JPH07113708B2 - Projection display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a projection type display device using a plurality of image forming light valves.

[Conventional technology]

A conventional light valve type projection display device decomposes white light into colored light and image-modulates the colored light with a light valve as described in SID'86 Digest announcement number 20.4 (scheduled to be released on May 8, 1986). Then, there is one that synthesizes and projects the respective color lights.

[Problems to be solved by the invention]

As shown in FIG. 2, the conventional projection display device selects wavelengths of white light into color lights (here, red, green, and blue), and then combines them by a dichroic optical element having similar wavelength selection characteristics. It Since the light passes through the double wavelength selection element, the loss of the light amount increases at the tail of the selection characteristic. Second
FIG. 2A is a wavelength selection characteristic of the dichroic optical element, and FIG. 2B is an intensity spectrum of each color light after combination.
R, G and B indicate red, green and blue light. When the light quantity in the case of FIG. 2 (a) and the light quantity of FIG. 2 (b) are compared in lumen units and the light quantity loss is obtained, the loss is about 50%. The projection type display device using this coloring system has the drawbacks that the luminous flux utilization rate is low and the light source is heavily loaded for the reasons described above.

[Means for solving problems]

The projection type display device of the present invention is, firstly, an illumination system, a decomposing means for decomposing light from the illumination system into colored light, a light valve for modulating each colored light to form an image, and the modulated light. In a projection type display device having a combining means for combining the respective color lights and a projection optical system for projecting the combined light, a wavelength region in which the wavelength selection characteristic of the first optical element constituting the separating means transits. And the wavelength region in which the wavelength selection characteristics of the second optical element constituting the synthesizing means transit do not substantially overlap with each other.

Secondly, the first optical element and the second optical element are dichroic optical elements in which a coating layer having wavelength selection characteristics is formed.

Thirdly, the first optical element and the second optical element are characterized in that two kinds of coating layers having different wavelength selection characteristics intersect at right angles.

Fourthly, the first optical element or the second optical element has a coating layer that selectively reflects red light and / or blue light in the visible region.

Fifthly, the first optical element or the second optical element has a coating layer that selectively reflects yellow light and / or cyan light in the visible range.

Sixth, the first optical element or the second optical element has a wavelength selection characteristic for specific linearly polarized light.

Seventh, the light valve positioned between the optical paths of the first optical element and the second optical element is a light valve that modulates a specific polarization of the light flux that passes through the first optical element. Of the light flux reflected by the first optical element is a light valve that modulates polarized light perpendicular to the specific polarized light.

Eighth, the light valve located between the optical paths of the first optical element and the second optical element is a light valve that modulates a specific polarization of the light flux that passes through the second optical element. Of the light flux reflected by the second optical element is a light valve that modulates polarized light perpendicular to the specific polarized light.

[Action]

According to the above configuration of the present invention, the light of the specific wavelength is projected without being subjected to the wavelength selection action of the first optical element and the second optical element doubly. Figure 3 (a), (b), (c)
4 and FIG. 4 simply explain the operation. FIG. 4 is a block diagram showing the first optical element 101, the second optical element 102,
The light valve 103 and the reflection mirror 109 are the main components. The light source light 104 is decomposed into transmitted light 401 and reflected light 402 by the first optical element. The wavelength selection characteristic is shown in FIG. In FIG. 3A, 303 corresponds to transmitted light, 306 corresponds to reflected light, and 301 is a transition wavelength region of selection characteristics. Next, the transmitted light 401 and the reflected light 402 are modulated by the light valve, and the wavelength selection characteristics of the second optical element are shown in FIG. 3B, where 304 corresponds to transmitted light and 307 corresponds to reflected light. 302 is a transition wavelength region of selective characteristics. As shown in Fig. 3 (b)
301 and 302 have no overlap. As a result, the output light 403 after combination has the spectrum shown in FIG. Since the output light is not doubly affected by the wavelength selection action, it is not attenuated by the light intensity as shown in FIGS. 2 (a) and 2 (b).
In the case of FIG. 4, magenta light, which is a combined light of blue and red, is output. Here, if a light valve is provided between the optical paths of the first optical element and the second optical element to perform image modulation, multi-color display can be performed.

The first optical element having the wavelength selectivity as described above, the second
As the optical element, a dichroic optical element having a wavelength selective coating can be used.

If a first optical element having a coating layer for selectively reflecting red light and blue light and a second optical element having a coating layer for selectively reflecting yellow light and cyan light are adopted to realize full color display. Good. Also the first
The selection characteristics of the second optical element may be reversed. As a disposition of the coating layer, a cross-shaped disposition is advantageous in that the optical path length becomes short.

When a light valve that modulates light with respect to a specific polarized light is used, the color light incident on the second optical element is limited to a specific polarized light (for example, S polarized light, P polarized light) and is further transmitted with polarized light that is selectively reflected. The polarized light may be different polarized light. This prevents the wavelength selection characteristics of the first optical element and the second optical element from overlapping for the color light that is selectively reflected by the second optical element, and uses different polarizations for the color light that is transmitted next. This is a function to prevent the influence of the wavelength selective reflection characteristic.

〔Example〕

Example 1 Example 1 shows an example of a projection type display device for performing full color display. FIG. 1 is a block diagram thereof. The first optical element has a structure in which a blue (B) reflection dichroic mirror 101 and a red (R) reflection dichroic mirror 101 'are combined in a cross shape, and the second optical element is an S-polarized cyan (C). The reflection dichroic mirror 102 and the polarization yellow (Y) reflection mirror 102 'are combined in a cross shape. 104 is a white light source, 105 is a focusing lens, 106
Is a projection lens, 107 is a screen, and 109 is a mirror for folding the optical paths of blue (B) and red (R) light. Further, 103 is a light valve for image formation, and in this embodiment, a TN mode liquid crystal matrix type panel is used.

The light from the white light source 104 is collimated by the focusing lens 105 and enters the first optical element. The first optical element has a color light separation characteristic shown in FIG. 5 (a), and decomposes the source light into red (R), green (G), and blue (B) light. The red light and the blue light, which are the reflected and separated components, have at least the S-polarized component with respect to the dichroic mirror that is the first optical element. Next, the directions of the red light and the blue light are changed by the mirror 109 and enter the light valve 103. The green light enters the light valve as it is. Here, the light valve that modulates red and blue light has a polarizing plate Nicol arrangement that transmits S-polarized light in a transmissive state and the light valve that modulates green light transmits P-polarized light in a transmissive state. Therefore, the red light and the blue light always enter the second optical element as S-polarized light, and the green light enters P-polarized light.

Next, the second optical element is 102 S-polarized yellow mirrors and 1
Since it comprises the 02 'S-polarized cyan mirror, it has the reflection characteristic of FIG. 5B for S-polarized light and the transmission characteristic of the real image 501 of FIG. 5C for P-polarized light. That is, the second
The optical element of (1) acts as a yellow and cyan mirror only for S-polarized light and has a property of transmitting P-polarized light. The second optical element has characteristics shown in FIGS. 5 (a) and 5 (b) for blue light and red light, and real images shown in FIGS. 5 (a) and 5 (c) for green light. Color light synthesis is performed according to the characteristics of 501. Blue light and red light are the first of the combined light
The wavelength characteristic selected by the first optical element and the wavelength characteristic selected by the first optical element are retained for the green light. This is because the transition region of the wavelength selection characteristic of the first optical element and that of the second optical element do not substantially overlap with each other with respect to each color light. In other words, the light of the same wavelength is doubly selected. Because there is no.

With respect to the characteristics of the first optical element and the second optical element described in the present embodiment, a commercially available dichroic optical element composed of a dielectric multilayer film is realized, but since vibration due to interference actually occurs, it is strictly required. It is not necessary to reproduce the characteristics of FIG.
The present invention is applicable if the wavelength transition regions described above do not substantially overlap.

The second optical element has a flat transmission characteristic (see FIG. 5 (c)).
Although 501) is shown, an element having a selection characteristic as shown by a broken line 502 in FIG. Also in this case, for green light, the wavelength selection regions of the first optical element and the second optical element should not overlap.

Furthermore, when the color light separation characteristic shown in FIG. 5 (a) has a polarization dependence acting only on a specific polarized light, the transmitted light (in this case, green light) has a flat spectrum as shown by a broken line 503. have. In this case, it is effective to insert a filter for giving a spectrum of green light indicated by 504 between the optical paths of the first optical element and the second optical element to supplement the color light separating action of the first optical element. Also at this time, it is necessary that the filter characteristics and the wavelength selection transition region of the second optical element do not substantially overlap with each other.

By eliminating the overlap selection effect associated with color light separation and combination, the luminous flux loss, which was about 50% in the past, was 10
It was reduced to 30%, and when the same light source was used, the maximum increase of the projected luminous flux was observed.

Example 2 Example 2 is a projection type multi-color display device in which the first optical element for color light separation has a wide wavelength range and the second optical element for synthesis has a narrow wavelength range. FIG. 6 is a block diagram thereof. The light emitted from the light source 104 is collimated by the focusing lens 105 and decomposed by the first optical element 101.

The reflected component has its direction changed by the mirror 109 and enters the light valve 103. On the other hand, the transmitted component is directly incident on the light valve 103. Next, these are combined by the second optical element 102, pass through the projection lens 106, and form an image on the screen 107.

The separation characteristics of the first optical element are shown in FIG. 7 (a), and the composite characteristics of the second optical element are shown in FIG. 7 (b). In the first optical measurement, visible light is reflected around 550 nm, and cyan (C) light is reflected.
Transmits yellow (Y) light. On the other hand, the second optical element reflects blue (B) light and transmits red (R) light. For this reason, the light in the 500 to 550 nm region of the Y light and the C light is emitted outside the system as the leak light 601. The wavelength intensity distribution of the maximum output light after combination is as shown in FIG. 7 (c).

Thus, even when the selection wavelength range of the first optical element is wide and the selection wavelength range of the second optical element is narrow, the wavelength selection transition regions do not overlap each other, so that the color purity of red, blue, and black magenta is high. It was possible to obtain excellent multi-color display.

Here, when the separation wavelength range of the first optical element is the widest,
This is the case when it acts as a broadband polarized beam splitter. In FIG. 6, the first optical element reflects S-polarized light and passes P-polarized light. If the second optical element also operates in the same manner, the light loss after combination can be composed of two highly efficient light valve images in which the transmission loss in the light valve accounts for most. Further, by imparting wavelength selectivity to any one of the optical elements, it is possible to obtain a highly efficient color projection display. In other words, this is for synthesizing and disassembling optical elements, one of which is polarized light and the other of which is decomposed and synthesized based on wavelength. In particular,
This can be easily realized by using a polarization beam splitter for covering the visible light region in the first optical element in FIG. 6 and using a dichroic mirror in the second optical element.

〔The invention's effect〕

As described above, according to the present invention, the decomposition of the characteristics that the wavelength selection transition regions are not substantially overlapped with each other, the synthetic optical element is used, and further, the degree of freedom of the polarization property is added to the wavelength selection transition region. Thus, it is possible to obtain a highly efficient projection type display device without loss of luminous flux. Further, since one optical element determines the color reproduction characteristic, the other optical element does not need to have a sharp selection characteristic. Further, the cross-shaped arrangement can minimize the focus length to the light valve of the projection lens. This is an effect that simplifies the lens design.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a full-color projection type display device of the present invention. FIG. 2 (a) is the wavelength selection characteristic of the conventional optical element, and FIG. 2 (b) is the spectrum after its synthesis. FIGS. 3A and 3B show wavelength selection characteristics of the first optical element and the second optical element, respectively. FIG. 3 (c) is the spectrum after synthesis. FIG. 4 is a configuration diagram for explaining the operation. 5 (a) and 5 (b) respectively show wavelength selection characteristics of the first optical element and the second optical element of the full-color projection display device of the present invention. FIG. 5C shows the wavelength selection characteristic of the optical element of FIG. 2 for P-polarized light. FIG. 6 is a configuration diagram of the projection type multi-color display device of the present invention. 7 (a) and 7 (b) respectively show wavelength selection characteristics of the first optical element and the second optical element of the projection type multi-color display device of the present invention, and FIG. Is the spectrum of. 101,101 '... first optical element 102,102' ... second optical element 103 ... light valve 104 ... light source 106 ... projection lens 107 ... screen

Claims (8)

[Claims] 1. An illumination system, a decomposing means for decomposing light from the illumination system into color lights, a light valve for modulating each color light to form an image, and a combining means for combining the modulated color lights. And a projection optical system for projecting the combined light, a wavelength region in which a wavelength selection characteristic of the first optical element forming the decomposition means transits, and the combining means. A projection type display device characterized in that the second optical element does not substantially overlap with the wavelength region in which the wavelength selection characteristic transits. 2. The first optical element and the second optical element are dichroic optical elements in which a coating layer having wavelength selection characteristics is formed, and the first optical element and the second optical element are dichroic optical elements. Projection type display device. 3. The first optical element and the second optical element are characterized in that two types of coating layers having different wavelength selection characteristics intersect at right angles. The projection display device described. 4. The first optical element or the second optical element has a coating layer that selectively reflects red light and / or blue light in the visible region. The projection type display device according to item 1. 5. The first optical element or the second optical element has a coating layer that selectively reflects yellow light and / or cyan light in the visible range. The projection type display device according to item 1. 6. The projection display device according to claim 1, wherein the first optical element or the second optical element has a wavelength selection characteristic for specific linearly polarized light. . 7. The light valve located between the optical paths of the first optical element and the second optical element is a light valve that modulates a specific polarization of a light beam that passes through the first optical element. 2. The projection display device according to claim 1, wherein the projection type display device is a light valve that modulates, of the light flux reflected by the first optical element, polarized light perpendicular to the specific polarized light. 8. The light valve located between the optical paths of the first optical element and the second optical element is a light valve that modulates a specific polarization of a light beam passing through the second optical element. 2. The projection display device according to claim 1, wherein the projection type display device is a light valve that modulates polarized light perpendicular to the specific polarized light, of the light flux reflected by the second optical element.