JP6451277B2 - Virtual image display device and image projection device - Google Patents

Description

  The present invention relates to a virtual image display device and an image projection device.

  In a head-up display, a technique is known in which an intermediate image is formed on a small screen, and an enlarged image of the intermediate image is formed by a reflection optical system.

  By using the microlens array plate as a small screen, the image on the screen can be made high resolution. On the other hand, when a display element, which is a MEMS driving device such as DMD (Degital Mirror Device), is arranged close to the microlens array plate, the temperature of the microlens array plate rises due to heat generated by the display element. End up. As a result, the microlens array plate expands, the pixel pitch changes, and the refraction angle of the light beam on the pixel changes due to the change in the curvature of the microlens, making it difficult to obtain stable image performance. .

  So far, a head-up display device has been proposed in which the prism member that guides the laser beam from the projector and irradiates the screen member is integrally formed with the entrance and exit surfaces and the mirror surface that constitute the lens surface. (For example, refer to Patent Document 1). Further, a virtual image display device has been proposed that includes a diffusion region for diffusing display light on a screen and a reflection region for reflecting invisible light toward a light receiving means (see, for example, Patent Document 2). Furthermore, a two-dimensional image display device having a fine convex lens structure in which scanned surface elements are arranged in a honeycomb array and a ratio between an effective pixel pitch in the X direction and an effective pixel pitch in the Y direction is larger than 1 has been proposed ( For example, see Patent Document 3).

  An object of the present invention is to provide a virtual image display device that has a small amount of heat transferred from a display element to a screen.

A virtual image display device according to the present invention includes an image projection device that projects an image on a screen and an observation optical system that forms a virtual image of the image, and the image projection device is a display element on which an emitted light beam from a light source is incident. A first imaging optical system in which an outgoing light beam from the display element is incident, a second imaging optical system in which an outgoing light beam from the first imaging optical system is incident, and a light beam emitted from the second imaging optical system And a screen that emits a light beam to the observation optical system, the first imaging optical system forms a first intermediate image between the display element and the screen, and the second imaging optical system includes: A second intermediate image is formed on the screen, and one surface of the screen is a microlens array surface in which a plurality of microlenses are arranged two-dimensionally, and a curved surface curved so that the microlens array surface is on the inside It is characterized by being.

  According to the present invention, the amount of heat transferred from the display element to the screen can be reduced.

It is an optical arrangement | positioning figure which shows embodiment of the virtual image display apparatus concerning this invention. It is an optical arrangement | positioning figure inside the image projector with which the said virtual image display apparatus is provided. It is an optical path diagram which shows the incident light to the micro lens array board with which the said virtual image display apparatus is provided, and the light which permeate | transmits a micro lens array board. It is a side view which shows the mode of arrangement | positioning of the said micro lens array board. It is sectional drawing of the interruption | blocking body which covers the said micro lens array board. It is a side view which shows the micro lens array board with which another embodiment of the virtual image display apparatus concerning this invention is provided. It is an optical arrangement | positioning figure inside an image projector in the example of the conventional image projector.

● Virtual image display device ●
Hereinafter, a virtual image display device according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the virtual image display device 1 includes an observation optical system 2 and an image projection device 3.

  As an example, the virtual image display device 1 is a device that is mounted on a moving body such as a vehicle, an aircraft, or a ship, and the driver 100 of the moving body visually recognizes the virtual image 52 via the observation optical system 2. The virtual image 52 displays navigation information (for example, information such as vehicle speed and travel distance) necessary for maneuvering the moving body. Although the virtual image display device incorporated in the vehicle body is shown in FIG. 1, a method called a combiner method in which a small virtual image display device is assembled in the vicinity of the driver's eyes may be used. Here, the method using the windshield 22 will be described as the method of the observation optical system 2. However, the image projection device 3 may be a combiner method or a vehicle body incorporation method.

● Observation optics 2
In the observation optical system 2, the concave mirror 21 and the windshield 22 are arranged in this order in the optical path. The observation optical system 2 forms a virtual image 52 of the light beam emitted from the image projection device 3 on the opposite side of the windshield 22 from the driver 100 side. The windshield 22 reflects the light beam that forms the virtual image 52 toward the driver 100. The driver 100 visually recognizes the virtual image 52 from a predetermined observation position on the optical path of the light beam reflected by the windshield 22.

● Image projector 3
FIG. 2 is an optical layout diagram showing the optical path of the chief ray only. As shown in FIG. 2, in the image projection apparatus 3, a DMD 31, a first imaging optical system 32, a second imaging optical system 34, and a small screen 4 are arranged in this order in the optical path. The DMD 31, the first imaging optical system 32, the second imaging optical system 34, and the small screen 4 are accommodated in a casing 35 that blocks outside air. DMD 31 is an example of a display element.

  By sealing the entire optical system including the small screen 4 with the casing 35, it is possible to prevent dust from adhering to the small screen 4.

  The first imaging optical system 32 and the second imaging optical system 34 are constituted by, for example, a condenser lens.

  The light beam emitted from the light source 301 enters the DMD 31 via the illumination optical system 302. The DMD 31 is a light modulation element in which a plurality of micromirrors are arranged two-dimensionally. The DMD 31 is modulated and driven according to the image signal to be displayed. That is, the inclinations of the plurality of micromirrors are independently changed to an angle at which the incident light beam enters the first imaging optical system 32 and an angle at which the incident light flux does not enter the first imaging optical system 32. One minute mirror corresponds to one pixel.

  The divergent light beam emitted from each pixel of the DMD 31 becomes a converged light beam by the first imaging optical system 32. The outgoing light beam from the first imaging optical system 32 is condensed at the position of the first intermediate image 50 to form a real image of the DMD 31. The divergent light beam emitted from the real image of each pixel on the first intermediate image 50 becomes a converged light beam by the second imaging optical system 34 and forms an image on the small screen 4. The image formed on the small screen 4 is the second intermediate image 51.

  The DMD 31 and the first imaging optical system 32 adopt a retrofocus method in order to increase the distance between the DMD 31 and the first imaging optical system 32. By forming the first intermediate image 50, it is possible to correct the distortion generated by the retrofocus method. That is, the second imaging optical system 34 can reversely correct the distortion of the first intermediate image 50 up to the second intermediate image 51.

● Small screen 4
As shown in FIG. 3, the small screen 4 is a microlens array plate in which a plurality of microlenses 40-k are arranged two-dimensionally. The microlens array plate has a microlens array surface 41 on which a plurality of microlenses 40-k are formed, and a flat surface 42 without a lens. The plane 42 is on the opposite side of the microlens array surface 41. The parallel light beam 803 incident on the microlens array surface 41 is converted into a divergent light beam 804 and is emitted from the plane 42 toward the driver 100.

  By using the microlens array plate for the small screen 4, the luminous flux directed toward the driver 100 becomes a divergent luminous flux, so that the driver's 100 eye box (a spatial region where the driver 100 can visually recognize the virtual image 52) is enlarged. be able to. That is, even when the driver 100 moves his / her neck up / down / left / right, the range in which the virtual image 52 can be visually recognized is widened.

  As shown in FIG. 4, the microlens array surface 41 of the microlens array plate is disposed to be inclined downward with respect to the direction of gravity. In other words, the angle between the perpendicular line drawn to the center of the microlens array surface 41 and the direction of gravity is 90 degrees or less. The microlens array surface 41 has a recessed portion as compared with the flat surface 42, and dust easily adheres thereto. By arranging the microlens array surface 41 so as to be inclined downward in the direction of gravity, it is possible to suppress the accumulation of dust adhering to the microlens array plate.

  One microlens 40-k included in the microlens array plate corresponds to one pixel. In order to form a high-resolution image, it is necessary to make the microlens 40-k small. When one microlens 40-k is small, even if it is a small dust, the entire pixel is blocked by the dust, which causes pixel missing. In the microlens array plate that forms a high-resolution image, measures against dust adhesion are more important than a low-resolution screen.

  As shown in FIG. 5, the small screen 4 may be covered with a housing 36 that blocks outside air. The housing 36 includes a transmission plate 361 and a transmission plate 362 that transmit light. The transmission plate 361 faces the microlens array surface 41, and the transmission plate 362 faces the flat surface 42 of the microlens array plate. The transmission plate 361 transmits the light beam 805 incident on the microlens array surface 41, and the transmission plate 362 transmits the light beam 805 emitted from the plane 42 to the outside of the housing 36.

  The housing 36 is an example of a blocking body. The transmission plate 361 and the transmission plate 362 are examples of light transmission members.

  By covering the small screen 4 with the housing 36, it is possible to prevent dust from adhering to the small screen 4. When only the small screen 4 is covered with the housing 36, the housing covering the entire optical system may have a hole. With this configuration, it is possible to improve the air passage of the optical system and easily release the heat generated by the driving device such as the DMD 31.

  As shown in FIG. 6, the small screen 4 may be a curved surface curved so that the microlens array surface 41 is on the inside. Since the small screen 4 is a curved surface, it is possible to suppress the adhesion of dust to the microlens array surface due to the airflow 60 from the top to the bottom of the microlens array surface 41. In particular, the adhesion of dust can be further suppressed by arranging the curved microlens array surface to be inclined in the direction of gravity.

● Transmission of heat from the DMD 31 to the small screen 4 Since the mirror angle of the DMD 31 changes at high speed, the DMD 31 generates heat to drive it. The temperature of the small screen 4 rises due to the heat generated in the DMD 31. As a result, the small screen 4 expands and the pixel pitch changes, or the refraction angle of the light beam on the pixel changes due to the change in the curvature of the microlens.

  When the entire optical system is sealed with the casing 35 as shown in FIG. 2, or when the small screen 4 is sealed with the casing 36 as shown in FIG. 5, heat tends to be trapped inside the casing 35 and the casing 36. . Therefore, the distance between the DMD 31 and the small screen 4 should be increased.

  As shown in FIG. 7, in the conventional image projection apparatus 303, the emitted light from the DMD 331 forms an image on the small screen 304 via the first imaging optical system 332.

  In this configuration, the distance between the DMD 331 and the small screen 304 is shorter than that of the image projector 3 according to the present invention.

  When the distance between the DMD 331 and the small screen 304 is increased, the image-side NA on the small screen 304 is decreased, and a high-resolution image cannot be obtained. In addition, in order to obtain a high-resolution image in the conventional configuration, the optical elements and the like of the second imaging optical system must be enlarged.

  On the other hand, the image projection apparatus 3 according to the present invention forms a first intermediate image 50, thereby maintaining a long distance between the DMD 31 and the small screen 4 without increasing the size of the optical element. Can be obtained.

● About the size of the first intermediate image 50 and the second intermediate image 51 In order to reduce the amount of heat transferred from the DMD 31 to the small screen 4, the optical path length from the first intermediate image 50 to the second intermediate image 51 should be long. . Setting the lateral magnification of the first intermediate image 50 and the second intermediate image 51 to 1 is not desirable because the optical path length from the first intermediate image 50 to the second intermediate image 51 becomes the shortest. In order to increase the optical path length from the first intermediate image 50 to the second intermediate image 51, the first intermediate image 50 and the second intermediate image 51 need to have different sizes.

  If the first intermediate image 50 is configured to be larger than the second intermediate image 51, the second imaging optical system 34 must be disposed closer to the small screen 4. As a result, the second imaging optical system 34 must be further enlarged, which is not desirable. Accordingly, the first intermediate image 50 is configured to be smaller than the second intermediate image 51. By making the first intermediate image 50 smaller than the second intermediate image 51, the entire optical system can be made compact, and the housing 35 can be made small.

  According to the embodiment described above, since the distance between the DMD and the screen can be increased by forming the first intermediate image between the DMD and the screen, the amount of heat transferred from the DMD to the screen can be reduced. .

DESCRIPTION OF SYMBOLS 1 Virtual image display apparatus 2 Observation optical system 3 Image projector 4 Small screen 31 DMD
32 First imaging optical system 34 Second imaging optical system 50 First intermediate image 51 Second intermediate image

JP 2014-142423 A Japanese Patent No. 5392276 JP 2014-139656 A

Claims (7)

An image projection device for projecting an image;
An observation optical system for forming a virtual image of the image;
With
The image projector is
A display element on which the light emitted from the light source is incident;
A first imaging optical system on which an outgoing light beam from the display element enters;
A second imaging optical system on which an outgoing light beam from the first imaging optical system enters;
A screen that projects the light beam emitted from the second imaging optical system and emits the light beam to the observation optical system;
Have
The first imaging optical system forms a first intermediate image between the display element and the screen;
The second imaging optical system forms a second intermediate image on the screen;
One surface of the screen is a microlens array surface in which a plurality of microlenses are two-dimensionally arranged, and is a curved surface curved so that the microlens array surface is on the inside. A virtual image display device. Before Symbol of perpendicular line drawn at the center of the microlens array surface, the angle between the direction of gravity is equal to or less than 90 degrees, the virtual image display device according to claim 1, wherein.   The virtual image display device according to claim 1, wherein the screen is surrounded by a blocking body that blocks outside air.   The virtual image display device according to claim 3, wherein the blocking body includes a light transmitting member that transmits light, and the light transmitting member transmits incident light to the screen and outgoing light from the screen. The first intermediate image is smaller than the second intermediate image, the virtual image display device according to any one of claims 1 to 4. It said first imaging optical system converts the light beam emitted from the display element into a convergent light beam, the virtual image display device according to any one of claims 1 to 5. A display element on which the light emitted from the light source is incident;
A first imaging optical system on which an outgoing light beam from the display element enters;
A second imaging optical system on which an outgoing light beam from the first imaging optical system enters;
Light beam emitted from the second imaging optical system is projected, a screen for emitting the light beam to the observation optical system,
With
The first imaging optical system forms a first intermediate image between the display element and the screen;
The second imaging optical system forms a second intermediate image on the screen;
One surface of the screen is a microlens array surface in which a plurality of microlenses are two-dimensionally arranged, and is a curved surface curved so that the microlens array surface is on the inside. An image projection apparatus.

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