JP6662165B2 - Signal processing device, photoelectric conversion element, image reading device, image forming device, and control method - Google Patents

Description

  The present invention relates to a signal processing device, a photoelectric conversion element, an image reading device, an image forming device, and a control method.

  In a batch exposure type photoelectric conversion element (for example, a CMOS sensor), when the voltages written to the capacitances of the respective channels in a column are sequentially read after photoelectric conversion, a preliminary operation is performed by a circuit before reading the first channel. A technique is known in which the operating conditions at the time of reading each channel are made uniform.

  Japanese Patent Application Laid-Open No. H11-163873 discloses a preparatory operation performed on an analog processing unit so that the analog processing unit can execute a preparatory operation before the analog processing unit starts processing an analog signal output from a pixel group. There is disclosed a photoelectric conversion element having a signal supply unit for supplying a signal necessary for the above.

  However, conventionally, there has been a problem that the time required for one cycle of the operation becomes longer due to the additional time for executing the preliminary operation.

  The present invention has been made in view of the above, and when a plurality of circuits sequentially perform substantially the same operation, the operation conditions of each circuit are made substantially the same without delaying the start of operation of each circuit. It is an object of the present invention to provide a signal processing device, a photoelectric conversion element, an image reading device, an image forming device, and a control method that can realize the above.

To solve the above problems and achieve the object, the present invention is, by performing the operation a plurality of circuits same sequentially, a signal processing unit for outputting a signal by performing processing on the input signal, the signal has an initialization unit for initializing the processing unit, wherein the signal processing unit, a preliminary operation of the circuit which operates the second or later becomes the same operating conditions and operation state before the start of the operation, the It is performed until the initialization unit finishes initializing the signal processing unit and before the circuit that operates first starts operating.

  ADVANTAGE OF THE INVENTION According to this invention, when a several circuit performs substantially the same operation | movement sequentially, it is possible to make the operating conditions of each circuit substantially the same, without delaying the start of operation of each circuit. To play.

FIG. 1 is a block diagram illustrating a configuration example of a signal processing device according to the embodiment. FIG. 2 is a timing chart illustrating an operation of the signal processing device as a comparative example. FIG. 3 is a timing chart showing the operation of the signal processing device as an embodiment. FIG. 4 is a block diagram illustrating a configuration example of the photoelectric conversion element according to the embodiment. FIG. 5 is a diagram illustrating a configuration example of the conversion processing unit illustrated in FIG. FIG. 6 is a timing chart showing a first operation example of the photoelectric conversion element. FIG. 7 is a timing chart showing a second operation example of the photoelectric conversion element. FIG. 8 is a timing chart showing a third operation example of the photoelectric conversion element. FIG. 9 is a timing chart illustrating a fourth operation example of the photoelectric conversion element. FIG. 10 is a timing chart illustrating a fifth operation example of the photoelectric conversion element. FIG. 11 is a diagram illustrating a modification of the pixel unit included in the conversion processing unit. FIG. 12 is a timing chart illustrating an operation example of a photoelectric conversion element including a modification of the conversion processing unit. FIG. 13 is a diagram illustrating an outline of an image forming apparatus including an image reading device having a photoelectric conversion element.

  Hereinafter, a signal processing device according to an embodiment will be described first with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating a configuration example of a signal processing device 1 according to the embodiment. The signal processing device 1 includes, for example, a signal processing unit 2 and an initialization unit 3.

  The signal processing unit 2 includes a plurality of (for example, three or more) circuits for performing processing, and the plurality of circuits sequentially perform substantially the same operation to perform processing on an input signal and output a signal. The initialization unit 3 initializes the signal processing unit 2 before the signal processing unit 2 processes the input signal. Further, the signal processing unit 2 performs a preparatory operation in which the operation state of the second and subsequent circuits is substantially the same as the operation state before starting operation until the initialization unit 3 finishes initializing the signal processing unit 2. And is performed before the first operating circuit starts operating.

  FIG. 2 is a timing chart illustrating an operation of the signal processing device 1 as a comparative example. In the operation as the comparative example illustrated in FIG. 2, in the signal processing device 1, the initialization unit 3 initializes the signal processing unit 2 before the signal processing unit 2 processes the input signal. For example, the initialization unit 3 initializes an input signal line of the signal processing unit 2 by sending a control signal or the like to the signal processing unit 2 (period t1).

  Before each circuit sequentially processes an input signal, the signal processing unit 2 performs a preliminary operation by, for example, inputting a pseudo signal to an input signal line or the like in order to equalize operating conditions at the start of operation of each circuit. (Period t2). Accordingly, the operation conditions at the start of the operation of the circuit that processes the first input signal Input (1) and the circuits that process the input signal Input (2) and thereafter are the same, so that there is no difference between the circuits that operate sequentially. Signal processing can be performed.

  However, in the operation as the comparative example shown in FIG. 2, since the period for performing the preliminary operation is added to the initialization period and the signal processing period, the start of the signal processing for the input signal (period t3 to) is delayed. I have.

  FIG. 3 is a timing chart showing an operation of the signal processing device 1 as an embodiment. In the operation of the embodiment shown in FIG. 3, the signal processing unit 2 performs a preliminary operation in which the operation state of the second and subsequent circuits is almost the same as the operation state before the operation starts, and the initialization unit 3 performs the preliminary operation. This is performed until the initialization of the signal processing unit 2 is completed, and before the circuit that operates first starts operating. For example, the signal processing device 1 performs the initialization operation and the preliminary operation at the same time by the signal processing unit 2 performing signal processing using the state of the input signal line at the time of the initialization operation as a pseudo signal. Accordingly, the signal processing device 1 can make the operating conditions of each circuit substantially the same without delaying the start of the signal processing (period t3).

  Next, the photoelectric conversion element 10 as an example of the signal processing device according to the embodiment will be described. FIG. 4 is a block diagram illustrating a configuration example of the photoelectric conversion element 10 according to the embodiment. The photoelectric conversion element 10 is, for example, a CMOS color linear sensor of a collective exposure method, and includes a conversion processing unit 12, a timing control unit (Timing Generator: TG) 14, a parallel-serial conversion unit (PS) 16, and an LVDS 18.

  The conversion processing unit 12 includes a plurality of pixels 120 (described later with reference to FIG. 5) arranged in one direction (for example, the main scanning direction of the document) for each color of the received RGB light. Conversion is performed, and image data for each color is output in parallel as digital data in the main scanning direction.

  The timing control unit 14 is a control unit that controls operation timing and the like of the conversion processing unit 12 and the parallel-serial conversion unit 16. The parallel-serial conversion unit 16 converts the digital data output in parallel by the conversion processing unit 12 into serial data, and outputs the serial data to the LVDS 18. The LVDS 18 converts the serial data input from the parallel-to-serial conversion unit 16 into a low-voltage differential serial signal, and outputs it to a subsequent stage.

  FIG. 5 is a diagram illustrating a configuration example of the conversion processing unit 12 illustrated in FIG. As shown in FIG. 5, in the conversion processing unit 12, n pixels 120 are arranged in the main scanning direction, and a total of three lines are arranged in the sub-scanning direction for each color of Red, Green, and Blue. The conversion processing unit 12 also includes other control signals and the like.

  All the pixels 120 accumulate charges in a common exposure time, convert the charges into a voltage, and transfer pixel signals to an analog memory (storage capacitor) 122 via the switch elements SL and CS_ * (*: R / G / B). Hold. Hereinafter, a portion including the pixel 120, the switch elements SL, CS_ *, SW, and the analog memory 122 is referred to as one pixel unit that outputs a result of the photoelectric conversion. The pixel unit outputs the result of the photoelectric conversion by performing substantially the same operation sequentially.

  In the conversion processing unit 12, three pixel portions including, for example, three pixels 120 (in FIG. 5, three pixels of Red, Green, and Blue) form one column. Each pixel unit is connected to a PGA (Programmable Gain Amp) 124 via a common signal line Vsig for each column. The electric charge (pixel signal) accumulated in each analog memory 122 is read out (by time division) in the order of Red, Green, and Blue via the signal line Vsig for each column, and is input to the PGA 124. The PGA 124 amplifies the input signal based on the reference voltage Vrefa.

  Each PGA 124 is connected to an A / D converter (ADC) 126. The A / D converter 126 A / D converts the signal amplified by the PGA 124 based on the upper reference voltage Vrefp and the lower reference voltage Vrefn, and outputs the signal. Hereinafter, the PGA 124 and the A / D converter 126 provided for each column may be referred to as a signal processing unit. The signal processing unit processes a signal output from the pixel unit.

  Note that the timing control unit 14 performs control to initialize the voltage of the analog memory 122 and the signal line Vsig to a predetermined voltage VCR by controlling the switch element CR and the like.

  FIG. 6 is a timing chart illustrating a first operation example of the photoelectric conversion element 10. The photoelectric conversion element 10 stores the pixel signals from the respective pixels 120 in the respective analog memories 122 by simultaneously turning on the switch elements SL and CS_ * simultaneously during the period t1. Also, the photoelectric conversion element 10 initializes the signal line Vsig prior to subsequent signal reading by turning on the switch element CR at the same time. Since the signal line Vsig is connected to the initialization voltage VCR, the potential converges on the VCR.

  After transferring the pixel signal to the analog memory 122, the photoelectric conversion element 10 simultaneously turns off the switch element SL and the switch element CS_ * and turns on the switch element SW in the period t2. At this time, potential fluctuation occurs in the signal line Vsig due to switching noise or the like. If the switching element CR is not turned ON, this potential fluctuation is maintained as it is, and the voltage at the time of starting reading is shifted. Therefore, an error occurs in the voltage at the time of reading (Vr in FIG. 6). Therefore, the photoelectric conversion element 10 converges the potential of the signal line Vsig to VCR by turning on the switch element CR continuously from the period t1.

  As described above, in the first operation example of the photoelectric conversion element 10, the period t2 is a stable period of the switching noise. That is, it is necessary to allow time for the potential of the signal line Vsig before reading to converge to the VCR. When the potential of the signal line Vsig converges, the photoelectric conversion element 10 performs a preliminary operation in the period t3.

  In the period t3, for example, an invalid pixel signal in which the switch element CS_ * remains OFF is amplified by the PGA 124 and A / D converted by the A / D converter 126. Thereafter, in the photoelectric conversion element 10, the signal processing unit performs amplification and A / D conversion of the pixel signal by turning on the switch element CS_ *.

  As a result, the states immediately before the R, G, and B pixel signals are respectively input to the signal processing units during the periods t4 to t6 are made substantially the same, and the conditions of the fluctuation of the reference voltage Vrefa / p / n become substantially equal. However, in the first operation example of the photoelectric conversion element 10, since the period t3 as the preliminary operation period is provided, the one-line cycle when the photoelectric conversion element 10 reads an image is extended by the period t3.

  FIG. 7 is a timing chart illustrating a second operation example of the photoelectric conversion element 10. In the second operation example, the photoelectric conversion element 10 inputs the voltage of Vsig during the stable period of the switching noise in the period t2 to the PGA 124 as an invalid pixel signal and amplifies the voltage, and the A / D converter 126 performs A / D conversion. A preliminary operation for performing the conversion is being performed. In the preparatory operation, there is no problem even if the voltage input to the PGA 124 is converging to the VCR.

  As described above, in the second operation example of the photoelectric conversion element 10, the preparatory operation in the preparatory operation period (t3) provided in the first operation example is performed in the period t2, and the PGAs 124 and A are provided for each pixel unit. The processing performed by the / D converter 126 is prevented from being delayed, and the operating conditions are aligned for each pixel unit.

  FIG. 8 is a timing chart illustrating a third operation example of the photoelectric conversion element 10. In the second operation example, the photoelectric conversion element 10 continuously turns on the switch element CR during the preliminary operation period to initialize the voltage of the signal line Vsig. In the third operation example, the photoelectric conversion element 10 turns off the switch element CR immediately after the start of the period t2, and turns on the switch element CR within the period t2 at the same timing as the signal processing of each pixel signal.

  Thereby, in the photoelectric conversion element 10, the operation of the switch element (transistor) for initializing the pixel portion can be made uniform, and the conditions such as switching noise can be made uniform. That is, the operation conditions of each circuit can be made substantially the same without delaying the start of operation of each circuit of the photoelectric conversion element 10.

  FIG. 9 is a timing chart illustrating a fourth operation example of the photoelectric conversion element 10. When the convergence time of the initialization operation by the switch element CR is short due to the characteristics of the photoelectric conversion element 10, the period (t2) before the processing by the signal processing unit may be short. Therefore, even if the preliminary operation period is shortened within the range of the variation of the reference voltage Vrefa / p / n in which the state immediately before the pixel signals are input in the respective colors of R, G, and B during the period t4 to t6 is the same. Good.

  For example, when the A / D converter 126 is a cyclic A / D converter, the preliminary operation period is reduced by reducing the number of conversion bits, thereby reducing the number of cycles. The signal in the preliminary operation does not matter even if the number of conversion bits of the A / D converter 126 is small.

  FIG. 10 is a timing chart illustrating a fifth operation example of the photoelectric conversion element 10. In the photoelectric conversion element 10, in the fifth operation example, the signal processing unit performs a preliminary operation when each pixel signal is accumulated in the analog memory 122 in the period t1. When the influence of the switching noise on the signal line Vsig at the end of the period t1 is canceled by the switch element that is turned on and the switch element that is turned off, the potential fluctuation in the initialization operation is reduced.

  More specifically, since the switching noise caused by turning off the switch elements SL and CS_ * and the switching noise caused by turning on the switch element SW have opposite polarities, the transistor size and the transistor size of each switch element are set so that the switching noise is canceled. Gate voltage is set. When the potential fluctuation after the period t1 is reduced, the characteristics before the start of the reading are uniform in the period t4 / t5 / t6, and the writing operation and the preparatory operation are performed at the same time, so that the speed can be further increased.

  Next, a modified example of the conversion processing unit 12 will be described. FIG. 11 is a diagram illustrating a modification of the pixel unit included in the conversion processing unit 12. The modified example of the pixel portion has a configuration in which switch elements SG and SN are added to the above-described pixel portion. The switch element SG is provided between the analog memory 122 and GND. The switch element SN is provided between the analog memory 122 and the potential terminal Vn.

  The potential terminal Vn is separated from the power supply, GND or reference voltage of the signal processing unit, and is given a potential unrelated to the signal processing unit. The potential of the potential terminal Vn is such that a current flows when a pixel signal is written from the pixel portion to the analog memory 122.

  FIG. 12 is a timing chart illustrating an operation example of the photoelectric conversion element 10 including a modification of the conversion processing unit 12. The photoelectric conversion element 10 provided with the modification of the conversion processing unit 12 turns on the switch element SN and turns off the switch element SG at the time of writing in the period t1, and uses a potential (potential terminal Vn) irrelevant to the signal processing unit as a reference. I do.

  After completion of the writing, the photoelectric conversion element 10 reads the pixel signal from the analog memory 122 on the basis of the GND or the potential terminal Vn. In the operation example shown in FIG. 12, the photoelectric conversion element 10 switches the reference of the analog memory 122 to GND by turning on the switch element SG and turning off the switch element SN.

  Accordingly, the photoelectric conversion element 10 having the modification of the conversion processing unit 12 can prevent the noise of the signal processing unit at the time of the preliminary operation from being transmitted to the analog memory 122 via the GND, and therefore, the analog memory It is possible to prevent an error from occurring in the voltage held by 122.

  Next, an image forming apparatus including the image reading device according to the embodiment will be described. FIG. 13 is a diagram illustrating an outline of an image forming apparatus 50 including an image reading device 60 having the photoelectric conversion element 10. The image forming apparatus 50 is, for example, a copying machine or an MFP (Multifunction Peripheral) having the image reading device 60 and the image forming unit 70.

  The image reading device 60 includes, for example, the photoelectric conversion element 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 or the like output from the timing control unit (TG) 14. The LED 602 irradiates the document with light. The photoelectric conversion element 10 receives reflected light from a document in synchronization with a line synchronization signal or the like, and a plurality of pixel units generate electric charges to start accumulation. Then, the photoelectric conversion element 10 outputs image data to the image forming unit 70 after performing parallel-serial conversion or the like.

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

  The device processing unit 80 includes an LVDS 800, an image processing unit 802, and a CPU 804. The CPU 804 controls each unit configuring the image forming apparatus 50 such as the photoelectric conversion element 10. Further, the CPU 804 (or the timing control unit 14) controls each pixel unit to start generating electric charges according to the amount of received light substantially simultaneously.

  The photoelectric conversion element 10 outputs to the LVDS 800, for example, image data of an image read by the image reading device 60, a line synchronization signal, a transmission clock, and the like. 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.

REFERENCE SIGNS LIST 1 signal processing device 2 signal processing unit 3 initialization unit 10 photoelectric conversion element 12 conversion processing unit 14 timing control unit (control unit)
16 parallel-serial conversion unit 50 image forming device 60 image reading device 70 image forming unit 120 pixels 122 analog memory (storage capacity)
124 PGA
126 A / D converter

JP-A-2006-019055

Claims (9)

By multiple circuit performs successively the same operation, a signal processing unit for outputting a signal by performing processing on the input signal,
An initialization unit for initializing the signal processing unit;
Has,
The signal processing unit,
The preliminary operation consisting in the same operating state and the operating state before the circuit operating the second and subsequent starts operation, the initialization unit is up to finish initializing the signal processing unit, and operates initially A signal processing device that performs the operation before the circuit starts operating. A plurality of pixel unit for outputting a result of converting each photoelectric by performing the same operation successively,
A plurality of signal in the pixel portion is output performs signal processing operations for processing successively by the pixel unit basis, the same operating state and the operating state of before the pixel portion for operating the second and subsequent starts operating A preliminary processing, a signal processing unit that performs until each of the plurality of pixel units is initialized, and before the pixel unit that operates first starts operating.
A photoelectric conversion element comprising: The plurality of pixel units include:
It has storage capacitors for storing the results of photoelectric conversion as electric charges, respectively.
The photoelectric conversion element according to claim 2, further comprising: a control unit configured to control each of the plurality of pixel units to be initialized by transferring a charge stored in each of the storage capacitors to a signal line. The photoelectric conversion element according to claim 3, wherein a period of the preliminary operation is shorter than a period of the signal processing operation for each of the pixel units. The signal processing unit,
4. The preparatory operation is performed while the control unit transfers charges from the plurality of pixel units to the storage capacitors, and transfers the charges stored in the storage capacitors to the signal lines. Or the photoelectric conversion element according to 4. The control unit includes:
While the signal processing unit is performing the preliminary operation, electric charges from a plurality of the pixel units are supplied to each of the storage capacitors to which a potential separated from a power supply, GND, or a reference voltage of the signal processing unit is applied. The photoelectric conversion element according to any one of claims 3 to 5, wherein the photoelectric conversion element is transferred. An image reading apparatus comprising the photoelectric conversion element according to claim 2. An image reading device according to claim 7,
An image forming unit that forms an image based on an output of the image reading device. By multiple circuit performs successively the same operation, a step of initializing a signal processing unit for outputting a signal by performing processing on the input signal,
The preliminary operation of the circuit which operates the second or later becomes the same operating conditions and operation state before the start of the operation, and in the signal processing unit until after initializing, and first the circuit operating in the operation Steps to be performed before starting,
Control method including:

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