JPS61107315A - Optical scanner - Google Patents

Abstract

PURPOSE:To form a fine spot without the generation of unevenness over the whole range of a scanning direction by compensating the defocusing of a condensed beam which may be generated at the time of constant speed plane scanning by a constant speed reflector through the 1st condenser. CONSTITUTION:A laser beam radiated from a laser light source 1 is modulated by a modulator 2, expanded to parallel light by a beam expander 3, reflected by a reflector 9, and then turned to a condensed beam by an autofocusing condenser 10 and a condenser 11. The condensed beam is scanned by a rotating polyhedral reflecting mirror 5 and then scanned on a recording part at a constant speed by a constant speed reflector 12 and reflectors 13, 14. Since the autofocusing condenser 10 can moved in the optical axis direction, the arc-like locus of the condensed spot is converted into a linear locus by the condenser 10, so that the defocusing of the condensed spot beam is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical scanning device for recording or reading.

Conventional ft is modulated by a modulator 2 according to an image signal, this modulated beam is expanded by a beam expander 3, the expanded beam is subsequently reflected by a reflection mirror 4, and expanded by the beam expander 3, and this expanded beam is A rotating polyhedral reflection mirror 6 scans a certain angle, passes through a constant velocity scanning lens 6, and condenses the light onto a recording section 8 using a reflection mirror 7 for recording.This uniform velocity scanning lens 6 If the length is long, the lens shape becomes large because a wide-angle lens is used, and since it is necessary to have distortion aberration in order to have constant velocity scanning performance, the number of lenses increases, which not only makes the structure complicated. , and is expensive.Furthermore, there are drawbacks such as spot unevenness in the scanning direction due to astigmatism of the lens.

Purpose of the Invention The present invention solves the above-mentioned conventional problems. It is possible to form a minute spot even with an extremely long scanning length, and the shape of the sbot is uneven over the entire scanning direction. It is an object of the present invention to provide an optical scanning device that can avoid such problems and further reduce costs.

Structure of the Invention In order to achieve the above object, the present invention includes a laser light source;
a first condenser lens that is movable in the optical axis direction and condenses the beam from the laser light source; and a second condenser lens that condenses the beam from the first condenser lens onto the scanned surface. an optical lens, a polyhedral reflection mirror for scanning the beam from the second condensing lens, and a constant velocity reflection mirror for scanning the condensed beam reflected by the polyhedral reflection mirror at a constant speed, and so on. The present invention is characterized in that the first condenser lens corrects the defocus of the condensed beam when the plane is scanned at a constant speed of υ by the speed reflection mirror.

DESCRIPTION OF EMBODIMENTS Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 2 describes the case where recording is performed using the optical scanning device of the present invention. .

As shown in FIG. 2, a laser beam emitted from a laser light source 1 is modulated by a modulator 2 according to an image signal, and the modulated beam expander 3 expands the laser beam into parallel light of a certain size. This expanded beam is reflected by a reflection mirror 9 and becomes a condensed beam by an autofocus condenser lens 10 and a condenser lens 11. This beam is scanned by a rotating polyhedral reflection mirror 5,
The recording unit 8 is scanned at a constant velocity by the constant velocity reflecting mirror 12 and the reflecting mirrors 13, 14. The locus of the minimum spot of the focused beam at this time is in the form of an arc centered on the reflective surface of the polygonal reflective mirror 5 and having a radius equal to the length of the optical path to the recording section 8. Since the autofocus condenser lens 10 is movable in the optical axis direction, the autofocus condenser lens 1o follows the trajectory of the arc-shaped condensing spot.
This converts the focused spot beam onto a straight line, and prevents the focused spot beam from being out of focus in the scanning direction.

In the above embodiment, the case of recording using the present optical scanning device was described, but the present device can also be applied to reading. In this case, this is achieved by installing a device to be read, such as a document, in the recording section 8, and placing a document positioning signal, etc., instead of an image signal, on the modulator 2, and can essentially be handled in the same way. .

Effects of the Invention As is clear from the above explanation, according to the present invention, a first condensing lens that moves in the optical axis direction according to the focal shift between the laser light source and the polyhedral reflecting mirror, and A second condensing lens is installed to condense the beam, and the condensed beam is scanned by a polyhedral reflecting mirror and a plane is scanned at a constant velocity by a constant-velocity reflecting mirror. The first condensing lens performs correction and scanning. In this way, a condensing lens is used, eliminating the need for a constant-velocity scanning lens.The condensing lens allows only the axial beam to pass through, and does not allow beams with different angles of view to pass through, eliminating shadow density caused by astigmatism. ,
By considering only spherical aberration and minimizing this aberration, it is possible to obtain an even and minute spot, and it is also possible to reduce costs. In addition, if the optical path length from the polyhedral reflective mirror to the scanned surface is lengthened, the scanning length will be extremely long, but since the focal shift of the spot that occurs in the scanning direction that occurs at this time is corrected by the first condensing lens, the scanning length will be very long. It has advantages such as being able to scan and form minute spots.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a conventional optical scanning recording device, and FIG. 2 is a schematic perspective view showing an optical scanning recording device in an embodiment of the optical scanning device of the present invention. 1... Laser light source, 2... Modulator,
3... Beam expander, 5... Polyhedral reflecting mirror, 8... Ki part, 1o... Auto focus condensing lens, 11... Condensing lens , 12... Constant velocity reflector, 13114...
···Reflector.

Claims (1)

[Claims] a laser light source, a first condenser lens that is movable in the optical axis direction and that condenses the beam from the laser light source, and a second condenser lens that condenses the beam from the first condenser lens onto the surface to be scanned. a condenser lens, a polyhedral reflection mirror that scans the beam from the second condenser lens, and a constant velocity reflection mirror that scans the condensed beam reflected by the polyhedral reflection mirror at a constant velocity. An optical scanning device characterized by: