JP2014021459A - Image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively cool two optical elements oppositely arranged in an image projection device.SOLUTION: The image projection device includes: a first optical element 9 and a second optical element 8 each having a transmission surface through which the light from a light source transmits, whose transmission surfaces sandwich a space S so as to be arranged opposite each other; and a cooling structure including two air guide units 15, 17 which cause cooling air flowing by the rotation of cooling fans 14, 16 to flow into the space from both sides of a first direction along the transmission surfaces. The two air guide units are configured such that a flow amount of air going toward the transmission surface of the first optical element is larger than the flow amount of the air going toward the transmission surface of the second optical element after the air flowed into the space from both sides collide with each other.

Description

  The present invention relates to an image projection apparatus such as a liquid crystal projector, and more particularly to a cooling technique of an optical element disposed in the apparatus.

  In the image projection apparatus as described above, strong light is irradiated for a long time, the temperature of the optical element that absorbs the light rises, and the performance may deteriorate. In order to mitigate the temperature rise of the optical element, it is required to cool the optical element efficiently. In a conventional image projection apparatus, cooling air (cooling air) is passed through a space between two optical elements arranged so as to face each other in a laminar flow or a state close thereto, thereby allowing the two optical elements to pass through. Air cooling methods have been used.

  Generally, the heat transfer capability of laminar cooling air is low, and if the heat generation amount of the optical element increases as the brightness of the image projection device increases, a large cooling fan is used to increase the cooling air amount or the wind speed. It is necessary to increase the rotation speed of the cooling fan. However, an increase in the size of the cooling fan prevents a reduction in the size of the apparatus. Further, when the rotation speed of the cooling fan is increased, noise generated from the cooling fan increases.

  For this reason, recently, a method of actively generating turbulence by colliding cooling air from a plurality of directions with each other and cooling the optical element by utilizing the high heat transfer coefficient of the turbulence is used. ing. In Patent Document 1, turbulent flow is caused by colliding cooling air introduced from two directions orthogonal to each other in the space between the liquid crystal panel and the polarizing plate in the direction along the surfaces of the panel and the polarizing plate. An image projection apparatus that cools the liquid crystal panel and the polarizing plate by generating the liquid crystal panel is disclosed. In Patent Document 2, two cooling winds having different wind velocity vectors are introduced into the space between the liquid crystal panel and the polarizing plate from both sides in the direction along the surface of the panel and the polarizing plate. An image projection apparatus is disclosed. In this apparatus, the two cooling airs collide with each other to generate a swirling flow of cooling air that is perpendicular to the surfaces of the liquid crystal panel and the polarizing plate, thereby performing highly efficient cooling.

JP 2000-140773 A JP 2008-107387 A

  In many image projection apparatuses, there is a difference in the amount of heat generated between two optical elements arranged to face each other. For example, in a liquid crystal panel and a polarizing plate on which light emitted from the liquid crystal panel is incident, the amount of heat generated is larger in the liquid crystal panel.

  However, in the image projection apparatuses disclosed in Patent Documents 1 and 2, the amount of cooling air blown to the optical elements facing each other is the same. In other words, in order to cool the optical element with a large amount of heat generation to a target temperature, a cooling air amount more than necessary is blown to the optical element with a small amount of heat generation. For this reason, the size and the number of rotations of the cooling fan are higher than the size and the number of rotations originally required for cooling those optical elements, and the generated noise increases.

  The present invention provides an image projection apparatus that efficiently cools each of two optical elements arranged so as to face each other with an appropriate amount of cooling air so that the cooling fan can be downsized and the number of rotations and noise can be reduced. provide.

  An image projection apparatus according to an aspect of the present invention includes a first optical element and a second optical element, each having a transmissive surface through which light from a light source is transmitted, the transmissive surfaces facing each other across a space. And a cooling structure including two air guide portions that allow cooling air flowing by rotation of the cooling fan to flow into the space from both sides in the first direction along the transmission surface. Then, after the air flowing into the space from the both sides collides with each other, the two air guide portions cause the air flow rate toward the transmission surface of the first optical element to flow toward the transmission surface of the second optical element. It is comprised so that it may become larger than the flow volume of this air which goes.

  According to the present invention, the flow rates of air that collide with each other in the space and go to the transmission surfaces of the first and second optical elements can be made different from each other (one more than the other). For this reason, each of the first and second optical elements can be efficiently cooled by an appropriate air flow rate. As a result, the cooling fan can be reduced in size and the number of rotations and noise can be reduced, and the image projection apparatus can be reduced in size and noise.

1 is a diagram showing a cooling structure provided in a liquid crystal projector that is Embodiment 1 of the present invention. FIG. FIG. 3 is a view in the α direction of the cooling structure in the first embodiment. FIG. 6 is a diagram showing a modification of the cooling structure in the first embodiment. FIG. 3 is a cross-sectional view illustrating an optical configuration of the liquid crystal projector according to the first embodiment. FIG. 5 is a diagram showing a cooling structure provided in a liquid crystal projector that is Embodiment 2 of the present invention. FIG. 10 is a diagram showing a modification of the cooling structure in the second embodiment. The figure which shows the simulation calculation result of the airflow in the cooling structure in Example 2. FIG. FIG. 10 is a diagram illustrating another modification of the cooling structure according to the second embodiment. FIG. 6 is a diagram showing a cooling structure provided in a liquid crystal projector that is Embodiment 3 of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, FIG. 4 shows an optical configuration of a liquid crystal projector as an image projection apparatus that is Embodiment 1 of the present invention. Reference numeral 1 denotes a light source (lamp) that emits white light. Reference numeral 13 denotes a projection lens (projection optical system). White light emitted from the light source 1 is decomposed into three color lights of red (R), green (G), and blue (B) by a color separation / synthesis optical system to be described later, according to an image signal input to the projector. Each color light is modulated (image modulation) by the liquid crystal panel. The modulated red light, green light, and blue light are synthesized again by the color separation / synthesis optical system, and a color image formed by the synthesized light is enlarged to a projection surface such as a screen via the projection lens 13. Projected. Between the light source 1 and the color separation / synthesis optical system, there is a polarization conversion element 101 that converts non-polarized light emitted from the light source 1 into linearly polarized light having a specific polarization direction (P-polarized light in this embodiment). Has been placed.

  In the color separation / synthesis optical system, reference numeral 2 denotes a dichroic mirror that reflects blue light and red light and transmits green light to separate them. Reference numeral 3 denotes an incident side polarizing plate for G, which is manufactured by attaching a polarizing element to a transparent substrate. The incident-side polarizing plate 3 for G transmits only P-polarized light. Reference numeral 4 denotes a first polarization beam splitter, which has a polarization separation surface that transmits P-polarized light and reflects S-polarized light.

  Reference numerals 5R, 5G, and 5B respectively denote a reflective liquid crystal panel for red, a reflective liquid crystal panel for green, and a reflective liquid crystal panel for blue that reflect incident light and modulate the image. 6R, 6G, and 6B are a quarter wavelength plate for red, a quarter wavelength plate for green, and a quarter wavelength plate for blue, respectively. A trimming filter 7 returns orange light to the light source side in order to increase the color purity of R. Reference numeral 8 denotes an incident-side polarizing plate for RB, which is manufactured by attaching a polarizing element to a transparent substrate and transmits only P-polarized light.

  Reference numeral 9 denotes a color selective phase difference plate that rotates the polarization direction of red light by 90 degrees and does not convert the polarization direction of blue light. Reference numeral 10 denotes a second polarization beam splitter, which has a polarization separation surface that transmits P-polarized light and reflects S-polarized light. Reference numeral 11B denotes an exit side polarizing plate for B, which performs blue light (S-polarized light) analysis. 11G is an exit side polarizing plate for G, and performs analysis of green light (S-polarized light). A dichroic prism 12 transmits red light and blue light and reflects green light so that they are combined and made incident on the projection lens 13.

  In such an optical configuration, white non-polarized light from the light source 1 is converted into P-polarized light by the polarization conversion element 101 and enters the dichroic mirror 2. The red light and blue light reflected by the dichroic mirror 2 are transmitted through the incident side polarizing plate 8 and incident on the color selective phase difference plate 9 after the orange light component is cut by the trimming filter 7. As described above, the color-selective retardation plate 9 rotates the polarization direction of red light by 90 degrees to form S-polarized light, and emits blue light as P-polarized light. The red S-polarized light and the blue P-polarized light are incident on the second polarizing beam splitter 10.

  The red S-polarized light is reflected by the polarization separation surface of the second polarizing beam splitter 10, passes through the quarter-wave plate 6R, and then enters the red reflective liquid crystal panel 5R. The blue P-polarized light passes through the polarization separation surface of the second polarizing beam splitter 10, passes through the quarter-wave plate 6B, and then enters the blue reflective liquid crystal panel 5B.

  The reflective liquid crystal panel 5R modulates and reflects the incident red light. The image-modulated red light passes through the quarter-wave plate 6R again and then reenters the second polarization beam splitter 10. Of the red light re-entering the second polarizing beam splitter 10, the S-polarized component is reflected again by the polarization separation surface of the second polarizing beam splitter 10, returned to the light source side, and removed from the projection light. . Further, the P-polarized component of the red light re-entering the second polarization beam splitter 10 passes through the polarization separation surface of the second polarization beam splitter 10 and travels toward the dichroic prism 12 as projection light.

  The reflective liquid crystal panel 5B modulates and reflects the incident blue light. The image-modulated blue light passes through the quarter-wave plate 6B again and then reenters the second polarizing beam splitter 10. The P-polarized component of the blue light re-entering the second polarization beam splitter 10 is transmitted again through the polarization separation surface of the second polarization beam splitter 10 and returned to the light source side to be removed from the projection light. . Further, the S-polarized component of the blue light re-entering the second polarization beam splitter 10 is reflected by the polarization separation surface of the second polarization beam splitter 10 and travels toward the dichroic prism 12 as projection light.

  On the other hand, the green light (P-polarized light) transmitted through the dichroic mirror 2 passes through the incident-side polarizing plate 3, passes through the polarization separation surface of the first polarizing beam splitter 4, and then passes through the quarter wavelength plate 6G. , Enters the green reflective liquid crystal panel 5G. The reflective liquid crystal panel 5G modulates the incident green light and reflects it. The image-modulated green light passes through the quarter-wave plate 6G again and then reenters the first polarization beam splitter 4. The P-polarized component of the green light re-entering the first polarization beam splitter 4 is transmitted again through the polarization separation surface of the first polarization beam splitter 4 and returned to the light source side to be removed from the projection light. In addition, the S-polarized component of the green light re-entering the first polarization beam splitter 4 is reflected by the polarization separation surface of the first polarization beam splitter 4 and travels toward the dichroic prism 12 as projection light.

  The dichroic prism 12 transmits blue light and red light, reflects green light, combines them, and directs them toward the projection lens 13. The projection lens 13 displays a color image by enlarging and projecting the synthesized light onto the projection surface.

  Next, the cooling structure of the optical element provided in the liquid crystal projector of this embodiment will be described with reference to FIGS. Here, as two optical elements to be cooled, an incident side polarizing plate 8 and a color selective phase difference plate 9 provided in the optical paths of red light and blue light will be described as an example. However, the cooling structure similarly configured can also be used for two other optical elements arranged opposite to each other. FIG. 1 shows an incident side polarizing plate 8 (hereinafter simply referred to as a polarizing plate), a color selective phase difference plate 9 (hereinafter simply referred to as a phase difference plate), and a cooling structure in a second direction (first direction) to be described later. It is the figure seen from the (perpendicular direction). FIG. 2 is a view of the cooling structure as viewed from a third direction α, which is a direction in which light is transmitted through the polarizing plate 8 and the phase difference plate 9. The retardation plate 9 corresponds to the first optical element, and the polarizing plate 8 corresponds to the second optical element.

  As shown in FIG. 1, the polarizing plate 8 and the retardation plate 9 include an emission surface (transmission surface) through which light emitted from the polarization plate 8 is transmitted and an incident surface (transmission surface) through which light incident on the retardation plate 9 is transmitted. Are arranged parallel to each other so as to face each other across the space S. In the following description, a direction parallel to the paper surface of FIG. 1 and along the exit surface of the polarizing plate 8 and the incident surface of the retardation plate 9, that is, a parallel direction (the left-right direction in FIG. 1) is referred to as a first direction. . In addition, the direction along the exit surface of the polarizing plate 8 and the incident surface of the phase difference plate 9 and orthogonal to the first direction (vertical direction in FIG. 2) is referred to as a second direction.

  In the present embodiment, the case where the first direction is the direction in which the long side of the image (the liquid crystal panels 5R and 5B) extends and the second direction is the direction in which the short side of the image extends is described. The second direction may be the direction in which the short side extends, and the second direction may be the direction in which the long side extends. Further, the first direction and the second direction are not necessarily parallel to the long side and the short side of the image, and may be directions inclined with respect to these.

  The cooling structure provided for the polarizing plate 8 and the retardation plate 9 is configured as follows. The cooling structure includes a first blower fan (cooling fan) 14, a first blower duct (air guide part) 15, a second blower fan (cooling fan) 16, and a second air duct (air guide part). ) 17 and the cover 20. As the first blower fan 14 and the second blower fan 16, various fans such as an axial fan and a sirocco fan can be used. The cover 20 shown in FIG. 2 covers the outer periphery of the space S between the polarizing plate 8 and the phase difference plate 9. However, on both sides of the cover 20 in the second direction, exhaust ports (exhaust portions) 20a for discharging air from the space S in the second direction are formed.

  The first and second air ducts 15 and 17, which are the two air guide portions, are directed toward the space S by the cooling air 18 and 19 flowing from the first and second air fans 14 and 16, respectively. Has an outflow outlet. These outlets are arranged on both sides of the space S in the first direction. That is, the first and second blower ducts 15 and 17 allow the air 18 and 19 flowing from the first and second blower fans 14 and 16 to rotate in the space S in the first direction. Has the role of flowing in from both sides.

  In the present embodiment, a case where air discharged from the first and second blower fans 14 and 16 is caused to flow into the space S via the first and second blower ducts 15 and 17 will be described. However, a cooling fan that sucks air from the space S may be used to apply a flow to the air so that the air flows from the outside of the space S through the air guide.

  Here, in FIG. 1, the flow of the first and second air ducts 15 and 17 in the third direction described above, in other words, the direction in which the exit surface of the polarizing plate 8 and the incident surface of the phase difference plate 9 face each other. The widths w1 and w2 of the outlets (air blowing surfaces) are narrower than the width W of the space S. Similarly, in the third direction, the centers A and B of the outlets of the first and second air ducts 15 and 17 are closer to the polarizing plate 8 than the center C of the space S, in other words, the center C It is arranged eccentrically with respect to. In addition, the widths w1 and w2 of the outlets of the first and second air ducts 15 and 17 may be the same or different from each other. Moreover, as shown in FIG. 2, the heights h1 and h2 in the second direction of the outlets of the first and second air ducts 15 and 17 may be narrower than the height H of the space S, It may be the same.

  In the cooling structure thus configured, when the first blower fan 14a rotates, the air 18 discharged from the first blower fan 14 passes through the first blower duct 15 and is polarized from the outlet. It flows into the space S between the plate 8 and the phase difference plate 9. At the same time, when the second blower fan 16 rotates, the air 19 discharged from the second blower fan 16 passes through the second blower duct 17 and flows into the space S from the outlet. As described above, since the outlet of the first air duct 15 and the outlet of the second air duct 17 are arranged on both sides of the space S in the first direction, the air 18 and the air 19 are in the space S. Collide with each other. In the vicinity of the position where this collision occurs, the air pressure increases.

  In this embodiment, the centers A and B of the outlets of the first and second air ducts 15 and 17 are eccentric with respect to the center C of the space S in the third direction. For this reason, a pressure difference arises between the collision position of the airs 18 and 19 in the space S, and the space part on the polarizing plate 8 side and the space part on the retardation plate 9 side from the collision position. Therefore, the air in the space S after the collision is divided into the air toward the polarizing plate 8 and the air toward the phase difference plate 9 in the third direction, and the exit surface of the polarizing plate 8 and the incidence of the phase difference plate 9 respectively. The polarizing plate 8 and the retardation plate 9 are cooled by hitting the surface. The air thus cooled in the polarizing plate 8 and the retardation plate 9 flows toward the exhaust port 20a and is exhausted out of the space S as shown in FIG.

  Here, in the third direction, if the widths of the outlets of the first and second air ducts 15 and 17 are set wider than the width W interval of the space S, the air flowing into the space S therefrom Even if 18 and 19 collide with each other, a pressure difference in the third direction is unlikely to occur. In this case, the air after the collision flows (exhaust) toward the exhaust port 20a without being divided in the third direction.

  In the present embodiment, the centers A and B of the outlets of the first and second blower ducts 15 and 17 are eccentric to the polarizing plate 8 side with respect to the center C of the space S. That is, in the third direction, the space portion on the polarizing plate 8 side and the space portion on the phase difference plate 9 side are asymmetrical with respect to the collision position of the airs 18 and 19 in the space S. More specifically, in the third direction, the width of the space portion on the phase difference plate 9 side is wider than the width of the space portion on the polarizing plate 8 side. For this reason, the air pressure in the space portion on the phase difference plate 9 side is lower than the air pressure in the space portion on the polarizing plate 8 side. As a result, the flow rate of air flowing toward the phase difference plate 9 in the air after the collision becomes larger than the flow rate of air flowing toward the polarizing plate 8.

  In general, a color-selective retardation plate is easier to absorb light and has a higher temperature than a polarizing plate. That is, the color-selective phase difference plate is more likely to cause problems such as performance deterioration due to temperature rise than the polarizing plate. In addition, the allowable temperature of the color selective phase difference plate is often lower than the allowable temperature of the polarizing plate. Therefore, as in the present embodiment, the flow rate of air toward the polarizing plate 8 is suppressed, and the flow rate of air toward the retardation plate 9 is increased to further increase the cooling efficiency of the retardation plate 9. And appropriate cooling can be performed for each of the phase difference plate 9. Thereby, compared with the case where the flow volume of the air which goes to the polarizing plate 8 is made the same as the flow volume of the air which goes to the phase difference plate 9, a required flow volume can be decreased as a whole. For this reason, the size of the 1st and 2nd ventilation fans 14 and 16 can be reduced in size, or the number of rotations can be suppressed and noise can be reduced.

  The eccentric amount D of the centers A and B of the outlets of the first and second air ducts 15 and 17 with respect to the center C of the space S is determined by the temperature of the phase difference plate 9 and the polarizing plate 8 in a state where light is incident. What is necessary is just to set so that it may become each target temperature.

  The exhaust port 20a may be formed only on one side in the second direction of the cover 20, as shown as a modification in FIG. In this configuration, air hitting the polarizing plate 8 and the retardation plate 9 at a position away from the exhaust port 20a continues to contact the polarizing plate 8 and the retardation plate 9 while flowing toward the exhaust port 20a. Remove more heat from these. For this reason, cooling efficiency can be increased more.

  In this embodiment, the widths w1 and w2 of the outlets of the first and second air ducts 15 and 17 are made narrower than the width W of the space S, and the centers A and B of the outlets are the centers C of the space S. The case of decentering with respect to was explained. However, the width of the outlets of the first and second air ducts 15 and 17 is not necessarily narrower than the width of the space S. For example, the width of the outlet of the first and second air ducts 15 and 17 is the same as the width of the space, and the center of the opening area of the outlet is on the polarizing plate 8 side with respect to the center C of the space S. It may be formed in a non-rotationally symmetric shape that is eccentric.

  FIG. 5 shows a cooling structure of a liquid crystal projector that is Embodiment 2 of the present invention. In this embodiment, elements common to the first embodiment and elements having the same functions are denoted by the same reference numerals as those in the first embodiment.

  In Example 1 shown in FIG. 1, the outer peripheral surfaces around the outlets of the first and second air ducts 15 and 17 that are eccentric with respect to the center C of the space S in the third direction are from the polarizing plate 8. The case where they are spaced apart has been described. On the other hand, in the present embodiment, in the third direction, the outer peripheral surfaces around the outlets of the first and second air ducts 15 and 17 are arranged at positions where they contact or approach the polarizing plate 8. . Thereby, the eccentricity D with respect to the center S of the space S of the centers A and B of the outlets of the first and second air ducts 15 and 17 is maximized.

  Here, “the outer peripheral surfaces of the first and second air ducts 15 and 17 are in contact with or close to the polarizing plate 8” means that the outer peripheral surface is an optical portion of the polarizing plate 8 (the exit surface thereof). It does not mean that it is in contact with or close to an effective area. That is, it means that the outer peripheral surfaces of the first and second blower ducts 15 a and 17 a are in contact with or close to a region outside the effective region of the polarizing plate 8. In consideration of the assembling property of the cooling structure, the outer peripheral surfaces around the outlets of the first and second air ducts 15 and 17 are connected from the polarizing plate 8 to the polarizing plate as shown in FIG. You may leave | separate to the direction (1st direction) which extended the 8 injection | emission surface.

  Furthermore, as shown in FIG. 8 as a modified example, the outer peripheral surfaces of the first and second air ducts 15 and 17 are in contact with or close to the holding member 21 that holds the polarizing plate 8 (and the retardation plate 9). You may do it.

  Also in the present embodiment, as in the first embodiment, the air 18, 19 flows into the space S from both sides of the space S in the first direction through the outlets of the first and second air ducts 15a, 17ab, and After the collision, it flows separately on the polarizing plate 8 side and the phase difference plate 9 side. However, since the first and second air ducts 15 and 17 are in contact with or close to the polarizing plate 8 as described above, the space portion on the polarizing plate 8 side and the phase difference plate 9 from the collision position of the air 18 and 19. The air pressure difference from the side space portion is larger (largest) than in the first embodiment. Therefore, the flow rate of air toward the polarizing plate 8 after the collision is minimized, and the flow rate of air toward the retardation plate 9 is maximized.

  According to the present embodiment, it is possible to perform appropriate cooling on each of the polarizing plate 8 and the retardation plate 9 as in the first embodiment, and in particular, the polarizing plate 8 has high heat resistance (for example, a wire grid). When the reflective polarizing plate is used, the retardation plate 9 can be cooled more efficiently.

  In FIG. 7, the simulation result of the flow of the air in the cooling structure of a present Example is shown. In this simulation, the two flat plates 8 ′ and 9 ′ corresponding to the polarizing plate 8 and the retardation plate 9 are disposed so as to face each other with the space S interposed therebetween. The air inlets 18 and 19 corresponding to the outlets of the first and second air ducts 15 and 17 are brought into contact with the flat plate 8 ′ on both sides of the space S in the first direction ( That is, it is provided so that the eccentric amount D is maximized). Although not shown, exhaust ports are provided on both sides in the second direction, which is a direction perpendicular to the paper surface of FIG.

  As can be seen from FIG. 7, the air 18 and 19 flowing into the space S from both sides of the space S collides with each other in the third direction toward the two flat plates 8 ′ and 9 ′. It flowed. At this time, the flow rate of air (indicated by hatching arrows) flowing toward the flat plate 9 'was greater than that of air flowing toward the flat plate 8' (indicated by solid black arrows). In Example 1, it is considered that a similar simulation result can be obtained although the difference in the flow rate of the air flowing toward the flat plates 8 ′ and 9 ′ is smaller than the simulation result of FIG.

  FIG. 9 shows a cooling structure for a liquid crystal projector that is Embodiment 3 of the present invention. In this embodiment, elements common to the first embodiment and elements having the same functions are denoted by the same reference numerals as those in the first embodiment.

  In Examples 1 and 2, two blower fans (first and second blower fans 14 and 16) are used, and separate blower ducts (first and second blower ducts 15 and 17) from each blower fan. In the above description, the airs 18 and 19 are introduced from both sides of the space S. In contrast, in the present embodiment, only one blower fan 23 is used, and the air discharged from the blower fan 23 is sent to one blower duct 22 and the first and second blowers that are piped so as to branch therefrom. Air 18 and 19 is introduced from both sides of the space S through the ducts 15 and 17. As the blower fan 23, an axial fan, a sirocco fan, or the like can be used as in the first and second embodiments. After the airs 18 and 19 that have flowed into the space S collide with each other, the flow rate of the air flowing toward the polarizing plate 8 is the point where the air flows toward the polarizing plate 8 and the phase difference plate 9. More points are the same as in the first and second embodiments.

  According to the present embodiment, compared with the first and second embodiments, the number of blower fans can be reduced, and mounting on a smaller liquid crystal projector can be realized.

  As described above, according to each of the above embodiments, the flow rate of one of the airs that collide with each other in the space and go to the transmission surfaces of the first and second optical elements is made larger than the flow rate of the other. Can do. For this reason, each of the first and second optical elements can be efficiently cooled by an appropriate air flow rate. As a result, the cooling fan can be reduced in size and the number of rotations and noise can be reduced, and the image projection apparatus can be reduced in size and noise.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  An image projection apparatus such as a small and low-noise liquid crystal projector can be provided.

8 Incident-side polarizing plate 9 Color selective phase difference plate 14, 16 Blower fan S Space

Claims (4)

An image projection apparatus that projects an image using light from a light source,
A first optical element and a second optical element, each having a transmission surface through which the light is transmitted, the transmission surfaces being arranged to face each other across a space;
A cooling structure including two air guide portions for allowing cooling air flowing by rotation of a cooling fan to flow into the space from both sides in the first direction along the transmission surface;
The two air guide portions are configured such that, after the air flowing into the space from both sides collides with each other, the flow rate of the air toward the transmission surface of the first optical element is the second optical element. An image projection apparatus configured to be larger than a flow rate of the air toward the transmission surface. In the direction in which the transmission surfaces of the first and second optical elements face each other,
The width of the outlet from which the air in the two air guide portions flows out toward the space is narrower than the width of the space, and the center of the outlet is closer to the second optical element than the center of the space. The image projection apparatus according to claim 1, wherein the image projection apparatus is disposed at a close position.   The said cooling structure has an exhaust part which discharges | emits the said air in the said space to the 2nd direction orthogonal to the said 1st direction along the said permeation | transmission surface. Or the image projection apparatus of 2. 4. The image projection apparatus according to claim 1, wherein an allowable temperature of the first optical element is lower than an allowable temperature of the second optical element. 5.