JPH02123320A - Scanner for plural beams - Google Patents

Abstract

PURPOSE:To synthesize three pieces or more of beams onto a deflector by separating spatially plural beams and allowing them to be made incident on a lens system. CONSTITUTION:The title scanner is provided with a light source part 10, lens systems 50, 60, 70, 80 and 90, a deflector PM, and a scanning lens 100 for separating a deflected beam into the scanning direction of the beam by the deflector PM and in the direction being orthogonal to said direction and condensing it onto the picture drawing surface. In this state, plural beams are separated spatially and made incident on the lens systems 50, 60, 70, 80 and 90 so as to have center axes being different from each other. That is, when said beams are made incident on the lens systems 50, 60, 70, 80 and 90, since the beams are separated spatially, an incident light can be set by a physical means such as a mirror, etc. without using a means utilizing a polarized light. In such a way, three pieces or more of beams can be synthesized in the same position on the deflector PM. Also, by following it up, a spot formed on the picture drawing surface can be separated by a prescribed distance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-beam scanning device that simultaneously scans a plurality of beams to form an image on a drawing surface.

[Prior Art and Problems to be Solved by the Invention] In this type of scanning optical device, it is necessary to use one deflector to deflect a plurality of beams that are 0N10FF by mutually different drawing signals. The beams need to be combined at the same position on the deflector in order to maintain convergence characteristics on the drawing surface.

Here, when two beams taking different optical paths are directed to a deflector and combined on the same optical path, Japanese Patent Laid-Open No. 60-166
As shown in Japanese Patent No. 916, a method is generally used in which the polarization directions of the beams are shifted by 901' from each other and the beams are combined using a polarizing beam splitter.

However, when three or more beams are to be combined, it is no longer possible to combine the beams using only the polarization method described in item 1.

In addition, if the spacing between scanning lines in the sub-scanning direction is set to be less than the spot diameter in order to increase the drawing density, if adjacent scanning lines are scanned simultaneously, interference will occur where the spots overlap, resulting in poor drawing characteristics. It becomes stable.

As a means to avoid this problem, it is possible to have a configuration in which spots formed simultaneously during drawing are scanned not on adjacent lines but on one or more lines separated from each other. According to this configuration, the plurality of spots can be spaced apart in the sub-scanning direction, thereby eliminating deviations in scanning timing. However, in this case, there are restrictions on the spot interval and the movement pitch for each scan, and electrical control becomes complicated.

If we assume a configuration in which adjacent lines are drawn simultaneously to prevent complication of control, increasing the spacing in the sub-scanning direction will reduce the drawing density, so the spot spacing should be adjusted to avoid interference in the main scanning direction. You need to move it a sufficient distance to prevent it.

Note that the spots may be spaced apart in both the main scanning direction and the sub-scanning direction.

As a method of shifting the spot in the main scanning direction,
As shown in Japanese Patent No. 1-261715, there is a method using a plurality of semiconductor lasers and a plurality of collimating lenses, making laser beams incident on a deflector from different directions, and combining the laser beams on the deflector.

However, in this method of combining light beams using different optical systems, the frame used to mount each optical element is always larger than the light beam, so the arrangement is restricted by this frame and the incidence of the light beam is limited. If the angular difference becomes too large, the scanning area on the drawing surface by each light beam will deviate greatly.

What can be used for drawing is the overlapping portion of each scanning area, so the above configuration cannot achieve high scanning efficiency, and is also limited by the size of the deflector, especially the deflector for each beam. Since the effect (change in deflection point in the case of a polygon mirror) is different, lens performance deteriorates. Furthermore, since each spot is separated by a large distance, scanning a portion of the scanning lens system with different characteristics and controlling using the same scanning signal will result in scanning deviation for each spot.

[Object of the invention] This invention was made in view of the above problems, and
An object of the present invention is to provide a multiple beam scanning device capable of combining three or more beams at the same position on a deflector.

[Means for solving the ff problem] In order to achieve the above object, the present invention spatially separates a plurality of beams and causes them to enter a lens system so as to have different central axes, and this lens system It is characterized in that a plurality of beams are combined at the same position on the deflector.

That is, since the beams are spatially separated when entering the lens system, it is possible to set the incident light by physical means such as a mirror, rather than by means using polarization. Each light beam is combined at the same position on the deflector, but each light beam may overlap when exiting from the lens system, and even if the light beam diameter is large, a minute separation angle can be achieved without physical constraints such as a frame. Can be set.

By appropriately setting this amount of separation in the main scanning direction and the sub-scanning direction, it is possible to eliminate the influence of interference during high-precision #lt image.

Note that when a polygon mirror is used as a deflector and an fθ lens is used as a scanning lens, the center distance between the spots on the drawing surface formed by two beams having an angle of Δθ when combined on the polygon mirror is , f·Δθ.

The optical system that separates the light beams and combines them at a predetermined position may be a convergent system or an afocal system.

As an example, for an afocal beam expander system,
FIG. 5 shows a case where the light beams are incident symmetrically on the optical axis.

This system consists of two lenses Is and L2, each of which is converted into a thin lens with focal ratios jlf+(<0) and f2()0) for display. Position S in front of lens L1
If the principal rays incident at the incident height hi and the angle θi are synthesized at an angle θp at the polygon mirror surface located at a position d behind the lens Le, then the distance between the position S and the polygon mirror surface is The optical matrix is: where M=f*/f+.

Therefore, Mhi+(f+ +f2+Ma+(d/M))・θ1=
0hi=-(θi/M)・(f++f, +Ma+(d/
14))=-θplf++fa+Ma+(d/M)).

Here, if 3 is the position of the first surface when the lens system is converted into a thick-walled lens system with a plurality of lenses, it is sufficient that the two light beams are separated at about 1js. That is, it is necessary that 2hi>Di, where Di is the diameter of the incident light beam.

This condition holds that if fl<Ol, that is, Mho, then θi
Since the signs of and θp are the same, and 0 in the above equation is positive, the arrangement is as shown in FIG. 5, and separation is possible.

Conversely, in the case of fl)O, M<Q, the signs of θi and θp are different, and this cannot be realized unless a and d are made very long and the value within 0 is negative.

However, even in such a case, for example, the sixth
If a relay lens LR is provided at the focal point as shown in the figure, an optical matrix can be easily realized as shown in the figure.

This relay lens LR does not actually need to be placed on the condensing point, but if the principal point is shifted by using a plurality of lenses, the lens surface can be shifted from the condensing point. Therefore, the influence of dust, scratches, etc. on the lens surface can be reduced.

If we consider the relay lens LR as part of the lens L1, then the lens system consisting of the lens KL+ and the relay lens LR has a focal length f (and the distance between principal points is negative. Therefore, even this relationship is It is sufficient to replace the relay lens LR with a plurality of thick lenses to achieve a satisfactory result, increasing the degree of freedom in design.The same can be said of the relay lens LR being considered as a part of the lens L2.

Furthermore, even when considering the relay lens LR and the lens L+ separately, the effect can be enhanced by configuring them with a plurality of lenses so that the distance from a, that is, the first surface of the lens L1 to the first principal point is large. can.

Furthermore, by predetermined combinations of beam expander systems such as those shown in FIG. 5 or 6, the degree of freedom in configuration is increased and the magnification of the beam system can be increased.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 to 4.

FIG. 1 is an explanatory diagram of the arrangement of an optical system of a photoplotter according to an embodiment, and FIGS. 2 and 3 are schematic explanatory diagrams of a part thereof developed along the optical axis.

This photoplotter splits the laser beam emitted from the argon laser 10 as a light source into three beams, two of which form two spots on the drawing surface, and the remaining one to accurately position the spot. It is used as a monitor light to detect. The spots on the drawing surface simultaneously scan adjacent scanning lines at predetermined intervals in the main scanning direction by rotation of the polygon mirror PM.

Note that, as mentioned above, the light beam emitted from one light source is divided into three parts, combined again, and scanned by the same deflector, so in this optical system, the light beam for drawing and the light beam for monitoring are deflected. The two drawing light beams are made to enter the same lens from different directions and are combined on the same optical path. This combination method is permissible because, as described above, the drawing spot is formed by shifting it in the main scanning direction.

Next, the configuration of each part of this device will be explained along with its operation.

The laser beam emitted from the argon laser 10 is transmitted through a pinhole 11 to a half mirror 12 with a 5% reflection.
divided. The laser beam reflected by this half mirror 12 is used as a monitor light beam 9.

On the other hand, the laser beam that has passed through the half mirror 12 has its polarization direction rotated by 90@ by the first 1/2 wavelength plate 13, and the light intensity is adjusted by the barrier pull filter 14 so that 50% is reflected and 50% is reflected.
The two 0-divided light beams, which are further divided into 1 by the first beam splitter 15 with % transmission, are used as drawing light beams that form two spots separated on the drawing surface.

The first drawing light beam 1 transmitted through the first beam splitter 15 is transmitted to the first drawing ^0 modulator 1 via a lens 16.
Focus the light on position 7.

This human O modulator 17 diffracts the laser beam incident from the direction satisfying the Bragg condition by inputting the ultrasonic wave to the transducer, and converts the input ultrasonic wave into 0N.
By performing 10FF, the laser beam can be switched to zero-order light and first-order light, and the first-order light is used as a drawing light beam. The AO modulator 17 is controlled by a write signal which is dot-by-dot exposure information for the drawing surface.

The primary light, which is the modulated ON light, is made into a parallel light beam again by a lens 18 provided behind the AO modulator 17, and then passed through a mirror 19 to a first light beam direction adjustment device consisting of four prisms. The beam is deflected by a predetermined angle by the lens 40 and is incident on the lens system 50 by the mirror 20.

On the other hand, the second beam reflected by the first beam splitter 15
The drawing light beam g2 is made into a convergent light via the lens 16', is reflected by the mirror 21, and is transmitted to the second drawing AO modulator 17°.
incident on . The function of the AO modulation@17' is the same as that of the first drawing AO modulator 17 described above. However, the signal that drives this second drawing ^0 modulator 17° is a signal for scanning a line that is shifted by one line from the signal input to the first drawing ^0 modulator 17. be.

The primary light emitted from the 2nd m[li AO transformer 17° passes through the lens 18' and passes through the second
The beam is deflected by a predetermined angle by the beam direction adjusting device 40°, and enters the lens system 50.

The lens 16.16° has the configuration shown in Table 1 on page 13, and the lens 18.18° has the configuration shown in Table 2.0 In the table, f is the focal length of the entire system; rl is the radius of curvature of the first surface of the lens system, di is the distance between the first surface and the i+1th surface (lens thickness and air gap), and nl is the refractive index of the medium between the first surface and the i+1th surface. ing.

Table 1 It is 127.89.

Table 2 127, 89.

The first and second beam direction II4 adjusting devices in Table 3 are composed of a first prism group P1 and a second prism group P2 each having two prisms, as shown in FIG.

The configurations of these prisms are shown in Table 3 on page 13.

Here, in FIG. 4, an X axis parallel to the direction of incidence of the light beam and y and z axes perpendicular to this are set. Figure 4 (A) 1
-7 plane is the cross section in the main scanning direction, X-2 in Fig. 4(B)
The plane shows a cross section in the sub-scanning direction.

The first prism group P1 includes first and second prisms 41 and 42.
are arranged so that each input/output end face is parallel to the y-axis, and the first
The prism 41 is rotatably adjustable around a rotation axis parallel to the y-axis.

The third and fourth prisms 43 of the second prism group P2
．． 44 is also arranged in the same manner as the first prism group P1 in terms of their relative relationship, but each entrance and exit end surface has two
The third prism 43 can be rotated around a rotation axis parallel to the z-axis.

In this device, by rotationally adjusting the first prism 41 and the third prism 43, the direction of the emitted light beam can be finely adjusted according to the relationship between the incident angle and the declination angle. In this example, the first and second drawing light fluxes ffi Ift
have their central axes at an angle of 0.27° in the main scanning direction and 0.034° in the sub-scanning direction, and 3.
8I, 0.48+nm1l in the sub-scanning direction! It is configured such that the light enters the second lens system 70 from the position where the light is directed.

In addition, the first prism group PI and the second prism 1njPt
are the directions of the luminous flux in the X-Z plane m y4!1
．． Since it is involved only in adjusting direction mi within the x-y plane and does not interfere with adjustment in other directions, adjustment in each direction can be performed independently.

Now, the first lens system 50 into which the light flux emitted from the above-mentioned light flux direction adjustment device @40.40' enters, has a three-element structure r + - + J as shown in Figure 3 and Figure 4. A lens that converges the incident laser light. This first lens system has a long distance from the first surface to the first principal point to facilitate separate incidence.

Further, the distance between the principal points is negative, and the entire optical system is made smaller.

A correction AO modulator 22 for correcting the influence of the surface tilt of the polygon mirror PM is provided 62 m+n in air equivalent distance from the focal point of the first lens system 50.

The laser beam for drawing that is emitted from the correction AO modulator 22 and reflected by the mirror 23 is transmitted through a relay lens system 60 consisting of two "10-" lenses.
The position of the light beam is corrected, and the light beam and the light beam overlap and enter the second lens system 70, which is composed of two lenses.

The laser beam for drawing, which is made into a parallel beam by the second lens system 70, is reflected by the mirror 24 and combined with the monitor light by the first polarizing beam splitter 25. That is, the monitor light 9 divided by the half mirror 12
. is reflected by the mirrors 26 and 27, enters the first polarizing beam splitter 25 as S-polarized light, and is reflected.

On the other hand, the two drawing light beams are made to have a different polarization direction from the monitor light by the first 1/2 wavelength plate 13, and are incident as P-polarized light, so they are transmitted as they are. The monitor light flux is the second 172 wavelength plate 28.
The polarization direction is rotated by 908, respectively, and "-
3rd lens system mark with 4-element configuration of 10~+'', mirror 29
The light enters a fourth lens system 90 consisting of two lenses "++" through the lens system 90.

The first lens system 50 and the second lens system 70 have a magnification of 1.67.
It constitutes the first beam expander system of 0.0
．． Expand the 7φ beam to 1.17φ. And the third
The lens system 80 and the fourth lens system 90 constitute a second beam expander system with a magnification of 21.4 times, and the two drawing light beams are expanded from 1.17φ to 25φ.

This embodiment has a configuration in which the beam expander system shown in FIG. 5 is provided behind the beam expander system shown in FIG. 6 described above.

The two drawing light beams and the monitoring light beam are directed to a polygon mirror PM via two mirrors 30 and 31, and are reflected and deflected by this polygon mirror PM.

Note that the two drawing light beams are combined at the same position on the polygon mirror at an angle of 27 degrees, and then reflected.

The relay lens system 60 connects these beam expanders.
It has a function of making the correction AO modulator 22 and the polygon mirror PM conjugate without being involved in the operation of the system, and correcting the deviation of the light beam on the polygon mirror due to surface tilt correction.

The configurations of the lens system to the fourth lens system described above are as shown in Tables 4 to 8 on pages 19 and 20.

The light beam reflected by the polygon mirror PM is converged by an fθ lens 100 with a focal length of 151 mm, and the drawing light beam passes through the second polarizing beam splitter 32 to form two spots with a diameter of 5 μm on the drawing surface.

On the other hand, the monitor light is reflected by the beam splitter 32 and enters the light receiving optical system 34 via a scanning correction scale 33 having a striped pattern perpendicular to the scanning direction. The light receiving optical system 34 outputs a pulse having a frequency proportional to the scanning speed based on a change in the amount of transmitted light of the beam scanning the scale 33.

The air-equivalent distance from the sixth surface of the fourth lens system 90 in Table 4 to the correction AO modulator 22 is 54.67, and the air-equivalent distance between the focal point of the lens system and the AO modulation surface is 81. .95
It is.

Table 5 The air equivalent distance is 140.38.

Table 6 It is 76.55.

It is 296.94 in Table 7 and Table 8, and the distance from the fourth surface of the fourth lens system 90 to the polygon mirror PM is 1281.00.

The two spots formed on the drawing surface are spaced apart by 20 μm in the main scanning direction and 2.5 μm, which is one line interval, in the sub-scanning direction.

In the above embodiment, only an example was described in which three beams are used to distinguish the drawing light beam and the monitor light beam by polarization, but the present invention is not limited to this, and for example, two beams for drawing are used. Not only can it be applied when only one beam is used, but it can also be used in a configuration in which four or more beams are combined.

[Effects] As described above, according to the present invention, since a plurality of beams are spatially separated and made incident on the lens system, three or more beams can be combined on the deflector.

Additionally, the spots formed on the drawing surface can be separated by a predetermined distance, and even when the pitch of the scanning line is set smaller than the spot diameter, the influence of interference can be removed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the arrangement of an optical system showing an embodiment of a multiple beam scanning device according to the present invention. FIG. 2 is a cross-sectional view in the main scanning direction showing a part of the optical system shown in FIG. FIG. 3 is a sectional view in the sub-scanning direction similar to FIG. 2. FIG. 4(A) and FIG. 4(B) are explanatory diagrams showing a cross section of the beam direction adjusting device. FIGS. 5 and 6 are explanatory diagrams of a beam expander system showing the principle of the present invention. 10... Argon laser (light source) 40.40°... Luminous flux direction adjustment device 50.60. To, 80.90... Lens system 100.
...fθ lens (scanning lens) PM...polygon mirror (deflection@)

Claims (1)

[Scope of Claims] A light source unit that emits a plurality of beams; The plurality of beams are incident at mutually different angles and from different positions to the extent that they can be spatially separated, and after being emitted, the plurality of beams are emitted at the same predetermined position on an optical path. a lens system that overlaps the plurality of beams with each other; a deflector that is provided at a position where the plurality of beams overlap and deflects the beams; and a deflector that separates the deflected beams in a direction in which the beams are scanned by the deflector and in a direction perpendicular thereto. 1. A multiple beam scanning device comprising: a scanning lens that focuses light onto a drawing surface.