An efficient method for measuring the internal parameters of optical cameras based on optical fibres

In this work, we report an expedient auto-collimating method for self-measuring the internal parameters (IPs) of optical cameras. Several key optical components, including the thin optical fibre (TOF), reflecting prism, and receiver, are introduced into optical cameras. The TOF outgoing end and area-array image receiver are integrated onto the focal-plane assembly of optical cameras. Different wavelengths of light, which are emitted by external sources, are transmitted to the focal plane through optical fibres. Because one optical fibre can transmit different wavelengths of light, the same position on the focal plane can obtain point light sources (PLSs) with different wavelengths. Then, the optical system of the cameras spontaneously transforms the PLSs into auto-collimating lights. The auto-collimating lights are reflected by a two-plane prism, return to the camera optical system, reach the focal plane and are received by the area-array sensor. Finally, the IPs are calculated based on a mathematical model of the imaging relation between fibre light sources and images. The experiment confirms that this method is efficient and has a level of precision of dozens of micrometres for an optical camera with a short focal length and small field of view. Our method is suitable for on-orbit IP measurements for cameras without spatial or temporal limitations.