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Home > Technolog NEC'S strengths > Technologies for Projector : Contrast Enhancement
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Contrast Enhancement

Achievement to high quality images (Contrast Enhancement)

Projectors of both the LCD method and DLP method have a display device that throws light from the light source by transmitting or reflecting the light, instead of LED. Due to this nature, they have the disadvantage that the image contrast tends to be deteriorated, and the solutions for this have been an issue for improving image quality. In order to improve contrast, some optical measures, such as variable brightness of lamps according to the projected images or variable optical iris are ordinarily provided in general. As an electrical measure, variable contrast according to the projected images is also available. However, this method has the disadvantage that it is difficult to improve the contrast of entirely bright or dark images. Then, we improved the contrast perceived by the eyes even for images where the contrast is difficult to improve with ordinary methods, by employing the image processing LSI uniquely developed by us.

Basic effects of Contrast Enhancement

Contrast Enhancement uses a characteristic of the human eyes where the perception of the color tone may vary with the contrast and the brightness of the surroundings.

By improving the contrast perception at the eyes, shadings are more noticeable and details can be expressed clearly. (Photo) By employing a circuit configuration emphasizing the middle to high range of the frequency elements of image signals, contours and undulations of images are clearer and the contrast perceived by the eyes has been improved with the entire cubic delineation as well.

For this function, the method could be applied up to the SDTV class due to difficulty in the circuit size at the beginning of development. We improved the processing method drastically by using external frame memory so that we could increase the number of horizontal dots, and then the method became possible to apply to 1080i for HDTV. For the RGB signals of PCs, the method is applied by converting the RGB signals into component signals internally. This function is now available for hi-vision images and PC signals.

Furthermore, although image signals are processed with 8 bits in the ordinary system, we developed a method processing image signals for HDTV in 10-bit. Thereby, the projector itself can process input and output signals in 10-bit for an improvement in image quality.


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