JP2009031222A - Thermostatic bath and modulation transfer function measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a modulation transfer function measuring device that can measure an MTF (Modulation Transfer Function) value of an analyte containing an infrared optical element at high temperature and low temperature exceeding an operating temperature range of an infrared imaging device and can be constituted at low cost, and to provide a thermostatic bath constituting the modulation transfer function measuring device. <P>SOLUTION: This modulation transfer function measuring device comprises a case 11 having an opening for carrying in or out the analyte A containing the infrared optical element, a door body 12 blocked so as to open or close the opening, a support tool 15 for supporting the analyte A in the case in the thermostatic bath for keeping the temperature in the case 11 constant, and a front window section 13 and a back window section 14 of infrared light permeability arranged in the case 11 or the door body 12. The modulation transfer function measuring device has the thermostatic bath 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a constant temperature bath having an infrared light transmitting window, and a modulation transfer function for measuring a modulation transfer function (MTF: Modulation Transfer Function) of an object such as a lens or a mirror supported in the constant temperature bath. It relates to a measuring device.

  MTF is used as one of indexes indicating the optical characteristics of the optical element. The MTF represents a periodic structure such as a sine wave pattern as an object, and represents the change in contrast of the image of the object as a function of spatial frequency as it passes through the subject.

A modulation transfer function measuring apparatus for measuring the MTF of an infrared optical element includes a black body furnace that emits infrared light. The infrared light emitted from the black body furnace passes through the chart member on which the light and dark pattern is expressed, and becomes infrared light having light and dark. The infrared light transmitted through the chart member is reflected by the reflecting plate, becomes parallel light by the collimator, and enters the subject having the infrared optical element. The infrared light that has passed through the subject enters the infrared imaging device via the relay lens, and the infrared imaging device captures the image that has been formed. The infrared imaging device gives an image obtained by imaging to the MTF arithmetic device. The MTF computing device computes the MTF value based on the contrast of light and dark in the image obtained by imaging by the infrared imaging device.
The MTF value is an MTF value at a certain spatial frequency, for example, (maximum luminance−minimum luminance) / (maximum luminance + minimum luminance) based on the maximum luminance and minimum luminance of an image obtained when a bright and dark pattern is imaged. Is defined. Therefore, as the MTF value is smaller, the contrast is attenuated and a blurred image is formed. Note that the MTF may be obtained by Fourier transforming the intensity distribution of a point image or a line image.

In addition, since an object of absolute zero or higher emits infrared light, it has hitherto been more accurate to install a modulation transfer function measurement device in a low temperature darkroom. There has been proposed a modulation transfer function measuring apparatus capable of measuring the MTF of an infrared optical element even at room temperature by subtracting the background radiation component and calculating the MTF.
(Gerald C. Holst), “Testing and Evaluation of Infrared Imaging Systems (Press Monographs)”, (Society of Photo Optical), May 1999, p. 252

Incidentally, in-vehicle infrared optical elements, for example, lens units, are required to guarantee optical characteristics in a wide temperature range of −40 ° C. to 80 ° C.
However, since the operating temperature range of the infrared imaging element used in the current modulation transfer function measuring apparatus is narrow and can be measured only near room temperature, the MTF is measured in a wide temperature range of −40 to 80 ° C. There was a problem that could not.

  Further, even if an infrared imaging device capable of imaging in a wide temperature range is put into practical use, it is very expensive and there is a problem that a modulation transfer function measuring device cannot be manufactured at low cost.

The present invention has been made in view of such circumstances, and can measure the MTF value of a subject including an infrared optical element at a high temperature or low temperature exceeding the operating temperature range of the infrared imaging element. It is an object of the present invention to provide a modulation transfer function measuring device that can be configured at low cost and a thermostatic chamber that constitutes the modulation transfer function measuring device.

  The thermostatic chamber according to the first aspect of the present invention includes a housing having an opening for taking in and out the subject, and a door that closes the opening so as to be openable and closable, so that the temperature in the housing is kept constant. And a support that supports a subject including an infrared optical element in the casing, and an infrared light-transmitting window disposed on the casing or the door body. It is characterized by that.

In the first invention, the subject is supported in the casing by the support, and is maintained at a constant temperature in a state where the opening is closed by the door. In addition, since the infrared ray transmitting window portion is arranged on the casing or the door body, infrared light can be incident on the subject inside the casing from the outside of the casing through the window portion. Through the unit, infrared light can be emitted from the subject to the outside of the housing.
Therefore, when the modulation transfer function measuring apparatus having an infrared imaging device is equipped with the thermostatic chamber according to the present invention, the infrared imaging device is operated at room temperature by placing the subject at a constant temperature in the thermostatic bath. The MTF of the subject can be measured at a low temperature or high temperature exceeding the operating range of the image sensor.
In addition, a modulation transfer function measuring apparatus capable of measuring the MTF of the subject at a low temperature or a high temperature can be configured at a low cost.

  The thermostat according to a second aspect of the present invention has a plurality of the window portions, infrared light is incident on the subject from outside the casing through the one window portion, and the other window portions from the subject. The window portions are arranged to face each other so that infrared light is transmitted through the housing and emitted outside the housing.

In the second invention, among the plurality of windows, at least one window and the other windows are arranged to face each other, and infrared light transmitted through the one window is incident on the subject. It is configured to pass through and be emitted from the other window portion to the outside of the housing.
Therefore, information indicating the optical characteristics of the subject can be obtained by supporting a subject that transmits infrared light, such as an infrared lens, on a support.

  The constant temperature bath according to a third aspect of the present invention is characterized in that the window portion contains germanium, zinc sulfide, zinc selenide, or silicon.

In the third invention, the window portion includes germanium, zinc sulfide, zinc selenide, or silicon and transmits infrared light.
In particular, since the surface treatment of germanium is easy, an antireflection film can be easily provided on the window portion by forming the window portion with germanium, and more accurate information on optical characteristics can be obtained.
Moreover, since the window part of zinc sulfide and zinc selenide can be molded, the thermostat can be constructed at low cost.

  The constant temperature bath according to a fourth aspect of the invention is characterized in that the window has a shape that is long in a predetermined direction.

In the fourth invention, since the window portion is long in the predetermined direction, the infrared light can be incident on the subject from various directions by changing the incident direction of the infrared light along the longitudinal direction. Information on many optical properties can be obtained. Moreover, since the dimension in the direction substantially perpendicular to the longitudinal direction is shorter than the dimension in the longitudinal direction, the window can be made smaller than a circular window.
Therefore, a window part can be comprised at low cost, and the heat retention of a thermostat can be improved by making a window part small.

  A modulation transfer function measuring apparatus according to a fifth aspect of the invention is a constant temperature bath according to any one of the first to fourth aspects of the invention, an infrared light emitting apparatus that emits infrared light, and the infrared light emitting apparatus. A chart member that spatially modulates the infrared light, a collimator that makes the infrared light spatially modulated by the chart member parallel light, and enters the subject in the case; and from the subject to the outside of the case An infrared imaging device that images infrared light emitted from the light source, and an arithmetic device that calculates a modulation transfer function of the subject based on an image obtained by imaging by the infrared imaging device.

  In the fifth aspect of the invention, since the thermostat bath that keeps the temperature of the subject including the infrared optical element constant is provided, and the infrared imaging device is arranged outside the thermostat bath, the operating temperature of the infrared imaging device The MTF of the subject can be calculated at a high temperature or low temperature exceeding the range.

  According to the present invention, by providing the modulation transfer function measuring device with a thermostatic chamber having an infrared light transmissive window, the infrared optical element can be used at a high temperature or low temperature exceeding the operating temperature range of the infrared imaging device. The MTF of the object to be included can be measured, and it can be configured at low cost.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
FIG. 1 is a schematic view showing the thermostatic chamber 1 according to Embodiment 1 of the present invention, and FIG. 2 is a schematic perspective view showing the thermostatic bath 1 with the door body 12 opened. 1A is a perspective view of the thermostatic chamber 1 viewed from the front side, FIG. 1B is a plan sectional view of the thermostatic chamber 1, and FIG. 1C is a view of the thermostatic chamber 1 viewed from the back side. It is a perspective view. In the figure, reference numeral 1 denotes a thermostatic bath. The thermostatic bath 1 includes a hollow substantially rectangular parallelepiped housing 11 having a rectangular opening 17 on the front side, and the opening 17 is closed by a door 12 so as to be opened and closed. .

  The housing 11 has heat insulation properties, and is formed on the bottom plate 11a, the side walls 11b and 11c and the back wall 11d formed substantially perpendicular to the bottom plate 11a, and the upper end portions of the side walls 11b and 11c and the back wall 11d. The bottom plate 11a, the side walls 11b and 11c, and the front side end of the top plate 11e constitute an opening portion 17.

The door 12 has a rectangular shape that is substantially the same shape as the opening 17 when viewed from the front, and a disk-shaped front window 13 is disposed at a substantially central portion of the door 12. The front window portion 13 is made of germanium that is transparent to infrared light, and an antireflection film is formed on the surface. In addition, in order to improve the heat retaining property of the thermostatic chamber 1, the front window portion 13 may be configured by a plurality of germanium plates arranged to face each other through an air layer.
In addition, a plurality of hinges 16 are provided at a connecting portion between the door body 12 and the housing 11 so that the door body 12 is opened and closed and rotated to the front side. More specifically, one piece of the hinge 16 is screwed to the left side of the door body 12 in front view, and the other piece of the butterfly plate is screwed to the front side portion of the side wall 11b of the housing 11, A handle 12 a for opening and closing the door body 12 is attached to an appropriate portion of the door body 12, for example, the right side portion of the front surface.

  Similarly, a disc-shaped back window portion 14 is disposed at a substantially central portion of the back wall 11 d of the housing 11 so as to face the front window portion 13. The back window portion 14 is made of germanium that is transparent to infrared light, and an antireflection film is formed on the surface.

On the bottom plate 11 a of the housing 11, a support tool 15 that supports the subject A including an infrared optical element such as an infrared lens and a mirror in the housing 11 is erected. The support 15 is made of a substantially rectangular plate-like member that is fixed to the bottom plate 11 a in such a posture that the longitudinal direction is the vertical direction and one surface faces the back window portion 14, and the front window portion 13 and the back window portion 14. And a circular subject holding hole 12a for holding the subject A so that the optical axis of the subject A coincides with the optical axis of the subject A. The subject A held in the subject holding hole 12a is fixed by, for example, a male screw.

In addition, a heater, a fan, and a filter (not shown) are juxtaposed in the vicinity of the top plate 11e inside the housing 11. The heater heats the air in the housing 11 by energization, and the fan circulates the air in the housing 11. The filter has a metal net, and repairs and removes dust and foreign substances floating in the housing 11 as the air circulates.
Furthermore, the thermostatic chamber 1 is provided with a temperature detector for detecting the temperature in the housing 11 and, based on the detection result of the temperature detector, the heater 11 so that the temperature in the housing 11 matches a predetermined target temperature. A control circuit for turning on and off the power is provided.

  FIG. 3 is a block diagram illustrating a reflection-type modulation transfer function measuring apparatus according to Embodiment 1 including the thermostatic chamber 1. A modulation transfer function measuring apparatus according to Embodiment 1 of the present invention includes a black body furnace 2 (infrared light emitting apparatus) that emits infrared light, a chart member 3, a reflector 4, a collimator mirror 5, a thermostat 1, A relay lens 6, an infrared imaging device 7, and an MTF arithmetic device 8 are provided.

  The chart member 3 is disposed in the infrared light radiation region of the black body furnace 2, and the infrared light emitted from the black body furnace 2 enters the chart member 3.

  The chart member 3 is, for example, a transmission type continuous sine wave chart, and the infrared light transmitted through the chart member 3 becomes infrared light having light and darkness of a predetermined spatial frequency.

  A reflection plate 4 is disposed on the anti-blackbody furnace side of the chart member 3, and infrared light transmitted through the chart member 3 and reflected by the reflection plate 4 is deflected by approximately 90 degrees and enters the collimator mirror 5. To do.

  The collimator mirror 5 reflects the infrared light reflected by the reflecting plate 4 as parallel light and makes it enter the thermostat 1. The infrared light reflected by the collimator mirror 5 enters the housing 11 from the front window portion 13 of the thermostatic chamber 1, passes through the subject A, and passes from the rear window portion 14 provided in the housing 11 to the housing. The light is emitted outside the body 11.

  An image related to the infrared light transmitted through the subject A in the thermostat 1 is magnified by the relay lens 6 and enters the infrared imaging device 7. The infrared imaging device 7 includes an infrared lens and an infrared imaging element such as a thermopile or a bolometer. The infrared imaging device captures an image formed on the imaging surface by an infrared lens, that is, photoelectrically converts the intensity distribution of infrared light into the intensity distribution of the luminance signal, and supplies the image data obtained by imaging to the MTF arithmetic unit 8. Output.

The MTF arithmetic unit 8 includes a CPU, a ROM connected to the CPU via a bus, a RAM, an input / output interface, and the like. Image data output from the infrared imaging device 7 is input to the input / output interface. The The CPU captures image data via the input interface, performs image processing such as clipping of image portions necessary for modulation transfer function measurement and noise removal from the image data, and calculating a brightness difference between light and dark from the image data. An MTF value is calculated. In addition, although the process which calculates the MTF value with respect to one spatial frequency was demonstrated, the MTF value with respect to another spatial frequency can be calculated similarly, and MTF can be calculated | required.
Needless to say, the infrared imaging device 7 captures point images, line images, and other pattern images, and the MTF is calculated by Fourier transforming the intensity distribution of the luminance of the captured image. Also good.
When the calculation of the MTF is completed, the CPU outputs the MTF to an external liquid crystal display, CRT, printer or the like via the input / output interface.

In the modulation transfer function measuring apparatus and the thermostatic chamber 1 configured as described above, the subject A is placed at a constant temperature in the thermostatic chamber 1, and the subject A is passed through the infrared transparent front window portion 13 and the rear window portion 14. Infrared light can be transmitted. Therefore, the MTF of the subject A can be measured at a low temperature or a high temperature exceeding the operating range of the infrared imaging device 7 while operating the infrared imaging device 7 at room temperature.

  FIG. 4 is a schematic perspective view showing the configuration of the thermostatic chamber 101 according to the first modification. The thermostatic chamber 101 according to the first modification includes a housing 11 and a door body 112, and a substantially rectangular front window portion 113 formed in a substantially central portion of the door body 112 so that a longitudinal direction thereof is a lateral direction. It is arranged. A rear window 114 having the same shape as the front window 113 is disposed at a substantially central portion of the rear wall 11d of the housing 11 so that the longitudinal direction is the horizontal direction.

  FIG. 5 is a schematic diagram showing a main part of the modulation transfer function measuring apparatus in which the incident direction of the infrared light with respect to the subject A is changed. In the thermostatic chamber 101 according to the first modified example, as shown by a solid line and a two-dot chain line in FIG. 5, the red color with respect to the subject A along the longitudinal direction of the front window portion 113 and the rear window portion 114. By changing the incident direction of the external light, infrared light can be incident on the subject A from various directions, and the MTF of the subject A can be obtained.

  Moreover, since it can be made small compared with the circular front window part 113, the heat dissipation from the front window part 113 and the back window part 114 can be suppressed to the minimum, and the heat retention of the thermostat 101. Can be improved.

  FIG. 6 is a schematic view showing a thermostatic chamber 201 according to a second modification, and FIG. 7 is a schematic perspective view showing the thermostatic bath 201 with the door body 212 opened. The constant temperature bath 201 according to the second modification is different in that the door 212 is provided on the upper portion, and therefore, the difference will be mainly described.

  The casing 211 includes a bottom plate 211a, a front wall 211f, side walls 211b and 211c, and a rear wall 211d that are provided substantially perpendicularly to the bottom plate 211a, and has an opening 217 at the top. A front window part 13 and a rear window part 14 are arranged to face the front wall 211f and the rear wall 211d, respectively. That is, in the front window portion 13 and the rear window portion 14, infrared light that has passed through the front window portion 13 passes through the subject A supported by the support 15, and is emitted from the rear window portion 14 to the outside of the casing 211. Is arranged.

  The door body 212 has a rectangular shape that is substantially the same shape as the opening 217. The door body 212 and the housing 211 are connected by a plurality of butterfly plates so that the door body 212 opens and closes upward. A handle 212 a for opening and closing the door body 212 is provided at the front side edge of the door body 212.

  In the thermostatic chamber 201 configured as described above and the modulation transfer function measuring apparatus including the thermostatic chamber 201, the subject A can be taken in and out from above, and the usability of the thermostatic chamber 201 and the modulation transfer function measuring apparatus is improved. Can be improved.

  In the first embodiment, the modulation transfer function measuring apparatus capable of measuring the MTF of the subject at a high temperature using a thermostatic chamber equipped with a heater has been described. You may comprise so that MTF of the lower test object may be measured.

Moreover, although the thermostat bath which formed the front window part and the back window part with germanium was explained, the front window part and the back window part were formed with zinc sulfide, zinc selenide, silicon, or other infrared light transmitting members. You may do it.
In particular, when the front window portion and the rear window portion are molded with zinc sulfide or zinc selenide, the thermostatic chamber and the modulation transfer function measuring device can be configured at a lower cost than the germanium window.

  Furthermore, although the case where the thermostat equipped with two front window parts and the back window part was described was explained, the subject which can make infrared light enter and emit from one window part, for example, MTF of an infrared mirror, When measuring, you may comprise so that a single window part may be provided. Moreover, you may comprise so that three or more window parts may be provided as needed.

  Furthermore, although the thermostat is used for MTF measurement, the thermostat according to the present invention is used for another measuring apparatus that needs to obtain information on the optical characteristics of the subject including the infrared optical element from the outside. It may be applied. For example, it may be used to obtain information such as OTF (Optical Transfer Function) and PTF (Phase Transfer Function).

(Embodiment 2)
FIG. 8 is a block diagram schematically showing a transmission type modulation transfer function measuring apparatus according to Embodiment 2 of the present invention. The modulation transfer function measuring apparatus according to the second embodiment includes the black body furnace 2, the chart member 3, the thermostat 1, the relay lens 6, the infrared imaging device 7, and the MTF arithmetic device 8 similar to those of the first embodiment. In addition, a collimator lens 205 is provided in place of the collimator mirror 5 and each device is arranged in a straight line, which is different from the modulation transfer function measuring device according to the first embodiment.

  Even in the modulation transfer function measurement apparatus according to the second embodiment, as in the first embodiment, the MTF value of the subject A is measured at a low or high temperature compared to the operating temperature range of the infrared imaging device 7. Can do.

  Other configurations, operations, and effects of the thermostatic chamber 1 and the modulation transfer function measuring device according to Embodiment 2 are the same as the configurations, operations, and effects of the thermostatic chamber 1 and the modulation transfer function measuring device according to Embodiment 1. Therefore, corresponding portions are denoted by the same reference numerals, and detailed description thereof is omitted.

  It should be understood that the embodiment disclosed this time is illustrative in all respects and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic diagram which shows the thermostat which concerns on Embodiment 1 of this invention. It is a typical perspective view which shows the thermostat in the state which opened the door body. It is a block diagram which shows the reflection type modulation transfer function measuring apparatus which concerns on Embodiment 1 provided with the thermostat. It is a typical perspective view which shows the structure of the thermostat which concerns on a 1st modification. It is a schematic diagram which shows the principal part of the modulation transfer function measuring apparatus which changed the incident direction of the infrared light with respect to the subject. It is a schematic diagram which shows the thermostat which concerns on a 2nd modification. It is a typical perspective view which shows the thermostat in the state which opened the door body. It is a block diagram which shows typically the transmission type modulation transfer function measuring apparatus which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Constant temperature bath 2 Black body furnace 3 Chart member 4 Reflector plate 5 Collimator mirror 6 Relay lens 7 Infrared imaging device 8 MTF arithmetic unit 11 Housing | casing 12 Door body 13 Front window part 14 Back window part 15 Support tool 16 Hinge 17 Opening part A Subject

Claims (5)

A thermostatic bath comprising a housing having an opening for taking in and out the subject, and a door body that closes the opening so as to be openable and closable, and maintains a constant temperature in the housing,
A support for supporting a subject including an infrared optical element in the housing;
A thermostatic bath comprising: an infrared light transmissive window disposed on the housing or the door. There are a plurality of windows, and infrared light is incident on the subject from the outside of the casing through the one window, and the red light is transmitted to the outside of the casing from the subject through the other windows. The thermostat according to claim 1, wherein the window portions are arranged so as to emit external light. The window is
Germanium, zinc sulfide, zinc selenide, or silicon is contained. The thermostat according to claim 1 or claim 2 characterized by things. The said window part is a shape long in a predetermined direction. The thermostat as described in any one of Claim 1 thru | or 3 characterized by the above-mentioned. The thermostat according to any one of claims 1 to 4,
An infrared light emitting device that emits infrared light; and
A chart member that spatially modulates infrared light emitted from the infrared light emitting device;
A collimator that makes infrared light spatially modulated by the chart member parallel light and enters the subject in the housing;
An infrared imaging device that images infrared light emitted from the subject outside the housing;
A modulation transfer function measuring apparatus, comprising: an arithmetic unit that calculates a modulation transfer function of the subject based on an image obtained by the infrared imaging device.

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