Partially light-controlled imaging system based on High Temperature Poly-Silicon Thin Film Transistor-Liquid Crystal Display

Abstract

A partially light-controlled imaging system is proposed as a novel device. It is used to improve the imaging quality at the illumination of 1.979 x 10(5)lx by means of mitigating image contrast. It consists of a High Temperature Poly-Silicon Thin Film Transistor-Liquid Crystal Display (HTPS TFT-LCD), which is set between the lens and CCD and is coupled with CCD by the optical fiber taper. The transmittance of pixelated LCD can be controlled by Field-Programmable Gate Array to realize the partially light-controlled and thus dynamic range of the imaging system can be extended. Samples of indoor objects and outdoor license plate are photographed by the prototype imaging system under strong light. The imaging results of this novel system are satisfactory with better restored details, compared with the photos taken by normal CCD camera (WAT-231S2) which uses aperture and shutter to control the overall light intensity.

Beyond the partial light intensity imager: Eliminating Moiré patterns

“…(1) and (2): Comparison between photographs taken using normal CCD camera (a) and PLII [10] (b) under strong light of more than 2.2 Â 10 5 lx. Fig.…”

“…Although Moiré patterns can play a positive role in a few applications [1][2][3][4][5][6][7], they result in unexpected random interference for detection [8][9]. In our previous works [10][11][12][13][14][15], three proposed instruments have suffered from such interference from Moiré patterns. The partial light intensity imager (PLII) uses a transmission-type liquid crystal display (LCD) coupling into a charge coupled device (CCD) camera to enhance the dynamic range to 2.2 Â 10 5 lx in strong light [10][11][12].…”

“…In our previous works [10][11][12][13][14][15], three proposed instruments have suffered from such interference from Moiré patterns. The partial light intensity imager (PLII) uses a transmission-type liquid crystal display (LCD) coupling into a charge coupled device (CCD) camera to enhance the dynamic range to 2.2 Â 10 5 lx in strong light [10][11][12]. In partially light-controlled imaging (PLCI), an LCD is set in front of an image intensifier to adapt to both strong and low level light, such as with the simultaneous occurrence of aurora and airglow [13].…”

“…It should be noted that the transmission type LCD is set between the CCD and the lens. The transmittance of every pixel on the LCD can be regulated by the FPGA or the digital signal processor (DSP) [10][11][12]. When strong light ( 42.2 Â 10 5 lx) with intensity over the detector threshold enters the lens, the program in the FPGA can distinguish the over-exposure area and decrease the transmissions of the corresponding pixels via the LCD driver.…”

Partially light-controlled imager based on liquid crystal plate and image intensifier for aurora and airglow measurement

“…In order to obtain information on both aurora and airglow in 1 image by the same detector, the PLCI is proposed as a novel device. Based on our previous research of liquid crystal and imaging systems [11][12][13], the electron count threshold of CCD is calculated first. Then a liquid crystal plate (LCP) and a super second-generation image intensifier (SSGII) are designed to be located between the lens and the CCD.…”