Optical navigation device with optical navigation quality detector
View Patent ↗An optical navigation system, e.g. optical mouse, determines optical navigation quality by examining some or all of the photosensors of a frame or monitoring intermediate or final results of the motion estimation system. The optical navigation quality is then used to determine the navigation output produced by the optical navigation system.
1. A navigation system comprising:
an optical navigator configured to generate a navigation output for motion estimation; and
an Optical Quality Estimator connected to the optical navigator to receive the navigation output, the Optical Quality Estimator being configured to process the navigation output to estimate the quality of the motion estimation of the optical navigator with respect to accuracy and to generate a quality signal.
2. A navigation system, as defined in claim 1 , further comprising:
a housing that includes the optical navigator and the Optical Quality Estimator; and
a switch, attached to the housing and operably connected to the Optical Quality Estimator, provides an input signal to the Optical Quality Estimator when the switch is depressed.
3. A navigation system, as defined in claim 1 , the optical navigator including:
a photosensor array configured to receive reflected light from a surface and to generate a current frame signal indicative of the reflected light;
an analog to digital converter connected to the photosensor array to receive the current frame signal and configured to generate a digital signal;
a frame memory connected to the analog to digital converter to receive the digital signal and configured to provide a previous frame signal;
a motion likelihood calculator connected to the frame memory to receive the digital signal and the previous frame signal and configured to generate a motion likelihood output indicative of a motion likelihood distribution; and
a maximum likelihood selector connected to the motion likelihood calculator to receive the likelihood output and configured to generate a motion output signal.
4. A navigation system, as defined in claim 3 , further including a source configured to emit a radiation towards the surface, wherein the source is selected from a group comprising visible light, infrared light, and ultraviolet light.
5. A navigation system, as defined in claim 4 , wherein the source is selected from a group comprising coherent, partially coherent, and incoherent electromagnetic sources.
6. A navigation system, as defined in claim 3 , the Optical Quality Estimator being connected to the analog to digital converter of the optical navigator to receive the digital signal as the navigation output, the digital signal including a plurality of photosensor values, the Optical Quality Estimator being configured to process the photosensor values to see if the number of distinct features in the digital signal exceeds a threshold to estimate the quality of the motion estimation of the optical navigator with respect to accuracy.
7. A navigation system, as defined in claim 3 , the Optical Quality Estimator being connected to the analog to digital converter of the optical navigator to receive the digital signal as the navigation output, the digital signal including a plurality of photosensor values, the Optical Quality Estimator being configured to process the photosensor values to compute a histogram of the photosensor values and measure the concentration of the histogram to estimate the quality of the motion estimation of the optical navigator with respect to accuracy.
8. A navigation system, as defined in claim 3 , the Optical Quality Estimator being connected to the motion likelihood calculator of the optical navigator to receive the motion likelihood output as the navigation output, the motion likelihood output including likelihood values corresponding to different possible movements, the Optical Quality Estimator being configured to process the likelihood values to estimate the Quality of the motion estimation of the optical navigator with respect to accuracy.
9. A navigation system, as defined in claim 8 , the Optical Quality Estimator being configured to check if the maximum value of the likelihood values differs from other values of the likelihood values by an amount that is statistically significant.
10. A navigation system, as defined in claim 3 , wherein the Optical Quality Estimator compares the magnitude of the velocity of the motion output signal with a preset threshold.
11. A navigation system, as defined in claim 3 , wherein Optical Quality Estimator compares the magnitude of the acceleration of the motion output signal with a preset threshold.
12. A navigation system, as defined in claim 3 , comprising:
a synthetic navigation generator connected to the optical navigator to receive a previous motion output signal that is indicative of a previous motion estimation, the synthetic navigation generator being configured to generate a synthetic motion signal in response to the previous motion output signal; and
the Optical Quality Estimator being configured to select one of the motion output signal and the synthetic motion signal.
13. A navigation system, as defined in claim 12 , wherein the synthetic motion signal represents no movement.
14. A navigation system, as defined in claim 12 , wherein the synthetic motion signal represents continuation of previously observed movement as indicated by the previous motion output signal of the optical navigator.
15. A navigation system as defined in claim 12 , wherein the synthetic motion signal represents continuation of previously observed movement as indicated by the previous motion output signal of the optical navigator with decreasing magnitude with increasing time.