JPH03100617A - Scanning optical device - Google Patents

Abstract

PURPOSE:To prevent spot performance on a scanning plane degrading by applying slide adjustment or turning adjustment to a static deflecting system. CONSTITUTION:A holding mechanism including the static deflecting system 20 which separates a beam of light from a laser beam source 10 from reflected light by a scan deflecting system 30 is set slidably freely in the optical axis direction or the X-axis of a scan lens 40 or in a direction almost perpendicularly to the optical axis within a main scan cross section, or it is set in such a manner that it can be turned freely around an axis parallel with the optical axis of the scan lens 40 i.e. the X-axis, the axis almost perpendicular to the optical axis in a main scan cross-sectional drawing i.e. a Y-axis, and furthermore, the axis almost perpendicular to the optical axis within a subscan cross-sectional drawing i.e. a Z-axis as employing constitution in which a laser beam of light is made incident on the scan deflecting system 30 from the optical path of a deflecting beam of light by the scan deflecting system 30. In such a manner, it is possible to prevent wave aberration on the scanning plane deteriorating and to prevent a spot disturbed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a scanning optical device that forms a pattern on a scanning surface by scanning a 0N10FF modulated laser beam on the scanning surface. In particular, the present invention relates to an apparatus such as a laser engraving machine that requires high density in the pattern formed.

[Conventional technology] In order to perform highly accurate drawing, the spot must be narrowed down to a small size. In order to reduce the spot diameter, it is necessary to increase the F number of the optical system, which inevitably reduces the depth of focus. It becomes shallow. Therefore, in order to keep the spot diameter on the scanning plane approximately constant, the curvature of field must be kept small.

However, if the optical axis of the scanning lens and the optical axis of the light beam incident on the polygon mirror do not match within the plane where the light beam is scanned by the polygon mirror, the deflection point will change to the fθ lens as the polygon mirror rotates. It changes asymmetrically between positive and negative image heights across the optical axis.

Therefore, there is a problem that the curvature of field on the photoreceptor surface becomes asymmetric, and cannot be corrected when using a lens symmetrical with respect to the optical axis.

In order to solve this problem, a configuration can be considered in which the laser beam is made incident on the polygon mirror through the optical axis of the scanning lens. Since the appearance of field curvature is symmetrical, it can be corrected with a lens that is symmetrical about the optical axis, and the value is also very small.

However, in order to adopt such a configuration, a static deflector must be placed in the optical path of the light reflected by the polygon mirror to separate the light beam from the light source to the polygon mirror and the light beam incident from the polygon mirror to the fθ lens. It is necessary to do so.

By the way, Japanese Unexamined Patent Publication No. 60-233618 discloses a configuration in which a polarizing beam splitter and a quarter-wave plate are used to cause a light beam from a light source to enter a polygon mirror through the optical axis of a scanning lens. There is.

In the configuration of JP-A No. 60-233618, in order to correct the influence of the inclination of the reflecting surface of the polygon mirror with respect to the rotation axis, which is called a surface tilt error, the laser beam is directed to the polygon mirror within the sub-scanning section. The image is once formed on the reflective surface. Therefore, it is not possible to provide a total reflection mirror as a static deflector, and it is necessary to use a polarizing beam splitter or the like.

However, in the case of the configuration described in the above publication, the angle of incidence of the light beam on the polarizing beam splitter changes as the polygon mirror rotates, so the transmittance of the polarizing beam splitter gradually decreases from the center to the periphery. This causes unevenness in the amount of light on the photoreceptor surface.

In order to solve each of the above-mentioned problems, the present applicant adopted a configuration in which the laser beam is incident on the Bogongon mirror through the optical axis of the scanning lens, and also developed a configuration in which a total reflection mirror can be used as a static deflector. Patent application Hei 1-63934
The proposal was made in issue 4.

That is, the light beam from the laser light source is once imaged in the sub-scanning section before entering the scanning deflector, and a static deflector is placed at this image formation position to guide the light beam from the light source to the scanning deflector. , guides the light beam reflected by the scanning deflector to the scanning lens.

The static deflector has a slit mirror that reflects the light beam or a mirror that is provided with a slit that transmits the light beam.

According to such a configuration, most of the light reflected by the scanning deflector is transmitted around the slit mirror or reflected by the portion outside the slit of the slit mirror, and forms a spot on the scanning surface via the scanning lens. tie.

However, when implementing the above proposed technology, it is necessary to arrange a prism to provide a slit mirror etc. between the polygon mirror and the scanning lens, so depending on the positional relationship of this prism, the light incident on the polygon mirror may [Objective of the Invention] This invention was made in view of the above problems,
The purpose of the present invention is to provide a scanning optical device that can prevent the deterioration of wavefront aberration on the scanning surface with a relatively simple configuration, and that can perform drawing with high precision. An object of the present invention is to provide a scanning optical device that can prevent spot disturbance due to angular errors.

[Means for Solving the Problems] In order to achieve the above object, a scanning optical device according to the present invention employs a configuration in which a laser beam is incident on a scanning deflector from the optical path of a beam deflected by the scanning deflector. The holding mechanism, which includes a static deflector that separates the light beam from the laser light source and the light reflected by the scanning deflector, can be slid in the optical axis direction of the scanning lens or in a direction almost perpendicular to the optical axis within the main scanning cross section. Alternatively, it can be freely rotated around an axis parallel to the optical axis of the scanning lens, or around an axis almost perpendicular to the optical axis in the main scanning section, and around an axis almost perpendicular to the optical axis in the sub-scanning section. It is characterized by

[Example] The present invention will be described below based on the drawings. 1 to 4 show an embodiment of a scanning optical device according to the present invention.

First, the arrangement of the optical elements of this device will be explained based on FIG.

The illustrated optical system includes a laser diode 10 as a light source, a collimating lens 11 that converts diverging light emitted from the laser diode 10 into a parallel light beam, a folding mirror 12 that reflects the collimated light beam, and a line image using this light beam. A prism block 20 has a cylindrical lens 13 as a condensing lens to form a condenser lens, a slit mirror 21 as a static deflector provided in alignment with the line image position of the light beam, and a prism block 20 that reflects the light beam reflected by the slit mirror 21. It includes a polygon mirror 30 as a scanning deflector for polarizing light, and an fθ lens 40 as a scanning lens for condensing the light beam reflected by the polygon mirror 30 to form a spot on the scanning surface.

Here, the surface scanned by the light beam by the polygon mirror 30 is defined as a main scanning section, and the surface perpendicular to the main scanning section and including the rotation axis 31 of the polygon mirror is defined as a sub-scanning section.

The prism block 20 has a rectangular parallelepiped shape in which a triangular prism 22 and a trapezoidal prism 23 are bonded together, and a slit mirror 21, which is a total reflection mirror, is deposited on the bonded surface. The angle of the slit mirror 21 with respect to the main scanning section is approximately 45°.

After being collimated, the diverging light emitted from the laser diode 10 is focused onto the slit mirror 21 by the cylindrical lens 13, and the entire amount of light is reflected by the slit mirror 21, passing through the optical axis of the fθ lens 40 to the polygon mirror 30. heading towards.

The light beam reflected and polarized by the polygon mirror 30 reaches the prism block 20 again with a predetermined spread. Here, most of the light flux passes through the periphery of the slit mirror 21 and enters the fθ lens 40.

The light beam emitted from the fθ lens 40 is deflected to the lower side of the base by a mirror 51 provided at the left end of the base 90, and is then deflected to the lower side of the base by a mirror 52. A spot that is scanned at a constant speed is formed on a panel 61 as a scanning target that is guided by a feed roller 53 and conveyed by a feed roller 60.

The slit mirror 21 provided to separate the optical paths does not change the transmittance due to changes in the rotation angle of the polygon mirror 30, so the image height on the scanning plane does not change as in the case of using a deflection beam splitter. There is no change in spot intensity due to

Next, the specific assembly of each optical element will be explained based on FIGS. 1 to 3, and at the same time, the adjustment direction of each optical element will be explained with reference to FIG. 10.

The coordinates in the figure are determined based on the traveling direction of the light beam, and the emission direction of the light beam of the laser diode 10 and the optical axis direction of the fθ lens 40 are the y axis, and the polygon mirror 3
The direction of the zero rotation axis 31 is defined as two axes, and the direction perpendicular to both the X and Z axes is defined as the y axis.

Each optical element is attached to a flat base 90 as a unit.

A polygon unit 100 incorporating a polygon mirror 30 and a motor for rotationally driving the polygon mirror 30 is immovably fixed to a base 90.

The light source unit 200, which includes everything from the laser diode 10 to the prism block 20, includes a lower substrate 201 that is slidable in the X-axis direction with respect to the base 90, and a lower substrate 2
01, and an upper substrate 202 which is rotatably provided around the Xe3' axis.

As shown in FIG. 2, the lower substrate 201 has two abutments fixed to the base 90 whose positions in the y-axis direction are determined by pins 203, and which are screwed into the base 90 through the lower substrate. The base 9 is fixed by the fixing bolts 204 at the four corners that match.
Fixed to 0. The through holes in the lower board 201 through which each of the fixing bolts 204 are inserted are formed to be larger than the diameter of the bolts, so by loosening these fixing bolts 204, the lower board 201 can be attached to the bin along the
It can be slid in the axial direction.

The sliding adjustment of the light source unit 200 in the X-axis direction has the effect of correcting out-of-focus in the sub-scanning direction on the scanning plane due to errors in the curvature of the lens system, the distance between surfaces, and the like.

The upper substrate 202 is positioned in the Xe'1 direction by abutting pins 205 fixed at three locations on the lower substrate 201. Further, the upper substrate 202 has screw holes formed at its four corners so that the tips thereof are connected to the lower substrate 202 as shown in FIG.
Adjustment bolts 206 that come into contact with the adjustment bolts 206 are screwed together, and fixing bolts 2 provided adjacent to these adjustment bolts 206 are screwed together.
07 to the lower substrate 201.

Therefore, by loosening the fixing bolt 207 and operating the adjustment bolt 206, the upper substrate 202 can be adjusted with respect to the lower substrate 201 around the x and y axes.

The rotational adjustment of the light source unit 200 including the prism block around the X axis is for correcting the collapse of the spot shape on the scanning plane and the deterioration of the image quality. After the adjustment is completed, it is used to improve the overall performance of the device.

The prism block 20 fixed at the center of the upper substrate is slidable in the y-axis direction with respect to the upper substrate 202. Considering the vignetting of the light beam transmitted from the polygon mirror 30 to the fθ lens 40 side, it is desirable that the area of the slit mirror 21 be as small as possible.Sliding adjustment of the prism block in the y-axis direction can be done by changing the size of the slit mirror. When the size is about the same as the line image formed by the cylinder lens 13, it is necessary to match these positional relationships.

As shown in FIG. 1, on the upper substrate 202, between the upper ends of the zero leg parts 210, two legs 210 are fixed to both sides of the prism block by fixing screws 210a that are screwed together from below. A horizontal plate 211 is installed, and a vertical plate 212 is installed between the legs 210 below the horizontal plate 211.

On the horizontal plate 211, there is a cylindrical lens barrel 220 in which the laser diode 10 and the collimating lens 11 made up of four lenses Ila to 4th lens lid are incorporated, and a mirror support part that supports the folding mirror 12. 230 is fixed.

The laser diode 10 is configured to be slidable in the y-z direction so that the oscillation light beam can be aligned with the designed optical axis, since there are variations in the location where light is emitted from product to product.

The collimating lens 11 is slidable in the y-axis direction to adjust its relative relationship to the laser diode 10. This is an adjustment for correcting out-of-focus in the main scanning direction on the scanning plane due to errors in the curvature of the lens system, distance between surfaces, etc.

The folding mirror 12 is rotatably adjustable around two axes, the Ly axis.

Further, the vertical plate 212 includes a positive lens 13a and a negative lens 1.
A cylinder lens 13 made up of a combination of lenses 3b and 3b is attached via a holder 240.

Since the cylinder lens 13 may include variations from product to product due to processing errors, it is possible to adjust the slide in the optical axis (X-axis) direction and adjust the rotation around the optical axis. The former adjustment is to adjust the movement of the line image along the optical axis direction to match the focus with the slit mirror.
The latter adjustment is for rotationally adjusting the direction in which the line image is formed to match the direction of the slit mirror 21.

In addition, from the laser diode 10 to the prism block 2
The parts up to 0 are integrated as one unit independent from other parts, which increases assembly accuracy and prevents misalignment between the line image forming position by the cylinder lens 13 and the slit mirror 21. .

The lens unit 300 includes an rθ lens 40 composed of three anamorphic lenses 41, 42, and 43, and a lens substrate 301 on which these lenses are arranged. The lens substrate 301 and the light source unit 200 are fixed to two places on the base 90 using pins 302.
The position in the X-axis direction is determined by abutting against the base 90, and it is fixed to the base 90 with fixing bolts 303 at the four corners.

Therefore, by loosening the fixing bolt 303, the lens substrate 301 can be slid in the y-axis direction using the bottle 302 as a guide.

In addition, the three anamorphic lenses are held down by a holding spring plate 311 provided by a holding plate 310 that covers the central lens.
The lens 42 is fixed to the lens substrate 301 in the z-axis direction through the lens board 301, and the center lens 42 is assembled so as to be rotatably adjustable around the Xty axis.

The adjustment of the fθ lens 40 is to correct the tilt of the image plane and the deterioration of image quality due to eccentricity errors.

As shown in FIG. 3, support members 312 slightly longer than the height of the lens are screwed to the four corners of the holding plate 310 to the lens substrate 301. It is fixed using fixing bolts 313.

In addition, each lens has 3 pins attached at 3 places.
0.320, . . , and these abutments are attached to L-shaped fixing plates 321. 321, . . . are applied and fixed to the lens substrate 301 in the Xty direction.

The abutment bin 203 for determining the position of the light source unit 200 and the abutment bin 302 for determining the position of the lens unit described above are positioned with respect to the center of rotation of the polygon mirror 30.

Additionally, on the lower right side of FIG. 2, as a means for detecting the rotational position of the polygon mirror 30, there is a monitor light source unit 400 that irradiates a monitor light beam onto a surface different from the surface of the polygon mirror 30 that reflects the drawing light beam. , and a monitor light receiving unit 500 that receives the monitor light beam reflected by the polygon mirror 30. Since these units have no relation to the invention, detailed description thereof will be omitted.

[Effect] As explained above, according to the scanning optical device of the present invention, by adjusting the slide of the static deflector, it is possible to easily match the line image formed by the condenser lens with the position of the slit mirror, etc. can be done.

Further, by adjusting the rotation of the static deflector, even if the spot performance on the scanning plane deteriorates due to an error from the design value of the lens, it can be adjusted to improve it.

[Brief explanation of drawings]

1 to 4 show an embodiment of a scanning optical device according to the present invention. IIIy! J is a side view of the light source unit corresponding to the view taken along the line II in FIG. 2, FIG. 2 is a plan view of the entire device, and FIG. Figure 4 is a perspective view showing the arrangement of optical elements.
... Laser diode 13 ... Cylinder lens 20 ... Prism block 21 ... Slit mirror 30 ... Polygon mirror 40 ... fθ lens

Claims (6)

[Claims] (1) A laser light source, a scanning deflector that reflects and deflects the light beam from the laser light source to scan within the main scanning cross section, and a scanning lens that focuses the laser light beam reflected by the scanning deflector onto the scanning surface. , a condenser lens that once forms an image in a sub-scanning section perpendicular to the main scanning section before the light beam from the laser light source enters the scanning deflector; and a condensing lens that forms an image in the optical path of the light reflected by the scanning deflector. a static deflector that is provided at a position where the light beam is imaged and guides the light beam from the laser light source to the scanning deflector and causes the light reflected by the scanning deflector to enter the scanning lens; What is claimed is: 1. A scanning optical device comprising: a holding mechanism that holds one optical element integrally while distinguishing it from other optical elements; and an adjustment mechanism that adjusts the position of the holding mechanism. (2) The scanning optical device according to claim 1, wherein the adjustment mechanism is a sliding mechanism that slides the holding mechanism in the optical axis direction of the scanning lens. (3) The scanning optical device according to claim 1, wherein the adjustment mechanism is a slide mechanism that slides the holding mechanism in a direction substantially perpendicular to the optical axis of the scanning lens within the main scanning section. . (4) The scanning optical device according to claim 1, wherein the adjustment mechanism is a rotation mechanism that rotates the holding mechanism around a rotation axis parallel to the optical axis of the scanning lens. (5) The adjustment mechanism is a rotation mechanism that rotates the holding mechanism within the main scanning section around a rotation axis substantially perpendicular to the optical axis of the scanning lens. scanning optical device. (6) The adjustment mechanism is a rotation mechanism that rotates the holding mechanism within the sub-scanning section about a rotation axis substantially perpendicular to the optical axis of the scanning lens. scanning optical device.