JPH02181124A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To obtain an inexpensive and compact light beam scanning device by using a diffraction grating where the pitch of many grooves increases from one outermost groove to the other. CONSTITUTION:This light beam scanning device has the diffraction grating 11 which has many mutually parallel grooves 14 on the main surface so that the pitch of the grooves 14 increases from one outermost groove 141 to the other 142. Then the light beam 12 is scanned from the outermost groove 141 of the diffraction grating 11 to the other 142 and the resulting reflected beam 13 is scanned on the surface of a target 24 in a specific direction. Therefore, the light beam is deflected by a small angle to obtain a large scan angle. Consequently, the inexpensive and compact light beam scanning device is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light beam scanning device that scans a surface of an object with a light beam in a predetermined direction.

[Prior Art] This type of light beam scanning device is used, for example, in a laser printer. A laser printer is an information recording device that uses a semiconductor laser to record characters, graphics, etc. on paper at high speed.

In recent years, laser printers have been put into practical use as high-speed information recording devices for fax machines, copy machines, and the like, and have come to be widely used as office automation equipment.

[Problems to be Solved by the Invention] Conventional light beam scanning devices for such laser printers horizontally scan a light beam of a semiconductor laser or a HeNe laser using a polygon mirror, etc., and scan the light beam by driving a recording paper. Characters, figures, etc. are printed and recorded by vertical scanning.

However, in such a light beam scanning device, a polycon mirror mechanically rotated at high speed is used as an optical system for deflecting light, which is expensive and takes up a large space.

An object of the present invention is to eliminate the two disadvantages and provide an inexpensive and compact optical beam scanning device.

[Means for Solving the Problems] According to the present invention, in an apparatus for scanning a light beam in a predetermined direction on the surface of an object, the main surface has a large number of mutually parallel grooves; comprising a diffraction grating whose pitch becomes wider as it goes from one side to the other in two outermost grooves located at the outermost side of the plurality of grooves,
A light beam characterized in that the light beam is scanned from the one to the other of the outermost grooves of the diffraction grating, and the resulting reflected beam is scanned over the surface of the object in the predetermined direction. A scanning device is obtained.

[Example] Next, an example of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a light beam scanning device according to an embodiment of the present invention is a device that causes a light beam 12 to scan a surface of an object 24 in a predetermined direction DI. The light beam scanning device has a large number of grooves 14 parallel to each other on the main surface.
A diffraction grating] 1, in which the pitch between the plurality of grooves 14 becomes wider as it goes from one of the two outermost grooves 141 to the other [42]. We are prepared. The optical beam scanning device scans the optical beam 12 from the one 141 to the other 142 of the outermost groove of the diffraction grating 1, and scans the resulting reflected beam 3 onto the surface of the object 24. It scans in the predetermined direction.

Next, the action of the diffraction grating will be explained with reference to FIG.

The angle θ formed by the incident light 12 and the diffracted light 3 is, when the pitch of the diffraction grating is d, when a visible light semiconductor laser is used as a light source and the groove pitch of the diffraction grating having light dispersion characteristics is formed with m=1. d=
At 0.67 μm, the deflection angle θ is 90°, and d=
[When i is 7 μm, θ is −5.7°, and a light deflection angle of about 84° is obtained. This diffraction grating can be mass-produced using photolithography technology or plastic molding.

Referring again to FIG. 1, this optical beam scanning device is for a laser printer. For this reason, the visible photon conductor laser 21 and the ultrasonic light modulator 22 are further
have. Laser light 2 from visible light semiconductor laser 21
When the light beam enters the ultrasonic light modulator 22, a phase grating formed by the ultrasonic waves in the crystal of the ultrasonic light modulator 22 generates a light deflection of about several degrees. A light beam can be formed on the photosensitive drum by deflecting and expanding this beam angle using the above-mentioned diffraction grating 23.

In FIG. 1, D2 indicates the sub-scanning direction in which the photosensitive drum 24 is moved.

As described in Section 2 below, according to this embodiment, the system for controlling the deflected beam includes the ultrasonic optical modulator 22 and the diffraction grating 1 which has a certain light dispersion characteristic. Since it can be mass-produced using plastic mold molding, etc., it has the effect of providing a very inexpensive and compact laser printer.

[Effects of the Invention] As explained above, according to the present invention, by using a diffraction grating in which the pitch between a number of grooves becomes wider as it goes from one side of the outermost groove to the other, a light beam is focused at a small angle. By increasing the height, a large scanning angle can be obtained, and an inexpensive and compact optical beam scanning device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical beam scanning device according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining the action of the diffraction grating shown in FIG. 1. ] ]... Diffraction grating, ]2... Incident light (light beam),
]3... Diffracted light (reflected beam), ]4... Groove, 21...
...Semiconductor laser, 2..Ultrasonic optical modulator, 24. Photosensitive drum (object) ...Resa light. Figure 1 Figure 2

Claims (1)

[Claims] 1. A device that scans a light beam in a predetermined direction on the surface of an object, the main surface of which has a large number of mutually parallel grooves, and the pitch between the large number of grooves is located at the outermost side of the large number of grooves. a diffraction grating that becomes wider from one of the two outermost grooves toward the other, the light beam being scanned from the one to the other of the outermost grooves of the diffraction grating, and the resulting reflection An optical beam scanning device characterized in that a beam scans the surface of the object in the predetermined direction.