Optical mouse chip with silicon retina structure

[0002] The present invention relates to an optical mouse chip with silicon retina structure, especially to an optical mouse chip applied to image edge abstraction and detection of moving body.

[0003] The use of a hand operated pointing device for use with a computer and its display has become almost universal. For example, an optical mouse is used in conjunction with a specific mouse pad. The recently developed mouse can operate on pad of various stuffs by image recognition skill.

[0004] FIG. 1 shows a block diagram of a prior art optical mouse chip, which comprises an image acquisition unit 1a, a digital signal processing unit 2aand a converting unit 3a. The image acquisition unit 1acaptures an image corresponding to the motion of mouse and converts an analog image signal corresponding to image into a digital image signal. The digital signal processing unit 2areceives the digital image signal and manipulates the digital image signal to find the moving direction of the image and the converting unit 3aconverts the moving direction of the image into PS/2 signal or quadrant signal format compatible to mouse adaptor or mouse controller.

[0005] In above-mentioned optical mouse chip, the processing unit 2areceives the digital image signal from the image acquisition unit 1aand manipulates the digital image signal to find the moving direction of the image. It is hard for the processing unit 2ato detect finer image or faster movement of image if the data amount of the image acquisition unit 1ais increased.

[0006] FIG. 2 shows the block diagram of a moving image detector, which comprises a plurality of silicon retina cells 8a. Each of the silicon retina cells 8acomprises a sensor 4a, an abstracting unit Sa, a delay unit 6aand a comparing unit 7a. The sensor 4adetects image variation to generate an analog signal and converts the analog signal to a digital signal. The abstracting unit 5ais connected to an output end of the sensor 4aand converting the digital signal to an image-moving signal. The delay unit 6ais connected to an output end of the abstracting unit 5aand delays the image-moving signal of the abstracting unit 5a. The comparing unit 7ais connected between the output end of an abstracting unit 5ain the same silicon retina cell 8aand the delay unit 6aof previous same silicon retina cell 8ato discriminate the movement of the image.

[0007] Moreover, a plurality of the silicon retina cells 8acan be grouped to synthesis a neuro network; and the moving speed and the moving direction of an image can be determined by interactive algorithm with delay and comparison operations. This interactive algorithm does not involve the processing unit 2aand the processing time is not increased with the data amount of the image acquisition unit 1a.

[0008] However, in above-mentioned moving image detector, the delay unit 6arequires time adjustment to comply with the moving speed of image in certain condition. Moreover, binary pulses are generated along upward/downward and right/left directions to determine the moving direction of image. The moving direction of image may be incorrectly judged if binary pulses are not generated along some directions.

[0009] It is an object of the present invention to provide an optical mouse chip with silicon retina structure and having fixed delay time between adjacent scan, thus determining the moving direction of image with enhanced speed and resolution.

[0010] It is another object of the present invention to provide an optical mouse chip with silicon retina structure, which selects a largest one among a plurality of direction parameters to determine the moving direction of the image after one scanning process, thus accurately determining the moving direction of image.

[0011] It is still another object of the present invention to provide an optical mouse chip with silicon retina structure, which use bipolar transistor to find edge variation of the image.

[0012] To achieve above object, the present invention provides an optical mouse chip with silicon retina structure comprising an image sensor array, an accumulator and a comparing/selecting unit. The image sensor array is a neuro network composed of a plurality of silicon retina cells and each of the silicon retina cells sensing a direction parameter of an image along an axis. The accumulator is connected to an output end of the image sensor array and sums the direction parameters of the image along different axes. The comparing/selecting unit is connected to an output end of the accumulator and selects a largest one from the sum of direction parameters of the image along different axes to determine a moving direction of the image.

[0013] The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:

[0014] FIG. 1 shows a block diagram of a prior art optical mouse chip;

[0015] FIG. 2 shows the block diagram of a prior art moving image detector

[0016] FIG. 3 shows a schematic diagram of a preferred embodiment of the present invention;

[0017] FIG. 4 shows the connection among a plurality of silicon retina cells;

[0018] FIG. 5 shows the structure of one silicon retina cell;

[0019] FIG. 6 shows the architecture of the image sensor of the present invention;

[0020] FIG. 7 shows the architecture of an accumulating module; and

[0021] FIG. 8 shows the architecture of the comparing/selecting unit of the present invention.

[0022] FIG. 3 shows a schematic diagram of a preferred embodiment of the present invention. The present invention provides an optical mouse chip with silicon retina structure, which comprises an image sensor array 1, an accumulator 2 and a comparing/selecting unit 3.

[0023] The image sensor array 1 is used for image detection and is a neuro network composed of a plurality of silicon retina cells 4. The neuro network can perform high-speed computation with parallel and distributed processing ability. Moreover, the neuro network can process vast amount of data and output moving parameters of image such as upward/downward, rightward/leftward movement and no motion.

[0024] The accumulator 2 is connected to an output of the image sensor array 1 and composed of five accumulating modules 21 for accumulating five different directional parameters (+X, +Y, no motion, −X, −Y as shown in this figure) output by the silicon retina cells 4. More particularly, each of the accumulating modules 21 comprises a plurality of row accumulating sections 211 and an area accumulating section 212. The row accumulating sections 211 are used to accumulate the five different directional parameters output by a row of the silicon retina cells 4. The area accumulating section 212 is used to accumulate the output of the plurality of row accumulating sections 211, thus obtaining net result of the five moving parameters of the image.

[0025] The comparing/selecting unit 3 is connected to an output of the accumulator 2 and selects a largest value among the five different directional parameters to determine the moving direction of the image.

[0026] With reference now to FIGS. 4 and 5, the connection among a plurality of silicon retina cells 4 and the structure of one silicon retina cell 4 are demonstrated. In FIG. 4, a silicon retina cell 4 is connected to four adjacent silicon retina cells 4A, 4B, 4C and 4D on upper/lower and right/left directions thereof to form a neuro network. The silicon retina cell 4 has five outputs (SHIFT_O, SHIFT+X, SHIFT−X, SHIFT+Y, SHIFT−Y) associated with the five different directional parameters of image and the five outputs are sent to silicon retina cell 4C in next row. Moreover, the silicon retina cell 4 receives output data from four adjacent silicon retina cells 4A, 4B, 4C and 4D (CELL_R, CELL_D, CELL_L, CELL_U). In this way, the silicon retina cell 4 communicates with its four adjacent silicon retina cells 4A, 4B, 4C and 4D to recognize the moving direction of image. Alternatively, the silicon retina cell 4 can also be connected to eight adjacent silicon retina cells along upper, lower, right, left, upper right, lower right, upper left, lower left directions to synthesis larger neuro network and recognize finer moving direction of image.

[0027] As shown in FIG. 5, the silicon retina cell 4 comprises an image sensor 41, a first shift register 42, a second shift register 43, five comparators 44 and five shifters 45. The image sensor 41 detects the edge variation of the image and generates a detection signal RETINA_OUT with rising edge or falling edge when edge variation occurs. The first shift register 42 is connected to an output of the image sensor 41 and stores the detection signal RETINA OUT of the image sensor 41. The second shift register 43 is connected to an output of the first shift register 42 and stores the detection signal RETINA_OUT output by the first shift register 42. Each of the comparators 44 is connected to the output of the first shift register 42 and recognizes the variation of moving direction for the image by comparison operation. The shifters 45 are connected to an output of corresponding comparators 44 and shift the five outputs (SHIFT_O, SHIFT+X, SHIFT−X, SHIFT+Y, SHIFT−Y) associated with the five different directional parameters of image to the silicon retina cell 4C in next row.

[0028] The image sensor 41 sends a detection signal RETINA_OUT to the first shift register 42 during a scanning process and the detection signal RETINA_OUT is moved from the first shift register 42 to the second shift register 43 in next scanning process. At this time, the output of the second shift register 43 is connected to the comparator 44 thereof and to the comparator 44 of adjacent silicon retina cells 4A, 4B, 4C and 4D. Similarly, the output end of the second shift register 43 of the adjacent silicon retina cells 4A, 4B, 4C and 4D are connected to the comparators 44 of the silicon retina cell 4. More particularly, the delay time between two scanning process is fixed and depends on operation frequency. Therefore, the drawback of variable delay time in prior art is solved. Moreover, the delay time between two scanning process is decreased when operation frequency is increased.

[0029] In case that the level of the detection signal stored by the image sensor 41 into the first shift register 42 is corresponding with one of the levels of the output signals (CELL_R, CELL_D, CELL_L, CELL_U) from the second shift register 43 of the adjacent silicon retina cells 4A, 4B, 4C and 4D during previous scan, the corresponding comparator 44 generates a pulse to indicate the detected direction of the image. In case that the level of the detection signal stored by the image sensor 41 into the first shift register 42 is corresponding with the detection signal stored in the second shift register 43 of the silicon retina cell 4 pre se during previous scan, the corresponding comparator 44 generates a pulse SHIFT_O to indicate image having no motion.

[0030] FIG. 6 shows the architecture of the image sensor 41 of the present invention. The image sensor 41 comprises a smoothing bipolar transistor (BJT) 411, an isolated bipolar transistor (BJT) 412 and a current comparator 413. The smoothing bipolar transistor 411 is used with the isolated bipolar transistor 412 to detect the edge variation of an image; and the smoothing bipolar transistor 411 and the isolated bipolar transistor 412 generate currents I_ESand I_EI, respectively. The current comparator 413 is connected to the emitter of the smoothing bipolar transistor 411 and the emitter of the isolated bipolar transistor 412 to sense the variation of the currents I_ESand I_EI, respective, and generates a detection signal RETINA_OUT. The image sensor 41 of the present invention further has an enhanced NMOS transistor 414 as resistor connected to the bases of adjacent smoothing bipolar transistors 411 to provide a smoothing circuit with the smoothing bipolar transistors 411.

[0031] Both of the smoothing bipolar transistor 411 and the isolated bipolar transistor 412 have current variation when the image to be detected has motion. The smoothing bipolar transistor 411 has different current variation magnitude than the isolated bipolar transistor 412 due to the effect of the smoothing circuit. The current comparator 413 can discriminate the different current variation magnitude and provides a detection signal RETINA OUT with rising edge or falling edge when edge variation occurs.

[0032] FIG. 7 shows an accumulating module 21 of the accumulator 2. With reference also to FIG. 3, the input of the accumulator 2 is connected to the output of the image sensor array 1. The bit number of the row accumulating section 211 is determined by the number of the silicon retina cell 4 in a row. The output of the row accumulating section 211 is connected to the row accumulating section 211 of next row. The output of the row accumulating section 211 in the last row is connected to the area accumulating section 212. The bit number of the area accumulating section 212 is determined by the total number of the silicon retina cells 4. The area accumulating section 212 generates a cumulative sum SUM_OUT.

[0033] FIG. 8 shows the architecture of the comparing/selecting unit 3 of the present invention. The comparing/selecting unit 3 of the present invention comprises a comparing/selecting section 31 with five inputs and four outputs and a plurality of enhanced NMOS transistors 32. The comparing/selecting section 31 receives five cumulative sums SUM_OUT associated with the five different directional parameters of image and selects a largest value among the five different directional parameters to determine the moving direction of the image. The comparing/selecting section 31 generates a pulse to indicate the moving direction of the image. Therefore, the incorrect recognition of moving direction of the image can be prevented. The enhanced NMOS transistors 32 are connected to output ends of the comparing/selecting section 31 and used to output the pulse for indicating the moving direction of the image. The pulse has a period determined by an operation frequency OUT from a timing control circuit (not shown). When the operation frequency OUT is increased, the elapsed time for image sensing and comparison is reduced, thus refining the recognition of moving direction.

[0034] To sum up, the optical mouse chip with silicon retina structure according to the present invention has following advantages:

[0035] 1. Determining the moving direction of image with enhanced speed and resolution.

[0036] 2. Accurately determining the moving direction of image.

[0037] 3. Ability to processing vast amount of data.

[0038] Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.