Abstract:
A system and method of manufacturing directed to an optical device with optical illumination. The optical device has a case for encasing an optical module. The optical module has one or more contact points in contact with the imaged surface. The suspension system uses a flexible connection to suspend the optical module over an opening in the bottom of the case. The flexible connection and the contact points control the distance between a surface and an optical lens within the optical module and allow the optical module to stay in the correct position.

Description:
RELATED APPLICATIONS 
     The present application relates to the subject matter of U.S. application Ser. No. 10/122,488, filed by Oliver Theytaz, et al. on Apr. 12, 2002. 
    
    
     BACKGROUND 
     A. Field of the Invention 
     The present invention relates generally to a suspension system for use with optical technology based displacement detection, and more particularly, to control critical distances along the optical path for use with optical technology in an input device. 
     B. Description of the Related Art 
     Optical technology displacement detection is used in many contexts, including in optical input devices for a computer or other device that requires an input device. There are many different types of input devices, including a mouse, a trackball, a digital pen, and a joystick. There are significant advantages to using optical input devices over mechanical and opto-mechanical input devices. For example, mechanical or opto-mechanical input devices have mechanical components that are more susceptible to breakdown, wear out, or clogging. Optical devices having only solid-state components are less susceptible to such breakdown, wear out, or clogging. 
     Optical input devices use a displacement of an image to detect movement of the input device relative to surface, e.g., a table surface in the case of a mouse or a ball in the case of a trackball. Optical input devices use an imaging lens, a sensor, and a light source to detect movement of the input device. Typically the light source is a light emitting diode (LED). Conventionally, the LED is attached with a clip to a printed circuit board (PCB). The sensor is mounted on the PCB. The sensor is attached to the imaging lens. There are two dimensions that are important to control to ensure the quality of the image. One important distance is the distance between the moving surface, e.g. table or ball, and the lens. The second important distance is the distance between the lens and the sensor. Conventional optical devices do not precisely control the distance between the moving surface and the lens. 
     Additionally, alignment of the imaging lens, the sensor, and the LED is critical. The alignment has a direct impact on the surface illumination and therefore on image quality. If the distance from the lens to the surface is not correct, oblique lighting creates a shift of the lighted area, which then does not match the area seen by the sensor, resulting in a partially dark image. Good surface illumination and good image quality are essential to an efficient optical system in an input device. 
     There are several reasons the alignment of the imaging lens, the sensor, and the LED is not always good. In conventional systems, critical optical dimensions are a result of many different parts stacked on top of each other creating an accumulation of errors. A critical optical dimension is a dimension that is critical for the optical system to create a sharp image of the surface, e.g., the table or the ball on the sensor; usually it is the path between the sensor and the surface. In the conventional optical path described above, there are errors introduced as a result of each part, e.g., the bottom of a case for the input device, the PCB, the clip, the LED, the sensor, and the imaging lens. This chain of parts is referred to as a chain of critical dimensions. 
     Another factor that leads to errors in alignment is that in conventional systems, positioning elements are built on the input device case to reduce the number of parts, cost and assembly time. When manufacturing the case, the highest priority is a cosmetic aspect of the product. Precise dimensions of the case assembly is a lesser priority, however, it can effect the alignment and the dimensions, as described above. Conventional systems use plastic that is chosen for cosmetic appearance and cost, not for mechanical precision. Consequently, the plastic used for the case adds to the chain of critical dimensions and is not a precision part. 
     Additionally, there are inherent errors introduced by using injected plastic parts. In conventional systems, most of the parts used are made of injected plastic. Injected plastic parts warp over time due to time and variations in temperature. Larger plastic pieces tend to warp more than smaller ones. The bottom of the case of the input device is made from a large piece of injected plastic. It is then a main cause of errors. In some conventional systems, this warping can degrade the performance of the input device or make it stop working completely. 
     There are several problems with conventional systems. One significant problem with conventional systems is the precise position of the imaging lens relative to the surface. This problem is caused by the chain of dimensions described above. Each part introduces more errors due to the tolerance of the particular connection between any two parts. Another problem is that a small error on the distance to the target can move a lighted spot away from its ideal position. 
     Another problem of conventional systems is electro static discharges (ESD). Sensitive electronics should be protected from these discharges because they can disturb their function or destroy the components. One conventional solution to the problem of ESD is to increase the distance between internal circuits and the outside world. A conventional solution is to use interleaving structures that make the path of a potential arc of discharge longer. A longer arc is less likely to have a discharge. Thus, there is a higher trigger voltage. The trigger voltage is the voltage difference required to trigger an ESD. To be effective, the trigger voltage should be higher than the specified ESD performance of the product. 
     Another problem of conventional systems is that conventional input devices are not waterproof. When a device is not waterproof, it can be damaged by spilled drinks or food or moisture entering the device as a result of humid climates. 
     What is needed is a system and method to precisely position the optical module relative to the imaged surface for use in an optical system that overcomes the above described problems and limitations. 
     SUMMARY OF THE INVENTION 
     The present invention provides a suspension system that reduces the number of critical parts. Thus, errors introduced in the chain of critical dimensions are reduced. One embodiment of the present invention provides an optical module that includes a sensor, a lens, a LED, and a LED clip correctly positioned together. Another aspect of the present invention suppresses the effects of the dimension errors in the bottom of the case from the critical dimensions chain. Yet another aspect of the present invention improves ESD immunity by providing a completely sealed structure for the bottom of the case. Finally, one embodiment of the present invention provides a waterproof-type barrier for the case. 
     One embodiment of the present invention flexibly couples the optical module to the bottom of the case. The bottom of the case can have an opening. The optical module can be positioned above the opening in the case such that the light illuminates a surface and the optical module protrudes through the opening. The surface can be a table or a mouse pad for an optical mouse or a ball for an optical trackball. One embodiment of the present invention uses an articulating arm to flexibly couple the optical module to the bottom of the case. The arm positions the optical module above the opening in the case. Optionally, a spring can also be used to apply a force on the optical module in the direction of the surface such that the optical module is in contact with the surface. Contact points can be part of the optical module and their position relative to the lens is precise because there is only one part in between. Thus, significantly reducing the accumulation of errors affecting the distance between the surface and the lens. When the optical module is in contact with the surface, the image is much sharper. In one embodiment, a flexible membrane can be attached to the bottom of the case over the opening in the case. The membrane is also attached to the optical module and acts to flexibly suspend the optical module over the surface. In one embodiment, the membrane is transparent to the wavelength or wavelengths of light used by the optical module so that light can pass through the membrane without having a hole in the membrane. In another embodiment, a hole can be made in the membrane to allow light to pass through. 
     Contact points can prevent the optical module from wearing out as a result of friction on the surface. Contact points can be any shape or size and are attached to the optical module or the membrane. The contact points can be made out of a low friction material or a hard material. 
     The present invention eliminates errors introduced by the bottom of the case because the optical module is flexibly suspended over an opening in the case. Therefore, even if there are imperfections in the bottom of the case or if the surface has irregularities, the imperfections will not alter the position of the optical module and therefore the illumination and the sharpness of the image. The position of the optical module is not dependent on the bottom of the case. 
     Additionally, a membrane can provide ESD protection. In one embodiment, the entire case can be lined with a membrane. In that embodiment, the case is protected from ESD because the membrane provides a barrier for discharge. Moreover in this embodiment, the membrane also provides a waterproof-type barrier. 
     The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram illustration of an overview of the present invention that includes a flexible suspension system. 
     FIG. 2 is an illustration of one embodiment of the present invention that includes a flexible articulating arm, a spring, a mounting module, a contact point, a surface, and feet. 
     FIG. 3 is an illustration of one embodiment of the present invention that includes a mounting module, a flexible arm, an optical module, and a contact point. 
     FIG. 4 is an illustration of one embodiment of the present invention that includes a flexible membrane, a mounting module, an optical module, a spring, a contact point, a surface, and feet. 
     FIG. 5A is an illustration of a bottom view of one embodiment of the present invention that includes a bottom of the case, a flexible membrane, an optical module, and a contact point. 
     FIG. 5B is an illustration of a side view of one embodiment of the present invention that includes a bottom of the case, a flexible membrane, an optical module and a contact point. 
     FIG. 5C is an illustration of a top view of one embodiment of the present invention that includes a flexible membrane, an optical module, a sensor chip, and a contact point. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description of the present invention is presented in the context of a suspension system for an optical device for use in, for example, a computer input device. In some embodiments, the principles disclosed may be implemented for use in an optical mouse, an optical trackball, an optical joystick, or an optical character recognition device. One skilled in the art will recognize that the present invention may be implemented in many other domains and environments, both within the context of suspension in optical devices, and in other contexts. Different embodiments of the present invention are now described with reference to the figures where like reference numbers indicate identical or functionally similar elements. Also in the figures, the left most digit of each reference number typically corresponds to the figure in which the reference number is first used. 
     Now referring to FIG. 1, there is shown a block diagram of an overview of a suspension system of the present invention for use in a mouse. FIG. 1 shows an optical module  105 , a case with an opening  100 , a flexible connection device  110 , one or more contact points  115 , a surface  130 , and one or more supporting feet  125 . The present invention is used in an optical input device. The principles of the present invention disclosed herein can apply to other optical devices, for example, a trackball, a joystick, or a digital pen. 
     The optical module  105  comprises an optical lens, optical sensor, light source, and a body. The body holds together the components of the optical module. It can also be used to shield the imaging light path from parasitic light or from direct light from the LED. The optical module  105  is flexibly attached to the case housing of the optical input device using flexible connection device  110 . In one embodiment, the optical module  105  is spring loaded against the surface, e.g., the table surface for a mouse or a ball surface for a trackball. The flexible connection device  110  can be any device that permits a flexible connection between the optical module  105  and the case  100 . Some embodiments of the flexible connection device  110  are shown in FIGS. 2-4 and described below. In one embodiment, the case has an opening  100 . The optical module is positioned above and protrudes through the opening in the case such that the light from the optical module illuminates the surface  130 . Supporting feet  125  support the bottom of the case  100  on the surface  130 . The supporting feet  125  are located on the bottom of the case  100  far from the optical module  105  and contact points  115 . 
     In embodiments with an opening in the case  100 , contact points  115  can be used to provide a contact between the surface  130  and the optical module  105 . Contact points  115  are points on the optical module that come into contact with the surface. The contact points  115  reduce wear and tear on the optical module that can be caused by friction with the surface. Contact points  115  are shown as individual points however, they can be in any shape. They can be individual points or can be one or more contact surfaces. For example, the contact surface can be in a ring around the optical module or in a “C” shape. Alternatively, contact points forming a triangle can be used. In one embodiment, the contact points  115  are made of a low friction plastic. Some examples of a low friction plastic are TEFLON™ and high molecular weight polyethylene (HMWPE). A thin sheet can be glued on the optical module bottom surface. One example of a thickness of the thin sheet is 0.3 mm. In other embodiments, the contact points  115  are made of a hard material. Some examples of hard material contact points are micro-balls made of zirconia, steel or ruby. In one embodiment, the contact points  115  are located close to an optical axis to minimize errors. An optical axis is typically the axis of symmetry of a light beam, for example from the LED to the target area on the table or from the lighted area through the imaging lens to the sensor. 
     Now referring to FIG. 2, there is shown one embodiment of the present invention. FIG. 2 shows the case with an opening  100 , optical module  105 , contact points  115 , a spring  230 , an articulating arm  200 , mounting module  205 , a top of the case  220 , a hinge or other flexible connector  235 , a surface  130 , and supporting feet  125 . In this embodiment, the articulating arm  200  is the flexible connection device  110 . The articulating arm  200  is designed to adjust the position and allow the movement of the optical module  105  in the vertical direction. Typically, the articulating arm is long enough so that the pivot point is a sufficient distance from the optical axis to minimize the azimuth change of the optical module  105  when the arm  200  moves up and down. The articulating arm  200  is attached to the case with a thin flexible section  235  to flex easily. In one embodiment, the bottom of the case  100 , the articulating arm  200 , and the body of the optical module are a single injected piece with a flexible section on the articulating arm  200 . Typically each part is the same material. The material can be Acrylonitrate-Butadiene-Styrene (ABS) or polycarbonate. In another embodiment, the bottom of the case  100  is a piece and the articulating arm  200  and the optical module body are another piece. The articulating arm  200  can be hinged to the bottom of the case  100 . The articulating arm  200  and optical module body can be made of a different material, for example, PolyOxyMethylene (POM), DELRIN™, or NYLON™. In another embodiment, the bottom of the case  100  is one piece, the articulating arm  200  and the optical module body are another piece and the arm is rigidly connected to the bottom of the case  100 . In this embodiment, the articulating arm  200  includes a flexible portion  235  near the mounting module  205 . p The articulating arm  200  is mounted to the case  100  using a mounting device  205 . The mounting module  205  can be any attachment mechanism. Some examples of attachment mechanisms are clipping, screwing, gluing, welding, soldering taping, or hinging. In one embodiment, the mounting module  205  is mounting to the bottom of the case  100  such that the articulating arm  200  is inside the case above the bottom of the case  100 . 
     The optical module is described above with reference to FIG.  1 . Contact points  115  are used to reduce friction between the optical module  105  and the surface  130 . The contact points are described above in reference to FIG.  1 . Supporting feet  125  are also described in reference to FIG.  1 . 
     The flexible portion  235  of the arm creates a force that presses the optical module against the table. Optionally, the spring  230  can be used to apply a downward force on the optical module  105 . The spring force can maintain the optical module&#39;s  105  position against the surface. Spring  230  can be any spring (coil, wire, blade, or any other type of spring) that will permit the appropriate spring force such that the optical module  105  is pressed against the surface. An appropriate spring force is a force such that the input device is not lifted off the surface. Typically, the force of the spring is lower than the weight of the input device. In one embodiment, the spring force is less than half the weight of the optical input device. Spring  230  can be attached to the top of the optical module  105  and also to the top of the case  220 . Alternatively, the spring can be inserted between the top of the optical module  105  and the top of the case  220 . Any method of attaching the spring  230  to the optical module  105  and the top of the case  220  can be used. 
     Now referring to FIG. 3, there is shown a bottom view of one embodiment of the present invention. FIG. 3 illustrates the bottom of the case of the optical device including a mounting module  300 , flexible articulating arm  305 , flexible portion  325 , optical module  105 , case opening  310 , bottom of case  320 , and contact points  115 . The optical module is described above with reference to FIG.  1 . 
     Articulating arm  305  is similar to articulating arm  200  in dimensions and flexibility. It allows for a flexible connection between the optical module and the case. In one embodiment, the articulating arm  305  can have a flexible portion or hinged connection  325 . However, articulating arm  305  is mounting to the bottom of the case  100  such that the articulating arm  305  is in an opening of the case. Shaded area  310  is the opening in the bottom of the case. The opening is shaped such that the optical module  105  can extend through the opening and also articulating arm  305  can be mounting in the opening. Contact points  115  can also be used to provide a contact between the optical module  105  and the surface  130 . Mounting module  300  is used to mount articulating arm  305  to the bottom of the case. Mounting module  300  is similar to mounting module  205  except it is located in the opening in the bottom of the case. In one embodiment, the mounting module  300  is a fixed portion of a hinge used to mount the articulating arm  305  to the bottom of the case  100 . 
     Now referring to FIG. 4, there is shown a side view of one embodiment of the present invention. FIG. 4 illustrates optical module  105 , the case with an opening  100 , top of case  220 , spring  410 , membrane  400 , mounting modules  405 , contact points  115 , supporting feet  125 , and surface  130 . The optical module  105 , contact points  115 , surface  130 , and supporting feet  125  are described above with reference to FIG.  1 . Membrane  400  is the flexible connection device  110 . The membrane  400  can be made of any flexible material. In one embodiment, the membrane  400  is transparent. In another embodiment, a hole is placed in the membrane  400  to allow light to pass through it. The membrane can be a thin sheet of plastic. Some examples of the plastic include a polyester foil, MYLAR™ foil, a polyurethane, and a silicone rubber. 
     The optical module  105  is attached to the membrane  400  using an attaching method. Some examples of attaching methods are ultrasonic welding, and glue. The membrane can also be pinched between two parts pressed together, for example, between an upper and a lower optical module body. In this embodiment, a hole is required for the attachment mechanism, for example, a pin, a clip, a fitting to mate properly together. The membrane  400  can be attached to the case  100  using mounting modules  405 . Mounting modules  405  use an attachment mechanism similar to the mounting modules described in reference to FIGS. 2 and 3 and similar to the attachment mechanism described above for attaching the optical module  105  to the membrane  400 . The flexibility of the membrane  400  allows slight vertical displacements of the membrane  400  to adapt to the position of the optical module  105 , keeping it in contact with the surface. A part of the membrane can be folded into bellows, allowing larger displacements with lower force required. These folds can be thermoformed into a flat sheet. 
     Optionally, a spring  410  can be used, attached to the optical module  105  and to the top of the case  220 , to provide a force on the optical module  105 . In one embodiment, the tension on membrane  400  provides the force on the optical module  105 . In one embodiment, contact points  115  (not shown) can also be used to reduce friction and wear and tear of the membrane  400  on the surface. 
     Additionally, the membrane  400  can provide protection from electrostatic discharge (ESD). Any ESD must travel a longer path around the membrane to the components within the case. The membrane  400  can completely enclose the bottom of the case  100  providing a barrier to electric discharge from the bottom of the mouse. Alternatively, the membrane  400  can be sealed to the bottom of the case  100  increasing the ESD path even more. Thus, protecting the components inside the case from ESD. This increased path length significantly increases the arc trigger voltage and therefore provides protection against ESD by raising it above what can normally happen in office environment. In one embodiment, no hole is made in the membrane. In that embodiment, the membrane is made out of a transparent material. 
     Additionally, the entire case can be lined with a similar membrane. Thus, again the device is protected from ESD. Also, lining the entire case with a membrane can provide a waterproof-type barrier for the case. The membrane can be thermo formed. Thermo forming allows easily deformed zones to permit small movements or position adjustments. 
     Now referring to FIG. 5A, there is shown a bottom view of one embodiment of the present invention. FIG. 5A illustrates the bottom of the case  100 , membrane  400 , contact points  115 , and the folds in the membrane  500 . The membrane is pinched between a lens and a friction ring. In one embodiment, the membrane is pinched ultrasonic welding. The membrane can be attached to the case bottom ultrasonic welding. The friction ring can be an injected part made of low friction material or including receptacles for three hard material micro spheres (not shown). FIG. 5A shows an alternate view of the embodiment shown in FIG.  4 . In this view, the folds in the membrane  500  can be seen as concentric circles. 
     Another embodiment similar to FIG. 4 is shown in FIG.  5 B. FIG. 5B is a side view of an embodiment of the present invention illustrating the bottom of the case  100 , a part of the optical module  105  (the LED), and the membrane  400 . Similarly to FIG. 5A, the folds in the membrane  400  can be seen in FIG.  5 B. 
     A top view of an embodiment of the present invention is shown in FIG.  5 C. FIG. 5C shows a sensor chip  505 , a part of the optical module  105  (the LED), the membrane  400 . The folds in the membrane  400  can be seen in FIG. 5C as concentric circles  500 . 
     From the above description, it will be apparent that the invention disclosed herein provides a novel and advantageous system for maintaining a constant distance between the surface and the lens in an optical device. The foregoing discussion discloses and describes merely exemplary methods and embodiments of the present invention. As will be understood by those familiar with the art, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. For example, the invention may be applied to other domains and environments, and may be employed in connection with additional applications where precise location of or distance from a sensor is desirable using inexpensive components. 
     Accordingly, the following description, while intended to be illustrative of a particular implementation, is not intended to limit the scope of the present invention or its applicability to other domains and environments. Rather, the scope of the present invention is limited and defined solely by the claims.