JP3490773B2 - Laser drawing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser drawing apparatus used when forming a circuit pattern on a substrate.

[0002]

2. Description of the Related Art When forming a circuit pattern on a substrate, a photopolymer or the like is evenly deposited on a substrate on which a thin film of a conductive metal material such as copper is uniformly deposited, and this substrate is exposed and baked. There is used a method in which the circuit pattern formed on the exposure and baking mask is exposed and baked by irradiating the substrate in this state with ultraviolet light or the like by covering with a working mask.
In this method, after exposing and baking, the exposed photopolymer on the substrate is washed away with a solvent and treated with a chemical solution that corrodes copper, etc., because the part where the photopolymer remains adhered remains uncorroded. The same circuit pattern as the mask circuit pattern can be formed on the substrate. However, according to such a circuit pattern manufacturing method, the time and man-hour burden required for the inspection of the exposure and printing mask, which is indispensable in the manufacturing process, is large, and the exposure and baking mask is exposed to humidity and temperature to prevent expansion and contraction. There is a heavy administrative burden, such as protection from changes and protection from dust and scratches.

On the other hand, there is also known a manufacturing method in which a laser beam is scanned on a substrate by a polygon mirror or the like to directly draw (exposure) the substrate without using an exposure printing mask. According to this method, the above-mentioned problems in the manufacturing method using the exposure printing mask can be alleviated. However, in this manufacturing method, when the laser light is reflected by a polygon mirror or the like and then imaged on the substrate through the lens,
There is no problem with the laser light scanned on the meridian of the lens, but the laser light that passes through other than the meridian is scanned as curved as it passes through a position away from the meridian, which causes distortion in the drawing light. is there.

[0004]

SUMMARY OF THE INVENTION The present invention has been made on the basis of such a consciousness as described above, and it is possible to improve the drawing speed without using an exposure printing mask and to scan the drawing surface. An object of the present invention is to provide a laser drawing apparatus capable of suppressing distortion of a drawn image as much as possible.

[0005]

SUMMARY OF THE INVENTION A laser drawing apparatus of the present invention is a dividing means for dividing a laser beam from a laser light source into a plurality of drawing light fluxes arranged in a line; the drawing light flux in a row is reflected by its reflection surface. A deflection mirror for scanning the drawing surface; and a reflected light from the reflecting surface of the deflection mirror is condensed to form an image on the drawing surface. The image height of the point image on the drawing surface is deflected. A laser drawing apparatus comprising: a scanning optical system that is proportional to the angle θ and satisfying the following conditional expression (1). When δ = cos ^-1 {2cos α · cos ² ω − cos α} γ = tan ⁻¹ {sin α / (2cos α · sin ω · cos ω)}, (1) δ sin γ-α <p / f However, f: scanning Focal length of the optical system, α: incident angle in the sub-scanning direction with respect to the reflecting surface of the deflecting mirror, ω: normal line of the reflecting surface of the deflecting mirror is a bisector of the optical axis of the scanning optical system and the incident optical axis Angle: p: pitch of a plurality of drawing light fluxes in a line, δ: angle between the drawing light flux reflected by the reflecting surface of the deflection mirror and the optical axis of the scanning optical system, γ: deflection mirror An angle formed by the main scanning direction and a line connecting the image forming point of the drawing light beam reflected by the reflecting surface on the drawing surface and the intersection of the optical axis of the scanning optical system with the drawing surface.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to illustrated embodiments. FIG. 1 shows a laser drawing apparatus 11 to which the present invention is applied.
FIG. 3 is an external perspective view showing the whole of FIG. Laser drawing device 11
Has an argon laser device 12 on the table 10, and beam benders 13, 23-25, 28-29, 3
0, 35, 41, 44, 45, 54, adjustment targets 15, 17, 33, half prism 16, beam bender (half mirror) 14, and lenses 52, 53, 65.
To 71. The laser drawing device 11 further includes acousto-optic modulators 19, 20, beam separators 21, 2,
2. Pitch converting condensing optical system 26, 31, 27, 32,
Eight-channel acousto-optic modulators 36 and 37, beam bender 38, condensing optical system 34, λ / 2 plate 39, polarization beam splitter 40, image rotator 43, polygon mirror 46, fθ lens 47, and Y-scale condensing lens. Four
8, condenser lens 49, Y scale 50, mirror 6
0, monitor light mirrors 51a and 51b, and a Y-scale photodetector 62. The adjustment targets 15, 17, and 33 are used for the drawing light fluxes L2 and L3 and the monitor light L when the argon laser device 12 is replaced.
It is an index for confirming the optical path of m.

A substrate setting device (not shown) for setting the substrate S close to the laser drawing device 11 so as to be positioned on the drawing table surface T (only the position of the surface is shown by a chain double-dashed line) which is an image surface. ) Is provided. This substrate setting device is arranged in the Z direction (the sub-scanning direction of the polygon mirror 46 (see FIG. 1).
Z table (not shown)
And a swing mechanism (not shown) that swings in the vertical direction of FIG.

Argon laser device (laser light source) 12
Is water-cooled, has an output of 1.8 W, and is configured to emit a laser beam L1 having a wavelength of 488 nm. The acousto-optic modulators 19 and 20 respectively perform correction for removing the light amount difference between the light beams L2 and L3 divided by the half prism 16, and control means for finely tilting each reflecting surface 46a of the polygon mirror 46. The correction is performed based on the data regarding the surface tilt of each reflecting surface 46a stored in the storage unit 8 of FIG.

The light beams L2 and L3 emitted from the acousto-optic modulators 19 and 20 are incident on the beam separators 21 and 22, respectively, and the beam separators 21 and 22 respectively form eight beams for first and second drawing. It is divided into luminous fluxes L5 and L6. Each of the beam separators 21 and 22 has eight emission holes along its longitudinal direction.

The first and second drawing light beams L5 and L6 emitted from the beam separators 21 and 22 are incident on the pitch converting condensing optical systems 26, 31 and 27, 32, respectively. The pitch converting condensing optical systems 26, 31 and 27, 32 are respectively beam separators 21, 22.
The pitch of each of the first and second drawing light fluxes L5 and L6 divided into eight light fluxes in a line by
Match the pitch of the acousto-optic modulators 36, 37 of the channel.

The polarization beam splitter 40 is fixed in a state where the half mirror surface 40a is inclined by 45 ° with respect to the sub scanning direction (Z). Polarizing beam splitter 40
Is a first drawing light beam L5 in one line that is deflected by the beam bender 38, and a second drawing light beam L6 that is in one line and passes through the λ / 2 plate 39 to enter. Alternately mixed at a predetermined pitch, and in the Y direction (polygon mirror 4
6 along the main scanning direction (vertical direction in FIG. 1) again. Although the polarization direction of the first drawing light beam L5 is not changed, the second drawing light beam L6 does not change its polarization direction.
The polarization direction is 90 relative to that of the drawing light beam L5.
Rotated by °. In this way, the drawing light beams L5 and L6 whose deflection directions are different from each other by 90 ° are alternately combined by the polarization beam splitter 40 as described above, and aligned in a line.

Each of the acousto-optic modulators 36 and 37 is constructed on the basis of the acousto-optic effect that the refractive index of a crystal of tellurium dioxide or the like is slightly changed when an ultrasonic wave is applied to the crystal. When a high-frequency electric field is applied to the provided transducer, ultrasonic waves of a traveling waveform are generated inside the crystal to Bragg-diffract the laser light, and the incident laser light is transmitted when the high-frequency electric field is not applied. You can Therefore, by switching the application of the high frequency wave to the acousto-optic modulator 36 (37), the incident light, that is, the drawing light beams L5 and L6 can be switched on and off freely. Each of the eight channels of the acousto-optic modulator 36 (37) includes a first drawing light flux L5 and a second drawing light flux L5 that form a line.
L6 is made incident on each of them, and the incident light beams L5, L
6 are arranged in a line so as to be modulated in the left-right direction (Z direction in FIG. 1).

8-channel acousto-optic modulators 36, 37
Are respectively the first and second drawing light fluxes L divided into eight.
5 and L6, the function of removing the variation in the light amount, and the drawing light fluxes L5 and L6, each of which is eight, are independently turned on and off by the control means 8 based on predetermined data, and are divided by the beam separators 21 and 22. It has a function of giving individual on / off drawing information to each of the divided drawing light fluxes of L5 and L6. The acousto-optic modulators 36 and 37 are
This laser drawing apparatus 11 using a polygon mirror 46 as a scanning means and an fθ lens as a light collecting means for the drawing light beams L5 and L6 scanned by the polygon mirror 46.
In FIG. 6, the drawing image i scanned by the drawing table surface T with respect to the drawing image i is not distorted as shown in FIG.
5, give to L6.

The fθ lens (scanning optical system) 47 is used to obtain a constant velocity with respect to the scanning surface (drawing surface) of the drawing light beam scanned by the polygon mirror (deflection mirror) 46. The fθ lens 47 solves the problem that the point image position of the drawing light beam on the scanning surface is not proportional to the deflection angle θ, and the scanning is performed faster by tan θ toward the upper side of the scanning surface. The image height of the point image of the drawing light beam on the scanning surface is proportional to the deflection angle θ formed by the reflected light beam and the optical axis of the fθ lens 47.

Therefore, the drawing light beam can be scanned at a constant speed, but when the fθ lens 47 is used, the following problems occur. That is, the plurality of divided drawing light beams reflected by the polygon mirror 46 are, as shown in FIG.
Since the polygon mirrors 46 are scanned in a line in the sub-scanning direction (Z), as the height increases in the sub-scanning direction,
Distortion (FIG. 17) occurs in the drawn image i that is scanned by passing through the position away from the optical axis O of the fθ lens 47.

The laser drawing apparatus 11 according to the present invention has the following features in order to solve such a problem. That is, the focal length of the fθ lens 47 is f, the image height of the polygon mirror 46 in the main scanning direction (Y) is y, the image height of the polygon mirror 46 in the sub scanning direction (Z) is z, and the reflection of the polygon mirror 46 is reflected. The incident angle in the sub-scanning direction (Z) with respect to the surface 46a is α, and the reflecting surface 4 of the polygon mirror 46 is
The normal m of 6a forms an angle ω with respect to the bisector of the optical axis O of the fθ lens 47 and the incident optical axis, and the pitch of a plurality of drawing light beams L5 and L6 in a row is p (FIG. 5). ), And
The angle formed by the drawing light beams L5 and L6 reflected by the reflecting surface 46a of the polygon mirror 46 and the optical axis O of the fθ lens 47 is δ.
And Further, the image forming point of the drawing light beams L5 and L6 reflected by the reflecting surface 46a of the polygon mirror 46 on the drawing surface and f
When the angle formed by the line connecting the intersection of the optical axis O of the θ lens 47 and the drawing surface and the main scanning direction (Y) is γ (FIG. 2)
(FIG. 5), it is configured to satisfy the following conditional expression (1). The image heights in the main and sub-scanning directions are respectively given by y = fδcos γ z = fδsin γ, and δ = cos ⁻¹ {2cosα ・ cos ² ω− cosα} γ = tan ⁻¹ {sinα / (2cosα ・ sinω ・ cosω )}, (1) δsin γ-α <p / f In this conditional expression, the normal m of the reflecting surface 46a and the fθ lens 47
The angle ω formed with the optical axis O of the polygon mirror 46, that is, the reference of the rotation angle ω of the polygon mirror 46 is, as shown in FIG.
It is assumed that the normal line m divides β formed by the drawing optical flux (incident luminous flux) L5 and L6 incident on the optical axis O of the fθ lens 46 into two equal parts.

Therefore, the polygon mirror (deflection mirror) 4
6 and the laser drawing apparatus 11 using the fθ lens 47 as a condensing means for the drawing light beams L5 and L6 scanned by the polygon mirror 46, the deviation amount of the drawn image i in the sub-scanning direction (Z). Can be smaller than 1 pitch p (FIG. 5). Then, in the present laser drawing apparatus 11, fθ
Since the portion of the lens 47 relatively close to the optical axis O is used for drawing, and the portion near the peripheral portion away from the optical axis O is not used for drawing, the reflecting surface 46a of the polygon mirror 46 is used.
When a plurality of divided light beams L5 and L6 reflected by the laser beam are scanned in a state of being arranged in a line, distortion occurring in the drawn image i (FIG. 17) to be scanned is suppressed as much as possible, and as shown in FIG. Can be drawn. From the above conditional expression, the fθ lens 47
It can be understood that it is preferable to use a lens having a large focal length f as the above in order to further reduce the distortion of the drawn image i.

Although the f.theta. Lens 47 is shown in FIG. 3 as if it were composed of one lens, the f.theta. Lens 47 is composed of a combination of several concave and convex lenses as described above. There is.

On the other hand, the monitor light Lm is the drawing light flux L2.
(L5) and L3 (L6) are light beams of a different system to have a longer optical path length, and a position spatially separated from the drawing light beams L5 and L6 by a predetermined distance is used as an optical path. Monitor light Lm
Is deflected by beam benders 54, 25,
The light passes through a position separated from the second drawing light beams L5 and L6 by a predetermined distance, and further approaches the drawing light beams L5 and L6 after being deflected by the mirrors 35 and 60, and passes through the lens 71, the beam bender 41, the lens 52, and the like. , The drawing light flux L5,
The path is changed so that it is located right beside the optical path of L6.

The image rotator 43 is arranged in a line (substantially the same plane) so that the point images of the adjacent first and second drawing light beams L5 and L6 can be superposed on each other during scanning by the polygon mirror 46. It is a mirror system for arranging 16 drawing light fluxes L5 and L6 arranged side by side on the drawing table surface T at an angle. Therefore, until the first and second drawing light beams L5 and L6 are incident on the image rotator 43, 16 of the first and second drawing light beams L5 and L6 are arranged in a line in a direction parallel to the main scanning direction (Y) of the polygon mirror 46. However, when the image is emitted from the image rotator 43, for example, as shown in FIG.
As shown in FIG. 5, it is rotated by a predetermined angle in the clockwise direction in FIG.

The first and second drawing light fluxes L5 and L6 and the monitor light Lm are further deflected by the beam benders 44 and 45, and then enter the reflecting surface 46a of the polygon mirror 46. When the polygon mirror 46 rotates counterclockwise in FIG. 8 about the rotation axis 73, the polygon mirror 46 continuously changes the deflection angle θ (see FIG. 3) and is rotated by the respective reflecting surfaces 46a in the same direction. The first and second drawing light fluxes L5,
Scan L6 and monitor light Lm. As a result, the first and second drawing light beams L5 and L6 respectively pass through the fθ lens 47 and the condenser lens 49 and are imaged on the substrate S located on the drawing table surface T. Further, the polygon mirror 46 can be rotationally moved about its rotary shaft 73 via an adjusting means (not shown), whereby the perpendicularity of the main scanning line to the sub-traveling line can be adjusted.

The monitor light Lm that has passed through the fθ lens 47 and the condenser lens 49 together with the first and second drawing light fluxes L5 and L6 is sequentially reflected by the monitor light mirrors 51a and 51b, and is deflected by 180 °. The light enters the Y scale 50 arranged at a position equivalent to the image plane of the surface T. This Y scale 50 has a slit formed in glass, as in the linear encoder. Then, the monitor light Lm is transmitted through the Y scale 50, then reflected and condensed by the long mirrors 63 and 64, respectively, and Y
The light is further condensed by the scale condenser lens 48 and is incident on the Y-scale photodetector 62. Based on the position of the monitor light Lm detected by the Y-scale photodetector 62, the positions of the 16 first and second drawing light beams L5 and L6 arranged in line are judged, and the control means 8 based on this judgment data 16 signals of the first and second drawing light fluxes L5 and L6 are individually given the drawing information by the signal.

The point images of the first and second drawing light fluxes L5 and L6 which are slightly inclined with respect to the drawing table surface T are 8
Through the acousto-optic modulators 36 and 37 of the channels, the point image diameter is corrected to be 30 μm, for example. Thereby, the variation in the light amount of each point image as shown in FIG. 14 is adjusted as shown in FIG. In this embodiment, the spots of the drawing light beams L5 and L6 are the acousto-optic modulator 3
6 and 37, the mutual interval P (FIG. 12) is, for example, 5
The pitch is adjusted to be μm.

The drawing line L (FIG. 15) formed by each point image along the sub-scanning direction (Z) is defined by the acousto-optic modulators 36 and 37.
The drawing light flux L5
And L6 are provided with an interval c for preventing interference between the point images, therefore, for example, even if the drawing light beam L6 at the bottom of FIG. The drawing line L does not become a line. Therefore, in the present laser drawing apparatus 11, the lowermost drawing light beam L5 is exposed, and then the next drawing light beam L6 is not directly exposed, but is exposed after a predetermined time. As a result, the drawing light beam L6 next to the point image of the drawing light beam L5 previously exposed is obtained.
Since it is possible to properly superimpose the point images of, the line L as shown in FIG. 15 can be drawn by continuously performing this operation. In this case, when the point image positions of the line L vary as shown in FIG. 12, the modulation timings of the eight-channel acousto-optic modulators 36 and 37 are appropriately changed to correct as shown in FIG. You can

The present laser drawing apparatus 11 having the above structure
Can be operated as follows. First, a positioning hole (not shown) of the substrate S on which a circuit pattern is to be formed
Are aligned with corresponding portions of the substrate setting device, and the substrate S is properly set in the device. As a result, the substrate S is slidable in the sub-scanning direction (Z) of FIG. 1 by the Z table and swing mechanism (not shown) of this substrate setting device, and at that position a rotation axis (not shown). It is set so that it can swing about the axis.

In this state, the argon laser device 1
When the laser beam L1 is oscillated and the irradiation of the laser beam L1 is started, the laser beam L1 is first deflected by the beam bender 13, passes through the adjustment target 15, and then enters the half prism 16, which is then reflected by the half prism 16. , And is split into a light beam L2 that goes straight and a drawing light beam that is deflected by 90 ° and goes toward the half mirror 14. The drawing light beam is split through the half mirror 14 into a light beam L3 which is deflected by 90 ° and travels in parallel with the light beam L2, and a monitor light Lm which is directed toward the beam bender 54 and is deflected by 90 ° by the beam bender 54. To be done.

The light beam L2 is incident on the acousto-optic modulator 19 via the lens 65, the adjustment target 17 and the lens 67, and the drawing light beam L3 is transmitted through the lenses 66 and 68 to the acousto-optic modulator 20. It is incident. Then, the light quantity difference between the light fluxes L2 and L3 is removed by the acousto-optic modulators 19 and 20. The luminous fluxes L2 and L3 are further
Main scanning direction (Y) by beam separators 21 and 22
Is divided into eight first drawing light fluxes L5 and second drawing light fluxes L6 which are parallel to each other. The first and second drawing light fluxes L5 and L6 further pass through the pitch conversion condensing optical systems 26 and 27, respectively, and the beam bender 2
After being deflected by 90 ° at 8, 29, they are incident on acousto-optic modulators 36, 37 via pitch-converging condensing optical systems 31, 32, respectively.

The drawing light fluxes L5 and L6, which are each divided into eight light fluxes, are individually removed by the acousto-optic effect of the 8-channel acousto-optic modulators 36 and 37, and the control means is used. Drawing information is given from the acousto-optic modulators 36 and 37 based on 8.

The drawing light beam L5 emitted from the acousto-optic modulator 36 is deflected by 90 ° by the beam bender 38 and then enters the polarization beam splitter 40, and the drawing light beam L6 emitted from the acousto-optic modulator 37. Is the λ / 2 plate 39
After passing through, the polarization direction is changed, and then the light is incident on the polarization beam splitter 40. These drawing light beams L5 and L6
The individual drawing light fluxes, each of which has eight light beams, are sequentially combined by the polarization beam splitter 40, and are combined so as to be arranged in a line in the main scanning direction (Y).

Further, the control means 8 includes a polygon mirror 46.
The substrate setting device is operated in synchronism with the scanning of the drawing light beams L5 and L6 from, and the substrate S is slid on the drawing table surface T along the direction parallel to the sub-scanning direction (Z). Therefore, the circuit pattern is two-dimensionally drawn (exposed) on the substrate S by the drawing light beams L5 and L6 which are turned on and off at appropriate times in parallel with 16 16 lines which are slightly oblique to the main scanning direction (Y).

[0031]

As described above, according to the present invention, it is possible to provide a laser drawing apparatus capable of improving the drawing speed without using an exposure printing mask. Further, according to the present invention, when the light beam scanned by the deflection mirror is imaged through the scanning optical system, it is possible to suppress the occurrence of distortion in the drawn image to be scanned as much as possible.

[Brief description of drawings]

FIG. 1 is an external perspective view showing an entire laser drawing apparatus to which the present invention is applied.

FIG. 2 is an explanatory diagram for explaining the principle of scanning a drawn image in the laser drawing apparatus.

FIG. 3 is an explanatory diagram for explaining the principle of scanning a drawn image in the laser drawing apparatus.

FIG. 4 is an explanatory diagram for explaining the principle of scanning a drawn image in the laser drawing apparatus.

FIG. 5 is an explanatory diagram for explaining the principle of scanning a drawn image in the laser drawing apparatus.

FIG. 6 is a diagram showing an example of a drawn image drawn by the laser drawing apparatus.

FIG. 7 is an explanatory diagram for explaining the principle of scanning a drawn image in the laser drawing apparatus.

FIG. 8 is an enlarged perspective view showing a polygon mirror used in the laser drawing apparatus.

FIG. 9 is an explanatory diagram showing a state in which two drawing light flux groups are rotated.

FIG. 10 is an explanatory diagram showing a state when one of the two groups of drawing light fluxes is moved in the main scanning direction of the polygon mirror.

FIG. 11 is an explanatory diagram showing a state when one of the two groups of drawing light fluxes is moved in the sub-scanning direction of the polygon mirror.

FIG. 12 is a diagram showing a relationship between a single-line drawing light beam and a line drawn by the drawing light beam in a state before correction.

FIG. 13 is a diagram showing a relationship between a line of drawing light flux and a line drawn by the drawing light flux in a corrected state.

FIG. 14 is a diagram showing a relationship between a single-line drawing light beam and a line drawn by the drawing light beam in a state before correction.

FIG. 15 is a diagram showing a relationship between a line of drawing light flux and a line drawn by the drawing light flux in a state after correction.

FIG. 16 is an explanatory diagram for explaining an inconvenience during drawing using a polygon mirror and an fθ lens.

FIG. 17 is an explanatory diagram for explaining an inconvenience during drawing using a polygon mirror and an fθ lens.

[Explanation of symbols]

11 Laser drawing device 12 Argon laser device (laser light source) 16 Half prism 36 37 Acousto-optic modulator 21 22 Beam separator 39 λ / 2 plate 40 Polarizing beam splitter 43 image rotator 46 Polygon mirror (deflection mirror) 47 fθ lens (scanning optical system) i drawing image L1 laser light L2 L3 luminous flux L5 L6 Drawing light flux Lm monitor light S substrate T drawing table surface

Claims (3)

(57) [Claims] 1. A splitting means for splitting a laser beam from a laser light source into a plurality of drawing light fluxes arranged in a line; and scanning the drawing surface by reflecting the one row light fluxes for drawing on its reflection surface. And a scanning optical system in which the image height of the point image on the drawing surface is proportional to the deflection angle θ, and the reflected light from the reflecting surface of the deflecting mirror is condensed to form an image on the drawing surface. And satisfying the following conditional expression (1): When δ = cos ^-1 {2cosα ・ cos ² ω-cosα} γ = tan ^-1 {sinα / (2cosα ・ sinω ・ cosω)}, (1) δsin γ-α <p / f However, f: scanning Focal length of the optical system, α: incident angle in the sub-scanning direction with respect to the reflecting surface of the deflecting mirror, ω: normal line of the reflecting surface of the deflecting mirror is a bisector of the optical axis of the scanning optical system and the incident optical axis Angle: p: pitch of a plurality of drawing light fluxes in a line, δ: angle between the drawing light flux reflected by the reflecting surface of the deflection mirror and the optical axis of the scanning optical system, γ: deflection mirror An angle formed by the main scanning direction and a line connecting an image forming point on the drawing surface of the drawing light beam reflected by the reflecting surface and an intersection of the optical axis of the scanning optical system with the drawing surface. 2. The deflecting mirror according to claim 1, wherein the deflecting mirror is a polygon mirror having a large number of reflecting surfaces, and the rotation of the deflecting mirror scans a line of divided drawing light beams reflected by the reflecting surfaces in a main scanning direction thereof. A laser writing apparatus configured to. 3. The scanning optical system according to claim 1, wherein the image height of the point image of the drawing light beam on the drawing surface is proportional to the deflection angle θ formed by the optical axis and the reflected light beam. A laser drawing device that is an fθ lens for scanning at a constant speed.