JP3093877B2 - Disk for light beam recording device and light beam recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam recording device and a disk used in the light beam recording device.

[0002]

2. Description of the Related Art As a device for recording characters, images and the like on a recording material by using a light beam, for example, a laser beam is scanned based on computer output information and a character is recorded on a recording material such as a microfilm. A laser computer output microfilmer (laser COM) for directly recording information such as the above is known (JP-A-55-67722). In such a light beam recording apparatus, the light beam is deflected by a deflecting means such as a polygon mirror, and then formed on a recording surface of the recording material by a scanning lens to record information on the recording material.

In the above, an f · θ lens having an imaging relationship shown in the following equation (1) is used as a scanning lens.
The recording material is positioned on the focal plane (hereinafter referred to as an image plane) of the θ lens.

S = f · tan θ
(1) where s is the distance of the image point from the optical axis f is the focal length of the f-θ lens θ is the angle of incidence of the light beam with respect to the optical axis For reasons such as unevenness, the light beam deflected by the deflecting means and transmitted through the f · θ lens does not have a flat image plane. As an example, as shown in FIG. 11, after a laser beam emitted from a semiconductor laser 100 and collimated by a collimator 102 is deflected by a polygon mirror 104 along a scanning direction (the direction of arrow C in FIG. 11), f · θ When an image is formed on the recording surface of the recording material wound around the drum 108 by the lens 106, the focal position (beam waist position) of the laser beam is shifted from the recording surface depending on the deflection angle, and the image surface is shown by a broken line 110. (Hereinafter, this is referred to as a field curvature surface 110).

In FIG. 11, a portion where the beam waist position of the laser beam deviates from the recording surface (in particular, the curved surface
(Near the edge of the recording surface), the beam diameter of the light beam applied to the recording surface becomes larger than the beam diameter at the beam waist position, and the energy of the light beam applied to the recording surface per unit area decreases. Inconveniences such as partial blurring of characters and images recorded on the recording surface occur. In recent years, there has been an increasing demand for a light beam recording apparatus capable of recording an image of a larger size, which can be applied to an output device or the like in printing. Has become.

In order to solve this problem, an electro-optic lens that can electrically control the beam waist position of a light beam using a PLZT electro-optic ceramic or the like is used so that the field curvature surface becomes flat. Correction is conceivable. However, since the PLZT electro-optic lens has low light transmittance and large scattering, the power of the light beam cannot be used effectively, and is not suitable for recording a large-sized image. Further, the electro-optical lens is expensive, and there is a problem that the cost of the light beam recording apparatus increases.

In Japanese Patent Laid-Open Publication No. Hei 3-17610, a wedge-shaped prism is disposed on the optical path of a light beam before a deflecting means, and the prism is moved so as to be synchronized with the deflection by the deflecting means. Scanning optical devices have been proposed. The wedge-shaped prism can change the optical path length of the light beam by changing the light beam transmission position on the prism, and accordingly, the beam waist position of the light beam changes. Therefore, if the curvature of the image surface is corrected and the prism is moved so as to be flat, the beam waist position of the light beam can be matched with the recording surface.

However, the curved surface of the image is rarely a simple curved surface which is curved with a constant curvature (see FIG. 11). When the scanning speed of the light beam is increased, the prism cannot be moved accurately due to the inertia of the prism, and the image or the like is recorded at a high speed. It was difficult.
Further, even if the movement of the prism can follow the scanning speed of the light beam, since the apex angle of the light beam changes with the movement of the wedge-shaped prism, the distance between pixels changes and the image is distorted. There was also.

The present invention has been made in view of the above facts, and has as its object to provide a disk for a light beam recording apparatus and a light beam recording apparatus capable of recording an image or the like with high quality and at a high speed. .

[0010]

In order to achieve the above object, a disk for an optical beam recording apparatus according to claim 1 is rotatable and has a predetermined optical path length changing pattern along a rotation direction.
As down occurs, the optical path length changing unit which is part of changing the optical path length of the transmitted light beam formed by distributed along the rotational direction
However, the shape of the optical path length change pattern is the same as each other and
Multiple coaxial shapes so that the optical path length change degrees differ from each other
Are located .

According to a second aspect of the present invention, there is provided a light beam recording apparatus, comprising: a light beam emitting means for emitting a light beam; a deflecting means for deflecting the light beam emitted from the light beam emitting means;
A scanning lens that forms an image of the light beam deflected by the deflecting unit; a forming unit that forms a beam waist of the light beam between the light beam emitting unit and the deflecting unit; and a rotatable member near the beam waist. Placed in
An optical path length changing pattern determined so that an image plane formed by the deflecting unit and the scanning lens is substantially flat.
The portion that changes the optical path length of the transmitted light beam is distributed along the rotational direction so that
An optical path length changing unit that changes the shape of the optical path length changing pattern.
So that the optical path length change degrees are different from each other
A plurality of disks arranged coaxially with each other, and driving means for rotating the disks in synchronization with the deflection by the deflection means.

The invention according to claim 3 is the invention according to claim 2.
Detecting means for detecting a beam waist position of the light beam emitted from the scanning lens, and moving the disk in a direction intersecting the rotation direction so that the beam waist position detected by the detecting means is a predetermined position. moving means for moving along, as further comprising a
I have.

[0013]

According to the first aspect of the present invention, the disk is made rotatable and a predetermined optical path length changing pattern is generated along the rotation direction.
The part that changes the optical path length of the transmitted light beam so that it shifts
Are distributed along the direction of rotation to form the optical path length changing part.
I have. The optical path length of the light beam can be changed by changing the refractive index of the disk or changing the thickness of the disk. The disc has a predetermined refractive index distribution (light
In order to form the optical path length changing portion of the ( path length changing pattern) , various manufacturing methods (described later) which are already known as a refractive index distribution forming method can be applied.

As shown in FIG. 1, when an optical path length changing portion whose refractive index changes between n1 and n2 (where n1 <n2) is formed on the disk 10, the magnitude of the refraction of light on the surface of the disk 10 Varies depending on the refractive index n of a portion irradiated with light, and accordingly, the optical path length and the beam waist position change.

That is, when a convergent light beam is applied to a portion having a refractive index n1 (refractive index: small), the emission angle φ1 is relatively large, and the light beam emitted from the disk 10 is converged as shown by a broken line in FIG. You. Further, the refractive index n2 (refractive index:
When the convergent light beam is irradiated on the portion (large), the emission angle φ1 becomes smaller, and the light beam emitted from the disk 10
The beam waist position moves in the direction away from the disk 10 as shown by the solid line in FIG. As described above, the optical path length of the light beam can be changed by changing the refractive index, whereby the beam waist position can be changed.

As shown in FIG. 2, when the optical path length changing portion is formed by changing the thickness of the disk 12 between L1 and L2 (L1 <L2), refraction of light on the surface of the disk 12 is performed. Is constant, but the thickness L
The position at which refraction occurs changes depending on the size of the light beam, and the optical path length and the beam waist position change accordingly.

That is, the thickness L1 (thickness: small)
Is irradiated with a convergent light beam, the optical path length passing through the disk 12 is relatively short, and the light beam emitted from the disk 12 is converged as shown by a broken line in FIG. When a convergent light beam is applied to a portion having a thickness L2 (thickness: large), the optical path length passing through the disk 12 is increased, and the light beam emitted from the disk 12 is changed as shown by a solid line in FIG. The beam is converged, and the beam waist position moves in a direction away from the disk 12. Thus, even if the thickness dimension is changed, the optical path length of the light beam can be changed, whereby the beam waist position can be changed.

When a light beam is irradiated by rotating the disk as described above, the light beam irradiation position moves on the light path length changing portion along the rotation direction, and the light path length is changed in a predetermined light path length changing pattern. Will be. Therefore, the optical path length and the beam waist position of the light beam transmitted through the disk are changed with the rotation of the disk.

In a light beam recording apparatus, an image is recorded on a recording material by deflecting a light beam by a deflecting means and forming an image by a scanning lens. The curvature of an image plane formed by the deflecting means and the scanning lens is corrected. Optical path length change putter
If the optical path length changing portion is formed so as to generate an image, and the disk is rotated so as to synchronize with the deflection by the deflecting means, the image plane can be made flat, and an image or the like can be recorded with high quality. it can.

The distribution of the change in the optical path length that corrects the curvature of the image plane due to the scanning lens can be obtained as follows. That is, as shown in FIG. 3 as an example, the collimator 16 and the
Converging lens 18, a collimator 20 having a focal length f _1, a f · theta lens 22 of focal length f ₂ as a scanning lens arranged in this order, the drum 24 to the focal position of the laser beam imaged by the f · theta lens 22 Deploy. Collimator 2
A deflecting unit (not shown) is arranged between the 0 and f · θ lenses 22, and a disk 26 according to the present invention is arranged between the converging lens 18 and the collimator 20.

Here, assuming that the field curvature when the laser beam is deflected so as to have a specific deflection angle is α (the distance from the surface of the drum 24 to the beam waist position of the laser beam), the curvature α Displacement D for correcting
_C (= moving focal length: see also FIGS. 1 and 2) is obtained by the following equation (2).

[0022]

(Equation 1)

For example, if the focal length f ₁ is 10 mm and the focal length f
_{When 2} is 500 mm and the field curvature is 500 μm, (2)
From the equation, a displacement D _C = 0.2 μm is obtained. This displacement amount D
_{From C,} a parameter for correcting the focal position to match the surface of the drum 24, that is, an appropriate value of the refractive index or the thickness dimension can be obtained. For example, when changing the refractive index, the original refractive index of the disk 26 is set to n.
₁ , assuming that the refractive index after the change is n ₂ and the thickness dimension of the disk 26 is 1 (a constant value),

[0024]

(Equation 2)

It is determined by the above equation (3). As an example, if the thickness dimension 1 is 1 mm and the refractive index n ₁ is 2.0, the change in the refractive index is Δn = n ₂ −n ₁ = 0.008, and if the refractive index is changed by Δn, the focal position will be on the surface of the drum 24. Can be matched. The above is the case where the light beam is deflected so as to have a specific deflection angle.However, in the case where the light beam is deflected so as to scan along a predetermined direction, the scanning angle is obtained in the same manner as described above for each continuously changing deflection angle. Even if the degree of curvature of the image plane varies from lens to lens, the distribution of changes in the optical path length that corrects this curvature (optical path length change pattern)
G) Specifically, the distribution of the change in the refractive index or the thickness dimension can be obtained.

In the present invention, when the light beam is deflected so as to increase the scanning speed of the light beam, the rotation can be synchronized with the deflection by rotating the disk at a high speed, which is adversely affected by the inertia of the disk. Since there is no
Images can be recorded at high speed. Further, since it is not necessary to use a wedge-shaped prism and the surface of the disk can be made parallel, the apex angle of the light beam does not change, and no distortion or the like occurs in the image.

In the light beam recording apparatus, the position of the image plane of the light beam formed by the scanning lens is the temperature,
It changes due to changes in the surrounding environment such as humidity. If the position of the image plane of the light beam deviates from the recording surface of the recording material, problems such as an overall blurred image occur. For this reason,
The disk for a light beam recording device according to the invention of claim 1 is an optical disk
The optical path length change patterns have the same shape
And coaxial so that the optical path length change degrees are different from each other
Are arranged. Thus, Before moving the disk so that the light beam passes through either the optical path length changing unit in accordance with the position of the image plane which varies due to variations in the ambient environment
This makes it possible to keep the position of the image plane constant irrespective of changes in the surrounding environment, and to record images and the like with high quality.

According to the second aspect of the present invention, the image plane formed by the deflecting means and the scanning lens is formed to be substantially flat.
The defined optical path length change pattern does not occur along the rotation direction.
The part that changes the optical path length of the transmitted light beam
The optical path length changing unit distributed along the rotation direction is
The shapes of the optical path length change patterns are the same and the optical path length change
Are arranged coaxially so that the degree of
The disk is rotatably arranged near the beam waist of the light beam formed by the forming means. The disk is rotationally driven by the drive means in synchronization with the deflection by the deflection means.

Thus, as described in the operation of the first aspect of the present invention, the image plane formed by the scanning lens can be made flat, and images and the like can be recorded with high quality. . Also, the shapes of the optical path length changing patterns
And the optical path length change degrees are different from each other.
Since the optical path length changing section is coaxially arranged,
It is also possible to keep the position of the image plane constant regardless of fluctuations.
You.

When the light beam is deflected so that the scanning speed of the light beam is increased, the disk may be rotated at a high speed, and the image is not affected by the inertia of the disk. Can be recorded. Further, since the disk is arranged near the beam waist, the beam diameter of the light beam applied to the disk is reduced, and the size of the disk can be reduced. Therefore, the light beam recording device can be downsized, and the disk can be easily rotated at high speed.

According to a third aspect of the present invention, the detecting means detects the beam waist position of the light beam emitted from the scanning lens, and the moving means moves the disk so that the detected beam waist position becomes a predetermined position. Is preferably moved along a direction intersecting the rotation direction. Thus, even if the position of the image plane changes due to a change in the surrounding environment, this change is detected by the detecting means, and the disk is moved along the direction intersecting the rotation direction by the moving means so that the beam waist position becomes a predetermined position. Is moved, and the optical path length changing unit irradiated with the light beam is changed. Therefore, the position of the image plane can be kept constant regardless of the fluctuation of the surrounding environment , and the image and the like can be recorded with high quality. .

[0032]

EXAMPLES Comparative Example Hereinafter, a comparative example of the present invention will be described first . Figure 4 shows the book
A laser beam recording device 30 according to a comparative example is shown.

The laser beam recording device 30 includes a semiconductor laser 32 for generating a laser beam. On the laser beam emitting side of the semiconductor laser 32, the semiconductor laser 32
And a first converging lens 36 that converges the parallel-beam laser beam.
An optical path length correction disk 38 is arranged near the beam waist position of the laser beam converged by the first converging lens 36.

As shown in FIG. 5A, the optical path length correcting disk 38 is rotatable about a center O as a center of rotation, and a plurality of portions 38A having different refractive indexes are provided along the entire circumference along the rotational direction. , 38B, 38C, 38D are arranged to form an optical path length changing portion. In the present embodiment, as shown in FIG. 5B as an example, when the laser beam is deflected by a polygon mirror 46 described later and the laser beam is imaged by the f · θ lens 52, from one end to the other end in the laser beam scanning direction. The amount of field curvature over the entire surface is measured in advance, and the optical path length changing unit changes the refractive index so that the curved image surface becomes flat, that is, the change in the refractive index when the disk 38 is rotated once by one rotation as shown in FIG. The refractive index of each part and the size of the area are determined so that the distribution (optical path length change pattern) shown in C) is obtained.

In order to form the distribution of the refractive index on the disk 38, various manufacturing methods as shown in Table 1 can be applied.

[0036]

[Table 1]

The optical path length correction disk 38 is rotated by the transmission of the driving force of the motor 40. The drive control circuit 42 is connected to the motor 40. A signal representing a rotation angle of a polygon mirror 46 (described later) as a deflecting unit is input to the drive control circuit 42. The motor 40 and the drive control circuit 42 constitute a drive means of the present invention. The drive control circuit 42 synchronizes the rotation of the disk 38 with the rotation of the polygon mirror 46 based on the input signal, that is, the polygon mirror 46. The motor 40 is driven so that the disk 38 makes one rotation by one scanning of the laser beam by the rotation of.

A second converging lens 44 is disposed on the laser beam emitting side of the optical path length correcting disk 38. The beam diameter of the laser beam emitted from the disk 38 is converged by the second converging lens 44. A polygon mirror 46 is provided on the laser beam emission side of the second converging lens 44.
Are arranged, and the laser beam emitted from the second converging lens 44 is incident on the polygon mirror 46.

On the other hand, near the polygon mirror 46, a synchronization semiconductor laser 48 for generating a laser beam for synchronization is provided.
Is arranged. A collimator 50 is disposed on the laser beam emission side of the synchronization semiconductor laser 48. The laser beam emitted from the synchronization semiconductor laser 48 is converted into a parallel light beam by the collimator 50, and then the polygon mirror 4
6 is incident. The laser beam from the second converging lens 44 and the laser beam from the collimator 50 irradiate substantially the same portion of the polygon mirror 46, and are similarly deflected by the rotation of the polygon mirror 46, and The light is incident on an f · θ lens 52 arranged on the laser beam emission side.

A photosensitive drum 54 is disposed on the optical path of the laser beam emitted from the semiconductor laser 32 and transmitted through the f · θ lens 52 along the scanning direction of the laser beam. The photosensitive drum 54 is structured such that a photosensitive material (not shown) is wound thereon and rotated. The laser beam is deflected by the polygon mirror 46 so as to scan the area shown by the broken line in FIG. 4, and is irradiated on the recording surface of the photosensitive material.

On the other hand, on the optical path of the laser beam emitted from the synchronizing semiconductor laser 48 and transmitted through the f · θ lens 52, the reflecting mirror 5 is arranged along the scanning direction of the laser beam.
6 is disposed, and a linear encoder 58 is disposed on the laser beam emission side of the reflection mirror 56. The laser beam is deflected by the polygon mirror 46 so as to scan a range indicated by a chain line in FIG. The linear encoder 58 is configured such that a large number of transparent band-shaped transparent portions having a constant width are formed at a constant pitch on an opaque plate material.

A photoelectric converter (not shown) is disposed on the laser beam emitting side of the linear encoder 58. When the laser beam scans over the linear encoder 58, the laser beam transmitted through the transparent portion is received by the photoelectric converter. And a pulse signal is output. This pulse signal is input to control means (not shown), and the polygon mirror 46 is controlled so that the pulse interval of the pulse signal is constant. As a result, the laser beam is deflected to scan a plane (recording surface) at a constant scanning speed, and the pixel interval of an image recorded on the photosensitive material is constant.

Next, the operation of this comparative example will be described. When the polygon mirror 46 is rotated, a signal indicating the rotation angle of the polygon mirror 46 is input to the drive control circuit 42, and the drive control circuit 42 rotates the disk 38 in synchronization with the rotation of the polygon mirror 46. Since the polygon mirror 46 of this embodiment scans the laser beam six times in one rotation,
One rotation of the polygon mirror 46 rotates the disk 38 six times. On the other hand, the laser beam emitted from the semiconductor laser 32 enters the disk 38 via the collimator 34 and the first converging lens 36.

Since the disk 38 is rotating as described above, the laser beam irradiating portion on the disk 38 changes with this rotation, and the beam waist position is changed according to the distribution of the refractive index shown in FIG. Are continuously changed. The laser beam emitted from the disk 38 enters the polygon mirror 46 via the second converging lens 44, is deflected by the polygon mirror 46, and is imaged on the recording surface of the photosensitive material by the f · θ lens 52.

As described above, the beam waist position of the laser beam incident on the f · θ lens 52 is changed by the optical path length changing portion of the disk 38, and the curvature of the image plane by the f · θ lens 52 is changed by this change. Since the laser beam is canceled, the laser beam always forms an image on the recording surface of the photosensitive material from one end to the other end in the scanning direction. Therefore, there is no inconvenience such as partial blurring of the image recorded on the photosensitive material, and a high-quality image can be obtained.

The pattern of the optical path length changing section provided on the optical path length correcting disk is not limited to the example shown in FIG. As an example, in the optical path length correction disk 60 shown in FIG. 6A, the disk 60 is divided into six areas by a line connecting each of the dividing points that divide the circumference of the disk 60 into six equal parts and the center O of the disk 60. , Each of the six areas shown in FIG.
An optical path length changing portion is formed so as to have a refractive index distribution as shown in FIG. For this reason, the change in the refractive index when the disc 60 is rotated once is as shown in FIG. 6C, and when the laser beam is scanned once in a portion corresponding to one area of the optical path length changing unit. Is corrected.

When the disk 60 is applied to the laser beam recording device 30, the polygon mirror 46 scans the laser beam six times in one rotation, so that the polygon mirror 46 rotates at the same rotation speed as the polygon mirror 46 in synchronization with the rotation of the polygon mirror 46. What is necessary is just to control. This makes it possible to increase the scanning speed and record an image at a high speed.
The rotation of the disk 60 can easily follow the rotation of the polygon mirror 46 even if the rotation speed is increased.

[ First Embodiment ] Next, a first embodiment of the present invention will be described. Note that the same parts as those of the comparative example are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 8A, the optical path length correcting disk 76 according to the first embodiment is similar to the disk 60 described above in that each of the dividing points for dividing the circumference of the disk 76 into six equal parts is used. It is divided into six areas by a line connecting the center O of 76. The disk 76 has three optical path length changing portions 78A, 78B, 78C coaxially with respect to the center O.
Are formed. Each optical path length changing unit 78A, 78
B and 78C are configured by arranging portions having different refractive indexes so that each of the six areas has a refractive index distribution as shown in FIG. 5C.

Each of the optical path length changing sections 78A, 78B, 7
8C shows the distribution of the change in the refractive index (the shape of the optical path length change pattern).
) Are the same, but the overall refractive index is different.
That is, as shown in FIG. 8C, the refractive index of the optical path length changing section 78A provided on the outermost circumference is generally low, and the optical path length provided adjacent to the inner circumference side of the optical path length changing section 78A. The refractive index of the changing section 78B is generally higher than that of the optical path length changing section 78B, and the refractive index of the optical path length changing section 78C provided at the innermost circumference is further increased.

Therefore, when the laser beam emitted from the first converging lens 36 passes through the outermost optical path length changing portion 78A, the position of the image plane is closest to the f · θ lens 52, and the transmission of the laser beam As the position moves inward, the position of the image plane moves in a direction away from the f · θ lens 52.

On the other hand, in the laser beam recording apparatus 70 of the first embodiment , a position sensor 72 as a detecting means is disposed near the photosensitive drum 54 as shown in FIG. The position sensor 72 includes a filter in which a large number of band-shaped opaque portions having a constant width are formed on a transparent plate at a constant pitch, and a photoelectric converter (not shown) arranged on the laser beam emission side of the filter. The surface is arranged so as to be flush with the recording surface of the photosensitive material wound around the photosensitive drum 54.

The width and pitch of the opaque portion provided in the filter are smaller than those of the linear encoder 58, and are substantially equal to the diameter of the laser beam. When the laser beam scans on the filter of the position sensor 72, the photoelectric converter receives only light transmitted through the transparent portion of the filter,
A DC signal whose level fluctuates sinusoidally is output from the photoelectric converter.

The position sensor 72 is connected to the moving means 74 and outputs the signal to the moving means 74. The moving means 76 moves the disk 76 and the motor 40 along the direction of arrow A in FIG. 7 with respect to the optical axis of the laser beam. As a result, the position of the laser beam passing through the disk 76 is moved along the radial direction of the disk 76, and the optical path length changing portion through which the laser beam passes is changed.

Next, the operation of the first embodiment will be described. The laser beam emitted from the semiconductor laser 32 passes through one of the optical path length changing portions 78A to 78C of the disk 76, is deflected by the polygon mirror 46, and is wound around the light receiving surface of the position sensor 72 and the photosensitive drum 54. The recording surface of the photosensitive material is scanned. By this scanning, the position sensor 7
4 outputs a DC signal whose level varies sinusoidally. The magnitude of the level fluctuation (the difference between the maximum value and the minimum value) of the signal varies depending on the beam diameter of the laser beam applied to the filter on the filter, and when the beam diameter is small, the fluctuation is large. The larger the diameter is, the smaller the energy per unit area is, so the above fluctuation is reduced.

This signal is inputted to the moving means 74, and the moving means 74 moves the disk 76 and the motor 76 by the arrow A so that the level fluctuation of the inputted signal becomes maximum.
Move along the direction. The curvature of the image plane of the laser beam formed by the f · θ lens 52 is corrected by any of the optical path length changing units 78A to 78C as in the comparative example. Changes due to environmental fluctuations. However, if the position of the image plane is shifted from the recording surface of the photosensitive material, it is detected as a decrease in the level fluctuation of the signal output from the position sensor 72. In the moving means 74, the disk 76 and the motor 76 are moved so that the level fluctuation of the signal output from the position sensor 72 is maximized, so that the position of the image plane coincides with the recording surface of the photosensitive material. The corrected image can be recorded with high quality irrespective of changes in the surrounding environment.

[ Second Embodiment ] Next, a second embodiment of the present invention will be described. In addition, the comparative example and
The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 9 , in a laser beam recording apparatus 80 according to the second embodiment , a deflecting beam splitter 82 is disposed on the laser beam emitting side of the collimator 34. As shown in FIG. 10, the laser beam emitted from the collimator 34 is reflected by the mirror surface of the deflecting beam splitter 82, and is emitted through a 波長 wavelength plate 84 attached to the surface of the deflecting beam splitter 82. .

The converging lens 8 is located near the quarter-wave plate 84.
6, optical path length correction disk 6 as shown in FIG.
0 and a reflection mirror 88 are arranged in order. The laser beam emitted from the 波長 wavelength plate 84 is converged by the converging lens 86, passes through the disk 60, and is reflected by the reflecting mirror 88.
And the optical path is changed by 180 °. Reflection mirror 8
The laser beam reflected by 8 passes again through the disk 60, the converging lens 86, and the 波長 wavelength plate 84 and is incident on the deflection beam splitter 82. Deflection beam splitter 82
Is transmitted through the quarter-wave plate 84 twice so that the polarization angle is rotated by 90 °, so that the laser beam passes through the mirror surface and is emitted.

As shown in FIG. 9, a condenser lens 90 and a second lens are provided on the emission side of the laser beam transmitted through the mirror surface.
Are arranged in order. The diameter of the emitted laser beam is adjusted by the condenser lens 90, the laser beam is converged by the second converging lens 90, and is incident on the polygon mirror 46.

The position sensor 72 includes a drive control circuit 9.
4 is connected, and the signal output from the position sensor 72 is input to the drive control circuit 94. Drive control circuit 94
Is connected to the piezo element 92, and the piezo element 92 is controlled so that the level fluctuation of the input signal is maximized.
Voltage. As shown in FIG.
The above-mentioned reflection mirror 88 is attached to the surface of 2.
When a voltage is applied, the piezo element 92 is internally distorted in accordance with the magnitude of the voltage, and is displaced in a direction approaching and separating from the deflection beam splitter 82 (the direction of arrow B in FIG. 10). With this displacement, the reflection mirror 88 also moves along the direction of arrow B in FIG.

When the reflection mirror 88 is located at a predetermined original position, the laser beam reflected by the reflection mirror 88 is emitted from the deflection beam splitter 82 with a beam width indicated by a solid line in FIG. When the reflection mirror 88 is moved to a position approaching the deflection beam splitter 82, the optical path length of the laser beam is shortened, and the laser beam reflected by the reflection mirror 88 is emitted with a beam width indicated by a broken line in FIG. The beam width is slightly increased as compared with the case where the reflection mirror 88 is located at the original position. Therefore, the beam waist position of the laser beam formed by the f · θ lens 52 is moved so as to be separated from the photosensitive drum 54.

When the reflecting mirror 88 is moved to a position separated from the deflection beam splitter 82, the optical path length of the laser beam becomes longer, and the laser beam reflected by the reflecting mirror 88 is shown by a dashed line in FIG. The beam is emitted with the beam width, and the beam width is slightly reduced as compared with the case where the reflection mirror 88 is located at the original position. Therefore,
The beam waist position of the laser beam formed by the f · θ lens 52 is moved so as to approach the photosensitive drum 54.

Next, the operation of the second embodiment will be described. The laser beam emitted from the semiconductor laser 32 and reflected by the reflection mirror 88 and transmitted through the deflection beam splitter 82 is
The position sensor 72 is deflected by the polygon mirror 46.
Are scanned on the light receiving surface and the recording surface of the photosensitive material. The curvature of the image plane of the laser beam formed by the f · θ lens 52 is corrected by the optical path length changing unit provided on the disk 60, but the position of the image plane changes due to a change in the surrounding environment. However, when the position of the image plane is shifted from the recording surface of the photosensitive material, it is detected as a decrease in the level fluctuation of the signal output from the position sensor 72, and the drive control circuit 94 outputs the signal output from the position sensor 72. The voltage applied to the piezo element 92 is changed so that the magnitude of the level fluctuation becomes maximum, and accordingly, the position of the reflection mirror 88 is moved. For this reason, the position of the image plane is corrected so as to coincide with the recording surface of the photosensitive material, and an image can be recorded with high quality irrespective of changes in the surrounding environment.

In the second embodiment , the reflection mirror 88 is attached to the surface of the piezo element 92.
A mirror surface may be formed by depositing a light reflecting material on the substrate.

In the above description, the semiconductor laser 32 is used as the light beam emitting means. However, the present invention is not limited to this, and a gas laser such as He--Ne or a liquid laser may be used.

In the above description, an optical path length correction disk provided with an optical path length changing portion for changing the optical path length by changing the refractive index has been described as an example. However, the present invention is not limited to this. May be provided with an optical path length changing unit that changes the optical path length according to the change of the optical path length.

In the above description, the optical path length changing portion is configured by arranging a plurality of portions having different refractive indexes, and the refractive index changes stepwise by this configuration. However, the present invention is not limited to this. Alternatively, the optical path length changing unit may be configured so that the thickness dimension changes continuously.

[0069]

As described above, according to the first aspect of the present invention, a rotatable disk is provided along a rotation direction.
An optical path length changing portion, in which a portion for changing the optical path length of a transmitted light beam is distributed along the rotation direction, so that a predetermined optical path length changing pattern is generated, the shape of the optical path length changing pattern
Are the same and the degree of change in the optical path length is different
As described above, since a plurality of coaxially arranged , an excellent effect that images and the like can be recorded with high quality and at high speed can be obtained.

According to the second aspect of the present invention, the image plane formed by the deflecting means and the scanning lens is formed to be substantially flat.
The defined optical path length change pattern does not occur along the rotation direction.
As described above, an optical path length changing unit in which a portion that changes the optical path length of a transmitted light beam is distributed along the rotation direction,
The shape of the length change pattern is the same and the degree of change in the optical path length
Fit is de <br/> disk in which a plurality arranged coaxially so different from each other, rotatably arranged near the beam waist that will be formed by the forming means, is driven to rotate in synchronization with the deflection by the deflection means As a result, an excellent effect that images and the like can be recorded with high quality and at high speed can be obtained.

The third aspect of the present invention is directed to the second aspect of the present invention.
Of the light beam emitted from the scanning lens
The beam waist position is detected at the specified position.
Disc along the direction that intersects the direction of rotation so that
Is moved, so in addition to the above effects, the surrounding ring
The position of the image plane can be kept constant regardless of changes in the border
Has the effect that

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for explaining a movement of a focal length by a disk having a changed refractive index as an operation of the present invention.

FIG. 2 is a conceptual diagram for explaining a movement of a focal length by a disk having a changed thickness dimension as an effect of the present invention.

FIG. 3 is a conceptual diagram for explaining a process of obtaining a change amount of an optical path length for correcting a curvature of an image plane.

FIG. 4 is a schematic configuration diagram of a laser beam recording device as a comparative example of the present invention .

FIG. 5A is a plan view of an optical path length correction disk of a comparative example , FIG. 5B is a diagram showing the amount of field curvature by an f · θ lens, and FIG. It is a diagram showing a distribution.

6A is a plan view showing another example of the optical path length correction disk, FIG. 6B is a diagram showing the field curvature by the f · θ lens, and FIG. 6C is a graph showing the refractive index of the disk. FIG. 4 is a diagram illustrating a distribution of changes.

FIG. 7 is a schematic configuration diagram of a laser beam recording apparatus according to a first embodiment of the present invention .

8A is a plan view of an optical path length correcting disk according to the first embodiment, FIG. 8B is a diagram showing the amount of field curvature by an f · θ lens, and FIG. FIG. 4 is a diagram illustrating a distribution of changes.

FIG. 9 is a schematic configuration diagram of a laser beam recording apparatus according to a second embodiment of the present invention .

FIG. 10 is a schematic configuration diagram around a deflection beam splitter in a laser beam recording apparatus according to a second embodiment .

FIG. 11 is an explanatory diagram illustrating a schematic configuration of a conventional laser beam recording apparatus and a curvature of an image plane.

[Explanation of symbols]

 Reference Signs List 10 disk 12 disk 30 laser beam recording device 38 optical path length correction disk 42 drive control circuit 52 f · θ lens 60 optical path length correction disk 70 laser beam recording device 72 position sensor 74 moving means 76 optical path length correction disk 78 optical path length Change unit 80 Laser beam recording device 92 Piezo element 94 Drive control circuit

Claims (3)

(57) [Claims] 1. It is rotatable and predetermined along a rotation direction.
The portion that changes the optical path length of the transmitted light beam is distributed along the rotation direction so that the optical path length changing pattern of
The optical path length changing unit, the shape of the optical path length changing pattern
Are the same and the degree of change in the optical path length is different
For a light beam recording device arranged coaxially as described above . 2. A light beam emitting means for emitting a light beam, a deflecting means for deflecting the light beam emitted from the light beam emitting means, and a scanning lens for imaging the light beam deflected by the deflecting means. Forming means for forming a beam waist of the light beam between the light beam emitting means and the deflecting means; rotatably disposed near the beam waist; forming an image by the deflecting means and the scanning lens; The optical path length change pattern, which is determined so that the image plane
As rolling occurs along the direction, the light is partially changing the optical path length of the transmitted light beam formed by distributed along the rotational direction
The path length changing unit is configured so that the shapes of the optical path length changing patterns are different from each other.
Same so that the degree of change in the optical path length is different from each other.
An optical beam recording apparatus, comprising: a plurality of disks arranged axially ; and a driving unit that rotates the disks in synchronization with deflection by a deflection unit. Detecting means for detecting 3. Before Symbol beam waist position of the light beam emitted from the scanning lens, the detected beam waist position by the detection means and the rotational direction of said disk to a predetermined position 3. The light beam recording apparatus according to claim 2 , further comprising: moving means for moving along the intersecting direction.