Multipass cavity for illumination and excitation of moving objects

• US 6,563,583 B2
• Filed: 10/12/2001
• Issued: 05/13/2003
• Est. Priority Date: 10/12/2000
• Status: Expired due to Term

• Current Assignee: Cytek Biosciences Inc
• Original Assignee: Amnis Corporation (DiaSorin S.p.A.)
• Inventors: Basiji, David A., Ortyn, William E.
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M
• Application Number:
  US09/976,465
• Publication Number:
  US 20020057432A1
• Time in Patent Office: 578 Days
• Field of Search: 356/338, 356/138, 356/399, 356/400
• US Class Current: 356/400
• CPC Class Codes: B01J 2219/00274 Sequential or parallel reactions; Apparatus and devices for combinatorial chemistry or for making arrays; Chemical library technology
• CPC Class Codes: C07K 1/047 Simultaneous synthesis of different peptide species; Peptide libraries
• CPC Class Codes: C12Q 1/6816 characterised by the detection means C12Q1/6804 takes precedence
• CPC Class Codes: C12Q 2563/107 fluorescence
• CPC Class Codes: C12Q 2563/179 the label being a nucleic acid
• CPC Class Codes: G01N 15/1433 using image recognition
• CPC Class Codes: G01N 15/1434 Optical arrangements
• CPC Class Codes: G01N 15/1456 without spatial resolution of the texture or inner structure of the particle, e.g. processing of pulse signals
• CPC Class Codes: G01N 15/147 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2015/0294 Particle shape
• CPC Class Codes: G01N 2015/1443 Auxiliary imaging
• CPC Class Codes: G01N 2015/1472 with colour
• CPC Class Codes: G01N 2015/1479 Using diffuse illumination or excitation
• CPC Class Codes: G01N 2015/1488 Methods for deciding
• CPC Class Codes: G01N 2021/052 Tubular type; cavity type; multireflective
• CPC Class Codes: G01N 2021/058 Flat flow cell
• CPC Class Codes: G01N 21/031 Multipass arrangements
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G02B 21/00 Microscopes
• CPC Class Codes: G02B 27/0012 Optical design, e.g. procedures, algorithms, optimisation routines
• CPC Class Codes: G02B 27/144 : using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence
• CPC Class Codes: G02B 7/28 : Systems for automatic generation of focusing signals

Abstract

A multipass cavity system employs a beam of light that is reflected back and forth between reflective surfaces a plurality of times, illuminating a different portion of the field of view with each pass until the light exits the reflection cavity. The “recycling” of the light beam substantially improves the SNR of the detection system. The present invention is a beam alignment system for use in such a multipass cavity, correcting misalignment in four degrees of freedom; the horizontal and vertical axes, and angle in each of the vertical and horizontal axes. Angular or positional errors lateral to the direction of the beam can dramatically affect performance. The present invention enables the measurement and adjustment of each degree of freedom independently, in order to make beam steering corrections and maintain optical alignment. This is accomplished in an automated, closed-loop feedback control system.

Claims

1. A beam detection system for use with an illumination system, to enable detection of beam misalignment in four degrees of freedom, comprising:

(a) a beam splitter disposed in an illumination system light path, said illumination system light path originating in said illumination system, said beam splitter separating an illumination system light beam traveling along the illumination system light path into a first beam that is directed along a first light path and a second beam that is directed along a second light path;

(b) a first position sensitive detector disposed in said first light path to receive said first beam, said first position sensitive detector determining an angular error associated with said illumination system light beam; and

(c) a second position sensitive detector disposed in said second light path to receive said second beam;

said second position sensitive detector determining at positional error associated with said illumination system light beam.

2. The beam detection system of claim 1, further comprising a first optical element disposed such that a front focal plane of said first optical element is disposed facing an aperture of said illumination system, and a rear focal plane of said first optical element is disposed facing said beam splitter.

3. The beam detection system of claim 1, further comprising a second optical element disposed such that a front focal plane of said second optical element is disposed facing an aperture of said illumination system, and a rear focal plane of said second optical element is disposed facing said second position sensitive detector.

4. The beam detection system of claim 1, further comprising a first and second optical element, disposed such that light reaching said first position sensitive detector from said illumination system light path passes through said first optical element but not said second optical element, and light reaching said second position sensitive detector from said illumination system light path passes through both said first optical element and said second optical element.

5. The beam detection system of claim 4, wherein said beam splitter is disposed between said first and second optical elements.

6. The beam detection system of claim 1, wherein said beam splitter directs said first beam by reflection and directs said second beam by transmission.

7. The beam detection system of claim 6, wherein a transmission/reflection ratio of said beam splitter is substantially 50/50.

8. A beam detection system for use with an illumination system, to enable detection of beam misalignment in four degrees of freedom, comprising:

(a) a first optical element disposed in an illumination system light path, said illumination system light path originating in said illumination system, such that a front focal plane of said first optical element is disposed facing an aperture of said illumination system;

(b) a beam splitter disposed in said illumination system light path, said beam splitter receiving light from said illumination system that passes through said first optical element, said beam splitter separating an illumination system light beam traveling along the illumination system light path into a first beam that is directed along a first light path and a second beam that is directed along a second light path;

(c) a first position sensitive detector disposed in said first light path to receive said first beam, said first position sensitive detector determining an angular error associated with said illumination system light beam;

(d) a second optical element disposed in said second light path, such that a front focal plane of said second optical element is disposed facing said aperture; and

(e) a second position sensitive detector disposed in said second light path to receive said second beam, such that a rear focal plane of said second optical element is disposed facing said second position detector, said second position sensitive detector determining a positional error associated with said illumination system light beam.

9. The beam detection system of claim 8, wherein said beam splitter is disposed between said first and second optical elements.

10. The beam detection system of claim 8, wherein said beam splitter directs said first beam by reflection and directs said second beam by transmission.

11. The beam detection system of claim 10, wherein a transmission/reflection ratio of said beam splitter is substantially 50/50.

12. The beam detection system of claim 8, wherein said illumination system light path and said second light path share a common axis.

13. The beam detection system of claim 8, wherein a focal length of said first optical element is smaller than a focal length of said second optical element.

14. A beam detection and alignment system for use with an illumination system, to enable detection and correction of beam misalignment at an aperture of said illumination system, comprising:

(a) a first independently adjustable reflective element disposed in an illumination system light path, said first independently adjustable reflective element selectively redirecting said illumination system light path, thereby adjusting a beam angle at said aperture;

(b) a second independently adjustable reflective element disposed in said illumination system light path, said second independently adjustable reflective element selectively redirecting said illumination system light path, thereby adjusting a beam position at said aperture;

(c) a first beam splitter disposed in said illumination system light path, said beam splitter separating an illumination system light beam traveling along the illumination system light path into a first beam that is directed along a first light path and a second beam that is directed along a second light path, said second light path being directed at said aperture;

(d) a second beam splitter disposed in said first light path, said second beam splitter separating an illumination system light beam traveling along said first light path into a first detection beam that is directed along a first detection light path and a second detection beam that is directed along a second detection light path;

(e) a first position sensitive detector disposed in said first detection light path to receive said first detection beam, said first position sensitive detector determining an angular error associated with said illumination system light beam; and

(f) a second position sensitive detector disposed in said second detection light path to receive said second detection beam;

said second position sensitive detector determining at positional error associated with said illumination system light beam.

15. The beam detection and alignment system of claim 14, further comprising:

(a) a first alignment optical element disposed in said illumination system light path, between said first independently adjustable reflective element and said second independently adjustable reflective element, such that said aperture is imaged by said first optical element onto said first independently adjustable reflective element; and

(b) a second alignment optical element disposed in said illumination system light path, between said second independently adjustable reflective element and said aperture, such that said aperture is substantially collimated by said second optical element at said second independently adjustable reflective element.

16. The beam detection and alignment system of claim 15, further comprising:

(a) a first detection optical element disposed in said first light path, such that a focal plane of said first detection optical element is disposed facing said aperture; and

(b) a second detection optical element disposed in said second detection light path, such that a focal plane of said second optical element is disposed facing said aperture, and said second beam splitter is disposed between said first and second detection optical elements.

17. The beam detection and alignment system of claim 16, wherein a focal length of said first detection optical element is smaller than a focal length of said second detection optical element.

18. The beam detection and alignment system of claim 14, wherein each beam splitter directs a first beam by reflection and a second beam by transmission.

19. The beam detection and alignment system of claim 18, wherein the transmission/reflection ratio of said first beam splitter is selected to sample a portion of the energy in the illumination system light path so as to provide a sufficient signal-to-noise ratio for accurate detection of the light traveling along the illumination system light path, and the transmission/reflection ratio of said second beam splitter is selected to provide substantially the same signal level at each position sensitive detector.

20. The beam detection and alignment system of claim 14, wherein said first light path and said second detection light path share a common axis.

21. The beam detection and alignment system of claim 14, wherein said first beam splitter is oriented to split an illumination system light beam traveling along the illumination system light path into said first beam and said second beam after the illumination system light beam passes through said aperture a first time, is internally reflected, and passes through said aperture a second time.

22. The beam detection and alignment system of claim 14, further comprising:

(a) a beam alignment processor electrically coupled to each of said first and second position sensitive detectors, said beam alignment processor determining angular and positional correction factors based on signals received from said first and second position sensitive detectors; and

(b) a prime mover drivingly coupled to each independently adjustable reflective element, such that each independently adjustable reflective element is repositionable independently of the other, said prime mover being electrically coupled to, and controlled by, said beam alignment processor.

23. The beam detection and alignment system of claim 14, wherein each independently adjustable reflective element comprises a mechanical actuator operable to adjust a position of the independently adjustable reflective element, further comprising a beam alignment processor electrically coupled to each of said first and second position sensitive detectors, said beam alignment processor determining angular and positional correction factors based on signals received from said first and second position sensitive detectors and being electrically coupled to each mechanical actuator, thereby enabling said beam alignment processor to control and adjust the position of each independently adjustable reflective element, based on signals generated by said first and second position sensitive detectors.

24. The beam detection and alignment system of claim 23, wherein said mechanical actuators are operable to adjust a tip and a tilt of each independently adjustable reflective element.

25. A beam detection and alignment system for use with an illumination system, to enable detection and correction of beam misalignment at an aperture of said detection illumination system, comprising:

(a) a first independently adjustable reflective element disposed in an illumination system light path, said first independently adjustable reflective element selectively modifying said illumination system light path by adjusting a beam angle at said aperture;

(b) a second independently adjustable reflective element disposed in said illumination system light path, said second independently adjustable reflective element selectively modifying said illumination system light path by adjusting a beam position at said aperture;

(c) a first alignment optical element disposed in said illumination system light path, between said first independently adjustable reflective element and said second independently adjustable reflective element, such that said aperture is imaged by said first optical element onto said first independently adjustable reflective element;

(d) a second alignment optical element disposed in said illumination system light path, between said second independently adjustable reflective element and said aperture, such that said aperture is substantially collimated by said second optical element at said second independently adjustable reflective element;

(e) a first beam splitter disposed in said illumination system light path, said first beam splitter separating said illumination system light beam into a first beam that is directed along a first light path and a second beam that is directed along a second light path, said second light path being directed at said aperture;

(f) a second beam splitter disposed in said first light path, said second beam splitter separating said illumination system light beam into a first detection beam that is directed along a first detection light path and a second detection beam that is directed along a second detection light path;

(g) a first detection optical element disposed in said first light path;

(h) a second detection optical element disposed in said second detection light path, such that said second beam splitter is disposed between said first and second detection optical elements;

(i) a first position sensitive detector disposed in said first detection light path to receive said first detection beam, said first position sensitive detector determining an angular error associated with said illumination system light beam; and

(j) a second position sensitive detector disposed in said second detection light path to receive said second detection beam, said second position sensitive detector determining a positional error associated with said illumination system light beam.

26. The beam detection and alignment system of claim 25, wherein each independently adjustable reflective element comprises a mechanical actuator operable to adjust a position of the independently adjustable reflective element, further comprising a beam alignment processor electrically coupled to each of said first and second position sensitive detectors, said beam alignment processor determining angular and positional correction factors based on signals received from said first and second position sensitive detectors and being electrically coupled to each mechanical actuator to enable said beam alignment processor to control and adjust the position of each independently adjustable reflective element based on signals generated by said first and second position sensitive detectors.

27. A beam detection and alignment system for use with an illumination system, to enable detection and correction of beam misalignment at an aperture of said illumination system, comprising:

(a) a first independently adjustable reflective element disposed in an illumination system light path, comprising a mechanical actuator operable to adjust a position of said first independently adjustable reflective element, thereby selectively modifying said illumination system light path, to adjust a beam angle at said aperture;

(b) a second independently adjustable reflective element disposed in said illumination system light path, comprising a mechanical actuator operable to adjust a position of said second independently adjustable reflective element to selectively modify said illumination system light path, to adjust a beam position at said aperture;

(c) a first beam splitter disposed in said an illumination system light path, said beam splitter separating an illumination system light beam traveling along the illumination system light path into a first beam that is directed along a first light path and a second beam that is directed along a second light path, said second light path being directed at said aperture;

(d) a second beam splitter disposed in said first light path, said second beam splitter separating an illumination system light beam traveling along said first light path into a first detection beam that is directed along a first detection light path and a second detection beam that is directed along a second detection light path;

(e) a first position sensitive detector disposed in said first detection light path to receive said first detection beam, said first position sensitive detector producing a signal indicative of an angular error associated with said illumination system light beam;

(f) a second position sensitive detector disposed in said second detection light path to receive said second detection beam;

said second position sensitive detector producing a signal indicative of a positional error associated with said illumination system light beam; and

(g) a beam alignment processor electrically coupled to each of said first and second position sensitive detectors, and to each mechanical actuator, said beam alignment processor determining angular and positional correction factors based on the signals received from said first and second position sensitive detectors, and adjusting a position of each independently adjustable reflective element by activating said mechanical actuators to apply said angular and positional correction factors to reduce an error in said beam angle and said beam position relative to said aperture.

28. A method for detecting a positional beam misalignment and an angular beam misalignment relative to an aperture in an illumination system, comprising the steps of:

(a) directing light from said aperture along a first light path;

(b) diverting a portion of light traveling along said first light path to a second light path;

(c) determining a positional error of the light traveling along the first light path relative to a central axis of said aperture; and

(d) determining an angular error of the light traveling along the second light path relative to a central axis of said aperture.

29. The method of claim 28, further comprising the steps of:

(a) focussing light traveling along the first light path to determine the position error from the light that is thus focussed; and

(b) focusing light traveling along the second light path to determine the angular error from the light that is thus focussed.

30. The method of claim 28, wherein the step of diverting a portion of light traveling along said first light path to a second light path comprises the step of splitting the light traveling along the first light path.

31. The method of claim 28, further comprising the steps of collecting light traveling along the first and second light paths;

and focussing the light collected onto a quad cell detector for each of the first and second light paths.

32. A method for detecting a positional light path misalignment and an angular light path misalignment relative to an aperture in an illumination system, and correcting the misalignment, comprising the steps of:

(a) directing light from the aperture along a first light path;

(b) diverting a portion of light traveling along the first light path along a second light path;

(c) determining a positional error of the light traveling along the first light path relative to a central axis of the aperture;

(d) determining an angular error of the light traveling along the second light path relative to a central axis of said aperture;

(e) if the angular misalignment is greater than a first predefined threshold, redirecting the light traveling from a source toward the aperture to correct the angular misalignment; and

(f) if the positional misalignment is greater than a second predefined threshold, further redirecting the light that was redirected to correct the positional misalignment.

33. The method of claim 32, further comprising the steps of:

(a) focussing light traveling along the first light path to determine the positional error; and

(b) focussing light traveling along the second light path to determine the angular error.

34. The method of claim 32, wherein the step of diverting comprises the step of diverting substantially one half of the light traveling along said first light path along said second light path.

35. The method of claim 32, wherein each of the steps of detecting light traveling along the first and second light paths comprises the step of detecting the light with a quad cell detector.

36. The method of claim 32, further comprising the step of automating the steps of detecting the angular and positional misalignments.

37. The method of claim 32, further comprising the steps of automating the steps of redirecting the light to correct for the angular and positional misalignments.

38. A method for detecting a positional misalignment and an angular misalignment of light traveling along a path relative to an aperture in an illumination system, and redirecting the light to correct the misalignment, comprising the steps of:

(a) determining the magnitude of the angular misalignment relative to the aperture;

(b) determining if the magnitude of the angular misalignment exceeds a predefined angular error limit;

(c) if the magnitude of the angular misalignment exceeds the predefined angular error limit, determining and executing an adjustment necessary to correct the angular misalignment;

(d) determining the magnitude of the positional misalignment relative to the aperture;

(e) determining if the magnitude of the positional misalignment exceeds a predefined positional error limit; and

(f) if the magnitude of the positional misalignment exceeds the predefined positional error limit, then determining and executing an adjustment necessary to correct the positional misalignment.

39. The method of claim 38, further comprising the steps of automating steps (a)-(f).