JPH08313807A - Multibeam recording device - Google Patents

Abstract

PURPOSE: To provide a multibeam recording device capable of adjusting the magnification while making a reducing projection lens telecentric to both sides of a light source and a photosensitive body. CONSTITUTION: A reducing projection lens 20 is composed by arranging, in order from the side of a light source 10, a first lens group 21 and a second lens group 22 both of which have positive powers, the reducing projection lens 20 is arranged so as to be telecentric to both sides of a light source part 10 and a photosensitive body P and an adjusting means 40, for adjusting the image forming magnification of the reducing projection lens 20 by moving the second lens group 22 in the direction of optical axis (z), 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 forming a pattern by 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.

In the multi-beam recording apparatus, in order to ease the positional accuracy on the light source side and the photosensitive material side, as disclosed in the above publication, the reduction projection lens is telecentric on both the light source side and the photosensitive material side. It is desirable that the optical system be almost afocal.

[0004]

However, when the reduction projection lens is an afocal system, if a magnification error occurs due to a manufacturing error of the optical system, the magnification is corrected even if the entire lens is moved in the optical axis direction. I can't.

Further, since the emission wavelength band of the semiconductor laser used in the multi-beam recording apparatus described in the above publication is a region where the wavelength of red or infrared is long, the size of the image spot is relatively large, There is a limit in improving the recording density.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art.
It is an object of the present invention to provide a multi-beam recording apparatus which is telecentric with respect to both sides of the photoconductor and whose magnification can be adjusted, and an apparatus which can improve the recording density.

[0007]

In order to achieve the above object, a multi-beam recording apparatus according to the present invention has a first lens group and a second lens group, both of which have positive power, arranged in order from the light source section side. To form a reduction projection lens, the reduction projection lens is arranged on both the light source side and the photoconductor surface side so as to be telecentric, and the reduction projection lens is changed by changing the distance between the first lens group and the second lens group. Is provided with adjusting means for adjusting the image forming magnification.

By making the light source side telecentric, when arranging the light sources, all the light beams from the respective light sources can be arranged in the optical axis direction of the reduction projection lens, and the light source section is arranged in the optical axis direction. It is possible to prevent a change in magnification even when the position is shifted.

Further, by making the surface of the photoconductor surface telecentric, it is possible to prevent the position of the image from changing even when the flatness of the surface of the photoconductor is poor or when the image is displaced in the optical axis direction to cause defocus.

Further, the imaging magnification can be adjusted by changing the distance between the first lens group and the second lens group. Since the reduction projection lens is an afocal system, the imaging magnification cannot be changed even if the whole is moved. Therefore, the group spacing is changeable, and the aberration is corrected so that the imaging performance does not change due to the movement.

In order to change the group spacing, it is desirable that the second lens group be independently movable in the optical axis direction. In a multi-beam recording apparatus having a plurality of light sources, the lens on the side closest to the light source that covers the light source has a large diameter and is heavy, so rather than moving the first lens group including this,
Moving the relatively lightweight second lens group reduces the load on the adjusting means.

In order for the light source side to be telecentric, the rear focal point of the first lens group must substantially coincide with the stop. For the photosensitive surface side to be telecentric, the front focal point of the second lens group must be It should match the aperture.

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 an emission wavelength in the blue region. Further, if the drawing density is improved, the allowable range for the imaging position error becomes narrower. Therefore, it is desirable to use the telecentric system as described above.

[0014]

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 reduction projection lens 20 is telecentric on both the light source section 10 side and the photoconductor P side. The second lens group 22 of the reduction projection lens 20 is
It can be moved in the optical axis direction z by the adjusting means 40, and the image forming magnification of the reduction projection lens 20 can be adjusted by this movement.

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.

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. In the multi-beam recording apparatus of the embodiment, the magnification error due to the manufacturing error of the lens is assumed to be about ± 0.1%, and ± 0.1
The second lens group is movable so that the magnification can be adjusted within the range of 26%. Below, the reduction projection lens 20
The following are three specific examples.

[0023]

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 astigmatism (S: sagittal, M: meridional),
(C) shows distortion.

Further, FIG. 7 shows the second lens group 22 with a 7 mm first
When moved in the direction away from the lens group 21 side (d8 =
42.30) shows various aberrations of the entire system, and FIG. 8 shows various aberrations of the entire system when the second lens group 22 is moved toward the first lens group 21 side by 7 mm (d8 = 28.30). . It can be understood that the aberration hardly deteriorates due to the movement.

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.

The fourth lens 22 of the second lens group 22
A diaphragm S is arranged between d and the fifth lens 22e, and the inter-lens distance d16 is the sum of the distance from the fourth lens to the diaphragm of 5.15 mm and the distance from the diaphragm to the fifth lens of 4.09 mm. .

[0027]

[Table 1] f = 138.46 FNo = 1: 2.5 d0 = 100 fB = 17.87 M = -0.039 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 the negative fifth lens 22e with the diaphragm S interposed therebetween,
The positive 6th to 10th lenses 22f to 22j are composed of 10 elements in 9 groups. The fifth and sixth lenses 22e and 22f are cemented lenses.

The rear focal point of the first lens group 21 and the front focal point of the second lens group 22 are the second focal points in the reference state shown in Table 1.
It substantially coincides with the diaphragm S provided in the central portion of the lens group 22, whereby the reduction projection lens 20 becomes telecentric on both the light source side and the photoconductor side. When the second lens group is moved in the optical axis direction, the telecentric condition is slightly broken and the imaging magnification changes.

[0030]

Second Embodiment FIG. 9 shows the overall structure of a reduction projection lens according to a second embodiment, FIG. 10 shows its various aberrations, FIG. 11 shows a first lens group, and FIG. 12 shows a second lens group. Table 2 shows a specific numerical configuration of the second embodiment. First lens group 2
The configuration of 1 is the same as that of the first embodiment.

Further, FIG. 13 shows a case where the second lens group 22 is moved in a direction away from the first lens group 21 side by 7 mm (d
8 = 35.89) and various aberrations of the entire system are shown in FIG.
The respective aberrations of the entire system when the lens group 22 is moved so as to approach the 7 mm first lens group 21 side (d8 = 21.89) are shown.

[0032]

[Table 2] f = 131.58 FNo = 1: 2.5 d0 = 100 fB = 19.53 M = -0.039 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

[0033]

Third Embodiment FIG. 15 shows the overall structure of a reduction projection lens according to a third embodiment, FIG. 16 shows its various aberrations, FIG. 17 shows a first lens group, and FIG. 18 shows a second lens group. Example 3
The specific numerical configuration of is shown in Table 3. The configuration of the first lens group 21 is the same as that of the first embodiment.

Further, FIG. 19 shows the case where the second lens group 22 is moved in the direction away from the first lens group 21 side by 7 mm (d
8 = 36.90) and various aberrations of the entire system are shown in FIG.
The respective aberrations of the entire system when the lens group 22 is moved so as to approach the 7 mm first lens group 21 side (d8 = 22.90) are respectively shown.

[0035]

[Table 3] f = 133.04 FNo = 1: 2.5 d0 = 100 fB = 18.31 M = -0.039 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

In Table 4, in each embodiment, the distance d8 between the first lens group and the second lens group was adjusted within the range of ± 7 mm from the reference magnification in the state shown in the above table. The change in magnification is shown. In any of the examples
The magnification can be changed by up to 0.26%. Since the magnification error due to the manufacturing error is estimated to be about 0.1%, it can be sufficiently corrected within the above adjustment range.

[0037]

[Table 4] Reference magnification -7 mm Adjusted magnification (rate of change) +7 mm Adjusted magnification (rate of change) Example 1 -0.0391 -0.0390 (-0.26%) -0.392 (+ 0.26%) Example 2 -0.0390 -0.0389 (-0.26%) -0.391 (+ 0.26%) Example 3 -0.0390 -0.0389 (-0.26%) -0.391 (+ 0.26%)

[0038]

As described above, according to the present invention, the reduction projection lens is arranged so as to be telecentric with respect to both the light source portion side and the photoconductor surface side.
Even if the light source unit or the photosensitive member surface is displaced in the optical axis direction, the movement of the image forming position can be avoided, the positional accuracy in assembling the light source unit can be eased, and the drawing accuracy can be improved. it can. Further, by changing the distance between the first lens group and the second lens, it is possible to correct a magnification error due to a manufacturing error or the like. Furthermore, when a light source having an emission wavelength in the blue region is used, drawing accuracy can be improved.

[Brief description of drawings]

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

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;

FIG. 7 is an aberration diagram of the entire system when the second lens group of Example 1 is moved 7 mm in a direction away from the first lens group.

FIG. 8 is a diagram of various aberrations of the entire system when the second lens group of Example 1 is moved 7 mm in a direction approaching the first lens group.

FIG. 9 is a lens diagram showing an overall configuration of a reduction projection lens according to a second example.

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

FIG. 11 is a lens diagram showing a first lens group of a reduction projection lens according to example 2;

FIG. 12 is an enlarged lens diagram showing a second lens group of the reduction projection lens according to the second example.

FIG. 13 is an aberration diagram of the entire system when the second lens group of Example 2 is moved 7 mm in a direction away from the first lens group.

FIG. 14 is a diagram of various aberrations of the entire system when the second lens group of Example 2 is moved 7 mm in a direction approaching the first lens group.

FIG. 15 is a lens diagram showing an overall configuration of a reduction projection lens according to a third example.

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

FIG. 17 is a lens diagram showing a first lens group of a reduction projection lens according to example 3;

FIG. 18 is an enlarged lens diagram showing a second lens group of the reduction projection lens according to the third example;

FIG. 19 is an aberration diagram of the entire system when the second lens group of Example 3 is moved 7 mm in a direction away from the first lens group.

FIG. 20 is a diagram of various aberrations of the entire system when the second lens group of Example 3 is moved 7 mm in a direction approaching the first lens group.

[Explanation of symbols]

 10 light source section 20 reduction projection lens 21 first lens group 22 second lens group 30 table 40 adjusting means

Claims (3)

[Claims] 1. A light source section comprising a plurality of light sources arranged two-dimensionally, and a positive first lens group and a positive second lens group are arranged in order from the light source section side. A reduction projection lens for forming an image of the light flux from the image on the surface of the photoconductor, and an adjusting means for adjusting the imaging magnification of the reduction projection lens by changing the distance between the first lens group and the second lens group, The multi-beam recording device, wherein the reduction projection lens is arranged so as to be telecentric on both the light source side and the photoconductor surface side. 2. The rear focal point of the first lens group is located outside the first lens, and the front focal point of the second lens group is located inside the second lens group. Item 1. The multi-beam recording device according to item 1. 3. The multi-beam recording apparatus according to claim 1, wherein the light source has an emission wavelength in a blue region.