JP2000218859A - Laser recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser recorder capable of improving a use efficiency of a laser beam and accurately recording an image in a simple structure insusceptible of the change with the passage of time. SOLUTION: A near field pattern of a laser beam L outputted from a semiconductor laser device LD is to be a parallel flux by a collimator lens 26, then the pattern is imaged on an aperture member 20 by a first lens 18. After the imaged near field pattern is beam-shaped in a sub-scanning direction by the aperture member 20, it is introduced to a recording film F through a second lens 22 and a third lens 24, thereby recording an image. At that time, fluctuation of the laser beam L in the sub-scanning direction is suppressed by the aperture member 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser recording apparatus for recording an image or the like by two-dimensionally scanning a recording medium with a laser beam.

[0002]

2. Description of the Related Art In the field of image recording, a laser recording apparatus for controlling the drive of a laser optical system based on a digital signal subjected to image processing and exposing and recording an image by area modulation on a recording medium is used. The recording medium on which the image has been exposed and recorded is supplied to a developing machine as necessary, and is converted from a latent image to a visible image.

In such a laser recording apparatus, a plurality of semiconductor lasers are arranged on a curved surface, a laser beam output from each semiconductor laser is collimated, and then condensed on a photosensitive material using a condenser lens. There is one configured to record an image (prior art 1: U.S. Pat. No. 4,744)
3,091).

In a laser recording apparatus having another configuration, after collimating laser beams output from a plurality of semiconductor lasers, an aperture member is disposed in the optical path of a laser beam composed of parallel light beams, and the aperture member is provided. There is a configuration in which an aperture image of a laser beam due to the aperture is formed on a photosensitive material (prior art 2: Japanese Patent Laid-Open No.
-186490).

[0005]

In this case, the prior art 1
Can focus laser beams from a large number of semiconductor lasers on a photosensitive material using a condensing lens, but since the setting position of each semiconductor laser sensitively affects the recording position on the photosensitive material, high precision In order to record various images,
It is necessary to position the semiconductor laser with high accuracy. However, even though the semiconductor laser is positioned with high accuracy, there is a problem that the recording accuracy is reduced due to the influence of the temporal change.

On the other hand, in the prior art 2, since the aperture member is disposed in the optical path of the collimated laser beam, if the aperture is set small, the semiconductor laser can be misaligned, and the semiconductor laser can be stabilized. High-precision images and the like can be recorded. However, in this configuration, since the light amount of the laser beam is greatly attenuated by the aperture member, there is a problem that the utilization efficiency of the laser beam is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and can improve the efficiency of use of a laser beam, and can highly accurately convert an image or the like with a simple structure without being affected by temporal fluctuation. It is an object of the present invention to provide a laser recording device capable of recording on a laser beam.

[0008]

In a laser recording apparatus according to the present invention, a near-field pattern is imaged by condensing a laser beam having a wide intensity distribution in a sub-scanning direction by an imaging lens. An image or the like is formed by shaping the near-field pattern in the sub-scanning direction using an aperture member arranged at the image forming position and guiding the near-field pattern to a recording medium.

In this case, since the laser beam is wide in the sub-scanning direction, the influence of the position shift of the near field pattern in the sub-scanning direction on the position shift of the laser light source is extremely small, and therefore, the influence of the fluctuation is small. In addition, it is possible to efficiently guide a laser beam to a recording medium and record a highly accurate image or the like. The displacement of the laser beam in the main scanning direction can be easily corrected by electrically controlling the recording timing.

[0010]

1 and 2 show a laser recording apparatus 10 according to the present embodiment. This laser recording device 10
Is a device for recording an area-modulated image by irradiating a plurality of laser beams L emitted from the exposure head 12 to a recording film F (recording medium) mounted on a drum 14. Note that a two-dimensional image is formed on the recording film F by moving the exposure head 12 in the sub-scanning direction (arrow Y direction) with respect to the drum 14 rotating in the main scanning direction (arrow X direction). The area-modulated image is an image in which a plurality of pixels are formed on the recording film F by controlling on / off of the laser beam L, and a predetermined gradation can be obtained depending on an area occupied by the pixels.

The exposure head 12 includes a light emitting unit 16 for outputting a plurality of laser beams L shown in FIG. 3, and a first lens 18 for condensing each laser beam L output from the light emitting unit 16 on a focal plane. An aperture member 20 disposed on the focal plane of the first lens 18; and a second lens 22 and a third lens 24 for condensing each laser beam L on the recording film F.

The light-emitting unit 16 includes a plurality of light-emitting portions 28 each including a semiconductor laser LD and a collimator lens 26, and a mount 32 having a light guide path 30 and on which each light-emitting portion 28 is mounted. Note that the semiconductor laser LD is arranged at the focal position of the collimator lens 26.

Here, the semiconductor laser LD is composed of a refractive index guided semiconductor laser which is a lateral multi-mode semiconductor laser, and basically has a p-type semiconductor substrate 33 and an n-type semiconductor laser as shown in FIG. An active layer 38 is provided between the semiconductor substrate 35 and the electrodes 40 and 42 provided on the semiconductor substrates 33 and 35.
The laser beam L is output from the active layer 38 by applying a predetermined voltage therebetween. In this case, the width of one electrode 40 is regulated, and the refractive index in the direction along the active layer 38 is controlled in accordance with the width. Therefore, the near-field pattern of the laser beam L output from the semiconductor laser LD is wide and substantially rectangular in the direction of the bonding surface of the active layer 38 corresponding to the width of the electrode 40, as shown in FIG. In the thickness direction of the active layer 38, the width becomes a shape corresponding to the thickness.

The semiconductor laser LD thus configured
Are mounted on a spherical mount 32, and the laser beam L output from each semiconductor laser LD is
Intersect at the front focal position of the first lens 18 as shown in FIG.

As shown in FIG. 5, the aperture member 20 arranged on the focal plane of the first lens 18 has a plurality of openings 34 corresponding to the respective semiconductor lasers LD. The opening 34 is configured to be narrow in the sub-scanning direction (arrow Y direction) and wide in the main scanning direction (arrow X direction). In this case, the beam spot 36 of the laser beam L output from each semiconductor laser LD is
The width in the sub-scanning direction (the direction of the arrow Y) is regulated.
In the present embodiment, the openings 34 are arranged in the main scanning direction (arrow X direction) so as to be shifted by a predetermined distance Δ in the sub-scanning direction (arrow Y direction). At the same time, 49 beam spots 36 are recorded on the recording film F.

The laser recording apparatus 10 according to the present embodiment
Basically, it is configured as above,
The operation and effect will be described.

The laser beam L modulated according to the image information and output from the active layer 38 of each semiconductor laser LD is:
After being converted into a parallel light beam by the collimator lens 26 and passing through the front focal point of the first lens 18, it is condensed on the rear focal plane of the first lens 18. In this case, the semiconductor laser LD
Is located at the front focal position of the collimator lens 26, so that a near-field pattern of the laser beam L (see FIG. 4) is formed on the rear focal plane of the first lens 18.

Here, the near field pattern of the laser beam L has a narrow intensity distribution in the main scanning direction (arrow X direction) of the recording film F and a wide intensity distribution in the sub scanning direction (arrow Y direction). On the other hand, the rear focal plane of the first lens 18 has a sufficient width in the main scanning direction (arrow X direction),
An aperture member 20 having a plurality of openings 34 having a width set to be smaller than the width of the beam spot 36 of the laser beam L in the sub-scanning direction (the direction of the arrow Y) is arranged (see FIG. 5). ). The plurality of openings 34 are arranged corresponding to each laser beam L output from the semiconductor laser LD.

Accordingly, since the position of each laser beam L passing through the aperture member 20 in the sub-scanning direction (the direction of the arrow Y) is regulated by the aperture member 20, the position of the semiconductor laser LD is affected. Instead, the light is condensed with high precision at a predetermined position in the sub-scanning direction (the direction of the arrow Y) on the recording film F via the second lens 22 and the third lens 24. The position in the main scanning direction (the direction of the arrow X) can be easily dealt with by electrically adjusting the timing of the main scanning.

In this embodiment, the shape of the laser beam L is set to be narrow in the main scanning direction (arrow X direction) and wide in the sub-scanning direction (arrow Y direction).
The laser beam L can be efficiently guided to the recording film F regardless of the displacement of the semiconductor laser LD.

That is, the width of the laser beam L output from the semiconductor laser LD in the main scanning direction (the direction of the arrow X) is represented by W
⊥, the width in the sub-scanning direction (arrow Y direction) is W //, the width of the beam spot 36 on the surface of the aperture member 20 in the main scanning direction (arrow X direction) is d0⊥, and the sub-scanning direction (arrow Y direction) 6) is d0 //, the deviation of the relative position between the light emitting point of the semiconductor laser LD and the optical axis of the collimator lens 26 is δs, and the deviation of the deviation δs on the surface of the aperture member 20 is δs0. As shown in the schematic diagram of FIG. 7, δs0 / d0⊥ = δs / W⊥ (1) δs0 / d0 // = δs / W // (2) In this case, since W⊥≪W //, the position variation of the beam spot 36 on the surface of the aperture member 20 is
It is understood that the position fluctuation in the sub-scanning direction (arrow Y direction) is much smaller than that in the main scanning direction (arrow X direction).

As a result, the width of the opening portion 34 formed in the aperture member 20 in the sub-scanning direction (arrow Y direction) is set to be wider by approaching the width d0 // of the beam spot 36 in the sub-scanning direction (arrow Y direction). can do. Therefore, the laser beam L is not largely shaken by the aperture member 20, and can be efficiently guided to the recording film F.

When recording an image using a near-field pattern of a lateral multi-mode semiconductor laser, it is necessary to consider the influence of the far-field pattern. Therefore, this point will be discussed below.

As described above, the near-field pattern of the laser beam L is imaged on the rear focal plane of the first lens 18, while the far-field pattern is formed by the collimator lens 26 as shown in FIG. Since the image is formed at the rear focal position P0, the image of the far field pattern is condensed by the first lens 18 as shown by the dotted line in FIG. An image is formed on P0 '.

In this case, as shown in FIG. 8, the full width at half maximum angle of the laser beam L output from the semiconductor laser LD in the sub-scanning direction (the direction of arrow Y) is θ //, and the focal length of the collimator lens 26 is Assuming f1, the full width at half maximum Sff at the rear focal position P0 in the sub-scanning direction (the direction of the arrow Y) of the far field pattern is Sffｆ2 · f1 · sin (θ /// 2) (3). Assuming that the optical distance from the rear focal point position P0 to the front principal point position of the first lens 18 is L0 and the focal length of the first lens 18 is f2, the image of the far field pattern of the laser beam L is F from rear principal point
An image is formed at a position P0 'separated by 2.L0 / (L0-f2) toward the recording film F. The width d0 / of the image of the far field pattern in the sub-scanning direction (the direction of arrow Y)
/ 'Is as follows: d0 //' = Sff · f2 / (L0−f2) = 2 · f1 · f2 · sin (θ // 2) / (L0−f2) (4) On the other hand, the width d0 // of the image of the near-field pattern in the sub-scanning direction (the direction of arrow Y) is as follows: d0 // = W // · f2 / f1 (5)

Here, as shown in FIG. 9, d0 //> d0
In the case of // ′, since the near-field pattern is imaged on the recording film F, there is a concern that the diameter of the beam spot 36 of the laser beam L fluctuates greatly due to the position fluctuation of the recording film F in the depth of focus direction. There is.
On the other hand, as shown in FIG. 10, when d0 // ′ ≧ d0 //, the diameter of the beam spot 36 does not change significantly even when the position of the recording film F fluctuates in the depth of focus direction. Images and the like can be recorded in the state.
Therefore, assuming that the width of the opening 34 of the aperture member 20 set at the position where the near-field pattern is condensed is D //, the intensity distribution of the laser beam L is set to be wide in the sub-scanning direction (the arrow Y direction). In addition, by designing the optical system constituting the laser recording device 10 so as to satisfy the relationship of d0 // '≧ d0 /> D //, the sub-scanning direction (arrow Y
Direction) and the depth of focus direction.

Also, in the case of d0 //> d0 // ', FIG.
As shown in FIG. 1, the width D // of the opening 34 of the aperture member 20 is set so as to satisfy the relationship d0 //> d0 // '≧ D //.
Is set, the influence of the position fluctuation in the sub-scanning direction (arrow Y direction) and the depth of focus direction can be reduced.

In the laser recording apparatus 10 configured as described above, when a part of the laser beam L is reflected by the aperture member 20 and re-input to the semiconductor laser LD, there is a concern that mode hopping will occur. Is done. Therefore, as shown in FIG.
When the first lens 18 disposed in the preceding stage is set to be shifted by a predetermined amount in a plane perpendicular to the optical axis, the laser beam L reflected by the aperture member 20 is applied to the semiconductor laser LD as shown by a dotted line. It is possible to avoid a situation where re-input is performed. For example, assuming that the shift amount with respect to the optical axis is δα, the laser beam L reflected by the aperture member 20 shifts by 2 · δα. Therefore, when the beam diameter of the laser beam L passing through the collimator lens 26 is B, it is set so that B <2 · δα.
By providing a light-shielding plate for this reflected light as needed, mode hopping of the semiconductor laser LD can be suitably avoided.

[0029]

As described above, according to the laser recording apparatus of the present invention, the intensity distribution of the laser beam is set to be wide in the sub-scanning direction, and on the aperture member for regulating the width in the sub-scanning direction. By imaging the near-field pattern of the laser beam, it is possible to suppress the variation of the laser beam in the sub-scanning direction and efficiently guide the laser beam to the recording medium. Therefore, an image or the like can be recorded with high accuracy with a simple configuration regardless of the influence of a temporal change.

[Brief description of the drawings]

FIG. 1 is a perspective configuration diagram of a laser recording apparatus using a near-field pattern according to an embodiment.

FIG. 2 is a plan view of the laser recording apparatus shown in FIG. 1;

FIG. 3 is an enlarged explanatory view of a light emitting unit and a first lens in the laser recording device shown in FIG.

FIG. 4 is an explanatory diagram of a structure of a semiconductor laser constituting a light emitting unit and a near-field pattern of a laser beam output from the semiconductor laser.

5 is an explanatory front view of an aperture member included in the laser recording device shown in FIG. 1;

FIG. 6 is an explanatory diagram of an influence of a fluctuation in a main scanning direction of a laser beam output from a semiconductor laser included in a light emitting unit.

FIG. 7 is an explanatory diagram of an influence of a fluctuation in a sub-scanning direction of a laser beam output from a semiconductor laser included in a light emitting unit.

FIG. 8 is an explanatory diagram of a far field pattern of a laser beam output from a semiconductor laser.

FIG. 9 is an explanatory diagram of a beam diameter at an imaging position of a near-field pattern and a far-field pattern.

FIG. 10 is an explanatory diagram of a beam diameter at an imaging position of a near-field pattern and a far-field pattern.

11 is an explanatory diagram of a case where an aperture member is arranged at an image forming position of a near-field pattern in the state of FIG. 9;

FIG. 12 is an explanatory diagram of a state where the first lens is set to be shifted by a predetermined distance in a plane orthogonal to the optical axis in the laser recording apparatus shown in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Laser recording device 12 ... Exposure head 14 ... Drum 16 ... Light emitting unit 18 ... 1st lens 20 ... Aperture member 22 ... 2nd lens 24 ... 3rd lens 26 ... Collimator lens 28 ... Light emitting part 36 ... Beam spot F ... Recording Film LD: Semiconductor laser

Continued on front page F-term (reference) 2C362 AA03 AA13 AA14 AA29 AA40 AA42 AA47 BA28 BA86 2H045 AG09 BA22 BA32 BA41 CB22 CB24 CB31 CB42 5F073 AA04 AA12 AB27 EA18 FA30

Claims (9)

[Claims] 1. A laser recording apparatus for recording an image or the like by two-dimensionally scanning a recording medium with a laser beam, wherein the intensity distribution is narrow in a main scanning direction and wide in a sub-scanning direction of the recording medium. A laser light source that outputs a laser beam indicating the following: an imaging lens that forms an image of the near-field pattern of the laser beam between the laser light source and the recording medium; An aperture member having a width in the scanning direction set to be smaller by a predetermined amount than the width of the near field pattern in the sub-scanning direction. 2. A laser recording apparatus according to claim 1, wherein said laser light source is a lateral multimode semiconductor laser. 3. A laser recording apparatus according to claim 1, wherein said laser light source is a refractive index guided semiconductor laser. 4. A laser recording apparatus according to claim 1, wherein a direction parallel to an active layer bonding surface of said laser light source is set as said sub-scanning direction. 5. A laser recording apparatus according to claim 1, wherein said laser light source comprises a plurality of semiconductor lasers arranged two-dimensionally. 6. An apparatus according to claim 5, wherein said plurality of semiconductor lasers are arranged on a spherical surface so that said laser beams cross each other on a front focal plane of said imaging lens and are guided to said imaging lens. A laser recording device, which is provided. 7. The laser according to claim 6, wherein the intersection of the laser beams is set at a point on the front focal plane that is separated from the optical axis of the imaging lens by a predetermined distance. Recording device. 8. The apparatus according to claim 1, wherein the width of the intensity distribution in the sub-scanning direction of the near-field pattern formed by the imaging lens is formed by the imaging lens. The laser recording apparatus is set to be smaller than the width of the intensity distribution of the laser beam in the sub-scanning direction of the far field pattern. 9. An apparatus according to claim 1, wherein said near-field pattern formed by said imaging lens has a width d0 // of an intensity distribution in a sub-scanning direction and said imaging lens has a width d0 //. The width d0 // 'of the intensity distribution in the sub-scanning direction of the far-field pattern of the laser beam to be imaged, and the width in the sub-scanning direction of the aperture of the aperture member arranged at the imaging position of the near-field pattern D // is set so that d0 //> d0 // '≧ D //.