Method and apparatus for robust velocity prediction
One embodiment relates to a method of velocity prediction using a sensor array. Differential signals are obtained from the sensor array at multiple frame rates. A first velocity prediction is determined from the differential signals at a first frame rate, and a second velocity prediction is determined from the differential signals at a second frame rate. Another embodiment relates to an optical navigation apparatus which includes a sensor array, differential circuitry, driver circuitry, and a signal processing device. The driver circuitry is configured to drive the sensor array and differential circuitry so as to operate at multiple frame rates in an interleaved manner. The signal processing device is configured to compute a first velocity prediction from the differential signals at a first frame rate and to compute a second velocity prediction from the differential signals at a second frame rate. Other embodiments and features are also disclosed.
1. A method of velocity prediction using a sensor array, the method comprising:
obtaining differential signals from the sensor array at multiple frame rates;
determining a first velocity prediction from the differential signals at a first frame rate; and
determining a second velocity prediction from the differential signals at a second frame rate; and
processing the first and second velocity predictions so as to derive a correction for extra or missing phase rotations, wherein a velocity prediction from the faster of the first and second frame rates is utilized to correct a velocity prediction from the slower of the first and second frame rates.
2. The method of claim 1 , wherein the sensor array comprises an array of detector cells configured as a comb array.
3. The method of claim 1 , wherein the first frame rate is 1/Δt 0 , the second frame rate is 1/Δt 1 , and the sensor array obtains the differential signals at the two frame rates by interleaving frames of width Δt 0 and frames of width Δt 1 .
4. The method of claim 3 , wherein the ratio of the first frame rate to the second frame rate is a non-integer number.
5. A method of velocity prediction using a sensor array, the method comprising:
obtaining differential signals from the sensor array at multiple frame rates;
determining a first velocity prediction from the differential signals at a first frame rate; and
determining a second velocity prediction from the differential signals at a second frame rate; and
processing the first and second velocity predictions so as to derive a correction for extra or missing phase rotations, wherein a slower velocity prediction of the first and second velocity predictions is utilized to correct a faster velocity prediction of the first and second velocity predictions.
6. The method of claim 1 , further comprising:
averaging velocity predictions from the multiple frame rates so as to determine an average velocity prediction.
7. The method of claim 1 , further comprising:
a third velocity prediction from the differential signals at the first frame rate, wherein the first and third velocity predictions measure velocity along two orthogonal axes; and
determining a fourth velocity prediction from the differential signals at the second frame rate, wherein the second and fourth velocity predictions also measure velocity along the two orthogonal axes.
8. The method of claim 7 , wherein the 2D sensor array comprises an array of detector cells configured as a 2D comb array.
9. The method of claim 7 , wherein the first frame rate is 1/Δt 0 , the second frame rate is 1/Δt 1 , and the sensor array obtains the differential signals at the two frame rates by interleaving frames of width Δt 0 and frames of width Δt 1 .
10. The method of claim 9 , wherein the ratio of the first frame rate to the second frame rate is a non-integer number.
11. The method of claim 7 , wherein said processing of the first and second velocity predictions corrects extra or missing phase rotations along a first axis, and further comprising:
processing the third and fourth velocity predictions so as to derive a correction for extra or missing phase rotations along a second axis.
12. The method of claim 7 , further comprising:
averaging the first and second velocity predictions so as to determine a first average velocity prediction along a first axis; and
averaging the third and fourth velocity predictions so as to determine a second average velocity prediction along a second axis.
13. An optical navigation apparatus, the apparatus comprising:
a sensor array configured to generate multiple output signals based on optical signals detected by groups of detector elements in the array;
differential circuitry configured to receive the multiple output signals and to generate differential signals;
driver circuitry configured to drive the sensor array and differential circuitry so as to operate at multiple frame rates in an interleaved manner; and
a signal processing device configured to compute a first velocity prediction from the differential signals at a first frame rate and to compute a second velocity prediction from the differential signals at a second frame rate,
wherein the sensor array comprises a two-dimensional comb array,
wherein the signal processing device is further configured to compute a third velocity prediction from the differential signals at a first frame rate and to compute a fourth velocity prediction from the differential signals at a second frame rate, and
wherein the first and second velocity predictions measure motion alone a first axis and the third and fourth velocity predictions measure motion alone a second axis which is orthogonal to the first axis.
14. The apparatus of claim 13 , wherein the first frame rate is 1/Δt 0 , the second frame rate is 1/Δt 1 , and the sensor array obtains the differential signals at the two frame rates by interleaving frames of width Δt 0 and frames of width Δt 1 .
15. The apparatus of claim 14 , wherein the ratio of the first frame rate to the second frame rate is a non-integer number.
16. The apparatus of claim 13 , wherein the signal processing device is further configured to process the first and second velocity predictions so as to derive a correction for extra or missing phase rotations.
17. The apparatus of claim 13 , wherein the signal processing device is further configured to average velocity predictions from the multiple frame rates so as to determine an average velocity prediction.