JPH10213778A - Laser optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laser beam of a fine beam shape by removing a side lobe from a laser beam having the side lobe. SOLUTION: A laser beam L having a side lobe is reflectively deflected by a mirror 23 and made incident upon a shaping means 10 and a part of beam quantity of a laser beam L' passed through the means 10 is detected by a photodiode 21 to check whether the beam L is suitably passed through the means 10 or not. When the beam L is not suitably passed through the means 10, a control part 25 controls a piezo element 24 and adjusts the angle of the mirror 23 to adjust the incident angle of the beam L upon the means 10. When the beam L is suitably passed through the means 10, the side lobe of the beam L is cut out by a slit 13 to shape the beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser optical device for shaping a beam shape of a laser beam, and more particularly, to removing a side lobe from a laser beam having a side lobe and shaping the laser beam into a laser beam having a good shape. The present invention relates to a laser optical device.

[0002]

2. Description of the Related Art Conventionally, an optical scanning recording apparatus for deflecting a laser beam by an optical deflector to scan on a photosensitive material and record an image on the photosensitive material, or conversely, from a recording medium on which an image is recorded. Optical scanning readers for reading images are widely used in practice. In such an optical scanning device, various laser generating devices such as a gas laser, a solid laser, a liquid laser, and a semiconductor laser can be used. However, when performing recording or reading of an image, high-quality sharpness is high. In order to obtain an image, a beam with a clean shape, in which the beam shape of the laser beam shows an ideal Gaussian distribution, is required.

In the case of an ideal single transverse mode laser beam, its intensity distribution is a Gaussian distribution, and the beam is gaussian even at a distant point (far-field image) unless the beam undergoes special mode conversion. Shows the distribution. However,
A laser beam emitted from an MOPA (master oscillator / power amplifier) laser or the like often has side lobes and does not completely have an ideal beam shape. Also, as shown in FIG. 2, the laser beam emitted from the semiconductor laser 3 has a large divergence angle, and if the laser beam is collimated by the collimator lens 4 or the like, vignetting occurs. The intensity distribution has side lobes as shown in FIG. In FIG. 2, a hatched portion 5 is a portion where the laser beam is vignetted by the collimator lens 4.

[0004] Such side lobes cause problems such as lowering the sharpness of an image at the time of image recording and reading, and causing artifacts at the time of image recording.

Therefore, an ideal Gaussian distribution (FIG. 4)
Beam shaping for removing side lobes is performed so as to obtain the beam of (b)). As a general method of beam shaping, as shown in FIG.
Beam shaping by an optical system that combines a slit 12 and a slit 13 placed at the focal position is known. This slit 13
By cutting the side lobes using, the beam shape can be made an ideal Gaussian distribution (FIG. 4B).

[0006]

However, when this laser optical system is embodied as an apparatus, the positional relationship between the slit and the beam is changed due to changes in the environmental temperature where the apparatus is placed, deformation of the mechanical members over time, and the like. As a result, there is a problem that a proper beam shaping cannot be performed, and a laser beam having an appropriately shaped beam cannot be stably obtained.

The present invention has been made in view of the above circumstances, and has as its object to provide a laser optical device capable of stably obtaining a laser beam having a good beam shape from which side lobes have been removed. Things.

[0008]

According to a first laser optical device of the present invention, a shaping means for passing a laser beam having side lobes to shape the beam shape of the laser beam; And a control means for controlling the laser beam or the shaping means so as to pass through the shaping means in a predetermined positional relationship from which the side lobes are removed.

That is, the first laser optical device of the present invention adjusts the incident angle at which the laser beam is incident on the shaping means, or controls the position of the shaping means so that the laser beam is moved to a predetermined position. Accordingly, the beam shape is shaped so that a laser beam without side lobes can be stably output by passing through the shaping means.

In a second laser optical device according to the present invention, in the first laser optical device, the shaping means has a lens for focusing the laser beam, and an opening for passing the focused laser beam. Opening means, and the control means performs the control such that a beam waist position of the laser beam substantially coincides with a position of the opening.

As a specific example of the second laser optical apparatus of the present invention, there is an apparatus which shapes a beam shape by a combination of a confocal lens and an aperture arranged at the focal position.

Here, the "opening" means not only a two-dimensional opening such as a pinhole but also a one-dimensional opening such as a slit.
It refers to those that include dimensional openings.

[0013] In a third laser optical device according to the present invention, in the second laser optical device, the control means monitors a laser beam passing through the shaping means and determines a positional relationship of the laser beam with respect to the opening. A monitor means for checking is provided, and the control is performed based on a result of monitoring by the monitor means.

According to a fourth laser optical device of the present invention, in the third laser optical device, the monitor means is a light amount detector for detecting the light amount of the laser beam passing through the shaping means. Is what you do.

According to a fifth laser optical device of the present invention, in the third laser optical device, the monitor means is a position sensor for detecting a position of the laser beam passing through the shaping means. Things.

According to a sixth laser optical device of the present invention, in the third to fifth laser optical devices, the control means deflects the laser beam emitted from the laser light source toward the shaping means. A deflecting means, and an angle adjusting means for adjusting a direction of deflection of the laser beam by the deflecting means, wherein the angle adjusting means is controlled based on the monitoring result. is there.

Here, examples of the "deflecting means" include a mirror and a prism. Examples of the "angle adjusting means" include a piezo element and a pulse motor. A seventh laser optical device according to the present invention, in the third to sixth laser optical devices, controls the control means by adjusting a position of the lens or the opening means based on the monitoring result. The present invention is characterized in that

[0018]

According to the laser optical apparatus of the present invention, the control means controls the laser beam or the shaping means so that the laser beam and the shaping means have a predetermined positional relationship when the laser beam passes through the shaping means. Since the control is performed, the side lobe of the laser beam having the side lobe can always be stably removed. Therefore, even if the positional relationship between the laser beam and the shaping means is displaced due to the temperature change of the environment in which the laser optical device is installed, or the aging of the mechanical members of the device, the laser optical device of the present invention can be used. The apparatus can automatically adjust the positional relationship between the laser beam and the shaping means, and can stably obtain a laser beam having a good beam shape from which side lobes have been removed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the laser optical device according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a laser optical device 1 according to one embodiment of the present invention. The laser optical apparatus 1 includes a shaping unit 10 that receives a laser beam L emitted from a laser light source 2 including a MOPA laser or a semiconductor laser, passes the laser beam L, and shapes the beam shape. A beam splitter 15 that separates a part of the laser beam L 'that has passed through the shaping means 10 and makes the laser beam Lm split by the beam splitter 15 is monitored by the laser beam Lm. The control means 20 checks whether or not the laser beam L has passed through properly, and if it does not pass through properly, the control means 20 controls the incident angle of the laser beam L to the shaping means 10 so as to pass properly. .

The laser light source 1 includes, for example, a single-mode semiconductor laser and a collimator lens for collimating a laser beam oscillated from the semiconductor laser. The beam L is such that a single transverse mode laser beam emitted from a semiconductor laser causes vignetting in the collimator lens and has a side lobe in the light intensity distribution.

Here, the shaping means 10 includes a confocal lens 11,
The laser beam L is focused by the lens 11 and is incident on the slit 13 near the beam waist thereof, and the side lobe of the laser beam L is caused by the slit 13. The beam is cut and shaped so as to have a beam shape whose intensity distribution shows an ideal Gaussian distribution. This shaping means 10
In, if the laser beam L is not properly incident on the slit 13, the beam shape cannot be properly shaped. “Appropriately incident” means that the beam waist of the laser beam L incident on the lens 11 and focused by the lens 11 is at the position of the slit 13 and the laser beam L
Is incident in a positional relationship where the side lobe is appropriately removed by the slit 13.

The control means 20 is a monitor means for monitoring a part Lm of the laser beam L separated by the beam splitter 15, and detects a light quantity of the laser beam Lm by a photodiode (PD) 21; A lens 22 for condensing Lm, a mirror 23 for reflecting the laser beam L emitted from the laser light source 2 and making it incident on the shaping means 10, a piezo element 24 for adjusting the angle of the mirror 23, and detection by the PD 21. It is determined whether or not the laser beam L has properly passed through the shaping means 10 on the basis of the amount of light that has passed through the piezo element so that the laser beam L can properly pass through the shaping means 10 and be shaped. And a control unit 25 that controls the control unit 24. The control unit 25 controls the light amount obtained when the laser beam L emitted from the laser light source 2 has passed through the shaping unit 10 and stored in advance.
By comparing with the light amount of the laser beam Lm detected by the above, it is determined whether or not the laser beam L is properly passing through the shaping means 10, and the piezo element 24 is so determined as to obtain the stored light amount. To adjust the angle of the mirror 23. The angle of the mirror 23 changes the direction of the laser beam L in a plane parallel to the plane of the paper and / or changes the direction of the laser beam L in a direction perpendicular to the plane of the paper.
Is adjusted so as to change the direction. In addition,
The control unit 25 may be configured to control the piezo element 24 to adjust the angle of the mirror 23 so that the light amount of the laser beam Lm detected by the PD 21 is maximized.

The operation of the laser optical device 1 will be described below.

The laser beam L having side lobes emitted from the laser light source 1 is reflected by the mirror 23 and deflected toward the shaping means 10. The laser beam L 'that has passed through the shaping means 10 is split by the beam splitter 15 and a part Lm of the beam is incident on the PD 21. PD21
The light quantity of the laser beam Lm is detected at
Means for appropriately shaping the laser beam L from the detected light quantity
If it is determined that the light does not pass through the piezo element 24,
To adjust the angle of the mirror 23. When the angle of the mirror 23 is adjusted and the laser beam L is incident on the shaping means 10 with a predetermined positional relationship with respect to the shaping means 10, the side lobe of the laser beam L is cut by the slit 13 and a beam having a Gaussian distribution is obtained. Shaped into shape. The laser beam L ′ whose beam shape has been shaped is collimated by the lens 12 and output from the laser optical device 1. The laser beam L ′ whose beam shape has been shaped is applied to the imaging lens 30.
Etc., and combined with a polygon mirror, fθ lens, etc., a printer, CR (Computed Radiograp
hy), etc., and used for image recording or image reading. By performing optical scanning using a laser beam shaped into an ideal beam shape by the laser optical device of the present invention, it is possible to obtain an image with good sharpness and high quality.

In the laser light source device 1, the mirror 23
Alternatively, a prism may be used as a deflecting means, and the laser beam L may be refracted by the prism and deflected toward the shaping means 10. The angle of the deflecting means is adjusted using a pulse motor instead of the piezo element. It may be a thing.

Further, the monitoring means is not limited to the mode using the photodiode 21 for detecting the light amount of the laser beam as described above, but the position of the laser beam Lm is detected by the position sensor and the detected laser beam is detected. It is also possible to take a form of examining the positional deviation of the laser beam L from the slit from the position of Lm.

The control unit 25 adjusts the angle of the deflecting means such as a mirror using a piezo element or a pulse motor, instead of the lenses 11, 12 or the slit of the shaping means 10.
The positional relationship between the laser beam L and the control means 10 may be adjusted by moving 13 or both in a plane perpendicular to the paper surface. Further, in some cases, the beam waist position may be adjusted by moving the lenses 11, 12 and the slit 13 in the optical axis direction.

When the apparatus is used by being incorporated in an apparatus such as a printer or a CR, the position control may be performed every time reading / recording is performed, but the control may be performed only when the power of the apparatus is turned on.

In the above embodiment, the laser beam output from the laser light source has side lobes. However, the laser optical device of the present invention has a side lobe caused by vignetting by another optical system. It is also possible to shape the beam shape of the laser beam having the above.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a laser optical device of the present invention.

FIG. 2 is a diagram showing a laser light source in which vignetting occurs.

FIG. 3 is a diagram showing an optical system for shaping a laser beam having side lobes;

FIG. 4 is a diagram showing an intensity distribution of a laser beam;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser optical device 2 Laser light source 10 Shaping means 11, 12 lens 13 Slit 15 Beam splitter 20 Control means 21 Photodiode 22 Lens 23 Mirror 24 Piezo element 25 Control part 30 Imaging lens

Claims (7)

[Claims] 1. A beam shaping unit for removing a side lobe of a laser beam by passing a laser beam having a side lobe, and a predetermined positional relationship between the laser beam and the shaping unit for removing the side lobe. And a control means for controlling the laser beam or the shaping means so as to pass through the shaping means. 2. The method according to claim 1, wherein the shaping unit includes a lens that focuses the laser beam, and an opening unit that has an opening that allows the focused laser beam to pass therethrough. The laser optical device according to claim 1, wherein the control is performed such that a beam waist position of the beam substantially coincides with a position of the opening. 3. The control means includes monitor means for monitoring a laser beam passing through the shaping means and examining a positional relationship of the laser beam with respect to the aperture, and performing the control based on a monitoring result by the monitor means. 3. The laser optical device according to claim 2, wherein the laser optical device performs the operation. 4. The laser optical device according to claim 3, wherein said monitor means is a light quantity detector for detecting a light quantity of the laser beam passing through said shaping means. 5. The laser optical device according to claim 3, wherein said monitor means is a position sensor for detecting a position of a laser beam passing through said shaping means. 6. A deflecting means for deflecting the laser beam emitted from the laser light source toward the shaping means, and an angle adjusting means for adjusting a deflecting direction of the laser beam by the deflecting means. The laser optical device according to any one of claims 3 to 5, further comprising: controlling the angle adjusting unit based on the monitoring result. 7. The laser according to claim 3, wherein said control means performs said control by adjusting a position of said lens or said aperture means based on said monitoring result. Optical device.