Epson Ultimicron series

view finder

Digital single-lens reflex (D-SLR) cameras are steadily getting smaller and lighter and some recent models equipped with an electronic viewfinder (EVF) are small enough to fit snugly in one hand. Here we introduce ULTIMICRON, a high-temperature polysilicon TFT color LCD panel used in such viewfinders, where it has won a reputation for providing super sharp, natural-looking images.

Viewfinders 101

The body - let alone the lens - of a typical D-SLR camera is large as these cameras typically come with an optical viewfinder which requires more space due to the mirror box, prism, and other optical and mechanical components necessary to present the image captured by the lens. EVFs on the other hand, basically present the same image as captured by the lens without requiring relatively heavy, space-consuming optics and allow the size and weight of the camera body to be reduced.

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A breakthrough in EVF image quality

Earlier EVFs helped reduce D-SLR camera size and weight, but they were not without their drawbacks: not only were the LCD panels small, their pixel count was under 200k - a level insufficient for good focusing. The introduction last year of an EVF claiming "1.4-megapixel equivalent resolution" caused quite a splash. This particular EVF produces a color image by displaying three images, one each of red (R), green (G) and blue (B), in rapid succession within a single frame (1/60th of a second). Therefore, if you were to take a random slice of the frame at any point in time, you would see only one of the colors (R, G, or B) displayed. In reality, the image contains only 480k pixels at any given point in time.

view finder

ULTIMICRON, on the other hand, provides a "true" 1.44 megapixel image. Each pixel has a built-in RGB color filter, and all 1,440k pixels are on at the same time. Regardless of where in time you take a slice of the frame, there is always a 1.44 mega-pixel color image. This is far superior to the "equivalent" 1.44 mega-pixel image.

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Zero color break-up

Equivalent 1.44 mega pixel EVFs also rely on a "color-sequential" display panel, which as the name implies, displays the red, green, and blue images in consecutive order. The three images are switched at extremely high speed to trick the human eye into perceiving a full-color image. However, if the camera shakes when the lens is zoomed—such as when tracking a fast-moving subject like a bird—a disturbing flicker of RGB afterimages becomes visible. This "color break-up" phenomenon happens because the images displayed on the viewfinder cannot keep up with the speed of the subject. ULTIMICRON is naturally immune to this problem because, with all three RGB color filters provided on a single panel, the image is always displayed in full color.

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In-house development makes it possible

The key to ULTIMICRON 's high resolution lies in Epson's panel microfabrication process. Color-sequential displays were used in earlier EVF applications because there was no such thing as a panel with an RGB color filter built into every pixel. Fabricating micro-filters is considered difficult even for companies with their own color filter fabrication technology. The Epson development team began work on a prototype. Using Epson's in-house know-how and combining it with technology developed by the TFT Operations Division, they were able to develop a panel in-house, without outsourcing the color filter.

Moreover, as ULTIMICRON panels are transmissive, a window has to be provided in each pixel to transmit light from the backlight.By applying our TFT panel microfabrication technology to the ULTIMICRON, we have given these panels the high aperture ratio essential for transmitting a large amount of light and providing a bright image.

Electronic viewfinders using ULTIMICRON represent a significant technological advance and are now giving optical viewfinders a run for their money.

News release: Epson Develops 0.52-inch QHD HTPS TFT Color Liquid Crystal Panel for Electronic Viewfinders

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