JPH08339034A - Liquid crystal display device for overhead projector - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display device for an overhead projector in which the amt. of cooling air is controlled according to the temp. increase of a liquid crystal cell in the liquid crystal display device and the noise due to the air blow is rendered as barely audible, and to prevent the temp. increase itself. CONSTITUTION: The liquid crystal display device is equipped with a transmission type liquid crystal cell 1, a lower protective panel 2 disposed near the light source part of an overhead projector 30 and apart from the cell 1 at a specified distance, and a cooling means 3 to blow cooling air into the space between the transmission type liquid crystal cell 1 and the lower protective panel 2, a temp. detector 4 to detect temp., and a noise detector 5 to detect noise around the liquid crystal display device 10. In this device, the amt. of the cooling air is controlled according to the detection results of the temp. detector 4 and the noise detector 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for an overhead projector, which mainly utilizes light from a light source section of an overhead projector to enlarge and project image information driven by a transmissive liquid crystal cell on a screen.

[0002]

2. Description of the Related Art In recent years, various companies have commercialized a liquid crystal display device for displaying an image of a personal computer or the like on a transmissive liquid crystal cell and enlarging and projecting it using a light source of an overhead projector for presentation. However, the transmissivity of this transmissive liquid crystal cell is very low, and the original brightness of the overhead projector cannot be realized, making it difficult to make a presentation on a large screen. Therefore, recently, in order to improve this brightness, while increasing the transmittance of the transmissive liquid crystal cell,
High-brightness overhead projectors compatible with liquid crystal display devices have been commercialized one after another.

However, when a high brightness overhead projector is used, the temperature of the transmissive liquid crystal cell rises due to the heat contained in the light emitted from the light source. When the temperature rises, the contrast of the transmissive liquid crystal cell deteriorates and color unevenness occurs, and the projection performance deteriorates.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Japanese Unexamined Patent Publication No. 63-46416 discloses that air is circulated in a gap between a liquid crystal display cell and a protective panel to cool the liquid crystal display cell. However, the liquid crystal display cell is cooled in order to always maintain a temperature below a certain value. There is a problem that the air volume noise needs to be very large because it is necessary to increase the air volume.

Further, Japanese Patent Laid-Open No. 6-82745 discloses that a temperature detector is provided to adjust the air volume according to the detection result. However, since the air volume is adjusted regardless of the noise of the overhead projector, the overhead projector is used. However, depending on the model, there was still the problem that air volume noise was a concern.

In view of the above problems, the present invention aims at controlling the cooling air flow rate according to the temperature rise of the liquid crystal display device and preventing the temperature rise itself and the liquid crystal display device for an overhead projector which makes the air flow noise less noticeable. A characteristic liquid crystal display device is provided.

[0007]

A liquid crystal display device for an overhead projector of the present invention for solving the above problems is a transmissive liquid crystal cell for displaying an image according to an input signal, and the transmissive liquid crystal cell on the light source side. Type liquid crystal cell and a lower surface protection panel disposed through a desired space, cooling means for sending cooling air to the space between the transmissive liquid crystal cell and the lower surface protection panel, and the temperature of the lower surface of the transmissive liquid crystal cell. It has a temperature detector for detecting and a noise detector for detecting ambient noise, and controls the cooling means based on the detection results of the temperature detector and the noise detector to adjust the amount of cooling air. It is a thing.

Further, the liquid crystal display device for an overhead projector is characterized by comprising warning means for inputting a detection result of the temperature detector to a microcomputer and displaying a warning under the control of the microcomputer.

According to another aspect of the present invention, in a liquid crystal display device arranged in an optical path from a light source section of an overhead projector to a screen, a transmissive liquid crystal cell for displaying an image by an input signal and an upper surface of the transmissive liquid crystal cell. The upper surface protection panel, the lower surface first protection panel arranged close to the transmissive liquid crystal cell on the light source side of the overhead projector, and the lower surface first protection panel and a desired space. It has a lower surface second protection panel, and is composed of a lower surface first protection panel and a cooling means for sending cooling air to the space of the lower surface second protection panel.

[0010]

The liquid crystal display device for an overhead projector according to the present invention comprises a cooling means for sending cooling air to the space between the liquid crystal cell and the lower surface protection panel, a temperature detector for detecting the temperature of the lower surface of the liquid crystal cell, and a liquid crystal display device surrounding the liquid crystal display device. It has a noise detector that detects noise, and the cooling air can be adjusted based on the two detection results. Therefore, the rotation speed of the fan can be controlled according to the temperature rise, and in the past, the rotation speed was reduced to reduce the noise of the fan. Although the upper limit was set and it could not be used for a long time with a high light output overhead projector, by using the noise detector shown in the present invention, the maximum rotation speed can be adjusted according to the noise of the high light output cooling fan. It has the feature that it can be rotated and the heating of the liquid crystal cell can be prevented.

Further, the present invention is characterized in that the detection result of the temperature detector is input to the microcomputer and a warning is displayed under the control of the microcomputer. If the user forgets to remove it from the overhead projector, when it is used at a high temperature, or when the power supply is turned off. Even if is not included, the LED on the liquid crystal display device blinks the warning or displays the warning on the on-screen, so that the user can be notified of the dangerous state of the liquid crystal cell.

According to another aspect of the present invention, a transmissive liquid crystal cell and an upper surface protection panel disposed on the upper surface of the transmissive liquid crystal cell,
A lower surface first protective panel for heat countermeasures for removing infrared rays and ultraviolet rays, which is arranged in the vicinity of the transmissive liquid crystal cell on the light source unit side of the overhead projector, and a lower surface first protective panel, and a desired space, and a desired space. The liquid crystal cell has a lower second protection panel that mainly protects against mechanical stress from the outside, and is composed of a cooling unit that sends cooling air to the space of the lower first protection panel and the lower second protection panel. The temperature rise is extremely suppressed, and the liquid crystal cell can be prevented from being heated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device for an overhead projector according to the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 4 shows an appearance of an overhead projector to which the present invention is applied. Reference numeral 30 denotes an overhead projector main body, and a projection lamp, a Fresnel lens (not shown), and a control circuit for controlling the entire overhead projector are provided. It is built in. A liquid crystal display device 10 enlarges and projects the image information of the transmissive liquid crystal cell 1 and displays it on a screen 20.

FIG. 1 shows a sectional view of a liquid crystal display device 10 for the overhead projector. The transmissive liquid crystal cell 1 A / D-converts an input video signal (not shown) or an RGB signal from a personal computer or the like, and controls the drive circuit 11 to display it. A temperature detector 4 is installed on the lower surface irrespective of the display area of the liquid crystal cell to monitor the temperature of the liquid crystal cell 1 in real time. A liquid crystal cell 1 is sandwiched above the body cover 12, and a lower surface protection panel 2 is attached to the body cover 12 10 mm below the liquid crystal cell. A cooling fan 3 for cooling the liquid crystal cell is provided on the side of the space between the liquid crystal cell 1 and the lower surface protection panel 2, and is rotated to lower the temperature. Although a suction fan is used in the drawing, the same effect can be obtained with a discharge method. A noise detector 5 is installed near the cooling fan 3 to detect noise around the fan and the surroundings.

When the liquid crystal display device 10 is placed on the overhead projector 30 which emits light and is used, the temperature detector 4 transmits the temperature information of the liquid crystal cell to the judgment circuit 8 and the temperature exceeds 40 ° C. as shown in FIG. And control circuit 9 to increase the fan air volume by 20%. On the other hand, even if the air volume is increased by 20%, it does not become larger than 45 dB around the fan, but in a high light output overhead projector that uses a metal halide lamp of 1 kW or more, the sound of the cooling fan becomes loud and 60 dB or more. It is possible to suppress the temperature rise of the liquid crystal cell 1 by increasing the flow rate of the cooling fan 3 by 30 to 50% so that it is detected by the noise detector 5 of the display device 10 and not noticeable. Here, the position of the noise detector is installed near the fan in this embodiment, but the most preferable form is that it is installed near the fan of the overhead projector, and the noise level in the surroundings can be accurately detected.

When the overhead projector is left on without powering on, the temperature of the polarizing plate in the liquid crystal cell 1 rises and the microcomputer in the circuit blinks the LED 6 indicating a warning based on the temperature detection result. , The on-screen display shows that there is an abnormality in the installation status, and it is possible to notify the user.

(Embodiment 2) In the structure of FIG. 2, the relationship between the liquid crystal cell 1 and the temperature detector 4 is the same as that of the embodiment 1.
The liquid crystal cell 1 is set between the upper surface protection panel 22 and the lower surface first protection panel 2a, and infrared rays and ultraviolet rays are cut by the lower surface first protection panel 2a so as to remove heat from the light source as much as possible. A lower surface second protection panel 2b is attached to the lower surface of the body cover 12, and is designed to have a strength so as to be protected from a mechanical shock from the outside when it is stored in a bag or the like.

The air blown from the cooling fan flows between the lower surface first protective panel 2a and the lower surface second protective panel 2b, and the lower surface first protective panel 2a is mainly cooled. The temperature rise of the liquid crystal cell 1 is slower than that of the first embodiment because the infrared rays and the ultraviolet rays are cut off. However, when the temperature rise occurs, the temperature detector 4 detects it and the air volume of the cooling fan 3 increases. Can be increased by 20 to 50%.

Although an axial fan is used as the cooling means in this embodiment, the cooling means is not limited to this. For example, a cross fan may be used, and since the cross fan supplies wind on the surface, cooling on the surface is possible.
Therefore, since each part of the panel can be cooled uniformly, deterioration of an image can be prevented.

[0021]

As is apparent from the above description, the liquid crystal display device for an overhead projector of the present invention is a cooling means for sending cooling air to the space between the liquid crystal cell which is displayed as an image by the input signal and the lower surface protection panel. And a temperature detector that detects the temperature of the lower surface of the liquid crystal cell and a noise detector that detects the noise around the liquid crystal display device, and the amount of cooling air can be adjusted based on the two detection results. The number of rotations of the fan can be controlled according to the number of rotations, and the cooling fan of the high light output overhead projector can be rotated at the maximum number of rotations according to the noise of the cooling fan to prevent heating of the liquid crystal cell. .

Further, the present invention is characterized in that a heating warning is displayed based on the detection result of the temperature detector, and when the liquid crystal display device is forgotten to be removed from the overhead projector, when it is used at a high temperature, or when the power is not turned on. The upper LED causes the warning to blink and the warning to be displayed on the screen, so that the user can be informed of the dangerous state of the liquid crystal cell.

In still another aspect of the present invention, a transmissive liquid crystal cell for displaying an image according to an input signal, a top protection panel arranged on the upper surface of the transmissive liquid crystal cell, and a transmissive liquid crystal cell on the light source section side of an overhead projector. A lower surface first protection panel for removing infrared rays and ultraviolet rays, which is disposed in the vicinity of the first protection panel, and a lower surface first protection panel and a lower surface which are arranged through a desired space and mainly protect from mechanical stress from the outside. It has a second protective panel, a lower surface first protective panel and a lower surface second
Since it comprises cooling means for sending cooling air to the space of the protective panel, it has the feature that the temperature rise of the liquid crystal cell is extremely suppressed and the heating of the liquid crystal cell can be prevented. Is extremely large.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display device for an overhead projector according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a liquid crystal display device for an overhead projector according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a control system in the first embodiment of the present invention.

FIG. 4 is an external view to which the present invention is applied in the first and second embodiments of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal cell 2, 2a, 2b Lower surface protection panel 3 Cooling fan 4 Temperature detector 5 Noise detector 6 LED 7 On-screen 8 Judgment circuit 9 Control circuit 10 Liquid crystal display device 11 Drive circuit 12 Main body cover 20 Screen 22 Upper surface protection panel 30 Overhead projector (OHP)

Claims (4)

[Claims] 1. A liquid crystal display device arranged in an optical path extending from a light source section of an overhead projector to a screen, wherein a transmissive liquid crystal cell for displaying an image by an input signal, and the transmissive liquid crystal cell on the light source section side. A lower surface protection panel arranged via a desired space, cooling means for sending cooling air to the space between the transmissive liquid crystal cell and the lower surface protection panel, and temperature detection for detecting the temperature of the lower surface of the transmissive liquid crystal cell. And a noise detector for detecting noise in the surroundings, and controlling the cooling means based on the detection results of the temperature detector and the noise detector to adjust the amount of cooling air. Liquid crystal display device for overhead projector. 2. A liquid crystal display device arranged in an optical path extending from a light source section of an overhead projector to a screen, wherein a transmissive liquid crystal cell for displaying an image by an input signal and the transmissive liquid crystal cell on the light source section side. A lower surface protection panel arranged via a desired space, cooling means for sending cooling air to the space between the transmissive liquid crystal cell and the lower surface protection panel, and temperature detection for detecting the temperature of the lower surface of the transmissive liquid crystal cell. A liquid crystal display device for an overhead projector, comprising: a temperature detector, a microcomputer for inputting a detection result of the temperature detector, and a warning unit for displaying a warning under the control of the microcomputer. 3. A liquid crystal display device arranged in an optical path extending from a light source section of an overhead projector to a screen, wherein a transmissive liquid crystal cell is displayed as an image by an input signal, and an upper surface protection panel disposed on an upper surface of the transmissive liquid crystal cell. A lower surface first protection panel arranged in proximity to the transmissive liquid crystal cell on the light source side of the overhead projector, and a lower surface second protection panel arranged with the lower surface first protection panel through a desired space. A liquid crystal display device for an overhead projector, comprising: a cooling unit that sends cooling air to the space between the lower surface first protection panel and the lower surface second protection panel. 4. The liquid crystal display device for an overhead projector according to claim 3, wherein the first lower surface protection panel comprises a film or a reflection plate that reflects infrared rays and ultraviolet rays.