JP2005128169A - Optical element cooling device and video projector - Google Patents

Abstract

An object of the present invention is to provide a cooling device for an optical element that has a simpler structure and is less expensive, eliminating the use of a liquid that is an optical coupling medium, eliminating the need for a liquid sealing operation that requires a complicated assembly process. And
A heat dissipating body having a metal as a main component and a resin molded body having light transmittance and being united and bonded to the heat dissipating body at the time of resin injection molding are provided. A cooling device for an optical element having a plurality of comb-like uneven portions 48b at a joint portion with a resin molded body 49 and black nickel plating on the surface thereof.
[Selection] Figure 7

Description

  The present invention relates to a cooling device for an optical element such as a glass prism and a video projector using the same.

  Recently, video projectors using a digital micromirror device (hereinafter referred to as DMD) as an image creation element have become widespread, and many have been sold in the market. The DMD is manufactured by a process similar to the semiconductor manufacturing process, and has a configuration in which a number of micromirrors each having a side of several microns are aligned vertically and horizontally on a silicon substrate.

  In one DMD chip, hundreds of thousands to millions of micromirrors are arranged, and each one functions as one pixel for image creation (for example, refer to Patent Document 1).

  The micromirror functioning as one pixel performs a seesaw motion by turning on and off an electrical signal with a predetermined axis as a rotation axis. Therefore, the micromirror takes two positions, that is, an ON position of the electric signal and an OFF position.

  FIG. 1 is a diagram showing the configuration and operation of the micromirror in the DMD 1. The light beam L incident on the micromirrors 2 (enlarged and displayed for explanation) arranged in the DMD 1 obliquely from the lower left is divided into two directions depending on which of the micromirrors 2 is inclined. . When the electrical signal is ON, the position m is taken, and the reflected light is emitted in the direction of Rm. When the electrical signal is OFF, the position n is taken and the reflected light is emitted in the direction of Rn.

  FIG. 2 is a schematic configuration diagram of a conventional video projector using a DMD. As shown in the figure, the conventional video projector includes a rectangular parallelepiped color prism 3 and triangular prisms 4 and 5. The DMD 1 is installed so that the micromirror 2 faces one surface of the color prism 3. In addition, the projection lens 8 is installed against the surface of the color prism 3 opposite to the surface on which the DMD 1 is disposed. A prism 4 is installed between the projection lens 8 and the color prism 3 so that the side surface is parallel to the side surface of the color prism 3, and the prism 5 is installed so that the side surface of the prism 4 and one side surface are parallel. Has been. These prisms 4 and 5 are installed so that the triangular shape which is the bottom surface is turned upside down, and a very thin parallel air layer 6 (the air layer thickness is about 5 microns) is formed between the opposing surfaces. Further, in order to absorb and extinguish unnecessary light, a prism cooling device 9 for cooling the color prism 3 is installed on the side surface other than the DMD 1 and the prism 4 are installed.

  Next, the operation of the conventional video projector having the above configuration will be described below.

  In FIG. 2, the light beam incident from the direction A is totally reflected by the inclined surface 4a of the prism 4 (because there is an air layer 6 between the prisms 4 and 5, it is totally reflected). The light beam reflected by the inclined surface 4 a travels along the optical path L and exits from the right side surface of the color prism 3. When light rays are emitted from the glass of the color prism 3 into the air, refraction occurs as shown in FIG. The light beam emitted from the right surface of the color prism 3 enters the micromirror 2 in the DMD. When the micromirror 2 is at the position m, the reflected light passes through the prisms 3, 4 and 5 and travels in the direction of Rm.

  Light rays emitted from the prism 5 enter the projection lens 8, and an image is enlarged and projected onto a screen (not shown) installed in front of the projection lens 8.

  The parallel light beam incident from the A direction is a strong uniform light beam having an extremely high energy density. This light beam is incident on a group of micromirrors 7 of the DMD, and each micromirror is driven at a very high speed by a video signal, and the incident light is distributed to projection light and unnecessary light. An image is formed by a combination of a number of light beam groups reflected by individual micromirrors 7 (corresponding to individual pixels).

  The contrast of the image is expressed by the difference in the accumulated time during which the individual micromirrors 7 are driven in the projection direction within a certain time by being driven ON-OFF at high speed.

  Here, when the micromirror 7 is at the position n, the reflected light (unnecessary light) travels in the Rn direction. The light beam traveling in the Rn direction is unnecessary light, and it is necessary to absorb and extinguish it as quickly as possible in order to avoid a decrease in contrast and ghosting due to reflection and scattering. For this purpose, a prism cooling device 9 is mounted on the upper surface of the color prism 3.

  If the prism cooling device 9 is not provided, as shown in FIG. 3, the unnecessary light reflected from the micromirror 2 in the direction of R <b> 1 travels through the color prism 3, and the upper surface of the color prism 3. The light is totally reflected by 3a and is not emitted outside the color prism 3. This is because if the refractive index of the glass is Nd = 1.52, the total reflection angle is 41.14 °, and the incident angle is larger than this angle.

  Since a part of the energy of the unnecessary light R1 reflected as described above changes to heat inside the color prism 3, the temperature of the color prism 3 becomes extremely high, and the prisms or the color prism 3 is a base (not shown). )), The adhesive is deteriorated due to heat, causing various problems. Further, the unnecessary light R1 reflected by the upper surface 3a of the color prism 3 follows the path of each of the prisms 3, 4, and 5 with R2, R3, and R4, goes out to the periphery of the prism, is scattered as unnecessary light, and is projected. Serious problems such as deterioration of the contrast of the image, generation of a ghost image, and increase in the temperature of the part where the light beam reaches.

  Next, the conventional prism cooling device 9 will be described. FIG. 4 is a block diagram of a conventional prism cooling device 9. The heat sink 10 made of a metal having good thermal conductivity such as copper, copper alloy, aluminum or the like has good light absorption and has a matte black surface finish to improve heat dissipation (for example, , Black nickel plating). The heat sink 10 has heat radiating fins 10a to enhance the heat radiating effect.

  A plurality of comb-like protrusions 10b are formed on the bottom surface of the heat sink 10 in order to efficiently attenuate incident light rays. As shown in FIG. 5, most of the light rays striking the comb-like projection 10b are absorbed by that portion, but a slight amount of reflected light repeatedly undergoes multi-stage reflection between the comb-like projections 10b as shown in FIG. Eventually converted to heat.

  Further, a liquid-tight transparent sealing glass 11 is bonded to the side of the heat sink 10 where the comb-like projections 10b are formed. A liquid-tight space constituted by the heat sink 10 and the seal glass 11 is filled with an optical coupling liquid 12 (hereinafter referred to as an OC liquid). An injection plug 13 for injecting the OC liquid into the liquid tight space is installed in the heat sink 10. Although only one injection plug 13 is shown in FIG. 4, two injection plugs for OC liquid injection and air venting are actually installed. The OC liquid 12 is filled in the entire liquid-tight space so that there are no residual bubbles.

  As described above, when the reflected light is converted into heat and the temperature of the entire prism cooling device 9 rises, the temperature of the OC liquid 12 similarly rises, so that the volume expands. A device for absorbing and relaxing the volume expansion is incorporated in the injection plug 13. The injection plug 13 has a hollow shaft 13a, and a through-hole for injecting the OC liquid 12 or extracting the air is formed in the central portion of the hollow shaft 13a in the vertical direction. And the rubber cap 13b is covered so that the hollow shaft 13a may be covered. Further, a sealing cap 13c is screwed from above. A seal portion having a circular cross section formed at the base portion of the rubber cap 13b is sandwiched between both step portions formed on the hollow shaft 13a and the sealing cap 13c by screwing the sealing cap 13c. A liquid-tight seal is made. The expansion / contraction of the OC liquid 12 is absorbed by the elastic deformation of the rubber cap 13b.

  The prism cooling device 9 assembled as shown in FIG. 4 is bonded onto the color prism 3 with a highly transparent adhesive. In order to reduce reflection at the adhesive layer, it is necessary to use an adhesive having a refractive index as close as possible to that of the prism (refractive index Nd = 1.49).

As shown in FIG. 2, when the prism cooling device 9 is bonded and mounted, the unnecessary light Rn is transmitted through the adhesive layer → the seal glass 11 → the OC liquid 12 without being totally reflected by the prism upper surface 3 a and formed on the heat sink 10. The comb-like protrusion 10b is reached. The light beam that has reached the comb-like projection 10b is attenuated by the reflection path as described with reference to FIG. 5 and converted into heat. Note that the heat sink 10 may be blown and air-cooled when it becomes hot only by natural air cooling.
Japanese Patent No. 3065068

  In order to obtain a bright image when enlarged and projected, the light flux incident on the DMD has an extremely high energy density. The energy density of the projection light and the unnecessary light is the same. There is no problem because the projection light is enlarged and projected on the screen through the projection lens. However, the unnecessary light needs to be quickly taken out of the prism, introduced into the light absorber, converted into heat, and attenuated and extinguished.

  The conventional prism cooling apparatus that introduces unnecessary light and attenuates and extinguishes as shown in FIG. 4 uses a liquid as an optical coupling medium, and thus requires a transparent glass for sealing the liquid. Adhesive work for sealing the glass in a liquid-tight manner, installation of injection plugs, injection and filling of OC liquid, liquid leakage confirmation work, etc. are necessary. Conventional cooling devices take time to assemble and are expensive. Yes.

  In view of the above-described conventional problems, the present invention eliminates the use of a liquid as an optical coupling medium, and as a result, eliminates a liquid sealing operation that requires a complicated assembly process, thereby reducing the cost of the optical element with a simpler configuration. It is an object of the present invention to provide a cooling device and a video projector using the same.

  In order to solve the above-described problems, a first aspect of the present invention is a resin molding that has a metal-based heat dissipation body and a light transmitting property, and is combined and bonded to the heat dissipation body at the time of resin injection molding. An optical element cooling apparatus including a body.

  The second aspect of the present invention is the optical element cooling apparatus according to the first aspect of the present invention, wherein the heat dissipating body has a surface plated with black nickel.

  The third aspect of the present invention is the optical element cooling device according to the first aspect of the present invention, wherein the heat dissipating member has a plurality of comb-like uneven portions at a joint portion with the resin molded body.

  Further, the fourth aspect of the present invention is substantially the same as the angle of the incident light beam so that the tip of the convex portion of the joint portion of the heat radiating member with the resin molded body is substantially parallel to the incident light beam. It is a cooling device of the optical element of the 3rd present invention which has an inclination.

  According to a fifth aspect of the present invention, there is provided the optical element cooling device according to any one of the first to fourth aspects of the present invention, and the incident light is made to be in one of two different directions according to the incident light. A digital micromirror device that reflects light, a projection lens that projects incident light, and a prism that is installed between the digital micromirror device and the projection lens and is in close contact with the resin of the cooling device for the optical element. The resin molding has a refractive index similar to that of the prism, and the two different directions are a direction that passes through the prism and enters the projection lens, and a cooling device for the optical element of the prism is installed. It is a video projector that is in the direction that is being performed.

  According to the present invention, there is provided a cooling device for an optical element that has a simple structure and is inexpensive, eliminating the use of a conventional liquid as an optical coupling medium, eliminating a liquid sealing operation that requires a large number of assembly steps and checks. I can do it.

  Hereinafter, embodiments will be described with reference to the drawings.

(Embodiment 1)
FIG. 6 is a schematic configuration diagram of a video projector using the optical element cooling device according to the first embodiment. As shown in FIG. 6, the video projector using the optical element cooling apparatus according to the first embodiment includes a rectangular parallelepiped color prism 41 and triangular prism shaped color prisms 42 and 43. A micromirror 45 is provided on one surface of the rectangular prism shaped color prism 41. In addition, the projection lens 46 is installed against the surface of the color prism 41 opposite to the surface on which the micromirror 45 is installed. A prism 42 is installed between the projection lens 46 and the color prism 41 so that the side surface of the color prism 41 is parallel to the side surface.

  A prism 43 is installed on the prism 42 while maintaining a very thin parallel air layer 44 (5 to 10 microns) so that the triangular shape of the bottom surface thereof is turned upside down. In order to eliminate unnecessary light, a prism cooling device 47, which is an example of the optical element cooling device of the present invention, is installed on the side surface of the color prism 41 other than the micromirror 45 and the prism 42. Yes.

  Next, the configuration of the prism cooling device 47 will be described below.

  FIG. 7 is a configuration diagram of the prism cooling device according to the first embodiment. The prism cooling device 47 has a heat sink 48 which is an example of a heat radiator of the present invention made of a metal such as copper, copper alloy, iron-based alloy or aluminum. The heat sink 48 has a plurality of fins 48a for heat dissipation. A plurality of comb-like protrusions 48 b are formed in the bottom recess of the heat sink 48. Further, the surface of the heat sink 48 is colored black by applying black nickel plating or the like to enhance light absorption.

  A transparent plastic material 49, which is an example of the resin of the present invention, is integrated with the heat sink 48 made of metal using, for example, an insert molding method, which is one of the well-known plastic molding methods. Molded. Since the transparent plastic material 49 is formed using the heat sink 48 as a mold, the transparent plastic material 49 is also in close contact with the complicated comb-like protrusions 48b. Further, the flat portion 49a of the transparent plastic material 49 is finished to be a smooth surface so as to be closely adhered to the color prism 41 later.

  FIG. 8 is an enlarged view of a comb-like protrusion 48b portion of the prism cooling device 47. FIG. As shown in the figure, the tip of the comb-like protrusion 48b is inclined so as to be substantially parallel to the incident light Rn to the transparent plastic material 49.

  The prism cooling device 47 described above is installed on the side surface of the color prism 41. At this time, the prism cooling device 47 is closely bonded so that no air remains on the bonding surface.

  The operation of the video projector using the optical element cooling apparatus according to the first embodiment having the above configuration will be described below.

  First, in FIG. 6, a light beam that has entered from the J direction is totally reflected by the inclined surface 42 a of the prism 42 and travels in the L direction, and a light beam emitted from the right side surface 41 a of the color prism 41 is incident on the DMD micromirror 45. .

  Here, when the micro mirror 45 is in the left-tilt position (position m), the reflected light beam is reflected in the Rm direction. The light beam traveling in the Rm direction enters the prism 42 and reaches the inclined surface 42a. The light ray Rm is emitted from the inclined surface 42a, enters the prism 43 through the minute air layer 44, and further travels through the prism 43 (in FIG. 6, the air layer 44 is drawn at a large interval for easy viewing).

  Next, the light beam is refracted by the slope 42 a and further refracted by the slope 43 a of the prism 43. Since the prisms 42 and 43 are made of the same material, there is no change in the traveling direction of the light beam, but a very slight step is generated. However, the air layers 44 are spaced apart by a few microns, and the amount of step is very small, so it can be said that the air layer 44 is substantially straight. An antireflection film is applied to the slope 42a and the slope 43a.

  The light beam that has passed through the prism 43 enters the projection lens 46, and is enlarged and projected onto a screen (not shown) installed in front.

  Further, when the micro mirror 45 is in the right-tilt position (position n), the reflected light beam is reflected in the Rn direction. The unnecessary light Rn is not totally reflected on the upper surface of the color prism 41, and travels almost straight as it is and enters the transparent plastic material 49. Since the transparent plastic material 49 has a high light transmittance, the light does not attenuate inside thereof. The unnecessary light Rn strikes a comb-like protrusion 48b formed on the heat sink 48.

  Next, as shown in the above-described configuration, the tip of each comb-like protrusion 48b is formed with an inclined portion having substantially the same angle as the incident angle of the unwanted light. It strikes against the side surface of the comb-like projection 48b without colliding with each tip of 48b.

  The impinging unnecessary light Rn attenuates while undergoing multi-stage reflection as shown in FIG. Most of the light energy is absorbed in the first impact, but is reflected almost completely and converted into thermal energy.

  Further, since the transparent plastic material 49 has high heat insulating properties, the heat generated in the comb-like projections 48b is more quickly conducted to the heat dissipating fins 48a having better thermal conductivity than flowing to the color prism 41 side. Heat is dissipated. If the heat sink 48 is blown and air cooled, the color prism 41 can be cooled more efficiently.

  Next, a method for manufacturing the optical element cooling apparatus according to Embodiment 1 will be described below.

  As described above, the transparent plastic material 49 is integrally formed on the side of the heat sink 48 on which the comb-like projections 48b are formed by using, for example, an insert molding method which is one of known synthetic resin molding methods. Thereby, a cooling device which is a composite part in which a heat sink 48 made of metal and a transparent resin molded body are integrally bonded can be obtained.

  Here, when the strength of the combined integration by metal and plastic insert molding (or outsert molding) is insufficient, a chemical bonding layer is formed at the joint in order to make the strength stronger. It may be.

  In general, when a plastic and a metal are integrally combined by an insert molding method to be combined, a softened plastic material enters and solidifies on fine irregularities on the metal surface, and is bonded by an anchor effect or frictional force. Therefore, when a temperature cycle is applied to this, slight deviation and thermal stress are generated at the interface due to the difference in thermal expansion coefficient between metal and plastic, and peeling is gradually progressed due to repeated temperature rise and fall. A thin space layer is formed and the optical coupling force is reduced.

  As described above, if even a slight space layer is formed on the boundary surface between the heat sink 48 and the transparent plastic material 49 due to peeling, the reflectance of the light beam increases at that portion, and the reflected light that has become stray light causes the “Background Technology” section. However, various problems as described above occur.

  The energy density of light incident on the heat sink 48 is extremely high, and the temperature of the heat sink 48 increases as the light-to-heat conversion is efficiently performed. Therefore, even in a severe temperature rise and fall, the close contact state between the heat sink 48 and the transparent plastic material 49 must be ensured.

  For this reason, a known surface treatment is performed on the heat sink 48 in order to maintain the close contact between the heat sink 48 and the transparent plastic material 49 even under harsh temperature conditions, and the heat sink 48 and the transparent plastic material 49 are formed during insert molding. The material of the surface treatment layer may be chemically bonded with the substance as an intermediary.

The known surface treatment is, for example, an aqueous solution of triazine thiols represented by the general formula (Chemical Formula 1), or methyl alcohol, isopropyl alcohol, ethyl alcohol, acetone, toluene, ethyl cellosolve, dimethylformaldehyde, tetrahydrofuran, methyl ethyl ketone, benzene. In addition, a solution using an organic solvent such as ethyl acetate as a solvent is used as an electrodeposition solution, a metal is used as an anode, a platinum plate titanium plate or a carbon plate is used as a cathode, and this is 20 V or less, 0.1 mA / dm ² to This is a metal electrochemical surface treatment method characterized by low-frequency, high-speed treatment performed by passing a current of 10 mA / dm ² at 0 to 80 ° C. for 0.1 seconds to 10 minutes (reference document, Japanese Patent No. 1840482). .)

また、上記（化１）において、Ｒは−ＯＲ´、−ＳＲ´、−ＮＨＲ´、−Ｎ（Ｒ´）_２；Ｒ´はアルキル基、アルケニル基、フェニル基、フェニルアルキル基、アルキルフェニル基又はシクロアルキル基、またＭはＨ、Ｎａ、Ｌｉ、Ｋ、１／２Ｂａ、１／２Ｃａ、脂肪族一級、二級及び三級アミン類、４級アンモニウム塩などである。

In the above (Chemical Formula 1), R is —OR ′, —SR ′, —NHR ′, —N (R ′) ₂ ; R ′ is an alkyl group, an alkenyl group, a phenyl group, a phenylalkyl group, an alkylphenyl group. Or a cycloalkyl group, and M is H, Na, Li, K, 1 / 2Ba, 1 / 2Ca, aliphatic primary, secondary and tertiary amines, quaternary ammonium salts and the like.

  In addition, as this kind of the above-mentioned transparent plastic material, norbornene-based resins, for example, trade names “Arton F5023”, “Arton FX4726”, “Arton D4532” manufactured by JSR, and alicyclic polyolefin-based resins, There are resins having a polar group in the side chain.

  As the resin of the present invention, in the optical element cooling apparatus of the first embodiment, the plastic material 49 is injection-moulded into the heat sink 48, but a polymer elastomer such as a light-transmitting silicone rubber body is used. May be used as an injection molding material.

  As described above, by replacing the optical coupling medium of the prism cooling device shown in the conventional example, that is, the volume region occupied by the sealing glass and the liquid, with a transparent resin molded body having a high light transmittance, the sealing glass Therefore, an optical element cooling apparatus and a video projector using the cooling apparatus can be provided with a simpler structure and an inexpensive optical element.

  The optical element cooling apparatus according to the present invention has an effect that can be provided at a low cost with a simple configuration, and is useful as a video projector or the like.

The figure explaining the structure and operation | movement of a micromirror formed in a DMD device Schematic configuration diagram of a video projector equipped with a conventional prism cooling device The figure explaining the advancing path of unnecessary light when there is no prism cooling device in the conventional video projector Configuration of conventional prism cooling device Explanatory drawing showing the process of absorbing and extinguishing unnecessary light while reflecting multiple stages in a conventional prism cooling device 1 is a schematic configuration diagram of a video projector equipped with a cooling device for optical elements according to a first embodiment of the present invention. 1 is a configuration diagram of an optical element cooling device according to a first embodiment of the present invention. The figure which shows the process in which the unnecessary light is absorbed and extinguished in multistage reflection in the cooling device of the optical element in Embodiment 1 concerning this invention.

Explanation of symbols

1 DMD
2 Micromirror 3 Color prism 4, 5 Prism 6 Air layer 8 Projection lens 9 Prism cooling device 41 Color prism 42, 43 Prism 44 Air layer 45 Micromirror 46 Projection lens 47 Prism cooling device 48 Heat sink 48 a Fin 48 b Comb-like projection 49 Transparent plastic material 49a Plane portion L Incident light to DMD Rm Projection light Rn Unnecessary light R1, R2, R3, R4 Ray path of unnecessary light

Claims (5)

A heat sink composed mainly of metal,
A cooling device for an optical element, comprising: a light-transmitting resin molded body that is combined and bonded to the heat radiating body during resin injection molding.   The cooling device for an optical element according to claim 1, wherein the heat dissipating body has black nickel plating on a surface thereof.   The cooling device for an optical element according to claim 1, wherein the heat dissipating member has a plurality of comb-like uneven portions at a joint portion with the resin molding.   The tip of the convex portion of the joint portion between the heat radiating body and the resin molded body has an inclination substantially equal to the angle of the incident light beam so as to be substantially parallel to the incident light beam. The cooling device for an optical element according to the description. A cooling device for an optical element according to any one of claims 1 to 4,
A digital micromirror device that reflects the incident light in one of two different directions according to incident light; and
A projection lens for projecting incident light;
A prism which is installed between the digital micromirror device and the projection lens and is closely bonded to a resin molded body of the cooling device for the optical element;
The resin molded body has a refractive index approximating that of the prism,
The two different directions are a direction in which the prism passes through the prism and enters the projection lens, and a direction in which a cooling device for the optical element of the prism is installed.

Images