JPH0797827B2 - Image processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention forms a latent image on an electrophotographic photoreceptor and develops the formed latent image to form an image according to input image data. The present invention relates to an image processing apparatus having an image forming unit.

[Prior Art] Conventionally, in an image processing apparatus such as a digital copying machine,
Some kinds of preset gradations are stored in a memory for image adjustment, and an appropriate gradation is selected from the memories to perform the image adjustment. However, in this method, fine gradation adjustment is often insufficient. For this reason, the white part will be blown out or the dark part will be darkened in spite of trying to produce the bright part. Alternatively, when the tone of the dark part is made bright and the tone of the bright part becomes white, it may happen. This is because the types of gradations to be selected are limited, and the device cannot follow variations in the characteristics of the image reading unit or the reproducing unit or changes in the characteristics of the reading unit or the reproducing unit. It was

In particular, with respect to changes in the image forming characteristics, even if a part of the image forming means is changed, it is necessary to reset the entire characteristics, which requires complicated processing.

[Problems to be Solved by the Invention] Therefore, according to the present invention, a plurality of functions that affect the image forming characteristics of the image forming means are stored, and each of them is rewritable, thereby changing the image forming means. It is an object of the present invention to provide an image processing device capable of flexibly coping with.

[Means for Solving the Problems] In order to solve the above problems, the image processing apparatus of the present invention forms a latent image on an electrophotographic photosensitive member, and develops the formed latent image to obtain input image data. An image processing apparatus having an image forming unit for forming an image according to the first storage, which stores a relationship between the input image data and a surface potential formed on the electrophotographic photosensitive member in accordance with the data. Means, a second storage means for storing the relationship between the surface potential and the development density, and an image forming characteristic of the image forming means obtained based on the stored contents of the first and second storage means. And third rewriting means for rewriting the stored contents of the first and second storage means.

[Embodiment] The image processing apparatus of the embodiment shown in FIG.
, CCD 3, amplifier 4, A / D converter 5, γ-RAM
6, D / A converter 7, triangular wave generator 8, comparator 9, laser driver 10, semiconductor laser 11
A cleaning unit 12, a polygon mirror 13, an electrophotographic photosensitive member 14, a charger 15, a developing unit 16, and a transfer separation unit 17.
Input device 20, RAM 21, CPU 22, program ROM 2
3, CCDRAM24, printer RAM25, E-VRAM26, V-DR
With AM27.

The RAM 21 has a pointer P.

In the configuration of FIG. 1, the image electric signal converted by the CCD 3 is amplified by the amplifier 4 and converted into 6-bit digital image data by the A / D converter 5. Then γ-
The image data is γ converted by the RAM 6. After γ conversion, it is converted into an analog signal by the D / A converter 7 and input to one end of the comparator 9. The output signal from the comparator is current-amplified by the laser driver 10 to turn on the semiconductor laser 11 according to the time width. In this way, the laser beam is pulse-width modulated according to the image signal level and recorded as an output image.

Here, the value of γ-RAM6 is the V-input from the input device 20.
Based on the printer characteristic created from the D characteristic and the EV characteristic, the CCD characteristic input from the input device 20, and the density characteristic input from the input device 20, according to the program ROM 23, the RAM 21
It is calculated by the CPU 22 using the pointer P in the table. CCDRAM2
4, the printer RAM 25, the E-VRAM 26, and the V-DRAM 27 store their respective characteristics, and the density characteristics are stored in the RAM 21.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an image processing apparatus of the embodiment.

The original 1 is projected by the lens 2 to form an image on the CCD 3 and is converted into an image electric signal. It is also possible to use an image sensor such as a contact sensor instead of the CCD3. The image electric signal is amplified by the amplifier 4 and converted by the A / D converter 5 into 6-bit digital image data. Next, the γ-RAM 6 performs γ conversion on the image data. This part will be described later. After γ conversion, it is converted into an analog signal by the D / A converter 7 and input to one end of the comparator 9. On the other hand, a pattern signal such as a triangular wave generated by a pattern signal generator such as the triangular wave generator 8 is input to the comparator. The readout of the CCD 3 and the cycle of the triangular wave are synchronized by the synchronization signal φ with the BD signal as a reference.

FIG. 2 shows the relationship between the triangular wave and the image signal after D / A conversion. D
The output of the / A converter 7 has a level of 00H in the case of 6 bits in the white part, and the level of 3FH in the black part is compared with the triangular wave. Midtones will be levels between 00H and 3FH. As a result of being compared, the voltage level is converted into a time width, and the white part is almost low level, but the black part is almost Hig.
The h level is output. The halftone section is set to High level for the time corresponding to the level.

The compared signal is current-amplified by the laser driver 10 and the semiconductor laser 11 is turned on according to the high-level time width. In this way, the pulse width of the laser light is modulated according to the image signal level. The pulse-width-modulated laser light is scanned by a scanning means 13 such as a polygon mirror, and an image is formed on an electrophotographic photosensitive member 14 by a lens (not shown) or the like.
An image is formed on the electrophotographic photosensitive member 14 by a well-known laser beam electrophotographic technique. The charging device 15 charges the electrophotographic photosensitive member 14, and an image signal is projected by the laser beam to form an electrostatic latent image. Next, the developing unit 16 develops the electrostatic latent image with toner to form a visible image, and the transfer separation unit 17 on the transfer material transfers and fixes the visible image to obtain a hard copy. The transfer residual toner is cleaned by the cleaning unit 12, and the process proceeds to the next cycle.

The contents of the .gamma.-RAM 6 for .gamma.-converting the image are calculated by the CPU 22 using the pointer P in the RAM 21 based on the contents of the RAMs 21, 24, 25, 26, 27 for storing the data input from the input device 20. Is set. FIG. 3 shows this relationship. The first quadrant of FIG. 3 (b) shows the relationship between the document density Do and the image density Dp to be printed out. Input devices such as a keyboard, a mouse, a light pen, and a digitizer.
You can enter an arbitrary curve with 20. It should be noted that the density here is not a density in a strict sense, that is, -1og ₁₀ R (R is the reflectance), and it is more common for an ordinary person to handle the density with the maximum density part normalized to 1. Easy to handle when operating. The result is stored in the RAM 21 via the CPU 22.

Similarly, the relationship between the document density in the fourth quadrant and the CCD output level corresponding thereto is set in the CCD RAM 24 by the input device 20. This content is changed when the original exposure source is changed, the optical system is changed, or the CCD 3 itself is changed, but in addition to that, it may change due to changes with time or changes in temperature. In such a case, the input device 20
Rewrite the contents of CCDRAM24. Note that it is also possible to automatically check the characteristics and rewrite the correction contents without using the input device 20.

The first quadrant of FIG. 3 (a) shows the relationship between the surface potential of the electrophotographic photosensitive member and the development density at that time, and is called the VD characteristic. VD characteristics are liable to change, and change due to toner lot differences, changes over time, changes in temperature and humidity, and usage conditions. According to these changes, the contents of the V-DRAM 27 are rewritten by the input device 20 each time. Note that this can also be automatically performed. The fourth quadrant shows the relationship between the image signal input to the D / A converter 7 and the surface potential obtained on the electrophotographic photosensitive member at that time, and is called the EV characteristic. This is changed according to the amplitude of the triangular wave and the frequency offset, and also changes due to the characteristics of the laser driver 10 and the semiconductor laser 11, the individual variations of the electrophotographic photosensitive member 14, the temperature, the humidity, and the changes over time. In response to these changes, the input device 20 causes the E-
Rewrite the contents of VRAM26. Note that this can also be automatically performed.

From the VD characteristic and the EV characteristic, the relationship between the image signal in the second image limit and the developing density (called printer characteristic) can be obtained. For example, the E-VRAM 26 is accessed by using the photoconductor potential as an address of 6 bits, and the image data of B'is output from the EV characteristic at that time. Similarly, V-DRAM is used as the address of the photoconductor potential 6 bits.
27 is accessed, and the development density of B is output from the VD characteristics. From these, a table having image data as data and development density as an address is completed. This is stored in the printer RAM 25. These are performed via the CPU 22.

Similarly, also in FIG. 3B, the RAM 21 storing the input desired density characteristic is accessed using the document density Do as an address, and the print density Dp at that time is output as data. Image data is output from the printer RAM 25 using the print density Dp as an address. .
Similarly, the CCD-RAM 24 also outputs a CCD output based on the CCD characteristics, using the document density Do as an address. This CCD output is used as an address, and the image data at that time is stored as data in the γ-RAM 6. Note that it is desirable that the contents of γ-RAM6 be retained even if the main unit switch is turned off by the backup power supply, and that if the contents of γ-RAM6 are destroyed by some adjustment, the universal characteristics of each property will be retained. It is desirable to put it in ROM so that it can be recovered.

4 (a) and 4 (b) show the flow chart of the program for calculating the contents of the .gamma.-RAM 6 contained in the program ROM 23. Hereinafter, description will be made step by step. First, in step S40-41 of FIG. 4 (a), the VD characteristic is input from the input device 20 to the V-DRAM 27 by using the photoconductor potential V as an address. In steps S42-43, the photoconductor potential V is input from the input device 20.
The EV characteristic is input to the E-VRAM 26 by using as an address. The pointer P is set to 0 at step S44. Step S
Use the pointer P as an address at 45 and develop density from V-DRAM 27
Dp is read out, and the image data is read out by the E-VRAM 26 using the pointer P as an address in step S46. Then, in step S47, the Dp obtained in step S45 is used as an address, and the image data obtained in step S46 is stored in the printer RAM. While counting up the pointer P at step S48, steps S45 to S49 are continued until the last address of the V-DRAM is accessed, and if the last address of the V-DRAM is accessed, the process proceeds from step S49 to step S50. At this point, the printer characteristics are created in the printer RAM 25 with the development density Dp as an address.

Moving to FIG. 4 (b), .gamma.-RAM6 is cleared at step S50. Then, in steps S51-52, the density characteristics input from the input device 20 are stored in the RAM 21 using the original density as an address. After the pointer P is cleared in step S53, the output density Dp is read from the density characteristic stored in the RAM 21 by using the pointer P as an address in step S54, and step S55.
Then, the image data is read from the printer RAM 25 by using the Dp read in step S54 as an address. In step S56, the pointer P is used as an address to read the CCD output from the CCDRAM24, and in step S57, the CCD read in step S56.
The image data read in step S55 is stored in the γ-RAM 6 with the output as an address. While counting up the pointer P at step S59, steps S54 to S59 are repeated until the end of the original density, which is the address of the density characteristic, and when the end is reached, the process proceeds from step S59 to step S60. At this point, the creation of the contents of the γ-RAM is completed. Step S
At 60, the copy of the original is executed.

The case where the Do-Dp curve is a straight line with an inclination of 45 ° corresponds to the case where the original is faithfully reproduced, but this state is not always the preferable reproduction. For example, when reproducing human skin, it is preferable to set the density range of the skin to be slightly brighter than the original, and to make the γ curve in this region slightly absent. In order to make such a delicate adjustment, it is impossible to select the γ curve from among the preset ones, and it is necessary to make an arbitrary adjustment. In this embodiment, any γ adjustment can be made.

The output characteristics of the CCD3 are linear with respect to the amount of light, but have a Log curve with respect to the document density, and the characteristics of the printer are S-shaped curves. I can't easily guess what will happen. Therefore, it is not easy for a person skilled in image adjustment to input the contents of the straight line γ-RAM6. On the other hand, with the Do-Dp characteristic, it is easy to understand intuitively and can be easily handled by ordinary people. That is, even an ordinary person can easily and arbitrarily adjust the tone of the image. Such desirable Do-Dp
By inputting CCD characteristics, VD characteristics, EV characteristics, etc. as necessary in addition to inputting characteristics, it is possible to easily correct the fluctuations of the respective fluctuation factors, and thus more stable image reproduction can be performed.

Although the tone control of the image signal from the original is described in the above description, the tone control can be performed by inputting the image signal from an external device through an appropriate interface. For example, if a video signal is input before the A / D converter 5 or an image signal from an electronic file is input after the A / D converter 5, the tone-controlled content can be printed out.

It should be noted that in the present embodiment, the γ conversion was described, but the idea of the present invention can be effectively used in other digital conversions.
Further, not only the image input from the image reading means but also the image stored in the file can be processed by setting the input characteristic of the recorded image.

As described above, according to the present invention, the gradation of the image signal can be arbitrarily changed, and the gradation can be easily specified from the input characteristic and the output characteristic of the image. Therefore, the gradation can be easily specified. It is possible to provide an image processing apparatus capable of combining different input means and output means.

Further, by using the γ-converting unit as in the present invention, it is possible to reproduce the gradation featuring an inflection point where the density is reversed in a certain region, and it is also possible to realize a new graphic expression which has never existed before. .

Furthermore, according to this embodiment, it is possible to correct the CCD characteristic, the VD characteristic, and the EV characteristic, which have such variable factors, so that it is possible to provide an image processing apparatus capable of more stable image reproduction.

[Effects of the Invention] According to the present invention, a plurality of functions that affect the image forming characteristics of the image forming means are stored, and each of them can be rewritten, thereby flexibly responding to changes in the image forming means. It becomes possible to do.

[Brief description of drawings]

FIG. 1 is a block diagram of the image processing apparatus of this embodiment, FIG. 2 is an explanatory diagram of pulse width modulation, FIG. 3 (a) is an explanatory diagram of printer characteristic creation, and FIG. 3 (b) is a .gamma.-RAM. FIG. 4 (a) and FIG. 4 (b) are flow charts for creating characteristics. In the figure, 1 ... manuscript, 2 ... lens, 3 ... CCD, 4 ...
Amplifier, 5 …… A / D converter, 6 …… γ-RAM, 7 ……
D / A converter, 8 ... Triangular wave generator, 9 ... Comparator, 10 ... Laser driver, 11 ... Semiconductor laser, 12 ... Cleaning unit, 13 ... Polygon mirror, 14
…… Electrophotographic photoreceptor, 15… Charger, 16 …… Developing section, 17…
… Transfer separation part, 20 …… input device, 21 …… RAM, 22 …… CP
U, 23 ... Program ROM, 24 ... CCD-RAM, 25 ... Printer RAM, 26 ... E-VRAM, 27 ... V-DRAM, P ... Pointer.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Moto Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yukihiro Ozeki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Hiroshi Sasame 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tetsuo Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 56) References JP-A-60-37877 (JP, A) JP-A-61-1175 (JP, A) JP-A-56-141673 (JP, A) JP-A-60-54567 (JP, A)

Claims (1)

[Claims] 1. An image processing apparatus having an image forming means for forming a latent image on an electrophotographic photosensitive member and developing the formed latent image to form an image according to input image data. First storage means for storing a relationship between input image data and a surface potential formed on the electrophotographic photosensitive member according to the data, and second storage for storing a relationship between the surface potential and the development density. Means, third storage means for storing the image forming characteristics of the image forming means obtained based on the stored contents of the first and second storage means, and storage of the first and second storage means An image processing apparatus comprising: a rewriting unit that rewrites contents.