Signal sample trigger apparatus, data acquisition system and method of sampling an analogue signal

1. A signal sample trigger apparatus comprising:

an input;

a processing resource coupled to the input; and

an output coupled to the processing resource; wherein

the processing resource is arranged to generate, when in use, a trigger signal in response to a location increment signal, the location increment signal having a rising edge and a falling edge;

the location increment signal corresponds to a repeating predetermined travel distance and is received via the input; and

the trigger signal is provided via the output for triggering execution of a sample of a measurement signal, the trigger signal comprising a repeating series of pulses associated with the location increment signal including a first pulse and a second pulse: wherein

the first pulse and the second pulse are generated in response to the rising edge of the location increment signal and the falling edge of the location increment signal, respectively.

2. The apparatus according to claim 1 , wherein the input comprises a first channel input and a second channel input.

3. The apparatus according to claim 2 , wherein the location increment signal comprises a first location increment signal and a second location increment signal, the first and second location increment signals being received via the first channel input and the second channel input, respectively.

4. The apparatus according to claim 3 , wherein the first location increment signal is out of phase with the second location increment signal.

5. The apparatus according to claim 3 , wherein the first location increment signal is substantially 90° out of phase with the second location increment signal.

6. The apparatus according to claim 1 , wherein the trigger signal constitutes a clock signal.

7. The apparatus according to claim 1 , wherein the processing resource comprises an interrupt signal generator, the interrupt signal generator being responsive to a change in the location increment signal so as to cause the processing resource to generate the trigger signal.

8. The apparatus according to claim 7 , wherein the interrupt signal generator has an interrupt time associated with a frequency of the trigger signal, the interrupt time being arranged to elapse between expected receipts of the location increment signal.

9. The apparatus according to claim 1 , wherein the processing resource is arranged to generate a state transition response signal.

10. The apparatus according to claim 1 , wherein the processing resource is capable of detecting a direction associated with the location increment signal and ignoring location increment signals associated with a direction that is opposite to an expected direction of travel.

11. A data acquisition system comprising:

a signal sample trigger apparatus according to claim 1 , the input of the signal sample trigger apparatus being coupled to a data encoder; and

a data sampling module coupled to the output of the signal sample trigger apparatus, the data sample module being arranged to sample the measurement signal in response to a characteristic of the trigger signal.

12. The system according to claim 11 , wherein the data encoder is arranged to generate, when in use, the location increment signal.

13. The system according to claim 11 , further comprising:

a scanning system, the data encoder generating the location increment signal in response to translation of an element of the scanning system.

14. The system according to claim 13 , wherein the element of the scanning system is a translatable stage.

15. The system according to claim 13 , further comprising:

a motion controller coupled to the scanning system.

16. An optical measurement apparatus comprising the data acquisition system according to claim 1 .

17. The apparatus according to claim 16 , further comprising a confocal optical system.

18. The apparatus according to claim 16 arranged to measure, when in use, a physiological characteristic of a part of a body.

19. The apparatus according to claim 18 , wherein the part of the body is an eye.

20. A method of sampling a measurement signal, the method comprising:

receiving a location increment signal corresponding to a repeating predetermined travel distance, the location increment signal having a rising edge and a falling edge;

generating a trigger signal in response to the location increment signal, the trigger signal comprising a repeating series of pulses associated with the location increment signal including a first pulse and a second pulse; wherein

the first pulse and the second pulse are generated in response to the rising edge of the location increment signal and the falling edge of the location increment signal, respectively; and

sampling the measurement signal in response to the trigger signal.