28 
The binocular observation system is comparatively simple and has a high optical perfor 
mance. As measuring mark, an opaque disc of 25 pm diameter (in the photo-plane) is 
employed. On request, different sizes and shapes of the measuring mark can be provided. 
The standard magnifications are xlO, x20, and x40. 
The digitisers, attached to the ends of the x- and y-spindles, are of the optical electronic 
type. 
The control panel with switches for operation and the setting device for the point numbers 
(or codes) is attached under the eyepieces. 
The electronic control unit is provided with a storage, facilitating fast operation, and Nixie 
tubes for a visual display of coordinates. For x and y, there are 6 decimal places and for the 
point number (or code) 8 places. The zero-coordinates can be set for any initial point. 
Different types of electrical typewriters, tape- or card punchers can be used. 
V. 2 Kern Monocomparator MK1. 
The design of this monocomparator is based on the Abbe comparator principle; it is to some 
extent similar to the Ascorecord of Zeiss-Jena. 
The photo-carrier is provided for maximum 12" x 12" format. A cross-slide system is used 
as the tracking device (fig. 20). Slow and fast tracking is possible. However, the measuring 
device is practically independent from the tracking device. 
Fig. 20. Monocomparator Kern MK1. 
The measuring device consists of two fine reference lines perpendicular to each other and 
of two linear glass-scales. The xy-reference lines are engraved on the supporting glass 
plate of the photo-carrier. They serve as the x- and y-coordinate axes (fig. 21). The two 
glass scales are perpendicular to each other and fixed with respect to the measuring mark;