| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection type display device which is not deteriorated in the focus performance of CRT, has high brightness without coloring, is resistant to burning of the fluorescent material of the CRT, and has a long life. SOLUTION: This projection type display device converts a horizontal frequency of a blue video signal double by a horizontal frequency converter circuit 20c, and displays the same two video signals obtained at the same horizontal vertical position of the CRT 1c. In such a case, a signal waveform in a low current region of the blue video signal is provided with an inverse gamma characteristic by a gain correction circuit 60, and the signal waveform is increased in gain to improve the cathode ray tube characteristic and the optical characteristic. The blue video signal together with red and green original pictures formed on the fluorescent screens of CRT 1a, 1b are magnified and projected by respective projection lenses 2a, 2b, 2c onto a screen 4 via a reflecting mirror 3, and thus, it is possible to obtain an excellent picture without coloring on the screen 4 from the low current region up to a high current region. |
