JPH0228122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical system using a semiconductor laser as a light source, and more particularly to a light source device suitable for an optical system that requires highly accurate parallel light and is used in a wide operating temperature range.

Conventional light source devices ignore changes in the distance between the semiconductor laser's light emitting point and the coupling lens due to thermal expansion caused by temperature changes, making it difficult to output highly accurate parallel light in devices that have a wide operating temperature range. It was possible.

An object of the present invention is to provide a light source device that outputs highly accurate parallel light that is not affected by temperature changes.

The semiconductor laser light source device will be explained using FIG. 1. If the light emitting point of the semiconductor laser is located at the focal point of the coupling lens, the output light from the coupling lens becomes parallel light. If the light emitting point of the semiconductor laser deviates from the focal position of the coupling lens, the output light from the coupling lens will no longer be parallel light. FIG. 2a shows a schematic diagram of the semiconductor laser light source device. The semiconductor laser mount 1 and the coupling lens 2 are connected by a fixed frame 4. When a temperature change occurs, the distance between the light emitting point 8 of the semiconductor laser and the lower end 9 of the coupling lens changes due to thermal expansion of the fixed frame 4. This distance change occurs when the fixed frame 4 has a structure in which the semiconductor laser mount 1 and the coupling lens 2 are directly connected. In the present invention, as shown in FIG. 2b, a thermal expansion absorbing damper 5 having a different thermal expansion coefficient from that of the fixed frame 4 is installed between the fixed frame 4 and the semiconductor laser mount 5, and between the fixed frame 4 and the coupling lens 2. A method has been devised to cancel changes in the distance between the lower end 9 of the coupling lens and the semiconductor laser light emitting point 8 due to temperature changes. However, the thermal expansion absorbing damper 5 can be used with either one. The coupling lens 2 has a lens fixed in a cylindrical lens housing, and has the role of converting laser light into parallel light.

In FIG. 2b, when the fixed frame 4 thermally expands and the distance between the lens 2 and the part supporting the laser mount 1 increases, the damper 5 is made to have a larger coefficient of thermal expansion than the fixed frame 4, and the fixed frame 4 When the lens 2 or the laser mount 1 is fixed to a part of the damper fixed to the lens 2 or the laser light source 8,
Since the expansion of the damper 5 acts to cancel out the expansion due to the expansion of the fixed frame 4, the size of the damper 5,
By appropriately setting the coefficient of thermal expansion, the distance between the lens and the light source can be kept constant.

An embodiment of the present invention will be described below with reference to FIG. FIG. 3 is a diagram of a light source device using a semiconductor laser as a light source. The light source device includes a semiconductor laser mount 1 for fixing a semiconductor laser, a heat sink 3 for dissipating heat generated by the semiconductor laser, and a coupling lens 2 for converting laser light into parallel light.
, a fixing frame 4 for connecting and fixing the semiconductor laser mount 1 and the coupling lens 2, and a fixing frame 4 for coupling the coupling lens 2 and the fixing frame to absorb changes in the distance between the coupling lens 2 and the semiconductor laser light emitting point due to thermal expansion. 4, and a fine adjustment screw 6 for adjusting the position of the coupling lens 2. FIG. 4 is a sectional view of the light source device. In Fig. 4, the fixed frame 4
Let Ka be the coefficient of thermal expansion of . Thermal expansion absorption damper 5
The coefficient of thermal expansion of is Kb, and the coupling lens and fixed frame are connected. When the coefficient of thermal expansion of the semiconductor laser mount 1 is Kc, the fixed frame 5 at a temperature change T
The thermal expansion of is (l ₁ + l ₂ + l ₃ ) × T × Ka, and the thermal expansion of the semiconductor laser 1 of ab is l ₁ × T × Kc The thermal expansion of the thermal expansion absorbing damper 5 of cd is l ₃ × T×Kb At this time, it is sufficient that bc is constant, so (l ₁ +l ₂ +l ₃ )×T×Ka−l ₁ ×T×Kc −l ₃ ×T×Kb=0, and l ₃ =l ₁ If the shape satisfies ×(Ka−Kc)+l ₂ ×Ka/Kb−Ka, a light source device that outputs parallel light that is not affected by temperature changes can be obtained. When aluminum is used for the fixing frame, Ka=23×10 ^-6 When copper is used for semiconductor laser mount 1, Kc=16.7×
10 ^-6 , when polymethyl methacrylate is used for the thermal expansion absorbing damper, Kb = 80 x 10 ^-6 , and in this case, if l ₁ = 3 mm and l ₂ = 1 mm, then l ₃ = 0.74 mm.

Also, if stainless steel is used for the fixed frame,
When Ka=16.4×10 ^-6 , copper is used for the semiconductor laser mount 1, and aluminum is used for the thermal expansion absorbing damper, l ₁ =3 mm and l ₂ =1 mm, then l ₃ =2.4 mm.

An embodiment in which a semiconductor laser is cooled will be described with reference to FIG. The semiconductor laser mount 1 is cooled by the Peltier element 7. At this time, Perchile element 7
Since the semiconductor laser mount 1 is kept at a constant temperature and does not thermally expand, the relational expression for thermal expansion is (l ₁ +l ₂ +l ₃ )×T×Ka−l ₃ ×T×Kb=0, and l ₃ = The thermal expansion absorbing damper 5 that satisfies (l ₁ +l ₂ )×Ka/Kb−Ka provides a light source device that outputs parallel light that is not affected by temperature changes.

FIG. 6 shows an embodiment in which an adhesive is used as the material for the thermal expansion absorbing damper 5. The thermal expansion of the fixed frame 4 is (l ₁ +l ₂ +l ₃ +l ₄ )×T×Ka, and the relational expression for thermal expansion is (l ₁ +l ₂ +l ₃ +l ₄ )×T×Ka−l ₁ ×T× Kc −l ₃ ×T×Kb=0, and l ₃ = {(l ₁ +l ₂ +l ₄ )×Ka−l ₁ ×Kc}/(Kb
-Ka), the light source device outputs parallel light without being affected by temperature changes.

According to the present invention, since it is possible to output highly accurate parallel light that is not affected by temperature changes, an optical system with small temperature dependence is possible.

[Brief explanation of drawings]

Fig. 1 is a related diagram of a semiconductor laser and a coupling lens, Fig. 2a is a conceptual diagram of a conventional semiconductor laser light source device, Fig. 2b is a conceptual diagram of a semiconductor laser light source device of the present invention, and Fig. 3 is a conceptual diagram of a semiconductor laser light source device of the present invention. 4 is a cross-sectional side view of the embodiment of FIG. 3, FIG. 5 is a diagram showing another embodiment of the present invention, and FIG. 6 is a diagram showing still another embodiment. . 1... Semiconductor laser, 2... Coupling lens,
3... Heat sink for heat dissipation, 4... Fixed frame, 5... Thermal expansion absorption damper, 6... Fine adjustment screw, 7... Pertuille element, 8... Laser emission point, 9... Lower end of coupling lens.

Claims (1)

[Claims] 1 comprising a light source, a lens that receives light from the light source, and a fixed frame to which the light source and lens are fixed;
and at least one of the light source and the lens,
A member, a part of which is fixed to the fixed frame and has a coefficient of thermal expansion different from that of the fixed frame, is fixed at a position that makes the distance between the lens and the light source shorter than the fixed position of the fixed frame and the member. A light source device, characterized in that the light source device is fixed to the fixed frame by being fixed to the fixed frame.