KR20070095688A - Optical lighting system - Google Patents

Abstract

An illumination optical system is provided to remove light of an unnecessary wavelength and increase purity and contrast of color by forming a dichroic coating layer having a transmitting or reflecting characteristic for light of a specific wavelength on a surface of a polarization conversion unit. An illumination optical system includes an optical source(21), at least one display panel(27a,27b,27c), at least one polarization conversion unit(26a,26b,26c) and a dichroic coating layer(23). The optical source(21) emits light. The display panel(27a,27b,27c) transmits image information to the emitted light. The polarization conversion unit(26a,26b,26c) is installed on a path of the light toward the display panel(27a,27b,27c), and converts the light which is incident on the display panel(27a,27b,27c), and a polarization direction of the light which is reflected from the display panel(27a,27b,27c). The polarization conversion unit(26a,26b,26c) has the dichroic coating layer(23) with a different transmittance according to a wavelength.

Description

Lighting optical system {Optical Lighting System}

1 is a diagram schematically illustrating the structure of a conventional reflective 3-plate optical system.

2 is a diagram schematically showing an embodiment of a reflective illumination optical system according to the present invention.

3 is a view showing the operation of the polarization converting unit constituting an embodiment of the present invention.

4A, 4B, and 4C are diagrams illustrating characteristics of a dichroic coating film of a polarization converting unit constituting an embodiment of the present invention.

5A and 5B illustrate a blocking path of yellow light according to still another embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

21: light source 22a, 22b: fly-eye lens

23, 33: dichroic mirror 24, 34: color select

25,35: polarization splitting prism 26,36: polarization converting unit

27,37: display panel

TECHNICAL FIELD The present invention relates to a reflective illumination optical system, and more particularly, to an illumination optical system that is structurally simple and has high optical performance such as color purity and contrast.

Recently, display devices have been placed in a trend toward larger screens as well as weight reduction and thinning. In particular, a large screen display device has emerged as an important problem in the display field, and one of those developed as such a large display device is a projector.

Projectors, such as large-screen display devices, are classified into two types, cathodic-ray tube (CRT) projectors and liquid crystal display (LCD) projectors, according to display elements. Among them, the liquid crystal display projector is further classified into a system using a transmissive liquid crystal display and a system using a reflective liquid crystal display (Lcos). Reflective liquid crystal displays are often used because of the advantage that the panel can be manufactured at a low cost compared to the transmissive type. In addition, the liquid crystal display projector is further classified into one plate type, two plate type, and three plate type according to the number of panels used. If the number of the panels used is large, the volume of the whole optical system is increased, and the liquid crystal display (LCD) panel is very expensive, which causes the price of the product to increase.

1 is a diagram schematically illustrating the structure of a conventional reflective 3-plate optical system. As shown, the light emitted from the lamp 1 passes through a dichroic mirror, a polarized beam splitter (PBS), and a synthetic prism and is separated and synthesized to convey image information. . Looking at this in detail.

The light emitted from the light source 1 is focused by the focusing lens and passes through the first dichroic mirror 2. The first dichroic mirror reflects red light (R), green light (G), and transmits blue light (B). The reflected red light R and green light G pass through the second dichroic mirror 3. In this case, the second dichroic mirror 3 reflects the green light G and transmits the red light R. Through this, the red light (R), green light (G), and blue light (B) are polarized separation prisms (Polarized) positioned in front of the red (R), green (G), and blue (B) display panels 5a, 5b, and 5c, respectively. Beam splitter (PBS).

In this case, the polarization splitting prism passes only a part of the linearly polarized wavelengths. For example, when dividing P polarization and S polarization according to the polarization direction, the polarization separation prism passes only the P polarization and reflects the S polarized light. Through this, it is possible to adjust the traveling direction of the light according to the polarization direction. In this case, the P polarized light and the S polarized light have a difference of 90 degrees.

Light (R, G, B) of each wavelength band incident on the polarization split prism (4a, 4b, 4c) is reflected and incident on the panels (5a, 5b, 5c), respectively. The light incident on the panels 5a, 5b, and 5c is reflected and the phase is changed. That is, the red light R passing through the second dichroic mirror 3 is reflected by the first polarization splitting prism 4a and is incident on the red display panel R LCD 5a. The light incident on the red display panel 5a is reflected and the polarization direction is changed. That is, the incident red light R of the S-polarized light is reflected and converted into P-polarized light and passes through the first polarization splitting prism 4a. As described above, the green light G of the S-polarized light reflected by the second dichroic mirror 3 is reflected by the second polarization separation prism 4b and is incident on the green display panel G LCD.

The green light G containing the image information is reflected and converted into P-polarized light so that it passes through the second polarization separation prism 4b. The blue light B of polarized light passing through the first dichroic mirror 2 and reflected on the mirror is reflected by the third polarization split prism 4c and is incident on the blue display panel B LCD. The reflected light is also P-polarized and passes through the third polarization separation prism 4c.

Through this, the red (R), green (G), and blue light (B) containing the image information in each display panel (5a, 5b, 5c) are synthesized by the synthesis prism 6 to include a projection unit (not shown) Incident). Through this, a large screen image can be realized.

However, the three-plate optical system is composed of one step by a light source and a dichroic mirror, two steps by a green display panel and a polarization separator, and three steps by a red and blue display panel, a synthetic prism and a polarization separator. There was a problem that the optical path of the entire system is long.

In addition, since a large number of components, such as a plurality of dichroic mirrors and polarization splitters, are required in the configuration, the configuration of the optical system is complicated, the size thereof becomes large, and there is a problem in that it is economically burdensome.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an illumination optical system having a simple configuration and high optical performance such as color purity and contrast while having a small size of the optical system. .

According to a feature of the present invention for achieving the above object, the present invention provides a light source for emitting light and at least one display panel for transmitting image information to the emitted light and on the path of the light directed to the display panel. And at least one polarization conversion unit for converting polarization directions of the light incident to the display panel and the reflected light, wherein some or all of the polarization conversion units have a dichroic coating film having a difference in transmittance according to a wavelength. It is characterized by including.

Preferably, the dichroic coating layer is characterized in that the light of the wavelength to be incident to the display panel transmits and the light of the other wavelengths is reflected.

Preferably, the polarization converting part may include a second wavelength conversion surface provided on a path through which light of a first wavelength is incident to the first display panel and a second provided on a path through which light of a second wavelength is incident to the second display panel. It includes a wavelength conversion surface, and according to the transmittance according to the wavelength of the dichroic coating film of the first wavelength conversion surface and the dichroic coating film of the second wavelength conversion surface, it is characterized in that to block the light of the unused wavelength It is done.

Preferably, the illumination optical system includes a red display panel, and the dichroic coating layer of the first polarization conversion surface provided on a path of light directed to the red display panel has a high transmittance of red light. In addition, the display device further includes a green display panel, and the dichroic coating layer of the second polarization conversion surface provided on the path of light directed to the green display panel has high transmittance of blue and green light.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of the illumination system according to the present invention will be described in detail.

2 is a diagram schematically showing an embodiment of an illumination optical system according to the present invention. As shown, the illumination optical system according to the present invention includes light sources 21, fly-eye lenses 22a and 22b, dichroic mirrors 23, color selects 24a, 24b and 24c, and polarization splitting prisms 25a and 2b. And 25c), polarization converters 26a, 26b, and 26c, and display panels 27a, 27b, and 27c.

The fly's eye lenses 22a and 22b convert incident light into linearly polarized light. That is, the first fly's eye lens 22a splits incident light into cells so that the first fly's eye lens 22a is focused on each lens cell of the second fly's eye lens 22b. The second fly's eye lens 22b converts the incident light into parallel light with respect to a specific portion, and converts the light into linearly polarized light having one optical axis, that is, P-polarized light and S-polarized light. At this time, the P-polarized component is converted so that all incident light becomes S-polarized light.

The dichroic mirror 23 has a property of transmitting or reflecting light of a specific wavelength according to its characteristics. Through this, each color may be separated in the visible light region using the wavelength difference.

The color selects 24a, 24b, and 24c convert polarization directions of specific wavelength light according to their characteristics. For example, when S-polarized light of white light is incident, the polarization direction of some wavelengths is converted according to its characteristics.

The polarized beam splitter (PBS) passes only a portion of the linearly polarized wavelength. That is, most of the horizontally polarized light is transmitted by the polarization splitting prism, but most of the vertically polarized light is reflected. For convenience, when it is divided into P-polarized light and S-polarized light, the polarization splitting prism passes only P-polarized light and reflects S-polarized light. Through this, it is possible to adjust the traveling direction of the light according to the polarization direction. At this time, the P-polarized light and the S-polarized light have a difference of 90 degrees in the vibration direction.

The polarization converters 26a, 26b, and 26c / are referred to collectively as 26, respectively, and are provided on the front of each display panel 27a, 27b, and 27c /, collectively referred to as 27. Convert. In this case, preferably, the polarization converter 26 is a quarter wave plate.

3 is a view showing the operation of the polarization converting unit constituting an embodiment of the present invention. As illustrated, light incident through the polarization converter 26 and incident on the display panel 27 is reflected by the display panel 27 and passes through the polarization converter 26 again.

In this process, in the case of the light circularly polarized by the quarter wave plate, once the quarter wave plate is transmitted again, the polarization direction is changed perpendicularly to the original polarization direction. That is, as illustrated, the polarization converter 26 polarizes the incident light to the left circle and unilaterally polarizes the reflected light. Therefore, the light reflected by the polarization converting unit 26 and the display panel 27 is perpendicular to the incident light. Therefore, when P polarized light is incident, the reflected light becomes S-polarized light, and when S polarized light is incident, the reflected light is P-polarized light.

At this time, the illumination optical system according to the present invention forms a dichroic coating film on the surface of the polarization converting portion 26 to remove light of unnecessary wavelengths. That is, it is intended to increase color purity and contrast by providing a dichroic coating film having a property of transmitting or reflecting light of a specific wavelength to remove light of unnecessary wavelengths.

4A, 4B, and 4C are diagrams illustrating characteristics of a dichroic coating film of a polarization converting unit according to an embodiment of the present invention. FIG. 4A illustrates the characteristics of the dichroic coating layer of the first polarization conversion unit 26a provided on the path of the red light R toward the red display panel 27a. As shown, the transmission of the red (R) wavelength is high and the transmission of the blue (B) and green (G) is very low.

FIG. 4B illustrates the characteristics of the dichroic coating film of the second polarization converting part 26b provided on the path of the green light G toward the green display panel 27b. As shown, the transmittance of the blue (B) and green (G) wavelengths is high and the transmittance of the red (R) is very low.

4C illustrates the characteristics of the dichroic coating film provided in the first polarization converting unit 26a and the second polarization converting unit 26b as described above. That is, as shown, the transmittance in the yellow (Yellow, Y) wavelength range is very low. This provides an optical system having the same effect without using a notch filter for yellow light (Y). That is, by providing the dichroic coating film as described above, the color purity and contrast of the red light and the green light are improved.

In another embodiment of the present invention, a dichroic coating layer is formed on the second polarization converter 26b and the third polarization converter 26c disposed on the front surface of the blue display panel 27c and the green display panel 27b. Cyan (C) light can be blocked. In this case, the color purity and contrast of the blue (B) and green (G) light may be improved by blocking cyan (Cyan, C) light by the characteristics of the dichroic coating film.

5A and 5B illustrate a blocking path of yellow light according to still another embodiment of the present invention.

Fig. 5A shows the path of light incident on this embodiment. For the convenience of explanation, S polarization is indicated by a dotted line and P polarization is indicated by a solid line. As shown, the incident white polarized light of S-polarized light is transmitted through the blue light B by the dichroic mirror 33 and the red light R and the green light G are reflected. The reflected red (R) and green light (G) is incident to the first color select 34a. The first color select 34a converts the red light R into P-polarized light and travels straight through the polarization splitting prism. The green light of the S-polarized light is reflected by the first polarization split prism 35a and proceeds. At this time, the dichroic coating film is provided on the polarization conversion part provided in the traveling path to remove unnecessary wavelength light.

That is, the transmittance of the red (R) wavelength is high and the transmittances of the blue (B) and green (G) are high in the first polarization converter 36a provided on the path of the red light R toward the red display panel 37a. Prepare a dichroic coating film to be very low. In addition, the transmittance of the blue (B) and green (G) wavelengths is high and the transmittance of the red (R) is very high in the second polarization converter 26b provided on the path of the green light G toward the green display panel 27b. Provide a low dichroic coating.

5b shows the path of the yellow light Y being blocked. As shown, when a part of the yellow light is P-polarized converted to the red display panel 37a, it is reflected by the dichroic coating film provided in the first polarization converting unit 36a. The yellow (Y) light of the reflected P-polarized light passes through the first polarization splitting prism 35a and is converted into S-polarized light by the first color select 34a. The yellow light of the converted S-polarized light is reflected by the dichroic mirror 33 and emitted.

In addition, when a part of the yellow light of the S-polarized light incident from the light source is directed to the green display panel 37b, it is reflected by the second dichroic coating film provided in the second polarization converting unit 36b. The yellow (Y) light of the reflected S-polarized light is reflected back to the first polarization splitting prism 35a and reflected by the dichroic mirror 33 to be emitted. This improves the purity and contrast of red (R) and green (G) light by blocking yellow (Y) light that is not needed.

Hereinafter, the operation of the illumination optical system according to the present invention will be described in detail.

As shown in FIG. 2, the white light emitted from the light source 21 passes through the fly's eye lenses 22a and 22b and is focused by the condenser lens. At this time, the white light polarized by the fly-eye lenses 22a and 22b is focused by the focusing lens and separated by the dichroic mirror 23 according to the wavelength. That is, the dichroic mirror 23 has a property of transmitting red (R) and green (G) light and reflecting blue (B) light. Through this, the red (R) and green (G) light transmitted through the dichroic mirror 23 is incident to the first color select 24a. The first color select 24a converts the red light R into P-polarized light.

The converted light is incident on the first polarization splitting prism 25a. At this time, red light R that is P-polarized light is transmitted and green light G that is S-polarized light is reflected. The separated red light R and green light G are incident on the red and green display panels 27a and 27b, respectively, and are reflected with image information.

In this case, the polarization converters 26a and 26b are provided in the optical paths toward the display panels 27a and 27b. That is, the first polarization converting section 26a and the second polarization converting section 26b are provided, and each polarization converting section includes the dichroic coating film as described above. Therefore, the first polarization converter 26a passes only the red light R and the second polarization converter 26b passes only the green light R. Through this, yellow (Y) light that is not necessary can be removed.

The red light R of P-polarized light incident on the red display panel 27a is reflected by image information and converted into S-polarized light by the polarization converter 26a. Therefore, the reflected red light R of the polarized light is reflected by the first polarization splitting prism 25a and enters the second color select 24b.

As in the case of the red light R, the green light G of the S-polarized light reflected by the first polarization split prism 25a is incident on the green display panel 27b and reflects the image information. At this time, it converts into P-polarized light by the 2nd polarization conversion part 26b provided on the path | route. Therefore, the reflected green light G of P-polarized light passes through the first polarization splitting prism 25a.

The red light (R) and green light (G) containing the image information are incident on the first polarization split prism (25a), the red light (R) is reflected and the green light (G) is transmitted. This outputs the same direction to the second color select 24b. The second color select 14b polarizes only the green light G to the S polarized light.

The blue light B reflected by the dichroic mirror 23 is incident and reflected by the second polarization split prism 25b. In this case, a third polarization converter 26c is provided on the optical path. As a result, the blue light B incident on the blue display panel 27c is reflected into the P-polarized light while containing the image information. Therefore, the reflected blue light B passes through the second polarization separation prism 25b and enters the third color select 24c. The third color select 24c converts the blue light B into S-polarized light. Therefore, blue light is reflected by the third polarization separation prism 25c and output in the same direction as the red (R) and green (G) light.

As a result, the red (R), green (G), and blue (B) lights all have the same polarization direction by the third polarization separation prism 15c, and are output in the same direction and synthesized. That is, the light is separated and synthesized according to the polarization direction by the polarization separation prism and incident on the projection unit (not shown) including the projection lens.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and those skilled in the art can make various modifications and adaptations within the scope of the claims. It is self-evident.

In the reflective illumination optical system according to the present invention as described in detail above, the following effects can be expected.

That is, there is an advantage in providing an illumination optical system having high optical performance such as color purity and contrast at a simple configuration and low cost.

Claims (5)

A light source for emitting light; At least one display panel transferring image information to the emitted light; And And at least one polarization converting unit provided on a path of light directed toward the display panel to convert a polarization direction of light incident to the display panel and reflected light. Part or all of the polarization converting unit is provided with a dichroic coating film having a difference in transmittance according to wavelengths. The method of claim 1, wherein the dichroic coating film, Illumination optical system, characterized in that for transmitting the light of the wavelength to be incident to the display panel, and reflects light of other wavelengths. The method of claim 1, wherein the polarization converter, A first wavelength conversion surface provided on a path through which light of a first wavelength is incident on the first display panel; And a second wavelength conversion surface provided on a path through which light of a second wavelength is incident on the second display panel. An illumination optical system according to claim 1, wherein light corresponding to a wavelength of the dichroic coating film of the first wavelength conversion surface and the dichroic coating film of the second wavelength conversion surface is blocked according to the wavelength. The method of claim 1, wherein the illumination optical system, And a red display panel, wherein the dichroic coating layer of the first polarization conversion surface provided on the path of light directed to the red display panel has a high transmittance of red light. The method of claim 4, wherein the illumination optical system, And a green display panel, wherein the dichroic coating film of the second polarization conversion surface provided on the path of light directed to the green display panel has high transmittance of blue and green light.

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