JPH08310187A - Multi-beam recorder - Google Patents

Abstract

PURPOSE: To provide a multi-beam recorder capable of regulating a focusing position by a small-sized moving mechanism. CONSTITUTION: A contraction projection lens 20 for focusing the luminous flux from a light source 10 on a photosensitive member P has a positive first lens group 21 for collimating luminous fluxes from the source 10 side and a positive second lens group 22 for converging the fluxes collimated by the group 21. Regulating means for holding the focused state of the lens 20 to the member P by moving only the group 22 in an optical axis direction is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam recording apparatus for reducing and projecting a light beam from a light source section having a plurality of light sources on a drawing surface.

[0002]

2. Description of the Related Art A multi-beam recording apparatus of this type is disclosed in, for example, Japanese Patent Laid-Open No. 6-186490. In the device disclosed in this publication, a light beam from a light source unit including a plurality of semiconductor lasers arranged two-dimensionally and apertures corresponding to these is imaged on a photosensitive material via a reduction projection lens to form a photosensitive material. The pattern is recorded by scanning. This publication only discloses a photosensitive drum provided with a photosensitive material as a recording target, and does not mention adjustment of the focal position.

Generally, when a plurality of types of photosensitive materials having different thicknesses are to be recorded, the focal point is aligned with the recording surface by moving the entire optical system or the entire recording surface in the optical axis direction. Can be adjusted.

[0004]

However, when the size of the recording object, the light source section, or the optical system is relatively large, if the entire optical system or the entire recording surface is moved as described above. There is a problem that the moving mechanism becomes large. In addition, if the mechanism is large, the responsiveness generally tends to be low, and for example, when exposing a non-flat recording target surface, it becomes difficult to deal with it by auto focus.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a multi-beam recording apparatus capable of adjusting the focal position with a small moving mechanism. .

[0006]

In order to achieve the above-mentioned object, a multi-beam recording apparatus according to the present invention includes a reduction projection lens for forming an image of a light beam from a light source section on a photoconductor surface from a light source section side. By including a positive first lens group for collimating the light flux and a positive second lens group for converging the light flux collimated by the first lens group, by moving only the second lens group in the optical axis direction, It is characterized in that adjustment means is provided for keeping the in-focus state of the reduction projection lens with respect to the photosensitive body surface.

Since the focus position can be adjusted by moving only the second lens group, it is possible to avoid increasing the size of the adjusting means.
In particular, in a multi-beam recording apparatus having a plurality of light sources, the lens closest to the light source section that covers the light source section has a large diameter and is heavy, so that it is relatively lighter than moving the first lens group including it. Moving the second lens group reduces the load on the adjusting means.

Further, since the light flux emitted from each light source of the light source section becomes a parallel light flux between the first lens group and the second lens group, even if the inter-group distance changes for focus adjustment, The magnification of the exposure pattern on the body surface does not change.

In order to avoid the movement of the second lens group for the focus adjustment in the optical axis direction and the deterioration of the performance of the reduction projection lens due to the eccentricity associated with the movement, spherical aberration and coma of the first and second lens groups are avoided. It is desirable that each is corrected independently. If the aberrations are balanced between the two lens groups without correction independently, decentering coma, image plane tilt, and distortion will occur when the positional relationship shifts, and the imaging performance will deteriorate.

Further, focus detecting means for detecting the in-focus state of the reduction projection lens with respect to the photoconductor surface may be provided, and the second lens group may be moved in the optical axis direction based on the detection result of the focus detecting means. Good. According to this, even when the surface of the photoconductor is not flat, the in-focus state can be maintained by the autofocus. Since the apparatus of the present invention can adjust the focal position by moving only the second lens group, it is possible to secure high responsiveness suitable for autofocus.

As the light source, LE having an emission wavelength in the blue region is used.
D or the like can be used. Since the spot size has a positive correlation with the wavelength, it is possible to reduce the spot size and improve the recording density by using a light source having a long length for light emission in the blue region. Further, if the drawing density is improved, the allowable range for the focus error becomes narrower. Therefore, it is desirable that the autofocus be possible as described above.

[0012]

Embodiments of the multi-beam recording apparatus according to the present invention will be described below. As shown in FIG. 1, the multi-beam recording apparatus of the embodiment includes a light source unit 10 including a plurality of light sources arranged two-dimensionally, and a first light source unit 10 having positive power.
Reduction projection lens 20 including second lens groups 21 and 22
And the table 30 on which the photoconductor P to be recorded is placed
Composed of and.

The optical system unit including the light source unit 10 and the reduction projection lens 20 is movable in the X direction in a plane perpendicular to the optical axis of the reduction projection lens 20, and the table 30 is in the X direction in the same plane. And are slidable in the vertical Y direction.

The light source section 10 is composed of a plurality of LEDs (light emitting diodes) 12 mounted on the top panel 11, and an aperture panel 13 having apertures corresponding to the plurality of LEDs 12 in a one-to-one correspondence. A so-called blue LED having a peak wavelength of 450 nm is used as the LED 42.

The beam transmitted through the aperture reaches the photoconductor P via the reduction projection lens 20, and forms an image of the aperture on the surface of the photoconductor P. The photoconductor P has a wavelength
A so-called ortho-type photosensitive material having a spectral sensitivity in the range of 400 nm to 570 nm is used.

The light source unit 10 is provided with 2048 LEDs 12, 12 in 64 columns in the X direction and 32 rows in the Y direction. Correspondingly, as shown in FIG. 2, the aperture panel 13 has 64 apertures 13a arranged in a line in the X direction and 32 in the Y direction.
By forming the rows, a total of 2048 apertures 13a are formed.

The apertures in the nth row in the Y direction are arranged along the X direction at intervals larger than the diameter of the LED in the X direction (32 times the diameter of the aperture). Further, focusing on the aperture in the m-th column in the X direction, the aperture in the n-th row and n +
The aperture of the first row is formed at a position shifted by the diameter in the X direction. Each LED is arranged to be centered on the aperture.

Focusing on a certain line on the photoconductor P in the X direction, by moving the table 30 in the Y direction,
The light flux from each row in the Y direction of the aperture sequentially arrives,
The pattern on the line is completed when the light flux of 32 rows is reached. The table 30 moves in the Y direction and moves to 2048
When the pattern formation of the strip-shaped area for the spot is completed,
The optical system unit is moved in the X direction to form a pattern in the next strip-shaped region.

As shown in FIG. 1, the second lens group 22
Between the table 30 and the table 30, a focus detection light projecting unit 40 for obliquely entering the detection light from the outside of the optical axis of the reduction projection lens 20 toward the photoconductor P, and the photoconductor emitting from this light projecting unit 40. A focus detection light receiving unit 50 that receives the light reflected by P is provided. The output of the focus detection light-receiving unit 50 is input to the control means 60, which controls the reduction projection lens 2.
The second lens group 22 is moved in the optical axis direction z via the driving means 61 so that the focus of 0 is made to coincide with the photoconductor P.

The luminous flux emitted from the LED 41 of the focus detection light projecting section 40 is transmitted through the light projecting lens 42 to the reduction projection lens 2
It is reflected by the photoconductor P at a position substantially intersecting the optical axis of 0. Here, the LED 41 has a wavelength outside the spectral sensitivity of the photoconductor P, for example, an emission wavelength in the red region. The light flux from the LED 41 reflected by the photoconductor P is received by the focus detection light receiving unit 5
It is condensed on the PSD 52 by the condenser lens 51 of 0.

The PSD 52 outputs, as an electric signal, a condensing position that changes according to the position of the photoconductor in the optical axis direction. For example, when the position of the photoconductor P is displaced from the position shown by the solid line in FIG. 1 to the position shown by the broken line in the direction away from the reduction projection lens 20, the condensing position on the PSD 52 also changes accordingly. The control means 60 can move the second lens group 22 based on the output signal of the PSD 52 so that the focus of the reduction projection lens 20 coincides with the photoconductor.

The reduction projection lens 20 is actually composed of a total of 14 lenses, that is, four lenses for the first lens group 21 and ten lenses for the second lens group 22 as shown in FIG. Aberrations of these lens groups are individually corrected so that the performance as a whole does not deteriorate even when the second lens group 22 is independently moved in the optical axis direction by the driving unit 61.

In the multi-beam recording apparatus of the embodiment, a photosensitive film which is a mask for a printed circuit board and a printed circuit board having a resist layer on the surface are used as recording targets. The difference between these thicknesses is about 6 mm, and the undulation on the surface of the photoconductor is about 250 μm at the maximum. In the embodiment, the focal position can be changed within a range of 7 mm in consideration of the displacement due to the change in the thickness of the photoconductor and the displacement due to the undulation of the photoconductor surface. Three specific examples of the reduction projection lens 20 will be shown below.

[0024]

EXAMPLE 1 FIG. 3 is an overall configuration of a reduction projection lens according to Example 1, FIG. 4 is its various aberrations, FIG. 5 is the first lens group,
FIG. 6 shows the second lens groups, respectively. Figure 4 (A) is 450nm
Of spherical aberration SA and sine condition SC in FIG.
(B) is chromatic aberration represented by spherical aberration of 400 nm, 450 nm, 550 nm, (C) is chromatic aberration of magnification represented by 400 nm, 550 nm, (D) is astigmatism (S: sagittal, M: meridional), ( E) shows distortion.

7 and 8 show the first lens group 21.
A single spherical aberration and a lateral aberration are shown respectively, and FIGS. 9 and 10 show a spherical aberration and a lateral aberration of the second lens group 22 alone, respectively.

Table 1 shows a specific numerical configuration of the first embodiment. In the table, symbol f is the focal length (mm), FNO is the F number, d0 is the distance (mm) on the optical axis from the aperture plate to the object side surface of the first lens L1, and fB is the back focus (m
m), M is the magnification, r is the radius of curvature (mm), d is the lens thickness on the optical axis and the air gap (mm), n450 is the refractive index at 450 nm,
ν is the Abbe number. In each embodiment, d0 is
The light beams emitted from the LEDs 12 and emitted from the first lens group 21 are set to be parallel light beams. Further, a diaphragm S is arranged between the fourth lens 22d and the fifth lens 22e of the second lens group 22, and an inter-lens distance d16 is 5.15 mm from the fourth lens to the diaphragm and from the diaphragm to the first lens. The sum of the distances up to 5 lenses is 4.09mm.

[0027]

[Table 1] f = 138.46 FNo = 1: 2.5 d0 = 17.25 fB = 18.00 M = -0.040 surface number r d n450 ν surface number r d n450 ν 1 ∞ 47.00 1.52485 64.1 17 -5.743 1.20 1.66888 33.8 2 -370.000 360.48 18 -25.828 4.00 1.50347 81.6 3 198.800 18.00 1.49480 70.2 19 -9.200 0.25 4 -533.000 69.40 20 -24.120 4.00 1.50347 81.6 5 -73.562 5.00 1.63114 49.8 21 -12.800 0.20 6 81.685 19.92 22 59.800 3.50 1.50347 81.6 7 135.029 9.80 1.49480 70.2 0.10 8 -65.656 35.30 24 40.040 3.50 1.50347 81.6 9 93.720 2.00 1.50347 81.6 25 -131.719 0.10 10 20.790 6.50 26 50.000 3.00 1.50347 81.6 11 31.514 3.50 1.71354 31.1 27 ∞ 12 -2324.027 0.35 13 10.000 5.30 1.50347 81.6 14 35.190 0.70 15 20.874. 33.8 16 7.400 5.15 Aperture 4.09

In the first embodiment, the first lens group (first surface to eighth surface) 21 is a positive first lens 21a, a positive second lens 21b, a negative third lens 21c, and a positive third lens from the object side. The second lens group (9th surface to 27th surface) 22 is composed of four lenses of four lenses 21d, and the second lens group (9th surface to 27th surface) 22 has a negative first lens 22a, a positive second lens 22b, a positive third lens 22c, and a negative third lens 22c. 4th lens 2
2d, and a negative fifth lens 22e, and positive 6th to 10th lenses 22f to 22j, and 10 elements in 9 groups, with a diaphragm interposed therebetween. The fifth and sixth lenses 22e and 22f are cemented lenses.

[0029]

Second Embodiment FIG. 11 shows the overall structure of a reduction projection lens according to a second embodiment, FIG. 12 shows its various aberrations, FIG. 13 shows a first lens group, and FIG. 14 shows a second lens group. Example 2
The specific numerical configuration of is shown in Table 2.

The structure of the first lens group 21 is the same as that of the first embodiment. 15 and 16 show spherical aberration and lateral aberration of the second lens group of Example 2 alone.

[0031]

[Table 2] f = 131.58 FNo = 1: 2.5 d0 = 17.25 fB = 19.66 M = −0.040 surface number r d n450 νd surface number r d n450 νd 1 ∞ 47.00 1.52485 64.1 17 -5.650 1.20 1.66888 33.8 2 -370.000 360.48 18 -24.770 4.00 1.50347 81.6 3 198.800 18.00 1.49480 70.2 19 -8.925 0.25 4 -533.000 69.40 20 -18.870 4.00 1.49480 70.2 5 -73.562 5.00 1.63114 49.8 21 -12.676 0.20 6 81.685 19.92 22 94.898 3.50 1.49480 70.2 7 135.029 9.80 1.49480 70.2 23. 0.10 8 -65.656 28.89 24 38.083 3.50 1.49480 70.2 9 189.224 2.00 1.50347 81.6 25 -155.523 0.10 10 19.820 6.50 26 29.723 3.00 1.50347 81.6 11 45.983 3.50 1.71354 31.1 27 -211.054 12 -112.300 7.32 13 9.797 5.30 1.50347 81.6 14 71.564 0.220 158 1.66888 33.8 16 8.164 5.00 Aperture 4.00

[0032]

Third Embodiment FIG. 17 shows the overall structure of a reduction projection lens according to a third embodiment, FIG. 18 shows its various aberrations, FIG. 19 shows a first lens group, and FIG. 20 shows a second lens group. Example 3
The specific numerical configuration of is shown in Table 3.

The structure of the first lens group 21 is the same as that of the first embodiment. 21 and 22 show spherical aberration and lateral aberration of the second lens group of Example 2 alone.

[0034]

[Table 3] f = 133.04 FNo = 1: 2.5 d0 = 17.25 fB = 18.44 M = -0.040 surface number r d n450 νd surface number r d n450 νd 1 ∞ 47.00 1.52485 64.1 17 -5.561 1.20 1.66888 33.8 2 -370.000 360.48 18 -31.156 4.00 1.50347 81.6 3 198.800 18.00 1.49480 70.2 19 -9.070 0.25 4 -533.000 69.40 20 -19.045 4.00 1.49480 70.2 5 -73.562 5.00 1.63114 49.8 21 -12.344 0.20 6 81.685 19.92 22 71.003 3.50 1.49480 70.2 7 135.029 9.80 1.49480 70.2 0.10 8 -65.656 29.90 24 34.908 3.50 1.49480 70.2 9 153.719 2.00 1.50347 81.6 25 -60.862 0.10 10 19.757 6.50 26 28.050 3.00 1.49480 70.2 11 53.471 3.50 1.71354 31.1 27 93.255 12 -81.213 6.13 13 9.775 5.30 1.50347 81.6 14 85.243 0.47 1566. 33.8 16 8.707 5.00 Aperture 4.00

[0035]

As described above, according to the present invention, since the focal position of the reduction projection lens can be adjusted by driving only the second lens group, the thickness of the photosensitive member can be increased without increasing the size of the apparatus. The focus position can be easily adjusted according to the change in the height.

Further, since the light flux emitted from the first lens group is configured to be a parallel light flux, the imaging magnification does not change even when the second lens group moves in the optical axis direction, and further, Since the focus can be adjusted simply by moving the relatively lightweight second lens group, it is possible to easily deal with autofocus.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a multi-beam recording apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of apertures on the aperture plate of FIG.

FIG. 3 is a lens diagram illustrating an overall configuration of a reduction projection lens according to a first example.

FIG. 4 is a graph showing various aberrations of the reduction projection lens of Example 1.

FIG. 5 is a lens diagram showing a first lens group of a reduction projection lens according to example 1;

FIG. 6 is an enlarged lens diagram showing a second lens group of the reduction projection lens according to the first example;

7 is a spherical aberration diagram of the first lens group of Example 1. FIG.

8 is a lateral aberration diagram for the first lens group of Example 1. FIG.

9 is a spherical aberration diagram of the second lens group of Example 1. FIG.

FIG. 10 is a lateral aberration diagram for the second lens group according to Example 1.

FIG. 11 is a lens diagram showing an overall configuration of a reduction projection lens according to a second example.

12 is a graph showing various aberrations of the reduction projection lens of Example 2. FIG.

FIG. 13 is a lens diagram showing a first lens group of a reduction projection lens according to example 2;

FIG. 14 is an enlarged lens diagram showing a second lens group of the reduction projection lens according to the second example.

FIG. 15 is a spherical aberration diagram of the second lens group of Example 2.

FIG. 16 is a lateral aberration diagram for the second lens group according to example 2.

FIG. 17 is a lens diagram showing an overall configuration of a reduction projection lens according to a third example.

FIG. 18 is a graph showing various aberrations of the reduction projection lens of Example 3;

FIG. 19 is a lens diagram showing a first lens group of a reduction projection lens according to example 3;

FIG. 20 is an enlarged lens diagram showing a second lens group of the reduction projection lens according to the third example;

FIG. 21 is a spherical aberration diagram of the second lens group of Example 3.

FIG. 22 is a lateral aberration diagram for the second lens group according to the third example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-beam recording device 1 10 Light source part 10 20 Reduction projection lens 21 1st lens group 22 2nd lens group

Claims (4)

[Claims] 1. A light source section having a plurality of light sources arranged two-dimensionally, a positive first lens group for collimating a light flux from the light source section side, and a parallelization by the first lens group. A reduction projection lens that is composed of a positive second lens group that converges the light flux and that focuses the light flux from the light source unit on the photoconductor surface; and the photoconductor surface by moving the second lens group in the optical axis direction. Adjusting means for maintaining the in-focus state of the reduction projection lens for the multi-beam recording apparatus. 2. The multi-beam recording apparatus according to claim 1, wherein the first lens group and the second lens group are individually corrected for spherical aberration and coma. 3. A focus detection unit for detecting a focus state of the reduction projection lens with respect to the photosensitive body surface, wherein the adjustment unit is configured to detect the focus state of the second projection unit based on a detection result of the focus detection unit.
The multi-beam recording apparatus according to claim 1, wherein the lens group is moved in the optical axis direction. 4. The multi-beam recording apparatus according to claim 1, wherein the light source has an emission wavelength in a blue region.