JP6733334B2 - Photoelectric conversion element, image reading apparatus, and image forming apparatus - Google Patents

Description

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

Conventionally, a CCD (Charge Coupled Device) has been used as a photoelectric conversion element in an image reading device such as a scanner, but in recent years, a CMOS linear sensor has attracted attention due to a demand for higher speed. A CMOS linear sensor is the same as a CCD in that incident light is photoelectrically converted by a photodiode, but it is different in that it performs charge-voltage conversion near a pixel and outputs it to the subsequent stage. Further, the CMOS linear sensor can incorporate an ADC (Analog to Digital Converter) and a high-speed logic circuit because the CMOS process can be used, and it can be said that the CMOS linear sensor is more advantageous than the CCD in terms of high speed.

However, when the scanner operates at high speed, not only the simple processing speed but also the charge accumulation time (line cycle) is required to be shortened. For example, in order to speed up the scanner, if the resolution is the same, it is necessary to increase the scanning speed per unit time, and therefore it is necessary to shorten the charge storage time. The amount of electric charge accumulated in a PD (Photo Diode) is determined by the irradiation light, but if the electric charge accumulation time is shortened, there is a problem that the sensitivity and S/N decrease. In order to compensate for the decrease in S/N in photoelectric conversion of PD, it is necessary to increase the amount of light, for example.

Further, in order to solve the above-mentioned problem, for example, in Patent Document 1, among the pixel signals of the previous frame held in the signal holding unit, the pixel signal of the same group and the same position as the pixel signal of the current frame, and the current frame There is disclosed a solid-state imaging device that includes an addition unit that adds the pixel signal of (1) and implements TDI (Time Delay Integration). TDI is known as a technique for achieving high sensitivity and high S/N.

However, in the conventional TDI technique, when the moving speed of the photoelectric conversion element with respect to the subject is changed from a constant value, the exposure position of each pixel to which the signal is added is shifted, and the S/N is reduced. There was a problem.

The present invention has been made in view of the above, and it is possible to prevent a decrease in S/N even when the moving speed relative to a subject is changed, and a photoelectric conversion element and an image. An object is to provide a reading device and an image forming apparatus.

In order to solve the above-mentioned problems and achieve the object, the present invention is a photoelectric conversion element that photoelectrically converts light received from a subject while being moved relative to the subject, and arranged in a moving direction. a plurality of light receiving elements that photoelectrically convert each color received from the subject is, a combining unit, wherein the plurality of light receiving elements to synthesize photoelectric conversion signals respectively, the light from the same position that put on the subject Control the timing at which the plurality of light receiving elements are exposed and the timing at which the combining section combines the signals so that the combining section combines the signals of the same color photoelectrically converted by the plurality of light receiving elements at different times. And a control unit for controlling.

According to the present invention, it is possible to prevent the S/N from decreasing even when the moving speed relative to the subject is changed.

FIG. 1 is a configuration diagram illustrating a configuration example of an image forming apparatus according to an embodiment. FIG. 2 is a configuration diagram showing a configuration example of the image reading device and the ADF. FIG. 3 is a diagram showing a configuration example of the photoelectric conversion element. FIG. 4 is a diagram illustrating a plurality of photodiodes included in the photoelectric conversion element and the periphery thereof. FIG. 5 is a diagram illustrating a configuration example of the combining unit. FIG. 6 is a timing chart showing an operation example of the combining unit. FIG. 7 is a diagram conceptually showing the synthesis of signals performed by the synthesis unit when the image reading apparatus reads an image of the same size. FIG. 8 is a diagram conceptually showing the synthesis of signals when the image reading apparatus of the comparative example reads an image at a variable magnification. FIG. 9 is a timing chart showing an operation example of the synthesizing unit when the image reading apparatus reads an image with variable magnification. FIG. 10 is a diagram conceptually showing the synthesis of signals performed by the synthesis unit when the image reading apparatus reads a variable-magnification image. FIG. 11: is a figure which shows the 1st modification of a synthetic|combination part. FIG. 12 is a timing chart showing an operation example of the synthesizing unit when the signal of the pixel is delayed. FIG. 13 is a diagram conceptually showing the synthesis of signals performed by the synthesis unit when delaying the pixel signals. FIG. 14 is a diagram showing a second modification of the combining unit. FIG. 15 is a timing chart showing an operation example of the synthesizing unit when the signal of the pixel is delayed. FIG. 16 is a diagram showing a third modification of the combining unit. FIG. 17 is a timing chart showing an operation example of the synthesizing unit when the signal of the pixel is delayed. FIG. 18 is a diagram showing a fourth modification of the combining unit. FIG. 19 is a timing chart showing the operation of the fifth modification of the combining unit when delaying the pixel signal. FIG. 20 is a diagram schematically showing different states in which the photoelectric conversion element is mounted on the substrate.

An image forming apparatus according to an embodiment will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram illustrating a configuration example of an image forming apparatus 300 according to the embodiment. The image forming apparatus 300 is a digital copying machine having a paper feeding unit 303 and an image forming apparatus main body 304, and on which an image reading apparatus 100 and an automatic document feeder (ADF) 200 are mounted.

In the image forming apparatus main body 304, a tandem type image forming unit (image forming unit) 305, and a registration roller 308 that conveys the recording paper supplied from the paper feeding unit 303 via the conveying path 307 to the image forming unit 305. An optical writing device 309, a fixing/conveying unit 310, and a double-sided tray 311 are provided.

In the image forming unit 305, four photoconductor drums 312 corresponding to four color toners of Y, M, C and K are arranged in parallel. An image forming element including a charging device, a developing device 306, a transfer device, a cleaner, and a charge eliminator is arranged around each photoconductor drum 312.

Further, an intermediate transfer belt 313, which is stretched between a driving roller and a driven roller while being sandwiched by a nip between the transfer device and the photosensitive drum 312, is arranged.

The tandem-type image forming apparatus 300 configured as described above performs optical writing on the photoconductor drum 312 corresponding to each color of Y, M, C, and K, and the developing unit 306 develops for each toner of each color. Then, primary transfer is performed on the intermediate transfer belt 313 in the order of Y, M, C, and K, for example.

Then, the image forming apparatus 300 forms a full-color image on the recording paper by secondary-transferring the full-color image in which the four colors are superposed by the primary transfer onto the recording paper, fixing and discharging the paper. The image forming apparatus 300 also forms an image read by the image reading apparatus 100 on a recording sheet.

FIG. 2 is a configuration diagram showing a configuration example of the image reading apparatus 100 and the ADF 200. The image reading apparatus 100 is a scanner device installed in an image forming apparatus such as a digital copying machine, a digital multi-function peripheral, or a facsimile machine. Further, the image reading device 100 may be a single scanner device. Then, the image reading apparatus 100 illuminates a document, which is a subject (reading target), with light emitted from a light source, processes reflected light from the document on a signal received by a CMOS image sensor, and outputs image data of the document. Read.

Specifically, as shown in FIG. 2, the image reading apparatus 100 includes a contact glass 101 on which an original is placed, a first carriage 106 including a light source unit 102 for exposing the original, and a first reflection mirror 103. The second carriage 107 includes the second reflection mirror 104 and the third reflection mirror 105. The image reading apparatus 100 also corrects various distortions caused by a photoelectric conversion element (for example, a CMOS color linear image sensor) 400, a lens unit 108 for forming an image on the photoelectric conversion element 400, and a reading optical system. A reference white plate (white reference plate) 110 used for the above and a sheet-through reading slit 111 are also provided. The photoelectric conversion element 400 is mounted on the substrate 112.

The image reading apparatus 100 has an ADF 200 mounted on the top, and is connected via a hinge so that the ADF 200 can be opened and closed with respect to the contact glass 101.

The ADF 200 includes a document tray 221 as a document mounting table on which a document stack made up of a plurality of documents can be placed. The ADF 200 also includes a separating/feeding unit including a feeding roller 222 that separates the originals one by one from the original stack placed on the original tray 221 and automatically feeds the originals toward the sheet-through reading slit 111. ing. Further, the lower part of the ADF 200 is a pressure plate 223. The pressure plate 223 also has a function as a background plate when an image is read through the contact glass 101.

Then, in the scan mode in which the image reading apparatus 100 scans (scans) the image surface of the document to read the image of the document, the first carriage 106 and the second carriage 107 cause the stepping motor to move in the arrow A direction (sub-scanning direction). ) To scan the document. At this time, in order to keep the optical path length from the contact glass 101 to the photoelectric conversion element 400 constant, the second carriage 107 moves at half the speed of the first carriage 106.

At the same time, the image surface, which is the lower surface of the document set on the contact glass 101, is illuminated (exposed) by the light source unit 102 of the first carriage 106. Then, the reflected light image from the image surface is transferred to the photoelectric conversion element 400 via the first reflection mirror 103 of the first carriage 106, the second reflection mirror 104 and the third reflection mirror 105 of the second carriage 107, and the lens unit 108. The images are sequentially sent and imaged.

Then, a signal is output by photoelectric conversion of the photoelectric conversion element 400, and the output signal is converted into a digital signal. In this way, the image of the original is read and digital image data is obtained.

On the other hand, in the sheet through mode in which the original is automatically fed and the image of the original is read, the first carriage 106 and the second carriage 107 move to the lower side of the sheet through reading slit 111. After that, the document placed on the document tray 221 is automatically fed by the feeding roller 222 in the arrow B direction (sub-scanning direction), and the document is scanned at the position of the sheet-through reading slit 111.

At this time, the lower surface (image surface) of the automatically fed document is illuminated by the light source unit 102 of the first carriage 106. Therefore, the reflected light image from the image surface is transferred to the photoelectric conversion element 400 via the first reflection mirror 103 of the first carriage 106, the second reflection mirror 104 and the third reflection mirror 105 of the second carriage 107, and the lens unit 108. The images are sequentially sent and imaged. Then, a signal is output by photoelectric conversion of the photoelectric conversion element 400, and the output signal is converted into a digital signal. In this way, the image of the original is read and digital image data is obtained. The document whose image has been read is discharged to the discharge port.

It should be noted that the light reflected from the reference white plate 110 is converted into an analog signal by the photoelectric conversion element 400 by the illumination by the light source unit 102 started before the image reading in the scan mode or the sheet through mode, and then converted into a digital signal. It In this way, the reference white plate 110 is read, and the shading correction at the time of reading the image of the document is performed based on the read result (digital signal).

Further, when the ADF 200 is provided with a conveyor belt, even in the scan mode, the document can be automatically fed to the reading position on the contact glass 101 by the ADF 200 and the image of the document can be read.

Next, a structural example of the photoelectric conversion element 400 will be described with reference to FIGS. FIG. 3 is a diagram showing a configuration example of the photoelectric conversion element 400. FIG. 4 is a diagram illustrating a plurality of photodiodes (PD; light receiving elements) included in the photoelectric conversion element 400 and the periphery thereof. As shown in FIG. 3, the photoelectric conversion element 400 includes a first photoelectric conversion unit (PIX(R1)) 40a to a sixth photoelectric conversion unit (PIX(B2)) 40f, and a first pixel circuit row (PIXBLK(R1)). 42a to a sixth pixel circuit row (PIXBLK (B2)) 42f, an AMEM (analog memory: storage section) 44, an A/D conversion section (ADC) 46, and a TG (Timing Generator; control section) 48.

In the first photoelectric conversion unit 40a (FIG. 3), for example, about 7,000 photodiodes (PD1: FIG. 4) provided with an R filter and photoelectrically converted are arranged in one direction (main scanning direction). The second photoelectric conversion unit 40b is arranged in parallel to the first photoelectric conversion unit 40a, is provided with an R filter, and photodiodes (PD2: FIG. 4) that perform photoelectric conversion are arranged in one direction, for example, about 7,000 photodiodes. ing. As described above, in the photoelectric conversion element 400, photodiodes that receive one color (for example, R) are arranged in, for example, two rows. Hereinafter, for the same configuration (or signal) arranged in two rows such as photodiodes, a 1 is added to the end of the configuration included in the first column, and a 2 is added to the end of the configuration included in the second column. May be distinguished. The number of columns for each color is not limited to two.

For example, when the photoelectric conversion element 400 reads a subject at the same magnification in the image reading apparatus 100 shown in FIG. 2, each PD 2 reads the same position as the position on the subject read by the opposing PD 1 one line cycle before. As described above, the PDs 1 are arranged at intervals. That is, PD1 and PD2 shown in FIG. 4 receive light from the same position on the subject.

In the first pixel circuit row (PIXBLK(R1)) 42a (FIG. 3), for example, about 7,000 pixel circuits 500a (FIG. 4) transmitting signals photoelectrically converted by each PD1 are arranged in one direction (main scanning direction). Has been done. The pixel circuit 500a has a transfer transistor TQ1, a floating diffusion 1 (FD1), a reset transistor RQ1, and a source follower SF1. The transfer transistor TQ1 transfers charges. The reset transistor RQ1 resets FD1. The source follower SF1 buffers the signal and outputs it to the subsequent stage. Then, the pixel circuit 500a is configured to be capable of converting the charge (signal level) photoelectrically converted by the PD1 into a voltage and transmitting the voltage and transmitting the reset level obtained by resetting the FD1.

In the second pixel circuit row (PIXBLK(R2)) 42b (FIG. 3), for example, about 7,000 pixel circuits 500b (FIG. 4) transmitting the signals photoelectrically converted by each PD 2 are arranged in one direction (main scanning direction). Has been done. The pixel circuit 500b has a transfer transistor TQ2, a floating diffusion 2 (FD2), a reset transistor RQ2, and a source follower SF2. The transfer transistor TQ2 transfers charges. The reset transistor RQ2 resets the FD2. The source follower SF2 buffers the signal and outputs it to the subsequent stage. Then, the pixel circuit 500b is capable of converting the charge (signal level) photoelectrically converted by the PD2 into a voltage and transmitting the voltage and transmitting the reset level in which the FD2 is reset.

Here, the PD 1 and the pixel circuit 500a illustrated in FIG. 4 constitute a pixel 50a that photoelectrically converts R light. Further, the PD 2 and the pixel circuit 500b shown in FIG. 4 constitute a pixel 50b that photoelectrically converts the R light. Further, the pixel 50a may be referred to as R1 as one pixel provided in the photoelectric conversion element 400 and photoelectrically converting R light. Further, the pixel 50b may be referred to as R2, which is one pixel included in the photoelectric conversion element 400 and photoelectrically converting the R light. That is, in the photoelectric conversion element 400, the first photoelectric conversion unit (PIX(R1)) 40a and the second photoelectric conversion unit (PIX(R2)) 40b each have about 7,000 pixels R1 that photoelectrically convert R light. Has R2. The signals output by the pixels R1 and R2 are PIXOUT_R1 and PIXOUT_R2, respectively.

In the AMEM (analog memory) 44, for example, about 7,000 synthesis units 440 are arranged in one direction (main scanning direction). FIG. 5 is a diagram showing a configuration example of the combining unit 440. The combining unit 440 includes transistors (switches) WS1, WS2, RDS_R1, RDS_R2, and TD, capacitors Csr1, Csr2 (holding unit), Cxsr1 (replacement holding unit), and a buffer 441 for light received by the photoelectric conversion element 400. It has for each color (R, G, B) and holds and combines signals.

The capacitors (holding units) Csr1 and Csr2 are analog memories for signal level, and a signal is written and held via the transistor WS1 or WS2 (common to RGB). For example, the capacitor Csr1 that holds the signal of PIXOUT_R1 is connected to the transistor TD and the buffer 441, and the capacitor Cxsr1 is connected to the output side of the buffer 441.

The capacitance Cxsr1 is for delaying the signal of the pixel R1, and here it causes a delay corresponding to the time required to read one line of the image. When the TD signal (common to RGB) is turned on, the signal is transferred from the capacitor Csr1 to the capacitor Cxsr1.

A signal held by each of the capacitors Cxsr1 and Csr2, that is, a signal of the pixel R1 delayed by one line with respect to the pixel R2 (a signal of the pixel R1 one line before) and a signal of the pixel R2 are a transistor RDS_R1 serving as a read switch. It is sequentially read out to the subsequent stage via RDS_R2. At this time, the transistors RDS_R1 and RDS_R2 are simultaneously turned on, so that the signals of the pixels R1 and R2 are averaged and output to the subsequent stage.

In this way, the synthesizing unit 440 averages the signals at the read positions (optical signals obtained by reading the same position on the subject) by delaying the signals. In FIG. 5, the case where the signal of the pixel R1 is delayed with respect to the pixel R2 is shown as an example, but when the signal of the pixel R2 is delayed with respect to the pixel R1, the configuration is reversed. .. Further, the combining unit 440 is not limited to delaying the signal by one line, and may further be provided with a capacitance so as to delay the signal by two lines or more.

Further, although FIG. 5 illustrates an example in which the capacitors Csr1 and Csr2 are provided in parallel, the invention is not limited to this. For example, the capacitors Csr1 and Csr2 may be provided in series. That is, the synthesizing unit 440 holds the signal and performs averaging or addition (integration) of the signal. Here, averaging, adding, or integrating signals is sometimes referred to as synthesis as one form of TDI.

The third photoelectric conversion unit (PIX(G1)) 40c and the fifth photoelectric conversion unit (PIX(B1)) 40e (FIG. 3) are the first except that the provided filters are G and B, respectively. The photoelectric conversion unit (PIX(R1)) 40a has the same configuration. The fourth photoelectric conversion unit (PIX(G2)) 40d and the sixth photoelectric conversion unit (PIX(B2)) 40f (FIG. 3) are the second except that the filters provided are G and B, respectively. The photoelectric conversion unit (PIX(R2)) 40b has the same configuration. That is, each of the first photoelectric conversion unit (PIX(R1)) 40a to the sixth photoelectric conversion unit (PIX(B2)) 40f is a pixel column.

The third pixel circuit row (PIXBLK(G1)) 42c and the fifth pixel circuit row (PIXBLK(B1)) 42e are configured similarly to the first pixel circuit row (PIXBLK(R1)) 42a. The fourth pixel circuit row (PIXBLK(G2)) 42d and the fifth pixel circuit row (PIXBLK(B2)) 42f have the same configuration as the second pixel circuit row (PIXBLK(R2)) 42b.

That is, the photoelectric conversion element 400 has about 7,000 pixels G1 and G2 that photoelectrically convert G light, and about 7,000 pixels B1 and B2 that photoelectrically convert B light, respectively. Here, the signals output from the pixels G1 and G2 are PIXOUT_G1 and PIXOUT_G2, respectively, and the signals output from the pixels B1 and B2 are PIXOUT_B1 and PIXOUT_B2, respectively. Further, the photoelectric conversion element 400 includes six pixels R1, R2, G1, G2, B1, and B2 that receive light from the same position in the subject in one column, and a combining unit 440 is provided for each column. It is configured (see FIGS. 4 and 5).

The ADC 46 (FIG. 3) has, for example, about 7,000 A/D converters arranged in one direction (main scanning direction). Each A/D converter A/D converts the signals output by the pixels R1, R2, G1, G2, B1, and B2 for each column. A TG (Timing Generator; control unit) 48 controls the operation timing of each unit constituting the photoelectric conversion element 400. For example, in the TG 48, the timing at which a plurality of PDs are exposed so that the signals are photoelectrically converted by the plurality of PDs at different times from the subject and the signals are photoelectrically converted by the plurality of PDs. Control the timing at which signals are combined. That is, the TG 48 performs control so that the photoelectric conversion element 400 realizes the TDI function.

Note that when the photoelectric conversion element 400 outputs a reset level (reference signal) and a signal level (signal), a CDS (Correlated Double Sampling) circuit provided in a subsequent stage calculates a difference between the reset level and the signal level. Output. When the photoelectric conversion element 400 outputs only the signal level, the CDS circuit may not be provided.

Next, an operation example when the photoelectric conversion element 400 performs signal combination as one form of TDI will be described. The TDI is mainly used in a linear sensor and is a method of photoelectrically converting (reading) reflected light from the same subject in a plurality of pixel rows and adding (integrating) the results. It is also possible to achieve high sensitivity and high S/N.

However, it is important to read the same position on a subject with a plurality of pixel rows. For example, in a CCD, the same reading speed of the subject and the transfer speed of transferring the accumulated charge to the next line are used to read the same subject. And the addition of electric charge is realized. Charges added at this time are called "time delay integration" because delayed charges are added.

On the other hand, while the CCD sequentially transfers the charges to the pixel row in the subsequent stage and adds the charges, the CMOS sensor converts the charges into a voltage in the vicinity of the pixels, so that the TDI method like the CCD is adopted. I can't. Therefore, the TDI of the CMOS sensor includes a storage unit (for example, an analog memory) that stores the read charges.

FIG. 6 is a timing chart showing an operation example of the combining unit 440. Here, the pixel R1 and the pixel R2 will be described as targets. First, when the transistors WS1 and WS2 are turned on, signals are held in the capacitors Csr1 and Csr2. Next, the transistors RDS_R1 and RDS_R2 are turned on. For the pixel R1, the signal held in the capacitor Cxsr1 is read, and for the pixel R2, the signal held in the capacitor Csr2 is read.

Here, since the transistors RDS_R1 and RDS_R2 are simultaneously turned on, the signals not connected to the subsequent stages are averaged.

On the other hand, when the transistor WS1 is turned on, the signal held in the capacitor Csr1 is transferred to the capacitor Cxsr1 via the buffer 441 when the transistor TD is turned on (actually holds the same voltage level as the capacitor Csr1). ..

Next, the signal held by the capacitor Cxsr1 is read at the timing when the transistor RDS_R1 is turned on. That is, the period from the transfer of the signal from the capacitor Csr1 to the capacitor Cxsr1 and the reading of the signal is a delay period, and here, a delay of approximately one line is generated.

Note that the operations of the transistors WS1, WS2, and TD for the pixels G1, G2, B1, and B2 are the same as those of the pixels R1 and R2, and the signal averaging timing and the transistor RDS_*1, The difference is that the timings read by RDS_*2 are time-series processing (* indicates R, G, or B).

FIG. 7 is a diagram conceptually showing the synthesis (averaging) of signals performed by the synthesis unit 440 when the image reading apparatus 100 reads an image of the same size. When the resolution when the image reading apparatus 100 reads an image at the same magnification is 600 dpi, one line cycle (LSYNC cycle) corresponds to 1 dot (line). Here, a case will be described as an example where the pattern of the document differs from line to line for pattern 600, pattern 0, pattern 2,... 600 dpi. Hereinafter, the operation of reading the image by the pixel R1 may be referred to as PIX(R1), and the operation of reading the image by the pixel R2 may be referred to as PIX(R2).

When the image reading apparatus 100 moves the photoelectric conversion element 400 at a speed V and scans a document (subject) in the order of PIX(R1) and PIX(R2), pattern 0, pattern 1, pattern 2...・Exposure is performed in the order of and patterns are sequentially read. Further, since the pattern one line after is read in PIX(R2) at the same time, pattern 0 is read in PIX(R2) at the timing of reading pattern 1 in PIX(R1). That is, the PIX (R2) is read one line later than the PIX (R1).

In this case, the TG 48 delays the signal of PIX (R1) that is read first by one line and performs control so as to take an average with PIX (R2) to enable the synthesis of the signal as TDI. At this time, since PIX(R1) and PIX(R2) read the same position on the subject, the signal after averaging naturally becomes a signal at the same position on the subject.

In FIG. 7, PIX(R1+R2) is expressed as “0&0”, but this is a signal obtained by synthesizing (averaging) “0” read by PIX(R1) and PIX(R2). Is the meaning.

FIG. 8 is a diagram conceptually showing the synthesis (averaging) of signals when the image reading apparatus (scanner) of the comparative example reads a variable-magnification (50% reduction) image. Although the operation at the same magnification is shown in FIG. 7, the scanner has a variable magnification operation for changing the magnification in the sub-scanning direction by changing the scan speed. FIG. 8 shows this scaling operation. FIG. 8 shows the case where the magnification is reduced to 50%, and the point different from the condition shown in FIG. 7 is that the scan speed is changed from V to 2V to double.

When the resolution at the same magnification is 600 dpi, one line cycle (LSYNC cycle) corresponds to 2 dots (line). This is because assuming that the pattern of the original is the same as that of FIG. 7, since PIX (R1) and PIX (R2) are scanned in this order at a speed of 2 V, pattern 0, pattern 1, and pattern 2 in PIX (R1). And pattern 3... and two patterns are read at once.

However, the PIX (R2) is arranged so as to be displaced by one line (one pattern) from the PIX (R2) when the photoelectric conversion element 400 reads an image at the same size, so that the pattern before one is used. Start with and read two patterns at a time. That is, at the timing when the pattern 2 and the pattern 3 are read together by the PIX (R1), the pattern 1 and the pattern 2 are read together by the PIX (R2).

In this case, even if the signal of PIX (R1) read out first is delayed by one line, PIX (R1) and PIX (R2) read the combined signals of pattern N and pattern N+1 and pattern N-1 and pattern N, respectively. Therefore, the different signals are averaged. This is because the scanning speed and the exposure timing (LSYNC timing) change due to the magnification change, so that the reading position (exposure position) is different between PIX (R1) and PIX (R2). That is, there is a problem that the resolution is deteriorated by performing the combining operation at the time of changing the magnification. In the example shown in FIG. 8, the scaling in the reduction direction is taken as an example, but the same problem occurs in the scaling in the expansion direction.

FIG. 9 is a timing chart showing an operation example of the synthesizing unit 440 when the image reading apparatus 100 reads a variable-magnification (50% reduction) image. As shown in FIG. 9, the TG 48 controls the exposure timing so that the PIX (R1) and the PIX (R2) are at the same exposure position with respect to the subject during zooming. The example shown in FIG. 9 is different from the example shown in FIG. 6 in that the LSYNCs on the PIX1 side (delayed pixel) and the PIX2 side (non-delayed pixel) are separate and the exposure timings of each are shifted. different. Specifically, the transistor WS1 is shifted by 0.5 line with respect to the transistor WS2 to operate.

FIG. 10 is a diagram conceptually showing the synthesis (averaging) of signals performed by the synthesis unit 440 when the image reading apparatus 100 reads a variable-magnification (50% reduction) image. The example shown in FIG. 10 differs from the comparative example shown in FIG. 8 in that the exposure timing (LSYNC:R1) of PIX (R1) to be read first is shifted by 0.5 line with respect to PIX (R2). The difference is.

In this case, in PIX (R1), the position advanced by 0.5 line (1/2 of the LSYNC cycle) in scanning is read after the line in FIG. That is, 0.5 lines after the timing of reading the pattern 0 and the pattern 1 in the PIX (R1) of FIG. 8, the pattern 1 and the pattern 2 which are positions advanced by the scan (one pattern ahead) are read. .. Therefore, the PIX (R1) whose exposure timing is shifted by 0.5 line reads the same pattern 1 and pattern 2 as the PIX (R2) together.

In this way, since PIX(R1) and PIX(R2) have the same exposure position, the same signal is averaged. That is, the image reading apparatus 100 can prevent the resolution from deteriorating even when the signal combining operation is performed at the time of changing the magnification. The PIX (R1) read first is already delayed by 0.5 line due to the shift of the exposure timing, and therefore the signal may be delayed (retained) by 0.5 line in the combining unit 440.

It should be noted that in the above-described scaling, the difference in the physical exposure positions of PIX (R1) and PIX (R2) (1 line) is reduced to less than 1 line by the scaling operation (0.5 line). It can be considered that the original line is restored by adding +0.5 line by changing the exposure timing.

FIG. 11 is a diagram showing a first modification (combining unit 440a) of the combining unit 440. When the image reading apparatus 100 reads a document in the order of R→G→B in the scan mode, the order of reading the document (relative moving direction) is reversed in the sheet-through mode to be in the order of B→G→R. At this time, the relationship of the pixels to be delayed by the image reading device 100 is also reversed. The synthesizing unit 440a is also capable of reversing the relationship of the pixels to be delayed, so that the signals can be correctly synthesized even when the image reading apparatus 100 is in the scan mode or the sheet through mode. Is configurable.

As illustrated in FIG. 11, the combining unit 440a photoelectrically converts the transistors (switches) WS1, WS2, RDS_R1, RDS_R2, RDS_R, TD1, and TD2, the capacitors Csr1, Csr2, Cxsr (replacement holding unit), and the buffer 441. The element 400 has each color of light received (R, G, B) and holds and combines signals.

In the example shown in FIG. 5, the only pixel that can be delayed is R1, but in the combining unit 440a, the transistor TD2 is added to the input side of the buffer 441, and the signal of the pixel R2 is also delayed. ing. Further, the combining unit 440a is added with a transistor RDS_R1 that connects the signal of the capacitor Csr1 to the read line (RDOUT) so that the signal of the pixel R1 that is not delayed can be output.

Further, although RDS_R1 shown in FIG. 5 is a signal for controlling the reading of the delay, in the combining unit 440a, the reading of the signal that is not delayed is controlled by RDS_R1 or RDS_R2, and the delay signal (pixel R1 or pixel R2 (Either signal is delayed), the read is controlled by RDS_R. The same applies to the pixel G1, the pixel G2, the pixel B1, and the pixel B2.

FIG. 12 is a timing chart showing an operation example of the combining unit 440a when the signal of the pixel R2 is delayed. In the case of delaying the pixel R2 (sheet through mode), the relationship opposite to that of the pixel R1 and the pixel R2 shown in FIG. 9 is obtained. Further, since the pixel R1 is not delayed, the TG 48 delays the signal of the pixel R2 by holding the signal of the pixel R2 in the capacitor Cxsr without turning on the transistor TD1. When reading a signal, the transistors RDS_R and RDS_R1 are simultaneously turned on. The same applies to the pixel G1, the pixel G2, the pixel B1, and the pixel B2.

In the case of delaying the pixel R1 (for example, scan mode), only the transistor TD1 is turned on to delay the signal of the pixel R1, and when reading the signal, the transistors RDS_R and RDS_R2 are simultaneously turned on.

FIG. 13 is a diagram conceptually showing the synthesis (averaging) of signals performed by the synthesis unit 440a when delaying the signal of the pixel R2. In the example shown in FIG. 13, the relationship between the pixel R1 and the pixel R2 is reversed with respect to the example shown in FIG. For example, when the reading method (scan mode or sheet through mode) shown in FIG. 10 is changed, the reading order of RGB is reversed and the relationship between the pixel R1 and the pixel R2 is also reversed. Therefore, in FIG. 13, the relationship between the pixel R1 and the pixel R2 is replaced with that in FIG. Specifically, the synthesizing unit 440a synthesizes (averages) the signal obtained by delaying the pixel R2 and the signal of the pixel R1 since the pixel R2 reads the document first.

As described above, the image reading apparatus 100 is configured such that the pixels to be delayed are selectable, so that the combining unit 440a can correctly combine the signals even if the reading method (scan mode or sheet through mode) is changed. it can.

FIG. 14 is a diagram illustrating a second modified example (combining unit 440b) of the combining unit 440. As shown in FIG. 14, in the combining unit 440b, the photoelectric conversion element 400 receives the transistors (switches) WS1a, WS1b, WS2a, WS2b, RDS_R1, RDS_R2, RDS_R, and the capacitors Csr1, Csr2, Cxsr (alternative holding unit). It holds for each color of light (R, G, B) to be used, and holds and combines signals.

In the combining unit 440a shown in FIG. 11, the delay is realized by holding the signal in the capacitor Cxsr via the buffer 441. This is because the operation of transferring a signal to another capacitor is simply performed (when the capacitors are connected, the signal is attenuated and the sensitivity is changed). Here, the buffer 441 is required to have an accuracy of faithfully reproducing the signal level, and therefore the circuit scale tends to be relatively large.

In the synthesizing unit 440b illustrated in FIG. 14, the buffer 441 is unnecessary by alternately operating the capacitance Csr1 (or the capacitance Csr2) and the capacitance Cxsr. The combining unit 440b can directly hold the signals from the PIXOUT_R1 and PIXOUT_R2 in the capacitor Cxsr via the transistors WS1b and WS2b. The synthesizing unit 440b operates alternately each time the signal of the pixel to be delayed is updated, that is, every line. Similarly, the transistors RDS_R and RDS_R* operate alternately.

FIG. 15 is a timing chart showing an operation example of the combining unit 440b when the signal of the pixel R1 is delayed. In the example shown in FIG. 15, the image reading apparatus 100 performs a scaling (50% reduction) operation, and shows a case where the pixel R1 reads an image before the pixel R2.

In the example shown in FIG. 15, the pixel R1 reads an image like pattern 1 and pattern 2... Then, after 0.5 line, the pixel R2 reads the same image of pattern 1 and pattern 2... This is the same as the example shown in FIG. At this time, for the pixel R1 to be delayed, the transistors WS_1a and WS_1b are alternately turned on to switch the capacitance for holding the signal for each line.

In the example shown in FIG. 15, for example, the signals of pattern 1 and pattern 2 shown in FIG. 13 are held in the capacitor Csr1, and the signals of pattern 3 and pattern 4 to be read next are held in the capacitor Cxsr. In this way, the combining unit 440b alternately switches the capacity for holding the signal.

Further, the TG 48 only controls the transistor WS_2a for the pixel R2 which is not the delay target, and only holds the signal as in the example shown in FIG.

On the other hand, for the pixel R1, the TG 48 alternately turns on the transistors RDS_R1 and RDS_R to read the signals of the capacitors Csr1 and Cxsr alternately when reading the signal held in the capacitor. The TG 48 controls only the transistor RDS_R2 for the pixel R2, and only reads the signal from the capacitor Csr2 as in the example shown in FIG.

That is, when the signal of the Nth line is held in the capacitor Csr1 and read, the signal of the N+1th line is held and read in the capacitor Cxsr, and the capacitor Csr1 (or Csr2) and the capacitor Cxsr operate once every two lines. Will be done. At this time, since the capacitors Csr1 (or Csr2) and the capacitors Cxsr perform the function of holding and delaying the signal from the pixel with one capacitor, the transfer of the signal between the capacitors is eliminated and the buffer 441 is unnecessary.

When the pixel R2 reads the image before the pixel R1 (the operation condition corresponds to FIG. 12), the operations of the pixel R1 and the pixel R2 described above are reversed. The same applies to the pixel G1, the pixel G2, the pixel B1, and the pixel B2, only the timing is different.

FIG. 16 is a diagram illustrating a third modification example (synthesis unit 440c) of the synthesis unit 440. As illustrated in FIG. 16, the combining unit 440c includes transistors (switches) WS1, WS2, RDS_R1, RDS_R2 and capacitors Csr1, Csr2 for each color (R, G, B) of light received by the photoelectric conversion element 400. It holds and synthesizes signals. The synthesizing unit 440c has a smaller capacity (memory) that occupies an area in the chip, as compared with other modified examples, so that the simplification effect is large.

The synthesizing unit 440c is different from other modified examples in that the timing of synthesizing the signals and the timing of moving the signals from the pixels to the capacitors can be made different. That is, the synthesizing unit 440c does not need the capacitor Cxsr by performing the signal synthesizing (averaging) operation in the period in which the exposure timing is shifted. The combining unit 440c has a configuration in which the capacitive memory Cxsr, the transistors WS_R1b, WS_R2b, and RDS are deleted from the combining unit 440b.

FIG. 17 is a timing chart showing an operation example of the combining unit 440c when the signal of the pixel R1 is delayed. In the example shown in FIG. 17, the image reading apparatus 100 performs a scaling (50% reduction) operation, and shows a case where the pixel R1 reads an image before the pixel R2.

The example shown in FIG. 17 differs from the example shown in FIG. 15 in that signal combination (averaging) and read operation to the subsequent stage are separated. For example, regarding the pixels R1 and R2, it is the same that the signals are held in the capacitors Csr1 and Csr2 at the operation timings of the transistors WS1 and WS2. Since the capacitor Csr1 also has the function of delaying (in the case of reverse reading, the capacitor Csr2 has a function of delaying), the signal held by the capacitor Csr1 is held until the transistor RDS_R1 is turned on next and read. It is delayed by being done.

In the capacitors Csr1 and Csr2, the signals held by the transistors RDS_R1 and RDS_R2 being simultaneously turned on in the state where they are not connected to the subsequent stage are combined (averaged). The averaged signal is evenly distributed to the capacitors Csr1 and Csr2, and is read out to the subsequent stage by turning on only the transistor RDS_R2. Here, the TG 48 performs the signal averaging operation during the period (T period) generated by shifting the exposure timing, so that the averaging timing and the timing of moving the signal from the pixel to the capacitor overlap. I'm avoiding it. Here, the TG 48 averages the signals held by the capacitors Csr1 and Csr2 in a period until one of the capacitors Csr1 and Csr2 holding a signal holds a new signal, and then, for example, the capacitor Csr2 By reading out the signal held by, the timing of synthesizing the signals held by the capacitors Csr1 and Csr2 is controlled.

Note that FIG. 17 shows the respective timings of RGB, and the timings at which the signals are averaged and read out in the subsequent stage are RGB in time series operation. In addition, in the combining unit 440c, in order to average the signals, RDS_*1 and RDS_*2 are turned on at the same time in a state where the latter stage is not connected, but in addition to these, between the capacitors Csr1 and Csr2. Alternatively, a switch (addition switch) may be provided to electrically disconnect the read line from the capacitor, and averaging may be performed simultaneously in RGB.

It should be noted that the operation example in the case of the variable-magnification reading of the image reading apparatus 100 described above cannot be realized unless the exposure timing is shifted. Therefore, in the image reading apparatus 100, the exposure timing does not need to be originally shifted in the case of, for example, the same-magnification reading, but even in this case, the exposure timing may be shifted so that the influence on the image can be ignored. The image reading apparatus 100 may be provided with an exposure timing shift of, for example, about 1% of the line period when reading at the same size. That is, the image reading apparatus 100 can realize the above-described composition regardless of the zooming state.

FIG. 18 is a diagram showing a fourth modified example (combining unit 440d) of the combining unit 440. As illustrated in FIG. 18, the combining unit 440d photoelectrically converts the transistors (switches) WS1, WS2, WR1, WR2, RDS_R1, RDS_R2, RDR_R1, RDR_R2, and the capacitors Csr1, Csr2, Crr1, and Crr2 (reference holding unit). The element 400 has each color of light received (R, G, B) and holds and combines signals.

When the image reading apparatus 100 performs CDS, the photoelectric conversion element 400 outputs two kinds of signals of a reset level and a signal level from a pixel, takes the difference between them in a post-stage circuit, and outputs an FPN (Fixed-Pattern-Noise). Remove. In this case, the photoelectric conversion element 400 needs to hold two types of signals, a reset level and a signal level. Therefore, the combining unit 440d includes capacitors Crr1 and Crr2 for holding a reset level signal, transistors WR1 and WR2 for holding a reset level signal, and a reset level signal so as to enable execution of CDS. Transistors RDR_R1 and RDR_R2 for reading are added.

FIG. 19 is a timing chart showing the operation of the fifth modification of the combining unit 440 when the signal of the pixel R1 is delayed. The fifth modification of the combining unit 440 reads out the capacitors Crr1 and Crr2 for holding a reset level signal, the transistors WR1 and WR2 for holding a reset level signal, and the reset level signal to the combining unit 440c. Therefore, the transistors RDR_R1 and RDR_R2 are added. In the example shown in FIG. 19, the operation at the time of scaling (50% reduction) is shown, and the case where the pixel R1 reads the image before the pixel R2 is shown.

In the example shown in FIG. 19, reset level holding/averaging/reading operations are added to the example shown in FIG. For example, when the signal is read from the pixel R1, the reset level is read before the signal level. At this time, the pixel is brought into a reset state or an equivalent state, outputs a reset level signal, and the transistor WR1 is turned on, whereby the reset level signal is held in the capacitor Crr1.

Next, the pixel R1 outputs a signal having a signal level, and the transistor WS1 is turned on, whereby the signal having a signal level is held in the capacitor Csr1. Here, although there is a delay of 0.5 line, similarly for the pixel R2, the signals of the reset level and the signal level of the pixel R2 are held in the capacitors Crr2 and Csr2, respectively.

Here, even when the signal is read, only the reset level read operation is added to the example shown in FIG. 17, and the transistors RDR_R1 and RDR_R2 or RDS_R1 and RDS_R2 are turned on at the same time. 17 is the same as FIG. 17 in that the signals are averaged by. The averaged signal is read out to the subsequent stage when the transistor RDR_R2 or RDS_R2 is turned on again. Here, the pixel R1 is read out after being delayed by 0.5 line as in the case of FIG. The same operation is sequentially performed on the pixel G1, the pixel G2, the pixel B1, and the pixel B2.

Next, the shift of the reading position due to the difference in the state where the photoelectric conversion element 400 is mounted on the substrate 112 will be described. FIG. 20 is a diagram schematically showing different states in which the photoelectric conversion element 400 is mounted on the substrate 112. For example, in the image reading apparatus 100, the exposure position shift occurs not only during zooming.

For example, as shown in FIG. 20, when the substrate 112 on which the photoelectric conversion element 400 is mounted has different inclinations, the exposure position is displaced. As shown in FIG. 20A, when the substrate 112 is arranged so that the pixel rows are orthogonal to the light incident direction, as shown in FIG. The line is shifted from the second photoelectric conversion unit 40b by one line, and the lines are shifted from each other by three lines. That is, the light that is imaged from the read document and is incident on the photoelectric conversion element 400 is also shifted by these lines.

Here, as shown in FIG. 20B, when the substrate 112 is tilted, the positional relationship of the shifts of one line and three lines shown in FIG. 3 changes. For example, when the substrate 112 is tilted by 30 degrees, the substantial positional deviation viewed from the incident light changes to 0.87 line/2.6 line, respectively. This is equivalent to scaling (reducing) to 87%. That is, the exposure position shifts even in the non-magnification non-magnification reading. Therefore, the image reading apparatus 100 may change the exposure timing according to the reading position shift amount, instead of whether or not the variable magnification reading is performed. The above-described composition is used not only in the case of variable-magnification reading, but also in the case where the resolution can be changed. Although the tilt of the substrate 112 (photoelectric conversion element 400) is described as an example in FIG. 20, a similar shift may occur due to the tilt (eccentricity) of the condenser lens or the reflection mirror.

40a First photoelectric conversion unit (PIX (R1))
40b Second photoelectric conversion unit (PIX (R2))
40c Third photoelectric conversion unit (PIX (G1))
40d Fourth photoelectric conversion unit (PIX (G2))
40e Fifth photoelectric conversion unit (PIX (B1))
40f 6th photoelectric conversion unit (PIX (B2))
44 AMEM (analog memory: storage unit)
48 TG (Timing Generator: control unit)
100 image reading device 112 substrate 200 automatic document feeder (ADF)
300 image forming apparatus 305 image forming unit (image forming unit)
400 Photoelectric conversion element 440, 440a to 440d Synthesis section PD Photodiode (light receiving element)
Csr1, Csr2 capacity (holding part)
Cxsr, Cxsr1 capacity (alternative holding unit)
Crr1, Crr2 capacity (reference holding part)

Patent No. 5594362

Claims (9)

A photoelectric conversion element that photoelectrically converts light received from the subject while being moved relative to the subject,
A plurality of light receiving elements arranged in the moving direction and photoelectrically converting light received from the subject for each color ;
A synthesizing unit for synthesizing the photoelectrically converted signals of the plurality of light receiving elements,
Of the same color signals obtained by photoelectric conversion of the light to the plurality of light receiving elements different times from the same position that put on the subject so that the synthetic part is synthesized, the timing at which the plurality of light receiving elements are exposed, A control unit that controls the timing at which the combining unit combines the signals;
A photoelectric conversion element comprising: The synthesizing unit,
Each of the plurality of light receiving elements has a plurality of holding portions that respectively hold a photoelectrically converted signal,
The control unit is
The timing of exposing each of the plurality of light receiving elements is controlled to be shifted according to the moving speed, and the timing of combining the signals held by each of the plurality of holding units is controlled. Photoelectric conversion element. The control unit is
The synthesizing unit delays the signal by delaying the exposure timing of at least one of the selected plurality of light receiving elements and delaying the timing of reading out the selected at least one of the signals held by each of the plurality of holding units. The photoelectric conversion element according to claim 2, wherein the timing of combining is controlled. A signal photoelectrically converted by any one of the plurality of light receiving elements, further comprising an alternative holding unit capable of holding in place of any of the plurality of holding units,
The control unit is
Alternately holding one of the plurality of holding units and the alternative holding unit of the signals photoelectrically converted by any of the plurality of light receiving elements, and controlling the timing at which the combining unit combines the signals. The photoelectric conversion element according to claim 2 or 3. The control unit is
Any of the plurality of holding units after averaging the signals held by the plurality of holding units in a period until one of the plurality of holding units holding a signal holds a new signal The photoelectric conversion element according to claim 2, wherein the timing of combining the signals held by each of the plurality of holding units is controlled by reading the signal held by the storage unit. The synthesizing unit,
For each of the plurality of light receiving elements, a plurality of reference holding units for holding a reference signal serving as a reference of a photoelectrically converted signal,
The control unit is
The photoelectric conversion element according to any one of claims 2 to 5, wherein the timing of synthesizing the reference signals held by each of the plurality of reference holding units is controlled. An image reading apparatus comprising the photoelectric conversion element according to claim 1. By the light receiving element in a straight direction orthogonal to the moving direction are arranged the photoelectric conversion elements, by the relative scanning of the object, an image reading apparatus for reading the object,
The control unit is
The image according to claim 7, wherein a timing at which the plurality of light receiving elements are exposed and a timing at which the synthesizing unit synthesizes signals are controlled according to a reading scaling ratio and a reading resolution for reading the subject. Reader. An image reading apparatus according to claim 7 or 8,
An image forming unit that forms an image based on image data read by the image reading device;
An image forming apparatus comprising:

Images