JP2007199538A - Projection-type video display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve cost reduction in a projection type video display device using a light-emitting diode as a light source. <P>SOLUTION: The projection type video display device comprises a blue light-emitting diode 1B or a near-ultraviolet light-emitting diode, and a reflecting mirror 7 in the opposite position. A fluorescent substance 6 is disposed in the location perpendicular to the diode 1B and the reflecting mirror 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention uses a light valve element such as a transmissive or reflective liquid crystal (Liquid Crystal on Silicon) panel image display element to project an image on a screen, such as a liquid crystal projector device or a reflective image. The present invention relates to a projection image display device such as a display projector device or a projection display device.

  Conventionally, a technique using a light emitting diode (hereinafter referred to as LED) as a light source in a projection display apparatus has been studied. Japanese Unexamined Patent Application Publication No. 2002-270020 discloses a technique using a blue LED and a phosphor as a white LED light source used for a backlight of a conventional display device. Moreover, as an example of the configuration of the projection type video display device, a projection type video display device using an LED light source is disclosed in Japanese Patent Laid-Open No. 2001-343706.

Japanese Patent Laid-Open No. 2002-270020 JP 2001-343706 A

  A conventional white LED light source has a resin layer in which a phosphor is distributed in the vicinity of a blue LED, and the blue LED and the phosphor are integrated. In the case of this configuration, forming the resin containing the phosphor in the vicinity of the blue LED has been a cause of high cost. Further, in order to reduce the variation in the color temperature of the light emitted from the white LED, it is necessary to disperse the phosphor as evenly as possible in the resin, which deteriorates the yield and causes a high cost.

  The light source unit according to one aspect of the present invention includes a light emitting diode, a reflective element at a position facing the light emitting diode, and a fluorescent element disposed at a position orthogonal to the light emitting diode and the reflective element.

  Cost reduction is realized with an LED light source or a projection-type image display device using the LED light source.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of an arrangement example of the blue LEDs 1. The light source unit used for a projection-type image display apparatus is shown.

  In FIG. 1 (a), a plurality of LEDs 1 are arranged at regular intervals. The reason why the constant interval is provided is to facilitate cooling. That is, the LED 1 is heated due to the heat generated by the LED 1 when the light is emitted. For cooling, the heat sink 2 is attached to the opposite side of the light emitting surface of the LED, but the cooling capacity is limited. Therefore, as in the present invention, LEDs are arranged at regular intervals to facilitate cooling. The amount of light emitted from the LED depends on the temperature, and decreases as the temperature increases. Therefore, here, the cooling is facilitated, the high temperature is prevented, and the amount of emitted light flux is increased.

  However, since the light source is scattered sparsely with a certain interval, when this light source is used as the light source of the projection type image display apparatus as shown in FIG. The use efficiency of is bad. Therefore, as shown in FIG. 1A, a polarization conversion element having a double pitch is disposed immediately after the LED. Thereby, the light is separated by the polarization separation film, divided into two optical paths, and the light can be developed densely. In addition, by performing polarization conversion, the light use efficiency can be doubled in a projection-type image display device using a polarizing plate and a liquid crystal panel. In other words, this configuration facilitates cooling and prevents high temperatures, thereby increasing the amount of emitted light flux of the LED. In addition, the light use efficiency can be increased by arranging the polarization separation elements by using an interval spaced for cooling.

  FIG. 1B is a configuration diagram of an embodiment of the present invention, and shows a light source unit used in a projection-type image display device. In the case of the configuration of FIG. 1B, one minute lens 4 a is used for two LEDs, and light condensed by the lens is incident on the polarization conversion element 3. This configuration is suitable when the amount of heat generated by the LED is small compared to FIG. Since the amount of generated heat is small, the LEDs can be arranged densely as compared with FIG. However, in this case, when the polarization conversion element is arranged immediately after the LED, the LED pitch is denser than the polarization conversion element, so that light from the LED cannot be taken into the polarization conversion element. The incident aperture of the polarization conversion element is every other pitch because of its configuration. That is, the light incident on the opening adjacent to the effective incident opening cannot be used effectively and becomes lost light. Therefore, as shown in FIG. 1B, a minute lens 4a is disposed between the LED and the polarization conversion element. That is, the light emitted from the LED is collected by the lens and enters the incident aperture of the polarization conversion element 3. Thereby, more light is taken in by the polarization conversion element, and the light use efficiency is improved.

  FIG. 1C shows another example of the light source unit used in the projection type video display device. This configuration is suitable for an LED having a wider light spread angle than in the case of FIG. For such LEDs, as shown in the figure, a lens is arranged and condensed, and then incident on the polarization conversion element, thereby increasing the amount of light taken into the polarization conversion element, Improve light utilization efficiency. Here, it arrange | positions so that the optical axis of a minute lens may come to the approximate center of LED. Thereby, the spot on the incident aperture of the polarization conversion element can be minimized, and the light capturing effect can be increased.

  Although not shown, when a vertically long LED is used, a cylindrical lens may be used instead of the lens. Since the polarization conversion element has a vertically long incident aperture, the number of lenses can be reduced and the cost can be reduced.

  Next, an embodiment of the optical unit in the present invention will be described with reference to FIG. FIG. 2A shows a projection-type image display apparatus using one transmissive liquid crystal panel as a light valve. As the light source, a B LED light source 1B that emits blue light is used. As the configuration of the light source unit, the LED light source having the configuration shown in FIG. 1 is used. The light emitted from the B LED light source travels through the light pipe 9 toward the transmissive liquid crystal panel 12, the reflection mirror 7 as a reflection element, or the phosphor 6 as a fluorescence element. The light traveling toward the reflection mirror 7 is reflected by the reflection mirror 7 and proceeds to the phosphor, the LED light source for B, or the transmissive liquid crystal panel.

  When blue light hits the phosphor 6, the phosphor is excited, and light in the range from green to red is emitted from the phosphor. This light mixes with the blue light from the B LED in the light pipe 9 to become white light. In this way, by creating white with a light pipe used to make the illuminance uniform, it is possible to cut a dedicated component for mixing colors, so that the size and cost of the apparatus can be reduced. Unlike normal white LEDs, the LED for B and the phosphor can be created separately, so there is no need to disperse the phosphor in the resin layer in the vicinity of the LED for B, and the process can be cut. Cost reduction is possible. Further, a general B LED can be used, and the phosphor can be made completely separately, so that the yield is improved and the cost can be reduced.

  The light traveling toward the transmissive panel is emitted with a substantially uniform illuminance distribution on the exit surface while being repeatedly reflected at the interface of the light pipe 9. The emitted light is aligned with the specific polarized light by an optical element that aligns polarized light, for example, the incident-side polarizing plate 10, and enters the electronic time-division optical characteristic switching element 11.

  The time division optical characteristic switching element 11 converts the output light having different polarization axes into a specific wavelength band and a wavelength band other than the specific wavelength band, and periodically switches the specific wavelength band. For example, the light emitted from the time-division optical characteristic switching element 11 is red for S-polarized light, blue and green for P-polarized light at a certain time, blue for S-polarized light for the next time, red and green for P-polarized light, and the next time. Thus, green is S-polarized light, blue and red are P-polarized light, and the above three states are periodically switched. In the subsequent optical path, only a specific polarization axis, here, S-polarized light is transmitted, and P-polarized light is incident on the incident-side polarizing plate 10 to reflect only red, then blue, and then green. Will do. Since the unnecessary color is S-polarized light, it is absorbed by the polarizing plate 10 and does not enter the liquid crystal panel 12. As described above, after time-division color separation is performed, the light irradiates the transmissive liquid crystal panel 12 which is a modulation element.

  The time-division optical characteristic switching element 11 has an R polarization rotation control element, a G polarization rotation control element, and a B polarization rotation control element for each color, and the polarization rotation control element has a specific wavelength region unless a voltage is applied thereto. The polarization axis of the light is converted, and when a voltage is applied, the polarization axis of the light is output without being converted. As a result, the time-division optical characteristic switching element 11 sequentially converts the polarized light of each color as R, G, and B. Here, since it is incident on the time-division optical characteristic switching element 11 as S-polarized light, G and B are converted into B-polarized light at the next timing, and R and G are converted into P-polarized light at the next timing and emitted.

  P-polarized light is transmitted and S-polarized light is absorbed by the incident-side polarizing plate 10 disposed on the emission side, so that it is emitted in the order of R, G, and B to the liquid crystal panel 12 side. A video for each color is displayed on the liquid crystal panel 12 in accordance with the timing of the color light irradiation. Since the switching timing of each color light is fast, an image projected on a screen (not shown) is displayed to human eyes as a combination of three color images.

  The liquid crystal panel 12 includes a number of liquid crystal display units corresponding to the pixels to be displayed (for example, horizontal 1024 pixels and vertical 768 pixels). Then, the polarization angle of each pixel of the liquid crystal panel 12 changes according to a signal input from the outside, and finally light that is orthogonal to the incident polarization direction is emitted, and the light having the same polarization direction is output side polarized light Light is detected by the plate 10 '. The amount of light passing through the exit-side polarizing plate 10 ′ and the amount of light that is detected (absorbed) are determined for light having polarized light at an intermediate angle depending on the degree of polarization of the exit-side polarizing plate 10 ′. In this way, an image according to the external signal is projected.

  Thereafter, the light that is the image passes through the projection lens 13 that is a zoom lens, for example, and reaches the screen. The image formed on the liquid crystal panel 12 by the projection lens 13 is enlarged and projected on the screen and functions as a display device.

  Thereby, the size can be reduced by using only the light source for B, and the cost can be reduced by eliminating the light sources for R and G. Further, since the light source is only for B, the amount of heat generation can be reduced. In addition, it is possible to reduce the size by reducing the volume of the heat sink and to reduce the noise by reducing the size of the cooling fan. Further, the cost can be reduced by not using the color synthesis component.

  FIG. 2B is a configuration diagram of another embodiment of the optical unit, and shows a projection type video display apparatus using one transmissive liquid crystal panel as a light valve. As the light source, a B LED light source 1B that emits blue light is used.

  The light emitted from the LED light source 1B enters the polarization separation element 8. Since the light emitted from the LED light source 1B is substantially elliptically polarized light, P-polarized light in the light passes through the polarization separating element film 8a and S-polarized light is reflected. The reflected S-polarized light is incident on the phosphor 6. When blue light hits the phosphor 6, the phosphor is excited, and light in the range from green to red is emitted from the phosphor. Of this light, only the P-polarized light passes through the polarization separation element 8 and enters the light pipe 9.

  Of the blue light, P-polarized light passes through the polarization separation film 8a, is reflected by the reflection mirror 7, and passes through the quarter-wave retardation plate 14 twice along the path, so that the polarization axis is 90 degrees. , Rotated and converted to S-polarized light. S-polarized light is reflected by the polarization separation film and enters the light pipe 9. The light beam in the light pipe is totally reflected at the interface when the incident angle is greater than or equal to the total reflection angle due to the difference in refractive index between the glass material and air. By repeating total reflection at the interface of the light pipe, the illuminance distribution on the emission surface is made substantially uniform and emitted. Further, the same effect can be obtained by using a mirror pipe that forms a cavity having a rectangular cross-section instead of a glass cuboid as the light pipe. The light is reflected by the inner reflecting surface a plurality of times, and the illuminance distribution on the emitting surface is made substantially uniform before being emitted. The mirror pipe is formed by bonding four mirrors with the reflecting surface inside.

  Blue light and red-green light incident on the light pipe are mixed in the process of being repeatedly reflected at the interface, and are emitted with a substantially uniform illuminance distribution on the exit surface. The light emitted from the light pipe enters the specific wavelength selective conversion wavelength plate. This specific wavelength selective conversion wavelength plate has a function of converting polarized light only by blue light and emitting red-green light as it is. Therefore, the blue light transmitted through the specific wavelength selective conversion wavelength plate is converted into P-polarized light and emitted. Further, red-green light is emitted as P-polarized light. Therefore, since the polarized light of all colors can be aligned with the P-polarized light, the light use efficiency can be improved without being cut by the polarizing plate.

  Thereafter, the light is incident on the reflective polarizing plate 10r that transmits only the P-polarized light, which is disposed to further increase the purity of the P-polarized light. The light emitted from the light enters the color switching element 11. The configuration and effects from the color switching element 11 to the projection lens 13 are the same as in FIG.

  In FIGS. 2A and 2B, the description has been made using the LED light source for B. However, the same effect can be obtained by using a near-ultraviolet light source instead. Further, although the light pipe is used as the integrator, it may be realized by a rod lens or a cylinder surrounded by a reflecting mirror.

  FIG. 3 is a block diagram showing an example of a projection type video display apparatus according to the present invention. A projection type image display apparatus using three transmissive liquid crystal panels as a light valve is shown.

  Here, the phosphor 6 is applied to the inner surface of the reflector 31. Blue light is emitted from the B LED light source 1B arranged at the focal position of the reflector. When this blue light strikes the reflector surface, the phosphor is excited and red to green light is emitted. Thereby, white light is formed together with the blue light emitted from the LED. Thereby, the size can be reduced by using only the light source for B, and the cost can be reduced by eliminating the light sources for R and G. Further, since the light source is only for B, the amount of heat generation can be reduced. In addition, it is possible to reduce the size by reducing the volume of the heat sink and to reduce the noise by reducing the size of the cooling fan.

  A first light source is formed by a plurality of condensing lenses provided in a rectangular frame having substantially the same size as the exit aperture of the reflector, and collects light emitted from the light source unit to form a plurality of secondary light source images. The first array lens 25 is formed on the liquid crystal panels 12R, 12G, and 12B, and is formed in the vicinity of the plurality of secondary light source images. Are transmitted through the second array lens 26 for forming individual lens images. This emitted light enters the polarization conversion element 27.

  A polarization separation film is provided on the prism surface, and incident light is separated into P-polarized light and S-polarized light by the polarization separation film. The P-polarized light passes through the polarization separation film and is emitted as it is. On the other hand, the S-polarized light is reflected by the polarization separation film, reflected once again in the original optical axis direction in the adjacent rhomboid prism, and then polarized by the λ / 2 phase difference plate provided on the exit surface of this prism. The direction is rotated by 90 °, converted into P-polarized light, and emitted. That is, P-polarized light is emitted from the polarization conversion element 3.

  The collimator lens 23 has a positive refracting power and has a function of condensing light. The light has its optical path bent by approximately 90 degrees by the reflection mirror 7, and the transmissive liquid crystal panels 12 R, 12 G, and 12 B of three colors RGB. Irradiate.

  The light transmitted through the collimator lens 8 is incident on a dichroic mirror 21 that transmits R light and reflects B light and G light. The R light transmitted through the dichroic mirror 21 is reflected by the reflection mirror 7, the optical path is changed by approximately 90 degrees, enters the condenser lens 24, and is condensed on the R transmission liquid crystal panel 12 </ b> R. The G light and B light reflected by the dichroic mirror 21 are incident on a dichroic mirror 22 that reflects G light and transmits B light. The G light reflected by the dichroic mirror 22 enters the condenser lens 24 and is condensed on the transmissive liquid crystal panel 12G for G. The B light transmitted through the dichroic mirror 22 is condensed on the B transmission type liquid crystal panel 12B via the relay lenses 30a, 30b, and 30c. In this apparatus, the contrast performance is ensured by the incident-side polarizing plates 10R, 10G, and 10B and the outgoing-side polarizing plates 10'R, 10'G, and 10'B for each color arranged so as to sandwich the video display element.

  Each color light transmitted through the transmissive liquid crystal panel enters the dichroic cross prism 28. Red light is reflected by the red reflecting film 28R, blue light is reflected by the blue reflecting film 28B, and green light is transmitted through the red reflecting film 28R and the blue reflecting film 28B. Each color light is synthesized by the dichroic cross prism 11, is emitted, and enters the projection lens 13. The image formed on the liquid crystal panel by the projection lens 13 is enlarged and projected on the screen to function as a display device.

  Moreover, in the said embodiment, although demonstrated using the LED light source as an example, an electrodeless light source (plasma light source) may be used and the same effect is acquired by combining with the optical structure of each embodiment.

  In addition, although the above-described light source has been described only in the embodiment used for the projection type image display device, the light efficiency can be improved or reduced even if the light source is used as a light source such as a near-eye display or a backlight for a mobile phone monitor. The effect of conversion is obtained.

It is a figure which shows an example of a light source unit. It is a figure which shows the other example of a light source unit. It is a figure which shows the other example of a light source unit. It is a figure which shows an example of an optical unit. It is a figure which shows the other example of an optical unit. It is a figure which shows an example of a structure of a projection type video display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... LED light source, 1R ... LED light source for R, 1G ... LED light source for G, 1B ... LED light source for B, 2 ... Heat sink, 3 ... Polarization conversion element, 3a ... Polarization separation film, 3b ... 1/2 wavelength phase difference Plate 4 4 Minute lens 5 Light beam 6 Phosphor 7 Reflecting mirror 8 Polarization separation element 8 a Polarization separation film 9 Light pipe 10, 10R, 10 G, 10 B Incident-side polarization Plate, 10 ', 10'R, 10'G, 10'B ... Emission side polarizing plate, 10r ... Reflective polarizing plate, 11 ... Electronic time-division optical characteristic switching element, 12, 12R, 12G, 12B ... Transmission Type liquid crystal panel, 13 ... projection lens, 14 ... specific wavelength selective conversion wavelength plate, 15 ... 1/4 wavelength phase difference plate, 21 ... red transmission color separation mirror, 22 ... blue transmission color separation mirror, 23 ... collimator lens, 24 ... Condenser lens, 25 ... First array lens 26 ... second array lens, 27 ... polarization conversion element, 28 ... cross dichroic prism, 28R ... red reflection film, 28B ... blue reflection film, 30a, 30b, 30c ... relay lens, 31 ... reflector

Claims (3)

A light emitting diode;
A reflective element disposed at a position facing the light emitting diode;
A fluorescent element disposed at a position orthogonal to the light emitting diode and the reflective element;
An integrator having an incident surface at a position facing the light emitting element;
A light valve that modulates the light emitted from the integrator;
A projection-type image display apparatus comprising a projection lens that projects light modulated by the light valve. In the projection type video display device according to claim 1,
A projection-type image display device comprising a polarization separation prism surrounded by three surfaces of the light-emitting diode, the reflective element, and the fluorescent element. In the projection type video display device according to claim 1 or 2,
The light emitting diode is a blue diode or a near-ultraviolet diode.

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