Self-Measurements of Point-Spread Function for Remote Sensing Optical Imaging Instruments

A point-spread function (PSF) is able to describe the spatial characteristics of a remote sensing optical imaging instrument (i.e., camera). Specifically, the PSF of a camera characterizes the image quality degeneration inevitably produced by the camera itself link, involving an optical system, an image sensor, and an electronic system in the imaging process of space optical cameras. In the nonblind reconstruction applications, the PSF is the prerequisite for remote sensing image reconstructions. On-orbit PSF measurement approaches are basically based on ground targets hidden remote sensing images, such as edge-based and point-pulse-based approaches. However, external targets used in these measurement methods are easily accessed because the imaging condition is limited by space and time. Here, we propose a real-time self-measurement method using optical fiber illuminations in conjunction with a Lasso-based reconstruction algorithm to measure the on-orbit PSF in real time. First, we construct an infinite object-point generation module by enclosing a laser, a fiber, and optics into a fiber micropoint-illuminator (mFPI), which can produce the collimated thin beams. The mFPI is composed of the head, fiber, and light source. The light source module is located external to the camera, where the lights from a laser are coupled into the input of an optical fiber by using a lens. The head is composed of the fiber output and lens, which is located on the internal of the camera. The light is guided into the head by the fiber, and the head acts as an infinite point target. Second, we propose a PSF reconstruction algorithm based on an extended Lasso model. Finally, confirmation experiments on a camera with optical fibers are performed. The proposed method provides a valuable self-measurement method for on-orbit cameras.