Patent Application
20070188457
1. Field of the Invention
The present invention relates to optics. More specifically, the present invention discloses an optimized optical system comprising an optical mouse illumination guide with a concave lens for spreading light to create a uniform, low contrast, illumination pattern.
2. Description of the Prior Art
Traditionally, an optical computer mouse uses a light-emitting diode (LED) to graze a surface with illuminating light, and detects patterns in reflected light from the surface to compute motion.
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The light beam 170 enters the illumination guide 130 through a first flat surface 1311, is reflected off a first reflector 1301, is reflected off a second reflector 1302, and exits the illumination guide 130 through a second flat surface 1312. The light beam 170 exits the mouse body through an aperture 107 in the base plate 102, reflects off a reference surface 10, and reenters the illumination guide 130 through a third flat surface 1313.
The light beam 170 shines onto an optical sensor 150, which detects patterns in the reference surface 10 revealed by the light. These patterns may be caused by roughness in the reference surface 10, or may be caused by colorations of the surface 10.
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However, this low angle causes most of the light emitted by the LED to have an uneven illumination pattern, thereby causing problems for the sensor. For example, some areas of the illumination pattern are very bright, whereas other areas a dim. The LED 140 must therefore be of high intensity in order to overcompensate for the dim areas, thereby consuming a large amount of power, which is then wasted on generating lost light, and which also creates heat dissipation issues.
Furthermore, this requires the LED 140 and other components to be correspondingly large, increasing the size of the mouse. In addition to increasing materials costs, this creates a lower limit on the attainable size of the mouse.
Moreover, the structure of this design places the LED 140 and the optical sensor 150 in different planes, and requires cuts in the PCB 110, thereby further increasing the design complexity of the mouse, and also increasing the required size.
In addition, the structure of the prior art mouse is typically open internally, and in many cases transparent materials are used for the housing 101 and base plate 102 for aesthetic considerations, thereby allowing external light not generated by the mouse 100 to reach the optical sensor 150, and internally, allowing randomly scattered light from the LED 140 to reach the optical sensor 150. This undesirable light can only serve to interfere with the imaging performed by the optical sensor 150.
Therefore there is need for an improved optical system for the mouse which will allow smaller overall size and lower power consumption while also reducing design complexity.
To achieve these and other advantages and in order to overcome the disadvantages of the conventional method in accordance with the purpose of the invention as embodied and broadly described herein, the present invention provides an optical mouse system that directs illumination at a surface from an angle of typically less than about thirty-three degrees in respect to a 90 degree angle from the surface, thereby increasing the optical efficiency of the system and reducing power requirements, and also thereby increasing the sensitivity of the system to the relative movement of the reference surface, and also thereby shrinking size requirements.
The present invention provides an optimized optical system with a concave surface for a lens for sensing motion of a surface relative to the optical system. The concave surface is situated on the illumination guide where the illumination beam exits the mouse to be reflected by a reference surface. Instead of focusing light in order to create a high intensity, high contrast illumination pattern, the present invention spreads the light to create a uniform, low contrast, illumination pattern.
When light passes through a convex lens, the convex lens causes light rays to refract convergently. This therefore creates a light pattern that is focused into a small point of light. This compact, high contrast, light pattern creates problems for the sensor and can cause the sensor to misinterpret motion of the mouse.
However, a concave surface causes light rays to refract divergently. As a result, the light is spread and creates a uniform and low contrast illumination pattern. This allows the sensor to more accurately sense motion of the mouse. As a result, the cursor representing mouse position moves across the screen more accurately and smoothly. As a result, computer user satisfaction is increased.
The present invention further provides an optical mouse system in which the illumination source is mounted on the same surface or plane as the optical sensor, thereby simplifying construction and shrinking size requirements.
The present invention further provides an optical mouse system in which the optical sensor may optionally be substantially isolated from extraneous light, both that which is generated by the mouse and that which is foreign to the system, thereby increasing the sensitivity of the system to the relative movement of the reference surface.
These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of preferred embodiments.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:
a is a diagram showing a cross section of a prior art optical computer mouse;
b is a diagram illustrating the path of a light beam generated by a prior art mouse;
a is a sectional diagram illustrating internal components of an optical computer mouse according to an embodiment of the present invention;
b is a sectional diagram illustrating internal components of an optical computer mouse according to an embodiment of the present invention;
a is a detail diagram illustrating an illumination guide of an optical computer mouse according to an embodiment of the present invention;
b is an drawing illustrating an illumination guide of an optical computer mouse according to an embodiment of the present invention;
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
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An illumination source 240 and an optical sensor 250 are mounted on a printed-circuit board (PCB) 210. The illumination source 240 is typically a light-emitting diode (LED) in the SMD form factor, but the present invention may also use an infrared-emitting diode, a laser diode, or other suitable illuminating radiation emission source matched to the type of illumination that the optical sensor 250 can receive.
A holder 220 is disposed over and around the illumination source 240, such that the holder 220 in combination with the PCB 210 isolates the illumination source 240 inside a source cavity 2201 so that the illumination it generates only exits through an exit aperture 2211. Likewise, the holder 220 is disposed over and around the optical sensor 250, such that the holder 220 in combination with the PCB 210 surrounds the optical sensor 250, isolating the optical sensor 250 inside a sensor cavity 2202 so that the illumination the optical sensor 250 receives, only enters through an entry aperture 2212.
An illumination guide 230 rests in an illumination guide cavity 2203 of the holder 220, retained securely in place by a clip 260. The clip 260 has a main aperture 267 through which the illumination exits, reflects off a reference surface 10, and re-enters the optical computer mouse.
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The illumination guide 230 may be made of polymer, glass, or other refractive material which is substantially transparent to the wavelength of the illumination being used. Optically, the illumination beam 270 is emitted from the illumination source 240, enters the illumination guide 230 through the first surface 2311, is reflected from the first reflector 2301, is reflected from the second reflector 2302, and exits the illumination guide 230 through the second surface 2312.
The first surface 2311 is a convex surface that focuses the illumination beam 270 into a collimated light beam. The second surface 2312 is a concave surface which spreads the light exiting the illumination guide 230.
Optionally, to spread the illumination beam 270 more evenly, the first surface 2311 and second surface 2312 may be shaped, for example by stippling or otherwise hazing their surfaces. Optionally, to spread the scattered illumination from the reference surface 10 to the optical sensor 250 for the purpose of removing detail from the image formed on the optical sensor 250, the third surface 2313 may be textured. Please note that the first surface 2311, the third surface 2313, and/or the fourth surface may be flat surfaces in some embodiments.
Continuing with discussion of
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The illumination source illuminates the first surface 2311 of the illumination guide 230 with about sixty degrees of its output. The first surface 2311 is designed with the correct focal length to collimate this illumination into an illumination beam 270. Any illumination which is moving in other directions is scattered or absorbed by the holder (not shown), which is preferably made of a black nonreflective material such as a polymer.
The first reflector 2301 and second reflector 2302 reflect the illumination beam 270 through the second surface 2312, which spreads the illumination beam 270 substantially to illuminate the reference surface 10 through the main aperture. The second surface 2312 is a concave lens which spreads the light to create a uniform illumination pattern on the reference surface 10.
Illumination which is scattered from the reference surface 10 re-enters the illumination guide 230 through the third surface 2313, travels through the illumination guide 230, exits through the fourth surface 2314, and falls on the image plane of the optical sensor.
The length of the first reflector 2301 is the width of the exit aperture divided by the sine of forty-five degrees. The length of the second reflector 2302 is the same as the width of the exit aperture (since the first reflector 2301 was selected to be at a forty-five degree angle) divided by the sine of the quantity forty-five degrees minus half the angle of incidence from the normal. In an embodiment of the present invention, it was chosen to be thirty-two degrees which simplifies to the sine of twenty-nine degrees.
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It should be noted that these values can be selected to meet design requirements. For example, depending on the distance of the light source or illumination guide to the reference surface, the illumination pattern can be larger or smaller. Also, the curvature of the concave lens can be designed to meet requirements.
In summary, the scattered light emitted from the light source is collected by the first lens which transforms the light into a collimated light beam. After reflecting off two reflective surfaces, the light is spread into a uniform light illumination pattern by the concave lens. This provides a low contrast uniform light pattern on the reference surface. This light reflects off the surface and enters the illumination guide through a third lens which focuses the light into a collimated light beam. The third lens acts substantially like the first lens. The light then exits the illumination guide via the fourth lens and falls on the sensor.
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The optical mouse system of the present invention also provides a substantial improvement over the prior art by reducing power usage and materials costs, and by simplifying the internal construction of the optical mouse core. Isolation of the illumination source from the optical sensor, and of the optical sensor from external illumination, helps to increase sensitivity of the system. Furthermore, its smaller form factor gives designers more flexibility in housing design.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the invention and its equivalent.
