Circuit and method for determining motion with redundant comb-arrays
A method is provided for sensing displacement of an optical sensor relative to a surface, the sensor having at least first and second arrays with a plurality of photosensitive elements. The method involves: (i) generating for each array first set of quasi-sinusoidal signals at a first time and a second set of quasi-sinusoidal signals at a second time in response to motion of light received thereon; (ii) computing from said first and second sets of signals phase angle changes for signals received from each array; (iii) computing from said first and second sets of signals radius values for signals received from each array; (iv) computing unwrapped phase angle changes for signals received from each array; and (v) combining said unwrapped phase angle changes for each of said arrays using radius-weighted-averaging to provide a single weighted average of unwrapped phase angle change resulting from said motion of light.
1. A method for sensing displacement of an optical sensor relative to a surface, the optical sensor having at least a first and a second array, each array having a plurality of photosensitive elements, the method comprising:
generating for each array a first set of quasi-sinusoidal signals at a first time and a second set of quasi-sinusoidal signals at a second time in response to motion of light received thereon in at least a first direction (x);
computing from said first and second sets of quasi-sinusoidal signals from each of said arrays a phase angle change (ΔØ x1 , ΔØ x2 ) for said first and second sets of quasi-sinusoidal signals received from each of said arrays;
computing from said first and second sets of quasi-sinusoidal signals from each of said arrays radius values (R x1 , R x2 ) for said first and second sets of quasi-sinusoidal signals received from each of said arrays; and
combining said phase angle changes (ΔØ x1 , ΔØ x2 ) for each of said arrays using radius-weighted-averaging to provide a single weighted average phase angle change ΔØ x resulting from said motion in the first direction.
2. A method according to claim 1 , wherein combining said phase angle changes (ΔØ x1 , ΔØ x2 ) using radius-weighted-averaging comprises combining said phase angle changes (ΔØ x1 , ΔØ x2 ) using the following equation:
Δ
ϕ
x
=
R
x
1
×
Δ
ϕ
x
1
+
R
x
2
×
Δ
ϕ
x
2
R
x
1
+
R
x
2
where R x1 is the radius value for the quasi-sinusoidal signals received from the first array, R x2 is the radius value for the quasi-sinusoidal signals received from the second array, ΔØ x1 is the phase angle change for the quasi-sinusoidal signals received from the first array, ΔØ x2 is the phase angle change for the quasi-sinusoidal signals received from the second array, and ΔØ x is the weighted average phase angle change.
3. A method according to claim 1 , further comprising computing unwrapped phase angle changes (ΔΦ x1 , ΔΦ x2 ) for said first and second sets of quasi-sinusoidal signals received from each of said arrays, and wherein combining said phase angle changes comprises combining said unwrapped phase angle changes.
4. A method according to claim 3 , wherein computing the unwrapped phase angle changes comprises computing velocity predictors for said first and second sets of quasi-sinusoidal signals received from each of said arrays using average velocity values from a number, K, of preceding successive frames, where K is a whole number greater than or equal to two.
5. A method according to claim 4 , wherein computing velocity predictors comprises computing velocity predictors using radius-weighted-averaging.
6. A method according to claim 1 , wherein generating for each array first and second sets of quasi-sinusoidal signals further comprises generating for each array quasi-sinusoidal signals at said first and second time in response to motion of light in at least a second direction (y),
whereby displacement of the optical sensor relative to the surface in two-dimensions is sensed.
7. A method according to claim 1 , wherein the sensor is a speckle-based sensor configured to identify a location on the surface based on a complex interference pattern created by a light reflected from the surface from a narrow band light source.
8. An optical navigation system for use in a data input device to sense displacement of the data input device relative to a surface, the system comprising:
an optical sensor having at least a first and a second array, each array having a plurality of photosensitive elements; and
a signal processing circuit comprising:
means for generating for each array a first set of quasi-sinusoidal signals at a first time and a second set of quasi-sinusoidal signals at a second time in response to motion of light received thereon in at least a first direction (x);
means for computing from said first and second sets of quasi-sinusoidal signals from each of said arrays a phase angle change (ΔØ x1 , ΔØ x2 ) for said first and second sets of quasi-sinusoidal signals received from each of said arrays;
means for computing from said first and second sets of quasi-sinusoidal signals from each of said arrays radius values (R x1 , R x2 ) for said first and second sets of quasi-sinusoidal signals received from each of said arrays; and
means for combining said phase angle changes (ΔØ x1 , ΔØ x2 ) for each of said arrays using radius-weighted-averaging to provide a single weighted average phase angle change ΔØ x resulting from said motion in the first direction.
9. An optical navigation system according to claim 8 , wherein the signal processing circuit further comprises means for computing unwrapped phase angle changes (ΔΦ x1 , ΔΦ x2 ) for said first and second sets of quasi-sinusoidal signals received from each of said arrays, and wherein the means for combining said phase angle changes comprises means for combining said unwrapped phase angle changes.
10. An optical navigation system according to claim 9 , wherein the means for computing the unwrapped phase angle changes comprises means for computing velocity predictors for said first and second sets of quasi-sinusoidal signals received from each of said arrays using average velocity values from a number, K, of preceding successive frames, where K is a whole number greater than or equal to two.
11. An optical navigation system according to claim 10 , wherein the means for computing velocity predictors comprises means for computing velocity predictors using radius-weighted-averaging.
12. An optical navigation system according to claim 8 , wherein the means for generating for each array first and second sets of quasi-sinusoidal signals further comprises means for generating for each array quasi-sinusoidal signals at said first and second time in response to motion of light in at least a second direction (y),
whereby displacement of the data input device relative to the surface in two-dimensions can be sensed.
13. An optical navigation system according to claim 8 , wherein the sensor is a speckle-based sensor configured to identify a location on the surface based on a complex interference pattern created by a light reflected from the surface.
14. An optical navigation system according to claim 8 , wherein the first and second arrays are positioned at different locations within an imaging area of the optical sensor illuminated by light reflected from the surface.