JPH07281112A - Image recorder - Google Patents

Abstract

PURPOSE:To provide an image recorder constituted so that plural exposure means are precisely aligned by simple control and an excellent image is recorded at a high speed. CONSTITUTION:A recording image is formed on a photosensitive drum 104 by laser beams outputted from two laser units 102 and 103. At this time, an interval between two laser beams on the drum 104 corresponds to time difference obtained when two laser beams are detected by beam detection substrates 105 and 106. By driving a motor 109 so that the time difference becomes a prescribed value, a laser unit fitting plate 110 is moved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording device such as a digital copying machine or a laser printer having an image writing means using a laser or the like.

[0002]

2. Description of the Related Art Conventionally, in this type of apparatus, an apparatus for exposing a photosensitive member with a laser or the like according to image data read from a scanner or input image data is generally known. Then, in order to operate these devices at a higher speed, it has been proposed to use a plurality of laser exposure means.

[0003]

However, in the case of providing a plurality of exposing means and operating them to increase the speed of the apparatus, it is necessary to accurately align the exposing means with each other to obtain a good image. The problem arises that you cannot get

An object of the present invention is to provide an image recording apparatus capable of accurately aligning a plurality of exposure means by simple control and recording a good image at a higher speed than in the past. is there.

[0005]

In order to achieve the above object, the present invention corresponds to first and second laser exposure means for forming a recorded image and the two laser exposure means. First and second laser light detection means,
Position adjusting means for adjusting the position of the laser exposure means, measuring means for measuring the time difference between the output signals of the first and second laser light detecting means, and the time difference is predetermined based on the output of the measuring means. And a control means for controlling the position adjusting means so that the value becomes a value.

[0006]

According to the present invention, the first laser light detecting means emits the laser light from the first laser light exposing means and the second laser light detecting means emits the laser light output from the second laser light exposing means. Respectively detect. The time difference between the two laser light detecting means detecting the laser light corresponds to the interval between the two laser lights when the two laser lights form an image. This time difference is measured using a measuring means. Then, the control means adjusts the position of the laser exposure means by using the position adjusting means so that this time difference becomes a predetermined value.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram best showing the features of the overall construction of the first embodiment of the present invention. The laser light generated by the laser units 102 and 103 is converted into parallel light by a collimator lens and a cylindrical lens (not shown). The parallel light then enters the polygon mirror 101 rotating at a constant speed. The laser light reflected by the polygon mirror 101 is focused on the photosensitive drum 104 by an imaging lens (not shown) arranged in front of the polygon mirror 101. Here, since the polygon mirror 101 is rotating at a constant speed, the laser light on the photosensitive drum 104 scans on the photosensitive drum 104 at a constant speed to remove the charge on the photosensitive drum 104.

When the photosensitive drum 104 is irradiated with laser light for one main scan in this way, a laser light irradiation start (horizontal synchronization signal) signal is required. This start signal includes a beam detection signal (hereinafter referred to as B
D signal) is used.

The laser light applied to the beam detection substrates 105 and 106 provided on the extension of the laser optical path is converted into an electric signal by a photodiode on the substrate and sent to the image processor circuit 107 as a BD signal.

The image processor circuit 107 outputs the digital image-processed image data to the laser driver circuit 108 as a laser drive signal at a timing based on the BD signal. The laser driver circuit 108 controls the two laser units 102 and 103 so that the output light amount of the laser becomes constant.

Further, 109 is a laser unit mounting plate 1
A motor that rotates 10 and is driven according to a rotation instruction determined by the image processor circuit 107 based on the two BD signals. In this way, the exposure positions of the two laser beams are finely adjusted.

Next, a method of adjusting the exposure position of the laser light will be described with reference to the schematic diagram of FIG. 2 and the time chart of the BD signal of FIG.

In FIG. 2, reference numerals 102 and 103 respectively denote laser units for emitting laser light, which are arranged on the mounting plate 110 at a distance d (about 100 μm). The laser light output from each laser unit must perform one scanning while maintaining a certain distance 1 in the sub-scanning direction on the photosensitive drum according to the target resolution. For example, at a resolution of 400 dpi, this distance l is 63.5 um. FIG. 2A is a diagram showing a case where the distance 1 on the photosensitive drum is larger than 63.5 μm. In such a case, as shown in FIG. By rotating the, the distance between the two lasers on the drum surface is 6
The laser exposure position must be adjusted so that it is 3.5 μm.

FIG. 3 is a time chart showing BD signals of the two lasers. As shown in FIG. 3, by rotating the mounting plate 110 of the laser, the time difference t between the BD signals (BDA, BDB) of each laser changes. This is taken out as a section signal and its time t
To measure. This measured time t corresponds to the distance between the lasers on the drum surface.

Next, the method for measuring the time difference t and the method for controlling the rotational position of the laser mounting plate will be described in detail with reference to the block diagram of FIG. 4 and the flowchart of FIG. Figure 4
FIG. 3 is a block diagram showing a configuration of a control device that controls a rotational position of a laser attachment plate. In FIG. 4, 111 is a CPU that controls the rotational position of the laser mounting plate 110.
Reference numeral 112 denotes a read-only memory (ROM) that stores a control procedure (control program) for the rotational position control,
The CPU 111 controls the rotational position of the laser mounting plate according to the control procedure stored in the ROM 112. Reference numeral 113 is a random access memory (RAM) which is a main storage device used as a storage area for input data, a work storage area, and the like. Reference numeral 114 denotes an I / O (input / output) port, which is an input interface for inputting count data of the counter circuit 116 and a stepping motor 119.
It is used as an output interface for outputting the drive signal of. Reference numeral 117 is a section signal generation circuit, which outputs B based on the beam detection signals BDA and BDB of the input laser light.
A section signal from the rising edge of DA to the rising edge of BDB is generated. Such a section signal generation circuit 117
It can be configured by a flip-flop circuit that operates at the rising edge of the input signal. The section signal is output to the counter circuit 116 as a count enable signal. Also.
A reference clock pulse (CLK) for counting is applied to the counter circuit 116 from, for example, a crystal oscillator. The CPU 11 reads the data counted by the counter circuit 116 and compares it with the count value written in the ROM 112 or the RAM 113 in advance. As a result of comparison, if the output value of the counter circuit is large, the CPU 111 outputs a drive pulse in the normal rotation (reverse rotation) direction of the stepping motor 109 to the motor driver circuit 115, and conversely, if the output value is small, it is in the reverse rotation (normal rotation) direction. Output drive pulse.

FIG. 5 shows the CPU 111 for the above operation.
It is a flow chart which shows the processing procedure which should be performed.

First, when there is an instruction from a key or the like on the operation unit (not shown), it is judged whether or not it is in the laser exposure position adjustment mode (step S1). Perform (step S11).

In the laser exposure position adjusting mode, the laser is turned on (step S2), and the count value X from the counter circuit 116 which is the time data of the section signal is read (step S3). When the count value X is read, the laser is turned off (step S4). Next, the count value Xref serving as a reference for the exposure position adjustment is read from the RAM or ROM (step S5), and X and Xre are read.
f is compared (step S6). As a result of the comparison, the number of pulses Y of the stepping motor corresponding to the difference is searched from the data table stored in the ROM in advance (step S7). When X and Xref are compared (step S8), and if X is larger than Xref, the stepping motor is driven by Y pulses in the forward rotation direction (step S9).
If it is small, the stepping motor is driven in the reverse direction by Y pulses (step S10). With such a procedure, the exposure positions of a plurality of lasers can be adjusted accurately.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. In the first embodiment, the laser light detecting means is provided for each of the plurality of lasers, but it is desirable to avoid providing a plurality of laser light detecting means in view of the space of the apparatus or cost reduction. Therefore, in this embodiment, the exposure position of the laser is adjusted by using only one laser light detecting means.

FIG. 6 is a block diagram showing the overall construction of this embodiment having one laser light detecting means. 6, the same reference numerals as those in FIG. 1 denote the same elements.

The configuration of the control device for the laser mounting plate 110 in this embodiment is almost the same as the configuration of the control device shown in FIG. 4, but the configuration of the part for generating the section signal is different.
FIG. 7 is a block diagram showing the configuration of the section signal generation circuit in this embodiment, and FIG. 8 is a time chart showing the output waveform of each part thereof.

In FIG. 7, both the laser beams A and B are photoelectrically converted by the photodiode in the beam detection substrate 105 and output to the comparison circuits 119 and 120. This a
The input waveform of the point is a in FIG. 8 when only the laser A emits light.
(A), and when only the laser B emits light, it becomes as shown in (a) of FIG. When both lasers A and B emit light, the waveform shown in a of FIG. 8 is obtained by adding the voltages of the two waveforms. This a of FIG.
The voltage having the waveform shown in (2) is input to the two comparison circuits 119 and 120.

Further, the constant voltage V _{1 of the} level shown in FIG. 8A is input to the other input of the comparison circuit 119, and the level shown in FIG. 8A is input to the other input of the comparison circuit 120. The constant voltage V _{2 of} is input. Here, the comparison circuit 119
From the rising edge of the output of FIG.
The time t to the rising edge of the output of 20 (c in FIG. 8) corresponds to the distance between the lasers on the photosensitive drum surface.
The output signals of 19 and 120 are input to the flip-flop 121. The output signal of the flip-flop 121 is d in FIG.
Becomes the waveform of. Then, this signal is output as a section signal to the counter circuit 116 of FIG. 4, and the pulse width thereof is measured.

Subsequent processing is the same as that of the first embodiment, and therefore its explanation is omitted. In this way, the exposure position of the laser can be adjusted.

[0026]

As described above, according to the present invention,
The exposure position of the laser can be adjusted accurately by simple control, and a good image can be recorded.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a first exemplary embodiment of the present invention.

FIG. 2 is an explanatory view showing the principle of the laser exposure position adjusting method of the present invention.

FIG. 3 is a time chart for explaining a laser exposure position adjusting method in the first embodiment.

FIG. 4 is a block diagram showing a configuration of a position control device for laser exposure means in the first embodiment.

FIG. 5 is a flowchart showing a procedure to be processed by the CPU of the position control device.

FIG. 6 is a block diagram showing an overall configuration of a second exemplary embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a section signal generation circuit according to a second embodiment of the present invention.

8 is a time chart showing an output state of each section of the section signal generation circuit shown in FIG.

[Explanation of symbols]

 101 polygon mirror 102, 103 laser unit 104 photosensitive drum 105, 106 beam detection substrate 107 image processor circuit 108 laser driver circuit 109 motor 110 laser unit mounting plate 111 CPU 112 ROM 113 RAM 114 I / O port 115 motor driver circuit 116 counter circuit 117 section signal generation circuit 119, 120 comparison circuit 121 flip-flop circuit

Claims (2)

[Claims] 1. A first and a second laser exposure device for forming a recorded image, a first and a second laser light detection device corresponding to each of the two laser exposure devices, and the laser exposure device. Position adjusting means for adjusting the position, measuring means for measuring the time difference between the output signals of the first and second laser light detecting means, and the time difference so as to become a predetermined value based on the output of the measuring means. An image recording apparatus, further comprising: a control unit that controls the position adjusting unit. 2. A first and second laser exposure means for forming a recorded image, a laser light detection means for detecting laser light from the two exposure means, and the first and second laser exposure means. Position adjusting means for adjusting the position of the means, first comparing means for comparing the output signal of the laser light detecting means and a first reference potential, output signal of the laser light detecting means and a second reference potential And second measuring means for comparing the time difference between the output signal of the first comparing means and the output signal of the second comparing means, and the time difference based on the output of the measuring means. And a control means for controlling the position adjusting means so that the value becomes a predetermined value.