Patent Application
20070091064
This invention relates to optical navigation devices and more particularly to such devices where the depth of field of the optics is variable.
Optical navigation devices are now commonly used, for example with personal computers, for allowing the computer user to “point” to a location on the display screen. An optical navigation device, often called a mouse, projects a light beam onto a surface. The light beam from a mouse moving across the surface reflects from imperfections (artifacts) on the surface. A sensor then picks up the reflections and the direction of travel of the mouse is determined from the surface artifacts as they are being reflected onto the sensor.
This works well when the navigation surface is at a relatively fixed position (Z dimension) with respect to the light beam and the sensor. In existing navigation devices the optical beam has a depth of field (DOF) which is usually about +/−5 mm. Thus, if the navigation surface is positioned more than 5 mm below the surface of the device (as it would be if a 30 mm glass plate were to be positioned between the navigation device bottom and the navigation surface) the reflected light would not impact properly on the sensor due to the Z dimension falling outside the limits of the DOF. In such a situation, and depending upon the exact Z dimension of the navigation surface, directional determinations would either be impossible to make or would be severely affected.
An optical navigation device containing an adjustable depth of field light source is positioned with respect to a surface such that the depth of field of light source can be adjusted to match the Z dimension of a particular surface. In one embodiment, a plurality of individual light sources are used each having a different angle of reflection from the surface. By selecting the light source having an angle of reflection to match the Z dimension of the surface to be navigated the device can be used over a wide range of Z dimensions. In one embodiment, the selection of the proper light source is accomplished upon start-up of the device with respect to a particular surface and in another embodiment a user can adjust the light surface to obtain optimal performance.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
Continuing in
Although depicted with two light sources 12 and 13 yielding two distinct depths of field, additional light sources (not shown) could be added, thereby increasing the number or range of depths of field. For example, by adding a third light a thicker (or a second) transparent medium could be used. If the thicker medium were to be double the size of medium 25 then the Z dimension would be approximately 60 mm. The light channels are advantageously arranged such that the depths of field are adjacent to each other, increasing the overall depth of field and, correspondingly the overall operable range of Z distances in which the device will function properly.
Using multiple light channels allows a transparent medium, such as medium 25, to be inserted between bottom surface 11 of device 10 and actual work surface 16 so long as the Z distance remains within the operable range. The transparent medium need only be transparent to the particular light required by the sensor. If desired, the wavelengths of the different light sources could be different to yield different depths of field perhaps depending upon the intermediary medium.
As depicted in
Alternatively, selection may also be accomplished by testing each light source. Starting with both light sources 12 and 13 off and then turning on light source 12. If the reflect light from light source 12 impacts upon the sensor then light source 12 is selected to remain on. Otherwise light source 12 will be turned off and light source 13 will be turned on. If the reflected light from light source 13 impacts the sensor then light source 13 will be selected and will remain on. Otherwise the process will be started again with light source 12 until the Z distance of the device is brought to within the depth of focus for light 12 or light 13.
The selection process may also be invoked if the Z distance changes during the operation of the navigation device, such as when a mouse is moved from a mouse pad onto a plate of glass above a navigation surface. When the Z distance changes to a value that is outside of the current depth of focus, reflected light will no longer impact upon the sensor, thus triggering the selection process. Such selection process could be similar to the ones described above or the light sources with depths of field closest to the previous depth of field may be tested before the light sources with depths of field farthest from the current depth of field
One or more buttons (not shown) may be arranged on device 10 such that pressing a particular button may invoke the automated selection process. If desired, the button could allow a user to select an individual light source, or change the selected light source in a predetermined manner, for example, by cycling through all the light sources with successive presses, thereby giving the user of the device control of the depth of field.
Alternatively, the depth of field may be controlled by the system (such as by processor 19 connected by transmission path 18) to which the navigation device is connected. In the example of a personal computer with attached mouse, software on the computer may be used to interactively select the desired depth of field in an automated or user controlled fashion. Alternatively, CPU 17 within device 10 could control the selection of light sources.
When using multiple light channels, the depths of field could partially overlap each other still increasing the overall depth of field but at the same time ensuring a smooth transition when changing light channels.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
