JPH0351889A - Projection type display - Google Patents

Abstract

PURPOSE:To make the brightness distribution of an image on a screen uniform and to make the image to see by providing a storage means stored with data of the opposite characteristics from the image of an optical system for displaying the image and a brightness varying means which varies the brightness distribution of a CRT screen according to the opposite characteristic data. CONSTITUTION:The storage means 1 is stored with the data of the opposite characteristics from the brightness distribution of the image of the optical system for displaying the image. The brightness varying means 7 varies the brightness distribution of the CRT between according to the opposite characteristic data. On the CRT on a light source side, the brightness distribution of the CRT screen is made to correspond to the opposite characteristic data. Then the brightness of the CRT screen is made lower toward the center part, so when images of both the surfaces of the CRT are projected on the screen through the optical system, the image on the screen has the distortion of the brightness distribution of the optical system corrected. Consequently, the brightness distribution of the image on the screen is made uniform and the image becomes easy to see.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a projection display, and more particularly to a projection display in which an optical system equalizes the brightness distribution on the screen to make it easier to see the image on the screen. It is. [Background of the Invention] In recent years, various large-screen projection displays using CRTs have been proposed.On the other hand, since a large screen is desirable for high-definition, etc. for the sense of realism, various projection-type displays for displaying high-definition have been proposed. It was proposed. [Problems to be Solved by the Invention] Incidentally, in the above-mentioned projection display, in order to display an image on the screen, the light source side (which outputs the image)
}I, G, B CRT) and an optical system to project this image onto the screen. On this light source side, the fourth
As shown in Figures 6 to 6, as the signal voltage increases, the brightness on the screen also increases, and the brightness distribution on the screen becomes approximately constant. is determined, so the brightness distribution on the light source side is not accurately reflected on the screen. That is, the brightness distribution on the CRT screen on the light source side is different from the brightness distribution on the screen, and there is a problem in that the periphery of the screen in particular becomes relatively dark. Note that the brightness distribution shown in Figure 6 is C
This applies to the RT screen and the horizontal direction on the screen, but the vertical direction can also be considered in the same way. This invention was made in view of the above problems, and its purpose is to provide a projection display that can make the brightness distribution of an image on a screen uniform. [Means for Solving the Problems] In order to achieve the above object, the present invention provides an optical system for displaying a CRT image on a screen, which has an inverse characteristic to the luminance distribution of the image in an optical system for displaying the image. [Function] Since the above method is provided, the present invention is characterized in that the present invention is provided with a storage means for storing data of the CRT screen, and a brightness variable means for changing the brightness distribution of the CRT screen according to the inverse characteristic data. In the CRT on the light source side, the brightness distribution of the CRT screen is determined to be a brightness distribution according to the inverse characteristic data. Then, the brightness is lowered towards the center of the CRT screen, so when the image on this CRT screen is projected onto the screen via the optical system, the distortion in the brightness distribution caused by the optical system is corrected for the image on the screen. Become a thing. In other words, the brightness distribution on the screen becomes uniform, and the image on the screen becomes easier to see. [Example] Hereinafter, an example of the present invention will be described based on the drawings. In Figure 1, the light source side of the projection display (e.g. R, G, 8 CRT) is equipped with data (digital) with characteristics opposite to the distortion in order to correct the distortion of the brightness distribution on the screen caused by the optical system. A frame memory 1 for storing, a vertical deflection circuit 2 and a horizontal deflection circuit 3 for outputting vertical/horizontal synchronizing signals for reading this reverse characteristic data, and a D/A converter 4 for converting this read characteristic data into analog. and,
A filter circuit (L
PF) 5, an amplifier 6 that amplifies the signal of this shaped inverse characteristic data, and a signal gain in order to correct the brightness on the light source side (the brightness on the CRT screen of R, G, B) by the above inverse characteristic data. A variable gain amplifier (gain adjustment means) 7 is provided to adjust the gain according to the inverse characteristic signal. Further, on the light source side, a PLL circuit 8 is provided which generates a clock of a frequency according to the horizontal synchronizing signal of the horizontal deflection circuit 2 when reading the reverse characteristic data of the frame memory 3. Here, to explain in detail the inverse characteristic data of frame memory 1, as shown in the measurement results in Figure 2, the brightness distribution on the screen (solid line in the figure) and the original brightness distribution (broken line in the figure) are different. In between, distortion occurs in the brightness distribution due to the optical system (arrow in the same figure). Then, the brightness distribution on the screen can be approximated by a polynomial, Z = f (x * y). Note that 2 is the brightness - Xpy is the position on the screen. Therefore, considering the signal voltage-brightness curve, find a characteristic function where Z = constant, calculate the data (digital data) at the x and y positions on the screen using this characteristic function, and convert this data into This is stored in the frame memory 1 as reverse characteristic data. When the projection display is operated, an image corresponding to the operation is emitted from the light source through an optical system, and this image is projected onto the screen. At this time,
As shown in Figure 3, the luminance distribution on the light source side, for example, R
, G, and B on the CRT screen are lowered toward the center of both sides because the signal gain is lowered near the center of the screen. Therefore, since the brightness distribution on the screen also changes relative to the brightness distribution of the CRT screen, the brightness distribution on the screen is lowered near the center and is made to be at the same level as the periphery. In other words, the image on the screen is displayed with approximately uniform brightness, making the image easier to see and improving the image quality. In this way, the circuit on the light source side can remove distortions in the brightness distribution, which are extremely difficult to achieve with optical systems.As this is not only difficult but cannot be easily corrected by improving the optical system, we are able to quickly respond to user requests. There will be no need to say that you can't do it. [Effects of the Invention] As explained above, according to the projection display of the present invention, the brightness distribution on the light source side (R, G.B CRT screen) is lowered toward the center of the screen than at the periphery. The upper luminance distribution can be made almost uniform, making it easier to see both sides of the screen, and improving image quality.

[Brief explanation of drawings]

FIG. 1 is a schematic partial block diagram of a projection type display showing an embodiment of the present invention, and FIGS. 2 and 3 are graph diagrams for explaining calculation of inverse characteristic data in the projection type display. Figures 4 to 6 are graphs for explaining the luminance distribution in conventional projection displays. In the figure, l is a frame memory (storage means), 2
is a vertical deflection circuit, 3 is a horizontal deflection circuit, 4 is a D/A converter, 5 is a filter circuit (PLF), 6 is an amplifier, 7 is a variable gain amplifier (gain adjustment means), and 8 is a PLL circuit.

Claims (2)

[Claims] (1) When displaying both images of the CRT screen on the screen, a storage means that stores data having characteristics opposite to the brightness distribution of the image in an optical system for displaying the images; A projection type display comprising a brightness variable means for changing the brightness according to the inverse characteristic data. (2) The brightness variable means includes R, G, and B CRs on the light source side.
Claim 1: The gain adjustment circuit is provided in a T circuit and changes a luminance distribution on a CRT screen according to the inverse characteristic data.
) Projection type display.