Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1986-01-21
1988-03-29
Psitos, Aristotelis M.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369124, 369125, 369119, 358347, 358348, G11B 700
Patent
active
047349034
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
TECHNICAL FIELD
The present invention relates to an information recording apparatus suitable for being applied to a case in which an optical film is exposed in response to an electrical input signal and then a recording is carried out thereon.
BACKGROUND ART
The information recording apparatus of this kind is used to record an audio signal on a sound track of, for example, a cinema film. As shown in FIG. 1, an optical image 1 having a triangular cross-section is irradiated through a light irradiating apparatus that includes a galvanometer on a linear-shaped slit 2 and the galvanometer is driven by an electrical audio signal to vibrate the optical image 1 in the direction shown by an arrow 3, whereby a scanning optical beam 4 of which the width is modulated in response to the audio signal is delivered via the slit 2. As shown in FIG. 2, when a cinema film is transported, this scanning optical beam 4 exposes and scans a sound track 5 to record on a sound track 5 an exposed locus 6 whose exposed area is changed with a central line X1 of the sound track 5 as the center.
The film thus exposed is chemically fixed with the result that the exposed locus 6 forms a transparent portion 7A and that the boundary between the transparent portion 7A and an opaque portion 7B draws a recording waveform 8 corresponding to the change of the audio signal.
By the way, when an information is recorded as described above, if the average level positions of the recording waveform 8 are fixed to the positions of, for example, lines X21, X22 in FIG. 2 and the recording waveform 8 is recorded with the average level positions X21 and X22 as the center even when the level of the audio signal is large (FIG. 3) or small (FIG. 4). Because the area of the transparent portion 7A is increased when the level of the audio signal is small, there occurs a problem that offensive noise based on scratches on the film and dust adhered to the film is mixed into the reproduced signal as a background noise. To solve this problem, a prior art background noise reduction circuit 11 shown in FIG. 7 is employed, in which the average level positions X21 and X22 of the recording waveform 8 are changed in response to the level of the audio signal so that when the signal level of the audio signal is small, the average level positions are made closer to the central line X1 as shown in FIG. 5, while when the signal level of the audio signal is increased, they are made distant from the central line X1 as shown in FIG. 6.
The background noise reduction circuit 11 supplies an input audio signal S1 through an input amplifier circuit 12 and a transformer 13 to a full wave rectifying circuit 14. A rectified output S2 therefrom is smoothed by a smoothing circuit 15, that generates a level detecting signal S3 corresponding to the signal level of the input audio signal S1 at the output terminal thereof. This level detecting signal S3 is supplied through an inverting amplifying circuit 16 to an adding circuit 17 in which it is added to the input audio signal S1. The resultant added output is delivered to the galvanometer as an average level position signal S4.
In the circuit arrangement shown in FIG. 7, if the signal level of the input audio signal S1 is decreased, the level detecting signal S3 is also decreased, increasing the average level position signal S4. Thus, the average level positions X21 and X22 of the recording waveform 8 on the sound track 5 are changed so as to approach the central line X1 as shown in FIG. 5. Conversely, if the signal level of the input audio signal S1 is increased, the level detecting signal S3 is increased, decreasing the average level position signal S4. Thus, the average level positions X21 and X22 of the recording waveform 8 on the sound track 5 are changed so as to come away from the central line X1 as shown in FIG. 6.
Consequently, when the input audio signal S1 as shown in FIG. 8A arrives, this signal is full-wave rectified by the full wave rectifying circuit 14 of the ground noise reduction circuit 11 and then smooth
REFERENCES:
patent: 4087651 (1978-05-01), Taneda et al.
patent: 4184055 (1980-01-01), Dolby
patent: 4355383 (1982-10-01), Dolby
patent: 4549288 (1985-10-01), Chan
patent: 4596008 (1986-06-01), Beard
Ozaki Yoshio
Shirai Hidemichi
Eslinger Lewis H.
Psitos Aristotelis M.
Sony Corporation
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