JPS6247268A - Laser recorder - Google Patents

Abstract

PURPOSE:To easily control the output of a laser beam by providing a shielding means in the optical path of the laser beam and constituting so as to control the light shielding means, permitting the laser beam to pass through in the write period of an image and shielding it except that period. CONSTITUTION:A liquid crystal shutter 10 as the light shielding means is arranged in the beam optical path between the acoustic optical modulator 3 of a scanning optical system and an expandor lens 4. The liquid crystal shutter 10 is light shield-controlled by a control circuit 11. In other words, in an image write mode T, the liquid crystal 10 is opened, making pass the laser beam light modulated by a picture signal, and in the period other than the image write mode 7, the liquid crystal shutter 10 is closed, shielding the laser beam and detecting a light output in the period. the detection of a laser light output is performed by an optical detector, such as a photodiode, etc., controlling the light output of laser by a well known APC control circuit through a semiconductor laser driving circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a laser recording device that simplifies the control of the optical output of a semiconductor laser.

(Prior Art) Recently, a laser recording device (so-called laser printer) that records an image using a laser beam has been developed and put into practical use. A laser recording device modulates an I/-the beam with an electrical signal representing image information, forms image information on a photoreceptor with the laser beam, and records the image information as a visible image by electrophotographic processing or the like. FIG. 3 is a schematic diagram of a scanning optical system of this type of laser recording apparatus. The beam diameter of the laser beam generated from the laser tube l is expanded by the beam expander lens 2.4, modulated by an image signal by the acousto-optic modulator 3, and passed through the cylindrical lens 5 to a rotating polygon mirror (called a polygon). 6. The rotating polygon mirror 6 rotates at high speed to deflect the laser beam and scan it on the photoreceptor 9, forming an electrostatic latent image of the recorded image on it. The image is formed at a distance proportional to the angle, and the cylindrical lens 8 corrects the deviation of the image forming point caused by the unprepared inclination of the rotating polygon mirror 6.

By the way, the optical output (light amount) of a semiconductor laser is easily changed due to the influence of the environmental temperature, so the optical output of the laser is detected,
This is fed back to the semiconductor laser drive circuit to stabilize the optical output, and this control is called APC control.

In APC control, in order to detect the optical output of a semiconductor laser, it is necessary to drive and turn on the semiconductor laser 1/-, but when this laser beam scans the photoconductor 2, toner as a developer is consumed. Therefore, in order to detect the laser light output, it must be performed while the laser beam scans the non-image area on the photoreceptor (area near both ends of the photoreceptor where no electrostatic latent image of the recorded image is formed), and the control is required. There is a problem in that a light amount detection circuit with a fast response speed must be used because the amount of light of the beam must be detected in the early hours when the process becomes complicated.

(Objects and Structure of the Invention) The present invention has been made in view of the above points, and it is an object of the present invention to easily control the optical output of a semiconductor laser with a simple structure. A light shielding means was provided in the optical path, and the light shielding means was controlled to allow the laser beam to pass during the image writing period and to block the laser beam during the period other than the image writing period.

(Example) The present invention will be explained below based on the drawings.

In the laser recording apparatus according to the present invention, as shown in FIG. 1, a liquid crystal shutter 10 as a light shielding means is arranged in the beam optical path between the acousto-optic modulator 3 and the expander lens 4 of the scanning optical system. . The liquid crystal shutter 10 is controlled to block light by a control circuit 11. That is, as shown in FIG. 2, in image writing mode T, the liquid crystal shutter l
O is opened to allow the laser beam modulated by the image signal to pass through, and during the period when the image writing mode is not T, the liquid crystal shutter 1 is opened.
0 to 1" to block the laser beam, and detect the optical output during this time. Detection of the laser optical output is performed by a photodetector such as a photodiode, and the detection is performed by a known APC control circuit via a semiconductor laser drive circuit. to control the optical output of the laser.

By providing a light blocking means in the deflection optical path of the laser beam in this manner, it becomes possible to adjust the optical output of the 1/- laser regardless of the scanning means of the laser beam.

In the second embodiment, a liquid crystal shutter was used as the laser beam shielding means, but it goes without saying that a mechanical shutter may also be used. Further, the light shielding means may be placed anywhere as long as it is in the optical path of the laser beam.

(Effects of the Invention) As explained above, in the present invention, a light shielding means is provided in the optical path of the laser beam to allow the laser beam to pass during the image writing period and to shield the laser beam during periods other than the image writing period. With this structure, the laser light output can be detected and adjusted during this beam blocking, and the light output can be easily controlled and no toner is consumed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the schematic configuration of the scanning optical system of the laser recording device according to the present invention, and FIG. 2 is a time chart showing the operation of the light shielding means used in the laser recording device according to the present invention.
FIG. 3 is a schematic diagram of a scanning optical system of a conventional laser recording apparatus. ■...Ray f tube, 2.4...expander lens,
3... Acousto-optic modulator, 5.8... Cylindrical lens, 6... Rotating polygon mirror, 7... fθ lens, 9...
... Photoreceptor, 10 ... Liquid crystal shutter, 11 ... Control circuit patent Yamaganin Roku Konishi Photo Industry Co., Ltd. agent
Patent Attorney Hiroshi Suzuki Male 2nd V! J Oiden name return 1 1
1Figure 3

Claims (1)

[Claims] In a laser recording device that records an image on a photoreceptor by scanning a laser beam from a semiconductor laser, a laser beam shielding means is placed in the optical path of the laser beam, and a laser beam shielding means is placed in the optical path of the laser beam to record an image on a photoreceptor. 1. A laser recording apparatus comprising: a light shielding control means for controlling the light shielding means so that the laser beam passes through the laser beam and blocks the laser beam except during an image writing period.