OPTICAL MOUSE

Abstract: An optical mouse (100) wherein the light source (106) is reflected off an optical pattern pad (22) and is placed such that a lens (120) at a predetermined distance from the optical pad focuses the reflected light directly onto an inverted integrated circuit (124) mounted on and through a hole (126) in a printed wiring board (118), the integrated circuit being housed in a clear plastic package. The path from the lens to the integrated circuit package is provided with an optical guide (122) such that the distances from the pattern pad to the lens, and from the lens to the optical sensor (128) in the integrated circuit, is fixed upon manufacture and assembly without any further optical adjustment. The inverted state of the integrated circuit chip allows a fixed distance to be provided through the hole in the printed wiring board rather than from above it as is common in the prior art.

Description: This invention relates to a cursor control device, otherwise known as an optical mouse, for use with an interactive display oriented computer system to provide movement for a visible cursor from position to position on a display screen of such a system. An optical mouse is a hand held cursor positioning unit with an overall weight of approximately three ounces (1 ounce = 31.3g). Its outputs are digital signals related to its positional change as it is moved over a pattern pad. Two or three or more button switches can be provided on top of the optical mouse for the operator to make functional selections. The optical mouse can interface with a host system via a multi-wire cable assembly. The optical mouse detects motion across a defined pattern pad by means of optical sensors and converts this motion to x and y pulse train outputs. The direction and speed of the motion is contained in the phase shift and frequency of the output signals which is decoded and utilised in displaying the cursor on a screen such as a cathode ray tube of a personal computer or workstation. At various times, the push buttons which operate microswitches within the optical mouse itself, can be utilised for certain functions on the surface of the screen of the cathode ray tube. For example, depressing the left button when the cursor is below and to the left of the left hand most letter of a word and the moving the mouse to the right hand most letter of a word and then depressing the right hand button of an optical mouse, can cause the highlighting of the word on the cathode ray screen for deletion thereof, or changing of the font or the size of the letters within the font, for example. Also, depression of one or the other switches can institute an action on the screen such as a printing function or a deletion function when the cursor is over a predetermined place on the screen as may be necessary. United States Patent 4,521,772, discloses a cursor control device, or "optical mouse" for use with an interactive display oriented computer system to provide movement for a visible cursor from position to position on a display screen of such a system. The device includes an IC (integrated circuit) chip that contains an optical sensor array and circuitry to bring about detectable bit maps based upon a plurality of sensor cells making up the array. The distinguishable bit maps are employed as a means for comparison to provide an output indicative of the direction and amount of movement of the cursor control device relative to an optical contrasting input to the array, the output being employed as a means to move the visible cursor from position to position on a display screen. GB-A -2 154 734 discloses an optical mouse of the type having unfolded optics. A light source is positioned on one side of an isolating wall internal to the mouse body, while a sensor is placed on the opposite side of the wall. Light from the light source reflects off of an image surface at an angle such that it is made incident upon the sensor. While this reference discloses unfolded optics in an optical mouse, it does not discuss the positioning of a printed wiring board or other circuitry which may be necessary for operation of the optical mouse. U. S. Patent 4,521,773 discloses an imaging array which provides a plurality of distinguishable bit map images and comprises an array of sensor cells capable of sensing radiation. The cells are connected in a manner to form distinguishable bit map images through a pattern of correspondence among the cells. Each bit map image formed comprises a combination of one or more cells indicative of detecting an image pixel within a field of array cells that have been non-indicative of such detection. The pattern of correspondence may be one of inhibition of the operation of other cells in the array or one of indication of operation to other cells in the array. Various patterns of correspondence can be created among the cells creative of bit map images. Bit map images may consist of combinations of responsive cells within a field of non-responsive cells in the array. For example, each bit map image may comprise radiation responsive array cells that have sensed a sufficient quantity of radiation within a field of cells which have not sensed radiation or have been inhibited from sensing radiation. On the other hand, each bit map image may comprise cells that have not sensed a sufficient quantity of radiation within a field of cells that have sensed a sufficient quantity of radiation. An application of the imaging array is in an IC chip for a cursor control device or an "optical mouse' for use with an interactive display oriented computer system to provide movement for a visible cursor from position to position on a display screen of such a system. One disadvantage of the optical mouse set forth in the cited two US patents is the fact that a reflecting mirror comprising folded optics is necessary and alignment thereof is required during the manufacture and assembly process. The alignment of the optical system is labour intensive and therefore expensive, to say nothing of the fact that folded mirror optics themselves must also be provided. According to the present invention there is provided an integrated circuit package including a housing, a printed wiring board mounted within said housing, a photosensitive active circuit element mounted on said printed wiring board adjacent one surface of said housing, characterised in that the printed wiring board has at least one hole defined therein for allowing light to pass from a first side of the printed wiring board to an opposite side of the printed wiring board, and the active circuit element being located on the first side of the printed wiring board and mounted to the printed wiring board by way of wires such that the active circuit element is optically aligned with the hole, and capable of receiving light from the opposite side of the printed wiring board through the hole. The package forms, an optical mouse wherein the light source is reflected off the optical pattern pad and is placed such that a lens at a predetermined distance from the optical pad focuses the light directly, i.e. avoiding folded optics onto an inverted integrated circuit mounted on and through the hole in the printed wiring board, the housing of the package being at least in part clear plastics material. The path from the lens to the integrated circuit package provides an optical guide such that the distances from the pattern pad to the lens, and from the lens to the optical sensor in the integrated circuit, is fixed upon manufacture and assembly without any further optical adjustment. The inverted state of the integrated circuit chip allows a fixed distance to be provided through the hole in the printed wiring board rather than from above it as is common in the prior art. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1a is the top view of a standard prior art integrated circuit package indicating pin placement and numbering thereof, Figure 1b is the pin placement of the reversed, i.e., inverted, integrated circuit package and its pin placement, and numbering as utilised in the present invention; Figure 2a shows an integrated circuit wherein an optical sensor array is placed in the integrated circuit and its normal pin placement and bending thereof in relation to the optical sensor of the prior art; Figure 2b shows the reverse bend to the pins of an integrated circuit with such an optical sensor array such that when the integrated circuit is reversed and placed into a printed wiring board, the optical sensor array is always at a predetermined fixed distance from the integrated circuit package to the printed circuit board in accordance with the invention, and Figure 3 is a diagrammatic cross section of an optical mouse comprising the present invention utilising a lens, an optical guide, and a reverse bent, inverted circuit package. With reference to Figure 3, the optical mouse 100 is shown to be covered by housing 108. This can be of moulded plastic of any of the well known types in the prior art. The major components of the optical mouse are seen to be the button 116, which operates microswitch 114 via the operating point 115. There could be two or even three or more of these buttons and microswitches depending on the choice of the system and the required operations. Normally, two or three microswitches and accompanying buttons are utilised, as more than two or three becomes confusing to an operator and adds to the complexity of the printed wiring board 118. The switch 114 would be mounted in holes in the printed wiring board 118. Not shown on the printed wiring board 118 are other electrical components, such as resistors and capacitors and connectors which are necessary for the operation of the circuit but are not directly relevant to the present invention. Light source 106 is included which is mounted in a housing 107. Lens 120 is shown installed in the optical guide 122 which fits through a hole 126 in the printed wiring board 118. The light would shine upon the optical sensor array 128 as seen in Figure 3. The configuration of integrated circuit 124 will be discussed hereinafter in relation to Figures 1 and 2. In operation, therefore, the light source 106 would be utilised to shine its light towards hole 110 in the bottom part of the cover 108 of the optical mouse 100. The light source 106 could be a light emitting diode which could emit light in the visible or the infrared region depending upon the sensitivity of the optical sensor away 128 mounted in the integrated circuit 124. There could be one, two, or even three of these light emitting sources 106 mounted in housing 107 depending upon the sensitivity of the optical sensor array 128 and whether or not redundant light sources are desired by the designer. Only one light source 106 is necessary, however, for the principles of the present invention. As the light strikes the pattern on pad surface 22, light and dark shadows are reflected from the surface, some of which is focused by lens 120 through optical guide 122 onto the optical sensor array 128. The operation of the pattern on surface 22 and the meaning of the various signals as detected thereby are fully covered in the two patents set forth above. Because the light source 106 is mounted in housing 106, and lens 120 is situated at the end of the optical guide 122, which extends through the hole 126 in printed wiring board 118, and that the integrated circuit 124 fits as close to the optical guide as can be made depending upon the length of the leads as bent in reverse direction, the manufacture of the optical mouse is made simple by the fact that no optical alignment or measurement is necessary subsequent to the assembly of the parts of the present optical mouse. The integrated circuit 124 is unique in its manufacture and its implementation in the present invention. Figure 1a shows the pin numbering of a standard integrated circuit package with the pin number 1 in the upper right hand corner if viewed from the top. The alignment indentation is between pins 1 and 16. It is in this top surface that prior art integrated circuits would have its optical sensor array. However, the integrated circuit package of the present invention has been reversed and inverted to allow the top surface to become the bottom surface so as to allow for immediate alignment of the bottom surface thereof when the integrated circuit package is mounted in its housing in the optical mouse. Figure 1b shows the inverted package pinout as would be the case for the integrated circuit of the present invention. Since the pins are reversed in its inverted state, care must be made to note where the pins are in the wiring process of the design of the printed wiring board. Figure 3 shows the integrated circuit 124 sitting on top of the optical guide 122 which acts as the spacer from the lens 120 to the optical sensor array 128. However, the optical guide could be shorter above the hole 126 in the printed wiring board which could allow for the pins of the integrated circuit to establish the height above the board in which the optical sensor array sits, in that most integrated circuits have a wider dimension to the pins as they immediately extend out from the body of the integrated circuit which narrows down to a less wide dimension in the pins. Thus, if the holes in the printed circuit board are made only to accommodate the narrow dimension of the pins of the integrated circuit, then when the integrated circuit is positioned within the printed circuit or printed wiring board, the shoulder of the place where the dimension changes from a narrow to wide width of the pin can be used as the spacing aspect, assuming that the pins of the integrated circuit package are bent accurately. Figure 2a shows a normal, prior art, integrated circuit wherein the active circuit chip element is on top of the integrated circuit bonding plate 134 in the housing 124 and the leads are bent away from this operative surface. In Figure 2b is shown an integrated circuit for use in the present invention wherein the pins are bent toward the active optical sensor array 128 in the reverse position, and when the entire integrated circuit is inverted such that the pins 130 are pointed downward, the active optical sensor array surfaces also point downward and would be positioned on the printed wiring board 118 as seen in Figure 3. In order to allow for the active optical sensor array surface 128 to be accurately positioned from the lens at the focal length thereof, the entire integrated circuit package can be made of clear plastic, of the type which could allow for accurate placement and distance from the lens to both the active optical sensor array and the surface of pad 22. Feet 136 in Figure 3 can provide for an accurate placement of the bottom surface of housing 108 to be distanced from pad 22. The foot distance 136 from the pad to the lens can be taken into account in the design of the system if it is desired to have such feet 136. It would be possible to incorporate lens 120 into the integrated circuit package; however, this would require custom moulds and special handling of the new package shape. It is possible, however, as the compound used for encapsulation of the integrated circuit package 124 is optically clear plastic and is similar to that used in prior art plastic lenses. In addition, higher orders of sophistication are achievable in that the optical source, prisms, integrated lenses, and registration pins and/or guides may also be incorporated into the custom plastic packages. Since all alignment is to the printed wiring board assembly 118, it becomes feasible, and thus desirable, to make the total assembly of parts by snapping them together rather than using screws and plastic welds. One of the basic goals of the present invention was to create an inexpensive and accurate optical assembly which would be compatible with automated assembly and testing. As stated above, in prior art integrated circuit packages, the chip die is on the top of the metal bonding plate. With the method of packaging as set forth herein, the chip die is mounted on the affected bottom of the plate, and since the active area is on the chip die, the method of packaging will allow for: 1. automatic integrated circuit sensor to lens alignment; 2. in line rather than folded optical path; 3. single layer printed wiring board assembly may be used; 4. automatic integrated circuit insertion may be used; 5. single lens fixed focus; 6. simplified illumination; and 7. reduced assembly steps and costs.

Claims: An integrated circuit package including a housing (108), a printed wiring board (118) mounted within said housing (108), a photosensitive active circuit element (128) mounted on said printed wiring board (118) adjacent one surface of said housing (108), characterised in that the printed wiring board (118) has at least one hole (126) defined therein for allowing light to pass from a first side of the printed wiring board (118) to an opposite side of the printed wiring board (118), and the active circuit element (128) being located on the first side of the printed wiring board (118) and mounted to the printed wiring board (118) by way of wires (130) such that the active circuit element (128) is optically aligned with the hole (126), and capable of receiving light from the opposite side of the printed wiring board (118) through the hole (126). An integrated circuit package as claimed in claim 1, characterised in that the package forms a cursor control device (100), or optical mouse (100), including optical guide means (122) mounted in the hole (126) and in line with the active circuit element (128), lens means (120) mounted at the end of the optical guide means (122) away from said active circuit element (128), and light emitting means (106) mounted adjacent the lens means (120) and the optical guide means (122) to illuminate an area a predetermined distance from the lens means (120), wherein light reflected from the area is gathered and focussed by the lens means(120), through the optical guide means (122) onto the active circuit element (128). An integrated circuit package as claimed in claim 1 or claim 2, characterised in that said housing (108) comprises at least in part clear plastics material.

Inventors: CHERRY, ROBERT S., WILLIAMS, LISA M.
Applicants: XEROX CORPORATION
Application year: 1987
Main classification: G06K11
IPC codes: G06F3