In this thesis, a double-mode linear imaging system is designed for the application of microspectrometers. The imaging system is optimized so as to work with a Planar Double Grating System and a Linear Variable Optical Filter, the combinations of which would be suitable candidates of high-resolution low-cost microspectrometers. This linear imaging system comprises one linear photodiode array and two readout modes: the integration mode and the coherent detection mode. The integration mode is applied when the leakage current is much smaller than the photocurrent, which increases the SNR by long integration time and improves the dynamic range by variable integration time control. The coherent detection mode is applied when the leakage current is comparable with the photocurrent, which aims at reducing the error caused by leakage current. The prototype of the imaging system is fabricated in AMIS 0.35um CMOS process.