JP2902700B2 - Digital image processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus such as a digital copying machine, and more particularly to generation of test image information that can be used for image inspection and density adjustment. [Prior Art] In general, in a digital copying machine, image information read by an image scanner is passed through an image processing apparatus including circuits for gamma correction, color correction, gradation correction, etc., and the image is adjusted. Output and produce a hard copy of the image. Incidentally, circuits such as gamma correction, color correction, and gradation correction perform compensation for reproducing a high-quality image. However, depending on the degree of compensation, the image quality may be rather deteriorated. For example, in a circuit that handles 256 gradations from 0 to 255, if the input level is relatively large, the compensated result may exceed 255 in some cases. In such a case, for the image of the portion where the compensated tone exceeds 255, the tone is smaller than the image portion where the tone is smaller than 255.
A so-called grayscale reversal phenomenon occurs, and image quality deteriorates. In order to prevent such grayscale inversion, it is necessary to adjust the level of the input image density and the degree of compensation in each image processing block. This type of adjustment is generally performed while reading a reference original image with an image scanner and visually checking a hard copy of the read image. Further, in a digital copying machine having an external input interface, a special pattern generator for testing is connected to the interface, predetermined digital image pattern information is input, and the image is recorded to obtain gradation and the like. Checks and adjustments are made. [Problems to be Solved by the Invention] However, in a device without an external interface, accurate gradation adjustment is impossible because the whole is not digital processing. Even when an external interface is provided, a special test is performed for each adjustment. Since the device must be connected, it is not possible for the user to make frequent adjustments as necessary to obtain a high quality image. Further, since the conventional pattern generator can be connected only to the input terminal of the image processing device, when a gradation inversion occurs, it is not possible to know which block in the image processing device is the cause, and various It is necessary to repeat trial and error of adjustment for each of the various blocks, which is very troublesome. In order to solve the above-described inconvenience, the present invention makes it possible to easily detect and adjust whether an error has occurred in the image processing means itself or whether an error has occurred in the output means on the output side. The task is to

[Means for Solving the Problems]

In order to solve the above-mentioned problems, in the present invention, an image generating means (100, 11
0); test pattern generation means (170) for generating image information of a first test pattern (8 bits of count output) and a second test pattern (3 bits of count output); image processing on input image information Image processing means (130, 150) for outputting processed image information by inputting the normal image information and the image information of the first test pattern, selecting one of the image information and sending the selected image information to the image processing means A first selection unit (120) to be output; a second selection unit (160) to which the processed image information and the image information of the second test pattern are input and select one of the image information; Output means (210) for outputting the image information selected by the selection means, and selecting the normal image information via the first selection means (120) in the normal mode (mode 1). 2 means of selection 160), the processed image information is selected, and in the output unit test mode (mode 4), the image information of the second test pattern is selected via the second selection unit. When in the means test mode (mode 2), the first
The image information of the test pattern is selected and the second
Control means (190) for selecting the processed image information via the selection means. In addition, in order to facilitate understanding, in the parentheses, reference numerals or corresponding items of the corresponding elements of the embodiment shown in the drawings and described later are added for reference.

[Action]

In the normal mode (mode 1), the control means (190)
The image generating means (100, 110) is generated by selecting normal image information via the first selecting means (120) and selecting the processed image information via the second selecting means (160). The normal image information to be processed is processed by the image processing means (130, 150), and the processed image information is output by the output means (210). As a result, image information on which normal image processing has been performed can be obtained. In the output unit test mode (mode 4), the control unit (190) selects the image information of the second test pattern via the second selection unit (160), and the output unit (210) selects this image information. Output. Thereby, image information of the second test pattern, which has not been subjected to the image processing of the image processing means (130, 150), is obtained. Based on this, the appropriateness of the operation of the output means (210) can be determined. In the image processing means test mode (mode 2), the control means (190) selects the image information of the first test pattern via the first selection means (120) and the second selection means (160). ), The image information processed by the image processing means (130, 150) is selected, and the output means (210) outputs this. Thereby, processed image information obtained by processing the image information of the first test pattern by the image processing means (130, 150) is obtained. From this image information, the image processing means (13
0,150) and the output means (210) can determine whether or not the operation is appropriate. If the output means is already known, the appropriateness of the operation of the image processing means (130, 150) can be determined. Therefore, it is possible to easily check and adjust the occurrence of an error in the output means (210), and also to easily check and adjust the occurrence of an error in the image processing means (130 and 150). In the later-described embodiment of the present invention, by operating the instruction switch means (200), three kinds of test patterns (8 bits, 6 bits and 3 bits of count data) output from the test pattern generating means (170) are obtained. Are respectively connected to the plurality of image processing means (130, 150) and the output means (210) via the first selection means (120), the third selection means (140), and the second selection means (160). Is applied selectively. Therefore, for example, in an apparatus in which three image processing means (110, 130, 150) of gamma correction, color correction, and gradation correction are sequentially connected in series, a third test pattern is provided via third selection means (140). By applying (6 bits of count data) to the input of the gradation correction circuit (150), the function of only the gradation correction circuit (150) among the three correction circuits (110, 130, 150) can be checked, and the first test pattern If the (8 bits of the count data) is applied to the input of the color correction circuit (130) via the first selection means (120), the functions of the color correction circuit (130) and the gradation correction circuit (150) are checked. it can. If the test signal is applied to the gamma correction circuit (110), three correction circuits (110, 130, 150)
Can be checked, it is possible to know which correction circuit should be adjusted in the case where a grayscale reversal occurs in the recorded image due to these switchings.

【Example】

FIG. 1 shows a main part of a signal processing circuit of a digital full-color copying machine of a type embodying the present invention. Referring to FIG. 1, this copying machine includes a scanner 100, an image processing unit, and a printer 210. The image processing unit includes a γ correction circuit 110, a color correction circuit 130, and a gradation correction circuit 150, which are connected in series. That is, the R, G, B image information output from the scanner 100 passes through the γ correction circuit 110, is applied to the color correction circuit 130 via the data selector 120, and the output information of the color correction circuit 130 is output to the data selector 140. Is applied to the gradation correction circuit 150 via the
Through the printer 210. γ correction circuit 110, color correction circuit 130, and gradation correction circuit 150
Are well-known circuits that have been put to practical use in the past, and all of them perform gradation value correction as needed. That is, the γ correction circuit 110 outputs an 8-bit gradation value obtained by correcting an 8-bit input value according to a predetermined γ correction curve. In the color correction circuit 130, the input R
(Red), G (Green), and B (Blue) are processed, and output information of Y (Yellow), M (Magenta), C (Cyan), and BK (Black), which are complementary to them, are processed. Generate In the color correction circuit 130, the input information has 8 bits, and the output information has 6 bits. In the tone correction circuit 150, the number of information bits is reduced by converting the tone value into an area tone expression such as dither. In this example, an input value of 6 bits for each color is converted to an output value of 3 bits for each color. If this type of correction is performed by calculation, the result of the calculation may cause an overflow. In such a case, the magnitude relationship between the gradation values is reversed between the input and output, and the quality of the recorded image is significantly degraded. Also,
Similarly, when a failure or the like occurs in each of the correction circuits, a grayscale abnormality similarly occurs. In order to detect these abnormalities,
In this embodiment, the reference pattern information is generated inside the apparatus, and the image can be recorded. In this example, the reference pattern information is generated by the counter 170. The counter 170 is cleared by a start signal START (a pulse appears at the start of the effective image scanning area) output from the timing signal generator 180,
The line synchronization signal Lsync (one pulse appears for each line of image scanning) is counted as a clock pulse.
Since the counter 170 is an 8-bit counter, its output value is 0, 1, 2, 3,..., 254, 255, 0, 1, for each line in synchronization with the image scanning of the scanner 100 and the printer 210. 2, ...
And sequentially change. Data selectors 120 and 14 inserted in the image processing unit
0 and 160 each have two sets of input terminals A and B and an output terminal Y, and selectively output information applied to the input of any group of A and B to the output terminal Y. can do. By switching the level of the control terminal SEL, the selection group of A and B can be switched. The input terminals of the B group (8 bits × 3) of the data selector 120 are all bits (8 bits) of the output terminal of the counter 170.
Bits) are connected in parallel, and the output of the counter is
It is connected in parallel to three 8-bit input terminals corresponding to each of R, G, and B of the B group. The output terminal of the counter 170 is similarly connected to the input terminal of each B group of the data selectors 140 and 160.
For 0, of the 8 bits output from the counter 170,
Only the upper 6 bits are connected, and for the data selector 160, only the upper 3 bits of the 8 bits output by the counter 170 are connected. The input terminal groups (A, B) selected by the data selectors 120, 140, and 160 are all system control units 190
Can control the switching. An operation board 200 is connected to the system control unit 190. By operating a selection key switch (not shown) on the operation board 200, the operator can select any one of four modes. it can. That is, each of the four modes corresponds to the control signals D ₁ , D
It corresponds to the combination of ₀ , and is as follows. Mode 1: D ₁ = 0, D ₀ = 0 Mode 2: D ₁ = 0, D ₀ = 1 Mode 3: D ₁ = 1, D ₀ = 0 Mode 4: D ₁ = 1, D ₀ = 1 Mode 1 , The data selectors 120, 140, and 160 all select the A group.
140 and 160 select the B, A and A groups, respectively. In mode 3, the data selectors 140 and 160 select the B and A groups, respectively.
Selects group B. Therefore, in mode 1, mode 2, mode 3 and mode 4, the information output by the scanner, the test pattern applied to group B of data selector 120, the test pattern applied to group B of data selector 140, and The information of the test pattern applied to the B group of the data selector 160 can be output to the printer 210 and recorded. For example, the gradation of the test pattern applied to the data selector 120 is updated every time the line synchronization signal Lsync (see FIG. 2) appears.
As indicated by 301 in the figure, a pattern in which the gradation changes sequentially line by line in the range of 0 to 255 is obtained. Similarly, if mode 3 is selected, as shown as 302 in FIG.
A pattern in which the gradation changes sequentially every four lines is obtained in the range of 0 to 63. If mode 4 is selected, as shown by 303 in FIG. 3, the gradation is changed every 32 lines in the range of 0 to 7. A pattern in which the key changes is obtained. Of course, these test patterns can be changed by changing the connection relationship between the input terminal of each data selector and the bit of the output terminal of the counter 170. In each test pattern as shown in FIG.
Since the gradation changes sequentially, if a gradation abnormality occurs, it can be easily found. Also, by checking for the occurrence of a gradation abnormality (gradation reversal) according to the mode switching, it is possible to know which correction circuit has an abnormality. For example, if a reversal of gradation is detected in mode 2 (256 gradations) and mode 3 (64 gradations) and normal in mode 4, it is considered that a bit error has occurred in the gradation correction circuit 150. Can be. Also, for example, mode
Mode 1 even though all 2,3 and 4 are normal
When an abnormal image appears in the image, it can be considered that the gamma correction circuit 110 is abnormal. In the above embodiment, the line synchronization pulse Lsyn
By inputting c to the counter 170, a test pattern in which the image density changes sequentially in the recording paper feed direction is generated, but the pixel synchronization pulse in the main scanning direction is supplied to the counter instead of the line synchronization pulse. If applied, a test pattern in which the density changes in the width direction of the recording paper can be obtained.

【effect】

As described above, according to the present invention, by switching from the normal mode (mode 1) to the output unit test mode (mode 4) and the image processing unit test mode (mode 2), it is determined whether an error has occurred in the output unit itself. It is possible to easily detect whether an error has occurred in the image processing means on the upstream side and to easily adjust each means.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a part of an electric circuit of a digital color copying machine embodying the present invention. FIG. 2 is a time chart showing the timing of signals used in the apparatus of FIG. FIG. 3 is a plan view showing a recording sheet on which an image of each test pattern is recorded. 100: image scanner, 110: gamma correction circuit 120: data selector, 130: color correction circuit 140: data selector, 150: gradation correction circuit 160: data selector, 170: counter 180: timing signal generator, 190: system control Unit 200: Operation board, 210: Printer G1 to G5: Gate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 1/00 H04N 1/04

Claims (1)

(57) [Claims] 1. An image generating means for generating normal image information; a test pattern generating means for generating image information of a first test pattern and a second test pattern; Image processing means for outputting completed image information; first selection means for receiving the normal image information and the image information of the first test pattern, selecting one of the image information and outputting the selected image information to the image processing means A second selecting unit that receives the processed image information and the image information of the second test pattern and selects one of the image information; an output unit that outputs the image information selected by the second selecting unit And in the normal mode, selecting the normal image information via the first selecting means, and selecting the processed image information via the second selecting means, When the image information of the second test pattern is selected via the second selecting means, the image information of the first test pattern is selected via the first selecting means when in the image processing means test mode. And a control unit for selecting the processed image information via the second selection unit.