JPS63123067A - Image recording device - Google Patents

Abstract

PURPOSE:To make longitudinal and lateral light beams to be exposed constant in width and to form an output image of high quality by correcting the pulse width of a modulating signal based on the shape of the light beam to which a photosensitive body is exposed. CONSTITUTION:Terminals (a)-(c) of a switch 2 are changed over according to the shape of the laser light emitted by a semiconductor laser, a pulse generator 3 generates a pulse signal 3a with prescribed time width in synchronization with the rising of the modulating signal 1 outputted by a CPU 12 based on an image signal, and a new modulating signal M1 is outputted to a laser drive circuit 13 through an inverter circuit 4 and an AND gate circuit 5. Further, a pulse signal generator 6 generates a pulse signal 6a with prescribed time width in synchronism with the falling of the modulating signal 1 and a new modulating signal M2 is outputted to the laser driver circuit 13 from an OR gate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording device that records an image in accordance with an image signal on a recording medium by turning on and off a light source.

[Conventional technology]

The image information is recorded by modulating a light beam with image information conventionally sent out from an electronic computer, etc., and scanning the modulated light beam onto a recording medium using an optical element such as an optical deflector and lens. devices have been developed.

FIG. 4 is a configuration diagram of a laser beam printer, which is an example of a conventional image recording device. Reference numeral 11 denotes an image input terminal, which receives an image signal sent from an external device such as a host computer, and connects a signal line 11a. image signal via CP
Send to U12. 13 is a laser driver, which is a laser generator 1 composed of a semiconductor laser based on an image signal.
A drive signal for on/off modulation of 4 is generated.

A scanner motor 15 rotates a rotating polygon mirror 16 at a constant speed.

Reference numeral 17 denotes an imaging lens having fθ characteristics, which horizontally scans the photosensitive drum 18 with a laser beam deflected by the polygon mirror 16 . 19 is a beam detector that detects the deflected laser beam in front of the image writing position and sends an image writing start signal (BD double signal) to the CPU 12. 20 is a recording paper that detects the laser beam formed on the photosensitive drum 18 by the laser beam A toner image whose latent image is developed by a known electrophotographic process is transferred and fixed.

In this type of recording device, the laser beam emitted from the laser generator 14 is approximately 100 gm, and the laser beam is emitted from the photosensitive drum 18.
is imaged.

[Problem that the invention seeks to solve]

However, the size and shape of the laser beam differ from the laser generator 14. Polygon mirror 16. It varies depending on variations in the imaging lens 17, etc., errors in the arrangement position, etc. In particular, variations in the shape of the laser beam cause the output image on the recording paper 20 to appear as shown in Fig. 5 (a).
) to (C) occur.

5(a) to (C) are schematic diagrams for explaining the relationship between the shape of the laser beam and the output image form. In FIG. 5(a), 21 is a laser beam, and the irradiation of the laser beam A horizontal image 22 and a vertical image 23 are formed. In the same figure (b), 24 is a laser beam, which shows a case where the beam width is shorter in the horizontal direction than the laser beam 21, 25 is a horizontal image by the laser beam 24, and 26 is a vertical image by the laser beam 24. In the image (C), 27 is a laser beam, which is shorter in the vertical direction than the laser beam 21, and 28 is a laser beam.
29 shows a horizontal image formed by the laser beam 27, and 29 shows a vertical image formed by the laser beam 27.

As can be seen from these figures, when variations occur in the shape of the laser beam 2] as in the case of the laser beam 24 or the laser beam 27, the effect appears in the middle of one pixel in the output image, and as shown in Fig. 5(b). As shown in FIG.
The width of the image may be reduced as shown in Figure 5 (c).
As shown in FIG. 2, there are problems in that the vertical image 23 becomes an image with an extended width like the vertical double image 29, resulting in an image with extremely low image quality.

For this reason, attempts have been made to make only the horizontal or vertical line width constant by adjusting the amount of laser light, but it is currently technically very difficult to make the line width constant both in the vertical and horizontal directions.

Therefore, conventionally the semiconductor laser 14. polygon mirror 16
．． Improvements have been made by machining and assembling precision of the imaging lens 17 and their positional relationships, but there is a limit to such mechanical precision, and pursuing it will actually accelerate cost increases. It could become a problem.

Furthermore, in recent years, the above-mentioned laser beam printer has begun to be used as a lower-order output device for edited printing plates or as an output device for Japanese word processors, and the demand for high image quality has become stronger. The problems described above degrade the output image.

This invention was made to solve the above problems, and by varying the exposure time of the light beam in the middle of one pixel according to the shape of the light beam, it is possible to always use the light beam regardless of the shape of the light beam. An object of the present invention is to obtain an image recording device that can form a high-quality output image with a constant width.

[Means for solving problems]

The image recording apparatus according to the present invention is provided with a correction means for correcting the pulse width of the modulation signal based on the shape of the light beam that exposes the photoreceptor.

[Effect]

In this invention, the correction means corrects the pulse width of the modulation signal based on the shape of the light beam that exposes the photoreceptor.

〔Example〕

FIG. 1 is a block diagram illustrating a pulse correction circuit of an image recording apparatus showing an embodiment of the present invention. Reference numeral 1 indicates a modulation signal based on an image signal, which is output from the CPU 12. In FIG. A switch 2 switches terminals a to c according to the shape of the laser beam emitted from the semiconductor laser 14. A pulse signal generator 3 generates a pulse signal 3a having a predetermined time width t1 in synchronization with the rise and fall of the modulation signal 1 output from the CPU 12. 4 is an inverter circuit which inputs an inverted pulse signal 4a obtained by inverting the pulse signal 3a to one side of the AND gate circuit 5. The modulation signal 7 is directly inputted to the other side of the AND gate circuit 5, and the two are ANDed, and a new modulation signal M1 is output to the laser driver circuit 13. 6
A pulse signal generator generates a pulse signal 6a having a predetermined time width t2 in synchronization with the fall of the modulation signal 1 output from the CPU 12. 7 is an OR gate circuit, and modulation signal 1
and the pulse signal 6a output from the pulse signal generator 6, and output a new modulation signal M2 to the laser driver circuit 13.

FIGS. 2(a) and 2(b) are timing charts illustrating signals of each part in FIG. 1, and the same signals as those shown in FIG. 1 are given the same reference numerals.

Next, the pulse width correction operation according to the present invention will be explained with reference to FIGS. 3(a) to 3(C).

FIGS. 3(a) to 3(C) are diagrams for explaining the pulse width correction operation according to the present invention, and the same parts as in FIGS. 1 and 5 are given the same reference numerals.

In the figure (a), 21 is a laser beam, and the ratio of length to width is 1.0 to 1.2.

In the same figure (b), 8 is a laser beam, and is comprised with the ratio of length and width of 0.7-1.0. In the same figure (C), 9 is a laser beam, and the ratio of length and width is 1.2 to 1.5.
It consists of

When the shape of the laser beam is the laser beam 21 shown in FIG. 13, and the horizontal image 22. A vertical image 23 is formed.

When the shape of the laser beam is the laser beam 8 shown in FIG. The pulse signal 3a is generated at the timing shown in FIG. input.

Since the modulation signal 1 is input to the other side of the AND gate circuit 5, the modulation signal M1 shown in FIG. 3(b) whose pulse width has been corrected is input to the laser driver circuit 13. Thereby, it is possible to generate a vertical image 8b that is the same as the horizontal image 8a.

When the shape of the laser beam is the laser beam 9 shown in FIG.
The pulse signal 6a of 2 is outputted from the pulse signal generator 6 to the OR gate circuit 7, and the OR of both is taken and the modulated signal M
2 will be input to the laser driver circuit 13.

Thereby, a vertical image 9b having the same width as the horizontal image 9a can be generated. According to experiments, the ratio of the length and width of the laser beams 8 and 9 in FIG. 3 is within the range of 0.7 to 1.0.
．． 2 to 1.5, the predetermined time width tl, t2 shown in FIGS. 2(a) and (b) is 20% of the pulse width equivalent to one pixel.
When I did this, the vertical and horizontal images were almost the same thickness. From this, when the vertical and horizontal lengths of the laser beam are larger than these values, the predetermined time width t1. It is sufficient to set t2 large.

In the above embodiment, an image exposure method in which a portion irradiated with a light beam is developed is explained as an example, but the present invention can also be applied to a background exposure method in which a non-image area is exposed. In this case, the relationship between the light beam shape and the line widths of the vertical lines and horizontal lines of the output image is opposite to that of the image area exposure method.

Therefore, the pulse width can be corrected by setting the correction direction to plus and minus to the opposite direction.

〔Effect of the invention〕

As explained above, the present invention includes a correction means for correcting the pulse width of the modulation signal based on the shape of the light beam that exposes the photoreceptor, so no matter what shape of the light beam is exposed, the vertical The line widths of lines and horizontal lines can be made the same, and high-quality image formation can be performed. Furthermore, since the ratio of the line widths of the vertical lines and the horizontal lines can be set according to the user's preference, there is an advantage that an image of an intended image can be formed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating a pulse correction circuit of an image recording apparatus showing an embodiment of the present invention, FIG. 2 is a timing chart illustrating signals of each part in FIG. 1, and FIG. A diagram explaining the pulse width correction operation, FIG. 4 is a configuration diagram of a laser beam printer showing an example of a conventional image recording device, and FIG. 5 is a schematic diagram explaining the relationship between the shape of the laser beam and the output image form. be. In the figure, 1 is a modulation signal, 2 is a switch, 3.6 is a pulse signal generator, 4 is an inverter circuit, 5 is an AND gate circuit, and 7 is an OR gate circuit.

Claims (2)

[Claims] (1) In an image recording device that forms an image by exposing a photoconductor with a light beam signal modulated by a modulation signal corresponding to image information, the modulation signal is based on the shape of the light beam that exposes the photoconductor. An image recording apparatus comprising a correction means for correcting the pulse width of the image recording apparatus. (2) The image recording apparatus according to claim 1, wherein the correction means determines the amount of correction of the pulse width of the modulation signal based on the ratio of the length and width of the light beam shape. .