Innovative test method for validating image quality performance of automotive lenses over operating temperature range

摘要

The use of electronic imaging systems in the automotive industry has increased dramatically as a result of the wide spread implementation of optical-based safety systems and driver assistance features in new vehicles. The challenging environmental requirements for automotive cameras have given rise to the need for image quality testing of these cameras over a wide range of operating temperatures. Functional and survivability testing of camera assemblies is relatively straightforward and may be carried out in conventional environmental chambers, but assessing the imaging performance of the lens over temperature is critical in evaluating whether hardware performance meets design intent and presents a much more challenging metrology problem. The lens must be contained within a chamber, but the chamber itself must not adversely contribute to the image quality being assessed. Measures must also be taken to prevent condensation in the optical path when operating below the ambient dew point. Additionally, careful consideration must go into the measurement of defocus over temperature - which is the critical metric in temperature testing - to ensure that the chamber is not contributing to the measured focus shift. In this paper, we describe an innovative system that takes these challenges into account and enables users to measure lens image quality metrics over a temperature range of -25°C to 105°C. This system has evolved over the past few years from a strictly in-house laboratory setup to a recently released commercial product, and we will present results from our extensive testing that show good correlation of measurements to modeled behavior.