JPS62235865A - Image recorder - Google Patents

Abstract

PURPOSE:To improve quality of a recorded image in an electrophotographic image recorder using a fine beam Iight source such as laser beams by controlling the exposure time per picture element in response to the distribution of the sensitive characteristic deviation of a photosensitive body. CONSTITUTION:An optical slit 4 is disposed before a lens 5, and the cosine four-production of the lens 5 and the sensitive characteristic deviation in the bus line direction of the photoshnsitive body (drum) 14 are simultaneously corrected. Since the more sensitive part of the photosensitive body 14 requires a low exposure quantity, the width of the slit 4 is narrowed to control Iight so that less light can be irradiated to a CCD 5. Whereas the less sensitive part of the photosensitive body 14 requires a greater exposure quantlty than the prescribed one, the width of the slit 4 is expanded to control light so that more light can be irradiated to the CCD 5. Thus the CCD 5 can obtain an picture signal corrected by the deviation of the sensitive characteristic distribution of the photo sensitive body 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic image recording apparatus having a copying function in combination with a document reading device.

(Conventional Apparatus) FIG. 2 shows a JIi diagram of a basic configuration example of the main body of a conventional image recording apparatus of this type. Reference numeral 14 denotes an electrophotographic photoreceptor (drum) having a photoconductor such as amorphous Se, amorphous Si, 0PC (4R optical semiconductor), CCTs, etc., and can rotate in the direction of the arrow in the figure. A primary charger 15 uniformly charges the surface of the photoreceptor drum 14 in a positive manner by positive corona discharge to ensure the first molding. 13
is a half-four-body laser for exposure, and is configured to blink in response to an image electric signal. The light emitted from this conductor laser 13 is turned into parallel light by a collimator lens 16, rotated and scanned by a polygon mirror 17, and is imaged on the surface of the photoreceptor drum 14 by an imaging lens 18. .

Instead of the above-mentioned i-conductor laser 13, He-No or Ni-
A gas laser such as a Cd laser may be used, and a galvanometer mirror or a hologram film may be used instead of the polygon mirror 17 for optical scanning.

The electrophotographic photoreceptor used for the photoreceptor drum 14 tends to have non-uniform photographic characteristics (photosensitive characteristics) in the circumferential direction of the drum or in the direction of the generatrix, and particularly in relation to the manufacturing method, the electrophotographic photoreceptor tends to have non-uniformity in the direction of the generatrix. There is a tendency for this to happen. Among these photosensitive characteristics, a deviation in the charging ability in the generatrix direction appears as a change in the dark potential vo, and a deviation in sensitivity in the generatrix direction appears as a difference in the bright potential vL. when high/low, vL is low/high).

Broadly speaking, these characteristics can be classified into five types. That is, as shown in FIGS. 3(a) to 3(d), each surface potential characteristic curve in the generatrix direction of the photoreceptor drum is shown as follows: l) dark area potential vn, bright area potential v1. Both, back 11 in the generatrix direction
11 (on the left side of the photoreceptor drum in Figure 2) and on the front side (1 on the right side in the same figure)
[! 1) (each parallel to the horizontal axis of FIG. 3, not specifically shown).

2) The dark area potential VD is uniform, but the bright area potential VD slopes upward and downward towards the front side (Figure 7i3 (a))
.

3) The dark area potential VD rises and slopes toward the front side, and the bright area potential vI is uniform (FIG. 3(b)).

4) Dark area/bright area potentials VD/VL are the same towards the front side.
F is inclined in the descending direction (Fig. 3 (C)).

5) Both the dark area/light area potentials vD/vL are inclined towards the front side, or the respective slope directions are opposite to the rising/F falling direction (Fig. 3(d)).

Note that the dotted line curves in FIGS. 3(b) to 3(d) will be described later.

On the other hand, there are regular development and reversal development as developing methods for visualizing the electrostatic latent image obtained by exposing the photoreceptor drum. The slope appears as a difference in the appearance of what can be called "fogging" between the back side and the front side, and the slope of the bright area potential vL appears as a difference in density or line width of the image. On the other hand, in the case of regular development, the above VO/v
The influence of the L characteristic is opposite to that in the case of reversal development, and the dark area potential V. The above-mentioned slope appears as a difference in image density or line width, and the slope of the bright area potential vL appears as a difference in the appearance of "fogging" in the above-mentioned direction.

Therefore, in either case of reversal development or regular development, the dark area/light area potential Vl)/j1. It is desirable for both partners to minimize the inclination in the generatrix direction.

As a countermeasure for this, for example, the slope of the bright area potential v0 is
One charger! Correction can be made by tilting the distance between the discharge 1 m (wire) of No. 5 and the surface of the photosensitive drum 14 with respect to the back side and the front side of the drum. With this method,
Characteristic curves obtained when the slope of the dark potential v0 curve is corrected are shown by dotted lines in FIGS. 3(b) to 3(d), respectively. However, when the dark area potential v0 characteristic is corrected by the above method, it is naturally affected by the bright area potential vL characteristic and changes accordingly. For this reason, for example, in FIG. 3(b), when the dark potential Vo is corrected, the bright potential vL characteristic, which was flat, becomes sloped, and in FIG. 3(C), the bright potential vL is also slightly corrected. It becomes a trend. In addition, in figure (d), along with the correction of the dark area potential v0, the bright area potential v
The L characteristic deteriorates (the slope increases).

On the other hand, regarding the bright area potential V and characteristic correction +E described in 1.D., in an ordinary electrophotographic copying machine with a wide width of image exposure, a slit is installed in the optical path to correct the exposure amount. , tilr#, thereby adjusting the bright area potential vL. However, in this type of electrophotographic image recording device that uses laser light, the beam diameter is approximately 100 μm.
The slits are so minute that correction using the slits is impossible. For this reason, if exposure correction is performed using a slit at a position where the beam diameter is large before the laser light focuses on the photoreceptor, the imaging beam diameter will become sharp due to the diffraction phenomenon, resulting in a decrease in resolution. Undesirable.

In addition, it is impossible to correct the bright area potential vL characteristic by changing the laser light intensity with a gas laser such as He-Ne, and even with a semiconductor laser, the current and light intensity characteristics of the laser element are steep. Therefore, it is practically impossible.

(Problem to be solved by the invention) For this reason, in the past, the dark area/bright area potential VD/VL
Primary charge 3i! so that the characteristic curves each have an acceptable slope. By adjusting the height of the discharge line (wire) of lls, it was necessary to accept changes in the rJ) line direction of the degree of "fogging" and changes in the density of the formed image to some extent. Alternatively, there is a problem in that the above-mentioned characteristics have to be selected, taking into account problems during the manufacturing process, so that they have an acceptable and appropriate slope.

The present invention has been made in view of the problems of the prior art as described below, and it corrects deviations in the sensitivity characteristic distribution of a photoreceptor in an image recording apparatus that uses a laser as an exposure source.
The objective is to make it possible to obtain high-quality recorded images without "fogging" or deviations in image density.

c. Means for Solving Problems] For this reason, in the present invention, the original reading device is provided with a deviation distribution correction device for the sensitivity characteristics of the photoreceptor, and the device corrects the deviation distribution of the sensitivity characteristics of each part of the photoreceptor. , this object is attempted to be achieved by configuring the exposure time of the laser beam to be varied.

[Effect]

With the configuration described below, the exposure time of each part on the photoconductor is controlled in response to the distribution of the sensitivity characteristic deviation of the photoconductor, so the sensitivity characteristic deviation is corrected, and "fogging" and density differences are eliminated. High-quality recorded images can be obtained.

(Examples) The present invention will be described below based on Examples. In Figure 1,
A block diagram of an embodiment of each pixel exposure aperture correction circuit according to the present invention is shown.

(Structure/Operation) 1 is an image reading device for reading a document and transmitting an image signal, and 2 is an electrophotographic (image) recording device. In the image reading device W11, the original (
(not shown) is imaged by the lens 5 onto a charge-coupled device (CCD) 6' that is synchronized with the image clock φ.

An optical slit 4 is disposed in front of the lens 5, and performs cosine fourth power correction of the lens 5 and correction of sensitivity characteristic deviation in the generatrix direction of the photoreceptor (drum) 14 at the same time.

That is, since the high-sensitivity portions of the photoreceptor 14 may be exposed to a small amount of light, the width of the slit 4 is narrowed to control the CCD 5 to be irradiated with a small amount of light. Since the low-sensitivity portions of the photoreceptor 14 require a larger amount of exposure than the predetermined amount, the width of the slit 4 is increased to control the CC 55 to be irradiated with a larger amount of light than the predetermined amount. Please, CC
At D5, an image signal is obtained in which the deviation of the sensitivity characteristic distribution of the photoreceptor 14 has been corrected. Image No. 18 obtained on the CCD 5 is an analog-digital (A/D) variable 111F.
%7, it is converted into a digital signal and sent to the image processing section 8.
Then, various processes such as masking, trimming, scaling, and negative/positive inversion are performed.

The image signal processed by the image processing unit 8 is, for example, 6 bi
The image signal is sent to the electrophotographic recording device 2 in the form of an image signal having multi-bit density data such as t or 8 bits. That is, when the signal is 6 bits, one pixel has density information of 64 gradations, and when the signal is 8 bits, it is transmitted with density information of 256 gradations.

In the electrophotographic recording device 2, the following processing is performed.

That is, an image signal manually input as bit information is converted into an analog signal by a digital-to-analog (D/A) converter 9. The signal is then compared by a comparator 1 with a signal from a waveform generator 10 that generates a triangular wave signal in synchronization with the image clock (pixel clock) φ. Note that the period of the triangular wave generated from the waveform generator 10 may correspond to, for example, three pixels. Here, the density information such as the 64 gradations or 256N gradations is converted into the length of the pulse width (pulse width modulation signal). □ Waveform generator! In addition to the triangular wave, the output of 0 can also be used with waveforms such as sawtooth, trapezoidal, or sine waves.

Here, the image correlation ratio lIl:J4 is modulated into a pulse width, and the laser driver 12 controls the lighting of the semiconductor laser 13.

The image signal from the image reading device 1 also contains corrections for the sensitivity characteristics of the photoreceptor 10, so that it is pulse width modulated and the lighting time of the semiconductor laser 13 is changed to The light is turned on for a longer time than the predetermined time in the normal sensitivity part, and the light is turned on for a shorter time than the above predetermined time in the high sensitivity part of the photoreceptor 10. As a result, the photoreceptor (drum) IO has an actual amount of exposure for each pixel. Since the correction is performed, the value of the bright area potential vL can be made substantially uniform.

(Other Embodiments) FIG. 4 shows a circuit block diagram of another embodiment. This embodiment is based on the optical slit 4 in the first embodiment (FIG. 1).
Instead, a shading correction circuit 19 and a photoreceptor sensitivity correction circuit 20 are provided. Same as Figure 1 (equivalent)
Components are represented by the same reference numerals, and duplicate explanations will be omitted.

The shading correction circuit 19 has a cosine 4 of the lens 5.
Multiplication correction and sensitivity correction of the CCD 6 are performed. The photoreceptor sensitivity correction circuit 20 includes, for example, a table, and converts the characteristics of an input image signal. In addition, the photoreceptor sensitivity correction circuit transfers the sensitivity characteristic information of the photoreceptor IO to a digitizer or ROM.

It is also possible to form a predetermined diple manually using an IC card or the like. This allows the photoreceptor to be exposed from the outside.
The human effort required to correct the sensitivity characteristics of O is simplified.

In addition, the shading correction circuit 19 and the photoreceptor sensitivity correction circuit 20 may have the same function, which facilitates simple integration of the circuits and eliminates the need for sensitivity correction by functional configuration, resulting in a simple structure. , and the cost associated with this can be reduced.

In the embodiment described above, correction of the sensitivity characteristic deviation in the generatrix direction of the photoreceptor drum IO is described, but correction in the circumferential direction of the drum is also possible based on the same principle.

〔Effect of the invention〕

As described above based on the embodiments, according to the present invention, the exposure time for each pixel is controlled in response to the distribution of the sensitivity characteristic deviation of the photoreceptor. Even in electrophotographic image recording devices that use fine beam light sources, it is now possible to correct deviations in the sensitivity characteristics of the photoreceptor, expanding the range of photoreceptor selection and use, and eliminating problems such as "fogging" and image density differences. By correcting this, we were able to improve the recorded image quality.

In addition, since the sensitivity correction of the photoreceptor can be handled at the same level as the multivalued image signal within the image reading device, the configuration can be simplified.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of each pixel exposure amount correction circuit according to the present invention, FIG. 2 is a configuration example of an electrophotographic image reading device, and FIGS. 3(a) to 3(d) are: Each surface potential characteristic curve of the photoreceptor in the photoreceptor drum generatrix direction, FIG. 4 is a circuit block diagram of a second embodiment of the present invention. 1 ------- Image reading device 2 ------- Electrophotographic image recording device 8 -------
Image processing device t o ------- Waveform generator 13 -------
- Semiconductor laser V 1) -------*Dark potential V , -, -, Bright potential

Claims (1)

[Claims] In an electrophotographic image recording apparatus comprising a document reading device for transmitting an image signal, and a recording means for recording an image by scanning a photoreceptor with a laser beam modulated by the image signal, By providing the apparatus with a sensitivity characteristic deviation correction means for the photoreceptor, the exposure time of the laser beam based on the image signal is changed in response to the distribution of the sensitivity characteristic deviation for each part of the photoreceptor. An image recording device characterized by: