Abstract: A system is provided for treating sound represented by the varying width of a motion picture film soundtrack, which provides a "flat" frequency response up to 12.5 kHz with maximum phase coherence, even though the film speed is only 62% to 78% of the present speed of 90 feet per minute. The projector photocell which detects a slit-shaped area of light passing through the soundtrack, produces an output that is amplified so the amplification is progressively greater at higher frequencies, with the gain at 12.5 kHz being at least 6 dB greater than at 1 kHz. A photocell is selected whose output at 12.5 kHz is within 1 dB of its output at 1 kHz for light of a wavelength of substantially 1000 nanometers.

Abstract: A circular projection system using segmented trapezoidal screens arranged in a continuous arcuate array about a central vertical axis. The top of each screen is tilted downward. Each screen is illuminated by a projector which is mounted above and behind the screen which opposes it. The image from each projector is also angled downward.For an eight-screen system, each screen is tilted by approximately 8.degree.. For a nine-screen system, each is tilted by approximately 7.degree.. For maximum linearity, the ratio of the distance between the projector lens and the top of the screen on which it projects to the width of the top of said screen is substantially equal to the ratio of the distance between the projector lens and the bottom of said screen to the width of the bottom of said screen.