JPH0797825B2 - Image processing device - Google Patents

Description

The present invention relates to an image processing apparatus that converts an input image and outputs an output image. In particular, the present invention relates to an image processing device that changes the correlation between an input image and an output image.

[Prior Art] Conventionally, in this type of device, when the negative / positive of the image is inverted, the image signal is inverted through an inverter. However, in this method, the rising and falling edges of the image signal are delayed, and there is a difference in the response speed between the rising edge and the falling edge, which causes a difference in the pulse width of the input image signal and the pulse width of the output image signal. Therefore, there is a problem that what was recorded with a thin black line in a positive image is recorded with a thick white line in a negative image, and conversely, the white line recorded with a negative image becomes a faint black line in a positive image. It was

Further, in the LBP, since the shape of the laser spot has a Gaussian distribution, the shape of the light amount distribution differs when the laser is turned on for one dot and turned off for one dot.
Also, when reproducing an image by electrophotography, there is a difference in reproducibility between black and white of an isolated one dot.

However, the same pulse width is not necessarily required for both the negative and positive, and the optimum value differs depending on the configuration of the image input / output device. This cannot be corrected by the inverter alone.

[Problems to be Solved by the Invention] In the present invention, when an image is formed by irradiating a recording medium with a laser, output is performed regardless of the difference in light amount distribution when the laser is turned on for a predetermined time and when it is turned off. (EN) Provided is an image processing device capable of making line widths on an image substantially equal to each other and capable of excellent positive image output and negative image output.

[Means for Solving the Problem] In order to solve this problem, the image processing apparatus of the present invention is
A reading unit (corresponding to CCD3 in the embodiment) for reading the original document and a converting unit for converting the image data converted by the reading unit into reproduction image data (also corresponding to γ-RAM6) ) And control means for controlling the lighting time of the laser in accordance with the reproduction image data converted by the conversion means (also the laser driver 10
And an image forming means for reproducing the original by irradiating the recording medium with the laser (also,
(Corresponding to the polygon mirror 13) and the difference in the light amount distribution when the laser is turned on for a predetermined time and when the laser is turned off for output images depending on whether the original is positively output or negatively output by the image forming unit. Setting means for setting the conversion characteristics (also corresponding to the description on page 9, line 10 to line 12 of the specification page 9) such that the widths of the above lines are almost equal (also in the CPU 22) (Corresponding).

[Embodiment] The image processing apparatus of the embodiment shown in FIG. 1 of the present invention includes a lens 2, a CCD 3, an amplifier 4, an A / D converter 5, and γ-R.
AM6, 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, a transfer separation unit.
17, a positive / negative switch 20, a RAM 21, a CPU 22, a program ROM 23, a positive characteristic ROM 24, and a negative characteristic ROM 25.

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 is input to one end of the gonvalator 9. The output signal from the comparator 9 is current-amplified by the laser driver 10 and the semiconductor laser 11
Turn on 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, depending on the selection of the positive / negative switch 20, the γ-RAM 6 has the γ characteristic value of the positive image output stored in the positive characteristic RAM 24 when the positive image is output, and the negative characteristic when the negative image is output. Γ of the negative image output stored in the characteristic ROM 25
The characteristic value is set.

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 the comparator 9 at one end. 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 transfers and fixes the visible image on the transfer machine 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 γ-RAM6 for γ conversion of images are positive / negative switches.
Based on the positive / negative state input from 20 and stored in RAM21, CPU22 uses positive characteristic ROM24 and negative characteristic.
ROM25 is selected and set.

FIG. 3A shows the γ characteristic value at the time of negative output, and FIG. 3B shows the γ characteristic value at the time of positive output. Fig. 3 (a)
In, the input data white 00H corresponds to the output data black 3FH, and the input data black 3FH corresponds to the output data white 00H. On the other hand, in FIG. 3B, white 00H of the input data corresponds to white 00H of the output data, and black 3FH of the input data corresponds to black 3FH of the output data. Here, the curves in FIGS. 3A and 3B are set so that the line widths on the positive and negative output images are almost equal. The curves are not limited to those shown in FIGS. 3 (a) and 3 (b).

FIG. 4 shows the γ-RAM incorporated in the program ROM 23.
6 shows the flow chart of the program for setting the contents. Hereinafter, description will be made step by step. First, in step S40, the selection of the positive / negative switch 20 is read and stored in the RAM 21. Next, in step S41, it is judged whether the output image is negative or positive,
If it is negative, the input data is used as an address in step S42 to read the γ characteristic value at the time of negative output from the negative characteristic ROM 25 and set it in the γ-RAM6. On the other hand, if positive, step S4
In 3 the input data is used as an address and the γ characteristic value at the time of positive output is read from the positive characteristic ROM 24 and set in the γ-RAM 6.
After the .gamma.-RAM6 is set, the copy of the original is executed in step S44, the predetermined number of sheets is counted by step S45, and the process is finished after the predetermined number of sheets is copied.

If the negative γ characteristic value is not one,
The tone can be adjusted during negative output. In this case, it is convenient to give a plurality of positive γ characteristic values and switch to tones corresponding to each other. Further, the black image data 3FH and the white image data 00H are associated with the negative γ characteristic value, but it may be preferable to associate 3FH with 0FA, for example.

Further, in this embodiment, the negative characteristic ROM 25 and the positive characteristic ROM 24 are used, but these are RAMs, and a configuration in which the characteristic can be set is also conceivable.

Furthermore, in the present embodiment, the γ conversion is described, but the idea of the present invention can be effectively used in other digital conversions. Also, the recording portion is irradiated with a laser and developed with toner,
Although the image scanning and reversal development system has been described, a similar effect can be obtained in a background ground scanning and regular development system in which a white background portion is irradiated with a laser and a non-irradiated portion is developed with toner.

[Effects of the Invention] As described above, according to the present invention, when an image is formed by irradiating a recording medium with a laser, there is a difference in the light amount distribution when the laser is turned on for a predetermined time and when it is turned off. Regardless, the widths of the lines on the output image can be made substantially equal, and good positive image output and negative image output can be performed.

[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 a characteristic diagram of .gamma.-RAM at the time of negative output, and FIG. 3 (b). Is a characteristic diagram of γ-RAM at the time of positive output, and FIG. 4 is a flow chart of γ-RAM setting. 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 …… Positive / negative switch, 21 …… RA
M, 22 …… CPU, 23 …… Program ROM, 24 …… Positive characteristic R
OM, 25 ... Negative characteristic ROM.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukihiro Ozeki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Sasame 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Tetsuo Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inichiro Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-55-4071 (JP, A) JP-A-60-190072 (JP, A)

Claims (1)

[Claims] 1. A reading unit for converting a document into read image data, a conversion unit for converting the image data converted by the reading unit into reproduction image data, and reproduction image data converted by the conversion unit. Accordingly, a control unit that controls the laser lighting time, an image forming unit that reproduces the original by irradiating the recording medium with the laser, and a light amount when the laser is turned on for a predetermined time and turned off. Based on the difference in distribution, the conversion means is set to have conversion characteristics such that the line widths on the output image are substantially equal when the document is positively output by the image forming means and when it is negatively output. And an image processing apparatus.