JP2009221415A - Material for infrared optical element and infrared optical element using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for IR optical elements, the material which is inexpensive and excellent in processability, and to provide IR optical elements using the material. <P>SOLUTION: The material 104 for IR optical elements comprises an IR transmitting resin 100 and IR transmitting inorganic particles 101 to 103 dispersed in the IR transmitting resin 100. The particle size distribution of the IR transmitting inorganic particles 101 to 103 is adjusted so as to appropriately suppress scattering of IR light by the IR transmitting inorganic particles 101 to 103 when the material 104 for IR optical elements transmit light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an infrared optical element material used for forming an infrared optical element and an infrared optical element using the material.

  Imaging optical systems include those that image visible light, those that image ultraviolet light, and those that image infrared light. Among them, imaging optical systems that image infrared light are used for monitoring purposes. For security purposes, it is often used to image infrared light emitted from a thermal object such as a human body.

  The emission spectrum intensity of infrared light emitted from a thermal object follows the radiation law. In applications such as intruder monitoring, infrared light having a peak intensity at a wavelength of about 10 μm emitted from the human body is a detection target. In the monitoring of an industrial plant apparatus that performs a thermal reaction, infrared light having a peak intensity at a wavelength of about 3 μm when the monitored temperature is high and about 5 μm when the temperature is low is a detection target.

  Examples of the imaging optical system used in such an infrared wavelength region include a reflection optical system, a refractive optical system, and a catadioptric optical system that combines a reflective optical system and a refractive optical system. In general, a reflection optical system that can use an optical element for visible light has a big problem that the field of view is narrow, and therefore, a refractive optical system and a catadioptric optical system are mainly used.

As materials constituting these optical systems, Ge, ZnSe, ZnS, and the like have been reported (for example, see Patent Documents 1 and 2). Moreover, AgCl, AgBr, etc. are also known as an infrared transmitting material (for example, refer patent document 3).
Japanese Patent Laid-Open No. 06-027368 Japanese Patent Laid-Open No. 04-125515 JP 05-0800002 A

  When Ge or Si is used as a material for forming an infrared transmission optical element, the infrared light transmittance is relatively good, but there is a problem in workability. Therefore, these materials are often used to form a spherical lens by polishing, and are not suitable for making aspherical surfaces.

  When ZnSe or ZnS is used as a material for an infrared optical element, the infrared transmittance is relatively good. However, these materials have a problem of high toxicity and material cost.

  When AgCl or AgBr is used as a material for an infrared optical element, Ag ions in the material are deposited as metallic Ag when irradiated with visible light or ultraviolet light, and the infrared transmittance is drastically reduced. There's a problem. Therefore, in order to shield visible light and ultraviolet light, it is necessary to provide a highly reliable film without a pinhole on the surface of an optical element formed of these materials. However, providing such a film not only leads to high costs, but also requires a lens barrel configuration and an assembling process that can hold the optical element without damaging the film. There's a problem.

  Therefore, an object of the present invention is to provide an infrared optical element material that has good processability such as moldability and can be reduced in cost, and an infrared optical element using the same.

  The present invention relates to a material for an infrared optical element used for forming an infrared optical element. The present invention relates to an infrared transmitting resin having transparency to infrared light, and having transparency to infrared light. Infrared transmitting inorganic particles mixed with a transmitting resin.

  In this case, the peak value of the particle size distribution of the infrared transmitting inorganic particles is preferably 70 nm or less.

  Alternatively, the ratio of particles having a particle size of 100 nm or more contained in the infrared transmitting inorganic particles is preferably 30% or less.

  When the particle size distribution of the infrared transmitting inorganic particles is adjusted as described above, the degree of scattering when infrared light passes through the infrared optical element material is moderately suppressed.

  The infrared transmitting inorganic particles are preferably water-soluble. In this case, as the infrared transmitting inorganic particles, particles obtained by spray-drying a solution containing an inorganic salt in a spray dryer can be used. The infrared transmitting inorganic particles preferably contain at least one of sodium chloride, potassium bromide, and potassium chloride.

  When producing inorganic infrared transparent particles by spray drying an inorganic salt aqueous solution with a spray dryer, controlling the inorganic salt concentration and spray dryer conditions (temperature, spraying speed, etc.) enables infrared having a desired particle size distribution. Transparent inorganic particles can be obtained.

  The infrared transmitting resin is preferably any one of a polyethylene resin, a cycloolefin resin, a fluorine resin, and a tetrafluoroethylene resin.

  When these resin materials are used, the material for infrared optical elements can be easily obtained by kneading the infrared transmitting inorganic particles after softening by applying heat.

  The present invention also relates to an infrared optical element that transmits infrared light, an infrared transmitting resin having transparency to infrared light, and an infrared transmitting resin having transparency to infrared light. Infrared transmitting inorganic particles mixed in the container.

  The infrared optical element is composed of an infrared transmitting resin and infrared transmitting inorganic particles mixed with the infrared transmitting resin, and has excellent workability. Therefore, an aspherical working surface can be provided to satisfactorily correct aberrations. .

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the material for infrared optical elements excellent in workability at low cost. Further, when the material for infrared optical elements according to the present invention is used, an optical element in which aberrations are favorably corrected can be realized at low cost by aspherical the formed working surface.

(Embodiment 1)
FIG. 1 is a partially enlarged view of an infrared optical element material according to Embodiment 1 of the present invention.

  The infrared optical element material 104 includes an infrared transmitting resin 100 and infrared transmitting inorganic particles 101 to 103 mixed with the infrared transmitting resin 100.

  The infrared transmitting resin 100 is desirably a thermoplastic resin so that the infrared transmitting inorganic particles can be held in a dispersed state therein and can be formed into an infrared optical element having a desired shape. In the present invention, it is desirable to use polyethylene resin, cycloolefin resin, fluorine resin or tetrafluoroethylene resin as the infrared transmitting resin. Characteristic absorption of resin material for light in the infrared region appears inherently and independently depending on the chemical bonding force between each atom of the molecule and the mass of each atom. Polyethylene resin, cycloolefin resin, fluorine system Resin or tetrafluoroethylene resin has little infrared absorption. In addition, since these resins are thermoplastic, they can be easily molded and are suitable for the infrared optical element material 104 according to the present invention.

  The infrared transmitting inorganic particles 101 to 103 are inorganic salts having transparency to infrared light. For example, sodium chloride, potassium bromide, and potassium chloride can be used. The infrared transmitting inorganic particles 101 to 103 are ideally mixed with the infrared transmitting resin in a state of being completely dispersed for each particle, but actually, as shown in FIG. In the permeable resin 100, a plurality of particles may be dispersed in an aggregated state. In this embodiment, the particle size distribution of the infrared transmitting inorganic particles 101 to 103 is adjusted so that desired optical characteristics can be obtained even in this case. Specifically, the peak value of the particle size distribution of the infrared transmitting inorganic particles 101 to 103 (before mixing with the infrared transmitting resin 100) is preferably 70 nm or less, and more preferably 65 nm or less.

  Infrared light in the vicinity of a wavelength of 3 μm on the short wavelength side is easily affected by scattering by the infrared transmitting inorganic particles 101 to 103. When the infrared light is scattered by the infrared transmitting inorganic particles 101 to 103 when passing through the infrared optical element material 104, unnecessary light serving as a flare component is generated. When the peak value of the particle size distribution of the infrared transmitting inorganic particles 101 to 103 exceeds 70 nm, the scattering intensity increases, and unnecessary light due to the flare component cannot be ignored during imaging.

  Here, the adjustment method of the infrared transmission inorganic particles 101-103 which concerns on this Embodiment is demonstrated.

  FIG. 2 is a schematic configuration diagram of an apparatus for producing infrared transmitting inorganic particles from an aqueous solution of an infrared transmitting inorganic salt.

  The manufacturing apparatus shown in FIG. 2 is mainly configured by a spray dryer 204 and a nozzle type atomizer 200 that sprays liquid in the spray dryer 204. The atomizer 200 is supplied with an aqueous solution of an inorganic salt serving as a material for the infrared transmitting inorganic particles from the storage tank 200 through the pipe 202. The spray dryer 204 is provided with a pipe 203 for blowing hot air from a hot air generator (not shown). The hot air blown from the pipe 203 is led to the vicinity of the jet outlet of the atomizer 200, and the inorganic salt aqueous solution sprayed from the atomizer 200 is instantly dried to deposit inorganic salt particles (infrared transmitting inorganic particles). The infrared transmitting inorganic particles obtained by spray drying are taken out through a pipe 205 provided at the lower part of the spray dryer 204.

  The particle size and particle size distribution of the generated infrared transmitting inorganic particles are controlled by adjusting the concentration of the inorganic salt aqueous solution, the spray amount per unit time, and the temperature of hot air blown into the spray dryer 204.

  As an example, spraying a sodium chloride aqueous solution with a concentration of 1% or less from a nozzle at a rate of 1 ml / min under the conditions of a spray dryer inlet hot air temperature of 200 ° C. and an outlet temperature of 150 ° C., a particle size distribution having a peak particle size of 65 nm Of sodium chloride particles were obtained. Moreover, even when potassium bromide or potassium chloride was used, particles having the same particle size distribution could be prepared under substantially the same conditions as in the case of sodium chloride.

  The surface properties may be improved by treating the surface of the infrared transmitting inorganic particles with a modifier. In this case, the aggregation of the infrared transmitting inorganic particles is suppressed to promote uniform dispersion in the infrared transmitting resin, or the wettability of the infrared transmitting inorganic particles is improved to facilitate mixing with the infrared transmitting resin. Can be improved.

  The material for infrared optical elements in which the infrared transmitting inorganic particles obtained by the above method are mixed with the infrared transmitting resin having good transmission characteristics with respect to the light in the infrared region is more than the original infrared transmitting resin. Excellent infrared transmission characteristics can be obtained. In addition, since the infrared optical element material according to the present embodiment has good moldability, it is easy to form an infrared optical element whose working surface is aspherical by molding, and therefore has good aberration. Infrared optical elements that can be corrected to be realized. Furthermore, according to the present embodiment, it is possible to reduce the cost of the infrared optical element material and the infrared optical element formed thereby.

  Further, sodium chloride, potassium bromide, and potassium chloride are materials having good infrared transmission characteristics, but have a problem that they are difficult to handle because of their hygroscopicity and deliquescence. However, in the present embodiment, since the infrared transmitting inorganic particles are dispersed and mixed in the infrared transmitting resin, it is isolated from moisture in the atmosphere. Restrictions on the use environment of the formed infrared optical element can be eliminated.

(Embodiment 2)
FIG. 3 is a partially enlarged view of an infrared optical element material according to Embodiment 2 of the present invention.

  The infrared optical element material 303 according to the present embodiment is composed of the same infrared transmitting resin 300 and infrared transmitting inorganic particles 301 and 302 as those according to the first embodiment. The particle size distributions 301 and 302 are slightly different from those according to the first embodiment.

  Specifically, in the present embodiment, the particle size distribution of the infrared transmitting inorganic particles is adjusted so that the proportion of particles having a particle size of 100 nm or more is 30% or less. When the ratio of particles having a particle size of 100 nm or more exceeds 30%, the intensity of scattered light from the infrared transmitting inorganic particles 301 and 302 increases, and unnecessary light due to flare components cannot be ignored during imaging. .

(Embodiment 3)
FIG. 4 is a schematic diagram showing a main part of an infrared imaging camera according to Embodiment 3 of the present invention.

  The infrared imaging camera 400 includes an infrared imaging device 405 that holds infrared lenses 401 and 402 and constitutes an infrared optical system 404, and an infrared imaging element 405 that outputs a signal corresponding to the intensity of received light. I have. The infrared lenses 401 and 402 are spherical or aspherical lenses formed by molding the infrared optical element material according to the first or second embodiment, for example, by hot pressing or injection molding.

  As described above, since the infrared optical element material according to the present invention is obtained by dispersing infrared transmitting inorganic particles in a thermoplastic infrared transmitting resin, the mold surface is formed by hot pressing or injection molding. Infrared lenses 401 and 402 having a transferred surface shape can be obtained easily and with high accuracy. Since an infrared lens having a high aberration correction capability can be realized by making the mold surface aspherical, it is possible to realize an infrared imaging optical system with a small number of infrared lenses and high resolution performance.

  The material for an infrared optical element according to the present invention can be used to form an infrared optical element used in an infrared imaging camera or the like.

The elements on larger scale of the material for infrared optical elements which concerns on Embodiment 1 of this invention Schematic configuration diagram showing an apparatus for producing infrared transmitting inorganic particles The elements on larger scale of the material for infrared optical elements which concerns on Embodiment 2 of this invention Schematic diagram showing the main part of an infrared imaging camera according to Embodiment 3 of the present invention.

Explanation of symbols

100, 300 Infrared transmitting resin 101-103, 301, 302 Infrared transmitting inorganic particles 104, 303 Infrared optical element material

Claims (8)

A material for an infrared optical element used for forming an infrared optical element,
An infrared transmitting resin having transparency to infrared light;
An infrared optical element material comprising infrared transmitting inorganic particles having transparency to infrared light and mixed with the infrared transmitting resin.   The infrared optical element material according to claim 1, wherein a peak value of a particle size distribution of the infrared transmitting inorganic particles is 70 nm or less.   The infrared optical element material according to claim 1, wherein a ratio of particles having a particle diameter of 100 nm or more contained in the infrared transmitting inorganic particles is 30% or less.   The infrared optical element material according to claim 2, wherein the infrared transmitting inorganic particles are water-soluble.   The infrared optical element material according to claim 4, wherein the infrared transmitting inorganic particles are particles obtained by spray drying a solution containing an inorganic salt in a spray dryer.   5. The infrared optical element material according to claim 4, wherein the infrared transmitting inorganic particles include at least one of sodium chloride, potassium bromide, and potassium chloride.   2. The infrared optical element material according to claim 1, wherein the infrared transmitting resin is any one of a polyethylene resin, a cycloolefin resin, a fluorine resin, and a tetrafluoroethylene resin. An infrared optical element that transmits infrared light,
An infrared transmitting resin having transparency to infrared light;
An infrared optical element comprising infrared transmissive inorganic particles having transparency to infrared light and mixed with the infrared transmissive resin.

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