JP2861862B2 - Collimating device having a plastic collimating lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collimator having a plastic collimating lens for converting a laser beam from a laser diode into a parallel light beam.

[0002]

2. Description of the Related Art Conventionally, in this type of collimator,
The collimating lens has a problem that the focal length changes due to expansion and contraction based on a temperature change. JP-A-63-1240
No. 10 discloses a collimating device which solves this problem.

FIGS. 5 and 6 are cross-sectional views of the collimator disclosed in the publication. In FIG. 5, a plastic collimating lens (hereinafter, simply referred to as a collimating lens) 43 is formed integrally with an annular projection 44 and is pressed against a metal cylinder 45 by a spring 46. The metal fixed cylinder 41 accommodates the spring 46, the collimating lens 43, and the cylinder 45,
A laser diode (LD) 42 includes a cylinder 45 and a fixed cylinder 41.
Is fixed to the end face of. As the temperature rises, the focal length f of the collimator lens 43 increases by Δf. At this time, the focal point F is going to be displaced to the right in the figure. Therefore, the length M of the annular projection 44 is increased by the temperature increase Δf of the focal length f
In this case, the collimator lens 43 can be displaced in the direction away from the LD 42 (the position indicated by the broken line), and as a result, the displacement of the focal point F can be corrected. Further, the collimating device shown in FIG.
The principle of preventing displacement of the focal length f is the same as that of FIG. In FIG. 6, a plastic collimating lens 53 is formed integrally with an annular projection 54, and the annular projection 54 having a length A is fixed to a metal cylinder 55. LD
52 is fixed to the end face of the cylinder 55.

As described above, conventionally, the displacement of the focal length is corrected by causing the displacement of the distance of the collimating lens with respect to the LD by using the expansion effect due to the temperature rise of the annular protrusions 44 and 45 made of plastic. .

[0005]

However, FIG. 5 and FIG.
In the collimating device of (1), the lengths M and A of the annular projections 44 and 54 must be adjusted in order to correct the temperature change Δf of the focal length of the collimating lenses 43 and 53. This is because the correction amount of the focal length with respect to the temperature change changes depending on the lengths M and A. That is,
This is because when the lengths M and A are long, the correction amount of the focal length can be increased, and when the lengths are short, the correction amount can be reduced. However, in the collimating devices shown in FIGS. 5 and 6, the lengths M and A of the annular projections depend on the focal length of the collimating lens.
Is constrained. Therefore, the lengths M and A cannot be set freely. Therefore, the design of the collimator,
There is no flexibility in manufacturing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a collimating apparatus for preventing displacement of the focal length of a collimating lens by utilizing the expansion action of plastics. It is to provide a device.

[0007]

A collimator according to the present invention comprises a holder having a laser diode fixed on a central axis thereof,
A plastic lens barrel is arranged coaxially with the center axis of the holder, and a plastic collimating lens fixed inside the plastic lens barrel at a predetermined distance in the laser beam emission direction of the laser diode. The plastic lens barrel has a lens barrel rear portion extending in a direction opposite to the laser light emission direction, one end of the lens barrel rear portion and one end of the holder are fixed with an adhesive, and the focal point of the plastic collimating lens based on a temperature change. It is characterized in that the increase and decrease of the distance and the linear expansion of the plastic lens barrel cancel each other.

[0008]

The feature of the present invention is that the rear part of the plastic lens barrel is located rearward of the laser diode (in the direction opposite to the laser beam emission direction), and the length thereof is determined by the focal length of the collimating lens. Without any restrictions. The length of the rear part of the lens barrel determines the degree of correction of the temperature change amount of the focal length. That is, by increasing the length of the rear part of the lens barrel, the correction amount can be increased. However, since the dimensions and the focal length of the plastic lens barrel can be designed separately, there is a degree of freedom in designing and manufacturing.

[0009]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an exploded perspective view showing a collimator according to an embodiment of the present invention, and FIG. 2 is an AA sectional view when the collimator shown in FIG. 1 is assembled. In the figure, a collimator according to the present embodiment includes a metal holder 1, a plastic lens barrel (hereinafter simply referred to as a lens barrel) 2 inserted into and fixed to the holder 1, and fixed inside the lens barrel 2. A collimating lens 3 (hereinafter simply referred to as a collimating lens) and a laser diode (hereinafter referred to as an LD) 4 fixed to the holder 1.

The holder 1 includes a front cylindrical portion 11, a rear cylindrical portion 13, and an LD fixing portion 12 (FIG. 1) formed between these cylindrical portions. LD fixing part 12 has LD4
An LD fixing hole 14 for inserting and fixing the lens is formed on the central axis, and a pair of lens barrel insertion holes 15 are formed around the LD fixing part 12 as shown in FIG. The lens barrel 2 has a cylindrical portion 21 and a pair of projecting portions 22. The collimator lens 3 is fixed inside the cylindrical portion 21, and the fixing position is determined by the stopper 23 (FIG. 2). The protrusion 22
The cylindrical portion 21 is inserted into the lens barrel insertion hole 15 of the LD fixing portion 12 of the holder 1 until the cylindrical portion 21 contacts the LD fixing portion 12. After insertion, the holder 1 is positioned so that the end faces of the holder 1 and the lens barrel 2 coincide.
Of the rear cylindrical portion 13 and the length of the protruding portion 22 of the lens barrel 2
S is determined. The end faces of the holder 1 and the lens barrel 2 are
Fixed by As shown in FIG. 2, the protruding part 22 of the lens barrel 2 is a rear part of the lens barrel in a direction opposite to a direction in which laser light is emitted from the LD 4.

Since the holder 1 is made of metal, the amount of expansion and contraction is sufficiently smaller than the amount of change in the focal length due to the temperature of the collimator lens 3. It is desirable that the plastic material of the collimating lens 3 has a small water absorption and a small linear expansion coefficient. The material of the lens barrel 2 has a large linear expansion coefficient,
Good molded products are good, for example, acrylic is suitable.

Assuming that the temperature change amount of the lens barrel 2 is Δt, the change amount of the focal length of the collimating lens 3 due to the temperature is Δx, and the linear expansion coefficient of the lens barrel 2 is A, as shown in FIG. The distance k from the end face to the collimating lens 3 is as follows.

K = Δx / (A · Δt) (1) From the equation (1), the change amount Δx of the focal length due to the temperature is determined by the temperature change amount Δt of the distance k and the length of the lens barrel 2. The greatest feature of this embodiment is that the protruding portion 22 of the lens barrel 2 is located behind the LD 4 (in the direction opposite to the laser beam emission direction), and the length S is set between the LD 4 and the collimating lens 3. It can be set freely without being aware of the focal length. The length S determines the distance k in the equation (1), and determines the degree of correction of the temperature change amount Δx of the focal length. That is, the correction amount can be increased by increasing the length S. However, even if the length S is changed, the focal length itself does not change, so that the dimensions of the lens barrel 2 and the focal length can be separately designed, and there is a degree of freedom in design and manufacturing. When the linear expansion coefficient A of the lens barrel 2 is large, (1)
There is an advantage that the distance k can be made shorter than the formula, and this advantage is particularly large when acrylic is used as the plastic material of the lens barrel 2.

FIG. 4 is a sectional view showing a second embodiment of the present invention. In the figure, a metal holder 31 to which an LD 34 is fixed is a plastic lens barrel (hereinafter simply referred to as a lens barrel) 3.
2 is fixed inside. The collimator lens 33 is fixed inside the lens barrel 32 at a predetermined distance from the LD 34. The end face of the holder 31 and the end face of the lens barrel 32 coincide with each other, and are fixed with an adhesive 35. At the distance S between the bonding surface of the adhesive 35 and the LD 34, the lens barrel 32 has a lens barrel rear 32 </ b> B.
To form The lens barrel rear portion 32B is a lens barrel portion in a direction opposite to the direction in which the laser light is emitted from the LD.

The effect of the rear portion 32B of the lens barrel is the same as the effect of the projecting portion 22 of the lens barrel 2 in the above-described embodiment. Assuming that the temperature change amount is Δt, the change amount of the focal length of the collimator lens 33 due to the temperature is Δx, and the linear expansion coefficient of the lens barrel 32 is A, the lens barrel 3
The distance k from the end face 2 to the collimating lens 33 is
Equation (1) is obtained. The length S determines the distance k in the expression (1), and determines the degree of correction of the temperature change amount Δx of the focal length of the collimator lens 33. Moreover, since the focal length of the collimating lens 33 is not restricted by changing the length S, there is a degree of freedom in design and manufacturing.

[0017]

As described above, according to the present invention,
The length of the lens barrel that determines the degree of correction of the displacement of the focal length can be freely set without being limited by the focal length of the collimating lens, and the degree of freedom in design and manufacturing is large.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a collimator according to a first embodiment of the present invention.

FIG. 2 is an AA when the collimator of FIG. 1 is assembled.
It is sectional drawing.

FIG. 3 is a right side view of a holder of the collimator of FIG. 1;

FIG. 4 is a sectional view showing a collimator according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a conventional collimator.

FIG. 6 is a cross-sectional view of another conventional collimating device.

[Explanation of symbols]

 Reference Signs List 1 holder 2 lens barrel 3 collimating lens 4 laser diode

Claims (5)

(57) [Claims] 1. A metal holder having a laser diode fixed on a central axis thereof, a plastic lens barrel arranged coaxially with the central axis of the holder, and a laser diode inside the plastic lens barrel. and a fixed plastic collimating lens to a position a predetermined distance in the laser beam emitting direction, the plastic lens barrel, the laser
A rear end of a lens barrel is formed extending from a fixing position of the diode to a side opposite to the laser beam emission direction, and one end of the rear end of the lens barrel and one end of the holder are fixed with an adhesive, and the plastic collimating lens based on a temperature change. A collimating device wherein the increase and decrease of the focal length and the linear expansion of the plastic lens barrel cancel each other. 2. The collimator according to claim 1, wherein the plastic lens barrel is disposed inside the metal holder. 3. A laser diode is fixed on a central axis ,
It has a plane perpendicular to its central axis and
A metal holder having an LD fixing portion to which the laser diode is fixed, a plastic lens barrel arranged inside the metal holder and arranged coaxially with the center axis of the holder, and inside the plastic lens barrel. A plastic collimating lens fixed to a position at a predetermined distance in a laser light emitting direction of the laser diode, wherein the plastic lens barrel is a mirror extending from the LD fixing portion to a side opposite to the laser light emitting direction. A tube rear is formed,
One end of the rear part of the lens barrel and one end of the holder are fixed with an adhesive, and the increase and decrease of the focal length of the plastic collimating lens based on temperature change and the linear expansion of the plastic lens barrel cancel each other, The collimator according to claim 1, wherein the holder further includes a lens barrel insertion hole penetrating the rear part of the lens barrel. 4. The collimator according to claim 1, wherein the plastic lens barrel is disposed outside the metal holder. 5. The collimator according to claim 1, wherein the plastic lens barrel is made of acrylic.