Martin J. Richards

Apparatus using one optical sensor to recover audio information from analog and digital soundtrack carried on motion picture film

An apparatus recovers audio information from analog and digital motion picture film soundtracks using a single optical sensor that senses across the widths of both soundtracks. Symbols representing audio information in the digital soundtrack are encoded in two dimensions and are recovered by oversampling the symbols in two dimensions. The two-dimensional encoding of digital information can be used with a variety of recording media; however, in one embodiment, the symbols are carried on motion picture film between the sprocket holes.

Reproduction of sound track signals by varying the detector threshold level as a function of the transverse scan position

Audio information is recovered from a variable-area optical record, particularly motion picture film variable-area optical soundtracks. A scan signal is obtained by repetitively scanning the optical record substantially transverse to the bias line. The noise reduction effect is enhanced by a threshold detector which is provided with a transversely varying threshold level that varies according to the position of the scan across the width of the soundtrack. A threshold is provided for a bilateral soundtrack, the threshold having a minimum level at the bias line of the soundtrack and increasing progressively with distance from the bias line. Thus, one each scan, the threshold level is high when the scan is at the edge of each soundtrack, falls progressively to a minimum when the scan reaches the bias line, and then increases progressively back to its original high level when the scan is at the other edge of the soundtrack.

The Effective Gain of a Projection Screen in an Auditorium

A gain screen is a technology used to increase the light levels seen by the audience without increasing the output of the projector. The quoted gain of the screen is the location of the highest gain, which is available at a single location on the screen (the hot spot), and for a limited number of seat locations near the center aisles. However, the perceived brightness of the image on the screen is not solely determined by the peak brightness of the hot spot, nor is the seat in the center of the auditorium the only location with an audience member. The perceived brightness, a subjective quantity, is more closely related to the total amount of light reflectingfrom the screen to the viewer than to the single hot spot point. Objectively, what we really want to know is the Lumen value at the viewers location, rather than the foot-Lambert value of a single point on the screen. Measuring the gain of the screen at many locations in the theater is not practical, but fortunately the information to calculate the gain at each seat exists in the screen specification sheets, and the room geometry. Once the screen gain is calculated for each seat in the auditorium, the overall effective screen gain can be determined from their average. A method is demonstrated for calculating this average screen gain and the overall effective room light level. The gain averaged over the screen and over all seats in the auditorium is always lower than the quoted gain of the screen. For 3D systems using silver screens, the average left eye/right eye crosstalk across the screen is negatively impacted by the screen doing an imperfect job of maintaining polarization, especially at the edges of the auditorium. Larger values of crosstalk are coincident with poor performance from both a gain and uniformity standpoint.