Systems and methods for precise measurement of transparent objects

1. A measurement system comprising:

a light source configured to produce a collimated optical beam;

a modulator configured to modulate the collimated optical beam to produce a collimated modulated optical beam;

optics configured to direct the collimated modulated optical beam to illuminate a transparent test object;

a first beam-blocking component including a first aperture positioned between the optics and the test object, the beam-blocking component being configured to allow a portion of the collimated modulated optical beam to travel through the first aperture to illuminate a test region of the test object and to block a remainder of the collimated modulated optical beam from reaching the test object;

a power detector configured to receive an intensity-modulated optical beam output from the test object and to measure variations in intensity of the intensity-modulated optical beam corresponding to an intensity modulation of the intensity-modulated optical beam, the intensity-modulated optical beam being derived from interaction of the collimated modulated optical beam with the transparent test object; and

a processor coupled to the power detector and configured to produce a representation of variation of thickness of the test object based on the variations in intensity of the intensity-modulated optical beam measured by the power detector.

2. The measurement system of claim 1 wherein the modulator is a phase modulator configured to phase-modulate the collimated optical beam and the resulting collimated modulated optical beam is a collimated phase-modulated optical beam.

3. The measurement system of claim 1 wherein the modulator is a frequency modulator configured to frequency-modulate the collimated optical beam and the resulting collimated modulated optical beam is a collimated frequency-modulated optical beam.

4. The measurement system of claim 1 wherein the power detector includes at least one photodetector.

5. The measurement system of claim 1 wherein the first aperture is dynamically repositionable within the first beam-blocking component.

6. The measurement system of claim 1 further comprising:

a second beam-blocking component including a second aperture and positioned on an opposite side of the test object relative to the first beam-blocking component, the second beam-blocking component being positioned between the test object and the power detector and arranged such that the second aperture is aligned with the first aperture and to allow the intensity-modulated optical beam to pass through the second aperture to reach the power detector.

7. The measurement system of claim 1 further comprising:

a reflector positioned on an opposite side of the test object relative to the first beam-blocking component and configured to reflect the collimated modulated optical beam back through the test object, the intensity-modulated optical beam output from the test object travelling through the first aperture; and

a beam splitter positioned between the optics and the first beam-blocking component and configured to direct the collimated phase-modulated optical beam to the first beam-blocking component and to direct the intensity-modulated optical beam to the power detector.

8. The measurement system of claim 7 wherein the reflector is in contact with the test object.

9. The measurement system of claim 1 wherein the light source includes a laser.

10. The measurement system of claim 1 wherein the optics includes a beam expander.

11. The measurement system of claim 1 wherein the processor is further configured to produce a representation of at least one of a surface roughness of the test object, a parallelism of surfaces of the test object, and a flatness of the test object based on the variations in the intensity of the intensity-modulated optical beam measured by the power detector.

12. A method of characterizing properties of a transparent test object, the method comprising:

producing a collimated modulated optical beam;

illuminating the test object with the collimated modulated optical beam, including allowing a portion of the collimated modulated optical beam to pass through an aperture of a beam-blocking component to illuminate a test region of the test object and blocking a remainder of the collimated modulated optical beam from reaching the test object with the beam-blocking component;

translating the test object through the collimated modulated optical beam in a direction perpendicular to a direction of propagation of the collimated modulated optical beam to produce an intensity-modulated optical beam derived from interaction of the collimated modulated optical beam with the test object, wherein translating the test object includes repositioning the aperture of the beam-blocking component to alter a location of the test region within the test object;

measuring variations in intensity of the intensity-modulated optical beam, the variations in intensity corresponding to an intensity modulation of the intensity-modulated optical beam; and

providing a representation of a thickness of the test object based on the measured variations in the intensity of the intensity-modulated optical beam.

13. The method of claim 12 wherein producing the collimated modulated optical beam includes:

generating a collimated optical beam with a laser; and

modulating the collimated optical beam with a phase modulator to produce a collimated phase-modulated optical beam.

14. The method of claim 12 wherein producing the collimated modulated optical beam includes:

generating a collimated optical beam with a laser; and

modulating the collimated optical beam with a frequency modulator to produce a collimated frequency-modulated optical beam.

15. The method of claim 12 wherein providing the representation of the thickness of the test object includes providing a thickness profile for the test object.

16. The method of claim 12 further comprising providing a representation of at least one of a surface roughness of the test object, a parallelism of surfaces of the test object, and a flatness of the test object based on the variations in the intensity of the intensity-modulated optical beam measured by the power detector.