Modeling of image formation of a low-cost white-light bench microscope with a linear CMOS image sensor: its application in metrology

Abstract

Three-dimensional (3D) microscopy techniques are essentially imaging methods but owing to its ability to get depth information they are widely used in optical metrology. Although the fact that there are numerous examples of applications of confocal microscopy for metrology systems those 3D techniques that more recently came up are very sparse in this field despite its similar optical sectioning ability. In particular there is no report in literature to our knowledge of metrology systems taking advantage of the low-cost, versatility and easy integration of CMOS linear image sensors. We have developed a bench-microscope prototype using LIS-1024 linear sensor (Panavision ©) and have built a model of microscope image formation using Matlab ((Mathworks ©) that is currently being tested in order to optimize sensor performance. The prototype comprises commercial and low-cost mechanical and optical components and a developed sensor readout board based on PIC16F876 microcontroller (Microchip Inc.) allowing its integration in the optical setup. This stage-scanning microscope builds the image through the movement of the specimen in one lateral, in opposition to confocal microscopy that demands scanning in both lateral directions, and in axial direction. Both the actuators control for positioning the object stage and the sensor readout for image acquisition are commanded from a Matlab application in a PC. This paper aims at showing the effectiveness of this model of image formation for the application of this low-cost prototype using a linear sensor also in metrology field. Results will be presented from tests that are being carried out with micromachined components.