JPH08292409A - Projector - Google Patents

Abstract

PURPOSE: To constitute a simple optical system, reduce the size of the projector, and facilitate its handling by enabling the projector to use both an electronic image of an electric signal and an enlarged image by an image sheet at the same time. CONSTITUTION: An image from an OHP sheet 91 is converged by a Fresnel lens 51 and made incident on a concave lens 41 on the bottom surface of the projection head part 30 of a transmission type OHP1. The incident light is made parallel through the concave lens 41 and made incident on a reflection type liquid crystal panel 11 formed of PDLC (high polymer distributed type liquid crystal) fitted at about 45 deg. from the incident direction. The incident light is reflected by an electronic image pattern displayed on the reflection type liquid crystal panel 11 at about 9 deg. from the incident direction to pass through a Schlieren optical system 21, so that it is enlarged and projected on the screen. When the reflection type liquid crystal panel 11 is placed in total reflection mode, a display dedicated to the OHP sheet 91 can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projector used in conferences and educational settings, and more particularly to a projector capable of obtaining a magnified image using an image sheet and a magnified image using an electronic image.

[0002]

2. Description of the Related Art Conventionally, an overhead projector (hereinafter referred to as OHP) that obtains an enlarged image of an image sheet (hereinafter referred to as OHP sheet) on a screen has been widely used in meetings and education. Recently, not only an enlarged image of an OHP sheet but also an electronic image of a computer, a television, a video, etc. is required to be enlarged and projected on a screen. Therefore, an OHP having both of the above functions has also been proposed (Japanese Patent Publication No. 4-53297, Japanese Patent Laid-Open No. 5-1650).
No. 19). The former technology displays an electronic image on a transparent TN (twisted nematic) liquid crystal panel, and
It is a substitute for a sheet, and the latter technique displays an electronic image using a reflective liquid crystal panel.
It is to substitute the HP sheet.

[0003]

However, in the above technique, a transmissive liquid crystal panel or a reflective liquid crystal panel having the same size as the OHP sheet is arranged instead of the OHP sheet on the stage on which the OHP sheet is placed. OHP
It is difficult to use at the same time as the seat. In addition, since the liquid crystal panel is optically used instead of the OHP sheet, the size thereof is about the same as that of the OHP sheet, which is large and difficult to use. Further special fairness 4-
In the technology of Japanese Patent No. 53297, since two deflecting plates are used for the liquid crystal panel, there is a problem that the brightness of the image is low and it is difficult to see.

Therefore, an object of the present invention is to obtain both a magnified image using an OHP sheet and a magnified image using an electronic image, simplify the structure of an optical system for obtaining a magnified image of an electronic image, and It is to miniaturize.

[0005]

In order to solve the above-mentioned problems, the structure of the present invention makes light emitted from a light source incident on an image sheet on which an image is recorded and collects light modulated by the image. Then, in the projector in which this light is reflected from the reflection plate toward the screen, and an enlarged image of the image is formed on the screen, the reflection plate reflects the incident light in the screen direction. ,
The state of not reflecting in that direction is configured by a liquid crystal panel that can be controlled for each pixel according to an external signal. Further, in the configuration of the related invention, the liquid crystal panel, a reflective electrode for reflecting the incident light in the screen direction,
A transparent electrode disposed to face the reflective electrode, and existing between the reflective electrode and the transparent electrode, and in accordance with the external signal applied between the two electrodes, a light transmission state and a light scattering state. It has a liquid crystal that takes advantage of. Furthermore, it is an optical means for projecting the light reflected by the reflecting plate to the screen to obtain the magnified image, wherein the scattered light generated by the light scattering state of the liquid crystal is projected to the screen. It is characterized in that it has diaphragm means for blocking light.

The present invention is also characterized in that the liquid crystal is a polymer dispersed liquid crystal (PDLC). The present invention is further characterized by having a cooling means for cooling the liquid crystal panel, or having a mechanism for mounting a reflecting mirror on the front surface of the liquid crystal panel.

[0007]

Operation: The projector allows the light from the light source to
The light is modulated by the image on the HP sheet), and the modulated light is condensed and reflected by the reflection plate, and is enlarged and projected on the screen. Since the reflector is composed of a liquid crystal panel that is controlled for each pixel according to an external signal, when the modulated light is incident and reflected, the image of the liquid crystal panel is further modulated. That is, the image on the OHP sheet and the image on the liquid crystal panel are superimposed. When the image display of the liquid crystal panel is set to the total reflection state, the mode for displaying only the image of the OHP sheet is set. If the light from the light source is incident on the reflector without the OHP sheet, only the electronic image of the liquid crystal panel is enlarged and projected.

According to the second aspect of the present invention, the reflection plate is composed of a transparent electrode and a reflection electrode sandwiching a liquid crystal, and is in a light transmitting state when energized and a light scattering state when not energized.
The electronic image displayed on the liquid crystal can be reflected when the light modulated by the image on the sheet is reflected. According to the configuration of claim 3, when the light modulated by the image on the OHP sheet is reflected by the reflector, the scattered light scattered by the light scattering state in the electronic image formed by the liquid crystal according to the external signal is screened. Since the diaphragm means that does not irradiate the light is provided, the difference in brightness can be increased.

In the structure of claim 4, since the liquid crystal of the reflection plate is a polymer dispersed liquid crystal (PDLC), an image with high brightness is formed in the reflection direction. In the structure of claim 5,
The liquid crystal panel is forced to dissipate heat to maintain a constant drive temperature and display a stable image. In the structure of claim 6,
Only the image of the OHP sheet is enlarged and projected without interrupting the display of the liquid crystal panel or energizing the liquid crystal panel.

[0010]

EFFECTS OF THE INVENTION Since the reflector may be a liquid crystal panel having only an area where the light modulated by the image of the OHP sheet is condensed and reflected, the OHP sheet can be made compact and compact.
Can be By simply displaying an electronic image on this small liquid crystal panel by an external signal, the display of this electronic image can be superimposed on the image of the OHP sheet, and both images can be projected brightly and easily. It becomes OHP. When the liquid crystal panel is set to the total reflection state, only the image on the OHP sheet can be enlarged and projected. Alternatively, without the OHP sheet, only the electronic image displayed on the liquid crystal panel can be enlarged and projected.

According to the structure of claim 2, since an electric image can be formed by utilizing the light transmitting state and the light scattering state by the reflecting plate, the electronic image can be easily displayed together with the image on the OHP sheet. It can be enlarged. In the structure of claim 3, since scattered light is cut, there is an effect that the contrast of the enlarged image can be increased.
According to the configuration of claim 4, the external information image can be displayed with higher brightness and higher contrast than the conventional liquid crystal panel, and a clear image can be obtained. Further, even in the case of the total reflection mode in which only the OHP sheet is displayed, the reflectance can be kept high and a bright projected image can be obtained.

According to the structure of claim 5, heat generation of the liquid crystal panel is suppressed, stable image display can be performed as an OHP, and the product life of the liquid crystal panel can be extended. According to the configuration of claim 6, since the reflecting mirror can be mounted even when the liquid crystal panel that plays the role of the reflecting mirror is not energized, the same OHP function as that of the conventional projection head unit can be provided, and the temporary liquid crystal panel display can be displayed. Even if you want to interrupt, you can enhance the expressive power by inserting a reflector and only displaying the OHP sheet.

[0013]

【Example】

(First Embodiment) The present invention will be described below based on specific embodiments. FIG. 1 shows a projector (O
It is sectional drawing which showed the typical structure of HP) 1. OHP 1
OHPs the Fresnel lens 51 with the light source unit 61 stored therein.
The table 60 includes a table 60 on which the sheet 91 is placed, and a projection head section 30 that is vertically movable and supported in a space above the Fresnel lens 51 by a column 62 provided on a part of the table. Here OHP 1 is transmissive.

As shown in FIG. 2, the projection head unit 30 includes a reflection type liquid crystal panel (hereinafter also referred to as a liquid crystal panel) 11 which is a reflector for collecting and reflecting light, and an OHP sheet on the bottom surface of the case 31. The concave lens 41 on which the light modulated by the image of 91 is condensed by the Fresnel lens 51 and is incident, the Schlieren optical system 21 for enlarging and projecting the reflected light from the liquid crystal panel 11, and the cooling fan 71 for cooling these. Consists of. An external information device 201 for displaying an electronic image by an external signal is displayed on the liquid crystal panel 11.
Are connected via a signal cable 202.

Incident light 301 which is incident and becomes parallel light
The size of the liquid crystal panel 11, the optical system of the Fresnel lens 51, the concave lens 41, and the like are determined so that the effective range of the liquid crystal panel 11 exactly overlaps the effective range of the liquid crystal panel 11. Since the required size of the OHP sheet 91 is predetermined, the optical system is determined so as to reduce the size to the effective area of the liquid crystal panel 11 by an appropriate lens design.

The schlieren optical system 21 is, as shown in FIG. 2, a reflected light 30 reflected from the reflective liquid crystal panel 11.
A condensing lens 22 for condensing 2 and a pinhole 23 for passing only necessary light out of the condensed light.
It is composed of a projection lens 24 for enlarging and projecting the light passing through 3 onto the screen.

A cooling fan 71, which is a cooling means for the projection head unit 30, cools the reflective liquid crystal panel 11 by air. Due to the ventilation, an air intake port 72 is provided on the bottom surface of the case 31, and an air exhaust port 73 is provided on the upper surface.

The reflection type liquid crystal panel 11 which is a reflection plate uses PDLC (polymer dispersed type liquid crystal) for the liquid crystal layer 10 and has the enlarged sectional view shown in FIG. In the PDLC, liquid crystal droplets 12 in which liquid crystals are fine particles are uniformly dispersed in a transparent polymer medium 13 and the liquid crystal layer 10 (1
It consists of 2 and 13). Liquid crystal layer 10
Is sandwiched between a transparent glass substrate 15 having a matrix of transparent electrodes 14 for applying an electric field to the liquid crystal layer 10 and a Si substrate 19 having a reflective electrode 17 which is a reflective surface, and the electric field is generated by these electrodes. It is adapted to be applied to the layer 10. On the surface of the Si substrate 19, MOSFETs 16 corresponding to each pixel 1: 1 are finely formed in a matrix. The matrix of the MOSFET 16 is formed by a semiconductor manufacturing process using Si as a substrate.

The PDLC shown here is a liquid crystal panel for color display in which a color filter 18 is provided on the reflective electrode 17. In this case, full color display is achieved by providing one color filter 18 for each of R, G, B on three adjacent MOSFETs 16 and displaying them as one set.

The OHP sheet 91 is placed on the upper surface of the Fresnel lens 51, and the light from the light source section 61 provided inside the base 60 for supporting the Fresnel lens 51 is applied to the OHP sheet 91 and condensed by the Fresnel lens 51. Light is OH
It is transmitted through the P sheet 91 and is modulated by the displayed image. The modulated light is condensed on the projection head unit 30 arranged above and is incident on the concave lens 41. Incident light 301 from the OHP sheet 91 is collimated by the concave lens 41 and is incident on the liquid crystal panel 11 which is a reflection plate.
Is incident as. The liquid crystal panel 11 is about 4 from the incident direction.
Since it is attached at an angle of 5 °, the reflected light 302 is reflected in the direction of about 90 ° from the incident direction, is condensed by the condenser lens 22, passes through the pinhole 23, and passes through the projection lens 24 to a screen (not shown). Enlarged and projected. By using such an optical system, only the necessary images are enlarged and projected,
Since excess light is cut off, the contrast is maintained high and the image is projected.

The reflection type liquid crystal panel 11 is provided with a signal cable 202 for an external information device 201 such as a personal computer or a video.
The electronic image from the external information device 201 is displayed by being connected via a connector (not shown). The external information device 201 may be any device as long as it can send a signal suitable for display control of the liquid crystal panel 11.

Since the principle and structure of the liquid crystal panel using PDLC are already known, only a brief explanation will be given. The liquid crystal panel 11 becomes transparent when an electric field is applied to the liquid crystal layer 10 and becomes a mirror which is reflected by the reflective electrode 17 behind the liquid crystal layer 10. That is, the MOSFET 16 is turned on, a voltage is applied to the reflective electrode 17, an electric field is applied between the MOSFET 16 and the transparent electrode 14 on the glass substrate 15 side, and the liquid crystal layer 10 becomes almost transparent (area of electric field ON in FIG. 4). This is because the liquid crystal droplets 1 dispersedly arranged in the liquid crystal layer 10 of the pixel to which the electric field is applied.
This is because the two orientations are aligned and the transmittance is increased, and the incident light 301 from the glass substrate 15 is almost totally reflected by the reflective electrode 17 to be reflected light 302 from the glass substrate 15 to the outside. Therefore, the pixels to which the electric field is applied are in a state of almost total reflection when viewed from the glass substrate 15 side. The liquid crystal layer 10 of the pixel to which the electric field is not applied (area where the electric field is OFF in FIG. 4) is the liquid crystal drop 1
Since the orientation of 2 remains oriented in various directions, the light transmittance is low, and the incident light 301 from the glass substrate 15 is regarded as scattered light 303, which remains dark as viewed from the glass substrate 1 side and has a low reflectance. .

The individual MOSFETs 16 forming each pixel form the contrast of light and dark as described above. Then, electronic image data is input as an external signal to a display control unit (not shown) attached to the liquid crystal panel 11, each MOSFET 16 of the pixels corresponding to the image data is on / off controlled, and an electronic image pattern is formed. The external signal to the liquid crystal panel 11 has a predetermined format, such as a video signal. Then, when the unmodulated incident light 301, which is parallel to the liquid crystal panel 11 arranged obliquely, is incident from the lower side, and seen from the direction in which the incident light is reflected,
An electronic image with a very high contrast is obtained.

As described above, the reflected light 302 reflected from the liquid crystal panel 11 on which the electronic image is displayed is modulated into the pattern of the electronic image. The parallel reflected light 302 including this electronic image pattern is condensed by the condensing lens 22, passes through the pinhole 23, and is enlarged and projected on a screen (not shown) by the projection lens 24. Although the scattered light 303 scattered by the liquid crystal droplets 12 is emitted from the dark portion of the image due to no electric field being applied, even if some of the scattered light 303 passes through the condenser lens 22, it is shown in FIG. As described above, the light cannot pass through the pinhole 23 unless it is parallel light. Therefore, the contrast of the image displayed on the liquid crystal panel 11 is kept high.

When using this OHP 1, therefore, there are the following three modes. (1) When displaying only the image of the OHP sheet All the MOSFETs 16 are turned on to apply an electric field to the pixels of the entire liquid crystal panel 11 to make the liquid crystal layer 10 of the entire panel transparent, and to make the entire liquid crystal panel 11 a reflective mirror. By doing so,
This is a mode in which only the image of the OHP sheet 91 is displayed.
In particular, PDLC has a high transparency of the liquid crystal layer 10 as compared with TN liquid crystal or the like, and therefore the reflectance of the liquid crystal panel 11 is also good, so that only the image of the OHP sheet 91 is projected brightly. Even if there is an RGB color filter 18 for each of the three MOSFETs, it will be the same as a white reflecting mirror because it will represent white as a whole by combining three MOSFETs, and only the OHP sheet is displayed. Let Alternatively, if the structure is such that an ordinary plane mirror is attached to the front surface of the liquid crystal panel 11, it becomes a reflecting mirror simply by attaching the plane mirror, and only the image of the OHP sheet 91 is displayed regardless of the state of the liquid crystal panel.

(2) Displaying only the electronic image of the liquid crystal panel If the light from the light source is directly incident on the projection head unit 30 without the OHP sheet 91, the incident light 301
Is modulated by the electronic image pattern when reflected by the liquid crystal panel 11, it is possible to magnify and project only the electronic image of the liquid crystal panel 11.

(3) When the image on the OHP sheet and the electronic image on the liquid crystal panel are displayed in a superposed manner The parallel light incident on the liquid crystal panel 11 is originally modulated by the image pattern on the OHP sheet 91. Therefore, when the liquid crystal panel 11 is irradiated with the incident light 301 modulated by the image of the OHP sheet 91, it is further modulated by the electronic image pattern when reflected by the liquid crystal panel 11, so that two images can be easily formed. Can be synthesized.

In the projection head section 30 shown here, the liquid crystal panel 11 is cooled by the cooling fan 71.
When the liquid crystal panel 11 has the color filter 18, not only the light from the light source unit 61 is almost equal to white light, but also infrared light is included. The visible light portion is also absorbed as heat except for the wavelength component of the filter. Therefore, as in the case of a liquid crystal panel having a full-color configuration, since the RGB filter reflects the energy of white light to about 1/3 and reflects it, 2/3 of the energy is generated in the liquid crystal panel 11 as heat. become. Therefore, a mechanism for forcibly cooling the liquid crystal panel 11 is provided. As shown in FIG. 3, in the case of air cooling, the hot air escapes upward, so the outside air is taken in from the air intake port 72 provided on the bottom surface of the case 31 of the projection head unit 30, and the air exhaust port 7 on the upper surface side.
The cooling fan 71 is operated so as to exhaust the air from No. 3, so that the air flow 601 becomes natural.

The liquid crystal panel 11 is cooled by the liquid crystal panel 11
In the case of (3), the display pattern portion that disperses the light easily absorbs the light as heat, and particularly in the case of color display, the color filter absorbs the light and generates heat, so that it is preferable. The cooling by the cooling fan 71 introduces outside air into the projection head unit 30 from below,
Efficiently discharge warm air from above. However, the mechanism for cooling the liquid crystal panel 11 does not have to be air cooling, and the back surface and the peripheral portion of the liquid crystal panel 11 may be directly cooled by liquid cooling or electronic cooling. In that case, there is an advantage that the large cooling fan 71 need not be provided, and there is an advantage that quietness is maintained.

The OHP projection head section 30 using the reflection type liquid crystal panel 11 having the structure of the present invention may be as large as a conventional one, and the liquid crystal panel 11 itself can be made small. Conventionally, it was expensive and not easy to handle because it was composed of an OHP sheet-sized liquid crystal panel, but a small liquid crystal panel is easy to manufacture and easy to handle. It can also be used in three modes: a mode that uses only the OHP sheet, a mode that magnifies and projects only the electronic image, and a mode that magnifies and projects both images at the same time. In addition, PDLC has high image brightness and can obtain good image quality even in bright surroundings, improving the presentation effect.

(Second Embodiment) FIG. 5 is a schematic sectional view of a structure in which the projection head unit 30 of the present invention is applied to a reflection type OHP 2. In the reflection type OHP, the light source 501 for the OHP sheet 91 is arranged not at the lower side of the OHP sheet 91 but at the upper side of the projection head unit 30. Therefore, the reflection type OHP does not require the large pedestal 60 having the light source unit 61 shown in FIG. 1, and has a compact structure. The OHP sheet 91 is irradiated from the light source 501 provided on the upper part, and the image of the OHP sheet 91 is condensed on the projection head unit 30 by the Fresnel lens 51 which also serves as a reflection plate. OHP sheet 91
After the image is collected and incident on the concave lens 41, the description is omitted because it is the same as in the first embodiment.

(Third Embodiment) If a reflecting mirror can be attached to the front surface of the liquid crystal panel 11, the liquid crystal panel 11 will be described.
It is possible to set the display mode only for the OHP sheet without driving. In order to bring the liquid crystal panel 11 into the total reflection state, it is necessary to apply an electric field to all the pixels, and power is consumed. Therefore, it is possible to save the power consumption of the liquid crystal panel 11 only by installing the reflecting mirror.

Although not shown in FIGS. 1 and 2, the schlieren optical system 21 is provided with a zoom function or the like for adjusting the focus of the enlarged and projected image. The focus adjustment of the OHP image is also performed by a fine adjustment mechanism that moves the projection head unit 30 up and down.

[Brief description of drawings]

FIG. 1 is a schematic configuration sectional view showing an OHP according to a first embodiment.

FIG. 2 is a schematic configuration sectional view of a projection head unit.

FIG. 3 is an explanatory diagram of cooling the projection head unit.

FIG. 4 is a schematic cross-sectional view showing an enlarged configuration of a reflective liquid crystal panel using PDLC.

FIG. 5 is a schematic structural cross-sectional view showing an OHP according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 OHP (transmissive type) 2 OHP (reflective type) 10 Liquid crystal layer (PDLC consisting of 12, 13) 11 Reflective liquid crystal panel 12 Liquid crystal droplets 13 Polymer medium 21 Schlieren optical system (consisting of 22, 23, 24) 30 Projection Head

Claims (6)

[Claims] 1. A light emitted from a light source is incident on an image sheet on which an image is recorded, the light modulated by the image is condensed, and the light is reflected from a reflecting plate toward a screen to obtain the image. In the projector configured to form the enlarged image of the image on the screen, the reflector has a state in which the incident light is reflected in the screen direction and a state in which the incident light is not reflected in the screen direction according to an external signal. A projector comprising a liquid crystal panel that can be controlled for each pixel. 2. The liquid crystal panel is provided between a reflective electrode that reflects the incident light in the screen direction, a transparent electrode that faces the reflective electrode, and the reflective electrode and the transparent electrode. The projector according to claim 1, further comprising a liquid crystal that is in a light transmitting state or a light scattering state according to the external signal applied between both electrodes. 3. An optical means for projecting the light reflected by the reflector to the screen to obtain the magnified image, wherein the scattered light generated by the light scattering state of the liquid crystal is directed to the screen. The projector according to claim 2, further comprising a diaphragm unit that blocks the projection of the light. 4. The polymer-dispersed liquid crystal (PDL)
The projector according to claim 2, wherein the projector is C). 5. The projector according to claim 1, further comprising cooling means for cooling the liquid crystal panel. 6. The projector according to claim 1, wherein the liquid crystal panel has a mechanism for mounting a reflecting mirror on the front surface.