JP2013050640A - Temperature controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature controller capable of accurately controlling temperature in the center part of an optical element.SOLUTION: A temperature controller for an optical element having a first main surface and a second main surface opposing to the first main surface includes: a first housing having contact with the first main surface with a fixed contact thermal resistance; a second housing having contact with the second main surface with a fixed contact thermal resistance in an area equal to a contact area between the first housing and the first main surface; a temperature adjustment element for adjusting the temperature of the first housing; a first temperature measurement element for measuring the temperature of the first housing; a second temperature measurement element for measuring the temperature of the second housing; and a controller for defining an average value between the measured temperature of the first housing measured by the first temperature measurement element and the measured temperature of the second housing measured by the second temperature measurement element as the temperature of the optical element, and controlling the temperature adjustment element to adjust the temperature of the first housing thereby to allow the average value to be a predetermined setting value.

Description

  The present invention relates to a temperature control device that controls the temperature of an optical element.

  As a method of controlling the temperature of an optical element such as a wavelength conversion element, a method of bringing a thermoelectric element or the like into contact with the optical element is employed. For example, a method for controlling the temperature of an optical element by fixing the optical element by sandwiching it with a casing having good thermal conductivity and controlling the temperature of one casing by a thermoelectric element has been proposed (for example, patents). Reference 1).

JP 2001-305592 A

  However, the above method only monitors the temperature of one casing, and there is a possibility that a large deviation occurs between the temperature of the lower surface of the optical element and the temperature of the upper surface depending on the ambient environmental temperature. This is because it is difficult to consider the effects of convection and the like, and the center temperature of the optical element cannot be controlled with high accuracy by simply monitoring the temperature of one casing. The deviation between the monitoring temperature and the actual temperature of the optical element that occurs when the temperature of only one surface of the optical element is monitored greatly affects the characteristics of the optical element.

  In view of the above problems, an object of the present invention is to provide a temperature control device that can accurately control the temperature of the central portion of an optical element.

  According to one aspect of the present invention, there is provided a temperature control device for an optical element having a first main surface and a second main surface opposite to the first main surface, and (a) constant on the first main surface. A first casing that contacts with the first main surface, and (b) an area that is equal to an area where the first casing and the first main surface are in contact with each other and is in contact with the second main surface with a constant contact thermal resistance. 2) (c) a temperature adjusting element that adjusts the temperature of the first casing; (d) a first temperature measuring element that measures the temperature of the first casing; and (e) a second. A second temperature measuring element that measures the temperature of the first housing, and (f) a measured temperature of the first casing measured by the first temperature measuring element and a second measured by the second temperature measuring element. The temperature of the first housing is adjusted by controlling the temperature adjustment element so that the average value of the measured temperature of the housing is the temperature of the optical element and the average value is a preset value. Temperature control device and a control device is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the temperature control apparatus which can control the temperature of the center part of an optical element accurately can be provided.

It is a schematic diagram which shows the structure of the temperature control apparatus which concerns on embodiment of this invention. It is a graph which shows the relationship between environmental temperature, the temperature difference of a 1st housing | casing, and the temperature difference of a 1st housing | casing and a 2nd housing | casing. It is a schematic diagram which shows the model for demonstrating the temperature difference of a 1st housing | casing and a 2nd housing | casing. It is a graph which shows the temperature characteristic of the SHG light output of an optical element. It is a schematic diagram which shows the structure of the temperature control apparatus which concerns on the modification of embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions is different from the actual one. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention include the material, shape, structure, arrangement, etc. of components. Is not specified as follows. The embodiment of the present invention can be variously modified within the scope of the claims.

  The temperature control apparatus 10 for an optical element according to an embodiment of the present invention is a temperature control apparatus for an optical element 100 having a first main surface 101 and a second main surface 102 facing the first main surface 101. As shown in FIG. 1, the temperature control device 10 includes a first casing 11 that contacts the first main surface 101 of the optical element 100 and a second casing that contacts the second main surface 102 of the optical element 100. 12, a temperature adjustment element 13 that adjusts the temperature of the first casing 11, a first temperature measurement element 14 that measures the temperature of the first casing 11, and the temperature of the second casing 12. A second temperature measuring element 15 and a control device 16 for controlling the temperature adjusting element 13. The control device 16 determines the average value of the measured temperature of the first casing 11 measured by the first temperature measuring element 14 and the measured temperature of the second casing 12 measured by the second temperature measuring element 15. The temperature of the first casing 11 is adjusted by controlling the temperature adjustment element 13 so that the average value is a preset value. This set value is set to a temperature having the best characteristics according to the temperature characteristics of the optical element 100, for example. The optical element 100 is, for example, a wavelength conversion element.

The first housing 11 is in contact with the first main surface 101 with a constant contact thermal resistance h ₁ . The second housing 12 is in area equal to the area of the first housing 11 and the first major surface 101 is in contact, in contact with a constant contact thermal resistance h ₂ to the second major surface 102. The optical element 100 is sandwiched and supported by the first casing 11 and the second casing 12 so that the contact thermal resistance h ₁ and the contact thermal resistance h ₂ are equal.

  The first casing 11 and the second casing 12 are made of, for example, the same material having a high thermal conductivity. An aluminum (Al) alloy material, brass, or the like can be used for the first housing 11 and the second housing 12.

The first temperature measuring element 14 is disposed inside or on the surface of the first casing 11, and the temperature of the first casing 11 is measured by the first temperature measuring element 14. The measured temperature of the first housing 11 measured by the first temperature measuring element 14 is hereinafter referred to as “first measured temperature T _M1 ”. Similarly, the second temperature measuring element 15 is disposed inside or on the surface of the second casing 12, and the temperature of the second casing 12 is measured by the second temperature measuring element 15. The measured temperature of the second housing 12 measured by the second temperature measuring element 15 is hereinafter referred to as “second measured temperature T _M2 ”. For example, the temperature of the central portion can be measured by making a hole in the first housing 11 or the second housing 12 and inserting a thermistor.

Since the thermal conductivity of the first casing 11 and the second casing 12 is high, the temperature of the first main surface 101 of the optical element 100 is equal to the first measurement temperature T _M1 , and the second of the optical element 100 It can be considered that the temperature of the main surface 102 is equal to the second measured temperature T _M2 .

As the temperature adjustment element 13, a thermoelectric element such as a Peltier element can be employed. When using the thermoelectric element to the temperature adjusting element 13, as shown in FIG. 1, according to the current S _T magnitude supplied to the temperature regulation element 13 by the current controller 131, the temperature of the first housing 11 is adjusted Is done. Controller 16, the first measured temperature T _M1 on the basis of the second measured temperature T _M2, controls the current S _T supplied to the temperature regulation element 13 by the signal Sc, controls the temperature of the optical element 100 .

In the temperature control device 10, the first casing 11 and the second casing 12 are formed of the same material, and the area where each of the first casing 11 and the second casing 12 contacts the optical element 100 is determined. Make equal. At this time, the contact thermal resistance h ₁ between the first housing 11 and the first main surface 101 of the optical element 100 and the contact heat between the second housing 12 and the second main surface 102 of the optical element 100 are shown. By designing the temperature control device 10 so that the resistance h ₂ is equal, the average value of the first measurement temperature T _M1 and the second measurement temperature T _M2 is the temperature of the central portion of the optical element 100 in the film thickness direction. Can be considered. In order to make the contact thermal resistance h ₁ and the contact thermal resistance h ₂ equal, for example, the surface accuracy and the surface roughness of the surfaces of the first casing 11 and the second casing 12 that are in contact with the optical element 100 are equal. do it.

By making the areas where the first housing 11 and the second housing 12 contact the optical element 100 equal, and making the contact thermal resistance h ₁ and the contact thermal resistance h ₂ equal, the control device 16 Controls the temperature adjustment element 13 using the average value of the first measurement temperature T _M1 and the second measurement temperature T _M2 as the temperature of the optical element 100, and adjusts the temperature of the optical element 100 to a desired set value. it can. For example, the control device 16 controls the temperature adjustment element 13 so that the average value of the first measurement temperature T _M1 and the second measurement temperature T _M2 becomes a temperature at which the performance of the optical element 100 is best exhibited. .

  Below, the effect of the temperature control of the optical element 100 by the temperature control apparatus 10 according to the embodiment of the present invention will be described.

The graph shown in FIG. 2 shows the temperature difference ΔT ₁₂ between the first casing 11 and the second casing 12 when the temperature control of the optical element 100 is not performed by the control device 16, and the first casing 11. And the temperature difference ΔT _1a between the ambient temperature Ta and the ambient temperature Ta. Here, the “environment temperature” is the temperature around the optical element 100 and the temperature control device 10 at the time of temperature measurement, for example, the temperature of room air. At this time, the size of the optical element 100 is 15 mm in length, 2 mm in width, and 1 mm in thickness. The material of the first casing 11 and the second casing 12 is made of an Al alloy. The second casing 12 has a length of 20 mm, a width of 30 mm, and a thickness of 3 mm. It is assumed that it is sufficiently large with respect to the second housing 12.

The factors causing the temperature difference ΔT ₁₂ shown in FIG. 2 are due to heat conduction and heat transfer between the first housing 11 and the second housing 12 and due to surrounding convection. This point will be described below using the model shown in FIG. It is assumed that there is no heat source inside the optical element.

  In the model shown in FIG. 3, the temperature measuring element 14M is arranged only in the first casing 11M, and the temperature measuring element is not arranged in the second casing 12M. That is, the temperature of the second housing 12M is not monitored, and only the temperature of the first housing 11M is monitored. In FIG. 3, the flow of the heat quantity Q is indicated by an arrow.

  If the temperature of the fluid around the optical element 100M, for example, the air, is the environmental temperature Ta, and the temperature of the central portion of the optical element 100M in the film thickness direction is the central temperature Ts, the optical temperature is not equal to the central temperature Ts. Heat transfer occurs between the element 100M and the fluid. For simplicity, a one-dimensional model is used for explanation.

The amount of heat Q penetrating the optical element 100M is defined as follows: the temperature of the first main surface 101 is T _S1 , the temperature of the second main surface 102 is T _S2 , and the thermal resistance at half the thickness of the optical element 100 is h _s . It is represented by the following formula (1):

Q = (T _S1 −T _S2 ) / 2h _s (1)

On the other hand, the temperature difference ΔT ₁₂ between the first casing 11M and the second casing 12M is expressed by Equation (2), where T1 is the temperature of the first casing 11M and T2 is the temperature of the second casing 12M. expressed:

ΔT ₁₂ = T1−T2 = Q × (h ₁ + h ₂ + 2h _s ) (2)

In Formula (2), h ₁ is the contact thermal resistance between the first casing 11M and the first main surface 101 of the optical element 100M, and h ₂ is the second main resistance of the second casing 12M and the optical element 100M. It is a contact thermal resistance with the surface 102. Note that, since the first casing 11M and the second casing 12M are made of a material having high thermal conductivity, the temperatures of the first casing 11M and the second casing 12M are uniform.

Relationship between the temperature difference [Delta] T _1a of the ambient temperature Ta is the temperature of the temperature T1 and the fluid in the first housing 11M, the table in equation (3) the thermal resistance between the second housing 12M fluid as ha Is:

ΔT _1a = T1-Ta = Q × (h ₁ + h ₂ + 2h _s + ha) (3)

The thermal resistance ha is small in the laminar flow region and large in the turbulent region. From equations (2) and (3), the following equation (4) is obtained:

T1−T2 = {(h ₁ + h ₂ + 2h _s ) / (h ₁ + h ₂ + 2h _s + ha)} × (T 1 −Ta) (4)

Since h ₁ , h ₂ , and h _s are constants, equation (5) is obtained as h ₁ + h ₂ + 2h _s = A:

T1-T2 = {1 / (1 + ha / A)} × (T1-Ta) (5)

As shown in Expression (5), in the laminar flow region where the temperature difference between the fluid and the first casing 11 is small, the thermal resistance ha is small, and therefore, the temperature T1 of the first casing 11 and the temperature of the fluid. The inclination of the temperature difference ΔT ₁₂ between the first casing 11 and the second casing 12 with respect to the temperature difference ΔT _1a with the environmental temperature Ta is large. On the other hand, in the turbulent flow region where the temperature difference between the fluid and the first housing 11 is large, the thermal resistance ha is large, so that the gradient of the temperature difference ΔT ₁₂ with respect to the temperature difference ΔT _1a is small (see FIG. 2). The reason why the temperature difference ΔT ₁₂ varies in the turbulent flow region where the temperature difference between the environmental temperature Ta and the temperature T1 of the first housing 11 is large is that fluctuation due to turbulent flow has an effect.

  As described above, it is difficult to consider the influence of convection and the like only by monitoring the temperature of the first housing 11 without monitoring the temperature of the second housing 12. As a result, it is impossible to accurately grasp the temperature of the central portion of the optical element 100 and control the temperature with high accuracy. In this case, the characteristics of the optical element 100 are greatly affected. For example, the optical output obtained from the wavelength conversion element is greatly affected by the temperature change of the wavelength conversion element. As an example, in the case of an MgLN wavelength conversion element having an element length of 15 mm, as shown in FIG. The output of the second harmonic generation light (SHG light) is reduced to half. Thus, sufficient performance cannot be obtained when the temperature of the optical element 100 cannot be accurately controlled.

On the other hand, in the temperature control device 10 of the optical element 100 shown in FIG. 1, h ₁ = h ₂ . For this reason, from equation (2):

T1−T2 = 2Q × (h ₁ + h _s ) (6)

Is established. Note that T1 = T _M1 and T2 = T _M2 . Further, the temperature difference T1-Ts between the first casing 11 and the central temperature Ts in the central portion of the optical element 100 in the film thickness direction is expressed by the following equation (7):

T1−Ts = Q × (h ₁ + h _s ) (7)

Thus, the following equation (8) holds:

Ts = (T1 + T2) / 2 = (T _M1 + T _M2 ) / 2 (8)

As shown in Expression (8), the center temperature Ts does not depend on the thermal resistance ha. That is, even in the laminar flow region shown in FIG. 2, even when fluctuation occurs in the turbulent region, the average value of the first measurement temperature T _M1 and the second measurement temperature T _M2 is the center of the optical element 100. The temperature of the part.

  The temperature T2 of the second housing 12 depends on the environmental temperature Ta, but is about 0 ° C. to 50 ° C., for example. The temperature T1 of the first housing 11 depends on the performance of the temperature adjustment element 13, but can be set to about 20 ° C. to 200 ° C., for example. The performance of the temperature adjustment element 13 that sets the temperature T1 of the first housing 11 is determined by the environmental temperature Ta and the temperature at which the performance of the optical element 100 is exhibited.

  Although the temperature control device 10 can control the temperature in the vicinity of the center of the optical element 100, there is a possibility that temperature distribution may occur in the optical element 100 itself depending on the environmental temperature Ta. For example, when the difference between the ambient temperature and the temperature desired for the optical element 100 is large. However, for example, as shown in FIG. 2, the temperature difference when the thickness of the optical element 100 is 1 mm is 1 ° C., and the beam diameter of light is generally about 200 μm. Only a temperature difference of about 2 ° C. occurs. For this reason, when temperature distribution arises in optical element 100 itself, there is no big influence on the characteristic of optical element 100.

  As described above, according to the temperature control apparatus 10 according to the embodiment of the present invention, the temperature of the central portion of the optical element 100 can be accurately controlled regardless of the environmental temperature Ta or the influence of convection. As a result, the performance of the optical element 100 can be exhibited sufficiently. In addition, since the temperature control device 10 uses only one temperature adjusting element 13, it can be downsized.

  Further, since the temperature control device 10 is in contact with only two surfaces of the optical element 100, an optical of an arbitrary size can be obtained by changing the distance between the first housing 11 and the second housing 12. It is possible to support the element 100 and control the temperature of the optical element 100. For example, as shown in FIG. 5, a spring 17 is disposed between the first casing 11 and the second casing 12, and the spring 17 is connected to the first casing 11 and the second casing 12 by a pin 18. Secure to.

  As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

In the above description, the surroundings of the optical element 100 and the temperature control device 10 are air. However, even if the surroundings are other than air, for example, in an environment in which convection occurs in the surroundings, such as in nitrogen (N ₂ ) gas. The temperature control device 10 can control the temperature of the optical element 100 with high accuracy.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 10 ... Temperature control apparatus 11 ... 1st housing | casing 12 ... 2nd housing | casing 13 ... Temperature adjustment element 14 ... 1st temperature measurement element 15 ... 2nd temperature measurement element 16 ... Control apparatus 100 ... Optical element 101 ... 1st main surface 102 ... 2nd main surface 131 ... Current controller

Claims (3)

A temperature control device for an optical element having a first main surface and a second main surface opposite to the first main surface,
A first housing that is in contact with the first main surface with a constant contact thermal resistance;
A second casing that is in contact with the second main surface with the constant contact thermal resistance, in an area equal to an area in which the first casing and the first main surface are in contact with each other;
A temperature adjusting element for adjusting the temperature of the first housing;
A first temperature measuring element for measuring the temperature of the first housing;
A second temperature measuring element for measuring the temperature of the second housing;
The average value of the measured temperature of the first casing measured by the first temperature measuring element and the measured temperature of the second casing measured by the second temperature measuring element is the value of the optical element. A temperature control device comprising: a control device configured to control the temperature adjustment element so as to adjust the temperature of the first casing so that the average value is a preset setting value.   2. The temperature adjustment device according to claim 1, wherein the temperature adjustment element is a thermoelectric element, and the control device controls the temperature of the first housing by controlling a current supplied to the temperature adjustment element. Temperature control device.   The temperature control apparatus according to claim 1, wherein a distance between the first casing and the second casing is variable.

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