JP2018064301A - Image pick-up device, image reading apparatus, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pick-up device that can prevent power supply voltages supplied to light receiving devices from being different due to the positions of pixels arranged for every color.SOLUTION: An image pick-up device comprises: a plurality of light receiving devices that are arranged in one direction for every color and perform photoelectric conversion; and a plurality of power supply wires that supply power supply voltages from a power supply source to the plurality of light receiving devices. The plurality of power supply wires are formed in substantially the same shape from the power supply source to the light receiving devices at least for every color.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image sensor, an image reading apparatus, and an image forming apparatus.

  The scanner includes a photoelectric conversion element that photoelectrically converts reflected light from a document, an analog processing unit that performs processing such as A / D conversion on an analog image signal output from the photoelectric conversion element, and digitally converted image data In some cases, an image correction unit that performs various corrections on the image and an image transfer unit that transfers image data to the subsequent stage using LVDS or the like.

  In particular, a CCD is often used as a photoelectric conversion element, but a CMOS linear image sensor has attracted attention due to the recent demand for low power consumption. A CMOS linear image sensor is the same as a CCD in that incident light is photoelectrically converted by a photodiode (light receiving element).

  However, the CCD transfers the charge by the shift register, and after the transfer, the charge detection unit converts the charge to the voltage. On the other hand, the CMOS linear image sensor converts the voltage signal to the voltage detection unit in the pixel, and switches and analog buses. Through the output buffer. The CMOS linear image sensor is known to have low power consumption because the driving load for the CCD is only a switch.

  Further, Patent Document 1 discloses a pixel array unit in which a plurality of unit pixels are configured in a matrix array, and a plurality of power supplies disposed on the pixel array unit that supplies a power supply voltage used in each unit pixel. And an image sensor in which a power supply line is arranged in a direction intersecting a scan direction for outputting a video signal from a pixel array unit.

  However, in the conventional CMOS linear image sensor, the power supply wiring is formed so as to extend in the pixel arrangement direction for each color, and the power supply voltage is supplied from one end side of the pixel arrangement for each color. There is a problem in that the power supply voltage drops as the element decreases, causing unevenness in the image data.

  The present invention has been made in view of the above, and an imaging element and an image reading apparatus that can prevent the power supply voltage supplied to the light receiving element from being different depending on the position in the pixel array for each color. An object of the present invention is to provide an image forming apparatus.

  In order to solve the above-described problems and achieve the object, the present invention provides a plurality of light-receiving elements that are arranged in one direction to form a pixel region that performs photoelectric conversion, and a power supply source that is parallel to the one direction. A plurality of power supply lines for supplying a power supply voltage to a plurality of light receiving elements, and each of the plurality of power supply lines supplies a power supply voltage from the power supply source to each of the light receiving elements in the pixel region. The length is formed in the same length.

  According to the present invention, it is possible to prevent the power supply voltage supplied to the light receiving element from being different depending on the position in the pixel array for each color.

FIG. 1 is a configuration diagram illustrating the configuration of an image sensor mounted on an image forming apparatus or the like and a peripheral configuration. FIG. 2 is a diagram illustrating the power supply wiring in the imaging device in the comparative example. FIG. 3 is a graph showing the distribution of the power supply voltage in the main scanning direction in the image pickup device of the comparative example shown in FIG. FIG. 4 is a diagram illustrating a first example of the power supply wiring of the image sensor according to the embodiment. FIG. 5 is a diagram illustrating a second example of the power supply wiring of the image sensor according to the embodiment. FIG. 6 is a diagram illustrating a third example of the power supply wiring of the image sensor according to the embodiment. FIG. 7 is a diagram illustrating a fourth example of the power supply wiring of the image sensor according to the embodiment. FIG. 8 is a diagram illustrating a fifth example of the power supply wiring of the image sensor according to the embodiment. FIG. 9 is a diagram illustrating an outline of an image forming apparatus including an image reading apparatus having an image sensor.

  Embodiments of an image sensor will be described in detail below with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing a configuration of an image sensor 10 mounted on an image reading apparatus or an image forming apparatus and the periphery thereof. The image sensor 10 is a digital output type CMOS color linear image sensor, and operates according to the control of the CPU 11.

  As illustrated in FIG. 1, the imaging element 10 includes, for example, a photoelectric conversion unit 12, a signal processing unit 14, and a control unit 16. The photoelectric conversion unit 12 includes N (1 to n) light receiving elements (photodiodes) 120, 122, and 124 that are arranged in one direction for each of R, G, and B colors (using filters not shown). The image sensor 10 includes three light receiving elements 120, 122, and 124 of R, G, and B, and is configured to output a photoelectrically converted signal for each column. Hereinafter, the direction in which the light receiving elements 120, 122, and 124 are respectively arranged may be referred to as a main scanning direction (simply the main scanning direction) when the imaging element 10 is mounted on the image reading apparatus.

  The signal processing unit 14 includes N PGAs (Programmable Gain Amplifiers) 140 and N A / D converters (ADCs) 20, and the analog signal output from the photoelectric conversion unit 12 for each column. Amplify, convert to digital signal and output. Hereinafter, substantially the same components are denoted by the same reference numerals.

  Next, power supply wiring in the chip for supplying a power supply voltage to each pixel (each including a light receiving element) of the image sensor 10 will be described. First, the power supply wiring in the CMOS linear image sensor (imaging device) in the comparative example will be described. FIG. 2 is a diagram illustrating the power supply wiring in the imaging device in the comparative example. In FIG. 2, control signal lines and the like are not shown.

  As shown in FIG. 2, the imaging device of the comparative example has N (1 to n) pixels 34, 32, and 30 (light receiving devices 124 and 122) arranged in one direction for each of R, G, and B colors. , 120 respectively). The power supply source 40 has a sufficient area and width so that a potential difference hardly occurs even if the position is different in the image sensor (chip), and the power supply voltage (Vdd) supplied from the outside is substantially equal in the chip. To supply. Each of the N pixels 30, 32, and 34 is supplied with a power supply voltage from the power supply source 40 via the power supply wiring 400 for each color.

  In FIG. 2, the nth pixel from the side close to the power supply source 40 is represented by Pixn. The number N of pixels in the main scanning direction is determined by a desired reading size and reading resolution of the image reading apparatus. For example, in order to read a short side of 297 mm of an A3 size document at 600 dpi (600 dots per inch), Approximately N = 7000 pixels are required. The image sensor 10 has an array of pixels in a total of three lines for each of Red, Green, and Blue in the sub-scanning direction when mounted on the image reading apparatus.

  As shown in FIG. 2, when a power supply voltage is supplied from one side in the main scanning direction to each of the pixels 30, 32, and 34, the impedance of the power supply wiring 400 increases as the distance from Pix1 and Pix2 close to the power supply source 40 increases. As the voltage increases, the voltage drop increases.

  FIG. 3 is a graph showing the distribution of the power supply voltage Vdd in the main scanning direction in the imaging device of the comparative example shown in FIG. In the imaging device of the comparative example shown in FIG. 2, as shown in FIG. 3, a voltage drop occurs as the power supply source 40 advances to the other end in the main scanning direction. That is, it is conceivable that the pixel characteristics change (deteriorate) depending on the power supply voltage. In this case, the image data becomes uneven in the main scanning direction as the power supply voltage Vdd decreases. Note that the distribution of the power supply voltage Vdd shown in FIG. 3 similarly occurs in the sub-scanning direction when the same power supply wiring is formed in the sub-scanning direction.

  Next, power supply wiring in the image sensor 10 according to the embodiment will be described. FIG. 4 is a diagram illustrating a first example of the power supply wiring in the image sensor 10 according to the embodiment. In FIG. 4, control signal lines and the like are not shown.

  In the first example of the power supply wiring in the image sensor 10, in order to make the length of the power supply wiring 402 for the pixels 30, 32, 34 the same for each color regardless of the pixel position in the main scanning direction, A power supply source 42 having a length equivalent to the length in the main scanning direction is arranged. Each of the power supply sources 42 and the like has a sufficient area and width so that a potential difference hardly occurs even if the position is different in the image pickup device (chip), and supplies a power supply voltage (Vdd) supplied from the outside. It is assumed that the chips are supplied almost evenly.

  N power supply wirings 402 are formed so as to have the same number as the N pixels 30, 32, and 34 arranged in the main scanning direction. Each power wiring 402 is formed so that the shape from the power supply source 42 to each of the pixels 30, 32, 34 (light receiving elements 120, 122, 124) is substantially the same for each color. Each power wiring 402 is formed so as to extend in a direction substantially orthogonal to the main scanning direction from the end of the power supply source 42 substantially parallel to the main scanning direction.

  Therefore, in each of the N pixels 30, 32, and 34, the length of the power supply wiring 402 from the power supply source 42 is equal for each color, the wiring impedance is equal, and the power supply voltage distribution in the main scanning direction is uniform. It becomes uniform.

  FIG. 5 is a diagram illustrating a second example of the power supply wiring in the image sensor 10 according to the embodiment. In FIG. 5, control signal lines and the like are not shown.

  In the second example of the power supply wiring in the image sensor 10, the power supply wiring 404, 406, and 408 are provided independently from the power supply source 42 to each of the pixels 30, 32, and 34. Each of the power supply wires 404, 406, and 408 is formed so that the shape from the power supply source 42 to each of the pixels 30, 32, and 34 (light receiving elements 120, 122, and 124) is substantially the same for each color. Further, each power supply wiring 404, 406, 408 is formed so as to extend from the end of the power supply source 42 substantially parallel to the main scanning direction in a direction substantially orthogonal to the main scanning direction.

  Therefore, in the second example of the power supply wiring in the image sensor 10, even if a pixel of a certain color consumes power, the consumption current does not flow to the power supply wiring of another color. That is, the second example of the power supply wiring in the image sensor 10 can prevent crosstalk between colors.

  FIG. 6 is a diagram illustrating a third example of the power supply wiring in the image sensor 10 according to the embodiment. In FIG. 6, control signal lines and the like are not shown.

  In the third example of the power supply wiring in the image pickup device 10, in addition to the configuration shown in the second example of the power supply wiring in the image pickup device 10, each of the amplification units 140 and each of the A / D converters 20 is also provided. The power supply wiring 410 and the power supply wiring 412 are provided independently. In addition, the power wirings 410 and 412 are formed in substantially the same shape from the power supply source 42 to the amplification unit 140 and the A / D converter 20. Each of the power supply wires 410 and 412 is formed so as to extend from the end of the power supply source 42 substantially parallel to the main scanning direction in a direction substantially orthogonal to the main scanning direction.

  FIG. 7 is a diagram illustrating a fourth example of the power supply wiring in the image sensor 10 according to the embodiment. In FIG. 7, control signal lines and the like are not shown.

  In the fourth example of the power supply wiring in the imaging device 10, a power supply source 44 is provided in parallel to the power supply source 42, and the power supply source 42 and the power supply source 44 are connected via the power supply wires 414, 416, and 418. A power supply voltage Vdd is supplied to each of the pixels 30, 32, and 34. In addition, the power supply wires 414, 416, and 418 are formed in substantially the same shape for each color from the power supply source 42 and the power supply source 44 to the pixels 30, 32, and 34 (light receiving elements 120, 122, and 124). Has been. The power supply wires 414, 416, and 418 extend in a direction substantially orthogonal to the main scanning direction from the end of the power supply source 42 and the end of the power supply source 44 that are substantially parallel to the main scanning direction. Is formed.

  Therefore, in the fourth example of the power supply wiring in the image sensor 10, it is possible to suppress the voltage drop by suppressing the difference in wiring impedance between the colors and reduce the characteristic difference between the colors.

  FIG. 8 is a diagram illustrating a fifth example of the power supply wiring in the image sensor 10 according to the embodiment. In FIG. 8, control signal lines and the like are not shown.

  In the fifth example of the power supply wiring in the image sensor 10, power supply sources 46r, 46g, and 46b are provided for each color. In the fifth example of the power supply wiring in the image sensor 10, the end of the power supply source 46g is formed between the Red pixel column (each pixel 34) and the Green pixel column (each pixel 32). . Further, in the fifth example of the power supply wiring in the image sensor 10, the end of the power supply source 46b is formed between the Green pixel row (each pixel 32) and the Blue pixel row (each pixel 30). . That is, the power supply sources 46g and 46b are provided in the non-pixel region between the pixel columns (lines). Each of the power supply wirings 420 for supplying the power supply voltage from the power supply sources 46r, 46g, 46b to the respective pixels 30, 32, 34 is provided independently for each pixel.

  Further, each power supply wiring 420 is formed in substantially the same shape from any one of the power supply sources 46r, 46g, 46b to the pixels 30, 32, 34 (light receiving elements 120, 122, 124). Each power supply wiring 420 is formed to extend in a direction substantially orthogonal to the main scanning direction from each end of the power supply sources 46r, 46g, 46b substantially parallel to the main scanning direction. Specifically, the power supply wiring 420 has the same wiring impedance and the power supply voltage Vdd is independently supplied to all the pixels 30, 32, and 34. Accordingly, the pixels 30, 32, and 34 do not cause a voltage drop due to a current flowing through other pixels. As described above, in the fifth example of the power supply wiring in the image sensor 10, the distribution of the power supply voltage Vdd is uniform in both the main scanning direction and the sub-scanning direction. The fifth example of the power supply wiring in the image sensor 10 is a configuration that is possible because the linear image sensor has a gap between pixel columns (lines), and is a configuration that cannot be efficiently realized by the area image sensor.

  The configuration of the power supply wiring in the image sensor 10 is not limited to the configuration shown in the first example to the fifth example, and may be a configuration in which these are arbitrarily combined.

  Next, an image forming apparatus including an image reading apparatus having the image sensor 10 according to the embodiment will be described. FIG. 9 is a diagram illustrating an outline of an image forming apparatus 50 including an image reading device 60 having the image sensor 10. The image forming apparatus 50 is, for example, a copying machine or an MFP (Multifunction Peripheral) having an image reading device 60 and an image forming unit 70.

  The image reading device 60 includes, for example, the image sensor 10, an LED driver (LED_DRV) 600, and an LED 602. The LED driver 600 drives the LED 602 in synchronization with a line synchronization signal output from the control unit 16. The LED 602 irradiates the original with light. The image sensor 10 receives reflected light from the document in synchronization with a line synchronization signal or the like, and a plurality of light receiving elements (not shown) generate electric charges and start accumulation. Then, after performing AD conversion and the like, the image sensor 10 outputs image data to the image forming unit 70 via a parallel-serial conversion circuit or the like.

  The image forming unit 70 includes a processing unit 80 and a printer engine 82, and the processing unit 80 and the printer engine 82 are connected via an interface (I / F) 84.

  The processing unit 80 includes an LVDS 800, an image processing unit 802, and a CPU 11. The CPU 11 controls each part of the image forming apparatus 50 such as the image sensor 10. In addition, the CPU 11 (or the control unit 16) performs control so that the respective light receiving elements start generating charges according to the amount of received light substantially simultaneously.

  The image sensor 10 outputs, for example, image data of an image read by the image reading device 60, a line synchronization signal, a transmission clock, and the like to the LVDS 800. The LVDS 800 converts received image data, a line synchronization signal, a transmission clock, and the like into parallel 10-bit data. The image processing unit 802 performs image processing using the converted 10-bit data, and outputs image data and the like to the printer engine 82. The printer engine 82 performs printing using the received image data.

  As described above, the image forming apparatus 50 includes the image reading device 60 having the image sensor 10. Therefore, the length (shape) of the power supply wiring from the power supply source to each pixel is equalized at least for each color, and the color It is possible to prevent the power supply voltage supplied to the light receiving element from being different depending on the position in the pixel array.

10 Image sensor 11 CPU
DESCRIPTION OF SYMBOLS 12 Photoelectric conversion part 14 Signal processing part 16 Control part 20 A / D converter 30, 32, 34 Pixel 40, 42, 44, 46r, 46g, 46b Power supply source 50 Image forming apparatus 60 Image reading apparatus 70 Image forming part 120 , 122, 124 Light receiving element 140 PGA
400-420 Power supply wiring

JP 2006-229935 A

Claims (10)

A plurality of light receiving elements that form a pixel region that is arranged in one direction and performs photoelectric conversion;
A plurality of power supply wirings for supplying a power supply voltage to the plurality of light receiving elements from a power supply source parallel to the one direction;
Each of the plurality of power supply wirings is
The imaging device is characterized in that a power supply voltage is supplied from the power supply source and the length of the pixel region to each of the light receiving elements is the same. Each of the plurality of light receiving elements for each color,
Each of the plurality of power supply wirings is
The imaging device according to claim 1, wherein a power supply voltage is supplied from the power supply source, and the length of the pixel region to each of the light receiving elements is the same for at least each color. The plurality of power supply wirings are:
The imaging device according to claim 1, wherein the imaging element is formed so as to extend from the end of the power supply source in the one direction. The plurality of power supply wirings are:
4. The imaging device according to claim 1, wherein the imaging element is formed so as to extend in the one direction from each of a plurality of ends of the power supply source. 5. At least one of the ends of the power supply source is
At least one of the plurality of light receiving elements arranged in the one direction of the first color to perform photoelectric conversion and at least one of the plurality of light receiving elements arranged in the one direction of the second color to perform photoelectric conversion The imaging device according to claim 1, wherein the imaging device is formed between the heels. The plurality of power supply wirings are:
The imaging device according to claim 1, wherein the imaging device is provided independently for each of the plurality of light receiving elements. A plurality of AD converters for converting the electrical signals photoelectrically converted by the plurality of light receiving elements into digital signals;
A power supply voltage is supplied to each of the plurality of AD converters from the power supply source, and further includes a plurality of other power supply wirings each having the same length. Item 7. The imaging device according to any one of Items 1 to 6. A plurality of amplifying units for amplifying electrical signals photoelectrically converted by the plurality of light receiving elements;
The power supply voltage is further supplied to each of the plurality of amplification units from the power supply source, and further includes a plurality of other power supply wirings each having the same length. The imaging device according to any one of 1 to 7.   An image reading apparatus comprising the image pickup device according to claim 1. An image reading apparatus according to claim 9,
An image forming unit for forming an image read by the image reading device;
An image forming apparatus comprising:

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