Methods and systems for measuring speckle translation with spatial filters

#Navigational devices have been used with computers and other types of computing systems for many years. A computer mouse is one example of a navigation device. With a mechanical computer mouse, a ball rolls over a mouse pad as the mouse is moved. Interior to the mouse are wheels that contact the ball and covert its rotation into electrical signals representing orthogonal components of motion.

#Another type of computer mouse is an optical mouse. FIG. 1 is a diagrammatic illustration of a portion of an optical mouse according to the prior art. Mouse 100 includes light source 102 and motion sensor 104. Light source 102 is typically implemented a light-emitting diode, which emits light 106 towards surface 108. Motion detector 104 typically includes a camera that captures images of surface 108. Motion detector 104 also includes a digital signal processor that receives and analyzes a sequence of images. Motion detector 104 determines the speed and distance mouse 100 has moved across surface 108 based on differences in the captured images.

#The type and texture of surface 108 can impact how effectively motion detector 104 determines the speed and distance of mouse 100. For example, a rough or patterned surface can make it easier for motion detector 104 to determine the velocity of mouse 100, because differences in the images are more easily discernable. Other types of surfaces, such as glass surfaces, can make it more difficult for motion detector 104 to determine the velocity of mouse 100. Because glass is a transparent material, it typically does not have a sufficient amount of detectable imperfections or patterns that may be used to determine the speed and distance of navigation device 100.

#The invention will best be understood by reference to the following detailed description of embodiments in accordance with the invention when read in conjunction with the accompanying drawings, wherein:

#FIG. 1 is a diagrammatic illustration of a portion of an optical mouse according to the prior art;

#FIG. 2 is a diagrammatic illustration of a spatial filter in an embodiment in accordance with the invention;

#The following description is presented to enable one skilled in the art to make and use embodiments in accordance with the invention, and is provided in the context of a patent application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments. Thus, the invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the appended claims and with the principles and features described herein.

#With reference to the figures and in particular with reference to FIG. 2, there is shown a diagrammatic illustration of a spatial filter in an embodiment in accordance with the invention. Spatial filter 200 includes a repeating pattern of photodetectors 202, 204, 206, 208 that generate individual signals on signal lines 210, 212, 214, 216, respectively. Individual signals 210, 214 are summed 218 to create signal 220. Signals 212, 216 are summed 222 to create signal 224. Signal 220 is typically known as the in-phase (I) channel or the cosine channel, while signal 224 as the quadrature (Q) channel or the sine channel.

#The spatial filter shown in FIG. 2 may be used in the systems and methods described herein. Embodiments in accordance with the invention, however, are not limited to the spatial filter design of FIG. 2. Other types of spatial filters may be used, such as, for example, a liquid crystal cell array, photodiode array, lenticular grating, cylinder array, transmission grating, or a prism grating.