JPS633273Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention uses three cathode ray tubes (hereinafter abbreviated as CRT) that correspond to the three emission colors that make up color images.
The present invention relates to a video output circuit for a video projector that facilitates convergence adjustment in a video projector that projects information light onto a screen via a magnifying lens or Schmitt optical system.

Unlike general color television receivers, this type of video projector has three
Because each CRT is independent, its mechanical mounting position is different, and the images projected onto the screen will have different distortions in red, green, and blue. Therefore, convergence adjustment is required to correct these distortions and combine the three-color images into one image without distortion. Convergence adjustment is performed by connecting a pattern generator that generates signals such as crosshatch patterns and color bars to the video projector. Convergence adjustment is performed by generating a crosshatch pattern signal in the pattern generator, causing the CRT to receive the crosshatch pattern, and projecting it onto the screen. The green CRT is located in the center of the red CRT, and the blue CRT
Match. By the way, the visibility of the human eye for blue is much lower than that for green and red, so it is difficult to accurately perform the above adjustment for blue.

The present invention was proposed to improve these drawbacks, and aims to facilitate the convergence adjustment of blue CRTs by converting blue color into a color with apparently high visibility. It is. In other words, if the green CRT and blue CRT receive a crosshatch pattern, and the red CRT emits a raster image, then on the screen a yellow crosshatch pattern and a red raster pattern created by combining the red raster and green crosshatch pattern will appear on the screen. A magenta crosshatch pattern is formed by combining the blue and blue crosshatch patterns, so by matching the magenta crosshatch pattern to the yellow crosshatch pattern, the convergence adjustment of the blue CRT with respect to the green CRT is performed. .

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block circuit diagram for adjusting the convergence of a video projector to which an embodiment of the present invention is applied. 1 is a video signal input terminal, and a video signal obtained by video detection of a video intermediate frequency signal taken out by a tuner is inputted to a video signal processing section 2. The video signal processing section 2 amplifies the input video signal and performs color signal processing and luminance signal processing.
The red video output circuit 3 amplifies the red primary color signal obtained by the video signal processing section 2 and outputs it to the red CRT 6.
Similarly, the green video output circuit 4 amplifies the green primary color signal and outputs it to the green CRT 7, and the blue video output circuit 5 amplifies the blue primary color signal and outputs it to the red CRT 8.
A pattern generator 9 generates a pattern signal for convergence adjustment, and is connected to the video signal input terminal 1 of the video signal processing section 2.

FIG. 2 is a circuit diagram of the red video output circuit 3, green video output circuit 4, and blue video output circuit 5 shown in the block circuit diagram of FIG. 1, which constitute the essential parts of the present invention. _TR ,
T _G and T _B are input terminals for red, green, and blue primary color signals, respectively. +B ₁ and +B ₂ are power supply voltages of the video output circuit. A circuit 30 consisting of transistors Q ₃₁ , Q ₃₂ , Q ₃₃ and resistors R ₃₁ to R ₃₆ , a circuit 40 consisting of transistors Q ₄₁ , Q ₄₂ , Q ₄₃ and resistors R ₄₁ to R ₄₆ , transistors Q ₅₁ , Q ₅₂ , Q ₅₃ and resistors R ₅₁ to R ₅₆ are amplification circuits for a red primary color signal, a green primary color signal, and a blue primary color signal, respectively. Since the blue video output circuit 5 does not include the switches and bias resistors of the red video output circuit 3 and the green video output circuit 4, which will be described later, the blue video output circuit 5 and the blue primary color signal amplification circuit 50 are the same. be. The primary color signals amplified by each primary color signal amplification circuit are applied from the collectors of transistors Q ₃₃ , Q ₄₃ , Q ₅₃ to cathode electrodes K _R , K _G , _KB of each CRT, respectively.

The switch SW ₁ provided between the base of the transistor Q ₃₁ of the red video output circuit 30 and the red signal input terminal _TR and the transistor of the green video output circuit 40
A switch SW ₂ provided between the base of Q ₄₁ and the green signal input terminal _TG is a switch for switching between the video signal input to the video signal input terminal 1 and raster. Switch SW ₁ is terminal T ₃₁ Switch SW ₂ is terminal T ₄₁
When connected to the terminal T32, the normal video signal is received by the red CRT6 and green CRT7, and the switch _SW1 is connected to the terminal _T32.
When switch SW ₂ is connected to terminal T ₄₂ , the red
Red and green rasters are illuminated on the CRT 6 and green CRT 7, respectively. Resistors R ₃₇ and R ₃₈ are bias resistors that determine the brightness of the red raster, and resistors R ₄₇ and R ₄₈ are bias resistors that determine the brightness of the green raster.

Next, the convergence adjustment of the blue CRT will be explained based on the block circuit diagram of FIG. 1 and the circuit diagram of FIG. 2. When using the green CRT 7 as a reference, connect the changeover switch SW 1 of the red video output circuit ₃ and the changeover switch SW ₂ of the green video output circuit 4 to the T ₃₂ and T ₄₁ terminals, respectively, and generate a crosshatch signal with the pattern generator 9. If you let it turn red
A raster is illuminated on the CRT, and the crosshatch signal is separated into green and blue primary color signals in the video signal processing unit 2, and the primary color signals are sent from the respective primary color signal input terminals T _G and T _B to each video output circuit 4. , 5 and is amplified, and a crosshatch pattern is received on each CRT. Therefore, a yellow and magenta crosshatch pattern is formed on the screen, and the convergence of the blue CRT can be adjusted. The present invention provides a raster generating circuit in the red video output circuit and the green video output circuit as described above, and combines the pattern received by the blue CRT with the red or green raster on the screen to create a color with high visibility. It becomes possible to convert to the pattern of
This has the effect of facilitating the convergence adjustment of the blue CRT.

[Brief explanation of the drawing]

FIG. 1 shows a block circuit for adjusting the convergence of a video projector according to the present invention. FIG. 2 is a circuit diagram of a video output circuit which forms the main part of the present invention. 30: Red video signal amplification circuit, 40: Green video signal amplification circuit, Q ₃₁ : Red video signal amplification circuit input stage transistor, Q ₄₁ : Green video signal amplification circuit input stage transistor, SW ₁ , SW ₂ : Switch.

Claims (1)

[Claims for Utility Model Registration] A video system in which information light from three cathode ray tubes corresponding to the three emitted light colors constituting a color image is projected onto a screen via a magnifying lens or Schmitt optical system. In the projector, a first switch means is provided at the base of the transistor in the input stage of the red primary color signal amplification circuit and is capable of selectively applying the red primary color signal and the first DC voltage; and a green primary color signal amplification circuit. A video projector comprising second switch means provided at the base of a transistor in a circuit input stage and capable of selectively applying a green primary color signal and a second DC voltage. Output circuit.