Linear and engular Measurements with CCD-Cameras

CCD matrix, a modern device to form video signals, is a unique metrological instrument, which generates data signals and can be used as a measuring graticule.

Its matrix of light-sensitive cells of modern photo and CCD cameras is a product of microelectronic technologies, and represents a 2D array of cells manufactured to 0.01 mcm precision. There can be millions of light-sensitive cells, while the dimensions of each of them and of the array pitch are within the renge of several mcm. Taking into consideration an orthogonal topology and the high accuracy of these structures it is reasonable to use them for solving precision metrological problems.

Multiframe operating mode of CCD camera also allows to substantially reduce the random error by increasing the number of measurement experiments. For a frequency of 30 frames per second and a recording time of 30 seconds we obtain 900 readings of the measurement, which allows us to reduce the random error thirtyfold.

We have performed background research which indicates the possibility of application of hardware-software complexes with CCD cameras for a broad renge of measuring tasks, including:

• Contactless measurement of linear and engular coordinates of objects in motion;
• Measurement of 2D and 3D coordinates of large-size objects and their elements;
• Measurement of motion paths of objects and reference points;
• Measurement of orientation of objects in space by focusing on their details;
• Measurement of reticle geometry in microphotolitography.

Thу above research project was conducted with various CCD cameras, renging from sophisticated ones with matrix thermostatting to simple Web-cameras. The research focused on the analysis of the acceptable error of localization of the object image coordinates on the CCD-matrix to a precision of .001 fraction of mcm.

The possibility of CCD camera applications as a vernier in linear measurements was examined. The proposed solution for long base applications can be considered as an alternative to the incremental sensors, which are not readily amenable to metrological certification.