Control systems and methods for diffuse illumination

• US 6,441,367 B1
• Filed: 06/02/1999
• Issued: 08/27/2002
• Est. Priority Date: 06/02/1999
• Status: Expired due to Term

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Gladnick, Paul G.
• Primary Examiner(s): Evans, F. L.
• Assistant Examiner(s): SMITH, ZANDRA V
• Application Number:
  US09/323,916
• Time in Patent Office: 1,182 Days
• Field of Search: 356/616, 356/618, 356/614, 356/625, 250/237.G, 359/599
• US Class Current: 250/237.00G
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 5/02 Diffusing elements; Afocal elements

Abstract

A light pattern generator generates a pattern of continuous wave, modulated and/or pulsed light onto a face of a collimator. The light pattern is collimated by an optical element and directed to a focusing element which focuses the collimated light pattern onto a sample. A controller controls the pattern generator and the light source to determine a shape of the illuminated pattern on the face of the collimator. The controller also controls the frequency, positional phase angle and pulse width of the light source. Additionally, the controller may control the color of the light so that the color varies over time.

Claims

1. An apparatus for controllably illuminating a sample diffusely, the apparatus comprising:

a light pattern generation system that controllably generates a pattern of light, the pattern of light having at least one illumination area, each illumination area having at least one of an angle of incidence, a positional phase angle and an arc length;

a collimator that receives and collimates the pattern of light;

a focusing element that focuses the collimated pattern of light onto a sample; and

a controller that controls the light pattern generation system to generate the pattern of light.

2. The apparatus of claim 1, wherein the light pattern generation system comprises a light pattern generator and a light source outputting light to the light pattern generator.

3. The apparatus of claim 2, wherein the light pattern generator is a beam deflector that deflects light output by the light source.

4. The apparatus of claim 3, wherein:

the beam deflector comprises a rotating mirror tiltably mounted on a shaft of a motor; and

the controller controls an angle of incidence of each illumination area by outputting a drive signal profile to the motor to drive the motor at a rotational velocity corresponding to the angle of incidence of that illumination area.

5. The apparatus of claim 3, wherein:

the beam deflector comprises a pair of galvanometers; and

the controller controls an angle of incidence of each illumination area by outputting a pair of drive signals to the pair of galvanometers to drive the pair of galvanometers at tilt angles corresponding to the angle of incidence of that illumination area.

6. The apparatus of claim 3, wherein:

the light source includes at least one controllable light emitting structure;

the controller outputs a modulated drive signal to each controllable light emitting structure to apply a modulation to an emitted light beam; and

the positional phase angle and arc length of each illumination area corresponds to the modulation of the light beam.

7. The apparatus of claim 6, wherein:

the light source includes at least one solid-state light emitting structure; and

the controller controls a positional phase angle and an arc length of each illumination area by outputting a drive signal to each of at least one solid-state light emitting structure.

8. The apparatus of claim 6, wherein:

the beam deflector comprises a pair of galvanometers scanning at a pair of frequencies;

the light source includes at least one solid-state light emitting structure;

the controller outputs a modulated drive signal to each solid-state light emitting structure to modulate the emitted light beam based on the scanning frequencies and relative phase; and

the positional phase angle and arc length of each illumination area is based on the modulated light beam.

9. The apparatus of claim 3, wherein:

the beam deflector comprises a rotating mirror tiltably mounted on a shaft of a motor rotating at a rotational velocity;

the light source includes at least one solid-state light emitting structure; and

the controller outputs a modulated drive signal to each solid-state light emitting structure, each modulated drive signal driving a corresponding solid-state light emitting structure to output a light beam and to modulate the light beam based on the rotational positions corresponding to the positional phase angle and arc length of each illumination area.

10. The apparatus of claim 2, wherein:

the light source includes at least one controllable light emitting structure;

the controller outputs a modulated drive signal to each controllable light emitting structure to output a modulated light beam; and

the positional phase angle and arc length of each illumination area is based on the modulated light beam.

11. The apparatus of claim 2, wherein:

the light source includes at least one solid-state light emitting structure; and

the controller controls a positional phase angle and an arc length of each illumination area by outputting a drive signal to each at least one solid-state light emitting structure to drive the at least one solid-state light emitting structure corresponding to the positional phase angle and arc length of that illumination area.

12. The apparatus of claim 2, wherein:

the light source outputs light;

the light pattern generator is a liquid crystal device having a plurality of selectable areas; and

the controller selectively activates the plurality of selectable areas to form the pattern of light.

13. The apparatus of claim 12, wherein the controller selectively activates the plurality of selectable areas based on the angle of incidence, positional phase angle and arc length of each illuminated area of the pattern of light.

14. The apparatus of claim 12, wherein each selectable area, when activated, transmits the light output by the light source.

15. The apparatus of claim 12, wherein each selectable area, when activated, does not transmit the light output by the light source.

16. The apparatus of claim 12, wherein each selectable area, when activated, reflects the light output by the light source.

17. The apparatus of claim 12, wherein each selectable area, when activated, does not reflect the light output by the light source.

18. The apparatus of claim 2, wherein the light source includes at least one solid-state light emitting structure.

19. The apparatus of claim 18, wherein each at least one solid-state light emitting structure is one of an LED and a laser diode.

20. The apparatus of claim 18, wherein:

the light source includes a plurality of solid-state light emitting structures; and

each solid-state light emitting structure emits light at a different wavelength.

21. The apparatus of claim 20, wherein the controller drives the plurality of solid-state light emitting structures to vary the wavelengths of the light beams based on an operational state of the light pattern generator.

22. The apparatus of claim 21, wherein the operational state of the light pattern generator is one of:

a rotational position when the light pattern generator includes a rotating mirror;

a drive signal phase angle when the light pattern generator includes a pair of scanning galvanometers; and

a configuration of selected areas when the light pattern generator is a liquid crystal device having a plurality of selectable areas.

23. The apparatus of claim 1, wherein the controller drives a solid-state light emitting structure to vary the wavelength of the light beam based on an operational state of a light pattern generator.

24. The apparatus of claim 23, wherein the operational state of the light pattern generator is one of:

a rotational position when the light pattern generator includes a rotating mirror;

a drive signal phase angle when the light pattern generator includes a pair of scanning galvanometers; and

a configuration of selected areas when the light pattern generator is a liquid crystal device having a plurality of selectable areas.

25. The apparatus of claim 1, wherein the pattern is one of elliptical and circular.

26. The apparatus of claim 1, wherein the sample reflects the light beam, the apparatus further comprising a light sensing device that senses the reflected light beam from the sample and outputs an image of the sample.

27. The apparatus of claim 26, wherein the light sensing element comprises one of a monochrome CCD array and a color CCD array.

28. The apparatus of claim 1, wherein the apparatus is operably positioned relative to an imaging system such that the collimated pattern of light is transmitted along a zone generally surrounding an optical axis of the imaging system.

29. A method for controllably illuminating a sample diffusely, the method comprising:

controllably generating a pattern of light, the pattern of light having at least one illumination area, each illumination area having at least one of an angle of incidence, a positional phase angle and an arc length;

collimating the pattern of light; and

focusing the collimated pattern of light onto the sample.

30. The method of claim 29, wherein controllably generating a pattern of light comprises:

outputting light onto a beam deflector;

controlling an operational state of the beam deflector; and

modulating the light output by the light source based on the operational state of the beam deflector.

31. The method of claim 30, wherein:

the beam deflector comprises a rotating mirror tiltably mounted on a shaft of a motor; and

controlling an operational state of the beam deflector comprises controlling a rotational velocity of the motor.

32. The method of claim 31, wherein modulating the light beam output by the light source based on the operational state of the beam deflector comprises:

determining a rotational position of the mirror;

determining desired rotational positions of the mirror for each illuminated area based on the positional phase angle and arc length for that illuminated area; and

modulating the light beam based on the desired and determined rotational positions of the mirror.

33. The method of claim 31, wherein:

the beam deflector comprises a pair of galvanometers;

controlling an operational state of the beam deflector comprises controlling a tilt angle of each of the pair of galvanometers.

34. The method of claim 33, wherein modulating the light beam output by the light source based on the operational state of the beam deflector comprises:

determining desired drive signal phase positions for the drive signals for the pair of galvanometers for each illuminated area based on the positional phase angle and arc length for that illuminated area;

modulating the light beam based on the drive signal phase positions for the drive signals for the pair of galvanometers.

35. The method of claim 30, wherein outputting light comprises driving at least one solid-state light emitting structure.

36. The method of claim 35, wherein each at least one solid-state light emitting structure is one of an LED and a laser diode.

37. The method of claim 35, wherein:

driving at least one solid-state light emitting structure comprises driving a plurality of solid-state light emitting structures; and

each solid-state light emitting structure emits light at a different wavelength.

38. The method of claim 37, wherein driving the plurality of solid-state light emitting structures comprises selectively driving various ones of the plurality of solid-state light emitting structures to vary the wavelengths of the light beam based on the operational state of the beam deflector.

39. The method of claim 29, wherein controllably generating a pattern of light comprises:

outputting light onto a liquid crystal device having a plurality of selectable areas;

selectively activating the plurality of selectable areas to form the pattern of light.

40. The method of claim 39, wherein selectively activating the plurality of selectable areas to form the pattern of light comprises selectively activating the plurality of selectable areas based on the angle of incidence, positional phase angle and arc length of each illuminated area of the pattern of light.

41. The method of claim 29, further comprising:

sensing light reflected from the sample; and

outputting an image of the sample based on the sensed light.

42. The method of claim 41, wherein sensing the light reflected from the sample comprises sensing the reflected light using one of a monochrome CCD array and a color CCD array.

43. The method of claim 29, wherein collimating the pattern of light further comprises:

transmitting the collimated pattern of light along a zone generally surrounding an optical axis of an imaging system usable to receive an image of the sample.