Projection-type image display device

Abstract

To provide a projection type video display device that can reduce generation of heat caused by stray light.SOLUTION: A projection type video display device of the present disclosure comprises: a light source; an image forming element that forms an image; a color separation and combination unit that separates light from the light source into first illumination light and second illumination light, emits the first illumination light and the second illumination light to the image forming element, and combines first projection light and second projection light reflected by the image forming element; and a notch filter that is arranged between the light source and the color separation and combination unit. A first dichroic filter reflects the first illumination light and the first projection light. A first incident angle of the first illumination light with respect to the first dichroic filter and a second incident angle of the first projection light with respect to the first dichroic filter are different from each other. The notch filter attenuates light in a first wavelength band including a boundary between the wavelength band of the first illumination light and the wavelength band of the second illumination light.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a projection-type video display device.

Background Art

[0002] A projection-type video display device that separates illumination light into three colors of red, green, and blue, synthesizes them, and displays them on a projection target is known.

[0003] For example, the projection-type video display device described in Patent Document 1 decomposes illumination light from an illumination optical system into a plurality of color lights having different wavelength regions, and synthesizes the respective color lights reflected by a reflection-type image display element to project and display color image light.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The projection-type video display device described in Patent Document 1 still has room for improvement in reducing heat generation caused by stray light.

[0006] The present disclosure provides a projection-type video display device capable of reducing heat generation caused by stray light.

Means for Solving the Problems

[0007] The projection-type video display device according to one aspect of the present disclosure is <XXX000119>a light source that irradiates light, an image forming element including a first image forming element that forms a first image and a second image forming element that forms a second image, A color separation and synthesis unit having a first dichroic filter that separates light from the light source into a first illumination light and a second illumination light having a wavelength band different from the wavelength band of the first illumination light, wherein the color separation and synthesis unit emits the first illumination light to the first image forming element and emits the second illumination light to the second image forming element, and synthesizes the first projected light reflected by the first image forming element and the second projected light reflected by the second image forming element, The system includes a notch filter positioned between the light source and the color separation and synthesis unit.

[0008] The first dichroic filter reflects the first illumination light and the first projection light.

[0009] The first incident angle of the first illumination light on the first dichroic filter and the second incident angle of the first projection light on the first dichroic filter are different.

[0010] The notch filter attenuates light in a first wavelength band that includes the boundary between the wavelength band of the first illumination light and the wavelength band of the second illumination light. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide a projection-type image display device that can reduce heat generation caused by stray light. [Brief explanation of the drawing]

[0012] [Figure 1] Schematic diagram showing the overall configuration of the projection-type video display device according to Embodiment 1. [Figure 2] Schematic diagram showing the light paths of the separated red wavelength bands in the color separation and synthesis section of the projection image display device shown in Figure 1. [Figure 3] Schematic diagram showing the light paths of the separated green wavelength band in the color separation and synthesis section of the projection image display device shown in Figure 1. [Figure 4] This figure shows the spectral transmittance characteristics of a red-reflecting dichroic filter. [Figure 5]Figure showing the spectral transmittance characteristics of a blue-reflecting dichroic filter. [Figure 6A] A diagram showing the optical paths of the first illumination light and the first projection light in a color separation and synthesis prism. [Figure 6B] Enlarged view of region E1 in Figure 6A [Figure 7] A diagram showing the optical paths of the second illumination light and the second projection light in a color separation and synthesis prism. [Figure 8] This figure shows the spectral transmittance characteristics of a notch filter corresponding to a red-reflecting dichroic filter. [Figure 9] This figure shows the spectral transmittance characteristics of a notch filter corresponding to a blue-reflecting dichroic filter. [Figure 10] A diagram showing the wavelength distribution of illumination light incident on the color separation and synthesis section. [Figure 11] A diagram showing the wavelength distribution of projected light emitted from the color separation and synthesis unit. [Modes for carrying out the invention]

[0013] (Background leading to this disclosure) Conventionally, projection-type image display devices have been developed that separate illumination light from a light source into three colors: red, green, and blue, and then combine the three separated colors of light to project onto a projection target such as a screen.

[0014] In this type of projection-based image display device, a dichroic filter placed within a color separation and synthesis prism separates the light into three colors: red, green, and blue. This light is then transmitted, or transmitted and reflected, through different block-shaped prisms within the color separation and synthesis prism, guiding the light to image forming elements for red, green, and blue light, which are provided for each prism. Each image forming element selects the direction in which the light of its respective color is reflected, separating the light to be projected onto the screen from the unwanted light. The projected light then passes through the color separation and synthesis prism again, where the red, green, and blue colors are recombined by the dichroic filter. The combined light is then projected onto the screen via the projection optical system.

[0015] Dichroic filters exhibit an incident angle dependence; as the incident angle of light on the dichroic filter increases, the transmission curve of the dichroic filter shifts towards shorter wavelengths. In projection-type image display devices, the incident angle of illumination light from the light source on the dichroic filter is generally different from the incident angle of projected light reflected by the image forming element on the dichroic filter. As a result, the difference in incident angles between the illumination light and the projected light generates stray light within the color separation and synthesis prism. This stray light generated within the color separation and synthesis prism heats the surface of the image forming element and the color separation and synthesis prism itself.

[0016] In projection-type image display devices, further increases in brightness are being pursued to improve visibility or to enable projection onto larger screens. When the intensity of the illumination light incident on the color separation and synthesis prism is increased to achieve higher brightness, stray light generated due to differences in the angle of incidence causes an increase in the surface temperature of the image forming element and the color separation and synthesis prism. Normally, the gap between the color separation and synthesis prism and the image forming element is very narrow, making it difficult to lower the surface temperature of the image forming element that has risen due to stray light. Therefore, the generation of stray light becomes a limitation on increasing brightness. In addition, the stray light heats the surface of the image forming element and the color separation and synthesis prism, causing the temperature to rise and deformation of the color separation and synthesis prism due to thermal expansion. Due to the deformation of the color separation and synthesis prism, the optical path inside the color separation and synthesis prism deviates from the desired optical path, resulting in a phenomenon called convergence shift, where the red, green, and blue light, which should ideally be imaged at a single point on the screen when projected from the projection optical system onto the screen, are imaged at different points on the screen. One problem is that convergence misalignment can significantly degrade the quality of the projected image.

[0017] Therefore, the present inventors investigated a projection-type image display device that can reduce heat generation caused by stray light, and arrived at the following invention.

[0018] The embodiments will be described in detail below, with reference to the drawings as appropriate. However, unnecessarily detailed explanations may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for the parties involved.

[0019] The attached drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0020] (Embodiment 1) [1-1. Structure] Referring to Figure 1, the projection-type image display device 1 according to Embodiment 1 will be described. Figure 1 is a schematic diagram showing the overall configuration of the projection-type image display device 1 according to Embodiment 1.

[0021] As shown in Figure 1, the projection-type image display device 1 comprises a light source 10, an image forming element 106, a color separation and synthesis unit 330, and a notch filter 135, and is a device that projects an image onto a screen (projection target) 400. In the projection-type image display device 1, light from the light source 10 enters the color separation and synthesis unit 330, is reflected by the image forming element 106, and is emitted from the projection lens unit 140 via the color separation and synthesis unit 330 and projected onto the screen 400.

[0022] The light source 10 irradiates visible light toward the color separation and synthesis unit 330. The visible light from the light source 10 has continuous spectral characteristics.

[0023] In the light source 10, light is emitted from two semiconductor lasers 201 and 202. The semiconductor lasers 201 and 202 emit blue light with a central wavelength of, for example, 456 nm. The light emitted from the semiconductor lasers 201 and 202 is polarized to be P-polarized.

[0024] The blue light emitted from the semiconductor laser 201 passes through the convex lens 211 and the concave lens 212, and then through the diffuser plate 204. The convex lens 211 and the concave lens 212 are afocal lenses that reparallelize the light emitted from the semiconductor laser 201. The blue light emitted from the semiconductor laser 201 passes through the convex lens 211 and the concave lens 212, is shaped into parallel light of the desired ray width, and then passes through the diffuser plate 204 to reach the dichroic mirror 206.

[0025] The dichroic mirror 206 has the property of transmitting P-polarized blue light. Therefore, the P-polarized blue light emitted from the semiconductor laser 201 is transmitted through the dichroic mirror 206, then through the condenser lenses 231 and 232, and is gradually focused and roughly imaged by the phosphor wheel 250.

[0026] The phosphor wheel 250 is constructed, for example, by providing a phosphor layer on the surface of a circular aluminum substrate. A rotary motor is positioned in the center of the aluminum substrate, allowing the phosphor wheel 250 to rotate. The phosphor layer is formed by coating, for example, a YAG phosphor that is excited by blue light and emits yellow light containing green and red wavelength components. Light that is substantially imaged by the phosphor layer of the phosphor wheel 250 is reflected as yellow light. By rotating the phosphor wheel 250, the temperature rise of the phosphor layer due to blue excitation light is suppressed, and the fluorescence conversion efficiency can be stably maintained. Yellow light is continuously emitted from the phosphor wheel 250.

[0027] The yellow light reflected by the phosphor wheel 250 passes through the condenser lenses 231 and 232, is reflected by the dichroic mirror 206, passes through the condenser lens 104, and enters the rod integrator 105.

[0028] Meanwhile, the blue light emitted from the semiconductor laser 202 passes through the convex lens 221 and the concave lens 222 and reaches the reflective mirror 203. The convex lens 221 and the concave lens 222 are afocal lenses that reparallelize the light emitted from the semiconductor laser 202. The blue light emitted from the semiconductor laser 202 passes through the convex lens 221 and the concave lens 222, is shaped into parallel light of the desired ray width, is reflected by the reflective mirror 203, passes through the diffuser plate 205 and reaches the dichroic mirror 206.

[0029] The P-polarized light emitted from the semiconductor laser 202 passes through the dichroic mirror 206, combines with the yellow light reflected by the dichroic mirror 206, passes through the condenser lens 104, and enters the rod integrator 105.

[0030] In this way, yellow light containing green and red wavelength components emitted from the phosphor wheel 250 and blue light from the semiconductor laser 202 are combined by the dichroic mirror 206.

[0031] The rod integrator 105 is made of a transparent material such as glass. The rod integrator generates light with a uniform intensity distribution by reflecting the incident light multiple times inside. The rod integrator 105 may be a solid rod, or it may be a hollow rod whose inner wall is made of a mirror surface.

[0032] Lenses 121, 122, and 123 form a relay optical system that substantially images the light emitted from the rod integrator 105 onto the image forming element 106. The light emitted from the rod integrator 105 passes through lenses 121, 122, and 123, is reflected by the reflection mirror 134, and then passes through the notch filter 135 before entering the color separation and synthesis unit 330. The notch filter 135 attenuates light in a predetermined wavelength band from the light that has passed through lenses 121 to 123. Details of the notch filter 135 will be described later.

[0033] Figure 2 is a schematic diagram showing the path of light in the red wavelength band separated in the color separation and synthesis unit 330 of the projection-type image display device 1 shown in Figure 1. Figure 3 is a schematic diagram showing the path of light in the green wavelength band separated in the color separation and synthesis unit 330 of the projection-type image display device 1 shown in Figure 1. Note that the blue reflective dichroic filter 186 is omitted from the illustration in Figure 2, and the red reflective dichroic filter 185 is omitted from the illustration in Figure 3.

[0034] As shown in Figures 2 and 3, the color separation and synthesis unit 330 includes a total reflection prism 130 and a color separation and synthesis prism 340. The total reflection prism 130 is composed of, for example, two approximately triangular prism-shaped prisms 130a and 130b. The total reflection prism 130 internally reflects the illumination light from the light source 10 and emits it toward the image forming element 106. A notch filter 135 is placed on the surface of prism 130b into which the illumination light from the light source 10 is incident.

[0035] The color separation and synthesis unit 330 separates light from the light source into red illumination light (first illumination light), green illumination light (second illumination light), and blue illumination light (third illumination light) with different wavelength bands using a red-reflecting dichroic filter and a blue-reflecting dichroic filter. The color separation and synthesis unit 330 also emits the red illumination light to the image forming element 106R (first image forming element), the green illumination light to the image forming element 106G (second image forming element), and the blue illumination light to the image forming element 106B (third image forming element). Furthermore, the color separation and synthesis unit 330 synthesizes the red projected light (first projected light) reflected by the image forming element 106R, the green projected light (second projected light) reflected by the image forming element 106G, and the blue projected light (third projected light) reflected by the image forming element 106B.

[0036] The wavelength range of red light (first illumination light and first projection light) is, for example, 600 nm to 730 nm. The wavelength range of green light (second illumination light and second projection light) is, for example, 515 nm to 599 nm. The wavelength range of blue light (third illumination light and third projection light) is, for example, 420 nm to 514 nm.

[0037] The color separation and synthesis prism 340 consists of three prisms 340G, 340R, and 340B. As shown in Figure 6A, prism 340G faces the image forming element 106G, prism 340R faces the image forming element 106R, and prism 340B faces the image forming element 106B. The color separation and synthesis prism 340 further includes a red-reflecting dichroic filter 185 and a blue-reflecting dichroic filter 186. A red-reflecting dichroic filter 185 (first dichroic filter, see Figure 2) is formed on the proximity surface between prism 340G and prism 340R. A blue-reflecting dichroic filter 186 (second dichroic filter, see Figure 3) is formed between prism 340R and prism 340B. Specifically, as shown in Figure 6A, the red-reflecting dichroic filter 185 is positioned between prism 340R and prism 340G, and the blue-reflecting dichroic filter 186 is positioned between prism 340R and prism 340B. Prisms 340R and 340B are roughly triangular prism-shaped prisms, and prism 340G is roughly rectangular prism-shaped prism.

[0038] Light incident on the color separation and synthesis prism 340 is separated into red, green, and blue light in their respective wavelength bands, and then roughly imaged by the image forming elements 106 corresponding to each color.

[0039] In this embodiment, the image forming element 106 includes three image forming elements: image forming element 106R (first image forming element), image forming element 106G (second image forming element), and image forming element 106B (third image forming element). In this embodiment, the image forming element 106 is composed of a digital micromirror device (DMD) having a plurality of movable micromirrors. Each micromirror of the image forming element 106 basically corresponds to one pixel. Based on various control signals, the image forming element 106 changes the angle of each micromirror, thereby switching whether or not to direct the light reflected by the image forming element 106 towards the projection lens unit 140. In this way, each image forming element forms an image.

[0040] Of the light reflected by the image forming element 106, the light to be projected as an image (DMD-ON light) enters the projection lens unit 140 and is then emitted onto the screen 400. Of the light reflected by the image forming element 106, the light not to be projected as an image (DMD-OFF light) does not enter the projection lens unit 140 but is output from the color separation and synthesis prism 340.

[0041] Here, with reference to Figure 2, the path of light in the red wavelength band will be explained. In the following explanation, the red wavelength band light traveling from the light source 10 to the image forming element 106R will be referred to as the first illumination light Ln1, and the light reflected by the image forming element 106R and projected as an image (DMD-ON light) will be referred to as the first projection light Pn1.

[0042] Of the light incident on the color separation and synthesis prism 340 from the total internal reflection prism 130, the first illumination light Ln1 in the red wavelength band passes through the blue reflection dichroic filter 186 (see Figure 3) via prism 340B and then incident on prism 340R. The first illumination light Ln1 incident on prism 340R from prism 340B passes through prism 340R and reaches the red reflection dichroic filter 185. The first illumination light Ln1 that reaches the red reflection dichroic filter 185 is reflected by the red reflection dichroic filter 185.

[0043] The first illumination light Ln1 in the red wavelength band, reflected by the red dichroic filter 185, undergoes total internal reflection at the surface of prism 340R through the gap between prism 340R and prism 340B, and is substantially imaged onto the image forming element 106R.

[0044] The first projected light Pn1, reflected by the image forming element 106R, is again incident on the prism 340R, undergoes total internal reflection on the surface of the prism 340R, and then is again incident on the red-reflecting dichroic filter 185. The first projected light Pn1, which has been mostly reflected by the red-reflecting dichroic filter 185, passes through the prism 340B and the total internal reflection prism 130, is incident on the projection lens unit 140, and is then projected onto the screen 400.

[0045] Next, with reference to Figure 3, the path of light in the green wavelength band will be described. In the following description, the light in the green wavelength band traveling from the light source to the image forming element 106G will be referred to as the second illumination light Ln2, and the light reflected by the image forming element 106G and projected as an image (DMD-ON light) will be referred to as the second projection light Pn2.

[0046] Of the light incident on the color separation and synthesis prism 340 from the total internal reflection prism 130, the second illumination light Ln2 in the green wavelength band passes through the blue reflection dichroic filter 186 via prism 340B and then incident on prism 340R. The second illumination light Ln2 incident on prism 340R from prism 340B passes through prism 340R and reaches the red reflection dichroic filter 185 (see Figure 2). The second illumination light Ln2 that reaches the red reflection dichroic filter 185 passes through the red reflection dichroic filter 185 and is incident on prism 340G. The second illumination light Ln2 passes through prism 340G and is substantially imaged on the image forming element 106G.

[0047] The second projected light Pn2, reflected by the image forming element 106G, is again incident on the prism 340G, largely passes through the red reflective dichroic filter 185 (see Figure 2), and then incident on the prism 340R. After passing through the prism 340R, the second projected light Pn2 is again incident on the blue reflective dichroic filter 186. The second projected light Pn2 largely passes through the blue reflective dichroic filter 186, passes through the prism 340B and the total internal reflection prism 130, and then incident on the projection lens unit 140 before being projected onto the screen 400.

[0048] Meanwhile, of the light incident from the total reflection prism 130 to the color separation and synthesis prism 340, the third illumination light in the blue wavelength band is incident on prism 340B, reflected by the blue reflection dichroic filter 186, undergoes total reflection on the surface of prism 340B, and is then substantially imaged onto the image forming element 106B.

[0049] The third projected light reflected by the image forming element 106B enters the prism 340B again, undergoes total internal reflection on the surface of the prism 340B, and then enters the blue dichroic filter 186 again. The third projected light, which has been mostly reflected by the blue dichroic filter 186, passes through the prism 340B and the total internal reflection prism 130, enters the projection lens unit 140, and is then projected onto the screen 400.

[0050] Figure 4 shows the spectral transmittance characteristics of the red-reflecting dichroic filter 185. Figure 5 shows the spectral transmittance characteristics of the blue-reflecting dichroic filter 186. Figure 6A shows the optical paths of the first illumination light Ln1 and the first projection light Pn1 in the color separation and synthesis prism 340. Figure 6B is an enlarged view of region E1 in Figure 6A. Figure 7 shows the optical paths of the second illumination light Ln2 and the second projection light Pn2 in the color separation and synthesis prism 340.

[0051] In Figure 4, the dashed line shows the spectral transmittance characteristics of the first illumination light Ln1 to the red-reflecting dichroic filter 185 at the first incident angle θ1, and the solid line shows the spectral transmittance characteristics of the first projected light Pn1 to the red-reflecting dichroic filter 185 at the second incident angle θ2. In Figure 5, the dashed line shows the spectral transmittance characteristics of the second illumination light Ln2 to the blue-reflecting dichroic filter 186 at the third incident angle θ3, and the solid line shows the spectral transmittance characteristics of the second projected light Pn2 to the blue-reflecting dichroic filter 186 at the fourth incident angle θ4.

[0052] The red-reflecting dichroic filter 185 reflects light in the red wavelength band and transmits light in wavelength bands other than red. In other words, the red-reflecting dichroic filter 185 reflects the first illumination light Ln1 and the first projection light Pn1.

[0053] As shown in Figures 6A and 6B, the first illumination light Ln1 in the red wavelength band is incident on the red reflective dichroic filter 185 at a first incidence angle θ1, and is reflected towards the image forming element 106R. The first projection light Pn1 in the red wavelength band reflected by the image forming element 106R is incident on the red reflective dichroic filter 185 at a second incidence angle θ2.

[0054] The first incident angle θ1 of the first illumination light Ln1 to the red reflective dichroic filter 185 and the second incident angle θ2 of the first projected light Pn1 to the red reflective dichroic filter 185 are different. In this embodiment, the second incident angle θ2 is smaller than the first incident angle θ1; that is, the first projected light Pn1 is incident on the red reflective dichroic filter 185 at a smaller angle than the first illumination light Ln1.

[0055] The red-reflecting dichroic filter 185 has the property that its spectral transmittance characteristics change depending on the angle of incidence. Therefore, as shown in Figure 4, in the red-reflecting dichroic filter 185, a phenomenon occurs in which components of the wavelength band that are reflected by the first illumination light Ln1 are transmitted by the first projection light Pn1. This phenomenon is called dichroic shift. In this embodiment, region R1 in Figure 4 is the wavelength band that is reflected by the first illumination light Ln1 and transmitted by the first projection light Pn1. This region R1 is a wavelength band that includes the boundary between the red wavelength band and the green wavelength band, and mainly contains amber-colored light.

[0056] When the first illumination light Ln1 is incident on the red reflective dichroic filter 185, the light in region R1 is reflected and directed towards the image forming element 106R. When the first projection light Pn1 reflected by the image forming element 106R is incident on the red reflective dichroic filter again, the light in region R1 is transmitted and becomes stray light Sn1 inside the color separation and synthesis prism 340. The stray light Sn1 heats up the image forming element 106 or other components of the color separation and synthesis unit 330. As a result, the temperature of the components of the image forming element 106 or the color separation and synthesis unit 330 rises, or convergence shift occurs in the image projected onto the screen 400.

[0057] The blue-reflecting dichroic filter 186 reflects light in the blue wavelength band and transmits light in wavelength bands other than blue. In other words, the blue-reflecting dichroic filter 186 reflects the third illumination light and the third projection light.

[0058] Here, as shown in Figure 7, the second illumination light Ln2 in the green wavelength band is incident on the blue reflective dichroic filter 186 at a third incidence angle θ3, and is transmitted towards the image forming element 106G. The second projection light Pn2 in the green wavelength band, reflected by the image forming element 106G, is incident on the blue reflective dichroic filter 186 at a fourth incidence angle θ4.

[0059] The third incidence angle θ3 of the second illumination light Ln2 to the blue-reflecting dichroic filter 186 and the fourth incidence angle θ4 of the second projection light Pn2 to the blue-reflecting dichroic filter 186 are different. In this embodiment, the fourth incidence angle θ4 is smaller than the third incidence angle θ3; that is, the second projection light Pn2 is incident on the blue-reflecting dichroic filter 186 at a smaller angle than the second illumination light Ln2.

[0060] The blue-reflecting dichroic filter 186 also has the property that its spectral transmittance characteristics change depending on the angle of incidence. Therefore, as shown in Figure 5, in the blue-reflecting dichroic filter 186, a phenomenon occurs in which components in the wavelength band that are transmitted by the second illumination light Ln2 are reflected by the second projection light Pn2. In other words, a dichroic shift occurs in the blue-reflecting dichroic filter 186 as well. In this embodiment, region R2 in Figure 5 is the wavelength band that is transmitted by the second illumination light Ln2 and reflected by the second projection light Pn2. This region R2 is a wavelength band that includes the boundary between the green wavelength band and the blue wavelength band, and mainly contains cyan colored light.

[0061] When the second illumination light Ln2 is incident on the blue-reflecting dichroic filter 186, the light in region R2 is transmitted and heads towards the image forming element 106G. When the second projection light Pn2, reflected by the image forming element 106G, is incident on the blue-reflecting dichroic filter again, the light in region R2 is reflected and becomes stray light Sn2 inside the color separation and synthesis prism 340. The stray light Sn2 heats up the image forming element 106 or other components of the color separation and synthesis unit 330. As a result, the temperature of the components of the image forming element 106 or the color separation and synthesis unit 330 rises, or convergence shifts occur in the image projected onto the screen 400.

[0062] In this embodiment, a notch filter 135 is placed between the light source 10 and the color separation and synthesis unit 330. More specifically, the notch filter 135 is placed between the lens 123 of the relay optical system and the total internal reflection prism 130. The placement of the notch filter 135 reduces stray light by attenuating light in at least a portion of the wavelength bands in regions R1 and R2 shown in Figures 4 and 5.

[0063] The notch filter 135 is a bandstop filter that attenuates light of a specific wavelength. More specifically, the notch filter 135 reflects at least a portion of the light from the light source 10 in regions R1 and R2. The light reflected by the notch filter 135 is absorbed by the relay optical system of the light source 10 and therefore does not enter the color separation and synthesis unit 330.

[0064] In this embodiment, the notch filter 135 is positioned on the incident surface of the light from the light source 10 to the color separation and synthesis unit 330. More specifically, it is positioned on the surface of the total reflection prism 130 to which the light from the light source 10 is incident. The notch filter 135 is positioned perpendicular to the optical axis from the light source 10.

[0065] For example, the notch filter 135 can be made by forming a filter that attenuates the amber color component on the front and back of a plate-shaped optical element, and a filter that attenuates the cyan color component on the back. That is, the notch filter 135 may include a notch filter that attenuates the amber color component and a notch filter that attenuates the cyan color component.

[0066] Figure 8 shows the spectral transmittance characteristics of the notch filter 135 corresponding to the red-reflecting dichroic filter 185. Figure 9 shows the spectral transmittance characteristics of the notch filter 135 corresponding to the blue-reflecting dichroic filter 186. The notch filter 135 will be described with reference to Figures 8 and 9.

[0067] In Figure 8, the dashed line shows the spectral transmittance characteristics of the first illumination light Ln1 at the first incident angle to the red-reflecting dichroic filter 185, the solid line shows the spectral transmittance characteristics of the first projected light Pn1 at the second incident angle to the red-reflecting dichroic filter 185, and the dashed-dotted line shows the spectral transmittance characteristics of the notch filter. In Figure 9, the dashed line shows the spectral transmittance characteristics of the second illumination light Ln2 at the third incident angle to the blue-reflecting dichroic filter 186, the solid line shows the spectral transmittance characteristics of the second projected light Pn2 at the fourth incident angle to the blue-reflecting dichroic filter 186, and the dashed-dotted line shows the spectral transmittance characteristics of the notch filter.

[0068] As shown in Figure 8, the notch filter 135 attenuates at least a portion of the light from the light source 10 that is included in region R1 of the red-reflecting dichroic filter 185 before it enters the color separation and synthesis unit 330. That is, at least a portion of the light from the light source 10 that could become stray light is reflected by the notch filter 135. The wavelength band that includes the boundary between the wavelength band of the first illumination light Ln1 (red wavelength band) and the wavelength band of the second illumination light Ln2 (green wavelength band) that are attenuated by the notch filter 135 corresponds to the first wavelength band of this disclosure. The light in the first wavelength band mainly contains an amber color component.

[0069] Similarly, as shown in Figure 9, the notch filter 135 attenuates at least a portion of the light from the light source 10 that is included in region R2 of the blue-reflecting dichroic filter 186 before it enters the color separation and synthesis unit 330. That is, at least a portion of the light from the light source 10 that could become stray light is reflected by the notch filter 135. The wavelength band including the boundary between the wavelength band of the second illumination light Ln2 (green wavelength band) and the wavelength band of the third illumination light (blue wavelength band) that are attenuated by the notch filter 135 corresponds to the second wavelength band of this disclosure. The light in the second wavelength band mainly contains a cyan component.

[0070] As shown in Figures 8 and 9, in this embodiment, the minimum transmittance of the wavelength attenuated by the notch filter 135 is approximately 55% to 65%. If the minimum transmittance of the wavelength attenuated by the notch filter is 80% or less, stray light can be sufficiently reduced. More specifically, as shown in Figure 8, the notch filter (first notch filter) that attenuates the amber component of the notch filter 135 has a center wavelength (λ) in the first wavelength band. NF1 It attenuates the light of the first wavelength band by more than 20%. In one example, the first notch filter reduces the light of the center wavelength (λ) of the first wavelength band. NF1 The light from the first notch filter may be attenuated by 30% or more. The full width at half maximum of the first notch filter may be, for example, 25 nm or less. In one example, the full width at half maximum of the first notch filter may be 20 nm or 15 nm or less. Also, as shown in Figure 9, the notch filter (second notch filter) that attenuates the cyan component of the notch filter 135 has a center wavelength (λ) in the second wavelength band. NF3 It attenuates the light of ) by more than 20%. In one example, the second notch filter has a center wavelength (λ) in the second wavelength band. NF3 The light from the second notch filter may be attenuated by 30% or more, or by 40% or more. The full width at half maximum of the second notch filter may be, for example, 25 nm or less. In one example, the full width at half maximum of the second notch filter may be 20 nm or 15 nm or less.

[0071] The characteristics of the notch filter 135 corresponding to the red reflecting dichroic filter 185 satisfy equations (1) and (2). Specifically, λDM1 is λ DM2 When it is smaller than λ, the characteristics of the notch filter 135 satisfy the upper part of Equation (1) and Equation (2), and λ DM1 is λ DM2 When it is larger than λ, the characteristics of the notch filter 135 satisfy the lower part of Equation (1) and Equation (2).

[0072] [Number]

[0073] [Number]

[0074] Here, λ DM1 is the wavelength at which the transmittance of the light incident on the red reflection dichroic filter 185 at the first incident angle θ1 is 50%. λ DM2 is the wavelength at which the transmittance of the light incident on the red reflection dichroic filter 185 at the second incident angle θ2 is 50%. λ DM3 is λ DM1 and λ DM2 is the wavelength width between and λ NF1 is the center wavelength of the first wavelength band of the notch filter 135. λ NF2 is the full width at half maximum (FWHM) of the first wavelength band. In the example of FIG. 8, λ NF1 = 582 nm, λ NF2 = 13 nm, λ DM1 = 562 nm, λ DM2 = 596 nm, λ DM3 = 34 nm.

[0075] Similarly, the characteristics of the notch filter 135 corresponding to the blue reflection dichroic filter 186 satisfy Equation (3) and Equation (4). Specifically, when λ DM4 is smaller than λ DM5 the characteristics of the notch filter 135 satisfy the upper part of Equation (3) and Equation (4), and when λ DM4 is larger than λ DM5 the characteristics of the notch filter 135 satisfy the lower part of Equation (3) and Equation (4).

[0076]

number

[0077]

number

[0078] Here, .'' DM4 λ is the wavelength at which the transmittance of light incident on the blue dichroic filter 186 at the third incidence angle θ3 is 50%. DM5 λ is the wavelength at which the transmittance of light incident on the blue dichroic filter 186 at the fourth incidence angle θ4 is 50%. DM6 is, λ DM4 and λ DM5 This is the wavelength range between λ. NF3 λ is the center wavelength of the second wavelength band of the notch filter 135. NF4 This is the full width at half maximum (FWHM) in the second wavelength band. In the example in Figure 9, λ NF3 = 513 nm, λ NF4 =13nm, λ DM4 =497nm, λ DM5 =520nm, λ DM6 = 23 nm

[0079] Figure 10 shows the wavelength distribution of illumination light incident on the color separation and synthesis unit 330. Figure 11 shows the wavelength distribution of projected light emitted from the color separation and synthesis unit 330. In Figure 10, the solid line shows the wavelength distribution when the notch filter 135 is installed, and the dashed line shows the wavelength distribution when the notch filter 135 is not installed.

[0080] As shown in Figure 10, when the notch filter 135 is placed, the light in the first wavelength band and the second wavelength band of the illumination light incident on the color separation and synthesis unit 330 is attenuated. As shown in Figure 11, the dichroic shift in the red-reflecting dichroic filter 185 and the blue-reflecting dichroic filter 186 causes a loss of light including the first wavelength band and the second wavelength band. By placing the notch filter 135, the light in the missing wavelength bands of the projected light can be attenuated before it is incident on the color separation and synthesis unit 330. Therefore, the wavelength distribution and light intensity of the projected light do not change regardless of whether the notch filter 135 is placed or not.

[0081] As described above, by arranging the notch filter 135, stray light in the color separation and synthesis unit 330 can be reduced, thereby suppressing heat generation in the image forming element 106 or the color separation and synthesis unit 330. When the notch filter 135 is arranged, stray light can be reduced by about 30% compared to when the notch filter 135 is not arranged.

[0082] [1-2. Effects, etc.] According to the embodiment described above, stray light generated by the difference in the angle of incidence to the dichroic filter (dichroic shift) can be reduced. As a result, heat generation in the image forming element 106 and the color separation and synthesis unit 330 can be suppressed.

[0083] To improve the efficiency of projection-type image display devices, there is a tendency to increase the tilt angle of the image forming element (DMD) 106. However, as the tilt angle of the image forming element (DMD) 106 increases, the dichroic shift also increases, which tends to increase stray light. In this embodiment, the notch filter 135 reduces stray light by pre-attenuating light in the wavelength band that becomes stray light in the color separation and synthesis unit 330 and the image forming element 106.

[0084] Furthermore, by reducing stray light, heat generation in the image forming element 106 and the color separation and synthesis unit 330 can be reduced, thereby suppressing the occurrence of convergence misalignment and other issues.

[0085] (Other embodiments) As described above, the above embodiments have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these embodiments and can be applied to embodiments that have been modified, replaced, added, or omitted. Furthermore, it is possible to create new embodiments by combining the components described in the above embodiments.

[0086] In the embodiment described above, the color separation and synthesis unit 330 was shown to separate and synthesize light from a light source into three wavelength bands: a first illumination light, a second illumination light, and a third illumination light. However, the invention is not limited to this. For example, the third image forming element is not a mandatory component, and the image forming element configuration may include a first image forming element and a second image forming element. In this case, the notch filter only needs to attenuate the light in the first wavelength band that includes the boundary between the wavelength band of the first illumination light and the wavelength band of the second illumination light. For example, by using two image forming elements to rapidly time-division control the display of green (first illumination light) and the display of red and blue (second illumination light), the image projected onto the screen 400 can be perceived as a full-color image.

[0087] Furthermore, although the above-described embodiment mentions an example in which the notch filter 135 is placed on the total reflection prism 130 of the color separation and synthesis unit 330, the placement of the notch filter 135 is not limited to this. The notch filter 135 only needs to be placed between the light source 10 and the color separation and synthesis unit 330, and for example, the notch filter 135 may be placed on the surface of any of the lenses 121 to 123 of the relay optical system.

[0088] Furthermore, in the embodiments described above, an example was described in which the notch filter 135 uses a plate-shaped optical member with a filter that attenuates the amber component and a filter that attenuates the cyan component formed on the front and back sides, respectively, but it is not limited to this. The notch filter may, for example, have a filter that attenuates both the amber and cyan components formed on one side of a plate-shaped optical member. Alternatively, it may have a configuration that includes both a filter that attenuates the amber component and a filter that attenuates the cyan component. Alternatively, without using a plate-shaped optical member, it may have a configuration that includes both a filter that attenuates the amber component and a filter that attenuates the cyan component on the side of the lens 123 of the relay optical system of the total reflection prism 130.

[0089] Furthermore, although the above-described embodiment described an example in which the image forming element 106 is a DMD, the invention is not limited to this. The image forming element 106 may also be a reflective type image display element such as an LCOS.

[0090] As described above, embodiments have been explained as examples of the technology in this disclosure. For this purpose, attached drawings and a detailed description have been provided. Therefore, among the components described in the attached drawings and detailed description, there may be not only components that are essential for solving the problem, but also components that are not essential for solving the problem, in order to illustrate the above technology. Therefore, the mere fact that these non-essential components are described in the attached drawings and detailed description should not be immediately assumed to mean that these non-essential components are essential.

[0091] Furthermore, since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the claims or their equivalents.

[0092] (Summary of the embodiment) (1) The projection-type image display device of the present disclosure includes a light source that emits light, an image forming element including a first image forming element and a second image forming element that form an image, a color separation and synthesis unit that separates light from the light source into a first illumination light and a second illumination light having different wavelength bands using a first dichroic filter, emits the first illumination light to the first image forming element and the second illumination light to the second image forming element, and synthesizes the first projection light reflected by the first image forming element and the second projection light reflected by the second image forming element, and a notch filter disposed between the light source and the color separation and synthesis unit. The first dichroic filter reflects the first illumination light and the first projection light, and the first incident angle of the first illumination light with respect to the first dichroic filter and the second incident angle of the first projection light with respect to the first dichroic filter are different, and the notch filter attenuates light in a first wavelength band that includes the boundary between the wavelength band of the first illumination light and the wavelength band of the second illumination light.

[0093] This configuration makes it possible to provide a projection-type image display device that can reduce heat generation caused by stray light.

[0094] (2) In the projection-type image display device of (1), the notch filter is λ DM3 >λ NF2 , and, λ DM1 +λ DM3 / 4≦λ NF1 ≤λ DM2 -λ DM3 / 4(λ DM1 <λ DM2 (In the case of) or λ DM2 +λ DM3 / 4≦λ NF1 ≤λ DM1 -λ DM3 / 4(λ DM1 >λ DM2 In the case of λ, satisfying the condition DM1 λ is the wavelength at which the transmittance of light incident on the first dichroic filter at the first incident angle is 50%. DM2 λ is the wavelength at which the transmittance of light incident on the first dichroic filter at the second incidence angle is 50%. DM3 is, λ DM1 and λ DM2 The wavelength width between λNF1 λ is the center wavelength of the first wavelength band of the notch filter. NF2 This is the full width at half maximum (FWHM) of the first wavelength band of the notch filter.

[0095] With this configuration, the notch filter can efficiently attenuate light in wavelength bands that would otherwise be stray light in the color separation and synthesis section.

[0096] (3) In the projection-type image display device of (1) or (2), the image forming element includes a third image forming element that forms an image, and the color separation and composition unit separates light from a light source into a first illumination light, a second illumination light, and a third illumination light with different wavelength bands using a first dichroic filter and a second dichroic filter, emits the first illumination light to the first image forming element, emits the second illumination light to the second image forming element, and emits the third illumination light to the third image forming element, thereby separating the first projection light reflected by the first image forming element and the second image form The second projected light reflected by the image forming element and the third projected light reflected by the third image forming element are combined, and the second dichroic filter reflects the third illumination light and the third projected light. The third incidence angle of the second illumination light to the second dichroic filter and the fourth incidence angle of the second projected light to the second dichroic filter are different, and the notch filter attenuates at least one of the light in the first wavelength band and the light in the second wavelength band, which includes the boundary between the wavelength band of the second illumination light and the wavelength band of the third illumination light.

[0097] With this configuration, even when the color separation and synthesis unit separates and synthesizes light from the light source into three colors, stray light can be reduced and heat generation can be decreased.

[0098] (4) In the projection-type image display device of (3), the notch filter is λ DM6 >λ NF4 , and, λ DM4 +λ DM6 / 4≦λ NF3 ≤λ DM5 -λ DM6 / 4(λ DM4 <λ DM5 (In the case of) or λ DM5 +λ DM6 / 4≦λ NF3 ≤λ DM4 -λ DM6 / 4(λ DM4 >λ DM5 In the case of λ, satisfying the condition DM4 λ is the wavelength at which the transmittance of light incident on the second dichroic filter at the third incidence angle is 50%. DM5 λ is the wavelength at which the transmittance of light incident on the second dichroic filter at the fourth incidence angle is 50%. DM6 is, λ DM4 and λ DM5 The wavelength width between λ NF3 λ is the center wavelength of the aforementioned second wavelength band of the notch filter. NF4 This is the full width at half maximum (FWHM) of the second wavelength band of the notch filter.

[0099] With this configuration, the notch filter can efficiently attenuate light in wavelength bands that would otherwise be stray light in the color separation and synthesis section.

[0100] (5) In any one of the projection-type image display devices described in (1) to (4), the notch filter is positioned on the incident surface of the light from the light source to the color separation and synthesis unit.

[0101] This configuration allows for efficient attenuation of light in wavelength ranges that could become stray light within the color separation and synthesis section.

[0102] (6) In any one of the projection-type image display devices described in (1) to (5), the image forming element is composed of a DMD (Digital Micromirror Device).

[0103] This configuration makes it possible to provide a compact projection-type image display device that prevents stray light from entering the image sensor.

[0104] (7) In any one of the projection-type image display devices described in (1) to (6), the light source emits visible light, and the visible light has continuous spectral characteristics.

[0105] This configuration allows for the projection of high-quality images. [Industrial applicability]

[0106] This disclosure is applicable to projection-type image display devices that project images. [Explanation of Symbols]

[0107] 1. Projection-type image display device 10 light source 106 Image forming elements 106B Image forming element (first image forming element) 106G Image Forming Element (Second Image Forming Element) 106R Image Forming Element (Third Image Forming Element) 135 Notch Filter 185 Red Reflective Dichroic Filter (First Dichroic Filter) 186 Blue Reflective Dichroic Filter (First Dichroic Filter) 330 Color separation / composition section 400 screens (projection targets) Ln1 First illumination light Ln2 Second illumination light Pn1 First projection Pn2 Second projection θ1 1st angle of incidence θ2 2nd angle of incidence θ3 3rd angle of incidence θ4 4th angle of incidence

Claims

1. A light source that emits light, An image forming element including a first image forming element that forms a first image and a second image forming element that forms a second image, A color separation and synthesis unit having a first dichroic filter that separates light from the light source into a first illumination light and a second illumination light having a wavelength band different from the wavelength band of the first illumination light, wherein the color separation and synthesis unit emits the first illumination light to the first image forming element and emits the second illumination light to the second image forming element, and synthesizes the first projected light reflected by the first image forming element and the second projected light reflected by the second image forming element, The system comprises a notch filter positioned between the light source and the color separation and synthesis unit, The first dichroic filter reflects the first illumination light and the first projection light, The first incident angle of the first illumination light to the first dichroic filter and the second incident angle of the first projection light to the first dichroic filter are different. The notch filter attenuates light in a first wavelength band that includes the boundary between the wavelength band of the first illumination light and the wavelength band of the second illumination light. λ ＤＭ１ λ ＤＭ２ If it is smaller than, the notch filter, λ ＤＭ３ >λ ＮＦ２ 、and, λ ＤＭ１ +λ ＤＭ３ / 4≦λ ＮＦ１ ≦λ ＤＭ２ -λ ＤＭ３ / 4 satisfies λ ＤＭ１ λ ＤＭ２ If it is greater than, the notch filter λ ＤＭ３ >λ ＮＦ２ , and, λ ＤＭ２ +λ ＤＭ３ / 4≦λ ＮＦ１ ≤λ ＤＭ１ -λ ＤＭ３ Satisfying / 4, λ ＤＭ１ This is the wavelength at which the transmittance of the first dichroic filter is 50% for light incident on the first dichroic filter at the first incident angle. λ ＤＭ２ This is the wavelength at which the transmittance of the first dichroic filter is 50% for light incident on the first dichroic filter at the second incident angle. λ ＤＭ３ is, λ ＤＭ１ and λ ＤＭ２ This is the wavelength range between, λ ＮＦ１ This is the center wavelength of the first wavelength band of the notch filter, λ ＮＦ２ This is the full width at half maximum (FWHM) of the first wavelength band of the notch filter. Projection-type image display device.

2. The wavelength band of the first illumination light is the red wavelength band, The wavelength band of the second illumination light is the green wavelength band. The projection-type image display device according to claim 1.

3. The aforementioned color separation and synthesis unit is A first prism facing the first image forming element, The device further comprises a second prism facing the second image forming element, The first dichroic filter is positioned between the first prism and the second prism, The projection-type image display device according to claim 2.

4. The notch filter attenuates light of the central wavelength of the first wavelength band by 20% or more. The projection-type image display device according to claim 1.

5. A light source that emits light, An image forming element including a first image forming element that forms a first image and a second image forming element that forms a second image, A color separation and synthesis unit having a first dichroic filter that separates light from the light source into a first illumination light and a second illumination light having a wavelength band different from the wavelength band of the first illumination light, wherein the color separation and synthesis unit emits the first illumination light to the first image forming element and emits the second illumination light to the second image forming element, and synthesizes the first projected light reflected by the first image forming element and the second projected light reflected by the second image forming element, The system comprises a notch filter positioned between the light source and the color separation and synthesis unit, The first dichroic filter reflects the first illumination light and the first projection light, The first incident angle of the first illumination light to the first dichroic filter and the second incident angle of the first projection light to the first dichroic filter are different. The notch filter attenuates light in a first wavelength band that includes the boundary between the wavelength band of the first illumination light and the wavelength band of the second illumination light. The image forming element further includes a third image forming element that forms a third image, The aforementioned color separation and synthesis unit further comprises a second dichroic filter, The first dichroic filter and the second dichroic filter separate the light from the light source into the first illumination light, the second illumination light, and the third illumination light having a different wavelength band from the wavelength band of the first illumination light and the wavelength band of the second illumination light. The color separation and synthesis unit emits the first illumination light to the first image forming element, emits the second illumination light to the second image forming element, and emits the third illumination light to the third image forming element, thereby synthesizing the first projected light reflected by the first image forming element, the second projected light reflected by the second image forming element, and the third projected light reflected by the third image forming element. The second dichroic filter reflects the third illumination light and the third projection light, The third incidence angle of the second illumination light to the second dichroic filter and the fourth incidence angle of the second projection light to the second dichroic filter are different. The notch filter attenuates light in the first wavelength band and light in the second wavelength band, which includes the boundary between the wavelength band of the second illumination light and the wavelength band of the third illumination light. λ ＤＭ４ λ ＤＭ５ If it is smaller than, the notch filter, λ ＤＭ６ >λ ＮＦ４ , and, λ ＤＭ４ +λ ＤＭ６ / 4≦λ ＮＦ３ ≤λ ＤＭ５ -λ ＤＭ６ Satisfying / 4, λ ＤＭ４ λ ＤＭ５ If it is greater than, the notch filter λ ＤＭ６ >λ ＮＦ４ , and, λ ＤＭ５ +λ ＤＭ６ / 4≦λ ＮＦ３ ≤λ ＤＭ４ -λ ＤＭ６ Satisfying / 4, λ ＤＭ４ This is the wavelength at which the transmittance of the second dichroic filter becomes 50% for light incident on the second dichroic filter at the third incidence angle. λ ＤＭ５ This is the wavelength at which the transmittance of the second dichroic filter becomes 50% for light incident on the second dichroic filter at the fourth incidence angle. λ ＤＭ６ is, λ ＤＭ４ and λ ＤＭ５ This is the wavelength range between, λ ＮＦ３ This is the center wavelength of the second wavelength band of the notch filter, λ ＮＦ４ This is the full width at half maximum (FWHM) of the second wavelength band of the notch filter. Projection-type image display device.

6. The wavelength band of the first illumination light is the red wavelength band, The wavelength band of the second illumination light is the green wavelength band, The wavelength band of the third illumination light is the blue wavelength band, The projection-type image display device according to claim 5.

7. The aforementioned color separation and synthesis unit is A first prism facing the first image forming element, A second prism facing the second image forming element, The device further comprises a third prism facing the third image forming element, The first dichroic filter is positioned between the first prism and the second prism, The second dichroic filter is positioned between the first prism and the third prism, The projection-type image display device according to claim 6.

8. The notch filter attenuates light of the center wavelength of the first wavelength band by 20% or more, and attenuates light of the center wavelength of the second wavelength band by 20% or more. The projection-type image display device according to claim 5.

9. The aforementioned notch filter is A first notch filter that attenuates light of the central wavelength of the first wavelength band by 20% or more, The system includes a second notch filter that attenuates light of the central wavelength of the second wavelength band by 20% or more, The projection-type image display device according to claim 8.

10. The full width at half maximum of the first notch filter is 25 nm or less. The full width at half maximum of the second notch filter is 25 nm or less. The projection-type image display device according to claim 9.

11. The color separation and synthesis unit has an incident surface into which light from the light source is incident, The notch filter is positioned on the incident surface of the color separation and synthesis unit. The projection-type image display device according to claim 1 or 5.

12. The image forming element is composed of a DMD (Digital Micromirror Device). The projection-type image display device according to claim 1 or 5.

13. The aforementioned light source emits visible light, The visible light has continuous spectral characteristics. The projection-type image display device according to claim 1 or 5.

Images