| 摘要 |
1,222,108. Photo-electric edge followers. MESSER GRIESHEIM G.m.b.H. April 22, 1968 [April 22, 1967], No. 18930/68. Heading G1A. In an edge follower for controlling a flame torch cutting machine, an auxiliary photo-detector 3 is used to sense the general brightness of the pattern-carrying surface or template, and to adjust an element in the optical system of the apparatus so as to maintain the intensity on the main detector 4 constant and so prevent the follower apparatus being guided away from the edge by the effect of changes in extraneous background illumination e.g. sunlight. The follower system is of the type in which the resistance of a photo-resistor 4, on to which is focused an image of the edge of a line or template, is compared with that of a fixed resistor in a bridge, and unbalance is used to generate control signals for the follow-up motor of the machine. The auxiliary cell 3 may be a photo-voltaic device, photo-diode or photo-transistor and its output is fed after comparison with a fixed level U to amplifiers 1 or 2 for driving servo 7. This can control an iris diaphragm 5 (as shown), a wedge or rotatable neutral density filter, or a perforated disc diaphragm. The apparatus is useful for line following with a bright sunlight background, and can also cope with yellowed or dirty drawings. |
