JP2013102321A - Image reader and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid occurrence of a linearity difference.SOLUTION: A TG (timing generator) 40 includes a plurality of phase selectors 42 for selecting an arbitrary rise edge and a fall edge from timing of a multilayer clock generated by a multilayer clock generator 41 and outputting respective driving signals of the arbitrary phase. The phases of the respective driving signals can be set from a control section 70 and the phases required for the respective driving signals can be set. Thus, the phase of sample hold timing of respective analog signals by sample-and-hold circuits 12 an 22 on an F side and an L side (a plurality of ch) can be adjusted. Consequently, the control section 70 can adjust the sample-and-hold timing of the respective analog signals with the TG 40 so that the levels of the respective digital signals from A/D converters 14 on the F side and the L side are matched.

Description

  The present invention relates to an image reading apparatus and an image forming apparatus equipped with the image reading apparatus.

In an image reading device that reads an original image by converting an analog signal from a CCD (Charge Coupled Device) image sensor into a digital signal, the analog signal is sampled and held by a sample hold circuit and then converted to a digital signal by an A / D converter Is done.
For analog signals, it is necessary to sample and hold an effective signal area for each pixel. However, in recent years, the frequency of the signal may have increased, and the sample and hold timing may shift depending on the delay variation of the drive signal. There is.

When the sample hold timing is shifted, there is a problem that the signal level to be held is different from the normal value.
As a method for adjusting the sample and hold timing, a method for adjusting to the sample and hold timing at which an optimum image is obtained by acquiring and comparing images at the sample and hold timings of a plurality of phases is already known.
For example, in Patent Document 1, in order to adjust the sample hold timing so as not to be incorrect, the sample hold is performed based on a plurality of digital signals output from the A / D converter (ADC) at each sample hold timing. A configuration for adjusting the phase of timing is disclosed.

  On the other hand, as an image reading apparatus, a CCD image sensor that outputs analog signals of a plurality of systems (hereinafter also referred to as “multiple channels (channels)”) and a plurality of analog channels from the CCD image sensor for high-speed image reading. A multi-channel sample-and-hold circuit that samples and holds a signal, and a multi-channel A / D converter that quantizes a plurality of channels of analog signals from the multi-channel sample-and-hold circuit and converts them into digital signals Things are also on the market.

However, in such a conventional image reading apparatus, the following problem occurs even if the above-described conventional method for adjusting the sample hold timing is used. That is, even if the sample and hold timings by the multiple channel sample and hold circuits are individually adjusted, the sample and hold timings do not always coincide with each other, and multiple channels of digital signals (image data) from the multiple channels of A / D converters are not necessarily matched. The levels of do not match and a linearity difference occurs.
The present invention has been made in view of the above points, and an object thereof is to avoid the occurrence of a linearity difference.

  The present invention converts reflected light from an object into an analog signal, divides the region into a plurality of regions and outputs a plurality of analog signals, and samples a plurality of analog signals from the image sensor. A plurality of systems of sample and hold circuits that hold and output, a plurality of systems of A / D converters that quantize and convert a plurality of systems of analog signals from the plurality of systems of sample and hold circuits into digital signals, and the image sensor And a plurality of systems of sample-and-hold circuits and a timing generator for generating a plurality of systems of A / D converter drive signals, in order to achieve the above object, It is characterized by that.

  That is, the timing generator is capable of adjusting the phase of the sample and hold timing of the analog signals of the plurality of systems by the sample and hold circuits of the plurality of systems, and a plurality of digital signals from the A / D converters of the plurality of systems. Adjusting means for adjusting the sample and hold timing of the analog signals of the plurality of systems by the timing generator so that the levels of the signals coincide with each other.

  According to the image reading apparatus of the present invention, since the levels of the digital signals of the plurality of systems from the A / D converters of the plurality of systems match, the occurrence of the linearity difference can be avoided.

1 is an overall configuration diagram illustrating a configuration example of a mechanism unit of an image reading apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration example of a signal processing unit included in the image reading apparatus 100 illustrated in FIG. 1 together with a control unit and a memory. FIG. 3 is a timing chart showing an example of the relationship between the input timing of a sample hold signal (SHD) from the TG 40 of FIG. 2 and the input / output of the sample hold circuits 12, 22. FIG. 3 is a timing diagram for explaining an operation when the phase of a sample hold signal (SHD) output from the TG 40 of FIG. 2 is changed. It is a flowchart which shows an example of adjustment of the sample hold signal (SHD) in the image reading apparatus 100 provided with the signal processing part shown in FIG.

FIG. 2 is a diagram for illustrating calculation of an average value of image levels in the vicinity of the boundary between the F side and the L side while showing the image level in the main scanning direction of the image data read from the reference white plate 110 in FIG. 1. It is a block diagram which shows the other structural example of the signal processing part with which the image reading apparatus of FIG. 1 is provided with the control part and the memory. It is a flowchart which shows an example of adjustment of SHD in the image reading apparatus 100 provided with the signal processing part shown in FIG. It is a whole block diagram which shows the structural example of the mechanism part of the image forming apparatus which is 2nd Embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention will be described.
In the following embodiments, a CCD image sensor that converts reflected light from a document or a reference white plate as an object into an analog signal, divides the region into a plurality of regions, and outputs a plurality of channels (a plurality of systems) of analog signals; A plurality of channels of sample and hold circuits that sample and hold a plurality of channels of analog signals from the image sensor, and a plurality of channels that quantize and convert the plurality of channels of analog signals from the plurality of channels of sample and hold circuits into digital signals. An image reading apparatus having a ch A / D converter has the following characteristics.

That is, the sample and hold timing of the analog signals of the plurality of channels by the sample and hold circuit of the plurality of channels is adjusted so that the levels of the digital signals of the plurality of channels from the A / D converters of the plurality of channels match. At this time, the phase of the sample and hold signal to the sample and hold circuits of a plurality of channels is changed.
Therefore, the feature will be specifically described with reference to FIGS.

[First embodiment]
FIG. 1 is an overall configuration diagram showing a configuration example of a mechanism unit of an image reading apparatus according to a first embodiment of the present invention.

  The image reading apparatus 100 is a scanner device or a single scanner device mounted on an image forming apparatus such as a digital copying machine, a digital multifunction peripheral, or a facsimile machine, and includes an image signal processing unit described later. Then, the original that is the subject is illuminated by the irradiation light from the light source, the reflected light from the original is received by the CCD image sensor, converted into an image signal by the A / D converter, and image processing is performed. Data can be read. Since the image signal converted by the A / D converter is an analog signal, it is converted into a digital signal.

  As shown in FIG. 1, the image reading apparatus 100 includes a contact glass 101 which is a document glass on which a document is placed, a first carriage 106 including a light source 102 for document exposure and a first reflection mirror 103, and a second carriage. A second carriage 107 including a reflection mirror 104 and a third reflection mirror 105 is provided. Also, a CCD image sensor (hereinafter simply referred to as “CCD”) 109, a lens unit 108 for forming an image on the CCD 109, and a reference white plate (“white reference plate” used for correcting various distortions caused by a reading optical system, etc. And a sheet-through reading slit 111.

An automatic document feeder (hereinafter abbreviated as “ADF”) 200 as an automatic document feeder is mounted on the upper part of the image reading apparatus 100 so that the ADF 200 can be opened and closed with respect to the contact glass 101. Are connected via a hinge or the like (not shown).
The ADF 200 includes a document tray 201 as a document placing table on which a document bundle composed of a plurality of documents can be placed. In addition, separation / feeding means including a feeding roller 202 that separates documents one by one from a bundle of documents placed on the document tray 201 and automatically feeds them toward the sheet-through reading slit 111 is also provided.

  In the image reading apparatus 100 configured as described above, in the scan mode in which the image surface of the document is scanned (scanned) to read the image of the document, the first carriage 106 and the second carriage 107 are indicated by arrows by a stepping motor (not shown). The document is scanned in the A direction (sub-scanning direction). At this time, the second carriage 107 moves at a half speed of the first carriage 106 in order to keep the optical path length from the contact glass 101 to the CCD 109 constant.

  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 102 of the first carriage 106. Then, the reflected light image from the image plane is sequentially sent to the CCD 109 via the first reflecting mirror 103 of the first carriage 106, the second reflecting mirror 104 and the third reflecting mirror 105 of the second carriage 107, and the lens unit 108. To form an image. Then, an analog signal is output by photoelectric conversion of the CCD 109, and converted into a digital signal by a signal processing unit at the subsequent stage. Thereby, 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. Thereafter, the document placed on the document tray 201 is automatically fed in the arrow B direction (sub-scanning direction) by the feeding roller 202, 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 102 of the first carriage 106. Therefore, the reflected light image from the image plane is sequentially sent to the CCD 109 via the first reflecting mirror 103 of the first carriage 106, the second reflecting mirror 104 and the third reflecting mirror 105 of the second carriage 107, and the lens unit 108. To form an image. Then, an analog signal is output by photoelectric conversion of the CCD 109, and converted into a digital signal by a signal processing unit at the subsequent stage. Thereby, the image of the original is read and digital image data is obtained. The document whose image has been read in this way is discharged to a discharge port (not shown).

The reflected light from the reference white plate 110 is converted into an analog signal by the CCD 109 due to illumination by the light source 102 started before reading an image in the scan mode or the sheet through mode, and converted to a digital signal by a signal processing unit at the subsequent stage. Is done. Thereby, the reference white plate 110 is read, and shading correction at the time of reading the image of the document is performed based on the reading result (digital signal).
Further, when the ADF 200 is provided with a conveyance belt, 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 even in the scan mode.

FIG. 2 is a block diagram illustrating a configuration example of a signal processing unit included in the image reading apparatus 100 illustrated in FIG. 1 together with a control unit and a memory.
The signal processing unit 1 includes a CCD 109, analog signals processing units (AFE: Analog Front End) 10, 20 on the F side and L side (multiple channels), a crystal oscillator 30, and a timing generator (TG: Timing Generator) 40. ing.

  The CCD 109 is of the FL type for analog output by dividing the main scanning line into the F side and the L side on the left and right for high speed reading. The FL type CCD 109 sequentially outputs pixel signals of the first half (F side, First) from the top pixel signal among pixel signals of the main scanning line (hereinafter also referred to as “analog signal” or “analog image signal”). And a terminal for sequentially outputting the second half (L side, Last) pixel signal from the end pixel signal. If the CCD 109 has a terminal for outputting a pixel signal of 3ch or more by dividing the pixel signal area of the main scanning line into 3 or more areas, an analog signal processing unit of 3ch or more is necessary. It becomes.

The timing generator (hereinafter also referred to as “TG”) 40 is a timing generator, and includes a multilayer clock generator 41, a plurality of phase selectors 42, and a line period generator 43, and a reference from the crystal oscillator 30. Based on the clock, a multilayer clock generator 41 generates a multilayer clock. Based on the multilayer clock, the phase selector 42 generates drive signals for the CCD 109 and analog signal processing units (hereinafter also referred to as “AFE”) 10 and 20.
The line period generator 43 counts the clocks from the multilayer clock generator 41 and outputs a main scanning synchronization signal that is asserted only once per line.

The plurality of phase selectors 42 select arbitrary rising edges and falling edges from the timing of the multi-layer clock, and output drive signals having arbitrary phases. The phase of each drive signal can be set from the external control unit 70, and the phase required for each drive signal can be set. Thereby, the phase of the sample and hold timing of each analog signal by the sample and hold circuits 12 and 22 on the F side and the L side, which will be described later, can be adjusted.
The CCD 109 is driven by drive signals (φ1, φ2, φ2L, RS, CP, SH) from the TG 40 and outputs an analog signal (hereinafter also referred to as “analog image signal”) corresponding to the reflected light from the original. The area of the original is divided into an F side and an L side on the left and right sides, and is output in analog form, and is input to the AFE (F side) 10 and the AFE (L side) 20.

Of the analog image signals output from the CCD 109, the analog image signal on the F side passes through the buffer 51 and the AC coupling capacitor 52 to the AFE (F side) 10, and the analog image signal on the L side passes through the buffer 61 and the AC coupling capacitor 62. To the AFE (F side) 20.
The AFE 10 includes a clamp circuit 11, a sample hold circuit (S / H) 12, an amplifier circuit (PGA: Programmable Gain Amplifier) 13, and an A / D converter 14.
The AFE 20 includes a clamp circuit 21, a sample hold circuit (S / H) 22, an amplifier circuit (PGA) 23, and an A / D converter 24.

The clamp circuits 11 and 21 respectively clamp the black offset level of the analog signal to a predetermined potential at the input timing of the clamp signal (CLP) from the TG 40. The clamping timing is simultaneously performed on the F side and the L side for each line.
The sample hold circuits 12 and 22 respectively sample the analog signal output from the clamp circuits 11 and 21 at the input timing of the sample hold signal (SHD) from the TG 40, and hold the analog signal level for a certain time (hold). ) This is called “sample hold”.

  The sample hold signal (SHD) is input to a switch element that turns on / off a signal to a capacitor in the sample hold circuit that holds the sample value, and sampling is started when the sample hold signal (SHD) is asserted. The sample ends at the end of assertion (hold). By sample-holding the signal area, the sample-and-hold circuits 12 and 22 continuously output the signal area level (FIG. 3). Sample hold timing is performed simultaneously on the F side and the L side for each pixel.

FIG. 3 is a timing chart showing an example of the relationship between the input timing of the sample hold signal (SHD) from the TG 40 of FIG.
The amplifier circuits 13 and 23 amplify the analog signals from the sample hold circuits 12 and 22 according to the gain setting from the control unit 70, respectively.

The control unit 70 controls the image reading apparatus 100 in an integrated manner, and includes a CPU (Central Processing Unit), a ROM that stores programs executed by the CPU, and a RAM that temporarily stores data. Yes. The control unit 70 uses the TG 40 to perform F-side and L-side sample and hold circuits so that the levels of the digital signals (image data) from the F-side and L-side A / D converters 14 and 24, which will be described later, match. 12 and 22 can function as adjusting means for adjusting the sample hold timing of each analog signal.
The memory 80 is a nonvolatile storage means such as a flash memory or a hard disk device that stores various data.

The control unit 70 increases the dynamic range of the signal by setting the gain so that the image data at the time of reading the reference white plate 110 becomes a constant level. This adjustment is performed when the image reading apparatus 100 is powered on.
Each of the A / D converters 14 and 24 quantizes the analog signal amplified by the amplifier circuits 13 and 23 at the input timing of the conversion signal (ADCK) from the TG 40 and converts it into a digital signal (image data). The timing of the A / D conversion is simultaneously performed on the F side and the L side for each pixel.

The digital signal thus obtained is sent to a subsequent image processing unit (not shown), and the F-side and L-side image data are combined.
The image processing unit also performs shading correction to normalize the image data of the document based on the image data read from the reference white plate, and causes variations in the main scanning direction such as sensitivity variations of the CCD 109 and uneven light distribution of the optical system. Correct. Since shading correction is a well-known technique, a detailed description thereof will be omitted.

  Here, as for the input timing of the sample hold signal (SHD), it is necessary to sample the signal region for a certain period of time and further hold the hold timing in the signal region. When the sample period is short, the charging time to the capacitor cannot be secured, and the signal level to be held is shifted. Even when the hold timing is out of the signal area, the signal level to be held becomes a value deviated from the signal level.

As shown in FIG. 2, in the configuration in which the AFEs 10 and 20 for processing the analog signals on the F side and the L side are mounted, due to variations in the output signal delay of the timing signal buffers 51 and 61 and variations in the time constant of the transmission line, Variations occur in the timing of the sample hold signal (SHD) input to the F side and the L side.
When the timing is shifted between the F-side and L-side sample and hold circuits 12 and 22, the F-side and L-side image levels are shifted. When the image processing unit performs shading correction, the white side or black side level (also referred to as “density level”, “tone level”, or “image level”) of the corrected image data is on the F side and L side. Although they match, there is a difference between the F side and the L side at the intermediate level, so a linearity difference occurs. When there is a level difference between the F side and the L side, there is a problem that the left and right colors are different from each other with the center of the document as a boundary, so that it is easily noticeable.

Particularly in recent years, due to the high integration of semiconductors, there is a configuration in which the functions of the AFEs 10, 20 and the TG 40 are integrated ASICs. In such a case, the ASIC on the F side operates as the TG 40 and the AFE 10, and the L side The ASIC operates as the AFE 20. In this case, the signal distance from the TG 40 to the AFEs 10 and 20 is very short on the F side and long on the L side. Therefore, the input timings of the sample and hold signals (SHD) on the F side and the L side tend to vary.
Therefore, in this embodiment, in order to match the timings of the sample and hold signals on the F side and the L side, image data is acquired by shifting the phase of the sample and hold signals so that the image levels on the F side and the L side match. Adjust the sample hold timing.

FIG. 4 is a timing chart for explaining the operation when the phase of the sample hold signal (SHD) output from the TG 40 of FIG. 2 is changed.
As shown in FIG. 4, when image data is acquired by shifting the phase of the sample hold signal, the hold timing is within the signal region, and the setting that satisfies the sample time shown in FIG. The level difference between the number F side and the L side is small.

FIG. 5 is a flowchart illustrating an example of adjustment of the sample hold signal (SHD) in the image reading apparatus 100 including the signal processing unit illustrated in FIG. In each figure including this figure, the step is abbreviated as “S”.
In the image reading apparatus 100, first, the first carriage 106 and the second carriage 107 in FIG. 1 are moved below the reference white plate 110, and the light source 102 is turned on (S1, S2). Thereby, the reflected light from the reference white plate 110 is converted into an analog signal by the CCD 109, and converted into a digital signal by the signal processing unit at the subsequent stage, whereby the reference white plate 110 is read.

Then, the control unit 70 sets the phase of the sample hold signal (SHD) to a default value (S3).
Thereafter, among the image data read from the reference white plate 110, predetermined regions of the image data on the F side and the L side are respectively acquired, and an average value (hereinafter simply referred to as “F”) of the predetermined regions of the acquired image data. (Also referred to as “average value of predetermined regions on the side and L side”) (S4).

Here, the average value of the image level of the predetermined area can be calculated as shown in any one of (1) to (3) below. Note that, instead of obtaining the average value, only a predetermined image level (one pixel) may be detected and used.
(1) Image levels at a plurality of predetermined locations (plural pixels) in the predetermined area are detected and averaged.
(2) A plurality of lines are detected and averaged at a predetermined (one pixel) image level in the predetermined area.
(3) A plurality of lines of image levels at a plurality of predetermined locations (plural pixels) in the predetermined area are detected and averaged.

Further, the image level of the image data read from the reference white plate 110 is not uniform in the main scanning direction due to the uneven light distribution of the optical system. For example, as shown in FIG. 6, by acquiring each image data in a predetermined range (predetermined area) near the boundary between the F side and the L side, which is the center in the main scanning direction, each image data on the F side and the L side is acquired. Image levels can be compared under equivalent conditions. Further, by calculating the average value of the image levels in a predetermined range near the boundary between the F side and the L side, it is possible to make a comparison by excluding the influence of noise and the like. The average value may be obtained from the image level of each image data in a predetermined range near the boundary between the F side and the L side of the image data of one line. Alternatively, in order to increase the accuracy of measurement, it may be obtained from the image level of each image data in a predetermined range near the boundary between the F side and the L side among the image data of a plurality of lines.
FIG. 6 shows the image level in the main scanning direction of the image data read from the reference white plate 110 in FIG. 1, and a diagram for explaining the calculation of the average value of the image levels near the boundary between the F side and the L side. It is.

After performing the process of step S4, the control unit 70 calculates the difference between the average values of the predetermined areas on the F side and the L side, and the difference is less than or equal to the expected value determined by the design (within the expected value range). (S5), and if it is less than the expected value, there is no problem with the phase of the current sample and hold signal (SHD), and the adjustment is terminated.
When the difference between the average values of the predetermined areas on the F side and the L side exceeds the expected value (not within the range of the expected value), the adjustment is continued.

Then, the control unit 70 stores the difference between the set value of the phase of the current sample hold signal (SHD) and the average value of the predetermined areas on the F side and the L side in the memory 80 (S6).
Next, it is determined whether or not all the settable phases have been tried. If not, the process returns to step S3 to change the setting of the phase of the sample hold signal (SHD).
After that, among the image data read from the reference white plate 110, the predetermined areas of the image data on the F side and the L side are respectively acquired again, and the average value of the image levels after the phase change of the predetermined area of each of the acquired image data Are respectively calculated (S4).

Subsequently, the control unit 70 calculates the difference between the average values of the F-side and L-side predetermined regions after the phase change, and determines whether the difference is equal to or less than the expected value determined by the design (S5). If it is below the expected value, the adjustment is terminated.
When the difference between the average values of the F-side and L-side predetermined regions after the phase change exceeds the expected value, the phase set value of the current sample hold signal (SHD) and the F-side and L-side values after the phase change The difference between the average values of the predetermined areas is stored in the memory 80 (S6).

Thereafter, the process proceeds to step S7, and it is determined whether or not all the settable phases have been tried again. However, the process proceeds to step S3 until all the settable phases are tried, and the same adjustment as described above is continued.
When the phases of all possible sample and hold signals (SHD) are tried and the difference between the average values of the predetermined areas on the F side and the L side does not fall below the expected value (S7), the memory 80 With reference to the result of the trial, the phase of the sample hold signal (SHD) is set such that the difference between the average values of the predetermined areas on the F side and the L side is the smallest (S8), and the adjustment is finished.

With the above adjustment, the sample hold timing is adjusted so that the image levels on the F side and the L side match, and the linearity characteristics can be matched.
Note that by performing the adjustment when the power of the image reading apparatus 100 is turned on, it is possible to adjust to an optimal state regardless of a change in state over time.

FIG. 7 is a block diagram illustrating another configuration example of the signal processing unit included in the image reading apparatus 100 of FIG. 1 together with the control unit 70 and the memory.
As shown in FIG. 2, in the configuration in which the F-side and L-side sample and hold timings are driven by a common signal, when the difference between the F-side and L-side timings is large, optimal settings should be made. Is difficult.
Therefore, for example, as shown in FIG. 7, the F-side and L-side sample hold timings are driven with different sample-hold signals (SHD_F, SHD_L) on the F side and L side, respectively, so that more accurate adjustment is performed. It becomes possible.

FIG. 8 is a flowchart illustrating an example of SHD adjustment in the image reading apparatus 100 including the signal processing unit illustrated in FIG.
This flowchart adjusts the sample hold signal (SHD_L) when the delay variation of the L side sample hold signal (SHD_L) is large due to a long distance between the TG 40 and the L side AFE 20.

In the image reading apparatus 100, first, the first carriage 106 and the second carriage 107 in FIG. 1 are moved below the reference white plate 110, and the light source 102 is turned on (S11, S12). Thereby, the reference white plate 110 is read as described above.
Then, the control unit 70 sets the phase of the sample hold signal (SHD_F, SHD_L) to a default value (S13, S14).

  After that, among the image data read from the reference white plate 110, predetermined regions of the image data on the F side and the L side are respectively acquired, and the average value of the image levels of the predetermined regions of the acquired image data (F side and L The average value of the predetermined area on the side) is calculated (S15). Note that the method for obtaining the predetermined areas of the image data on the F side and the L side is the same as that described with reference to FIGS.

Subsequently, the control unit 70 calculates a difference between the average values of the predetermined areas on the F side and the L side, and determines whether the difference is less than or equal to the expected value determined by the design (within the expected value range). (S16) If it is below the expected value, there is no problem with the phase of the current sample and hold signal (SHD_L), so the adjustment is terminated.
When the difference between the average values of the predetermined areas on the F side and the L side exceeds the expected value (not within the range of the expected value), the adjustment is continued.

Then, the control unit 70 stores the difference between the phase set value of the current sample hold signal (SHD_L) and the average value of the predetermined areas on the F side and the L side in the memory 80 (S17).
Next, it is determined whether or not all the settable phases have been tried. If not, the process returns to step S14 to change the phase setting of the sample hold signal (SHD_L).
After that, among the image data read from the reference white plate 110, the predetermined areas of the image data on the F side and the L side are respectively acquired again, and the average value of the image levels after the phase change of the predetermined area of each of the acquired image data Are respectively calculated (S15).

Subsequently, the control unit 70 calculates the difference between the average values of the F-side and L-side predetermined regions after the phase change, and determines whether or not the difference is less than or equal to the expected value determined by the design (S16). If it is below the expected value, the adjustment is terminated.
If the difference between the average values of the F-side and L-side predetermined regions after the phase change exceeds the expected value, the phase set value of the current sample hold signal (SHD_L) and the F-side and L-side values after the phase change The difference between the average values of the predetermined areas is stored in the memory 80 (S17).

Thereafter, the process proceeds to step S18 to determine whether or not all the settable phases have been tried again. However, the process proceeds to step S14 until all settable phases are tried, and the same adjustment as described above is continued.
When the phases of all the sample-and-hold signals (SHD_L) that can be tried are tried and the difference between the average values of the predetermined areas on the F side and the L side does not become less than the expected value (S18), the memory 80 With reference to the result of the trial, the phase of the sample hold signal (SHD_L) is set such that the difference between the average values of the predetermined areas on the F side and the L side is the smallest (S19), and the adjustment is finished.

With the above adjustment, the sample hold timing is adjusted so that the image levels on the F side and the L side match, and the linearity characteristics can be matched.
Note that by performing the adjustment when the power of the image reading apparatus 100 is turned on, it is possible to adjust to an optimal state regardless of a change in state over time.

According to the image reading apparatus of the first embodiment, the following effects (1) to (6) can be obtained.
(1) The TG 40 can adjust the phase of the sample and hold timing of each analog signal by the sample and hold circuits 12 and 22 on the F side and the L side (multiple channels). The sample hold timing of each analog signal is adjusted by the TG 40 so that the levels of the digital signals from the D converter 14 coincide. Thereby, the occurrence of the linearity difference can be avoided.

(2) The control unit 70 individually adjusts the sample hold timing of each analog signal so that the levels of the respective digital signals match. Thus, even when the level variation of each digital signal is large, the sample hold timing of each analog signal can be adjusted, so that the occurrence of a difference in linearity can be reliably avoided.
(3) The control unit 70 can remove the influence of noise by performing the adjustment using the average value of the level of each digital signal.

(4) The control unit 70 can adjust the white level of each digital signal by performing the above adjustment when the CCD 109 converts the reflected light from the reference white plate 110 into an analog signal.
(5) By performing the adjustment using the level near the boundary between the digital signals, the control unit 70 can remove the influence of fluctuations in the main scanning direction due to optical light distribution unevenness.
(6) By performing the above adjustment when the image reading apparatus 100 is turned on, the control unit 70 can adjust the sample hold timing of each analog signal to an optimum state regardless of the state change over time. Become.

  The embodiment in which the present invention is applied to an image reading device (scanner or the like) that reads an image of a document with a CCD has been described above. However, the present invention is not limited to this, and the image reading device that reads an image of a document with another image sensor. Of course, the present invention can also be applied to various image forming apparatuses such as a digital multifunction machine, a digital copying machine, a facsimile machine, and a printer equipped with the image reading device. The image forming apparatus main body can print the image data from the image reading apparatus on a sheet such as paper as a visible image. Accordingly, it is possible to provide an image forming apparatus that can efficiently acquire a high-quality image.

[Second embodiment]
Next explained is the second embodiment of the invention.
FIG. 9 is an overall configuration diagram showing a configuration example of a mechanism portion of the image forming apparatus according to the second embodiment of the present invention, and the same reference numerals are given to the same portions as those in FIG.
The image forming apparatus 300 is a digital copying machine on which the image reading apparatus 100 shown in FIG. 1 (including the signal processing unit shown in FIG. 2 or FIG. 7) is mounted.

As shown in FIG. 9, the image forming apparatus 300 is provided with an ADF 400 on an upper part of a contact glass 101 on which an original is placed. A hinge or the like (not shown) is provided so that the ADF 400 can be opened and closed with respect to the contact glass 101. It is connected through.
The ADF 400 includes a document tray 401 as a document placement table on which a document bundle composed of a plurality of documents can be placed. Further, when a print key on an operation unit (not shown) is pressed, the originals are separated one by one from the original bundle placed on the original tray 401 with the image surface facing upward, and automatically fed, and the sheet through reading slit 111 is provided. Alternatively, separation / feeding means including a feeding roller 402 and a conveying belt 403 that are conveyed toward the contact glass 101 is also provided.

The document fed by the feeding roller 402 or the conveying belt 403 is read on the image as described with reference to FIG. 1 and then discharged onto the upper surface of the ADF 400 by the conveying belt 403 and the discharging roller 404.
Here, the operation of the controller (not shown) and the ADF 400 when the document is conveyed to the reading position of the contact glass 101 by the ADF 400 will be described.

  The feed motor of the ADF 400 is driven by an output signal from the controller. When the feed start signal generated by pressing the print key on the operation unit is input, the controller corrects the feed motor.・ Reverse drive. When the feeding motor is driven to rotate in the forward direction, the feeding roller 402 rotates clockwise to automatically feed the document located at the highest position from the bundle of documents toward the sheet-through reading slit 111 or the contact glass 101. Be transported. When the leading edge of the document is detected by the document set detection sensor 405, the controller drives the feed motor in reverse based on the output signal from the document set detection sensor 405. This prevents subsequent documents from entering and prevents separation.

  When the document set detection sensor 405 detects the trailing edge of the document, the controller also counts a rotation pulse of a conveyance belt motor (not shown) from this detection point, and when the rotation pulse reaches a predetermined value, the conveyance belt 403. Is stopped and the conveying belt 403 is stopped, whereby the document is stopped at the reading position on the contact glass 101. Further, when the trailing edge of the document is detected by the document set detection sensor 405, the feeding motor is driven again, and the subsequent document is separated and automatically fed as described above. Then, the sheet is conveyed toward the contact glass 101, and when the pulse of the feeding motor from the time when the document is detected by the document set detection sensor 405 reaches a predetermined pulse, the feeding motor is stopped and the next document is detected. To wait first.

  When the document stops at the reading position on the contact glass 101, the image of the document is read. When this image reading is completed, a signal indicating that is input to the controller, so that the controller drives the conveyance belt motor in the normal direction by this signal, and the document is discharged from the contact glass 101 by the conveyance belt 403 to the discharge roller. Unload to 404.

As described above, the original bundle placed on the original tray 401 in the ADF 400 with the image side of the original facing upward is automatically fed from the uppermost original by pressing the print key. For example, the reading position on the contact glass 101 is read. It is conveyed to.
The original that has been conveyed to the reading position and stopped is discharged from the discharge port by the conveying belt 403 or the like after the image is read. Further, when it is detected that there is a next document on the document tray 401, the next document is automatically fed and conveyed onto the contact glass 101 like the previous document.

  The transfer sheets (paper sheets) stacked on the first tray 301, the second tray 302, and the third tray 303, which are sheet feeding trays, are a first sheet feeding unit 311, a second sheet feeding unit 312, and a third sheet feeding unit, respectively. The sheet is fed by 313 and conveyed by the vertical conveyance unit 314 to a position where it abuts on a drum-shaped photosensitive member (photosensitive drum) 315 as an image carrier. Actually, any one of the trays 301 to 303 is selected, and the transfer paper is fed therefrom. Also, a recording medium other than transfer paper can be used.

On the other hand, the image data read by the image reading apparatus 100 is written on the surface of the photoreceptor 315 charged in advance by a charging unit (not shown) by a laser beam from a writing unit 350 in the printer as an image forming unit (there is When the surface is exposed), the portion passes through the developing unit 327, and a toner image is formed there. The developing unit 327 that performs the image formation, the charging unit, and the like constitute image forming means.
The transfer sheet fed from the selected paper feed tray is transferred by the transfer belt 316 at the same speed as the rotation of the photoconductor 315, and the toner image on the photoconductor 315 is transferred. Further, the toner image is fixed by the fixing unit 317, and is discharged by a paper discharge unit 318 to a paper discharge tray 319 outside the apparatus.

  At this time, for example, in order to reverse the transfer paper on which the toner image is formed on one side in order to discharge face-down (the image surface faces downward in order to align the transfer paper in the page order), the transfer paper is discharged. The paper is conveyed to the double-sided paper conveyance path 320 by the unit 318, switched reverse by the reversing unit 321, and then discharged to the paper discharge tray 319 through the reverse paper conveyance path 322.

When images are formed on both sides of the transfer paper, the transfer paper on which the image is formed on one side is conveyed to the double-sided input conveyance path 320 by the paper discharge unit 318 and is switched back by the reverse unit 321. After that, it is sent to the duplex conveying unit 323.
The transfer paper sent to the double-sided conveyance unit 323 is fed again from the double-sided conveyance unit 323 to transfer the toner image formed on the photoconductor 315 again, and is again applied to the photoconductor 315 by the vertical conveyance unit 314. It is transported to the contact position. Then, after the toner image is transferred to the other surface, the toner image is fixed by the fixing unit 317 and discharged to the paper discharge tray 319 by the paper discharge unit 318.

  The photoconductor 315, the conveyance belt 316, the fixing unit 317, the paper discharge unit 318, and the development unit 327 are driven by a main motor (not shown), and the driving force of the main motor is transmitted to each of the paper feed units 311 to 313 by a paper feed clutch. Driven. The vertical conveyance unit 314 is driven by the driving force of its main motor being transmitted via an intermediate clutch.

  The writing unit 350 includes a laser output unit 351, an imaging lens 352, and a mirror 353. Inside the laser output unit 351, a laser diode that is a laser light source and a rotating polygon mirror (polygon mirror) that scans the laser light. Or it has a vibrating mirror. The laser light emitted from the laser output unit 351 is deflected by a polygon mirror or a vibrating mirror, passes through an imaging lens 352, is folded by a mirror 353, and is focused on the surface of the photoreceptor 315.

According to the image forming apparatus (digital copying machine) of the second embodiment, the image reading apparatus of the first embodiment is provided, and an image is formed on a recording medium based on image data read by the image reading apparatus. Therefore, it is possible to avoid the deterioration of the image quality of the formed image. That is, it is possible to achieve high image quality of the formed image.
In addition, this invention is not limited to each embodiment mentioned above, It cannot be overemphasized that all the technical matters contained in the technical idea described in the claim are object.

1: Signal processing unit 10, 20: Analog signal processing unit (AFE)
11, 21: Clamp circuit 12, 22: Sample hold circuit (S / H)
DESCRIPTION OF SYMBOLS 13, 23: Amplifier circuit (PGA) 14, 24: A / D converter 30: Crystal oscillator 40: Timing generator (TG) 41: Multilayer clock generator 42: Phase selector 43: Line period generator 51, 61: Buffer 52, 62: AC coupling capacitor 70: Control unit 80: Memory 100: Image reading device 101: Contact glass 102: Light source 103: First reflection mirror 104: Second reflection mirror 105: Third reflection mirror 106: First carriage 107 : Second carriage 108: Lens unit 109: CCD image sensor 110: Reference white plate 111: Sheet-through reading slit 201: Document tray 202: Feed roller 200, 400: ADF 300: Image forming apparatus 315: Photoconductor 317: Fixing Unit 327: Development unit 350: Writing unit

JP 2009-10931 A

Claims (7)

Converts the reflected light from the subject into analog signals, divides the area into multiple areas and outputs multiple analog signals, and samples and holds multiple analog signals from the image sensor and outputs them A plurality of systems of sample and hold circuits, a plurality of systems of analog signals from the plurality of systems of sample and hold circuits, respectively, a plurality of systems of A / D converters that convert them into digital signals, the image sensor, and the plurality of systems An image reading apparatus having a sample-and-hold circuit and a timing generator for generating a drive signal for the A / D converters of the plurality of systems,
The timing generator is capable of adjusting the phase of the sample and hold timing of the analog signals of the multiple systems by the multiple sample and hold circuits,
An adjustment means is provided for adjusting the sample hold timing of the analog signals of the plurality of systems by the timing generator so that the levels of the digital signals of the plurality of systems from the A / D converters of the plurality of systems match. An image reading apparatus.   The image reading apparatus according to claim 1, wherein the adjustment unit individually adjusts sample hold timings of the analog signals of the plurality of systems so that levels of the digital signals of the plurality of systems match.   The image reading apparatus according to claim 1, wherein the adjustment unit performs the adjustment by using an average value of levels of the digital signals of the plurality of systems. The image reading apparatus according to any one of claims 1 to 3,
A reference white plate used when performing shading correction on the digital signal of the plurality of systems,
The image reading apparatus according to claim 1, wherein the adjustment unit performs the adjustment when the image sensor converts the reflected light from the reference white plate into an analog signal.   5. The image reading apparatus according to claim 1, wherein the adjustment unit performs the adjustment using a level near a boundary of the digital signals of the plurality of systems.   6. The image reading apparatus according to claim 1, wherein the adjustment unit performs the adjustment when the image reading apparatus is powered on.   An image forming apparatus comprising the image reading apparatus according to claim 1.

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