Abstract: An illumination intensity correcting circuit including a curve fitting circuit formed by differential amplifier circuits and a load resistor, wherein the amplification factor of the curve fitting circuit is changed before and after each breakpoint voltage, the reference voltages of the differential amplifier circuits are set so that at least two breakpoint voltages are arranged in the range of a voltage of a video signal, and the amplification factors of the differential amplifier circuits are set so that the amplification factor of the curve fitting circuit in the range of the signal voltage inside of the two breakpoint voltages is smaller than the amplification factor outside of the two breakpoint voltages.

Abstract: When a display image is a photographic image or a moving image, an ON signal is inputted from the ON-OFF circuit and the ON-OFF circuit to the sharpness circuit and the gamma correction circuit under a control signal from the control circuit. An inputted image signal Fc is subjected to sharpness processing for edge enhancement by the sharpness circuit, and the intermediate signal level of the image signal Fc is raised by gamma correction of the gamma correction circuit. Thus, the CRT can display a sharp, high-quality photographic or moving image having an enhanced edge and emitting light with its luminance proportional to the signal level. When a display image is a code display image of letters or the like, the sharpness circuit is controlled to be in an unactivated state and the gamma correction circuit is controlled to be in an activated state under a control signal from the control circuit.

Abstract: The present invention relates to a preamplifier for computer display for transmitting an analog video signal as a result of converting a digital video signal outputted from a computer by a video D/A converter circuit of a digital signal processing IC to a display, wherein an input characteristic of the preamplifier is current input to match a characteristic of current output of the video D/A converter circuit.

Abstract: An illumination intensity correcting circuit including a curve fitting circuit formed by differential amplifier circuits and a load resistor, wherein the amplification factor of the curve fitting circuit is changed before and after each breakpoint voltage, the reference voltages of the differential amplifier circuits are set so that at least two breakpoint voltages are arranged in the range of a voltage of a video signal, and the amplification factors of the differential amplifier circuits are set so that the amplification factor of the curve fitting circuit in the range of the signal voltage inside of the two breakpoint voltages is smaller than the amplification factor outside of the two breakpoint voltages.

Abstract: An illumination intensity correcting circuit including a curve fitting circuit formed by differential amplifier circuits and a load resistor, wherein the amplification factor of the curve fitting circuit is changed before and after each breakpoint voltage, the reference voltages of the differential amplifier circuits are set so that at least two breakpoint voltages are arranged in the range of a voltage of a video signal, and the amplification factors of the differential amplifier circuits are set so that the amplification factor of the curve fitting circuit in the range of the signal voltage inside of the two breakpoint voltages is smaller than the amplification factor outside of the two breakpoint voltages.

Abstract: A gamma correction circuit includes a main imaging signal processing circuit and a correction signal generating circuit. The main imaging signal processing circuit receives an input imaging signal (RGB signals: 3 three primary color signals) Si, and generates an output imaging signal on the basis of a predetermined reference voltage and an output resistance. Moreover, the correction signal generating circuit includes a plurality of current differential amplifiers connected in parallel with each other, and is configured so that the input imaging signal is supplied to the current differential amplifiers and each output of the current differential amplifiers is added to the generated output imaging signal from the main imaging signal processing circuit.

Abstract: To obtain a clear-cut picture image by correcting a contour of a video signal of a natural picture image and the like from a computer. Video signals of, for example, three primary colors (R, G, B), including a natural picture image and the like produced by, for example, a computer from input terminals 1 are supplied to a mixing circuit (2) and mixed at a ratio of, for example, 0.6G+0.3R+0.1B to produce a signal corresponding to a luminance (Y). This signal is supplied to differentiation circuits 3A and 3B having different time constants each other and predetermined high frequency components are extracted therefrom, respectively, and these output signals are selected by a switch (4), and then supplied to an amplifying circuit 5. The gain of the amplifying circuit 5 is arbitrarily controlled by a signal from a control terminal (6).

Abstract: The automatic-discriminating apparatus is constituted by functional blocks such as a killer circuit, an APC circuit, a switch, and an automatic discrimination control circuit. The switch connects one of crystal oscillators to a VCO of the APC circuit by a control signal from the automatic discrimination control circuit. The automatic discrimination control circuit divides one vertical scanning period into predetermined sections. When receiving a killer signal indicating the OFF state from the killer circuit at the predetermined sections even one time, it outputs a control signal holding the connection state thereof to the switch, and holds the APC circuit in the locking state. When receiving a killer signal indicating the ON state at the divided predetermined sections a predetermined number of times, it outputs a control signal connecting the other crystal oscillator through the VCO to the switch.