JPH04320079A - Laser unit - Google Patents

Abstract

PURPOSE:To accurately maintain formation of a parallel beam of a semiconductor laser light by compensating separation of a collimator lens from the laser due to an expansion of a laser support member upon rising of a temperature, a deviation of a focal position of the lens due to a variation in the oscillation wavelength of the laser by the expansion of the member in a laser unit in which formation of the parallel mean of the light emitted from the laser is conducted by the lens. CONSTITUTION:A lens support member 15 for compensating an expansion of a laser support member 14 and a variation in an oscillation wavelength of a semiconductor laser by reducing an interval between the laser and a collimator lens 8 by the expansion upon rising of a temperature, is provided between the member 14 and the lens 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser unit used in equipment such as a laser printer.

0002

[Prior Art] In devices such as laser printers, the laser light emitted by a semiconductor laser, which is a light source, is collimated into a beam of light by a collimator lens and used for printing, etc. Currently, collimator lenses and semiconductor lasers are used. An integrated laser unit is provided.

[0003] Therefore, as a conventional example of such a laser unit, a device disclosed in Japanese Unexamined Patent Publication No. 1-145611 will be described with reference to FIG. First, in this laser unit 1, a PCB (Princess
A laser holder 6 is fixed to the ted circuit board 3 and the heat sink 4 with bolts 5 passing through these members 3 and 4, and a resin lens barrel is inserted into the cylindrical portion of the laser holder 6 and connected thereto. A collimator lens 8 is fixed to the distal end of the lens 7 . Here, the parts 4 to 6 that form the lens support member are made of aluminum or the like and have a small coefficient of linear expansion, and the resin lens barrel 7 that is the lens support member is made of a resin material added with a filler. It has a large linear expansion coefficient.

In such a configuration, the laser unit 1 is configured to collimate the laser beam emitted by the semiconductor laser 2 with the collimator lens 8 and emit it. Used as a light source, etc.

[0005] Here, since the semiconductor laser 2 that emits high-energy laser light generates heat, the temperature of the semiconductor laser 2 and the various parts 4 to 7 rises as the operating time elapses. At this time, the temperature of the laser holder 6 is usually increased due to temperature rise.
Due to the expansion, the distance between the semiconductor laser 2 and the collimator lens 8 is expanded and the collimation of the laser beam is inhibited. However, in the laser unit 1 disclosed in the above publication, the resin lens barrel The expansion of the parts 4 to 6 is offset by the expansion of the parts 4 to 6, thereby maintaining a uniform distance between the semiconductor laser 2 and the collimator lens 8. In order to realize such characteristics, in the laser unit 1 of the above-mentioned publication, the linear expansion coefficient is controlled by a filler added to the resin lens barrel 7.

[0006]

[Problems to be Solved by the Invention] In the above-mentioned laser unit 1, in order to maintain a uniform distance between the semiconductor laser 2 and the collimator lens 8 and convert the laser beam into a parallel beam with high precision, the laser holder 6 may be damaged due to temperature rise. The linear expansion coefficient of the resin lens barrel 7 is set so as to cancel out the expansions such as the above.

As mentioned above, the collimator lens 8 that collimates the laser beam has a refractive index that changes depending on the wavelength of the transmitted light, and the semiconductor laser 2 that emits the laser beam to the collimator lens 8 has a , the oscillation wavelength of the emitted laser light increases as the main body temperature increases over time. In other words, in the laser unit 1 described above, the distance between the semiconductor laser 2 and the collimator lens 8 is maintained uniform by canceling out the expansion of each part due to temperature rise, but even so, the distance between the semiconductor laser 2 and the collimator lens 8 is maintained uniformly.
The change in the oscillation wavelength of the laser beam impedes parallelization of the laser beam.

For this reason, for example, when a laser printer is manufactured using the laser unit 1 as described above, as the operating time passes, the collimation of the laser beam is inhibited and the printing quality deteriorates.

[0009]

[Means for solving the problem] The invention according to claim 1 includes:
A semiconductor laser that emits laser light is provided, and a collimator lens is provided that has a property of having a high refractive index when the transmitted light has a long wavelength and converts the laser light of the semiconductor laser into a parallel beam. A laser support member that expands is provided, and the laser support member and the collimator lens are connected to each other, and the distance between the semiconductor laser and the collimator lens is reduced by expansion due to temperature rise, thereby expanding the laser support member and changing the oscillation wavelength of the semiconductor laser. A lens support member is provided to compensate for this.

According to the second aspect of the invention, the distance in the optical axis direction from the joint between the lens support member and the laser support member to the light spot of the semiconductor laser is L, and the distance from the joint between the lens support member and the laser support member to the light spot of the semiconductor laser is L. The distance in the optical axis direction to the joint between the lens support member and the collimator lens is l, the temperature of the lens support member and the laser support member that has changed from room temperature is △T, the linear expansion coefficient of the laser support member is Y, and the lens support The linear expansion coefficient of the member is X, the refractive index of the collimator lens at room temperature is n, the refractive index of the collimator lens at temperature ΔT is Δn, the radius of curvature of the light incident surface of the collimator lens is r1, and the light output of the collimator lens is If the radius of curvature of the surface is r2, -{r1・r
2/(r1-r2)} [(△n-n)/{(n-1)・
(△n-1)}]≦L・Y・△T−1・X・△T≦0 is satisfied.

[0011]

[Operation] The lens support member that connects the laser support member and the collimator lens expands due to temperature rise, reducing the distance between the semiconductor laser and the collimator lens, thereby compensating for the expansion of the laser support member and the fluctuation in the oscillation wavelength of the semiconductor laser. Therefore, even after the operating time of the semiconductor laser has elapsed, the collimation of the laser beam can be maintained with high precision.

0012

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 4. Note that the same parts as those in the laser unit 1 described above will be given the same names and symbols, and the explanation will be omitted. First, in the laser unit 9 of this embodiment, as illustrated in FIG.
The heat sink 1 is elastically held on the rear surface of the heat sink 11 by the bolts 12 that pass through these parts 3 and 11.
By fixing the lens barrel 14 within the cylindrical portion of the laser holder 13 fixed to the front surface of the laser holder 1, the parts 11 to 14 made of aluminum or the like form a laser support member having a small coefficient of linear expansion.

A collimator lens 8 is attached to a stepped portion formed on the inner circumferential surface of the lens barrel 14 via an annular lens support member 15 by adhesive or the like. Here, the lens support member 15 is made of acetal resin or the like having a large coefficient of linear expansion, and is made of a joint 16 with the lens barrel 14.
The collimator lens 8 is displaced by expansion and contraction of the operating section in the optical axis direction from the to the joint 17 with the collimator lens 8. Moreover, in this laser unit 9,
An aperture 18 for shaping laser light is attached to the tip of the lens barrel 14.

In this laser unit 9, FIG.
As illustrated in FIG. The length in the optical axis direction from 1 to the joint 17 between the lens support member 15 and the collimator lens 8 is l, the temperature of the parts 11 to 14 forming the laser support member and the lens support member 15 is ΔT, and parts 4 to The linear expansion coefficient of lenses 6 and 10 is Y, the linear expansion coefficient of the lens support member 15 is X, and the collimator lens 8 is
The refractive index at room temperature is n, and the temperature of the collimator lens 8 △T
If the refractive index at is △n, the radius of curvature of the light entrance surface of the collimator lens 8 is r1, and the radius of curvature of the light exit surface of the collimator lens 8 is r2, -{r1・r2/(r1−r2)}
[(△n-n)/{(n-1)・(△n-1)}]≦L
・Y・△T−l・X・The relationship of △T≦0 is satisfied.

In such a configuration, the laser unit 9 is formed such that the light spot of the semiconductor laser 2 is located on the focal position of the collimator lens 8 at room temperature, as illustrated in FIG. 1(a). In this state, similarly to the laser unit 1 described above, the laser light emitted by the semiconductor laser 2 is collimated by the collimator lens 8 and used as a light source of a laser printer.

In this laser unit 9, when the temperature of each part 11 to 15 rises due to the heat generated by the semiconductor laser 2, the parts 11 to 15 expand due to the temperature rise, as illustrated in FIG. 1(b). It is designed to offset the expansion of the semiconductor lasers 11 to 14 and also compensate for fluctuations in the oscillation wavelength of the semiconductor laser 2.

Specifically, as illustrated in FIG. 3, the semiconductor laser 2 has an oscillation wavelength λ of 7 when its temperature ΔT is 0 degrees.
Characteristically, the oscillation wavelength becomes longer as the temperature rises, such as 75 (mm) and 785 (mm) at 50 degrees. The collimator lens 8 is, as illustrated in FIG.
When the wavelength λ of transmitted light is 780 (mm), the refractive index n is 1.7.
2009 and 10 (mm) is 0.000625. Characteristically, as the wavelength of transmitted light increases, the refractive index increases, so when the wavelength λ of transmitted light is 780 (mm) and the focal length f is 6. When a 25 (mm) collimator lens 8 is manufactured, when the wavelength λ changes to 790 (mm), the focal length f changes to 5.46 (mm).

That is, when the temperature rises due to the heat generated by the semiconductor laser 2, each part 11 to 14 expands in the direction of moving the collimator lens 8 away from the semiconductor laser 2, as in the case of the laser unit 1 described above, and the collimator lens 8 also expands. Although the focal length becomes shorter and the focal position moves away from the semiconductor laser 2, in this laser unit 9, the parts 11 to
The linear expansion coefficient of the lens support member 15 and the length of the operating portion are set so as to offset the expansion of the lens 14 and also compensate for the displacement of the focal length of the collimator lens 8. Therefore, in this laser unit 9, the collimation of the laser beam is maintained with high precision even after the operating time has elapsed, so that, for example, a laser printer (not shown) with always good printing quality and stable performance can be used. etc. can be carried out.

Note that when the laser unit 9 is actually manufactured according to the above conditional expression, if the heat generation temperature ΔT is 50 degrees or less, the amount of variation in the focal length of the collimator lens 8 {r1·r
2/(r1-r2)} [(△n-n)/{(n-1)・
(Δn-1)}] is about 10 (μm) at maximum.

[0020]

[Effects of the Invention] The invention as claimed in claim 1 provides a collimator which is provided with a semiconductor laser that emits a laser beam, and which has a characteristic that the longer the wavelength of the transmitted light, the higher the refractive index, and converts the laser beam of the semiconductor laser into a parallel beam. A lens is provided, a laser supporting member is provided to which the semiconductor laser is fixed and expands as the temperature rises, and the laser supporting member and the collimator lens are connected to each other so that the distance between the semiconductor laser and the collimator lens is reduced by the expansion due to the temperature rise. By providing a lens support member that compensates for the expansion of the laser support member and fluctuations in the oscillation wavelength of the semiconductor laser, the semiconductor laser generates heat over time and the laser support member moves the collimator lens away from the semiconductor laser. Even if the oscillation wavelength of the semiconductor laser becomes longer and the focal length of the collimator lens becomes shorter due to the passage of operating time, the expansion of the lens support member offsets the expansion of the laser support member and the focus of the collimator lens Since it also compensates for distance displacement, it has the effect of maintaining the collimation of the laser beam with high precision even after the operating time has elapsed.

According to the second aspect of the invention, the distance in the optical axis direction from the joint between the lens support member and the laser support member to the light spot of the semiconductor laser is L, and the distance from the joint between the lens support member and the laser support member to the light spot of the semiconductor laser is L. The distance in the optical axis direction to the joint between the lens support member and the collimator lens is l, the temperature of the lens support member and the laser support member that has changed from room temperature is △T, the linear expansion coefficient of the laser support member is Y, and the lens support The linear expansion coefficient of the member is X, the refractive index of the collimator lens at room temperature is n, the refractive index of the collimator lens at temperature ΔT is Δn, the radius of curvature of the light incident surface of the collimator lens is r1, and the light output of the collimator lens is If the radius of curvature of the surface is r2, -{r1・r
2/(r1-r2)} [(△n-n)/{(n-1)・
By satisfying the relationship of (△n-1)}]≦L・Y・△T−l・X・△T≦0, the collimation of the laser beam is maintained with high precision even after the operating time has elapsed. This has effects such as being able to easily realize a laser unit that can be used.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of essential parts showing an embodiment of the present invention.

FIG. 2 is a longitudinal side view of the whole.

FIG. 3 is a characteristic diagram of a semiconductor laser.

FIG. 4 is a longitudinal side view of the collimator lens.

FIG. 5 is a vertical side view showing a conventional example.

[Explanation of symbols]

2 Semiconductor laser 8
Collimator lens 9
Laser units 11 to 14 Laser support member 15 Lens support members 16, 17
Joint part 19 Light spot

Claims (2)

[Claims] [Claim 1] A semiconductor laser that emits laser light;
A collimator lens that has a property of having a high refractive index when the wavelength of transmitted light is long and collimates the laser beam of the semiconductor laser, a laser support member to which the semiconductor laser is fixed and expands due to temperature rise, and this laser A lens that connects a support member and the collimator lens and reduces the distance between the semiconductor laser and the collimator lens through expansion due to temperature rise to compensate for expansion of the laser support member and fluctuations in the oscillation wavelength of the semiconductor laser. A laser unit comprising a support member. 2. The distance in the optical axis direction from the joint between the lens support member and the laser support member to the light spot of the semiconductor laser is L, and the distance from the joint between the lens support member and the laser support member to the lens support member and the collimator lens. The distance in the optical axis direction to the junction with the lens support member is l, the temperature changed from room temperature between the lens support member and the laser support member is ΔT, the linear expansion coefficient of the laser support member is Y, and the linear expansion coefficient of the lens support member is X, the refractive index of the collimator lens at room temperature is n, the refractive index of the collimator lens at temperature △T is △n, the radius of curvature of the light entrance surface of the collimator lens is r1, the radius of curvature of the light exit surface of the collimator lens is r2 Then, -{r1・r2/(r1-r2)}[(△n-n)/{
(n-1)・(△n-1)}]≦L・Y・△T−l・X
・Claim 1 characterized in that it satisfies the relationship △T≦0.
Laser unit listed.