PROJECTION DISPLAY APPARATUS

A cooling device of a projection display apparatus includes a first heat receiving unit including an opening that is rectangular. The first heat receiving unit includes a flow path part that forms the opening. An image display element of the projection display apparatus includes a first front face located in front of a reflective image display, a second front face parallel to the first front face and located behind and outside the first front face, and a first side face located between the first front face and the second front face. The first front face is inserted into the opening, and the flow path part is in contact with the first side face and the second front face via a heat conductive member. The flow path part includes a front face that is flush with or in front of the first front face of the image display element.

BACKGROUND

1. Technical Field

The present disclosure relates to a projection display apparatus using an image display element, and more particularly to a configuration of a cooling device for an image display element.

2. Description of the Related Art

Conventionally, a reflective image display may be used as an image display element of a projection display apparatus. An example of the reflective image display is a digital mirror device (DMD). Since the DMD is made of an inorganic material and has high reliability, the DMD is also often used in ultrahigh-luminance projection image display elements. However, in order to maintain high reliability of the reflective image display such as the DMD, it is necessary to realize a temperature required in the image display element.

Cooling of the reflective image display is mainly performed by connecting a heat dissipating means such as a heat sink or a liquid cooling device to a back surface. In addition, a material having excellent thermal conductivity such as a copper plate, a connection of a heat pipe, or a liquid cooling device may be provided on a light incident side (front face side) of the reflective image display.

For example, Patent Literature (PTL) 1 and PTL 2 disclose a structure in which a refrigerant of air or liquid is caused to flow through a gap between a prism and a DMD to cool the DMD.

SUMMARY

However, the cooling on the light incident side of the reflective image display cannot achieve sufficient cooling performance because a distance to an optical member, for example, a prism, disposed on a front face of the reflective image display is short. In the structure of PTL 1, dust cannot be prevented from adhering to an optical path effective area of an image display, and heat conduction efficiency is limited when a refrigerant is air, and thus the structure is limited to a projection display apparatus having a low light output.

In the structure of PTL 2, a pipe tube through which a refrigerant that is liquid flows is disposed between the image display and the prism that is a part of a projection optical system. Cooling efficiency is improved by using liquid as the refrigerant instead of air. However, it is required to increase a light amount from a light source in order to increase the luminance of a projected image, and it is necessary to improve the cooling efficiency of the image display.

An object of the present disclosure is to provide a projection display apparatus including a cooling device with improved cooling efficiency.

A projection display apparatus of the present disclosure includes: a light source unit that emits light; an image display element including a reflective image display that modulates the light from the light source unit according to an external signal; a cooling device that cools the image display element; and a projection lens unit that enlarges and projects an image generated by the light modulated by the image display element. The cooling device includes a first heat receiving unit including an opening that is rectangular, a pump that feeds a refrigerant that is liquid to the first heat receiving unit, and a heat dissipation part that dissipates heat received by the refrigerant. The first heat receiving unit includes a first inflow pipe into which the refrigerant flows, a first outflow pipe through which the refrigerant flows out, and a flow path part that forms the opening and connects the first inflow pipe and the first outflow pipe. The image display element includes a first front face located in front of the reflective image display, a second front face parallel to the first front face and located behind and outside the first front face, and a first side face located between the first front face and the second front face. The first front face of the image display element is inserted into the opening of the first heat receiving unit, the flow path part of the first heat receiving unit is in contact with the first side face and the second front face of the image display element via a heat conductive member, and the flow path part of the first heat receiving unit includes a front face that is flush with or in front of the first front face of the image display element.

The projection display apparatus of the present disclosure can provide a projection display apparatus including a cooling device with improved cooling efficiency.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments will be described in detail with reference to the drawings as appropriate. However, unnecessarily detailed description may be omitted. For example, the detailed description of already well-known matters and the overlap description of substantially the same configurations may be omitted. This is to avoid an unnecessarily redundant description below and to facilitate understanding by those skilled in the art.

Note that the inventors of the present disclosure provide the accompanying drawings and the following description for those skilled in the art to fully understand the present disclosure, and do not provide them to intend to limit the subject matter described in the scope of claims.

First Exemplary Embodiment

A first exemplary embodiment will be described below with reference toFIGS.1to5.

A schematic configuration of a projection display apparatus according to a first exemplary embodiment of the present disclosure will be described with reference toFIG.1.FIG.1is a configuration diagram of a projection display apparatus according to a first exemplary embodiment. For convenience of the following description, an XY orthogonal coordinate system illustrated in the drawing is assumed inFIG.1.

Projection display apparatus100includes light source unit101, light guide optical system LL, prism unit132, three image display elements138R,138G,138B (collectively referred to as image display element138), cooling device CL (seeFIG.5), and projection lens unit139. Light source unit101emits light, and light guide optical system LL guides the light from light source unit101to image display elements138R,138G,138B via prism unit132. Prism unit132separates light from light source unit101into blue light, red light, and green light, and guides the light to image display elements138R,138G,138B. Image display elements138R,138G,138B modulate the separated light from light source unit101according to an external signal. Cooling device CL cools image display elements138R,138G,138B. Projection lens unit139enlarges and projects an image generated by light modulated by image display elements138R,138G,138B.

Each of laser diode units101a,101bincludes a plurality of light sources, and each of the light sources includes a pair of, for example, blue laser diodes and a collimating lens disposed on an emission side thereof. As a result, the light source can emit laser light with suppressed spread.

Light emitted from laser diode unit101ais incident on mirror102having a partial opening. A part of the light incident on mirror102is emitted in a +X-direction through the partial opening of mirror102, and the remaining light is reflected by a reflector in a +Y-direction.

Light emitted from laser diode unit101bis also incident on mirror102. When the light is incident on mirror102, similarly, a part of the light passes through the partial opening of mirror102and is emitted in the +Y-direction, and the remaining light is reflected by the reflector in the +X-direction. Regarding ratios of the blue light to the light traveling in the +X-direction and to the light traveling in the +Y-direction among the emitted light from laser diode units101a,101b, the shape of the partial opening of mirror102is designed so that the ratio of the latter is high.

The blue light emitted in the +X-direction is condensed by lens103, reflected by mirror104, then condensed in the vicinity of diffuser plate105, and diffused by diffuser plate105. The diffused blue light enters condenser lens106, becomes collimated light, and enters dichroic mirror107. Dichroic mirror107has a characteristic of transmitting blue light and reflecting other color light. Therefore, the blue light incident on dichroic mirror107is transmitted through dichroic mirror107. The transmitted blue light passes through lens108, mirror109, and lens110, and is condensed on an incident surface of rod integrator111having a rectangular opening.

The light traveling in the +Y-direction via mirror102having a partial opening is converged by lens112and lens113constituting an afocal system with mirror114interposed therebetween and is incident on diffuser plate115. The blue laser light incident on diffuser plate115is diffused here, and then passes through dichroic mirror107to be incident on condenser lenses116,117. The blue light incident thereon is incident on phosphor part119of phosphor wheel device118.

Phosphor part119is, for example, a ceramic phosphor, and a reflection layer (not illustrated) that reflects light having a wavelength of fluorescent light is formed on a surface opposite to an incident surface of the excitation light. The reflection layer is fixed to spreader121having excellent thermal conductivity via an adhesive layer (not illustrated). Spreader121is a disk and is configured to be rotatable by motor122at the center.

The blue light incident on phosphor part119is converted into yellow light by entering phosphor part119, reflected by the reflection layer on a back surface, and emitted toward condenser lens117. The yellow light having passed through condenser lens117passes through condenser lens116and is incident on dichroic mirror107. Here, the yellow light is reflected and condensed on the incident surface of rod integrator111having a rectangular opening through lens108, mirror109, and lens110similarly to the blue light. Inside rod integrator111, the blue light of the laser light source and the yellow light of the fluorescent light are superimposed to generate white light.

As described above, light source unit101may have a configuration other than the above-described configuration as long as it is configured to emit white light.

Light guide optical system LL includes relay lenses123,124, mirror125, field lens126, and total reflection prism127.

The light emitted from rod integrator111passes through relay lenses123,124and is reflected by folding mirror125. The totally reflected light passes through field lens126and enters total reflection prism127. Total reflection prism127includes first prism128and second prism129, and is fixed while maintaining a slight gap (air gap) between first prism128and second prism129. The light incident on total reflection prism127is totally reflected by side face130of first prism128, passes through side face131of first prism128, and is incident on prism unit132.

Prism unit132is formed by bonding and fixing first prism134having blue-transmitting dichroic mirror face133having a characteristic of reflecting blue light, second prism136having green-transmitting dichroic mirror face135having a characteristic of reflecting red light and blue light, and third prism137. However, an air gap is provided between first prism134and second prism136in order to use total reflection.

Image display elements138R,138G,138B are disposed to face end surfaces of first prism134, second prism136, and third prism137, respectively. Image display element138includes reflective image display138a(seeFIG.3) in which a plurality of minute mirrors are two-dimensionally arranged. Inclination directions of the minute mirrors are controlled in two directions in accordance with an image signal from the outside. Reflected light from the mirror at a tilt angle at the time of an ON signal returns to prism unit132at an incident angle of 0 degree, and is incident on prism unit132again at a large angle at the time of an OFF signal.

Image display element138B is for blue light modulation, image display element138R is for red light modulation, and image display element138G is for green light modulation. At present, these image display elements in the market include device elements used as DMDs in projection display apparatuses.

In each pixel of image display elements138R,138G,138B, the image in a white display mode returns to prism unit132again, passes through first prism128and second prism129of total reflection prism127, enters projection lens unit139, and reaches a screen not illustrated in the drawing. Thus, color display is achieved.

[1-2. Configuration of Main Part]

Next, the configuration of the main part will be described with reference toFIG.2.FIG.2is a configuration diagram around prism unit132. InFIG.2, a second heat receiving unit is omitted for easy understanding of image display element138R. Furthermore, in the configuration around image display element138, a side of prism unit132is defined as the front, and an opposite direction thereof is defined as the rear.

Image display element138receives and reflects strong light from light source unit101, but generates heat due to light incident and absorbed between the micromirrors constituting reflective image display138aof image display element138and driving of image display element138itself. In order to ensure the reliability of image display element138, it is required to maintain a desired temperature. Therefore, as illustrated inFIG.3, first heat receiving unit141and second heat receiving unit140are provided.

A peripheral structure of image display element138will be described with reference toFIG.3.FIG.3is a peripheral configuration diagram of the image display element, and illustrates a peripheral structure of the image display element corresponding to one color light of three image display elements138R,138G,138B. Drive board142is connected to a controller (not illustrated), and receives an external signal corresponding to image content to be displayed from the controller. Drive board142and image display element138are electrically connected via socket143.

Image display element138is sandwiched and supported between fixing metal fitting144and metal fitting145. On a front side of image display element138, mask substrate146and heat insulating substrate147that transmit effective light incident on reflective image display138aare supported by mask substrate support metal fitting148, and first heat receiving unit141is disposed between image display element138and heat insulating substrate147. Mask substrate146absorbs stray light traveling in each of first to third prisms134,136,137.

Second heat receiving unit140is in contact with a back surface of image display element138via conductive grease by a pressing spring (not illustrated), and can receive driving heat of image display element138. First heat receiving unit141is thermally connected to an outer face part of protruding part138dprotruding forward of image display element138via sheet-like heat conductive member155(seeFIG.10A).

Next, the following description refers toFIG.4.FIG.4is a perspective view of the image display element. Image display element138has quadrangular cylindrical protruding part138dprotruding forward from base part138c. Protruding part138dhas opening138e, and a front face of reflective image display138adisposed on base part138cis exposed through opening138e. Protruding part138dhas a rectangular shape in a front view.

Next, the following description refers toFIG.5.FIG.5is a diagram illustrating connection of a liquid-cooled module of cooling device CL. First heat receiving unit141includes first inflow pipe152through which a refrigerant flows into first heat receiving unit141, and a first outflow pipe153through which the refrigerant flows out of first heat receiving unit141. Second heat receiving unit140includes second inflow pipe162through which the refrigerant flows into second heat receiving unit140, and second outflow pipe163through which the refrigerant flows out of second heat receiving unit140.

Second heat receiving unit140incorporates pump140a, and the refrigerant sent from second heat receiving unit140flows into first heat receiving unit141through second outflow pipe163, pipe191, and first inflow pipe152. The refrigerant flowing into first heat receiving unit141absorbs the heat of the front face of image display element138, and the temperature thereof rises. The refrigerant whose temperature has increased flows out of first heat receiving unit141, passes through first outflow pipe153and pipe192, and flows into radiator150as a heat dissipation part. The refrigerant is cooled by radiator150, and the cooled refrigerant passes through pipe193, reserve tank151, and pipe194and circulates to second heat receiving unit140again.

Next, a configuration of first heat receiving unit141will be described with reference toFIGS.6to9.FIG.6is a perspective view of first heat receiving unit141.FIG.7Ais a rear view of first heat receiving unit141.FIG.7Bis a side view of first heat receiving unit141.FIG.7Cis a front view of first heat receiving unit141.FIG.8is an eight-direction arrow view inFIG.7C.FIG.9is a cross-sectional view taken along line9-9inFIG.7C.

First inflow pipe152is connected to or near one of the four corners of flow path part154. Flow path part154is formed along the shape of the front face of image display element138. Flow path part154has, for example, opening179fitted into an outer face of protruding part138dof image display element138. Flow path part154branches in two directions from a connection point of first inflow pipe152, goes around image display element138, joins again, and reaches first outflow pipe153. The refrigerant flowing from first inflow pipe152flows out of first outflow pipe153through flow path part154, and reaches radiator150through the pipe.

First inflow pipe152and first outflow pipe153are connected so as to be positioned diagonally at the four corners of flow path part154. First inflow pipe152is connected by first joint157located at one corner of flow path part154. First outflow pipe153is connected by second joint161located at one corner of flow path part154.

Flow path part154includes first pipe173and second pipe174branching from first joint157. First pipe173and second pipe174merge at second joint161. First pipe173and second pipe174have the same length. That is, a distance from first inflow pipe152to first outflow pipe153in flow path part154is the same, and a flow rate of refrigerant Rg is branched in a well-balanced manner. Here, the same length of first pipe173and second pipe174does not have to be exactly the same length, and may be substantially the same length. As described above, since image display element138and flow path part154are thermally connected via heat conductive member155, heat of a front part of image display element138can be absorbed.

First heat receiving unit141includes opening179in a central part. Opening179is formed by first pipe173and second pipe174. Opening179has a shape larger than a distal end shape of protruding part138dof image display element138by about one, and has, for example, a rectangular shape.

In first heat receiving unit141, two corners of rectangular flow path part154, first inflow pipe152, and first outflow pipe153are brazed via first joint157and second joint161, respectively. First inflow pipe152is connected to first joint157by bending a round pipe, and first outflow pipe153is similarly connected to second joint161.

As illustrated inFIG.9, flow path part154(first inflow pipe152and first outflow pipe153) is formed by brazing upper and lower two thin metal plates175,176. At this time, for example, flow path part154can be formed by assembling metal plates175,176made of a clad material and passing the metal plates through a heating furnace. Flow path part154is made of, for example, an aluminum clad material.

As illustrated inFIGS.10A and10B, protruding part138dof image display element138has a stair shape at the outer part. Protruding part138dincludes first front face138da, second front face138dbformed one step below (rearward), and third front face138dcas a contact face formed one step further below (rearward). Second front face138dbis formed outside first front face138da, and third front face138dcis formed outside second front face138db. First front face138daand second front face138dbare connected to each other at first side face138ddas a rising wall part. Second front face138dband third front face138dcare connected by second side face138deas a rising wall part.

First side face138ddextends rearward from an outer end of first front face138da. Second front face138dbextends parallel to first front face138daoutward from a rear end of first side face138dd. Second side face138deextends rearward from an outer end of second front face138db. Third front face138dcextends parallel to first front face138daoutward from a rear end of second side face138de. First front face138daand first side face138ddconstitute first step part138df, and second side face138deand third front face138dcconstitute second step part138dg.

Flow path part154of first heat receiving unit141is in contact with first side face138ddand second front face138dbof protruding part138dvia heat conductive member155. As a result, even when stray light that has not been absorbed by mask substrate146is applied to protruding part138dand the front face of reflective image display138a, heat due to the irradiation can be transmitted to flow path part154via heat conductive member155.

Front face175cof flow path part154of first heat receiving unit141is located on the same face as first front face138daof protruding part138dor in front of first front face138da, that is, so as to be convex in a traveling direction of the modulated light. As a result, even when bending R is required at a corner between front face175cof flow path part154and inner wall part181in processing of metal plate175, a contact area with first side face138ddcan be sufficiently secured.

In order to simplify the processing of upper and lower metal plates175,176, a part facing first side face138ddof protruding part138dof image display element138is formed in each of metal plate175and metal plate176, and these facing parts are brazed to each other as first brazed faces175a,176a. Furthermore, a part extending to an outer periphery of flow path part154is formed in each of metal plate175and metal plate176in a direction perpendicular to first side face138dd, and these extending parts are brazed to each other as second brazed faces175b,176b, respectively.

A face of metal plate175opposite to first brazed face175aconstitutes inner wall part181of flow path part154. Therefore, respective first brazed faces175a,176ato be brazed of two metal plates175,176are parallel to inner wall part181forming opening179.

In flow path part154, the heat resistance between image display element138and refrigerant Rg can be further reduced as the thickness of the part facing first side face138ddof image display element138is thinner. However, flow path part154can be easily created by brazing on each of first brazed faces175a,176afacing first side face138dd.

Furthermore, as illustrated inFIG.8, first joint157has inclined face156that is a face intersecting with an inflow direction of the refrigerant in the internal structure indicated by a broken line. The refrigerant flowing into first joint157from first inflow pipe152through reserve tank151collides with inclined face156. As a result, even when air is mixed in the refrigerant, the air flows as fine bubbles due to the collision. As described above, since the air reservoir is less likely to occur in first joint157, the refrigerant is poured downstream without stagnation. Inclined face156is not limited to first joint157, and may be disposed at least before refrigerant Rg reaches flow path part154via first inflow pipe152.

Since first joint157and second joint161are respectively interposed in the connections between flow path part154and first inflow pipe152and first outflow pipe153, in order to store the inflow pipe and the outflow pipe in a space where they can be disposed, first inflow pipe152and first outflow pipe153can be connected to flow path part154without forming small bend R at the roots thereof.

As illustrated inFIGS.3and4, in image display element138, one face of the stepped plane part of protruding part138dis third front face138dc, and third front face138dcis in contact with claw part159of fixing metal fitting144. First inflow pipe152and first outflow pipe153extend between prism unit132disposed facing image display element138and image display element138, and are connected to another cooling module.

First heat receiving unit141is disposed closer to fixing metal fitting144than a space formed by fixing metal fitting144and prism unit132, and first inflow pipe152and first outflow pipe153are eccentrically disposed closer to the prism than flow path part154, so that first inflow pipe152and first outflow pipe153can be disposed even in a narrow space. This eccentricity can be achieved by bending the pipe as in the example ofFIG.11, or by eccentrically providing the inflow side and the outflow side at the joint part as inFIG.4.

Furthermore, as illustrated inFIGS.7C and8, first inflow pipe152and first outflow pipe153of first heat receiving unit141extend along a longitudinal direction of prisms134,136,137facing image display element138to an opposite side of the incident direction of the incident light on reflective image display138a.

A first modification example of first heat receiving unit141will be described with reference toFIG.11.FIG.11is a perspective view illustrating the first modification example of first heat receiving unit141. InFIG.11, when first inflow pipe152and first outflow pipe153can be bent by 90 degrees in the pipe connection between first inflow pipe152and first outflow pipe153and flow path part154, convex part160is provided at a root of flow path part154, and the refrigerant flowing into vertical wall part164collides with the refrigerant, so that it is possible to obtain an effect similar to that of above-described inclined face156(seeFIG.8). In this regard, inclined face156and vertical wall part164may be omitted as long as reserve tank151has a function of removing air mixed in the refrigerant. However, the presence of inclined face156and vertical wall part164is advantageous for balancing a flow rate of refrigerant Rg when flow path part154branches into two.

InFIG.9, flow path part154is formed of two sheets of sheet metal, but may be formed of sheet metal and a cut component. Processing cost can be reduced when flow path part154is formed of two sheet metals.

In the first exemplary embodiment, second heat receiving unit140includes pump140a. However, pump140amay be provided separately from second heat receiving unit140.

[2. Effects and Others]

As described above, projection display apparatus100according to the present exemplary embodiment includes light source unit101that emits light, image display element138that includes reflective image display138athat modulates the light from light source unit101according to an external signal, cooling device CL that cools image display element138, and projection lens unit139that enlarges and projects an image generated by the light modulated by image display element138. Cooling device CL includes first heat receiving unit141having rectangular opening179in a central part, pump140athat sends refrigerant Rg that is liquid to first heat receiving unit141, and radiator150that radiates heat received by refrigerant Rg. First heat receiving unit141includes first inflow pipe152into which refrigerant Rg flows from pump140a, first outflow pipe153from which refrigerant Rg flows out, and flow path part154forming opening179and connecting first inflow pipe152and first outflow pipe153. Image display element138has protruding part138dlocated outside reflective image display138a. Protruding part138dincludes first front face138dalocated in front of reflective image display138a, first side face138ddextending rearward from an outer end of first front face138da, and second front face138dbextending outward from a rear end of first side face138ddand parallel to first front face138da. Protruding part138dof image display element138is inserted into opening179of first heat receiving unit141, and flow path part154of first heat receiving unit141is in contact with first side face138ddand second front face138dbof protruding part138dvia heat conductive member155. Front face175cof flow path part154of first heat receiving unit141is located on the same face as first front face138daof protruding part138dor in front of first front face138da.

Since flow path part154of first heat receiving unit141comes into contact with first side face138ddand second front face138dbof protruding part138dof image display element138via heat conductive member155, it is possible to efficiently cool the light incident side of image display element138. Furthermore, front face175cof flow path part154of first heat receiving unit141is located on the same face as first front face138daof protruding part138dor in front of first front face138daof protruding part138d, and a contact area with first side face138ddcan be sufficiently secured even when bending R is required at a corner between front face175cof flow path part154and inner wall part181in processing of metal plate175.

Flow path part154of first heat receiving unit141has first pipe173and second pipe174which are branched from first inflow pipe152and joined at first outflow pipe153, first pipe173and second pipe174form different sides of rectangular opening179of first heat receiving unit141, and first pipe173and second pipe174have the same length. Since first pipe173and second pipe174have the same length, branched flow path part154can be uniformly cooled along opening179.

First inflow pipe152and first outflow pipe153of first heat receiving unit141extend along the longitudinal direction of each face of prisms134,136,137facing image display element138. As a result, the space of the front face cooling structure of image display element138can be saved.

First heat receiving unit141has inclined face156intersecting with the inflow direction of refrigerant Rg at least until refrigerant Rg reaches flow path part154via first inflow pipe152, and refrigerant Rg collides with intersecting inclined face156. Accordingly, even when refrigerant Rg contains air, the air flows as fine bubbles, so that clogging of refrigerant Rg can be prevented.

First inflow pipe152of the first heat receiving unit141and flow path part154are connected via first joint157, or first outflow pipe153of first heat receiving unit141and flow path part154are connected via second joint161.

Projection display apparatus100includes second heat receiving unit140that receives driving heat of image display element138, first heat receiving unit141is disposed between prism unit132and image display element138, and image display element138is disposed between first heat receiving unit141and second heat receiving unit140. Second heat receiving unit140includes second inflow pipe162into which refrigerant Rg flows and second outflow pipe163from which refrigerant Rg flows out.

Since image display element138is disposed between first heat receiving unit141and second heat receiving unit140and is cooled by each of first heat receiving unit141and second heat receiving unit140, both faces of the image display element138can be cooled, and cooling efficiency can be improved.

Second outflow pipe163and first inflow pipe152are connected in series such that refrigerant Rg flowing out of second outflow pipe163of second heat receiving unit140reaches first inflow pipe152of first heat receiving unit141. As a result, the cooling structure of image display element138can be saved in space.

Flow path part154of first heat receiving unit141includes two brazed metal plates175,176, and first brazed faces175a,176a, which are mating faces where two metal plates175,176are brazed, are parallel to inner wall part181of flow path part154forming opening179.

Flow path part154of first heat receiving unit141includes two brazed metal plates175,176, and second brazed faces175b,176b, which are mating faces where two metal plates175,176are brazed, extend from the outer periphery of flow path part154in a direction perpendicular to inner wall part181of flow path part154forming opening179.

Second Exemplary Embodiment

Projection display apparatus200according to a second exemplary embodiment projects a full-color image with a configuration different from the configuration of projection display apparatus100according to the first exemplary embodiment. Projection display apparatus200according to the second exemplary embodiment of the present disclosure will be described with reference toFIG.12.FIG.12is a schematic diagram illustrating a configuration of projection display apparatus200according to the second exemplary embodiment of the present disclosure. Note that projection display apparatus200according to the second exemplary embodiment and projection display apparatus100according to the first exemplary embodiment have the same configuration except for the points described below.

As illustrated inFIG.12, projection display apparatus200according to the second exemplary embodiment includes light source unit201that generates light, image generation unit202that converts the light into image light, and projection lens unit203that projects the image light onto a screen, for example.

In the case of the second exemplary embodiment, light source unit201includes, for example, light source lamp204that is a high-pressure mercury lamp and emits white diffused light. Furthermore, light source unit201includes a plurality of optical elements that guides light emitted from light source lamp204to image generation unit202. These optical elements will be described along with the propagation of light.

Diffused light emitted from light source lamp204is condensed on an incident surface of rod integrator206having a rectangular cross section by reflector205.

Color wheel207is disposed in front of an emission surface of rod integrator206. Color wheel207includes a red transmission filter that transmits only red light included in the white light from light source lamp204, a green transmission filter that transmits only green light, and a blue transmission filter that transmits only blue light. When color wheel207is rotated by motor208, the red transmission filter, the green transmission filter, and the blue transmission filter are sequentially and repeatedly disposed in front of the emission surface of rod integrator206. As a result, red light, green light, and blue light are sequentially and repeatedly emitted from color wheel207.

The light that has passed through color wheel207enters image generation unit202via lens209, lens210, lens211, mirror212, and lens213.

In the second exemplary embodiment, image generation unit202includes total reflection prism214and one image display element223.

In the second exemplary embodiment, total reflection prism214includes first prism215and second prism216. First prism215and second prism216are prisms having a substantially triangular prism shape, and are made of, for example, a glass material. Air gap217of several μm is formed between first prism215and second prism216.

First prism215includes side face218on which light Li from light source unit201is incident, side face219which reflects incident light Li, and side face220which transmits reflected light Li and faces image display element223.

Second prism216includes side face221forming air gap217by facing side face219of first prism215at an interval in parallel, and side face222facing projection lens unit203. Side face219of first prism215and side face221of second prism216are bonded to each other via an adhesive at a part other than the light transmitting part, for example, to form air gap217.

Image display element223includes a DMD as a reflective image display. Light, that is, red light, green light, and blue light are sequentially and repeatedly incident on image display element223from light source unit201through first prism215of total reflection prism214.

Furthermore, reflected light from image display element223, namely, image light Lp enters total reflection prism214, passes through air gap217(internal total reflection face), and is emitted from side face222of second prism216to projection lens unit203. Then, the image light is projected onto a screen by projection lens unit203.

Also in the second exemplary embodiment, similarly to the first exemplary embodiment described above, first heat receiving unit141A is provided around a front face of the DMD of image display element223.

FIG.13is a perspective view illustrating a peripheral structure of image display element223. As illustrated inFIG.13, image generation unit202includes prism case224, packing225, light shielding mask226, heat insulating material227, first heat receiving unit141A, drive board142A, socket143A, insulating sheet231, and presser metal fitting232.

Image display element223is disposed without a gap with respect to prism case224in which total reflection prism214is included and to which side face220is applied via packing225, light shielding mask226, and heat insulating material227, and first heat receiving unit141A similar to that of the first exemplary embodiment is connected to a periphery of the DMD of image display element223via a heat conductive member not illustrated in the drawing. On the other hand, image display element223is disposed on socket143A, drive board142A, insulating sheet231, and presser metal fitting232, and image display element223and drive board142A are electrically connected.

Although not illustrated inFIG.13, as illustrated inFIG.3, second heat receiving unit140of the first exemplary embodiment is disposed on a back surface of presser metal fitting232.

Similarly to the first exemplary embodiment, the liquid-cooled module can be connected in the second exemplary embodiment as illustrated inFIG.5, and a pump for circulating the refrigerant may be provided separately from the heat receiving unit on a back surface side.

Similarly to first heat receiving unit141of the first exemplary embodiment, first heat receiving unit141A has the configuration illustrated inFIGS.4and10, and can take heat from a front face of image display element223. Note that, in the second exemplary embodiment, since it is not necessary to provide image display element223for each color light, the degree of freedom in a drawing direction of first inflow pipe152A and first outflow pipe153A is high, and the necessity of alignment in the same direction is low. This is optimized in accordance with the peripheral structure, and is not restricted as a basic structure.

First heat receiving unit141A is also configured by brazing first inflow pipe152A and first outflow pipe153A formed by bending round pipes to both ends of flow path part154A. Flow path part154A is also formed by brazing two upper and lower thin plates, and flow path part154A is optimized in accordance with the dimensions of image display element223.

Here, image display element223is sandwiched between socket143A and prism case224, and is designed such that prism case224and third front face138dccontact each other. At this time, first heat receiving unit141A is included in prism case224, and first inflow pipe152A and first outflow pipe153A extend from side faces thereof. At that time, first inflow pipe152A and first outflow pipe153A only need to be at positions that do not interfere with socket143A, and unlike the first exemplary embodiment, there are few restrictions on the light input and output direction with respect to flow path part154A.

Even when the drawing direction and the eccentric position of first inflow pipe152A and first outflow pipe153A are different in the second exemplary embodiment, it is possible to similarly obtain the effect of enabling distribution to the flow paths in two directions and discharge of mixed air by forming inclined face156by providing a convex part at the root and causing the inflow refrigerant to collide. Also in the second exemplary embodiment, flow path part154A is formed of two metal plates, but may be formed of a sheet metal and a cut component.

Third Exemplary Embodiment

A projection display apparatus according to a third exemplary embodiment will be described with reference toFIGS.14to19. The projection display apparatus according to the third exemplary embodiment differs from projection display apparatus100according to the first exemplary embodiment mainly in configurations of an image display element, a first heat receiving unit, and a fixing metal fitting. The other configurations are similar to those of projection display apparatus100, and thus the same reference marks are used and detailed description thereof is omitted.FIG.14is a view illustrating an arrangement of image display element300, first heat receiving unit310, and fixing metal fitting324of the projection display apparatus according to the third exemplary embodiment,FIG.15is a perspective view of image display element300,FIG.16is a cross-sectional view of image display element300,FIG.17Ais a front view of first heat receiving unit310,FIG.17Bis a view of the first heat receiving unit inFIG.17Aas viewed in a direction of an arrow17B,FIG.18is a rear view of first heat receiving unit310, andFIG.19is a partially enlarged view illustrating an arrangement of image display element300and first heat receiving unit310.

As illustrated inFIGS.15and16, image display element300includes reflective image display301in which micromirrors that can be independently controlled from the outside are two-dimensionally arranged similarly to image display element138, ceramic base part302surrounding the reflective image display, terminal part303provided on a back surface electrically connected to a drive board, heat dissipation part304provided on the back surface, and front face glass306that seals the inside while transmitting incident light from a light source unit. Front face glass306is fixed to base part302by filling adhesive305between side face306band base part302.

Furthermore, base part302of image display element300has positioning holes307A,307B, a position in a direction parallel to front face302aof base part302is fixed by positioning holes307A,307B, and front face302ais pressed and fixed by pins327A,327B,327C provided on the fixing metal fitting324(seeFIG.14).

Note that terminal part303of image display element300is electrically connected to drive board142via a socket as in the case of image display element138. As in the case of projection display apparatus100, drive board142is connected to a controller, and receives an external signal corresponding to image content to be displayed from the controller.

Similarly to projection display apparatus100according to the first exemplary embodiment, second heat receiving unit140is brought into contact with heat dissipation part304of image display element300via conductive grease by a pressing spring (not illustrated), and can receive driving heat of image display element300.

As illustrated inFIGS.17A,17B, and18, first heat receiving unit310includes first inflow pipe311, first outflow pipe312, rectangular flow path part313, first joint315, and second joint316.

First inflow pipe311and first outflow pipe312are brazed and connected to two corners located diagonally of rectangular flow path part313or the vicinity thereof via first joint315and second joint316, respectively. First inflow pipe311and first outflow pipe312are connected to first joint315and second joint316, respectively, by bending a round pipe.

Flow path part313includes through holes326A,326B,328A,328B,328C penetrating first pipe317, second pipe318, and flow path part313.

First pipe317and second pipe318branch from first joint315and join together at second joint316to form rectangular flow path part313, and form rectangular opening314at the center. First pipe317and second pipe318have the same length. That is, a distance from first inflow pipe311to first outflow pipe312through first pipe317and a distance from first inflow pipe311to first outflow pipe312through second pipe318are the same, and a flow rate of refrigerant Rg is divided in a well-balanced manner. Here, “the lengths are the same” includes not only a case where the lengths are completely the same but also a case where the lengths are substantially the same.

Furthermore, first pipe317and second pipe318constituting flow path part313are constituted by upper and lower two thin metal plates (detailed configurations of the two metal plates are omitted inFIG.19) similarly to first pipe173and second pipe174constituting flow path part154of the first exemplary embodiment illustrated inFIG.9. Also in this case, for example, flow path part313can be formed by assembling a metal plate made of a clad material and passing the metal plate through a heating furnace. Flow path part313is made of, for example, an aluminum clad material.

Similarly to the cooling device of the first exemplary embodiment illustrated inFIG.5, the refrigerant flows into flow path part313from second heat receiving unit140through second outflow pipe163, pipe191, and first inflow pipe311. The refrigerant flowing into flow path part313absorbs the heat of the front face of image display element300, and the temperature rises. The refrigerant whose temperature has increased flows out of first outflow pipe312, passes through pipe192, and flows into radiator150as a heat dissipation part. The refrigerant is cooled by radiator150, passes through pipe193, reserve tank151, and pipe194, and circulates to second heat receiving unit140again.

As illustrated inFIG.17B, first joint315is provided with face356facing an inflow direction of refrigerant Rg, and inflow refrigerant Rg collides with face356. Accordingly, even when refrigerant Rg contains air, the air flows as fine bubbles, so that clogging of refrigerant Rg can be prevented. Face356is not limited to first joint315, and may be provided at least until refrigerant Rg reaches flow path part313via first inflow pipe311.

Rectangular opening314of flow path part313is formed in a shape larger than an outer shape of front face glass306of image display element300by about one along the outer shape of the front face glass, and is fitted into front face glass306.

Through holes326A,326B,328A,328B,328C provided in flow path part313are holes through which pins325A,325B,327A,327B,327C provided in fixing metal fitting324pass, respectively. Through holes326A,326B,328A,328B,328C penetrate flow path part313, and two metal plates are brazed to form wall surfaces of these through holes so that the refrigerant does not leak.

As illustrated inFIG.14, fixing metal fitting324includes pins325A,325B,327A,327B,327C. Pins325A,325B of fixing metal fitting324pass through through holes326A,326B provided in flow path part313of first heat receiving unit310, and are inserted into positioning holes307A,307B of image display element300, respectively. By inserting pins325A,325B into positioning holes307A,307B, respectively, the position in the direction parallel to front face302aof base part302of image display element300is fixed.

Pins327A,327B,327C of fixing metal fitting324pass through through holes328A,328B,328C provided in flow path part313of first heat receiving unit310, respectively, and are pressed against front face302aof image display element300. When pins327A,327B,327C are pressed against front face302aof image display element300, the position of image display element300in a front-rear direction (a traveling direction of the light modulated by reflective image display301) is fixed.

Next, a positional relationship between image display element300and first heat receiving unit310will be described. As illustrated inFIG.19, front face306aof front face glass306of image display element300is parallel to front face302aof base part302, and protrudes more in the traveling direction (forward) of the light modulated by reflective image display301than front face302a. Therefore, a part of side face306bof front face glass306is exposed forward from base part302. That is, image display element300has a structure in which front face306aof front face glass306is located in front of front face302aof base part302, and front face306aof front face glass306and front face302aof base part302are connected by side face306bof front face glass306.

A part of front face glass306protruding forward from base part302is fitted into opening314of first heat receiving unit310. At this time, side face306bof front face glass306is in contact with inner wall part313cof opening314of first heat receiving unit310, and front face302aof base part302is in contact with flow path part313(first pipe317, second pipe318) via sheet-like heat conductive member355. Refrigerant Rg supplied to first heat receiving unit310is divided into two directions of first pipe317and second pipe318of flow path part313, flows in front of front face302aof base part302of image display element300and around side face306bof front face glass306, and joins at first outflow pipe312. As a result, heat generated in image display element300by incidence of strong light from light source unit101can be transmitted to refrigerant Rg flowing through flow path part313.

Furthermore, as illustrated inFIG.19, in the first heat receiving unit310, front face313alocated on the front side is provided and plane part313bis provided on a side of opening314and on a side of image display element300with respect to front face313a. On plane part313bof first heat receiving unit310, light shielding mask glass321is disposed in parallel to front face glass306with an air interval in front of front face glass306of image display element300. By providing plane part313bonly in the periphery of opening314in this manner, light shielding mask glass321can be disposed close to an effective part of image display element300and can be configured to be small. As illustrated inFIG.19, flow path height d1of flow path part313between plane part313band image display element300is smaller than flow path height d2of flow path part313between front face313aof flow path part313and image display element300. However, since light shielding mask glass321becomes small, flow path part313having flow path height d2of a sufficient size can be secured on the outer peripheral side of plane part313b, and the flow of the entire refrigerant is smooth. Moreover, flow path part313having flow path height d3larger than flow path height d2is formed on the outer peripheral side of image display element300.

Furthermore, light shielding mask glass321includes light shielding region323that cuts light other than light incident on an effective part of reflective image display301of image display element300and light reflected and emitted. When light shielding region323absorbs light, the temperature becomes high. Therefore, it is preferable to provide a heat insulating member between plane part313bof first heat receiving unit310and light shielding mask glass321.

[2. Effects and Others]

As described above, the projection display apparatus according to the third exemplary embodiment includes: light source unit101that emits light; image display element300including reflective image display301that modulates the light from light source unit101according to an external signal; the cooling device that cools image display element300; and projection lens unit139that enlarges and projects an image generated by the light modulated by image display element300.

The cooling device includes first heat receiving unit310having rectangular opening314in a central part, pump140athat sends refrigerant Rg that is liquid to first heat receiving unit310, and radiator150that radiates heat received by refrigerant Rg. First heat receiving unit310includes first inflow pipe311into which refrigerant Rg flows from pump140a, first outflow pipe312from which refrigerant Rg flows out, and flow path part313forming opening314and connecting first inflow pipe311and first outflow pipe312.

Image display element300includes front face glass306having front face306a(first front face) located in front of reflective image display301, and base part302having front face302a(second front face) outside front face glass306. Front face302aof base part302is parallel to front face306aof front face glass306and is located behind and outside front face306aof front face glass306. Between front face306aof front face glass306and front face302aof base part302, a part of side face306b(first side face) of front face glass306is exposed from base part302.

Front face306aof front face glass306of image display element300is inserted into opening314of first heat receiving unit310, and flow path part313of first heat receiving unit310is in contact with side face306bof front face glass306exposed from base part302and front face302aof base part302via heat conductive member355. Front face313aof flow path part313of first heat receiving unit310is positioned in front of front face306aof front face glass306.

First heat receiving unit310has face356facing an inflow direction of refrigerant Rg at least until refrigerant Rg reaches flow path part313via first inflow pipe311, and refrigerant Rg collides with facing face356. Accordingly, even when refrigerant Rg contains air, the air flows as fine bubbles, so that clogging of refrigerant Rg can be prevented.

Flow path part313of first heat receiving unit310has plane part313bparallel to front face313a, and front face313ais located around plane part313band in the traveling direction of the modulated light compared to plane part313b. That is, in the vicinity of opening314of first heat receiving unit310, plane part313bparallel to front face313aof flow path part313and front face306aof front face glass306is provided between them. Light shielding mask glass321is disposed on plane part313b, and light shielding mask glass321is provided with light shielding region323for cutting light other than light incident on an effective part of image display element300and light reflected and emitted. However, plane part313bis not necessarily required as long as flow path height d2of flow path part313can be configured to be close to flow path height d1, and a support member for light shielding mask glass321may be separately provided on front face313aof flow path part313of first heat receiving unit310.

Flow path part313of first heat receiving unit310has a plurality of through holes326A,326B,328A,328B,328C penetrating in the traveling direction of the modulated light. By causing pins325A,325B,327A,327B,327C provided in fixing metal fitting324to pass through through holes326A,326B,328A,328B,328C, respectively, image display element300can be easily positioned.

Other Exemplary Embodiments

As described above, the above exemplary embodiments have been described as examples of the techniques disclosed in the present application. However, the techniques in the present disclosure are not limited to the above exemplary embodiments, and can also be applied to exemplary embodiments in which change, substitution, addition, omission, and the like are performed. Furthermore, a new exemplary embodiment can be made by combining the components described in the above exemplary embodiments.

In the first and third exemplary embodiments, light source unit101generates white light from the blue laser by laser diode unit101a, but the present invention is not limited thereto. White light may be generated by synthesizing light beams of respective colors from a red semiconductor laser, a blue semiconductor laser, and a green semiconductor laser, or a light source other than the laser such as a lamp may be used.

In the cooling device of the first to third exemplary embodiments, refrigerant Rg flows into the first heat receiving unit and the second heat receiving unit in series, but the present invention is not limited thereto. As in cooling device CL2of a second modification example illustrated inFIG.20, the first heat receiving unit and the second heat receiving unit may be configured such that refrigerant Rg flows in parallel.

In the first exemplary embodiment, projection display apparatus100includes prism unit132in which a plurality of prisms134,136,137each having a triangular prism or a quadrangular prism are directly bonded to each other through an optical thin coating or fixed while an air gap is maintained on an optical path between image display element138and projection lens unit139. Here, as in a third modification example illustrated inFIG.21, first inflow pipe152and first outflow pipe153of first heat receiving unit141may extend in parallel to a face of flow path part154, and may be connected to flow path part154so as to be eccentric (biased) to the incident side of the light to the corresponding prism of prism unit132with respect to a center of a rectangle formed by flow path part154. Since first inflow pipe152and first outflow pipe153are eccentrically connected to flow path part154on the light incident side to prism unit132, a path on the light incident side to prism unit132is shortened in flow path part154, and the cooling efficiency on the light incident side to prism unit132can be increased. The same applies to first inflow pipes152A,311and first outflow pipes153A,312of first heat receiving units141A,310of the second and third exemplary embodiments.

Furthermore, as in a fourth modification example illustrated inFIG.22, first inflow pipe152of first heat receiving unit141may be connected to flow path part154on a side of a part having a high light density of the corresponding prism of prism unit132, and first outflow pipe153may be connected to flow path part154on a side of a part having a low light density of the corresponding prism. Since first inflow pipe152of first heat receiving unit141is connected to flow path part154on the side of the part of the corresponding prism of prism unit132where the light density is high, refrigerant Rg can be caused to first flow into the side of protruding part138dwhere the temperature is high, so that the cooling efficiency can be improved. The same applies to first inflow pipes152A,311and first outflow pipes153A,312of first heat receiving units141A,310of the second and third exemplary embodiments.

As described above, the exemplary embodiments have been described to exemplify the techniques in the present disclosure. For that purpose, the accompanying drawings and the detailed description have been provided. Therefore, in order to illustrate the above techniques, the components illustrated in the accompanying drawings and described in the detailed description can include not only components essential for solving the problems but also components non-essential for solving the problems. Thus, it should not be immediately construed that those non-essential components are essential only based on the fact that those non-essential components are illustrated in the accompanying drawings or described in the detailed description.

The exemplary embodiments described above are intended to illustrate the technique in the present disclosure, and thus various changes, replacements, additions, eliminations, and the like may be made within the scope of claims and equivalents thereof.

Overview of Exemplary Embodiments

(1) A projection display apparatus of the present disclosure includes: a light source unit that emits light; an image display element including a reflective image display that modulates the light from the light source unit according to an external signal; a cooling device that cools the image display element; and a projection lens unit that enlarges and projects an image generated by the light modulated by the image display element. The cooling device includes a first heat receiving unit including an opening that is rectangular in a central part, a pump that feeds a refrigerant that is liquid to the first heat receiving unit, and a heat dissipation part that dissipates heat received by the refrigerant. The first heat receiving unit includes a first inflow pipe into which the refrigerant flows from the pump, a first outflow pipe through which the refrigerant flows out, and a flow path part that forms the opening and connects the first inflow pipe and the first outflow pipe. The image display element includes a protruding part protruding from a periphery of the reflective image display in a direction in which the modulated light travels on a side on which the light from the light source unit is incident. The protruding part includes a first front face on a side on which the light from the light source unit is incident, a first side face extending rearward from an outer end of the first front face, and a second front face parallel to the first front face and located in a direction opposite to a direction in which the light of the first front face is incident. The protruding part of the image display element is inserted into the opening of the first heat receiving unit, and the flow path part of the first heat receiving unit is in contact with the first side face and the second front face of the protruding part via a heat conductive member. A front face of the flow path part of the first heat receiving unit is flush with the first front face of the protruding part or in front of the first front face of the protruding part.

As described above, since the flow path part of the first heat receiving unit is in contact with the first side face and the second front face of the image display element via the heat conductive member, a light incident side of the image display element can be efficiently cooled. Furthermore, in the cooling device, since the front face of the flow path part of the first heat receiving unit is located on the same face as the first front face of the image display element or in front of the first front face, even when bending R is required at a corner between the front face and an inner wall part of the flow path part, a contact area with the first side face can be sufficiently secured.

(2) The projection display apparatus of (1) includes a prism unit in which a plurality of prisms each having a triangular prism or a quadrangular prism are directly bonded via an optical thin coating or fixed while an air gap is maintained on an optical path between the image display element and the projection lens unit. The first inflow pipe and the first outflow pipe of the first heat receiving unit extend in parallel to a face formed by the flow path part, and are connected to the flow path part at a position eccentric to a light incident side to the prism unit with respect to a center of the opening formed by the flow path part.

(3) In the projection display apparatus of (1), the flow path part of the first heat receiving unit includes a first pipe and a second pipe branching from the first inflow pipe and joining at the first outflow pipe, the first pipe and the second pipe form different sides of the opening that is rectangular of the first heat receiving unit, and the first pipe and the second pipe have an identical length.

(4) The projection display apparatus of (1) or (3) includes a prism unit in which a plurality of prisms each having a triangular prism or a quadrangular prism are directly bonded via an optical thin coating or fixed while an air gap is maintained on an optical path between the image display element and the projection lens unit. The first inflow pipe of the first heat receiving unit is connected to the flow path part on a high light density side of the prism unit, and the first outflow pipe is located on a high light density side of the light from the light source unit that has entered the prism unit.

(5) In the projection display apparatus device of (2) or (4), the first inflow pipe and the first outflow pipe of the first heat receiving unit extend along a longitudinal direction of the prism of the prism unit, the prism facing the image display element.

(6) In the projection display apparatus of any one of (1) to (5), the first inflow pipe and the first outflow pipe of the first heat receiving unit extend on a face parallel to the reflective image display of the image display element on an opposite side of a direction in which incident light enters the reflective image display.

(7) In the projection display apparatus of any one of (1) to (6), the first heat receiving unit includes a face that intersects or faces an inflow direction of the refrigerant at least until the refrigerant reaches the flow path part via the first inflow pipe.

(8) In the projection display apparatus of any one of (1) to (7), at least one of the first inflow pipe and the first outflow pipe of the first heat receiving unit is connected to the flow path part via a joint.

(9) The projection display apparatus of (2) or (4) includes a second heat receiving unit that receives driving heat of the image display element, and the first heat receiving unit is disposed between the prism unit and the image display element. The image display element is disposed between the first heat receiving unit and the second heat receiving unit. The second heat receiving unit includes a second inflow pipe into which the refrigerant flows, and a second outflow pipe through which the refrigerant flows out.

(10) In the projection display apparatus of (9), the second outflow pipe and the first inflow pipe are connected in series, the refrigerant flowing out of the second outflow pipe of the second heat receiving unit reaching the first inflow pipe of the first heat receiving unit.

(11) In the projection display apparatus of (9), the first heat receiving unit and the second heat receiving unit include a configuration, the refrigerant flowing in parallel.

(12) In the projection display apparatus of any one of (1) to (11), the flow path part of the first heat receiving unit is configured of two brazed plate members, and the two brazed plate members include a mating face parallel to an inner wall part of the flow path part forming the opening.

(13) In the projection display apparatus of any one of (1) to (12), the flow path part of the first heat receiving unit is configured of two brazed metal plate members, and the two brazed plate members include a mating face extending from an outer periphery of the flow path part in a direction perpendicular to an inner wall part of the flow path part forming the opening.

(14) In the projection display apparatus of any one of (1) to (13), the reflective image display is a digital mirror device.

(15) In the projection display apparatus of any one of (1) to (14), the flow path part of the first heat receiving unit is made of an aluminum clad material.

(16) In the projection display apparatus of (1), the image display element includes a protruding part located outside the reflective image display, and the protruding part includes the first front face, the second front face, and the first side face.

(17) In the projection display apparatus of (1), the image display element further includes a front face glass positioned in front of the reflective image display, and a base part including the second front face positioned outside the front face glass, and the first front face is a front face of the front face glass, and the first side face is a side face of the front face glass.

(18) In the projection display apparatus of (1), the flow path part of the first heat receiving unit includes a plane part parallel to the front face of the flow path part, and the front face of the flow path part is located around the plane part and in front of the plane part.

(19) In the projection display apparatus of (1), the flow path part of the first heat receiving unit includes a plurality of through holes penetrating in a front-rear direction.

The present disclosure is applicable to a projection display device including an image display element having a reflective image display.