object passing through the other field of view, said characteristic being other than the indication of the velocity of an object.

36. The measurement system of claim 3, further comprising means disposed downstream from said field of view, for sorting objects.

37. The measurement system of claim 3, wherein said light sensitive detector comprises one of a photosensitive diode and a photomultiplier tube.

38. The measurement system of claim 3, further comprising a fluid supply disposed upstream of the field of view, said fluid supply providing the field of view with a flow of a fluid in which a plurality of objects are entrained.

39. The measurement system of claim 38, wherein each of the plurality of objects comprises one of a biological cell and a particulate component of a biological specimen.

40. The measurement system of claim 3, further comprising a solid support on which a plurality of objects are disposed, and a prime mover, said solid support being moved through the field of view by the prime mover.

41. An optical analysis system employed to determine an indication of a velocity of a relative movement between an object and the optical analysis system, and to determine at least one additional characteristic of the object, comprising:

(a) a first optical element disposed to direct light from an object along a first collection path;

(b) a second optical element disposed in the first collection path to direct a portion of the light traveling along the first collection path, along a second collection path;

(c) an optical grating disposed in the second collection path, said optical grating modulating the light traveling along the second collection path, producing modulated light that has a modulation frequency corresponding to a velocity of the relative movement between the object and the optical analysis system;

(d) a light sensitive detector disposed in the second collection path to receive the modulated light, said at least one light sensitive detector producing an electrical signal in response to the modulated light;

(e) means coupled to the light sensitive detector to receive the electrical signal, for determining the indication of the velocity of the relative movement between the object and the optical analysis system as a function of the electrical signal and producing a timing signal as a function of said indication of the velocity;

(f) a time delay integration (TDI) detector disposed to receive light traveling along the first collection path, said TDI detector being coupled to said means for determining the indication of the velocity, said TDI detector employing the timing signal to produce an output signal that is indicative of said at least one additional characteristic of the object.

42. The optical analysis system of claim 41, further comprising a control that is coupled to and controls the means for determining the indication of the velocity, and the TDI detector.

43. The optical analysis system of claim 41, wherein said optical grating has a substantially uniform pitch.

44. The optical analysis system of claim 43, wherein said means for determining the indication of the velocity of the relative movement between the object and the optical analysis system comprises:

(a) an amplifier having an input that is coupled to the light sensitive detector disposed in the second collector path and an output, said amplifier amplifying the electrical signal, producing an amplified electrical signal at its output;

(b) an analog-to-digital converter that converts the amplified electrical signal to a sequence of digital samples; and

(c) processing means for processing the sequence of digital samples to determine the indication of the velocity of the object.

45. The optical analysis system of claim 43, wherein said means for determining the indication of the velocity of the relative movement between the object and the optical analysis system comprises:

(a) an amplifier having an input that is coupled to the light sensitive detector disposed in the second collector path and an output, said amplifier amplifying the electrical signal, producing an amplified electrical signal at its output;

(b) a bandpass filter coupled to the output of the amplifier, said bandpass filter filtering the amplified electrical signal to produce a passband signal; and

(c) a first analog baseband converter and analog-to-digital converter that converts the passband signal to a first sequence of digital samples, such that the first sequence of digital samples represents a real part of the electrical signal, and

(d) a second analog baseband converter and analog-to-digital converter that converts a portion of the passband signal into a second sequence of digital samples, such that the second sequence of digital samples represents an imaginary part of the electrical signal, and

(e) processing means for processing the first and second sequences of digital samples to determine the indication of the velocity of the relative movement between the object and the optical analysis system.

46. The optical analysis system of claim 44, wherein said processing means calculates a time series of phase samples from a baseband complex representation that is derived from the sequence of digital samples.

47. The optical analysis system of claim 41, wherein said optical grating disposed in the second collection path has a substantially non uniform pitch.

48. The optical system of claim 47, wherein said optical grating disposed in the second collection path comprises at least one of:

(a) a plurality of alternating opaque bars and transparent gaps, widths of which vary in a linear progression in a direction perpendicular to a longitudinal extent of the plurality of alternating opaque bars and transparent gaps; and

(b) a plurality of alternating opaque bars and transparent gaps, widths of which vary in a non-linear pattern in a direction perpendicular to a longitudinal extent of the plurality of alternating opaque bars and transparent gaps.

49. The optical analysis system of claim 47, wherein the optical grating disposed in the second collection path and having the substantially non uniform pitch comprises two substantially identical sections, each having a non-uniform pattern of bar and gap widths and disposed along an axis of motion of light from the object such that the light from the object traverses said sections sequentially.

50. The optical analysis system of claim 47, further comprising:

(a) a third optical element disposed in the second collection path, such that a portion of the light traveling from the object along the second collection path is diverted along a third collection path;

(b) an optical grating disposed in the third collection path and having a substantially non uniform pitch, said optical grating modulating the light, to produce modulated light having a modulation frequency corresponding to the velocity of the object passing through the field of view; and

(c) a light sensitive detector disposed in the third collection path and used to convert the modulated light traveling along the third collection path into a second electrical signal, said light sensitive detector being coupled to provide the second electrical signal to said means for determining the indication of the velocity of the relative movement between the object and the optical analysis system.

51. The optical analysis system of claim 50, wherein said means for determining the indication of the velocity of the relative movement between the object and the optical analysis system comprises:

(a) a first amplifier having an input that is coupled to the light sensitive detector disposed in the second collection path, and an output, said first amplifier amplifying the electrical signal, producing an amplified electrical signal at its output;

(b) a first bandpass filter coupled to the output of the first amplifier, said first bandpass filter filtering the amplified electrical signal provided by the first amplifier to produce a passband signal;

(c) a first analog-to-digital converter that converts the passband signal to a first sequence of digital samples;

(d) a second amplifier having an input that is coupled to the light sensitive detector disposed in the third collection path, and an output, said second amplifier amplifying the second electrical signal, producing a second amplified electrical signal at its output;

(e) a second bandpass filter coupled to the output of the second amplifier, said second bandpass filter filtering the second amplified electrical signal to produce a second passband signal;

(f) a second analog-to-digital converter that converts the second passband signal to a second sequence of digital samples; and

(g) processing means for processing each sequence of digital samples, to determine the indication of the velocity of the relative movement between the object and the optical analysis system.

52. The optical analysis system of claim 50, wherein said means for determining the indication of the velocity of the relative movement between the object and the optical analysis system comprises:

(a) a first amplifier having an input that is coupled to the light sensitive detector disposed in the second collection path, and an output, said first amplifier amplifying the electrical signal, producing a first amplified electrical signal at its output;

(b) a first analog-to-digital converter that converts the first amplified electrical signal to a first sequence of digital samples;

(c) a first digital bandpass filter for rejecting a direct current bias and a high frequency noise component from the first sequence of digital samples;

(d) a second amplifier having an input that is coupled to the light sensitive detector disposed in the third collection path, and an output, said second amplifier amplifying the second electrical signal, producing a second amplified electrical signal at its output;

(e) a second analog-to-digital converter that converts the second amplified electrical signal to a second sequence of digital samples;

(f) a second digital bandpass filter for rejecting a direct current bias and a high frequency noise component from the second sequence of digital samples;

(g) processing means for processing each sequence of digital samples, to determine the indication of the velocity between the object and the optical analysis system.

53. The optical analysis system of claim 50, wherein said means for determining the indication of the velocity of the relative movement between the object and the optical analysis system determines an amplitude peak of a cross-correlogram generated by a convolution of the electrical signal from the light sensitive detector disposed in the second collection path with the second electrical signal from the light sensitive detector disposed in the third collection path, so that an image field associated with the optical grating disposed in the second collection path and a second image field associated with the optical grating disposed in the third collection path are aligned in series along an axis of the relative movement between the object and the optical analysis system.

54. The optical analysis system of claim 51, wherein said processing means comprises at least one of a digital oscilloscope, a programmed computing device, and an application specific integrated circuit.

55. The optical analysis system of claim 52, further comprising a control system controllably connected to each amplifier and to said processing means, said control system regulating an upper and a lower limit of a time shifting employed in determining a cross-correlation in response to variations in the velocity of the relative movement between the object and the optical analysis system.

56. An imaging system adapted to determine an indication of a velocity of a relative movement between the imaging system and an object, and at least one additional characteristic of the object, comprising:

(a) an optical element disposed to direct light traveling from an object along a first collection path;

(b) a beam splitter disposed in the first collection path so that a portion of the light traveling from the object along the first collection path is diverted along a second collection path;

(c) an optical grating disposed in the second collection path, the optical grating modulating the collected light traveling along the second collection path, to produce modulated light having a modulation frequency corresponding to the velocity of the relative movement between the object and the imaging system;

(d) a light sensitive detector disposed in the second collection path to receive the modulated light, said light sensitive detector producing an electrical signal in response to the modulated light received along the second collection path;

(e) means coupled to the light sensitive detector, for determining the indication of the velocity of the relative movement between the object and the imaging system as a function of the electrical signal, said means producing a timing signal as a function of said indication of the velocity;

(f) an imaging lens disposed in the first collection path, producing an image from the light traveling along the first collection path; and

(g) a time delay integration (IDI) detector disposed in the first collection path to receive the image produced by the imaging lens, producing an output signal that is indicative of said at least one additional characteristic of the object, said TDI detector being coupled to the means for determining the indication of the velocity to receive the timing signal and producing the output signal by using the timing signal to provide a clocking function that synchronizes the TDI detector to a movement of the image of the object over the TDI detector so that a response to the light comprising the image is integrated over time as the image moves over the TDI detector.

57. An imaging system for determining an indication of a relative velocity and at least one additional characteristic of an object, from images of the object, while there is relative movement between the object and the imaging system, comprising:

(a) a light source that emits light illuminating the object;

(b) an optical element disposed to direct light from the object along a first collection path;

(c) a first beam splitter disposed in the first collection path so that light scattered from the object is directed along a different path, while light that is emitted by the object continues through the beam splitter along the first collection path;

(d) a second beam splitter disposed in the first collection path so that a portion of the light from the object traveling along the first collection path is diverted along a second collection path;

(e) an optical grating disposed in the second collection path, said optical grating modulating the light traveling along the second collection path, to produce modulated light having a modulation frequency corresponding to the velocity of the relative movement between the object and the imaging system;

(f) a light sensitive detector disposed to receive the modulated light, producing an electrical signal in response thereto;

(g) means coupled to the light sensitive detector to receive the electrical signal, for determining the indication of the relative velocity between the object and the imaging system and producing a timing signal as a function of said indication of the relative velocity;

(h) a spectral dispersing element disposed downstream of the second beam splitter in the first collection path, said spectral dispersing element spectrally dispersing the light emitted by the object, producing spectrally dispersed light;

(i) an optical element disposed to receive the spectrally dispersed light, producing an image thereof;

(j) a cylindrical lens disposed to receive the light scattered from the object, said cylindrical lens having a central axis around which the cylindrical lens is curved, said central axis being generally orthogonal to a direction of the relative movement between the object and the imaging system, so that the cylindrical lens produces a scattered pattern image of the object along a direction that is substantially parallel to said central axis of the cylindrical lens; and

(k) at least one time delay integration (TDI) detector disposed to receive the image, producing an output signal that is indicative of at least one characteristic of the object, and to receive the scattered pattern image produced by the cylindrical lens, producing a different output signal that is indicative of at least one other characteristic of the object, said at least one TDI detector being coupled to the means for determining the indication of the relative velocity of the movement between the object and the imaging system, said at least one TDI detector producing said output signals by using the timing signal for synchronization of said output signals with movement of the image and the scattered pattern image over said at least one TDI detector.

58. An optical analysis system employed to determine an indication of a velocity of a relative movement between an object and the optical analysis system and to determine and at least one other characteristic of the object, comprising:

(a) a first collection optical element disposed so that light from the object is directed along a first collection path;

(b) a first light dispersing optical element disposed in the first collection path so as to disperse the light traveling along the first collection path, producing first dispersed light;

(c) a first imaging optical element disposed to receive the first dispersed light, forming at least one image from the first dispersed light;

(d) a second collection optical element disposed to direct light from the object along a second collection path, different than the first collection path;

(e) a second light dispersing optical element disposed in the second collection path, so as to disperse the light traveling along the second collection path, producing second dispersed light;

(f) a second imaging optical element disposed to receive the second dispersed light, forming at least one image from said second dispersed light;

(g) a beam splitter that is disposed in one of the first collection path and the second collection path, so that a portion of the light traveling from the object along said one of the first collection path and the second collection path is diverted along a third collection path;

(h) an optical grating disposed in the third collection path, the optical grating modulating the light traveling along the third collection path, to produce modulated light having a modulation frequency corresponding to the velocity of the relative movement between the object and the optical analysis system;

(i) a light sensitive detector disposed in the third collection path to receive the modulated light, the light sensitive detector producing an electrical signal in response to the modulated light;

(j) means coupled to the light sensitive detector to receive the electrical signal, for determining the indication of the velocity of the relative movement between the object and the optical analysis system, producing a timing signal corresponding thereto;

(k) a first time delay integration (TDI) detector coupled to the means for determining the indication of the velocity to receive the timing signal and disposed to receive said at least one image formed by the first imaging optical element, said first TDI detector producing a first output signal that is indicative of at least one characteristic of the object by integrating said at least one image formed from the first dispersed light over time using the timing signal for synchronization of the first TDI detector with the movement over the first TDI detector of said at least one image formed by the first imaging optical element; and

(l) a second TDI detector disposed to receive said at least one image formed by the second imaging optical element, said second TDI detector being coupled to said means for determining the indication of the velocity to receive the timing signal and producing a second output signal that is indicative of at least one other characteristic of the moving object by integrating said at least one image formed from the second dispersed light over time using the timing signal for synchronization of the second TDI detector with the relative motion of said at least one image formed by the second imaging optical element.

59. A method for determining an indication of a velocity of an object in motion using light from the object, comprising the steps of:

(a) modulating light from the object using an optical grating to produce modulated light having a modulation frequency that varies as a function of the velocity of the object;

(b) producing an electrical signal corresponding to an intensity of the modulated light;

(c) processing the electrical signal in the time domain to determine the indication of the velocity of the object.

60. The method of claim 59, further comprising the step of amplifying the electrical signal before the step of processing.

61. The method of claim 59, further comprising the step of filtering the electrical signal before the step of processing.

62. The method of claim 61, wherein the step of filtering the electrical signal comprises the step of:

(a) removing a direct current bias from the electrical signal; and

(b) eliminating frequencies above a predetermined Nyquist limit from the electrical signal.

63. The method of claim 59, wherein the step of modulating light from the object using an optical grating comprises the step of utilizing an optical grating having a substantially uniform pattern.

64. The method of claim 63, further comprising the steps of:

(a) amplifying the electrical signal before the step of processing, producing an amplified signal;

(b) converting the amplified signal into a complex analog baseband signal;

(c) converting the complex analog baseband signal into a first digital sample sequence representing a real part of the amplified signal; and

(d) converting the complex analog baseband signal into a second digital sample sequence representing an imaginary part of the amplified signal.

65. The method of claim 63, further comprising the steps of:

(a) amplifying the electrical signal before the step of processing, producing an amplified signal;

(b) filtering the amplified signal, producing a passband signal;

(c) converting the passband signal into a complex analog baseband signal;

(d) converting the complex analog baseband signal into a first digital sample sequence representing a real part of the passband signal; and

(e) converting the complex analog baseband signal into a second digital sample sequence representing an imaginary part of the passband signal.

66. The method of claim 63, wherein the step of processing comprises the steps of:

(a) producing a baseband complex representation of the electrical signal;

(b) phase sampling the baseband complex representation of the electrical signal to determine a time series of phase samples of the baseband complex representation; and

(c) determining a first derivative of the time series of the phase samples to determine the indication of the velocity of the object.

67. The method of claim 63, wherein the step of processing comprises the steps of:

(a) sampling the electrical signal, producing a sequence of digital samples;

(b) splitting the sequence of digital samples into a plurality of baseband signal pairs;

(c) separating the plurality of baseband signal pairs into sample packets, according to predefined criteria;

(d) applying an unwrapping algorithm to each sample packet;

(e) rejecting sample packets having a width outside of predefined limits; and

(f) determining the indication of the velocity of the object based upon a sample packet that is not rejected.

68. The method of claim 67, further comprising the step of applying a lowpass filter to each baseband signal pair before the step of separating the baseband signal pairs into sample packets.

69. The method of claim 67, further comprising the step of employing a sequence of upper and lower sideband samples derived from the sequence of complex baseband samples for automated control of the method.

70. The method of claim 63, further comprising the steps of:

(a) applying a Hilbert transform to the electrical signal before the digital samples; and

(b) using the upper sideband and the lower sideband digital samples to;

(i) determine a frequency associated with a light sensitive detector; and

(ii) setting a local oscillator frequency for a baseband demodulator used for determining the indication of the velocity of the object.

71. The method of claim 59, wherein the step of processing comprises the step of utilizing at least one of a digital oscilloscope, a programmed computing device, and an application specific integrated circuit to perform the processing.

72. The method of claim 59, further comprising the steps of:

(a) providing a control system; and

(b) using the control system to perform at least one of the following functions;

(i) regulating an amplification gain applied to the electrical signal in response to a varying level of the electrical signal;

(ii) determining a signal-to-noise ratio of the electrical signal for use in regulating a threshold applied to frequency measurements; and

(iii) regulating a frequency of a baseband converter local oscillator used in the step of processing, as a function of the velocity of the object.

73. The method of claim 59, wherein the step of modulating light from the object using an optical grating comprises the step of utilizing an optical grating having a substantially non uniform pattern.

74. The method of claim 73, wherein the step of utilizing an optical grating comprises the step of utilizing an optical grating having at least one of:

(a) a plurality of alternating opaque bars and transparent gaps, widths of which vary in a linear progression in a direction perpendicular to a longitudinal extent of the bars and the transparent gaps; and

(b) a plurality of alternating opaque bars and transparent gaps, the width of which vary in a non-linear pattern in a direction perpendicular to a longitudinal extent of the bars and the transparent gaps.

75. The method of claim 73, wherein the step of utilizing an optical grating comprises the step of utilizing an optical grating having two substantially identical sections, each with a substantially non-uniform pattern of bar and gap widths, disposed along an axis of motion of the object such that light from the object sequentially traverses said sections.

76. The method of claim 59, wherein the step of modulating light from the object using an optical grating comprises the steps of utilizing a first optical grating to modulate a first light beam from the object, producing first modulated light;

and utilizing a second optical grating to modulate a second light beam from the object, producing second modulated light, wherein the first and second optical gratings have a substantially non uniform pattern.

77. The method of claim 76, wherein the step of modulating light from the object using an optical grating further comprises the step of aligning the first and second optical gratings such that image fields of the first and second optical gratings are disposed in series along an axis of motion of the object.

78. The method of claim 76, wherein the step of producing an electrical signal corresponding to an intensity of the modulated light comprises the steps of producing a first electrical signal corresponding to the first modulated light, and producing a second electrical signal corresponding to the second modulated light, further comprising the steps of converting the first electrical signal into a first sequence of digital samples, and converting the second electrical signal into a second sequence of digital samples.

79. The method of claim 78, further comprising the step of amplifying the first electrical signal and the second electrical signal before converting the first electrical signal and the second electrical signal into the first and second sequences of digital samples.

80. The method of claim 78, further comprising the step of filtering the first electrical signal and the second electrical signal before converting the first electrical signal and second electrical signal into the first sequence and second sequence of digital samples, respectively.

81. The method of claim 76, wherein the step of processing comprises the steps of:

(a) convolving the first electrical signal with the second electrical signal to produce a convolution;

(b) generating a cross-correlogram based on the convolution; and

(c) determining the indication of the velocity from a peak amplitude of the cross-correlogram.

82. The method of claim 76, further comprising the steps of:

(a) providing a control system; and

(b) using the control system to regulate an upper and a lower limit of a time shift in a cross-correlation function in response to a variation in the velocity of the object.

83. A method for determining an indication of a relative velocity associated with an object and one or more other characteristics of an object, comprising the steps of:

(a) directing light from the object along a first collection path;

(b) diverting a portion of the light traveling along the first collection path to a second collection path that is in a different direction than the first collection path;

(c) modulating light traveling along the second collection path as a function of the relative velocity;

(d) producing an electrical signal as a function of an intensity of the modulated light;

(e) processing the electrical signal in the time domain to determine the indication of the relative velocity associated with the object;

(f) providing a time delay integration (TDI) detector disposed to receive the light that is traveling along the first collection path;

(g) using the indication of the relative velocity associated with the object to synchronize the TDI detector with a motion of an image of the object on the TDI detector; and

(h) analyzing an output signal from the TDI detector to determine at least one other characteristic of the object.

84. The method of claim 83, wherein the step of modulating the light comprises the step of providing an optical grating having a substantially uniform pitch;

and wherein the step of processing the electrical signal to determine the indication of the relative velocity comprises the steps of;

(a) producing a baseband complex representation of the electrical signal;

(b) producing a time series of phase samples from the baseband complex representation; and

(c) determining the indication of the relative velocity from a first derivative of the time series of phase samples.

85. The method of claim 83, wherein the step of modulating the light comprises the step of providing an optical grating that modulates the light, further comprising the steps of:

(a) diverting a portion of the light traveling along the second collection path to a third collection path that is in a different direction than the first and second collection paths,

(b) providing a second optical grating having a substantially non uniform pitch, the second optical grating being disposed along the third collection path such that the optical grating and the second optical grating are aligned in series along an axis of relative motion associated with the object, the second optical grating modulating light traveling along the third collection path; and

(c) producing a second electrical signal as a function of an intensity of the modulated light traveling along the third collection path, wherein the step of processing the electrical signal to determine the indication of the relative velocity associated with the object comprises the steps of;

(i) convolving the electrical signal with the second electrical signal to form a convolution;

(ii) producing a cross-correlogram based on the convolution; and

(iii) determining the indication of the relative velocity from a peak amplitude of the cross-correlogram.

86. A method for determining an indication of a velocity and one or more other characteristics associated with a moving object, while there is relative movement between the object and an optical system used to determine the indication of the velocity and the one or more other characteristics, comprising the steps of:

(a) directing light from the object along a first collection path and a second collection path, the first and second collection paths being in a different direction than a direction of the relative movement between the object and the optical system;

(b) modulating light traveling along the first collection path;

(c) producing an electrical signal as a function of an intensity of the modulated light;

(d) processing the electrical signal in the time domain to determine the indication of the relative velocity between the optical system and the object;

(e) dispersing the light that is traveling along the second collection path, producing dispersed light;

(f) providing a time delay integration (TDI) detector disposed to receive the dispersed light;

(g) using the indication of the relative velocity to synchronize the TDI detector with movement of the dispersed light from the object over the TDI detector; and

(h) analyzing an output signal from the TDI detector to determine said one or more other characteristics of the object.

87. The method of claim 86, wherein the step of modulating comprises the step of providing an optical grating having a substantially uniform pitch, and wherein the step of processing the electrical signal to determine the indication of the velocity between the optical system and the object comprises the steps of:

(a) creating a baseband complex representation of the electrical signal;

(b) producing a time series of phase samples from the baseband complex representation of the electrical signal; and

(c) determining a first derivative of the time series of phase samples to determine the indication of the velocity between the optical system and the object.

88. The method of claim 86, further comprising the steps of:

(a) diverting a portion of the light traveling along the first collection path to a third collection path that is in a different direction than the first and second collection paths,

(b) modulating light traveling along the third collection path, producing modulated light;

(c) producing a second electrical signal as a function of an intensity of the modulated light traveling along the third collection path;

(d) convolving the electrical signal and the second electrical signal to produce a cross-correlogram; and

(e) determining the indication of the velocity between the optical system and the object from a peak amplitude of the cross-correlogram.