JPS6123375A - Laser scanning apparatus - Google Patents

Abstract

PURPOSE:To eliminate the risk of the laser beam damaging the human body when a laser scanning apparatus is inspected, by providing a light-emission suspending means which detects abnormality related to the scanning with a laser beam and suspends the emission of light by a laser source. CONSTITUTION:An abnormality detecting part 2 serving as a light-emission suspending means drives a timer every time a synchronous detection signal from a synchronous detector 8 is inputted thereto. In this case, the time (t) set in the timer is slightly longer than the time required for the scanning light to scan across a recording member 7. When the scanning system has no abnormality, the scanning period is repeated within the set time (t) for each scanning. If there is abnormality, the laser beam is not applied to the synchronous detector 8 even after the set time (t) has elapsed. In such case, when the output is suspended due to the expiration of the set time (t) of the timer, the abnormality detecting part 2 judges that an abnormal situation occurs, and generates a control signal for informing a DC power supply 1 of the occurrence of an abnormal situation. In response to the control signal, the power supply 1 suspends either or both of modulating functions of an optical modulator 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a laser scanning device, and more particularly to a laser scanning device that can be applied to a device that records information using laser light.

(Prior art) As a writing means for an image recording device using laser light,
Those using a He-Ne laser, a high-voltage power supply, an optical modulator, a rotating polygon mirror, etc. are known. In such conventional image recording devices, an error message is displayed when an abnormality occurs in the writing scanning system, such as out of synchronization in main scanning, abnormality in the laser emitting unit, abnormality in the rotating polygon mirror, or abnormality in the optical modulator. However, no measures have been taken to stop the generation of f-laser light.

Therefore, when inspecting the above-mentioned abnormality, there is a risk that the human body may come into contact with the laser beam or look directly at it, which is dangerous or harmful, which poses a problem.

(Objective) Therefore, an object of the present invention is to provide a laser scanning device having a function of stopping the generation of laser light when there is an abnormality in the scanning system.

(Structure) In order to achieve the above object, the present invention is characterized in that it includes a light emission stopping means that detects an abnormality in laser light scanning and stops the light emission of the laser light source.

Hereinafter, a detailed explanation will be given based on one embodiment of the present invention.

The figure shows a control system for a scanning system of an image recording apparatus.

The DC power supply 1 has a function of converting alternating current into direct current, and output to the high voltage power supply 3 is controlled on/off based on a control signal from the abnormality detection section 2. The high-voltage power supply 3 is a DC/DC converter, and supplies the power necessary to cause the laser light source 4 to emit light. The light source 4 is composed of, for example, a He--Ne laser tube, and emits a laser beam toward a rotating polygon mirror 5. The optical modulator 6 is disposed on the optical path of the laser beam from the light source 4 and in front of the rotating polygon mirror 5, and controls the laser beam on and off according to image information. Laser light that reaches the rotating polygon mirror 5 from the light source 5 via the optical modulator 6 is scanned onto the scanning surface of the drum-shaped recording medium 7 in accordance with the rotation of the rotating polygon mirror 5. In that case, the laser beam first irradiates the synchronization detector 8 and then scans the recording medium 7 for each scan. A synchronization signal from the synchronization detector 8 accompanying the laser beam irradiation is output to the write control section 9. The write control unit 9 drives the optical modulator 6 by synchronizing the image signal and the write clock so that the write start positions on the recording medium 7 are aligned.

The abnormality detection section 2 as a light emission stopping means according to the present invention drives a timer every time the synchronization detection signal from the synchronization detector 8 is input. Here, the set time t of the timer is set to be slightly longer than the time required for one scan of the scanning light over the recording medium 7. If there is no abnormality in the scanning system, the scanning cycle is repeated within a set time for each scan. If an abnormality occurs, the synchronization detector 8 may not be irradiated with laser light even after the set time t has elapsed. In this case, when the output stops due to the arrival of the timer set time t, the abnormality detection unit 2 determines that an abnormal situation has occurred, and sends a control signal to notify the abnormality to either the DC power supply 1 or the modulation function of the optical modulator 6. stop one or both. If the functions of both the DC power supply 1 and the optical modulator 6 are stopped, there is a low probability that both of them will become defective at the same time, thus providing a double safety device. The abnormalities handled in this example include stoppage of rotation of the rotating polygon mirror, abnormally low speed rotation, defective optical modulator,
Almost all abnormalities related to the writing system can be detected, such as a failure in the synchronization detector 5, an abnormality in the write control section 9, a failure in the light source 4, a failure in the high voltage power supply 3, etc.

When a semiconductor laser is used as the light source, the optical modulator 6 of the above example is not used, so it is sufficient to stop the light emission from the light source using a control signal from the abnormality detection section 2.

In addition to the above-mentioned embodiments, as a means for detecting an abnormality, it is also possible to determine an abnormality based on a decrease in the light intensity of the laser beam incident on the synchronization detector 8. For example, a comparator compares a signal detected by a photodiode with a reference voltage, and if the signal falls below a predetermined level, it is determined to be abnormal. In this case, the reference voltage is determined by paying attention to the recorded image density, which changes depending on the magnitude of the light intensity, and with reference to the photoelectric conversion voltage corresponding to the light intensity that does not cause abnormal image density.

The laser scanning device according to the present invention includes a printer, a copying machine,
In addition to being applicable to recording devices such as facsimile machines, the present invention can also be applied to reading devices. It goes without saying that the present invention can also be applied to a scanning device that uses a holo scanner instead of a rotating polygon mirror.

(Effects) In the present invention, if an abnormality occurs in the scanning system, the laser beam will not be emitted, so when an operator or service person performs an inspection, there is no risk of injury to the human body due to the laser beam, and it is safe. is secured and convenient.

[Brief explanation of drawings]

The figure is a block diagram of a scanning control system illustrating an embodiment of the present invention. 2... Abnormality detection section (as light emission stopping means).

Claims (1)

[Claims] In a laser scanning device that emits light from a laser light source toward a surface to be scanned via a scanning means,
1. A laser scanning device comprising: a light emission stopping means for stopping light emission of a laser light source in response to abnormality information related to laser light scanning.