JPH0736131U - LCD projector - Google Patents

Abstract

(57) [Summary] [Objective] To provide a liquid crystal projector in which the brightness becomes constant immediately after lighting and the lamp life is not shortened. In a projection type liquid crystal display device in which an image of a transmissive liquid crystal panel is illuminated from the back by a light source lamp and enlarged and projected by a projection lens, a switch of the light source lamp is turned on.
And a brightness adjustment circuit that adjusts the brightness of the liquid crystal panel, and a control unit that controls these. The control unit controls the brightness from the time when the switch is turned on. The brightness of the brightness adjusting circuit is increased during a predetermined time. Alternatively, the brightness of the brightness adjustment circuit is set to the switch ON.
At the time of, increase the value and then decrease to the steady value.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a metal halide lamp light source used for a projection type liquid crystal television which illuminates an image of a transmission type liquid crystal panel from the back side and magnifies and projects the image by a projection lens.

[0002]

[Prior art]

 2. Description of the Related Art In recent years, projection type liquid crystal televisions have been commercialized in which an image of a transmissive liquid crystal panel is illuminated from the back by a light source lamp and enlarged by a projection lens. In the projection type liquid crystal television, the light emitted from the light source is applied to the liquid crystal panel, and the light transmitted through the panel is enlarged and projected on the screen by the projection lens. In principle, such a video projector uses a liquid crystal panel as a light valve instead of the slide of the conventional slide projector, and the light source lamp has a high luminous efficiency and a long life. Metal halide lamps were often used. However, the metal halide lamps described above have the property of being dark immediately after lighting and gradually becoming brighter, and it takes about 1 minute to reach a steady brightness. The temperature of the lamp is detected by a temperature sensor, and a timer is used to increase the voltage applied to the lamp for a predetermined time and increase the lamp current to increase the brightness. However, such a method has a drawback that a high voltage is frequently applied to the lamp and the life of the lamp is shortened.

[0003]

[Problems to be solved by the device]

 As mentioned above, there is a method to detect the temperature of the lamp with the temperature sensor and increase the voltage applied to the lamp for a predetermined time with the timer, thereby increasing the brightness immediately after the lamp is lit. However, since a high voltage has to be applied to the lamp frequently, it has the drawback of shortening the life of the lamp. It is to provide a liquid crystal projector that is bright and does not shorten the life of the lamp.

[0004]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention detects a switch ON of the light source lamp in a projection type liquid crystal display device in which an image of a transmissive liquid crystal panel is illuminated from the back by a light source lamp and enlarged and projected by a projection lens. It is composed of a control unit, a timer that counts the time after the switch is turned on, and a brightness adjustment circuit that adjusts the brightness of the liquid crystal panel.

[0005]

[Action]

 With the above configuration, in the liquid crystal projector according to the present invention, the control unit monitors the time after the light source lamp is turned on by the time data from the timer from the time when the switch is turned on, and according to the time data, , The data of the brightness level of the memory is read, the brightness of the brightness adjustment circuit is increased for a predetermined time according to the read data, and then it is decreased to a steady value. The brightness of is always adjusted to be constant.

[0006]

【Example】

 An embodiment of the liquid crystal projector of the present invention will be described below with reference to the drawings. In the figure, reference numeral 1 is a light source lamp (metal halide lamp), which is composed of an arc tube 2, a reflecting mirror 3, and a case 4 to which they are fixed. Reference numeral 5 is a power switch for the lamp, 6 is a timer for counting time, and 7 is a memory for storing brightness level data corresponding to the time data of the timer 6. A control unit 8 connects the power switch 5, the timer 6, the memory 7, and the brightness adjusting circuit 9.

Next, the operation of the liquid crystal projector according to the present invention will be described with reference to the drawings. In FIG. 1, the control unit 8 obtains a switch-on signal from the power switch 5, detects a lamp lighting signal, starts the timer 6, inputs the time data, and outputs the time data of the timer 6. Based on the time data, the brightness level data stored in the memory 7 corresponding to the time data is read for about 1 minute from the time of switching on, and the brightness of the brightness adjusting circuit 9 is increased by the read data, The brightness of the brightness adjusting circuit 9 is gradually decreased to the standard value as the brightness of the lamp is increased.

The descending speed when gradually lowering the brightness of the brightness adjusting circuit 9 to the standard value is increased at the time of turning on the switch, and then is decreased to a steady value in several steps. There is a method of doing so, or a method of increasing the value at the time of turning on the switch and then gradually decreasing it to a steady value through a number of steps.

[0009]

[Effect of device]

 As described above, according to the liquid crystal projector of the present invention, the screen can be instantly brightened when the light source lamp is turned on, so that a beautiful screen can be seen from the beginning. At the time of turning on the switch, a high voltage is applied to the lamp, so that it is not necessary to increase the brightness of the lamp, so that the life of the lamp can be extended.

[Brief description of drawings]

FIG. 1 is a schematic view of a power supply unit of a liquid crystal projector according to the present invention.

[Explanation of symbols]

 1 Light source lamp 2 Arc tube 3 Reflector 4 Case 5 Power switch 6 Timer 7 Memory 8 Controller 9 Brightness adjustment circuit

Claims (3)

[Scope of utility model registration request] 1. A projection type liquid crystal display device in which an image of a transmissive liquid crystal panel is illuminated from the back by a light source lamp and enlarged and projected by a projection lens, and a control unit for detecting a switch ON of the light source lamp and the switch ON. And a brightness adjusting circuit for adjusting the brightness of the liquid crystal panel, and the controller increases the brightness of the brightness adjusting circuit for a predetermined time from the time when the switch is turned on. A liquid crystal projector characterized by the above. 2. The brightness of the brightness adjusting circuit is increased at the time of turning on the switch, and then decreased to a steady value through several stages. The described liquid crystal projector. 3. The brightness of the brightness adjusting circuit is increased when the switch is turned on, and then gradually decreased to a steady value through a number of steps. 1. The liquid crystal projector according to 1.