Accuracy of coordinate measurements at phase modulation by digital raster

Abstract

The development of optical-electronic instruments for measuring linear and angular quantities based on focal-plane array (photomatrices) using a digital phase analyzer (digital raster) is considered. It is shown that, unlike a phase raster with a mechanical drive, a digital raster provides the possibility of automation and increased measurement accuracy, reducing the weight and size characteristics of the measuring instrument. A method for constructing a digital raster is proposed, based on the use of photomatrices in combination with computer technologies. To ensure the required accuracy of the developed opto-electronic devices, the sources and components of the measurement error were investigated. The influence of the discrete structure of a digital raster on the error in measuring image coordinates has been studied. Mathematical expressions are obtained for calculating the limiting values of coordinate measurement errors caused by parasitic phase modulation that occurs when using a digital raster (sampling error). The dependence of these errors on image parameters and pixel size has been determined. It is shown that, based on the permissible maximum sampling error, it is possible to calculate the required dimensions of a photomatrix pixel, while the size of the sampling pixel can be larger than the size of the photomatrix pixel, which is very signifi cant from the point of view of energy relations. The results obtained will be useful in the development of optical-electronic means of angular and linear measurements with digital rasters.