JPH0456476A - Picture reader - Google Patents

Abstract

PURPOSE:To keep picture quality constant and to stabilize the reading of high- definition picture by comparing a value reading a white board with a prescribed value by an image sensor, and displaying an alarm or an error message based on the compared result. CONSTITUTION:A CPU 230 compares the value of the reflection density of the white board read by a three-line color CCD sensor 103 with a surface contamination constant stored in a working RAM, for example, and when a reading optical system is contaminated and the value of the reflection density is lower than the contamination constant, for example, the message of 'clean the optical system', etc., is displayed through a driving circuit 251 to a display means 250 such as an LCD or the like at an operation part on the upper face of the image reader. Thus, a service man or the like can clean the optical system in an optimum period and a picture having satisfactory gradation reproducibility can be obtained without the flicker of the picture or the degradation of gray balance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device, and particularly to an image reading device using an image sensor.

[Prior Art] Conventionally, in an image reading device that digitally reads images using an image sensor such as a CCD, there have been problems such as uneven sensitivity of each pixel of the image sensor and illuminance of an illumination system consisting of a light source such as a halogen lamp, a reflective shade, etc. Image shading caused by unevenness and the like can be corrected by white level correction (shading correction) using a standard white plate that serves as a reference for the white level during image reading.

In the shading correction, as described above, prior to reading the original, a standard white plate placed outside the original position is read, and the actual image reading signal is corrected according to the reading level. In other words, if the read data of the standard white board is Rs, the uncorrected image data when the actual image is read is Ri, and the corrected image data after shading correction is Ro, then Ro=(Ri/Rs) X 255
(1) (255: normalization coefficient when the image data is 8 bits) Correction is executed by the following calculation, but as can be seen from equation (1), the level of the corrected image data Ro is the standard white board reading level. It greatly depends on the level of data Rs. In other words, if the reflection density of the standard white plate is lower than the reflection density of the white part of the image before correction (Ri<Rs), the value when reading the white part of the original of the image data R8 after correction is Ro<255 from equation (1). As a result, the white parts of the document do not become white, but appear as image fog.

Conversely, if the reflection density of the standard white plate is higher than the reflection density of the white part of the image before correction (Ri>Rs), the value of the post-correction image data Ro when reading the white part of the original will be Rs ≥ Ri. Ro=255 for the uncorrected image data, and the image is read as a low-density image.

For this reason, it is extremely difficult to manage the reflection density of the standard white plate, and variations in the reflection density of the standard white plate cause fogging and jumps in the reproduced image density, resulting in differences in gradation reproducibility between devices. . In other words, if the standard white plate becomes dirty with dust, toner, etc., fogging and skipping will occur, causing image deterioration.

On the other hand, in an image reading device that digitally reads an image using an image sensor such as a COD, an illumination system for illuminating an original includes a light source such as a halogen lamp, a reflective shade, and the like. Due to the heat generated by this lighting system, the CCD,
This will cause trouble to the CCD drive driver, etc. For this reason, normally a cooling fan is used to cool the inside of the image reading device, but the cooling fan generates an air flow. Airflow is also generated when the illumination system scans back and forth. These airflows cause toner, oil, dirt, etc. inside the machine to float, and these stains adhere to the standard white board, lighting lamps, reflective shade 1 reflective mirror, condensing lens, CCD, etc. If these reading optical systems become dirty, it also causes fogging or skipping of images.

In particular, in digital color copying machines, etc., which have multiple image sensors arranged in parallel for each color separation and read out line-sequentially, slight fogging or skipping appears as color unevenness, and gray The balance becomes unstable.

[Problems to be Solved by the Invention] In the above conventional example, toner, oil, dirt, etc. inside the machine float, and these stains are scattered on the standard white board, lighting lamps, and reflective shade 1.
It adheres to reflective mirrors, condensing lenses, CCDs, etc., dirtying the reading optical system and causing image fogging and skipping, leading to image deterioration. could not deal with the deterioration of

In addition, when using a digital copying machine system by combining a document reading device and a printer device that uses so-called electrophotographic technology, if the output image is fogged or skipped, it is necessary to check whether there is a problem with the document reading device or the printer device. It was difficult to determine whether the problem was caused by the problem or not, and it was difficult to deal with the problem.

An object of the present invention is to provide an image reading device that solves the above problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an image reading device that performs white correction of document read data using a white plate that serves as a reference level for reading the white portion of the document by an image sensor. , a comparison means for comparing the value read on the white board by the image sensor and a predetermined value, and a warning when the value read by the image sensor falls below the predetermined value based on the comparison result of the comparison means. or means for displaying an error message.

[Function] According to the present invention, with the above configuration, image quality can be kept constant, high-quality image reading can be performed stably, and even a person who is not familiar with the entire system can handle the system.

[Examples] Hereinafter, the present invention will be described in detail using preferred embodiments with reference to the drawings.

FIG. 2 is a diagram showing an example of a schematic internal configuration of an image reading device to which the present invention is applied.

100 is an original pressure plate, 1402 is a platen glass on which the original 102 is placed, and 110 is a halogen lamp 1 for exposing the original.
501 and a first reflecting mirror 105, and 111 is a mirror unit consisting of a second reflecting mirror 106 and a third reflecting mirror 107. 108 is a lens unit for reducing and forming a reflected light image from the original 102 exposed and scanned by the halogen lamp 104 on the 3-line color CCD sensor 103;
The mirror units 110 and 111 are moved in the direction of arrow A (
(sub-scanning direction).

Color separation image signals read line by line by the 3-line color CCD sensor 103 during exposure scanning are input to a video processing circuit 200 shown in FIG. 1 and subjected to signal processing.

The signal 214 is a signal line for driving the 3-line color CCD sensor 103, and the necessary driving pulses are generated by the pulse generator 201.

In FIG. 2, reference numeral 1504 is a white plate for correcting the white level of an image signal, which will be described later.By reading and scanning the reflected light from a single white plate 15040 irradiated by a halogen lamp 104 with a 3-line color CCD sensor 103, A signal level of a predetermined density can be obtained and is used for white level correction of video signals.

Note that the video processing circuit 200 shown in FIG. 1 is controlled by a central control unit CPU 230 via a bus 231.

Next, the video processing circuit 200 will be described in detail. As described above (the original 102 is first irradiated with the halogen lamp 1501, the reflected light from the original 102 passes through the mirror units 110 and 111, the optical lens 108,
A reduced image is formed on the 3-line color CCD sensor 103,
The color is separated and read. Three line sensors 103a, t03b of the 3-line color CCD sensor 103,
The output from 103c is the amplifier circuit 202.203°20
4, the signal is amplified to a predetermined level.

Figure 3 shows the 3-line color CCD sensor 103 shown in Figure 2.
This is a configuration diagram of 10μm×10μm as one pixel, and 5
A line sensor 103a with 000 effective pixels,
Three lines of sensors 103b and 103c are arranged in parallel on a common chip 30 with a distance of 180 um (1 g line), and each line sensor is dyed with R, G, and B organic dyes. In addition, each line sensor is R-CCD103a, G-CCD103b, B-
It is assumed that the CCD 103c. In addition, each COD is independently
and are driven synchronously.

Each CCD 103a, 103b, 103c outputs a video signal V1. 1, Vo, and Vm are independently output, and after being amplified to a predetermined voltage value by independent amplifiers 202, 203, and 204, A/D conversion circuit 205.
206 and 207, each is converted into 8-bit digital data.

Next, in this embodiment, as described above, each CCD has an interval of 18 lines (10 μm x 1 g = 1801 t m) in the sub-scanning direction, and the image is scanned in advance in the reading direction A in FIG. Red (R) filter CCD
Viewed from 103a, CCD with green (G) filter
103b, and CCD1 of the blue (B) filter
The distance from 03c is 18 lines (180 μm) and 36 lines, respectively.
line (360um), each CCD 103a,
The reading positions on the document by 103b and 103c are shifted.

Therefore, in order to connect them correctly, the following correction operation is performed using memory for multiple lines. In other words, B-CCD10 is the last one to be read out of the three CCDs.
To synchronize with 3c, the sub-scan reading density is set to 400.
dpi, R-CCD for 100% same size reading
The buffer memory 208 of 103a contains 36 lines of G
- The buffer memory 209 of the CCD 103b has a synchronization memory for 18 lines.

As shown in FIG. 1, the digital data from the A/D conversion circuits 205, 206 and 207 is temporarily stored in the buffer memories 208 and 209 (only R and G data), and then goes to the black level correction circuits 210, 211 and 212. The black level is corrected by the white level correction circuits 213, 214, and 215 (details will be described later), and the logarithmic conversion circuits 216, 217
, 218, is subjected to masking processing in a masking circuit 219, and is processed by a black extraction/undercolor removal (LICR) circuit 2.
20 , black extraction/bottom removal is performed, γ correction is performed in a γ correction circuit 221 , main scanning scaling processing is performed in a main scanning scaling processing circuit 222 , and output from the video processing circuit 200 through a filter/sharpness circuit 223 .

FIG. 4 shows an example of the configuration of the white level correction circuits 213, 214, and 215.

In the initial value setting mode, a blank sheet of paper (for example, copy paper) is placed on the platen glass 1402, and the white sheet and white plate 1 are
The ratio of the reflection density of 504 is measured for each color CCD and for each pixel according to the flowchart below, and the CPU
230 backup memory (not shown). However, the white level correction circuit 213, 214, 21
5 have the same configuration and operation, so one of them will be explained as a representative.

In the flowchart of FIG. 5, in step 501, the optical system 110 is moved to the bottom of the blank paper on the platen glass 101.
, and in step 502 the halogen lamp 1501 is turned on.
is turned on, and in step 503, the white image data of the uniform white level output from the CCD 103c is sent to the selector 402.
One line is stored in the correction RAM 401 via the gate 404.

Next, step 504 Te, CP [J230 is the correction RAM
White image data (WD, )/(W
, ), =1 to 4678 are temporarily stored in the working RAM via the gate 409.

Then, in step 505, the optical system 110 is connected to the white plate 1504.
In step 506, selector 40 selects the uniform white level white image data output from CCD 113 again.
2. I-2 minute correction RAM 401 via gate 404
Store it in

In step 507, the CPU 230 downloads the white image data (Ws
+) ~(Ws+57a) is stored in the working RAM. Next, in step 508, blank image data (Wol) stored in each working RAM, = 1 to 467.
Divide the image data (Ws+) t・1~4678 of the white plate by 8 to obtain the measured value c of the white plate noise, = (ws+)/(w
o3) Store in working RAM as i=1 to 4678 and back up.

Here, the output measurement value of the blank paper is set to N (・type 255),
Also, as mentioned above, a white board is a so-called gray with a lower reflection density than white paper, but it is extremely difficult to reproduce a perfect gray, so if it has some color tinge or some discoloration, If white correction is performed using this as a white plate, the gray balance of the read image data will be disrupted. Therefore, R, G, and B CCDs when reading a white board
Assuming that the output balance has collapsed, by setting a white board brightness correction factor K (=typ1) for each color as a coefficient to correct the imbalance, it is possible to correct the gray balance described above. The expected white paper output value N and the white board brightness correction factor are also stored in the working RAM and backed up together with the white board brightness measurement value C.

In the present invention, in step 509, the value of the reflection density WS of the white plate is compared with the contamination constant D (stored in the working RAM, for example). Normally toner, oil, dirt, etc. are standard white boards, lighting lamps.

If the reading optical system becomes dirty due to adhesion to the reflection mirror, condenser lens, CCD, etc., the reflection density of the standard white plate will be higher than the reflection density of the white part of the image before correction, and the image will have a lower density. The image is read as a low-density image.For this reason, if the reading optical system becomes dirty and the reflection density value falls below the dirt constant D (set value), the process proceeds to step 510, and the CPU 230, for example, reads the image shown in FIG. Display means such as LCD of the operation section on the top surface of the image reading device (250 in Fig. 1)
A message such as "Please clean the optical system" is displayed on the drive circuit 251 (indicated by ).

This allows service personnel and the like to clean the optical system at the optimal time, and provides images with good gradation reproducibility without image distortion or deterioration of gray balance.

If the standard white plate reflection density is higher than the contamination constant, E
It becomes ND.

In fact, prior to a copying or reading operation, the exposure lamp 1
04 is turned on, the white plate 112 is exposed, and the white image data of the uniform white level output from each CCD is sent to the selector 40.
2. Correction RAM 401 for one line via gate 404
Store in.

Next, a correction coefficient for each pixel is calculated according to the flowchart in FIG. That is, in step 601, the correction RAM 4
01 is stored at addresses W1 to W4878 into the working RAM of the CPU 230.
03 and 404 are closed, the gate 409 is opened again, and data is set so that B of the selector 409 is selected.

As a result, the correction RAM 401 is accessed by the address from the address bus of the CPU 230, and the white image data (Wl) to (W, , . . . ) are read to the working RAM of the CPU 230 via the gate 409 and the data bus.

Next, in step 602, the white image data (W4) to addresses W1 to W46□8 imported into the working RAM are
For (Ls7g), the expected output value N of the blank paper backed up in the working RAM, the white board spacing correction,
Using the whiteboard distance measurement value C, (i 1 ~ 4678),
A shading correction coefficient of Ei=(N XC, XK)/W (i=1 to 4678) is calculated for each pixel.

Then, in step 603, gates 403 and 409 are closed, gate 404 is opened, and selectors 407 and 409 are closed.
Set data in the latch 408 to select B of 06, and read the address W1 to W46 of the correction RAM 401 again.
Data in the working RAM is written from the CPU 230 via the selector 402 and the gate 404 in accordance with the address data.

When reading the original image, the correction coefficient E1 is stored in the correction RAM 40 in synchronization with the human image data D input to the B1n terminal.
1 to the multiplier 407 via the gate 403,
The calculation DO=Di XE+ is performed for each pixel and output as corrected data.

FIG. 7 shows a flowchart of another embodiment.

In this embodiment, steps 701 to 7
The steps up to 09 are the same as the embodiment shown in FIG.

In this embodiment, when the reading optical system becomes dirty and the reflection density value falls below the dirt constant, the process proceeds to step 710, where the average value of the image data of the white plate (WSA=(W9
i) i=1 to 467g/4678) is calculated by the CPU 230, and in step 711 the voltage of the illumination lamp driver (not shown) is increased by WsA/D to increase the light intensity of the illumination lamp (here, the voltage of the illumination lamp and The amount of light shall be linear. If it is non-linear, it will be corrected accordingly).

As a result, even if the reading optical system of the image reading device becomes dirty and the reflection density of the standard white plate decreases, the light intensity can be increased to obtain the reflection density that would be obtained if the optical system was not dirty, resulting in a wide dynamic range. This has the advantage of producing high-quality images with good tonality.

Of course, this can also be done using software. That is, when the reading optical system becomes dirty and the value of the reflection density falls below the dirt constant, (W, ), = 1 to 46.
By adding 78/D to the shading correction value, a large dynamic range can be obtained and a high quality image with good gradation can be obtained.

[Effects of the Invention] As explained above, according to the present invention, when the value read by the image sensor of the reflected light from the white plate falls below a certain value, a warning or an error message is displayed, thereby improving the reading optical system. can notify you when it is dirty. This not only allows you to maintain a constant image quality and read high-quality images (even if you are not familiar with the system, you can easily determine where in the system the image fogging or skipping is occurring). It has the effect of being distinguishable.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts of an image reading device according to the present invention, Fig. 2 is a diagram showing the internal configuration of the device, Fig. 3 is a block diagram of a 3-line color CCD sensor, and Fig. 4 is a white level level diagram. Block diagram of correction circuit, Figures 5 and 6
7 are flowcharts of each operation of the device. Figure Figure

Claims (1)

[Claims] 1) In an image reading device that performs white correction of document reading data using a white board that serves as a reference level for reading the white portion of a document by an image sensor, a value read from the white board by the image sensor and a predetermined value are determined. and means for displaying a warning or error message when the value read by the image sensor falls below a predetermined value based on the comparison result of the comparison means. Image reading device.