JPH023350A - Laser exposure device - Google Patents

Abstract

PURPOSE:To discriminate the trouble of a laser beam source and an optical modulator easily by attenuating zero-order beams from an optical modulating means and providing a trouble detecting means detecting the power of laser beams by an output from a photo-detector receiving first-order beams and the attenuated zero-order beams. CONSTITUTION:An attenuating means 36 is composed of an attenuating lens, attenuates the power of zero-order beams up to an extent having no effect on the image of a photosensitive drum 4, and introduces the power to a reflecting mirror 31. A start stop detector 5 has a light-receiving area capable of detecting first-order beams and zero-order beams. The output level of the detector 5 between an alarm level V1 and an instantaneous interruption level V2 represents projection to the detector 5 of attenuated zero-order beams, laser beams are not modulated by the abnormality of a video data, an optical modulator driver 2a or an optical modulator 2 and only zero-order beams are output, and an alarm signal is output from a comparator 6a. When the output level of the detector 5 is brought to the instantaneous interruption level V2 or less, both zero-order beams and first-order beams are not projected to the detector 5, and the alarm signal is output from the comparator 6a and an instantaneous interruption signal from a comparator 6b by the instantaneous interruption of a laser tube 1.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figure 4) Means for solving the problem to be solved by the invention (Figure 1) Working example (a) 1 Description of embodiments (Figures 2 and 3) (b) Description of other embodiments Effects of the invention [Summary] Used in laser printers, etc., to expose the exposure surface with modulated laser light from a laser light source. Regarding laser exposure equipment, the purpose is to easily determine whether a failure is in the laser light source or the optical modulator. and a light modulation means for outputting the
In a laser exposure apparatus configured to irradiate the exposure surface with the primary light, attenuation means for attenuating the zero-order light from the light modulation means, and receiving the first-order light and the attenuated zero-order light. A photodetection element and a failure detection means for detecting the power of the laser beam output from the photodetection element are provided, so that it can be determined whether the failure is in the light source of the sea 4j' or in the light modulation means 2:). .

[Industrial application field]

The present invention relates to a laser exposure device used in a laser printer or the like, which exposes a laser beam surface with modulated laser light from a laser light source.

Laser exposure devices are widely used in laser printers that scan and expose a photoreceptor with Rayleigh light, and laser processing machines and Rayleigh inspection machines that scan laser light onto a processed surface or a surface to be inspected.

In such a laser exposure apparatus, when relevance is required, a high-power gas laser such as He-Ne or Ar is used instead of a low-power laser element such as a semiconductor laser.

In this laser exposure apparatus, the laser light output is stopped due to a failure in the laser optical system, so there is a need for a technique that can accurately detect the failure part of the laser optical system.

[Conventional technology]

FIG. 4 is an explanatory diagram of the prior art.

FIG. 4(A) shows a laser printer as a laser exposure device.

Laser light from the gas laser tube 1 enters an optical modulator (acousto-optic modulation element) 2.

The optical modulator driver 2a generates a modulation signal in accordance with the video signal (DEC), drives the optical modulator 2, and modulates the laser light from the laser tube 1.

As a result, when there is no modulation, it becomes 0th order light, and the shutter 3
Shielded by 0.

On the other hand, when there is modulation, it becomes primary light and the reflection mirror 31
The light enters the polygon (rotating) mirror 32 via the polygon mirror 32, is scanned by the polygon mirror 32, passes through the f-theta lens 33 and the folding mirror 111, and is irradiated onto the photosensitive drum 4, which is the irradiation surface.

At the left end or right end of the photosensitive drum 4, there is a reflective mirror 3 for detection.
5 is provided, and the scanning 1/-the light is reflected by the reflecting mirror 35.
It is configured so that it is reflected by the beam and hits a scan start detection element (fumetodetektor) 5.

As shown in FIG. 5(B), in the video disk, scan star 1 detection signals are provided on both sides of the print data for each scan cycle, and this causes the scan start detection element 5 to receive primary light during normal operation. is incident, and a scan start signal SS is obtained.

This scan start signal SS means that the photosensitive drum 4, which is the irradiation surface, is irradiated with laser light, and the laser power is checked based on the scan start signal.

In other words, if the scan start signal is generated every regular period, the laser beam has reached the irradiated surface, and if it is not generated, the laser beam has reached the irradiated surface and is not there, so the laser optical system It was determined that this was a malfunction.

[Problem to be solved by the invention]

However, with conventional technology, only the primary light of the laser beam is detected, so it is only possible to check whether the primary light of the laser beam has reached the irradiated surface or not, and if laser beam #1 has caused a problem. What is there is the optical modulator 2 and its driver 2a.
There was a problem in that it was not possible to determine whether a fault was occurring, and when a fault was detected, all of its parts had to be replaced.

Therefore, an object of the present invention is to provide a laser exposure apparatus that can easily determine whether a failure occurs in the laser light source or the optical modulator.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

The present invention includes a laser light source 1 and a light modulating means 2 that modulates the laser light of the laser light source 1 with a modulation signal and outputs zero-order light and first-order light, and directs the first-order light onto an exposure surface 4. In the laser beam exposure apparatus configured to emit laser light, attenuation means 36 for attenuating the zero-order light from the light modulation means 2, and a photodetection element 5 for receiving the first-order light and the attenuated zero-order light. , the optical detection 1[i
A failure detection means 6 for detecting the power of the laser beam output from the element 5 is provided, so that it can be determined whether the failure is in the laser light source 1 or in the light modulation means 2.

[Effect]

In the present invention, the check is performed so that the primary light also enters the photodetector element +i2). In this case, since the zero-order light hits the irradiation surface 4 and the modulation is not sloppy, the intensity of the zero-order light is weakened by the attenuating means 3 before irradiation.

In other words, if there is a failure in the laser light source, neither the first-order light nor the zero-order light is output, so the output from the photodetector element 5 cannot be changed.Conversely, even if the laser light source is normal, if the luminous intensity 1i11 unit 2 does not perform modulation due to a failure, the 0th-order light is output. Since only light is output, the output from the photodetection element 5 is low due to the effect of the attenuation means 36. If both are normal, the output of the photodetection element 5 will be a dog, so this level difference will cause the failure detection means to 6 can determine the faulty part.

〔Example〕

(a) Description of one embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention.

In the figure, the same components as those shown in FIGS. 1 and 4 are indicated by the same symbols, and 6a is a first comparator, which outputs a scan start signal SS and an alarm level V. 6b is a second comparator, which compares the scan start signal SS and instantaneous interruption level Vz (
V, <y), and when the signal SS is below the instantaneous interruption level V2, a laser instantaneous interruption signal is generated.

The attenuating means 36 is composed of an attenuating lens, is provided between the light modulator 2 and the refracting mirror 31, and attenuates the power of the zero-order light to an extent that it does not affect the image on the photosensitive drum 4. 31.

The start/stop detection element 5 has an appropriate light-receiving area for detecting the first-order light and the zero-order light through the reflection mirror 35, and is provided at a position where either the first-order light or the zero-order light is incident.

FIG. 3 is an explanatory diagram of the operation of one embodiment of the present invention, and shows a waveform obtained by the scan start detection element 5.

When both the laser tube 1 and the optical modulator 2 are normal, the primary light enters the detection element 5 due to modulation, and its level is S.
S, which is higher than the alarm level ■. Conversely, the alarm level V is set lower than the output level SS of the detection element 5 during normal operation.

Therefore, neither an alarm signal nor a momentary interruption signal is output from both comparators 6a and 6b.

On the other hand, the output level of the detection element 5 is as shown in FIG.
, between the alarm level ■1 and the instantaneous interruption level V2, which indicates that the attenuated zero-order light is incident on the detection element 5.

At this time, there may be an abnormality in the video data, or the optical modulator driver 2
3 or an abnormality in the optical modulator 2, indicating that the laser beam is not modulated and only the zero-order light is output, and an alarm signal is output from the comparator 6a.

Therefore, it can be determined that there is an abnormality in the optical modulator 2, the F lime 2a, or the video data.

Furthermore, the fact that the output level of the detection element 5 is below the instantaneous interruption level (■2) means that neither the zero-order light nor the first-order light is incident on the detection element 5.

At this time, the laser tube 1 is momentarily cut off and no laser light is generated, and an alarm signal is output from the comparator 6a and a momentary cutoff signal is output from the comparator 6b.

Therefore, it can be determined that there is a momentary interruption of the laser tube 1.

This check and check need not be performed all the time, but may be performed at the timing of the scan start detection signal shown in FIG. 4(B).

In this way, the zero-order light is attenuated through the attenuation lens 36 and made incident on the photodetector element 5 without being blocked by a shutter, without affecting the scanning of the first-order light on the irradiation surface. , it becomes possible to determine the degree of failure between the laser tube and the optical modulator.

(b) Description of other embodiments In the above embodiments, a laser printer was used as an example.
It can also be used in a laser reading device using a reading surface as an irradiation surface instead of a photosensitive drum, a laser processing machine using a processing surface, a laser inspection machine using an inspection surface, and the like.

Furthermore, scanning of the laser beam is not necessarily necessary, and the irradiation mechanism may be made movable to enable scanning.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, since the zero-order light is attenuated and made incident on the photodetecting element to determine a fault, the effect is that it is possible to easily determine a fault between the laser light source and the optical modulator. In addition to this, it also has the effect that the characteristics on the irradiated surface are not affected by the zero-order light, contributing to the investigation of the cause of failure of the laser exposure apparatus, and reducing the need for unit repair and replacement.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is an explanatory diagram of the operation of an embodiment of the present invention, and FIG. 4 is an explanatory diagram of the prior art. Laser light source, optical modulator, irradiation surface (photosensitive drum), photodetection element, fault detection means, 36-light attenuation means.

Claims (1)

[Claims] (1) A laser light source (1), which modulates the laser light of the laser light source (1) with a modulation signal, and
In a laser exposure apparatus including a light modulating means (2) for outputting secondary light and a primary light, and configured to irradiate the exposure surface (4) with the primary light, 0 from the light modulating means (2) is provided. Attenuation means for attenuating the next light (
(36), a photodetection element (5) that receives the first-order light and the attenuated zero-order light, and a failure detection means (6) that detects the power of the laser beam output from the photodetection element (5). ), and the laser light source (1
) or the light modulating means (2).