JPH0529017U - Pass wavelength band controller for optical filter - Google Patents

Abstract

(57) [Abstract] [Purpose] In a semiconductor laser device, to allow light to pass through a thin film coating optical interference filter (interference filter) regardless of temperature changes. [Configuration] The interference filter 1 is provided with a rolling shaft 2, the moving end 402 of the bimetal 4 is brought into contact with the sliding plate 3, the sliding plate 3 is elastically balanced with the rolling shaft 2, and the sliding plate 3 is elastically balanced by the temperature change. A mechanism is provided in which the interference filter 1 is rotated by the deformation of the bimetal due to the temperature change of the semiconductor as the emission wavelength of the semiconductor changes, via the sliding plate 3 and the rolling shaft 2. [Effect] Even if the emission wavelength changes due to the temperature change, the temperature change of the bimetal 4 moves the equilibrium point between the sliding plate 3 and the rolling shaft 2 to rotate the interference filter 1, so that the emission wavelength changes the emission wavelength. Even if it changes, the light can pass through the interference filter 1.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pass wavelength band control device for controlling a pass wavelength band of an optical filter so as to deviate according to a temperature change. BACKGROUND OF THE INVENTION In order to distinguish light from a light source from other light (backlight), an optical filter having a central wavelength of light emitted from the light source in a pass band is provided on the optical axis of a light receiver. There is a device provided. By the way, in a semiconductor light emitting element such as a semiconductor laser element, the central wavelength of the emitted light changes due to a change in ambient temperature. Therefore, when a semiconductor light emitting element is used as a light source, the semiconductor light emitting element changes due to a change in ambient temperature. Light from the light emitting element does not pass through the optical filter. Especially when a semiconductor laser is used, a narrow band filter is used as the optical filter in order to take advantage of the fact that the laser light is light of a single spectrum, so that a small change in ambient temperature is caused. However, light does not pass through the optical filter. In order to avoid such a situation, in a device having a semiconductor light emitting element as a light source, the semiconductor light emitting element is placed in a constant temperature bath to keep the wavelength of emitted light constant, or a wavelength tunable optical filter is used. A general method is to use (for example, a Fabry-Perot type interference filter) and control so as to change the pass wavelength band of the optical filter in accordance with the change of the emission wavelength of the semiconductor light emitting element. A conventional passband bandwidth control device for an interference filter is provided with a rolling shaft on the interference filter so that the rolling shaft is rotated by a motor, and a drive circuit for the motor and a rotation angle of the motor. Has a potentiometer and a control circuit that are connected to the rotation axis of the motor, and the control circuit calculates the rotation angle of the motor (that is, the rolling axis of the interference filter) based on the wavelength data of the emitted light at the present time. Then, the motor is driven until the angle detected by the potentiometer matches the rotation angle. In the conventional interference filter pass wavelength band controller, the relationship between the temperature change and the emission center wavelength of the semiconductor light emitting element is calculated based on the ambient temperature change, and based on this, the relationship is calculated. In order to drive the motor, a control circuit mainly composed of a microcomputer (so-called CPU) capable of performing complicated calculations is required, and a motor drive mechanism is required, which makes the device configuration complicated and expensive. Further, particularly when receiving weak light (for example, when receiving reflected light attenuated while propagating in the air like a light receiving portion in a laser radar), the sensor has high sensitivity. Although a light receiving element is required, such an optical element is generally sensitive to electrical noise, and a driving system for an interference filter, which is the largest source of electrical noise, is provided in the vicinity of the light receiving element. Therefore, a large shield mechanism is required for the drive system, and the device becomes large. The present invention proposes to solve the above problems. In order to solve the above problems, the present invention uses a thin film coating optical interference filter (hereinafter referred to as “interference filter”) to provide a rolling axis on the filter. At the same time, for example, a bimetal or a shape memory alloy or the like, one end of the temperature sensitive body whose shape changes due to temperature change is set as a fixed end, and the other end is set as a moving end. By contacting the sliding plate fixed to the shaft with the rolling shaft, the shape change of the temperature sensitive body due to temperature change is transmitted to the rolling shaft to roll the interference filter. It is a thing. As is well known, in the thin film coating optical interference filter, since the passing wavelength band of light differs depending on the incident angle of light, the crossing angle between the interference filter and the optical axis of the light source is variably controlled. By doing so, the passing wavelength of the light of the interference filter can be changed. Therefore, in a device having a semiconductor light emitting element as a light source, if the intersection angle between the optical axis and the interference filter is changed according to the change in ambient temperature, the emitted light passes through the interference filter regardless of the change in the emission wavelength of the semiconductor light emitting element. You can The amount of change in the shape of the temperature sensitive body has a constant relationship with the change in ambient temperature, and the angle with respect to the optical axis of the interference filter has a constant relationship with the passing wavelength band. By controlling the rolling angle of the interference filter by changing the shape of the body, it is possible to change the pass wavelength band of the interference filter by following the center wavelength of the emitted light of the light source whose center wavelength changes due to temperature change. Embodiment of the Invention FIG. 1 is a perspective view showing a structure of a main part of an embodiment of the present invention, and FIG. 2 is a cooperation mechanism of a rolling shaft of an interference filter and a temperature sensitive body of the embodiment of the present invention. FIG. 3 is a plan view for explaining the operation of FIG. 3, and FIG. 3 is a sectional view showing the details of the fixed end side mechanism of the temperature sensitive body of the embodiment of the present invention. As shown in FIG. 1, in the pass wavelength band control device according to the present invention, a rolling shaft 2 pivotally supported by a bearing (for example, a pivot bearing, not shown) is attached to an interference filter 1. The sliding plate 3 is fixed to the rolling shaft 2 in a cantilever manner in a direction in which the longitudinal direction thereof is orthogonal to the axial center (rolling center) a of the rolling shaft 2. Further, a temperature sensitive body, for example, a bimetal (hereinafter, bimetal is taken as an example) 4 is formed in an arc shape, for example, and one end 401 thereof is fixed to a base (invariant portion) 5 as a fixed end. The end 402 is brought into contact with the sliding plate 3 as a moving end. A coil spring 6 is provided between the rolling shaft 2 and the base 5, and the rolling shaft 2 is always elastically biased in the direction of arrow b by the coil spring 6. The moving end 402 of the bimetal 4 is in contact with the sliding plate 3 from the direction opposite to the urging direction of the coil spring 6. Therefore, the moving end 402 of the bimetal 4 maintains the contact with the sliding plate 3 by the back tension applied by the coil spring 6 even if the shape of the bimetal 4 changes due to the temperature change. With such a configuration, the interference filter 1 rolls around the axis a of the rolling shaft 2 following the shape change of the bimetal 4, and the intersection angle θ between the optical axis c and the interference filter 1 (this The crossing angle θ is represented by the angle between the optical axis c and the direction orthogonal to the optical axis c. Therefore, by selecting the characteristics and shape of the bimetal 4 (for example, the diameter of a circular arc), the temperature-center wavelength characteristics of the light source (not shown) can be set to the pass wavelength band-tilt angle (θ) characteristics of the interference filter 1. If they are matched, the passing wavelength band (that is, the inclination angle θ) of the interference filter 1 can be controlled so that the light from the light source always passes through the interference filter 1 even if the ambient temperature of the light source changes. However, it is necessary that the bimetal 4 and the light source (light emitting element) are in the same environment (even if they are different in location, they should have the same atmosphere at least). The above operation will be described in more detail with reference to FIG. The moving plate 3 rolls around the rolling shaft 2 from a solid line state (3A) to a dashed line state (3B). At this time, the moving end 402 of the bimetal 4 moves while sliding on the plate surface of the sliding plate 3 along the longitudinal direction. That is, the locus of the contact point between the bimetal 4 and the sliding plate 3 changes in the longitudinal direction of the sliding plate 3 (this direction is referred to as the y direction) and changes in a direction orthogonal to this (this direction is the x direction). It can be decomposed into Now, assuming that the shape of the bimetal 4 is a circular arc of a perfect circle and the radius thereof is R, and the moving end 402 of the bimetal 4 is fixed to the sliding plate 3 (that is, (There is no movement in the y direction.) Considering that the deviation Δx of the moving end 402 in the x direction can be regarded as a part of the circumference of a true circle having a radius R, the deviation Δx and the above circumference can be considered. From the ratio, the deviation angle Δθ ′ is given by Can be approximated by By the way, the moving end 402 of the bimetal 4 actually moves in the y direction by Δy. That is, the radius of the arc of the bimetal 4 also changes to (R + Δy). Since this deviation Δy is smaller than the radius R, the actual deviation angle Δθ is obtained by replacing R in the equation (1) with (R + Δy). It can be approximated by By the way, when a semiconductor laser is used as a light source, the wavelength of the semiconductor laser changes in a linear relationship within a narrow range of temperature change. On the other hand, the relationship between the crossing angle θ of the interference filter 1 with respect to the optical axis c and the passing wavelength band is a function of cos θ. After all, if the relationship between the crossing angle θ of the interference filter 1 and the temperature change is set as a function of cos θ, the pass wavelength band of the interference filter 1 becomes the center wavelength of the semiconductor laser that linearly changes with temperature change. Can be matched. Therefore, in the equation (2), if the ratio of R and Δx, Δy is appropriately selected by selecting the characteristics and shape of the bimetal 4, it can be approximated to the function of cos θ. That is, the mechanism for sliding the moving end 402 of the bimetal 4 in the longitudinal direction of the plate surface of the sliding plate 3 constitutes a mechanism for converting the function of cos θ into a linear function, whereby the crossing of the interference filter 1 is performed. It is possible to track the angle θ with changes in the wavelength of the semiconductor laser. If a fine adjustment mechanism for semi-fixedly adjusting the fixed end 401 is provided on the fixed end 401 side of the bimetal 4, initializing work of the pass wavelength band of the interference filter 1 becomes easy. This fine adjustment mechanism is configured, for example, as shown in FIG. That is, the fixed end 401 of the bimetal 4 is fixed to the holding structure 7 provided with the screw holes 701, and the holding structure 7 is slidably fitted inside the guide portion 501 provided on the base 5, so that the bimetal 4 is fixed. An adjusting screw 9 is provided between the base 5 and the holding structure 7 with a coil spring 8 urged in a direction away from the base 5 interposed (the adjusting screw 9 is screwed into a screw hole 701 of the holding structure 7). ing.). In this mechanism, the fixing position of the fixed end 401 of the bimetal 4 to the base 5 can be semi-fixedly adjusted by turning the adjusting screw 9, and this adjustment allows the moving end 402 of the bimetal 4 to move. Since the position also changes, the initial angle of the interference filter 1 can be adjusted to the angle of the pass wavelength band whose center wavelength is the emission wavelength of the light source at that time. In the above embodiment, the shape of the bimetal 4 is arcuate, but the shape is not limited to arcuate as long as the rolling shaft 2 rolls. However, in order to simplify the relationship between the temperature and the pass wavelength band of the interference filter 1, a perfect circular arc shape is optimal. Further, although the bimetal is used for the temperature sensitive body in the embodiment, a shape memory alloy may be used instead of the bimetal. When a shape memory alloy is used, it is used within a range in which the temperature-shape change characteristic of the shape memory alloy exhibits a linear characteristic. That is, in other words, a shape memory alloy having linear characteristics in the expected temperature change range is used. Further, although the above-described embodiment is an example in which the interference filter is carried out, any optical filter having a characteristic that the passing wavelength band is changed by the change of the crossing angle with the optical axis is used. It is possible to carry out this invention. As described above in detail, according to the present invention, a thin film coating optical interference filter, which is originally used with a fixed pass wavelength band, is used. The crossing angle of the optical filter with respect to the optical axis is changed by changing the shape of the temperature sensitive body due to the temperature change, and an expensive and complicated control circuit mainly composed of a so-called CPU, a motor drive mechanism, etc. are required. do not do. Further, since no electric noise generation source is used at all, even in a device handling particularly weak light, a shield mechanism for the electric noise generation source is not required at all. Further, by adopting a mechanism for performing linear correction in the mechanism section that converts the shape change of the temperature sensitive body into the rolling angle of the optical filter, the pass wavelength band of the optical filter is changed in the wavelength of the light of the light emitting source. Can be successfully tracked. As described above, the present invention provides a pass wavelength band control device for an optical filter that can accurately follow the wavelength change of emitted light with a very simple mechanism, is resistant to noise, and is small, lightweight and inexpensive. It is provided and has an extremely remarkable effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing the structure of the essential parts of an embodiment of the present invention. FIG. 2 is a plan view illustrating the operation of the embodiment of the present invention. FIG. 3 is an embodiment of the present invention. A cross-sectional view showing the mechanism of the temperature-sensing body fixing part of [No. of symbols] 1 ... Thin film coating optical interference filter (interference filter) 2 ... Rolling shaft 3 ... Sliding plate 4 ... Temperature sensing body (bimetal) 401 ... Fixed end 402 ... Moving end

Claims (1)

[Claims for utility model registration] [1] In a device that allows light emitted from a light source whose center wavelength of emitted light fluctuates due to changes in ambient temperature to pass through separately from back light, the device is affected by changes in the incident direction of the light. A rolling axis is provided on the optical filter whose light passing wavelength band changes, and one end of the temperature sensitive body whose shape changes due to temperature change is used as a fixed end and the other end is a moving end of the temperature sensitive body. In cooperation with the rolling axis of the optical filter, by controlling the rolling of the optical filter by the shape change of the temperature sensitive body, the central wavelength of the emitted light of the light source is always in the passing wavelength band of the optical filter. An optical filter pass wavelength band control device which is included. [2] A sliding plate is cantilevered on the rolling shaft of the optical filter, and the sliding plate is elastically biased in one direction of rotation about the rolling shaft to provide a temperature-sensing body. 2. The pass wavelength band control device for the optical filter according to claim 1, wherein the moving end of the optical filter is brought into contact with the surface of the sliding plate from the opposite biasing direction. 3. The temperature sensitive body is a bimetal.
A pass wavelength band control device for the optical filter according to. 4. The pass wavelength band control device for an optical filter according to claim 1, wherein the temperature sensitive body is a shape memory alloy.