JPH03232367A - Picture reader using reduced optics - Google Patents

Abstract

PURPOSE:To always read an original near an optical axis even in the case of an enlarging mode or a consecutive enlarged photographing mode by integrally moving a reduced optics and a sensor in a main scanning direction. CONSTITUTION:In the consecutive enlarged photographing mode, the original is divided into panels with 6 rows and 3 columns so as to be divided into 6 in the main scanning direction (column) and divided into 3 in a sub scanning direction (row), and the respective divided areas are copied while being enlarged by magnification 400%. Therefore, areas corresponding to the sheet size of an A4S are read in the order of panels 1.1, 2.1,...6. 1 and next, reading is executed in the order of the second column while moving a register position only for d=297-17=280mm. Further, reading is executed in the order of the third column while moving the register position only for the same distance (d). At such a time, since the respective panels are always read near the optical axis while moving an imaging unit 1 in the main scanning direction, reading can be executed with high resolution and high illuminance.

Description

[Detailed Description of the Invention] Industrial Application Field] The present invention relates to an image reading device for reading image data of a digital copying machine, facsimile machine, printer, etc.
In particular, the present invention relates to an image reading device that reduces a document image using a reduction optical system and forms the image on a reading sensor.

[Conventional technology]

In recent years, digital color copying machines have been developed and researched, and the present applicant has previously filed applications regarding digital color copying machines (for example, Japanese Patent Application No. 63-292195).

This digital color copying machine reads a color original image in each of the three primary colors of light, red (R), edge (G), and blue (B), and converts the read data into an electric digital density multiplier. Imaging Human Power Terminal (IIT)
) is provided.

This IIT is equipped with an exposure lamp, a rod lens array and a CCD line sensor for reading the original image, an imaging unit that scans the original and optically reads the image, and a drive means for moving the imaging unit. , electrical hardware, etc. for performing conversion processing on the electrical reading multiplier charged and converted by the CCD line sensor.

According to such a digital color copying machine, since image signals are digitally processed, various types of processing can be easily performed, and high-quality color copies can be made.

FIG. 10 is a sectional view of an imaging unit 7) using a contact source line sensor.

The original 220 is set with the image side to be read facing downward on the platen glass 31, and the image side to be read is placed facing down on the imaging unit 3.
7 moves its lower surface in the direction of the arrow shown in the figure, and the daylight color fluorescent lamp 2
22 and a reflecting mirror 223 to expose the original surface to light. Then, the reflected light from the original 220 is transmitted to the rod lens array 22.
4. By passing the cyan filter 225, C
A royal life-size image is formed on the light receiving surface of the CD line sensor 226. The rod lens array 224 is a compound lens consisting of four rows of fiber lenses, and has the advantage of being bright and having high resolution, allowing the power of the light source to be kept low, and being compact. Further, the imaging unit 37 is equipped with a circuit board 227 including a CCD sensor drive circuit, a CCD sensor output buffer circuit, and the like. In addition, 228 is a lamp heater, 229 is a flexible cable for control signals, and 230 is a flexible cable for illumination power supply. The housing 37a to which the line sensor 226 is fixed has a circuit board 22 at the bottom thereof.
7 is attached, a heat sink 250 having a protrusion 250b is attached between the circuit board 227 and the housing 37a, and furthermore, a punching metal 251 for electromagnetic shielding is attached so as to cover the heat sink 250. A drive IC chip 252 is disposed on the circuit board 227, and the line sensor 226 is electrically connected to the circuit board 227 by a connecting pin 226a.

FIG. 11 shows an example of the arrangement of the CCD line sensor 226, and as shown in FIG.
6a to 226e are arranged in a staggered manner in the main scanning direction X. This is because it is difficult to form a large number of light-receiving elements without missing parts and with uniform sensitivity due to wafer size, yield, and cost. This is because if they are arranged side by side, it is difficult to configure pixels to both ends of the line sensor, resulting in unreadable areas.

The sensor section of this line sensor 226 has an R (
Red), G (Rin IJ-n), B (Blue) 3
Repeat the color filters in this order and arrange them next to each other.
Bits constitute one pixel during reading. Assuming that the reading pixel density of each color is 16 dots/mm and the number of pixels per chip is 2928, the length of one chip is 2928/(1
6X3) = 61m port, 61X5 = 5 chips as a whole
The length is 305 spits. Therefore, as a result, an isosceles line sensor capable of reading an A3 size image is obtained.

Furthermore, each RSG and B pixel is arranged at a 45 degree angle to reduce moiré.

In this way, when the plurality of line sensors 226a to 226e are arranged in a staggered manner, adjacent line sensors scan different document surfaces.

That is, when the line sensor is moved in the sub-scanning direction Y orthogonal to the main-scanning direction X of the line sensor and the document is read,
The first row of line sensors 226b scans the original in advance.
, 226d and the subsequent signals from the second row of line sensors 226a, 226C, 226e, there is a time lag corresponding to the positional lag between adjacent line sensors.

Therefore, in order to obtain one line of continuous signals from image signals divided and read by a plurality of line sensors, at least the first row of line sensors 222 that scan the original in advance must be used.
b, 226 (t to (memorize the word) and 1 followed by the second row of line sensors 226a, 22.6c, 226e
It is necessary to read out the signal in synchronization with the signal output from.

In this case, for example, if the amount of deviation is 250 μm and the resolution is 1
Assuming 6 dots/rule, a delay of 4 lines is required.

In order to configure a sensor from multiple chips, it is necessary to correct the joints of the chips, and there is also a circuit that converts 5 chips in parallel to series, a dark correction circuit for each pixel of t to correct the dark reference between chips, and a point sequential method. In this case, the unevenness of the analog frequency characteristics leads to color layering of RlG and B, so high precision is required, which increases the cost, and the cost of the sensor itself also increases.

Furthermore, since the rod lens array 224 used in the contact type line sensor has a shallow depth of focus, blurring occurs even if the document is lifted about 1 meter from the platen surface.

Therefore, when trying to copy a book, for example, the center part of the book cannot be brought into close contact with the platen surface, so it bulges up and becomes blurry. Furthermore, when an ADF (Auto Document Feeder) is used, the document inevitably becomes wavy, resulting in areas that cannot be brought into close contact with the platen surface, and similarly, there is a problem in that blurring occurs, making it impossible to make good copies.

Therefore, the present applicant has already filed an application for a reduced color sensor in place of the contact type line sensor (for example, Japanese Patent Application No.
265932).

FIG. 12 is a diagram showing a schematic configuration of an image manual terminal <IIT> 32 of a color copying machine in an embodiment of the present invention. In FIG. 12(a), the IIT 32 is composed of an optical scanning mechanism and a reading sensor 37 as described above.

The optical scanning mechanism includes a fluorescent lamp 20 for illuminating the original.
1. - full rate mirrors (Full Rate M
mirror; FRM) 202 and a pair of half rate mirrors (Half Rate Mirror;
HRM) 203. 204, and an optical lens 20 that forms an image on the reading sensor 37.
It consists of 5. The FRM 201 is inclined at approximately 45° and is attached to the first carriage 207 with its reflective surface facing upward and to the left in the figure.

Similarly, a fluorescent lamp 201 is also attached to the first carriage 207. The first carriage 207 is movable along the sub-scanning direction of the color copying machine. This allows scanning for reading the original on the platen glass 31. Further, a pair of HRMs 203 and 204 are provided on the second carriage 209 at an angle of about 45 degrees and are vertically overlapped. In that case, the upper HRM 203 has its reflective surface facing toward the lower right in the figure, and the lower HRM 203
204 has its reflective surface facing upward and to the right in the figure. In this way, each mirror 202, 203, 20
4, the optical reading force of the original on the platen glass 31 is introduced into the optical lens 205.

The second carriage 209 is also movable in the sub-scanning direction. The moving speed vl of the first carriage 207 is set to be twice as large as the moving speed v2 of the second carriage 209. In this way, the first and second carriages 207 . ．． By setting the speed ratio of 209 to 2, the moving distance of FRM202 is always HRM203.204
This is twice the distance traveled. Therefore, each mirror 202
．． No matter which position 203 and 204 move, the optical path length from the original to the optical lens 205 is always constant [e.g., approximately 500 mm in the examples shown in FIGS. (The distance from the optical lens 205 to the optical lens 205 is constant.)

As shown in No. 121m(d), the CCD sensor 37 has a pixel row 217a formed by color filters having spectral sensitivities of red (R), Jl'j (G), and blue (B).

217b and 217c are formed as a highly integrated three-line sensor (three-color line sequential sensor) 217 arranged above and below. Currently, this 3-line sensor 217 has 1 pixel and 1 pixel.
1μm, number of pixels in each pixel column 5゜000, pixel column spacing 15
A size of 4 μm has been realized. Using this 3-line sensor 217, 16 dots/open (that is, 1 pixel 6
The size of the optical system when reading an A3 short side (297 mm) document is as shown in Figures (b) and (c), and the size of the 3-line sensor 231 is as shown in Figure (d).
) as shown. The magnification m in this optical system is m=11/62.5'q115.7. Therefore, the pixel column interval on the reading sensor 37 side is 1
54 μm becomes 875 μm on the original side.

Note that the focal length r of the optical lens 205 in this case is 75
tnm.

Such a reading sensor 37 can be attached to a board 221 as in the conventional case, and this board 221 is attached to the color copying machine main body 30.
It is designed to be installed in an adjustable position.

CC used in image reading device with such reduction optical system
A reading sensor consisting of a D line sensor can be formed compactly because the read optical image is reduced by an optical lens.
A three-line sensor (three-color line sequential sensor) has been developed in which pixel rows are arranged vertically using color filters having spectral sensitivities of , G, and B. Since this three-color sequential sensor is small, it is formed with a high degree of integration.

[Problem to be solved by the invention]

By the way, the conventional reduction optical system lens is placed at the center of the area where various types of documents can be read in the main scanning direction, and therefore, compared to the center of the reading area near the optical axis of the lens, the edge of the reading area away from the optical axis is has the problem of poor MTF. For example, when enlarging the document by 400% as shown in Figure 13, the document is placed in the corner register R and enlarged, so only the portion with poor MTF is used for scanning, which is extremely inefficient. , there is a problem that the image becomes blurred. Furthermore, the illuminance of the large surface when an image is formed by the lens decreases as it moves away from the optical axis, and is proportional to cos'θ, where θ is the half-plane angle as shown in the figure. Therefore, when reading at a position off the optical axis, there is a problem that the illuminance decreases and it is not possible to obtain a sufficient reading gradation.

The present invention is intended to solve the above problems.

The purpose of the invention is to use a reduction optical system and always obtain the best MT
The purpose is to enable reading with F.

Another purpose of this station is to use a reduction optical system to allow reading without reducing the gradation.

Another object of the present invention is to use a reduction optical system to obtain high image quality with no reading resolution or color shift in enlargement mode, narrow document reading, enlargement continuous shooting mode, etc. be.

[Means and operations for solving the problems] The present invention is characterized in that the reduction optical system and the reading sensor can be integrally moved i in the main scanning direction.

In the present invention, by integrating the reduction optical system and the reading sensor and moving them in the main scanning direction, the original can be read near the center of the optical axis. for that,
A document detection sensor detects the size of the document during prescanning, and the sensor is driven in the main scanning direction so that the center of the document is near the optical axis. For example, even when a small original is placed on the corner register, such as when magnifying 400%, the sensor is moved to the corner register side and read with the best MTF near the optical axis. Since there is little influence from the law, reading can be performed with high screen illuminance, and the reading gradation does not deteriorate. Also,
In cases such as enlarged continuous shooting mode, the optical axis can be aligned with the center of each reading area, so it is also the best MTF.

It becomes possible to perform reading with high image illuminance.

〔Example〕

Examples will be described below.

FIG. 1 is a diagram for explaining the present invention in detail. In the figure, 1 is an imaging unit, 2 is a reduction optical system, and 3 is a reading sensor.

As shown in FIG. 1(a), conventionally, the original is read by the imaging unit 1 at position A. Therefore, when enlarging the original 220 placed on the corner register R as shown in the figure, it is necessary to Because the image was read far off-axis, the image was blurred and the illuminance decreased. In contrast, in the present invention, the imaging unit 1 is moved in the main scanning direction and the document is read near the optical axis of the reduction optical system 2. As shown in Figure 2, the horizontal axis is the linear density, and the vertical axis is M.
When TF is used, when the imaging unit is at the 8th position as in the past, the characteristics are as shown by the broken line, but when the imaging unit is moved to the B position and reading is performed near the optical axis. The characteristics are shown as a solid line,
It becomes possible to significantly improve MTF and perform high resolution reading.

Note that the degree to which the imaging unit should be moved in the main scanning direction varies depending on the size of the document and the position where the document is placed. In this state, a reading sensor is used to detect and judge the size and position of the document and determine how far it should be moved.

Further, FIG. 1(b) is an explanatory diagram when the present invention is applied to an enlarged continuous shooting mode.

Enlarged continuous copying mode is a mode in which each part of the original is enlarged and copied, and multiple copies are linked to make very large copies.To do this, one original is divided into multiple parts, and a set number of copies are made. This mode enlarges and copies each divided area to the finished size. For example, a manuscript A4L (297mm x 210cm), a paper A4S (2
10w x 297 city>, image size AOL (1188
The case of 400% magnification and 6 rows and 3 columns will be explained with reference to FIG.

In FIG. 3, the document is divided into 6 panels in the main scanning direction (columns) and 3 panels in the sub-scanning direction (rows), with 6 rows and 3 columns.
Each divided area is enlarged and copied at a magnification of 400%. The finished size of each of the 18 panels corresponds to the paper size of A4S, and the length in the main scanning direction is 210M, and the length in the sub-scanning direction is 297 marks. The resulting image size when these panels are connected corresponds to AOL, so the overall main scanning direction is 1183 mm.
, the length in the sub-scanning direction is 840 mm.

Therefore, the overlapping amount a of each panel in the main scanning direction is: a = <210 x 6 mm - mm - 1l88 +
5 = 14.4mm The overlapping amount of each panel in the sub-scanning direction is b = (29783mm - 840) + 3 =
It is 17mm. In this way, by connecting the copies with some overlap in the main scanning direction and the sub-scanning direction, it is possible to make seamless enlarged copies.

For this purpose, the shaded panel 1.1.2.1.
...Read the area corresponding to the A4S paper size in the order of 6.1, then set the registration position to d=297-17=
Reading is performed in the order of moving the register position by 280 mm to the second column, moving the register position by the same distance d and reading the third column, and so on. At this time, as shown in FIG. 1 et al., by moving the imaging unit 1 in the main scanning direction and always reading each panel near the optical axis, it is possible to read with high resolution and high illuminance.

FIG. 4 is a perspective view showing an embodiment of a structure for moving the sensor in the main scanning direction, and FIG. 5 is a sectional view of the main part.

In this embodiment, the reduction optical system 2 and the CCD are mounted on the member 7.
A movable table 5 on which a sensor 3 is mounted is movable in the main scanning direction by a motor 10 and a scanning wire (or belt) 11. The moving table 5 includes a driving motor 10 such as a stepping motor and a tension pulley 1.
The guide 13 is driven by a scanning wire stretched between the guide 13
The lid is guided and driven in the main scanning direction, and the positioning sensor 14 detects whether the lid is attached. Between the CCD sensor and the circuit chips 22 and 23 is the fifth
As shown in the figure, they are connected by a drive signal cable 20 and a video signal cable 21. In the case of a sensor using a reduction optical system, the sensor does not scan the platen surface, so there is space around the Tribe No. 8 cable and video signal cable, and the cable can be easily shielded. Therefore, noise generation can be reduced by lift force.

FIG. 6 is a perspective view showing another embodiment of the structure for moving the sensor in the main scanning direction.

In this embodiment, a ball screw 16 is rotated by a driving motor 10 such as a stepping motor, and guided by a slide shaft 17 to move the moving table 5 in the main scanning direction. The points are the same as in the case of FIG.

FIG. 7 is a diagram showing an example of the overall configuration of a color copying machine to which the present invention is applied.

A color copying machine to which the present invention is applied has a base machine 30 as a main body, a platen glass 31 on which an original is placed, and an image manual terminal (IIT) 32.
, electrical system control storage section 33, image output terminal (I
OT) 34, paper tray 35, user interface (
It consists of an edit pad 61 and an auto document feeder (ADF) as options.
) 62, sorter 63 and film projector (F/
P) 64.

Electrical hardware is required to control the above-mentioned ITTS 10TSU/1, etc., but this hardware is required to control each of the IIT, IPSSU/I, F/P, etc. that performs image processing on the output signal of the IIT. It is divided into multiple boards for each processing unit, and the SYS board and IOT control them.

Electrical control system storage section 33 along with MCB board (master control board) etc. for controlling ADF, sorter, etc.
It is stored in.

11T32 is a reading sensor 37 consisting of a CCD sensor, etc.
and a scanning optical mechanism consisting of a plurality of scanning mirrors 38 and an optical lens 205 that forms an optical image of the original onto the reading sensor 37. The primary color of light B
(blue), G (edge), and R (red), convert them into digital image signals, and output them to the iPS.

IPS converts the B, G, and R signals of the IIT32 into toner primary colors Y (yellow), C (cyan), M (magenta), and K (black), and further converts the color, gradation, definition, etc. In order to improve the reproducibility, various data processing is performed to convert the process color gradation toner signal into an on/off binary r-signal, which is output to the 10T34.

10T34 has a scanner 40, a sensitive material belt 41,
The image signal from the IPS is converted into an optical signal in the laser output section 40a, and is transmitted to the photosensitive material belt 4 via the polygon mirror 40b, the SF/θ lens 40c, and the reflective mirror 40d.
A latent image corresponding to the original image is formed on the original image. The sensitive material belt 41 is driven by a drive boob J41a, and a cleaner 41b1 belt 74@41 cXY, M, C is placed around it.
, a developing device 41d and a transfer device 41e are arranged. Then, a transfer device 4 is placed opposite to this transfer device 41e.
2 is provided, and a paper conveyance path 3 is provided from the paper tray 35.
For example, in the case of a four-color full-color copy, the transfer device 42 is rotated four times to transfer Y, M, and C1K to the paper in the order of Y, M, and C1K. The transferred paper passes from the transfer device 42 to the vacuum photographing device 43, is fixed by the fixing device 45, and is discharged. In addition, the paper conveyance path 3
5a has 5SI (single seat inserter) 35b
Paper is also selectively supplied from the machine.

The U/I 36 allows the user to select a desired function and instruct its execution conditions, and is equipped with a color display 51, a hard control panel 52 next to it, and an infrared touch board 53 to control the screen. Direct instructions can be given using soft buttons. Next, options for the base machine 30 will be explained. One is the coordinate input device Eddy 7) on the platen glass 31.
A pad 61 is placed on the pad 61 to enable various image editing using a manual pen or a memory card. In addition, the existing ADF6
2. The sorter 63 can be attached.

Furthermore, the feature of this embodiment is that the platen glass 31
A film image is projected onto the film using light projected from the F/P 64, and the optical image is read by the reading sensor 37 via the above-mentioned scanning optical mechanism for each R, GB, thereby making a color copy directly from the color film. It makes it possible to take

The target manuscript may be a negative film, a reversal film, or the like.

Next, the configuration of the video signal processing system of the IIT 32 will be explained.

FIG. 8 and FIG. 9 are diagrams showing an example of the configuration of a video signal processing circuit.

In FIG. 8, the three-color line sequential sensor 217 is a sensor 21 of pixel arrays using color filters each having a spectral sensitivity of R (red). It consists of a pixel array sensor 217b that uses a color filter with a spectral sensitivity of G (green), and a pixel array sensor 217C that uses a color filter that has a spectral sensitivity of SB (blue). The converted video signal is converted into a video signal color-separated into R and GSB, and outputted separately into even-numbered pixels, 1 (Even), and odd-numbered pixels (Odd).

The illustrated video signal processing circuit includes a sample and hold circuit 2.
611 Gain adjustment circuit A G C (AIITO!, IA
TICGAIN C0NTRDI, ) 262, offset adjustment circuit AOC (AljTOMATIC0FSET
C0NTR0L) 2 6 3, A/D
Conversion circuit 264, mixer 265, gap correction memory 266.266', dark output correction circuit 267.270
10G conversion table 268, shading correction circuit 2
69.271, samples and holds the analog video signal output from the three-color line sequential sensor 217, adjusts the gain, adjusts the offset i, and converts it into a digital signal. It performs gap correction, shading correction, and conversion from a luminance signal to a density signal by mixing the signals.

The gap correction memories 266 and 266' are for correcting the gap between each pixel column, and are composed of line memories having a FIFO configuration. When the sampling density in the sub-scanning direction is changed according to the reduction/enlargement ratio, the correction amount is adjusted in accordance with the change, and the signal of the pixel row that scans the document in advance is stored. The signals of each pixel column are output in synchronization.

The log conversion table 268 is, for example, Lo in a ROM configuration, which specifies that a reflected signal should not be converted into a density signal.

k Up Table (LUT), which uses the R, G, and B color separation signals obtained from the reflected light of the original as the density R.
, G, BF'. The dark output correction circuit 267 and the shading correction circuit 269 are SRA
It has M270 and M271, and performs shading correction, image data input adjustment, etc.

Dark output correction and shading correction are performed by writing reference data into SRAM, subtracting this reference data from image data, and then outputting the result.This processing allows corrections due to the light distribution characteristics of the light source and changes over time of the light source. Variations in the optical system due to dirt on reflective mirrors and lenses, and variations in sensitivity between each pixel of the three-color line sequential sensor 217 are corrected. Among the circuits that perform this processing, one of the dark output correction circuits 267 uses a conversion table 268.
The other shading correction circuit 269 and the conversion table 2268
It is connected to the subsequent stage to correct the reading output of the white reference plate.

For this purpose, the dark output data and the read data of the white reference plate are written into the respective SRAMs 270 and 271 as reference data.

FIG. 9 shows an example of a more simplified circuit configuration.

In the example shown in FIG. 9, each channel 1. This uses a three-color line sequential sensor 217 that serially outputs video signals for each of Il and III. Three circuits are connected to the three-color line sequential sensor 217 corresponding to each channel ■, ■■ of the color-separated pixel row, and a sample hold circuit 272 is connected to each channel.
, a dark processing circuit 273 that clamps the video signal at a reference dark level, a log conversion circuit 274 that converts the video signal to density, an A/D conversion circuit 275 that converts the analog video signal to a digital signal, and a gap correction memory. 276, 276', 276', and a shading correction circuit 277 are connected.

The gap correction memories 276, 276' and 276' are memories of the same size, and the gear tooth length on the document surface is 875 μm, the size of one pixel is 16 dots/mm, and 62
．． Assuming 5 μm, the gap correction memory 276' has a size for interpolating 875/62.5=14 lines, that is, for 8 bits and 256 gradations, a memory capacity of 8×5000×14=70 bytes is required. Therefore, the gap correction memory 276, 276' is n2 times larger, that is, 28
The number of bites for the line was 140, and the total was 2.
10 bytes of memory are required. Further, the shading correction circuit 277 stores data obtained by reading a white background (white reference board) in the SRAM 27B, and performs white shading correction by subtracting this voltage from the input image data.

Next, an overview of the dynamics of the video signal processing system will be explained along the flow of image signals.

First, the three-color line sequential sensor 217 detects the original in RlG, B
When the colors are separated and read, the even number side (
Even) and odd number side (Ocld), and the video signal is sent to the sample hold circuit 5H261. The sample and hold circuit 5H261 holds this video word in a sample and hold panos, and removes noise.

For this held video signal, the gain and offset are adjusted by a gain adjustment circuit AGC 262 and an offset adjustment circuit AOC 263, and the A/D conversion circuit 264 converts it into a digital signal. Combine signals. Among the combined R, G, and B signals, the image data is synchronized by correcting the signal j of the preceding pixel column by delaying it by the gear in gap correction memories 266 and 266'. After the shading correction circuit 267 corrects the dark level, the log conversion table 268 performs density conversion, and the shading correction circuit 269 corrects the white level.

In addition to the above copy scan mode, there is a color detection sample scan mode. In this color detection sample scan mode, first, the IIT carriages 207 and 209 are moved to the designated color detection point, and after elapse of, for example, 50 m5, the original reading density data is written to the SRAM.
After that, the data of the specified pixel is transferred to the R of the VCPU (not shown).
Transfer to AM. Note that the above 50 m5 is the time during which the IIT32 carriages 207 and 209 stop vibrating and stand still. In data capture, for example, five pixels in the main scanning direction and five pixels in the sub-scanning direction from the specified point are targeted. In this case, the specified point and the pixel data of the following five points are extracted from the pixel data of one line in the main scanning direction and read into the RAM of the VCPU, and then the IIT carriage 207209 is moved four times with one pulse each. Similarly, pixel data is read in five points at a time. The above is the process when the number of designated points is one. Therefore, if there are multiple designated points, the same process is repeated for each designated point.

Next, adjustment of read data will be explained.

In the three-color line sequential sensor 217, the fluorescent lamp 201 irradiates the document with light and reads the reflected light, so the read signal level corresponds to the reflectance and becomes higher as the document becomes whiter. Conversely, when the fluorescent lamp 201 is turned off, the three color line sequential sensor 217
The signal level (suggested output level, dark level) output from will show the lowest value. This dark level is not flat even for one chip, but varies. Normally, the white signal (read signal of the white reference plate) and black signal (implicit output) of the three-color line sequential sensor 217 are as follows.
There are variations depending on each channel and further depending on each pixel within the channel.

Therefore, in an image reading device using such a three-color line sequential sensor 217, the gain adjustment circuit AGC262 adjusts the gain to guarantee gradation, and adjusts the gain to adjust the lowest value of this dark level. The offset adjustment circuit AOC263 guarantees that the voltage is raised to a certain value.

The remaining gain adjustment circuit AGC262 is, for example, 25
With 6 gradations, the gain is adjusted so that the maximum value (peak value) of the white signal of each channel is aligned with this reference value, with 200J as the reference value for one novel A/D output.
The offset m adjustment circuit AOC263 uses "IQ" as a reference value of the A/D output level at 256 gradations, for example, and adjusts the offset value so that the minimum value of the black signal can be approximated to this reference value.

That is, in the genon adjustment, first, the read data of the white reference plate is written into, for example, the SRAM of the white shading circuit. Thereafter, the VCPU samples read data from this SRAM at predetermined pixel intervals and finds the maximum value. Then, this maximum value is a predetermined output, for example 2
The gain is adjusted to 200 at 56 gradations.

In offset a adjustment, for example, the log conversion table 268 is bypassed and the dark output is sent to the white shading correction circuit 2.
After writing to the SRAM 271 of 69, the vcpu samples the read data from this SRAM 271 at predetermined pixel intervals and finds the minimum value. Then, an offset value is set such that this minimum value becomes 10 at a predetermined output, for example, 256 gradations. In this way, the minimum value is A/D
If the output level is higher than the reference value, it will be lowered to that reference value.
Conversely, if it is smaller than the reference value, offset adjustment is performed to raise it to the reference value.

In addition, if the A/D conversion circuit 264 converts the input range of 0 to 2.5 V into a digital signal of 0 to 25501 bytes and 8 bits, the signal level read from the white reference plate is By setting the value close to 2.5V, it is possible to improve the accuracy of reading the original. However, since the reflectance of the white reference plate is about 80%, if this reading signal level is increased to, for example, about 2.3V, there is a problem that it will be saturated with the blank white of the original. Adjust the gain so that the signal 1 novel read from the white reference plate is about 2.0V, and then
I am trying to divide it into 6 equal parts and convert it to a digital signal, but
When the light intensity of the fluorescent lamp 201 decreases with use, the level of the signal read from the same white reference plate gradually decreases, and the resolution per bit decreases.

The gain adjustment AGC 262 makes it possible to obtain stable resolution even in such cases, and when the level of the signal read from the white reference plate is set to, for example, 2°OV, it is always maintained at this value. Adjust the gain so that
This allows the optimal gain to be set even for chips with varying sensor sensitivities.

However, with only gain adjustment and offset adjustment, the levels between each pixel cannot be made uniform, and the image becomes rough or has lines in areas of high density.

The ΔV dark correction (dark shading correction) corrects such unevenness in pixel units at the dark level, and the white shape ink correction corrects the A unevenness in pixel units at the white reading level. It is.

In the ΔV dark correction, the log conversion table 268 is bypassed and the dark output is sent to the white shading correction circuit 26.
After writing to SRAM271 of 9, vcpu writes this SRAM.
Read data from RAM271. This is repeated four times and integrated to obtain an average value, and this average value is stored in the SRAM 270 of the dark shading correction circuit 267.
write to.

After performing the gain adjustment, offset adjustment, and ΔV dark correction as described above, it is possible to proceed to the copy operation. In the copy operation, select the log conversion table 268, and first,
Prior to the transition to the copy cycle, writing processing of reference data to the SRAM 271 of the white shading correction circuit 269 is performed. This process includes gain adjustment,
After performing offset adjustment and further performing ΔV dark correction, the white reference plate is read, and the read data is written into the SRAM 271 as reference data. Therefore, the data written in the SRAM 271 of the white shading correction circuit 269 is the read data of the white reference plate DW, and the data written in the SRAM 271 of the dark shading correction circuit 267 is
If the correction data written in 270 is DO, it becomes log (DW - DD).

Therefore, in the actual copy cycle, the original read data DX is first transferred to the dark shading correction circuit 2.
67 performs ΔV dark correction, the manual data of the white shading correction circuit 269 becomes log (DX - DD), so if the reference data written in the SRAM 270 by the dark shading correction circuit 267 is subtracted from this data, log (DX −DO) −log <DW −
Do). In other words, as a result of correction by the darkening correction circuit 267 and the white shading correction circuit 271, the density signal is log (DX
-DD ) -log (Dlll -DO) is to be corrected, and the reflected signal is to be corrected to DW -DO.

The ΔDark correction, which is corrected based on the black signal, is performed on the reflected signal before log conversion, and the shading correction, which is corrected based on the white signal, is performed on the density data after log conversion. This makes the correction value smaller and improves the correction efficiency. Also, SRAM270, 27
By storing 1512 worth of correction data using 1 and performing correction processing by subtracting this data, a general-purpose full adder IC can be used, and arithmetic processing can be performed easily. By doing this, there is no need to assemble a hard logic divider with a complicated and large-scale circuit as in the past.

Next, control of the IIT 32 will be explained.

T I T IJ mote has sequence control for various copy operations, service support function, self-diagnosis function,
It has a fail-safe function. IIT sequence control is divided into normal scan, sample scan, and initialization. Various commands and parameters for IIT control are sent via serial communication from the SYS remote 71.

In normal scanning, the paper size and magnification are set as scan length data from 0 to 432 mm (1 ma + step), the scan speed is set by the magnification (50% to 400%), and the prescan length (from the stop position to the registration position) is set as the scan length data. Distance) data is also set by magnification (50% to 400%).

In a normal scan, first, when a scan command is received, the fluorescent lamp is turned on by the FL-ON signal, and the
The motor driver is turned on by the CN-RDY multiplier, and scanning is started after a predetermined timing. When the register position is reached, the image area signal IMG-AREA is
becomes low level for a predetermined scan period, and in synchronization with this, the IIT-PS signal is output to the IPS.

The sample scan is used for color detection during color conversion, color balance correction and shading correction when using F/P. In this sample scan: First, the first and second carriages 207 are
, 209 is moved to a target sample position and temporarily stopped, or after repeating a minute movement a plurality of times, it is stopped and sample data is collected.

When initializing the 11T, when it receives a command from the SYS remote when the power is turned on, it checks the register sensor,
Check the operation of the imaging unit using the registration sensor, and correct the home position of the imaging unit using the registration sensor.

By the way, in the processing circuit shown in FIG.
However, when increasing the sampling density in the sub-scanning direction to obtain a signal for enlarged copying, it is necessary to increase the capacity by that amount. For example, if you try to enlarge to a scaling factor of 400%, the sampling density in the sub-scanning direction will be 16X4=64 dots/
mm, and the memory capacity is four times as large as 840 bytes.

On the other hand, the ways in which color image reading devices are used can be roughly divided into two. One is for full-color reading, which requires faithful reading of so-called Victorian originals such as color photographs, paintings, and prints, and the other is for example 0% M, YS
This is for so-called functional document reading in which it is sufficient to be able to separate a total of eight colors: RSG, B, and KXW. The processing circuits shown in FIGS. 8 and 9 are applicable to full-color reading and can also be used for functional purposes.

〔Effect of the invention〕

As described above, according to the present invention, since the reduction optical system and the sensor can be moved together in the main scanning direction, even in the enlargement mode or enlargement continuous shooting mode, the image sensor is always near the optical axis. It becomes possible to read the manuscript with
The document can be read with the best TF and high image illuminance, making it possible to obtain high-resolution, high-gradation image quality.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the present invention in detail, Figure 2 is a diagram showing the relationship between linear density and MTF, Figure 3 is a diagram for explaining the enlarged continuous shooting mode, and Figure 4 is a diagram for explaining the sensor. FIG. 5 is a perspective view showing an embodiment of the structure for moving the sensor in the main scanning direction, FIG. 5 is a cross-sectional view of the main part, FIG. The figure shows an embodiment of a color copying machine to which the present invention is applied, FIGS. 8 and 9 show an example of the configuration of a video signal processing circuit, and FIG. 10 shows imaging using a contact type line sensor. A sectional view of the unit, FIG. 11 is a diagram showing an example of the arrangement of the CCD line sensor,
FIG. 12 is a diagram showing a schematic configuration of an image manual terminal of a color copying machine, and FIG. 13 is a schematic diagram illustrating problems caused by the reduction type optical system. 1... Imaging unit, 2... Reduction optical system,
3...Reading sensor, 5...Moving table, ?・・・
- Moving member, 10...Motor, 11...Scanning wire, 16...Ball screw.

Claims (2)

[Claims] (1) In an image reading device that reduces a document image using a reduction optical system and forms the image on a reading sensor, the reduction optical system is characterized in that the reduction optical system and the reading sensor are movable together in the main scanning direction. An image reading device using (2) In an image reading device that reduces a document image using a reduction optical system and forms the image on a reading sensor, a moving member on which a document detection means for detecting the size of the document, a reduction optical system, and a reading sensor are placed. 1. An image reading device using a reduction optical system, comprising: a driving means for driving a moving member in a main scanning direction based on a document detection result.