| 摘要 |
PURPOSE:To enable any inexpensive lens system to make sufficient corrections of color phase irregularity by providing a phase modulator and by exercising variable control over an input signal coupling with the variable mechanism for the focal distance of the lens. CONSTITUTION:From potentiometer 22 coupling with the rotation of zoom ring 21, a voltage can be obtained which is high at the wide-angle end of ring 21 and low at the telephone end. Further, attenuator 23 is provided between circuit 18 and input terminal 184 of phase correcting circuit 18 for an index signal. A saw-tooth wave signal of horizontal scanning period H is therefore supplied to circuit 18 via this attenuator 23. Then, a voltage from potentiometer 22 is supplied to attenuator 23 as a control voltage to vary the amplitude of the saw-tooth wave according to the turning angle of ring 21. Therefore, even if the projection diaphragm position shifts according to the turning of ring 21, the amplitude of the saw-tooth wave varies correspondingly, so that phase corrections can be made by circuit 18 in accordance with the projection diaphragm position. |
