JPH0241067A - Color picture processing unit - Google Patents

Abstract

PURPOSE:To decide deficiency in luminous quantity of a light source, propriety of a CCD and a broken wire easily and surely by detecting the propriety of at least a picture read means from a level of plural digital color signals. CONSTITUTION:A optical image of an object 2 is fed to an effective area extraction circuit 15 via an optical system 3, a dichroic mirror 4, and A/D converters 10, 11. The circuit 15 detects a signal component of a maximum original width and gives it to a color discrimination circuit 20 of the next stage. A signal reading a reference white board among digital signals just before the color discrimination circuit 20 is latched by a latch circuit 200 and it is fetched by a CPU 160 for picture processing. The digital color signal fetched in the CPU 160 is fetched in a master CPU 250 controlling the optical scanning system and the CPU 250 discriminates the propriety of components, especially CCD 6, 7, or deficiency of the luminous quantity of the light source depending on the level of the digital color signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to an image processing apparatus such as a plain paper recording color copying machine and is suitable for color image processing apparatuses, in particular, the quality of image reading means, light sources, etc. The present invention relates to a color image processing device that allows for easy discrimination.

[Background of the Invention] In a color image processing device, such as a color copying machine using a laser beam, a color original is separated into multiple colors to obtain color image information, and a color image is recorded based on this color image information. I try to do that.

When recording a color image, the built-in CPU is capable of performing various image processing such as scaling processing and partial color conversion processing.

Partial color conversion processing refers to image processing in which image information inside or outside a specified area can be recorded in the color used for specifying the area, for example.

In addition, in such color copying machines, the built-in CP
The quality of the components of the copying machine is determined by U, and based on the results, copying operations are prohibited or an abnormality is displayed.

In that case, the basis for determining the quality is the image signal at the time of copying, which is read by an image reading means such as a CCD.

[Problem to be Solved by the Invention] By the way, when the internal MCP U determines whether there is a disconnection in the components of the copying machine, especially the CCD, which is an image reading means, or a light source (such as a halogen lamp) that illuminates the original, the above-mentioned problem will occur. If the image signal at the time of copying is used, it has the disadvantage that it is not possible to accurately determine whether the image reading means is defective or defective.

Since the level of image No. 18 becomes zero when the light source is disconnected, it is not possible to reliably detect whether or not the disconnection occurs based on this image signal.

However, it is impossible to judge even the quality of the CCD, which is the image reading means. This is because although the quality of COD can be determined based on a set reference level, the image signal on which the determination is based varies greatly depending on the content of the document being read.

In addition, this image No. 43 is not the signal itself, which is obtained by converting the optical image that was irradiating the original into an electrical (, ff) signal.In other words, it is an image signal that has been upgraded by AGC, etc., or has been processed by various image processing methods. This is because the signal has been subjected to

Therefore, the present invention proposes a color image processing device that can easily and reliably determine whether these parts are good or bad.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides means for decomposing color image information into a plurality of color separation images and converting them into a plurality of color signals; means for obtaining a distortion-corrected digital color signal No. 3, a color discrimination means for discriminating this digital color signal and roughly separating it into a plurality of bits of color signals, and an image processing means for the color-discriminated multi-bit color signals. and has.

The present invention is characterized in that at least the quality of the image reading means is detected from the levels of the plurality of digital colors No. 4i described above.

[Function J] The quality of the component is determined from the levels of a plurality of digital color signals supplied to the color discrimination means.

The multiple digital color signals are the image fi (No. 3) read from the reference white board with a CCD, and the A/D conversion output of this image (No. 3), which is a signal that has been subjected to shading correction. means.

[Example] Next, an example of a color image processing device according to the present invention will be described.
A case in which the present invention is applied to the color copying machine described above will be described in detail with reference to FIG. 1 and subsequent figures.

FIG. 1 is a system diagram showing an overview of this color image processing device, and shows color image information (optical@
) passes through the optical system 3 to the dichroic mirror 4.
It is separated into two color separation images.

In this example, a red R color separation image and a cyan (and Y color separation image) are separated. Therefore, the cutoff wavelength of the dichroic mirror 4 can be approximately 540 to 600 nm.

The color separated images of red R and cyan cy are supplied to image reading means, for example, CCDs 6 and 7, and image No. 43 containing only the red component R and cyan component cy is output from each image reading means, for example.

Images No. 48 R and Cy are supplied to an A/D converter 10.11, where they are converted into digital signals of a predetermined number of bits, 6 bits in this example. Shading correction is performed simultaneously with A/D conversion. 12 and 13 indicate shading correction circuits.

The shading-corrected digital image signal is extracted by the effective area extraction circuit 15 for only the 48th maximum original size, and is supplied to the color discrimination circuit 20 at the next stage. When the maximum document width to be handled is 84 size, the size signal B4 generated by the timing signal generating means 170 of the system is used as the gate signal.

Here, if the digital image signals subjected to shedding correction are VR and VC, respectively, these image signals VR.

VC is supplied to a color discrimination circuit 20 and separated into a plurality of color signals.

In this example, a case is illustrated in which a configuration is possible in which the signal is separated into three color signals: red, blue, and black.

That is, no matter what color the original is, each pixel is assigned to one of red, blue, or black. When this process is performed, each part of the document is recognized as a red, blue, or black color part.

In addition, if these red, blue, and black are other colors, roughly 4
This color discrimination processing also includes the determination of a color or more.

Each color signal that has been successfully discriminated is divided into color code data (2-t data) indicating its color information and its density data (6-t data).
It consists of

The data for each color signal is stored in a color discrimination conversion table (map) in a ROM, for example.

FIG. 2 shows an example of this color discrimination map.

It is also possible to prepare a plurality of color discrimination conversion tables and select one of them depending on the type of document, for example. In this case, a microcomputer 1 for image processing, which will be described later,
Table selection processing is executed based on instructions from 60.

The color-discriminated image data is transferred to a color image processing step.

First, it is supplied to the next-stage color ghost correction means 300, and color ghosts in the main scanning direction (horizontal scanning direction) and the sub-scanning direction (drum rotation direction) can be corrected.

This is because unnecessary color ghosts occur during color discrimination, especially around black characters.

FIG. 3 shows an example of appearance of color ghosts.

The figure shows the color ghost that appears after color discrimination is performed by capturing an image of the kanji character "sexuality" written in black.

As you can see from this example, as a color ghost,
As shown in FIGS. 4A to 4C, red and blue appear at the edge of the black line, black appears at the edge of the blue line, and black appears at the edge of the red line.

It is clear that color ghosts appear differently in other color combinations.

The color ghost correction means 300 is a circuit for correcting such color ghosts as much as possible. Color ghost processing applies only to color code data.

In this example, color ghost correction is performed using a color pattern method. This is because the color ghost color that appears is fixed for the original color, such as original black → red, helmet ghost original red, blue → black ghost. According to the color pattern method, if the color of a pixel of interest is determined by examining the color appearance (pattern) of the pixel of interest and its surrounding pixels, the color of the original image can be identified relatively easily.

As an example, FIG. 5 shows the relationship between the pixel of interest, the surrounding color pattern, and the color of the pixel of interest determined at that time.

In the first example, since both sides of the pixel of interest are white and black, the blue color of the pixel of interest is determined to be a color ghost appearing at the black edge. Red in the third example is also determined to be a color ghost of black. Therefore, in both the first and third examples, the pixel of interest is changed to black.

On the other hand, in the second and fourth examples, it is not determined that a color ghost has appeared, and the color of the pixel of interest is output as is.

This type of processing is difficult to implement with an arithmetic circuit, so in this example, it is implemented in ROM and LUT (lookup table).
It is used in the format. As a color pattern, one-dimensional or two-dimensional systems are possible, but if the number of colors is N1 and the number of surrounding pixels including the pixel of interest is M, then the size of the color pattern is N14. Therefore, if a two-dimensional pattern is used, the number of M will suddenly increase, making it impractical.

In other words, in a two-dimensional pattern, each dimension direction (main scanning direction/
Although the number of peripheral pixels in the sub-scanning direction is large (it cannot be taken), the number of patterns increases. FIG. 6 shows the relationship between the size and the number of color patterns.

In this example, the one-dimensional size is 1×7 large 1> (that is, N
=4. M=7) color pattern is used, and color ghost removal is performed independently in the main scanning direction and the sub-scanning direction.

At this time, since there is no difference in the appearance of color ghosts in the image between the main scanning direction and the sub-scanning direction, the same color pattern is used in the main scanning direction and the sub-scanning direction in this example.

The color pattern size is 1 x 7, but if the degree of color ghost appearance is small, 1 x 7 is selected.
It is also possible to use a smaller sized color pattern, such as x5. Color ghosts of up to 1 pixel can be removed with a color pattern of size 1×5, and color ghosts of up to 2 pixels can be removed with a color pattern of size 1×7.

The image data (color code data and density data) after the color ghost correction is processed in the subsequent resolution correction circuit 40, and the resolution (MTF) is corrected.

Factors contributing to resolution deterioration include optical system, optical travel system, 48
There are problems with the signal processing system, recording system, etc. Of these, the optical system and its travel system directly affect resolution deterioration.

FIG. 7 shows MTFf in the main scanning direction and sub-scanning direction when the optical system is driven! (before correction) is shown. This characteristic is 2 to 16
These are measured values when scanning a black and white pattern with a spatial frequency up to dots/mm.

The MTF in this case was defined and used as MTF=(W-BK)/(W+BK)(%). Here, W is a white signal, BK is a black 13
This is the number.

The deterioration of MTF is more significant in the sub-scanning direction. To make the same amount of correction, the amount of correction in the sub-scanning direction should be 2 times that of the main-scanning direction.
It should be set to ~4 times.

In order to correct the main and sub-scanning directions to the same degree without deteriorating the reproducibility of fine line areas, a resolution correction circuit such as a convolution film that uses 3 x 3 pixel image data should be used. can be used.

FIG. 8 shows the correction results when using the convolution filter.

The resolution-corrected density data and color code data are each supplied to the color data selector 50, and when the partial color conversion mode is selected, the image area is recorded in a specific color (see FIG. 10).

When performing image processing such as this partial color conversion mode, it is necessary to detect the markers (= signs RP and BP) from the color markers written on the document and extract that area, as shown in Figure 11. .

For this reason, a region extraction circuit 60 is provided to detect the color marker region on the document, and the region signals QR", QB" (see FIG. 11) obtained from this are supplied to the data selector 50. Ru.

In addition to these signals, the data selector 50 is supplied with a scan code signal indicating which color is currently being copied and a partial color conversion signal CC.

It is a multi-color copying machine that can record multiple specific colors, and it develops one color per rotation of the photoreceptor drum, and after all colors are developed,
In a type of printer that records a color image by performing transfer separation processing, the scan code signal indicates which color is currently being developed.

Therefore, when a blue color marker is detected, the corresponding color data can be output during the blue copy sequence and when the area signal is obtained.
Images within the blue color marker can be recorded in blue.

When not performing partial color conversion processing, density data is output only when the color code data matches the scan code signal. That is, at the end of the red copy sequence, the corresponding density data is selectively output while the red color code is being obtained.

The image data output from the color data selector 50 (
The density data) is subjected to enlargement/reduction processing in a scaling circuit 70.

Enlargement/reduction processing is performed by interpolating the density data in the main scanning direction, and by controlling the scanning speed in the sub-scanning direction (rotation direction of the photosensitive drum).

If the scanning speed is increased, sampling data in the sub-scanning direction is thinned out, resulting in a reduction process; on the other hand, if the scanning speed is made slower, an enlargement process is performed.

In this example, the color code data is also subjected to enlarging/reducing processing at the same time, and then supplied to the multi-value converting circuit 8o.

The density data subjected to the enlargement/reduction processing is sent to the multi-value conversion circuit 80.
, multi-value processing is performed. For example, by using four threshold values, 6-bit density data is quinarized.

Threshold data is set manually or automatically.

A histogram creation circuit 100 is provided to automatically determine threshold data.

The histogram creation circuit 100 creates a density histogram as shown in FIG. 9 from certain captured image data, and calculates optimal threshold data for the image based on the created density histogram.

A density histogram may be created for each color, and multi-value processing may be performed for each color using threshold data calculated based on the density histogram.

The 3-bit multi-value data that has been subjected to multi-value processing is supplied to the host computer 160 via the interface 130.

The multi-level signal passed through the host computer 160 is supplied to a laser beam printer 150 that constitutes an output device, and the laser is PWM-modulated by this multi-level signal. A photosensitive drum provided in the laser beam printer 150 is illuminated by the laser beam.

An electrophotographic color copying machine is used as a developing device provided in the Rebbeam printer 150. In this example, two-component non-contact jumping development and reversal development are employed.

That is, the transfer drum used in conventional color image formation is not used. In order to miniaturize the device, three-color images of helmet, red, and black are developed on the OPC photoreceptor (drum) for image formation in three rotations of the drum as described above, and transfer is performed once after development. The image is then transferred onto recording paper such as plain paper.

The various image processing commands and image processing timings described above are all controlled by the host computer 160.
I can do it.

170 is a processing timing (number a generation circuit) for obtaining various processing timings, and generates a timing signal for starting reading for the CCD 6°7, etc. 180
is the timing (U number generation circuit) for obtaining the scaling timing.

According to the present invention, among the digital color signals obtained immediately before the color discrimination circuit 20, a digital color signal is provided in the copying machine main body based on the digital color signal obtained when reading the reference document, in this example, the reference white plate. The quality of the parts is determined.

Therefore, the digital color signal obtained from a predetermined area is latched by the latch circuit 200, and is taken into the CPU 160 for image processing.

The digital color signals taken into the CPU 160 are roughly
CPU (master CPU) that controls the optical scanning system (scanner)
U) 250, and the quality of the parts, especially the CCD 6.7, etc., is determined from the level of the digital color signal.

FIG. 12 shows an excerpt of the signal exchange relationship among the image processing CPU 160, scanner CPU 250, and printer CPU 150A described above.

The printer CPU 150 sends horizontal and vertical effective area signals H, ■, ■, to the timing signal generation circuit 170.
■, index signal I indicating the start of each horizontal scan;
External synchronization signals such as DX and clock CLK are supplied.

The scanner CPU 250 sends an index switching signal IDX-E to the timing generation circuit 170.
X is supplied. This is a control signal for switching between the internal synchronization signal generated inside the timing generation circuit 170 and the external synchronization signal described above.

In addition, a signal COR, a reference signal REF, and a briscan signal PRE, which determine the timing to start sampling shading data, can be supplied. Reference signal REF is control number 18 for switching the reference voltage of A/D converter 10.11. Briscan signal PR
E is a control I signal for bliscan to create a histogram prior to reading the document.

The index switching signal IDX-EX, the signal COR determining the sampling start timing, the reference signal REF, and the bliscan signal PRE are all active "L".

CPU 160 for image signals and CP for scanning, U2
50, the following serial communication signals are exchanged.

The request signal REQ is a signal for controlling the transmission and reception of serial data between the scanner CPU 250 and the image processing CPU 160. This is synchronized by the serial clock SCK.

RxD refers to serial data (received data) sent from the scanner, and TxD refers to serial data (transmitted/received data) sent from the image processing side.

Specific examples of these transmitted and received data RxD and TxD are shown in FIGS. 13 and 14.

The received data RxD consists of 7 bytes, and the lower 3 bits of the first byte are I10 check data C.
This is IIKIP. This check data C11KIPO
~CHK The relationship between IF5 and the transmission mode selected thereby is shown in FIG.

In this example, in addition to mode I (which is also a normal reading mode) in which image data (digital color No. 4a) necessary for determining the quality of parts is transmitted as transmission data TxD, there are modes II and III. The data transmitted in Mode I are red and cyan digital color signals.

Mode 11 detects the light distribution state of the light source over almost the entire effective area, so the feed button 8 is used when changing the image reading position (data latch position) in one line.
In this mode, the transmission data is red and cyan digital color signals as in mode (2). The latch pulse used at this time is the center pulse C8P.

Moat River 1 also has light distribution adjustment, but this mode is used to detect the maximum level position of the linear light source. In this mode as well, the center pulse CSP is used to change the image reading position.

Of the transmission data TxD shown in FIG. 14, CO to C5
, RO to R5L indicate the level (6-bit configuration) of each cyan and red digital number 18.

An example of a code assigned to each byte of received data RxD is shown below.

1, SCO~SC2...Scan code 2, CI
ANG... Partial color conversion code 3, EE...
...Automatic threshold selection code 4, CIIKPRE
・・・・・・Bliss scan code 5, RDO-RD3・
... Red density level 6, BLO to BL3... Blue density level 7.8 KO to BK3... Black density level 8, H2O-H2S... Magnification in the main scanning direction (50 to 4
00%) In FIG. 12, the following signals are exchanged between the scanner CPU 250 and the printer CPU 150A.

Among the pulses sent from the printer CPU 150A, 5START is a pulse that designates the start of scanning for the scanner.

Transmission data TxD 1 is data indicating that a magnification is specified, and a scanning speed in the sub-scanning direction is specified for the scanner. All of these are synchronized by a serial clock 5CKI.

Image data (received data) RxDl to be actually copied is sent from the scanner CPU 250 side.

The scanner CPU 250 receives a sensor output indicating the home position of the scanner from the sensor 350h). The lighting control circuit 360 is controlled by the lighting signal generated by the scanner CPU 250, thereby controlling the lighting state of the light source (such as a halogen lamp) 370.
S is done. Further, the drive circuit 380 is controlled by the motor drive signal, and thereby the scanner drive motor 390 is controlled.

However, in this invention, the components, especially the CCD and the light source 37, are
The acceptability of 0 is determined when the optical system of the scanner is at the home position.

This will be explained with reference to FIG. First, when the copy start button is operated, the light source 370 is turned on ([mB]). After that, when a predetermined period of time has elapsed, the briscan signal PRE becomes active and the scanner 25
0 operates and a prescan operation is started, but before that, information on the reference white board is read (A and C in the same figure).

Thereafter, the sampling start signal COR becomes active (D in the figure), and the red and cyan image data are stored in the memories provided in the shading correction circuits 12 and 13. During prescan, the reference voltage REF is switched to data stored in the shading correction memory (FIG. 1).

A histogram of a specific area of the image is created during the bliscan period.

When the prescan is completed, the received data RxD is transferred to the image processing CPU 160 in response to the request signal REQ (E and F in the figure).

The CPU 160 analyzes this received data RxD. When in mode I for determining the quality of parts (CODIo, 11, light source 370, etc.), the obtained red and cyan image data are inserted into the transmission data TxD and sent to the scanning CPU 250 (see G in the same figure). ).

The scanning CPU 250 analyzes the transmitted image data to determine whether the CCD is good or bad.

As a result of the judgment, if the parts such as COD are not defective,
As soon as the Briscan mode ends, copying of the first sheet starts (A in the figure). At this time, the index switching signal IDX-EX is inverted (H in the same figure), and the signal sent from the printer CPU 150A side (IDX,
Document reading processing is performed in synchronization with H.■, V.V).

Then, only the image data within the vertical effective area signal vV is subjected to subsequent image processing (J in the same figure).

Note that shieding correction is performed based on the image data read by the reference signal REF (I in the same figure).

Figure 17 shows the CPU 1 for image processing in determining the quality of parts.
6 is a flowchart 400 showing an example of a control program that has been stored in the computer 60;

When the rising edge of the request signal REQ is detected, input of the received data RxD is started, and when all data input (7 bytes) is completed, the received data RxD inserted in the first byte is decoded (steps 401 to 401). 404)
.

As a result of the decoding, if the transmission mode is not I, the process transitions to another processing routine 405, but if the transmission mode is ■, the red and cyan digital color signals fully latched by the center pulse C3P are taken in (step 406).

The center pulse C8P is selected at a timing that can be obtained when scanning approximately the center of one line.

The captured data is transferred to the scanner CPU 250 side as transmission data TxD, and when the transferred data reaches 2 bytes, the transmission 3 mode ends and the process exits from this processing routine (steps 407 and 408).

On the scanner CPU 250 side, this transmission data TxD
Based on this, determination processing 420 as shown in FIG. 18 is executed.

First, the transmission data TxD is captured, and then it is checked whether the captured data has a capacity of 2 bytes (
Step 421.4.22). When 2 bytes of transmission data are input, the cyan and red levels of the input data are then compared with the reference level (step 423).
．． 424).

Both reference levels are set to intermediate levels.

When the maximum level is 63, about 3 rubels is set as the reference level.

If both are above the standard level, it is assumed that the COD and light source are normal and the next copy process is accepted (
step 425). However, if any of them is below the reference level, that CCD is determined to be defective or poorly adjusted, and processing for that purpose is executed (step 426).
. The processing includes prohibiting the copying operation and warning processing to that effect, and the warning processing includes flashing a lamp.

When the red and cyan levels are both below the reference level, it is determined that the light source needs to be replaced due to a decrease in the light intensity of the light source or a disconnection of the light source. When the number is 7, there will be a display to that effect. These determination processes are performed in step 426.

[Effects of the Invention] As described above, according to the present invention, the quality of a component is determined from the levels of a plurality of digital color signals supplied to the color separation means.

The plural digital color signals are image signals obtained by reading a reference white plate with CCD, and A of this image No. 643.
/D conversion output, and since it is a signal that has been subjected to shading correction, it can be determined whether the CCD is good or not, the light intensity of the light source is insufficient, etc.
It has the feature of being able to easily and reliably determine whether there is a cut or the like.

Therefore, the present invention is extremely suitable for application to a color image processing apparatus such as the above-mentioned color copying machine.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a color image processing device according to the present invention, FIG. 2 is a diagram of a color discrimination map, FIGS. 3 and 4 are explanatory diagrams of color ghosts, and FIGS. The figure is an explanatory diagram of color ghost correction, and Figures 7 and 8 are MTF.
A characteristic diagram showing correction, FIG. 9 is a diagram of a density histogram, FIG. 10 is an explanatory diagram of how color markers are changed, FIG. 11 is a system diagram of an area extraction circuit, and FIG. 12 is a diagram showing the relationship between CPUs. , Fig. 13 is an explanatory diagram of received data, Fig. 14 is an explanatory diagram of transmitted data, Fig. 15 is a diagram showing the relationship between I10 check data and transmission mode, and Fig. 16 is used to explain the transmission/reception A3 mode. A waveform diagram, FIG. 17 is a flowchart showing an example of the processing procedure in the image processor FlICPU, and FIG. 18 is a flowchart showing an example of the processing procedure in the scanner CPU. l...Color image processing device 20...Color discrimination circuit 40...Resolution correction circuit 50...Color data selector, area extraction circuit, scaling circuit, multi-value conversion circuit, histogram creation circuit, output device, CPU for image processing / Latch circuit / CPLT for scanner μm-64λ nap 11 Fig. 2 Patent applicant Konica Corporation Fig. 9 B Fig. Pixel of interest Fig. TFlliQIV)/Lα) l/mm + Fig. 12 Figure 15 Figure 16 420; Scanner (main unit) processing Figure 18 400: Image processing unit processing Figure 17

Claims (1)

[Claims] (1) means for decomposing color image information into multiple color separation images and converting them into multiple color signals; means for obtaining distortion-corrected digital color signals from these multiple color signals; It has a color discrimination means for discriminating into multi-bit color signals, and an image processing means for the color-discriminated multi-bit color signals, and detects the quality of at least the image reading means from the levels of the plurality of digital color signals. A color image processing device characterized by: