Optical beam steering and sampling apparatus and method

Abstract

In a light (optical) beam steering/sampling system, a matrix inversion control technique is used to decouple the operation of the actuators which drive the steering mirrors. The control technique uses two virtual variables, each having an associated independent feedback loop operating in a non-cross-coupled manner, each variable being associated with one of the two steering mirrors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in a block diagram an example of the present optical system.

FIG. 2 shows in a block diagram the feedback control method for the two feedback loops.

FIG. 3 shows the optical axis of the FIG. 1 system.

Claims

1. Apparatus comprising: a first steering reflector on which a beam of light is incident;a second steering reflector on which light reflected from the first steering reflector is incident;a first beam splitter on which light reflected from the second steering reflector is incident;a second beam splitter on which light reflected from the first beam splitter is incident;a first detector on which light reflected from the first beam splitter is incident; anda second detector on which light transmitted by the second beam splitter is incident;wherein a first value which is a function of an output signal of both detectors is indicative of a state of the first steering reflector, and a second value which is a function of an output signal of both detectors is indicative of a state of the second steering reflector.

2. The apparatus of claim 1, further comprising a controller coupled between the detectors and the steering reflectors, whereby the controller changes a state of the first and second steering reflectors responsive to respectively the first and second values.

3. The apparatus of claim 1, each steering reflector including a reflector coupled to an actuator.

4. The apparatus of claim 3, each steering reflector having a second actuator coupled to the reflector to tilt the reflector in a direction substantly orthogonal to a direction in which the first actuator tilts that reflector.

5. The apparatus of claim 1, wherein light transmitted by the first beam splitter is directed out of the apparatus.

6. The apparatus of claim 1, further comprising a third reflector positioned to reflect the light transmitted by the second beam splitter to the second detector.

7. The apparatus of claim 2, the controller including two control loops, one control loop being associated with each of the first and second values.

8. The apparatus of claim 1, wherein each of the first and second values is a function of a displacement and an angle of the light beam incident on the apparatus.

9. The apparatus of claim 2, wherein the controller includes means for calibrating the apparatus.

10. The method of claim 1, further comparing a first lens located to focus light onto the first detector and a second lens located to focus light onto the second detector.

11. Method for operating an optical apparatus having two steering reflectors, comparing the acts of: splitting light reflected serially from the two steering reflectors;splitting the split light, into two portions;detecting a first portion of the twice split light;detecting a second portion of the twice split light;obtaining a first value which is a function of an output signal from both acts of detecting, the first value being indicative of a state of the first steering reflector; andobtaining a second value which is a function of an output signal from both acts of detecting, the second value being indicative of a state of the second steering reflector.

12. The method of claim 11, further comprising the act of: controlling a state of the first and second steering reflectors responsive to respectively the first and second values.

13. The method of claim 11, further comprising the act of changing the state of each steering reflector by an actuator.

14. The method of claim 13, further comprising the act of providing a second actuator associated with each steering reflector to tilt the steering reflector in a direction orthogonal to a direction in which the first actuator tilts that reflector.

15. The method of claim 11, further comprising the act of directing externally a portion of the light which is split from the first act of splitting.

16. The method of claim 11, further comprising the act of reflecting the second portion of the twice split light prior to the act of detecting same.

17. The method of claim 12, the controlling including: providing two control loops, one control loop being associated with each of the first and second values.

18. The method of claim 11, wherein each of the first and second values is a function of a displacement and an angle of light incident on a first of the steering reflectors.

19. The method of claim 11, further comprising the act of calibrating the optical apparatus.

20. The method of claim 11, further comprising the act of focusing the light prior to detecting same.