JPH01164918A - Two-dimensional optical scanner - Google Patents

Abstract

PURPOSE:To execute a raster scan at a high speed and with high accuracy by using rotary polygon mirror deflectors having each different rotation speed for executing horizontal and vertical deflections and a movable condensing means which is moved by a position information generating means of a light beam. CONSTITUTION:A light beam emitted from a laser light source 101 is made incident on a movable condensing system 103, and subsequently, brought to two-dimensional deflection by two rotary polygon mirror deflectors 104, 105. Also, in a position information generating means 102 whose timing is taken by a signal of a photodetector 107 for detecting a start point of the light beam, a position of the movable condensing optical system 103 corresponding to the beam position is programmed in advance, and by this signal, the movable condensing optical system 103 is driven. In such a way, a high speed raster having a high quality can be given simply.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the configuration of a scanning device for two-dimensionally scanning a laser beam.

[Conventional technology]

The conventional two-dimensional scanning device is NHK Technical Research 27NQ1, P
2O (1975), a rotating polygon mirror deflector was used for horizontal deflection, a galvano scanner was used for vertical deflection, and field curvature was corrected using an anamorphic lens. Another conventional technique, shown in FIG. 5, uses two galvano scanners 501 and has a movable imaging system 502 for focus correction. Furthermore, 50
3 is a laser light source, and 504 is a scanned plane.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology requires a galvano scanner that performs high-precision, high-speed control, and is an expensive device that can only be used in machine tools, laser projectors, etc. SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a two-dimensional optical scanning device that is simple and provides high-quality, high-speed rasters.

[Means for solving problems]

The two-dimensional optical scanning device of the present invention includes a rotary polygon mirror in which the horizontal and vertical deflection means have different rotational speeds, a light beam position information generating means, and a light beam that forms a dot on a scanned plane. It is characterized by comprising a movable condensing optical system for imaging, a means for generating position information of the movable condensing optical system corresponding to the position of the light beam, and a driving means.

[For production]

The above configuration of the present invention performs high-speed two-dimensional deflection using a rotating polygon mirror deflection device for horizontal and vertical deflection. At this time, astigmatism caused by the positional variation of the deflection point of the rotating polygon mirror is corrected actively and electrically by a movable condensing optical system. Further, the movement position of the movable condensing optical system is given by a preprogrammed position information generating means.

〔Example〕

FIG. 1 is a perspective view of a two-dimensional optical scanning device of the present invention. The light emitted from the laser light source 101 enters the movable condensing optical system 103, and then passes through two rotating polygonal mirror deflectors, 10
4.2-dimensionally deflected by 105. Further, 107 is a photodetector for detecting the starting point of the light beam, and the timing of the position information generating means 102 is determined based on this signal. The position of the movable condensing optical system corresponding to the beam position is programmed in advance in the position information generating means, and the movable condensing optical system 103 is driven by this signal. 106 is a scanned plane.

Next, a more specific example is shown in Table 1, which shows the main components of this example.

Table 1 FIGS. 2(a) and 2(b) are schematic diagrams of the optical system.

201 is the X-deflection plane, 202 is the Y-deflection plane, and the second
FIG. 2(a) shows the optical path in the Y-1 direction plane, and FIG. 2(b) shows the optical path in the X-direction plane.

Here, the distance from the movable focusing optical system to the scanned plane is y,
If the distance to the laser light source is X and the focal length of the movable condensing optical system is f, basically no image is formed.

Next, if the scanning angle is ±θ, the correction amount of y is y(1-c
osθ) ...<1).

Furthermore, the deflection surface of the rotating polygon mirror is moved in the optical axis direction. Generally, if the number of surfaces is N and the radius of the circumscribed circle is r, then this correction amount is maximum.

From the above, the maximum correction amount for y is ...(3) becomes.

If we enter the data in Table 1 and X” 400 mm, we get (
Equation 3) is 24 m + 0.17 m + 1.8 m, and it can be seen that field curvature is dominant.

Assuming that the maximum y correction is 241T1w+, the movement 1 of the movable condensing optical system requires only 4 μ of X correction according to the imaging formula (1).

FIG. 3 is a cross-sectional view of the movable condensing optical system. A glass lens 301 is fixed to a lens holder 302, and a permanent magnet 303 magnetized in the longitudinal direction and auxiliary magnetic poles 304 and 305 are fixed to the outside of the lens holder. The lens holder is elastically coupled to the yoke 308 by support springs 306 and 307, and a damper rubber 309 is provided between the support spring and the yoke.
．． 310 is inserted. By passing currents in opposite directions through the coils 311 and 312, it is possible to control the force acting on the permanent magnet, making it possible to minutely displace CL. The structure of this actuator is easy to process because all parts are cylindrical, and accuracy is easy to ensure. Furthermore, since it is not necessary to fix the damper rubber with adhesive, it becomes possible to use silicone rubber or the like, which is not easy to adhere but has excellent damping properties, as the damper rubber.

FIG. 4 is a configuration diagram of a control circuit for the movable condensing optical system. A clock is supplied from a clock generation circuit 402 to a no-line counter 403, a data selector 404, and an address counter 404 in response to an index signal 401 from a start point detector 107 shown in FIG. The no-line counter determines the end point or starting point of the female scan no-line, and can also be used as a synchronization signal from the female scanner.

Next, a frame memory 406 temporarily stores the video signal 405 according to the address from the address counter 404, a memory 407 stores the corrected position information of the actuator,
A laser drive signal and an actuator position signal are respectively read out from the two.

A data selector 404 performs serial conversion. Laser drive signal is laser driver 408
The signal is level-shifted and becomes a modulation signal for the laser diode 409. Meanwhile, the actuator position signal is also serially converted and converted into a drive level by the actuator driver 410.

It is convenient to drive the actuator by controlling the open loop using absolute position information.

Therefore, position detection is not performed in FIG. 4, but when accuracy is required, closed loop control is preferably performed.

When XY scanning was performed with the above configuration, a good number of resolution points was obtained. Similar results were obtained when the movable part was a laser diode.

Although the present invention has been explained based on the embodiments above, even if an optical path switching mirror, a beam cue receiving system, and a surface tilt correction optical system are added to the engineering system of the above embodiments, the effects of the present invention will not be impaired in any way. It is self-evident that there is no such thing. Further, in terms of applied fields, the present invention is not limited to laser beam printers, but can also be used in display devices and the like.

〔Effect of the invention〕

As shown above, according to the two-dimensional optical scanning device of the present invention,
A rotating polygon i! with different rotational speeds in horizontal and vertical directions. High-precision optical scanning is possible without using an anamorphic lens for field curvature correction, which was required in the past, by using a movable condensing means that is moved by the allil direction device and the optical beam internal position information generation means. can be done. Furthermore, since a rotating polygonal mirror deflector, which is excellent in mass production, is used, high-speed and highly accurate raster scanning can be performed.

[Brief explanation of the drawing]

FIG. 1 is a perspective configuration diagram of a two-dimensional optical scanning device of the present invention. FIG. 2(a) and FIG. 2(b) are schematic diagrams of the optical system,
(a) shows the optical path in the Y-deflection plane, and (b) shows the optical path in the XI reconfession plane. FIG. 3 is a sectional view of the actuator. FIG. 4 is a configuration diagram of a control circuit for the movable condensing optical system. FIG. 5 is a block diagram of a conventional two-dimensional scanning optical system. 101...Laser light source 102...Position information generating means 103...Movable condensing optical system 104.105...Rotating polygonal mirror deflector 106...Target Scanning plane 107...Photodetector and above Applicant: Seiko Epson Corporation, Figure 3, Figure 4

Claims (1)

[Claims] In an optical scanning device that performs two-dimensional scanning using two deflection means that deflect a light beam vertically and horizontally, a rotating polygon mirror deflector having different rotational speeds that performs horizontal and vertical deflection;
A means for generating positional information of a light beam, a movable condensing optical system that forms a point-like image of the light beam on a scanned plane, a means for generating positional information of the movable condensing optical system corresponding to the positional information of the light beam, and a drive. A two-dimensional optical scanning device characterized by having a means.