We propose a pixel aperture technique in a complementary metal oxide semiconductor (CMOS) image sensor for 3D imaging. In conventional camera systems, the aperture is located between the object and the CMOS image sensor (CIS); this type of image sensor consists of a pixel array with red, green, and blue (RGB) Bayer pattern color filters. Our proposed image sensor uses red, green, blue, and white (RGBW) (without color filter) filters, and the aperture is located on the W pixel. A sharp image can be obtained from the W pixels, and the RGB pixels produce a defocused image with blurring. The sharp image can be compared with the defocused image to obtain depth information for 3D imaging. A metal layer, such as aluminum in the conventional CIS process, is used for the aperture on the white pixel. We designed and simulated a pixel model for the pixel aperture technique using a 0.11 µm CIS process and evaluated the performance of the proposed technique using finite-difference time-domain (FDTD) analysis.