Estimation of Lens Stray Light with Regard to the Incapacitation of Imaging Sensors

Abstract

We present our efforts on estimating light scattering characteristics from commercial off-the-shelf (COTS) camera lenses in order to deduce thereof a set of generic scattering parameters valid for a specific lens class (double Gauss lenses). In previous investigations, we developed a simplified theoretical light scattering model to estimate the irradiance distribution in the focal plane of a camera lens. This theoretical model is based on a 3-parameter bidirectional scattering distribution function (BSDF), which describes light scattering from rough surfaces of the optical elements. Ordinarily, the three scatter parameters of the BSDF are not known for COTS camera lenses, which makes it necessary to assess them by own experiments. Besides the experimental setup and the measurement process, we present in detail the subsequent data exploitation. From measurements on seven COTS camera lenses, we deduced a generic set of scatter parameters. For a deeper analysis, the results of our measurements have also been compared with the output of an optical engineering software. Together with our theoretical model, now stray light calculations can be accomplished even then, when specific scatter parameters are not available from elsewhere. In addition, the light scattering analyses also allow considering the glare vulnerability of optical systems in terms of laser safety.

Estimation of Lens Stray Light with Regard to the Incapacitation of Imaging Sensors—Part 2: Validation

“…Then, in Section 2.2 , we summarize our measurements and the corresponding data analysis to derive the essential scatter parameters for camera lenses, which are a fundamental part of the input to the theoretical model. Both topics will be discussed only very briefly and thus, for a more in-depth description, we refer the reader to our previous work [ 14 , 22 ]. The content of Section 2.1 and Section 2.2 was taken from references [ 14 , 22 ] and is presented below in a summarized form.…”

“…In this publication, we present our efforts to verify whether the scattering parameters for camera lenses derived in our previous work [ 22 ] are reliable, as well as the validation of our theoretical model of reference [ 14 ]. For this, we first measured the stray light parameters of a two-element laser focusing optics consisting of a well-known optical layout.…”

“…These scatter parameters do not belong to the standard specifications and are therefore usually not known for COTS camera lenses. Therefore, we performed dedicated measurements to estimate such scatter parameters for a selection of eight typical COTS camera lenses of the Double-Gauss type [ 22 ]. Based on these measurements, we derived a generic set of scatter parameters that can be used when the manufacturer does not specify such parameters.…”

“…In addition to the tests regarding the laser-focusing optics, we performed stray light simulations for a generic camera lens of the Double-Gauss type, whose optical layout was extracted from a standard textbook on optical design. To do so, we applied our above-mentioned generic set of scatter parameters derived from our earlier work [ 22 ]. Thus, we compared the output of our theoretical model to the FRED simulation results in order to validate the applicability of our model in conjunction with our generic set of scatter parameters regarding an arbitrary lens of the Double-Gauss type.…”

An Instrument for the Characterization and Calibration of Optical Sensors

“…In our instrument standalone software has been developed versus MATLAB application for the measurement and data storage proposed available in [ 19 ]. In [ 20 ], measurements to assess the scattering parameters of commercial off-the-shelf (COTS) camera lenses are presented. The EMVA 1288 standard was applied by insufficient information is available about the construction and performance of the experimental setup.…”