JPS60172017A - Laser light generating device - Google Patents

Abstract

PURPOSE:To maintain a physical size interval between a semiconductor laser and a collimating lens in a constant state by surrounding a supporting member by a heat insulating member, also holding the supporting member at a fixed temperature, and cutting off thermally an opening of an optical path by a 1/2 wavelength plate having a heat insulating property, when holding the supporting member by the heat insulating member. CONSTITUTION:A spacer 10 is surrounded by the first heat insulating member 19 and the second heat insulating member 20 of a cylindrical shape, and also a flange 12 is surrounded by the second flange 21 consisting of a heat insulating member such as a synthetic resin, etc. On this second flange 21, an opening is formed in order to secure an optical path of a laser light, and in order to cut off thermally this opening, a 1/2 wavelength plate 22 is utilized. In case when a holo-scanner is used as a scanning means, this 1/2 wavelength plate 22 has a function for rotating a plane of polarization of a laser light by 90 deg. to match a lattice direction of a hologram in order to raise a diffraction efficiency by the hologram. Also, the spacer 10, the flange 12, a semiconductor laser LD, etc. which become an object of a temperature control are surrounded by the heat insulating member, and are scarcely influenced by a temperature variation from the outside, the burden of a Pertier effect element 15 is reduced, and the fixed temperature holding function is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a laser light generation device, and more particularly to a laser light generation device applicable to a laser printer.

(Conventional technology) Semiconductor lasers are known as laser light sources.

Semiconductor lasers are smaller, cheaper, and consume less power than laser light sources such as gas lasers.
It has characteristics such as the ability to linearly modulate the emission intensity with a drive current, and is suitable as a laser light source for an optical scanning device.

Therefore, there is the following example in which an optical scanning device is configured using a semiconductor laser as a light source.

As shown in FIG. 1, the semiconductor laser LD is supported by a mount 1, and is controlled at a constant temperature to an appropriate temperature to ensure performance by a thermistor 2 and a Peltier effect element 3 as a temperature control element. In addition, these members are surrounded by a heat insulating member 4 and thermally isolated. semiconductor laser L
A lens unit 5 containing a collimating lens is supported in front of D.

The collimating lens is provided to convert the diverging light beam from the semiconductor laser into a parallel light beam.In order to increase the coupling efficiency of the coupling lens, the larger the numerical aperture (NA'), the more suitable it is. The larger the number, the shallower the depth of focus, and the higher the lens positioning accuracy is required. Generally, it is said that NA=0.3 is sufficient due to the relationship with the depth of focus.

Now, in the prior art, the semiconductor laser LD is surrounded by a heat insulating member 4 and the temperature is controlled, but the supporting members 6 and 7 that support the lens unit 5 are thermally exposed to the outside air. It is in the same environment as the one that is being heated, but there is no temperature control and it is directly controlled by the environmental temperature.

Therefore, the support members 6 and 7 thermally expand (or thermally contract) due to temperature changes associated with driving this laser beam generator and the optical scanning device using the same, and changes in room temperature, causing the semiconductor laser L D There is a problem in that the distance between the collimating lens and the collimating lens deviates, making it impossible to obtain the required imaging diameter on the photoreceptor or document.

(Objective) Accordingly, an object of the present invention is to provide a laser light generating device equipped with a means for efficiently maintaining a constant physical distance between a semiconductor laser and a collimating lens.

According to the above-mentioned object of the present invention, there is provided a laser light generating device in which support members for a semiconductor laser and a collimating lens are surrounded by a heat insulating member.

(composition) The configuration of the present invention will be explained below based on Examples.

As a solution to the above-mentioned problems in the conventional technology, the supporting members of the semiconductor laser and the becollimating lens are thermally isolated from the outside world, and the inside surrounded by the heat insulating member is also protected from the heat generated by the laser semiconductor itself. In order to eliminate temperature changes in the support member, it is conceivable to maintain a constant temperature by controlling the temperature.

Therefore, when the semiconductor laser and the collimating lens are surrounded by a heat insulating member along with their support members, it becomes necessary to secure at least the optical path of the laser beam with an optically apertured and thermally insulating member. .

On the other hand, recently, an optical scanning method has been put into practical use in which the laser beam emitted from a semiconductor laser is deflected by a hologram grating disk, and the deflected laser beam is focused into a spot on the scanned surface to perform main scanning in a straight line. It's coming.

When using such an optical scanning method, there is a
It has been found that interposing a two-wavelength plate is advantageous in terms of laser light utilization efficiency.

The opening for the optical path formed in a part of the heat insulating member surrounding the collimating lens together with these supporting members is
A laser light generator was constructed by thermally blocking the light with a two-wavelength plate.

21st i! In ilI, the semiconductor laser LD is supported by a spacer 10, and the spacer 1
A flange 12 supporting a lens unit holder 11 is attached to the lens unit 0 in close contact with the lens unit holder 11. A collimating lens Lc is mounted inside the lens unit holder 11.

In the spacer 10, a silicone rubber sheet 1-13 sandwiching a Peltier effect element 15 is in close contact with the surface opposite to the mounting surface of the spacer 10, and a heat dissipation hole is attached to the other silicone rubber sheet 14. j6 are attached closely together.

In the above configuration, the spacer 0 and the flange 12 are made of a material with good thermal conductivity, such as an aluminum alloy. On the spacer lo, the Peltier effect element 15
A thermistor 17 is attached at a position spaced apart from.

A partition wall 18a of a second spacer 18 made of a heat insulating material is interposed between the semiconductor laser LD and the heat radiation fin 16 to thermally isolate the semiconductor laser 1-Dt. This second spacer 18 also covers a portion of the spacer 10.

The silicone rubber sheets 13 and 14 have thermally conductive and electrically insulating properties, and function to bring the Peltier effect element 15 into close contact with the spacer 10 and the radiation fins 16 to improve heat conduction.

Based on the temperature information detected by the thermistor 17,
The spacer 10 and the semiconductor laser LDs are controlled at a constant temperature, and the temperature control effect is further enhanced by the lens unit holder 1.
The temperature of the flange 12 supporting the spacer 1 is also controlled to be the same constant temperature as that of the spacer 0.

That is, the temperature control performance of the Peltier effect element 15 extends to the support member of the collimating lens Lc, so that changes are suppressed.

Here, in order to make the function of the Peltier effect element 15 more effective and to improve the efficiency of drive energy, supporting members such as the spacer 10 and the flange 12 are also surrounded by a heat insulating member.

The means for doing so will be explained below.

The spacer 10 is surrounded by a cylindrical first heat insulating member 9 and a second heat insulating member 20 attached thereto. Further, the flange 12 is surrounded by a second flange 21 made of a heat insulating material such as synthetic resin. This second flange 2
1 is attached as if a kidap was applied to the second heat insulating member 20. By the way, although an opening must be formed in the second flange 21 to ensure the optical path of the laser beam, the 1/2 wavelength plate 22 is used to thermally block this opening.

This 1/2 wavelength plate 22 has a function of rotating the polarization plane of the laser beam by 906 degrees to match the lattice direction of the hologram in order to increase the diffraction efficiency by the hologram when a holo scanner is used as a scanning means, as will be described later. This 1/2 wavelength plate 22 is attached to a holder 23 by adhesive, and is also attached to the second flange 21.

Thus, the spacer 10, which is subject to temperature control. Flange 12. Since the semiconductor laser LD and the like are surrounded by a heat insulating member, they are less affected by external temperature changes, the load on the Peltier effect element 15 is reduced, and the constant @ holding performance is improved.

FIG. 3 specifically shows the configuration shown in FIG. 2.

The structure will be explained below according to the assembly procedure.

In the figure, the lens unit holder 11 includes a washer 24,
Corrugated washer to prevent pack lash 25. It is screwed onto the cylindrical portion 12a of the flange 12 via a washer 26 and the like.

Here, the notch 11a formed in the lens unit holder 11 is for engaging a wrench when performing the above-mentioned screwing, and is used for focus positioning.

The flange 12 mounted with the lens unit holder 11 in this manner is attached to the second flange 21 with screws 27 and 28.

Next, the semiconductor laser LD (is the engagement hole 1 of the spacer 10).
The screws 30 and 31 are used to tighten the screws 30 and 31 in such a way that the screws 30 and 31 are engaged with the step portion 0a, abutted against the stepped seat surface, and pressed from the rear side by the presser plate 29. At that time, the notch 32 of the semiconductor laser LD is the semiconductor laser LT formed on the holding plate 29)
The direction of the contact surface of the semiconductor laser is determined by engaging with a bottle-shaped member protruding from the inside of the engagement hole 29a of No. 4. Furthermore, a spacer 33 is engaged with the cylindrical portion in which the engagement hole 29a is formed, taking heat insulation into consideration.
From its back, a printed circuit board 34 for driving a semiconductor laser is shown.
is installed. Reference numeral 34a indicates a terminal. The thermistor 17 is also screwed onto the spacer 10.

In this way, the spacer 10 to which the semiconductor laser LD+ and the like are attached is attached to the screw holes 12i and 12b of the flange 12 with two attachment screws. One of these screws is numbered 35. Show C. This installation is sometimes 610b.

Adjustments are also made to align the light emitting point of the semiconductor laser LDI with the optical axis of the collimating lens by engaging the tool with the 10 cm distance. Specifically, the spacer 10 is pressed against the flange 12 and the pressing is performed by slightly moving it within the plane.

In this way, once the light emitting points are aligned on the optical axis, the three holes 16e, 16f, 1.6g of the radiation fin 16
It further passes through the hole in the first heat insulating member 19 and the three holes in the second spacer 18, and is tightened into the three screw holes 10e, 10f, and 10g in the spacer 10 with screws. One of the screws mentioned above is designated by the reference numeral 35.

In this way, the four laser beam generators are attached to the main body of the required optical scanning device. This installation is done through two holes 16a and 16 formed in the radiation fin 16.
This is done via b. Incidentally, if one of the screws is designated by the reference numeral 36, this screw 36 passes through the hole 16a, passes through the side notch 19a of the first heat insulating member 19, and passes through the hole 20a in the second heat insulating member 20. Furthermore, the main body of the optical scanning device (not shown) is passed through the bushing 12a1 made of synthetic resin as a heat insulating material fitted into the hole 12aL of the flange 12 and through the hole 21d of the second flange 21. It is screwed into the side plate. A wrench is inserted into the notch 11a of the lens unit 1 to the holder 11 through the opening of the holder 21 and rotated to adjust the emitted light so that it becomes parallel.

Then, the claw 23a of the holder 23 is inserted through the notches 21a and 21b formed in the opening of the second flange 21.
23b, and then rotate the holder 23 to attach the holder 23.

It is assumed that a half-wave plate 22 having heat insulating properties, such as crystal, is bonded to the holder 23 in advance.

Next, the second heat insulating member 20 and the first heat insulating member 19 stacked thereon are pressed against the flange 12, the second spacer 18 is further pressed against the spacer 10, and the opening 18a1 of the second spacer 18 is opened. Seat surface 10a of spacer 10 through
While pressing the silicone rubber sheet 13, the Peltier effect element 15, and the silicone rubber sheet 14 in this order, the three screw holes 10e, 10f, and 10g of the spacer 10 are inserted through the three holes 16e, 16f, and 16g of the radiation fin 16.
Tighten the screws. One screw in the above is designated by the reference numeral 35.

In this way, the integrally configured laser light generating device is attached to a desired optical scanning device main body. This attachment is performed through two holes 16a and 16b formed in the radiation fin 16. Incidentally, if one of the screws is designated by the reference numeral 36, this screw 36 passes through the hole 16a, passes through the side notch 19a of the first heat insulating member 19, and passes through the second heat insulating member 20.
through the hole 20a of the flange 12, and further the hole 12a of the flange 12.
The bushing 12a1 made of synthetic resin as a heat insulating material is fitted into the bushing 12a1, and the hole 21d of the second flange 21 is passed through, and then the bushing 12a1 is screwed into the main body side plate of the optical scanning device (not shown).

In the above description, for the sake of organization, the members made of heat insulating material are enumerated once more: the second flange 21 made of synthetic resin material, and the bush 12a also made of synthetic resin material.
9. First heat insulating member 19 made of polyurethane foam. Second heat insulating member 202 Second spacer 18 made of synthetic resin. These include a 1/2 wavelength plate 22 made of crystal, a holder 23 made of synthetic resin, and the like.

In this example, for example, when a scanning device is configured by combining a collimating lens with a focal length of 9 mm, an fO lens with a focal length of 3011 m, the required optical system, and a scanner, the distance between the collimating lens and the semiconductor laser changes. The relationship between changes in the beam diameter on the surface to be scanned due to this is as shown in Fig. 4, and the change in the feeding direction of the surface to be scanned perpendicular to the scanning direction by the sub-scanning direction scanning means shown by the solid line. Although the amount is almost negligible, in the main scanning direction (scanning direction by the scanning means) shown by the broken line, a change in the luminous flux diameter occurs that cannot be ignored in terms of image formation.

The support member is made of aluminum (linear expansion coefficient: 23.6
10' am/am deg) and the maximum expected temperature change is 35°C, the amount of change in the collimating lens of the semiconductor laser will be 8 μm if no temperature control means are applied, which corresponds to this. The amount of change in the diameter of the light beam on the surface to be scanned exceeds the range that is practical for image formation.

However, when implementing the present invention, temperature control is ±1°C.
This is a relative change in the position of the semiconductor laser of about 0.47 μm, and does not cause any problems in image formation.

Next, the significance of interposing a 1/2 wavelength plate on the optical path between the semiconductor laser and the hologram grating disk will be supplementarily explained.

Simply put, the reason why a 1/2 wavelength plate is used is because of the constraints on the structure of the optical scanning device, the laser beam from the semiconductor laser is incident on the hologram diffraction grating at a 90° grating line. The electric field vibration plane in the luminous flux is 9
This is to maximize the utilization efficiency of laser light in optical scanning by rotating it by 0°.

In this connection, an example of a pretravel device combining a semiconductor laser and a holographic 11-grating disk will be described below.

In FIG. 5, the laser beam Lb from the laser beam generator 149 passes through a cylindrical lens 200, an aperture 300 for beam shaping, and further.

It is reflected by the plane mirror 400.5'OO and is directed toward the hologram grating disk 600 with a predetermined angle of incidence, and is incident on one of the hologram diffraction gratings on the hologram grating disk 600.

The hologram grating disk 600 has a disk shape as shown in FIG. 6, and has a plurality of optically equivalent hologram diffraction gratings 100-1 and 100-2 on one surface of a transparent circular substrate.
...100-i... are arranged in an annular shape.

The hologram diffraction grating 100-i is a linear diffraction grating, and is configured as a surface relief hologram, a volume type phase hologram, or the like.

The hologram grating disk 600 is fixedly attached to the shaft of a motor 700 by a mounting tool (not shown), and is rotated by the motor 700.

In FIG. 6, the direction of the grating lines of the diffraction grating in hologram diffraction grating 100-4 is line A-A, that is, the straight line connecting the center of hologram grating IQO-i and the rotation center of hologram grating disk 600. is parallel to the direction of

When the laser beam Lb enters the hologram diffraction grating IQO-i, diffracted light is generated by the hologram diffraction grating +GO-i. Note that the symbol Lb in the figure indicates a beam cross section of the incident laser beam. hologram grating disk 600
When rotates, the direction of the grating lines of the hologram diffraction grating 100-i with respect to the incident laser beam Lb rotates, so
Accordingly, the direction of the diffracted light changes along a conical surface whose apex is the incident position of the laser light Lb. Since each hologram diffraction grating 100-4 formed on the hologram grating disk 600 is optically equivalent to each other, each time the hologram diffraction grating on which the laser beam Lb is incident is switched by rotating the hologram grating disk 600. , the deflection of the diffracted light is repeated.

Now, the diffracted light generated by the hologram diffraction grating 600 is reflected by a plane mirror 800 placed above the hologram diffraction grating 600, as shown in FIG.
A photoreceptor 130, which is a surface to be scanned, is passed through an fO lens 900, a plane mirror 1000, and a cylindrical lens 120.
Converge in a slit upwards. Then, as the hologram grating disk 600 rotates, the spot-like convergence point is linearly displaced on the surface to be scanned, and main scans the surface to be scanned. Note that reference numeral 160 indicates a photodetector for generating a synchronization detection signal for determining the writing start position.

(Effect) In the present invention, the temperature control effect of the thermistor, the Bertier effect element, the radiation fin, etc. is effectively applied to the supporting member of the semiconductor laser and the collimating lens, so that the temperature of the supporting member is controlled to be constant. The spacing between the laser and the collimating lens is not affected by thermal expansion (convergence), which is advantageous.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a laser beam generator according to the prior art;
FIG. 2 is a cross-sectional view of the laser beam generator according to the present invention, FIG. 3 is an exploded perspective view of the laser beam generator according to the present invention,
FIG. 4 is a graph illustrating the amount of displacement of the beam diameter on the scanned surface due to positional deviation of the semiconductor laser, FIG. 5 is a perspective view illustrating the main parts of the optical scanning device to which the present invention is applied, and FIG.
The figure is a diagram illustrating a laser beam at a diffraction point on a hologram diffraction grating. 10... Spacer, 12... Flange, 12a
...butsch, 15... Peltier effect element, ]6.
...Radiating fin, 17...Thermistor, 1B...
・・Second spacer,】9・・First insulation member, 20・
...Second heat insulating member, 21...Second flange, 22
...172 wavelength plate.

Claims (1)

[Claims] Used in an optical scanning method in which a laser beam is deflected by a hologram grating disk, the deflected laser beam is focused into a spot on a surface to be scanned, and main scanning is performed in a straight line, and as a light source. A laser beam having a semiconductor laser, a collimating lens that converts a diverging light beam from the semiconductor laser into a parallel light beam, and a support member that mechanically holds the semiconductor laser and the collimating lens in a predetermined imaging position. In the generator, the support member is surrounded by a heat insulating member, and a temperature control means for maintaining the support member at a constant temperature is provided, and an aperture for the optical path to be secured when the support member is held by the heat insulating member is provided with a heat insulating member. /
A laser beam generator characterized by thermal isolation using a two-wavelength plate.