JPH0430087B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an information recording device, and is particularly suitable for application to exposure recording of an optical film in response to an electrical input signal.

[Background technology and its problems]

This type of information recording device is used, for example, to record audio signals on the soundtrack of a movie film, and as shown in FIG. By illuminating the linear slit 2 and driving the galvanometer electrically with the audio signal, the triangular light image 1 is vibrated in the direction of the arrow 3, thus passing through the slit 2 with a width corresponding to the audio signal. A modulated scanning light beam 4 is obtained. As shown in FIG. 2, this scanning light beam 4 scans and exposes the soundtrack 5 as the movie film runs, and as a result, the exposed area changes along the center line X1 of the soundtrack 5 according to changes in the audio signal. Soundtrack 5 shows the exposure trajectory 6 that changes around .
Record above.

The exposed film is chemically fixed, and as a result, the exposure trajectory 6 forms a transparent portion 7A, and the boundary line between the transparent portion 7A and the opaque portion 7B corresponds to the change in the audio signal. Waveform 8
will be drawn.

By the way, when recording information in this way,
For example, by fixing the average level position of the recorded waveform 8 to the positions of lines X21 and X22 in Figure 2, this average level position is maintained both when the level of the audio signal is high (Figure 3) and when it is low (Figure 4). X21 and X2
If recording waveform 8 is recorded centering on waveform 2, the area of the transparent portion 7A increases when the audio signal level is low, so harsh noises caused by scratches on the film or dust attached to the film will be reproduced as ground noise. There is a problem with signal mixing. In order to solve this problem, conventionally, the average level positions X21 and X22 of the recording waveform 8 are changed according to the level of the audio signal, and when the signal level of the audio signal is small, the average level positions X21 and X22 of the recording waveform 8 are changed to the center line X1 as shown in FIG. A ground noise reduction circuit 11 as shown in FIG. 7 has been used in which the ground noise reduction circuit 11 is moved closer to the center line X1 but moved away from the center line X1 as shown in FIG. 6 when the signal level of the audio signal increases.

The ground noise reduction circuit 11 receives the input audio signal S.
1 is applied to a full-wave rectifier circuit 14 via an input amplifier circuit 12 and a transformer 13. Its rectified output S
2 is smoothed in a smoothing circuit 15, and a level detection signal S3 corresponding to the signal level of the input audio signal S1 is obtained at its output terminal. This level detection signal S3 is applied to the adder circuit 17 via the inverting amplifier circuit 16 and added to the input audio signal S1, and the added output thus obtained is sent to the galvanometer as the average level position signal S4.

In the configuration shown in FIG. 7, when the signal level of the input audio signal S1 decreases, the level detection signal S3 decreases accordingly, thereby increasing the average level position signal S4, and thus the average of the recorded waveform 8 on the soundtrack 5. Level positions X21 and X22
is changed so as to approach the center line X1 as shown in FIG. On the other hand, when the signal level of the input audio signal S1 increases, the level detection signal S3 increases accordingly, causing the average level position signal S4 to decrease, and thus the average level position X21 of the recorded waveform 8 on the soundtrack 5. and X22
is changed away from the center line X1 as shown in FIG.

In this way, when an input audio signal S1 as shown in FIG. Approximately 20 m _s for a change in signal level
_ec ] A level detection signal S3 (FIG. 8B) that changes with a certain delay is obtained, and the average level positions X21 and X22 of the recorded waveform 8 of the soundtrack 5 are corrected according to the change in the signal level of the audio signal S1. Thus, when the signal level is low, the exposure area of the exposure locus 6 becomes narrower, thereby making it possible to reduce the occurrence of ground noise.

However, the conventional configuration shown in FIG. 7 has the following drawbacks, and is therefore still functionally insufficient as a ground noise reduction circuit 11.

The first drawback is that with respect to the waveform of the level detection signal S3 output from the smoothing circuit 15, if the signal level of the input audio signal S1 changes suddenly, the waveform of the level detection signal S3 changes smoothly in response. Instead, a blunt, sharp inflection point portion K1 is formed.
When the level detection signal S3 changes suddenly in this way, the amplitude of the recorded waveform 8 on the soundtrack 5 suddenly moves, and at the same time the average level positions X21 and X22 suddenly move away from the center line X2. This results in waveform 8 being distorted. When this waveform distortion is reproduced, a pop noise that sounds like a ``pop'' or ``pop'' is included in the reproduced sound. However, generally when the sound starts to be generated, the input audio signal S1
Since the signal level often rises rapidly, there are many opportunities for this pop noise to occur, causing a loss in sound quality.

The second drawback is that when the signal level of the input audio signal S1 changes, the response change of the level detection signal S3 obtained from the smoothing circuit 15 is approximately 20 m _se
c ] Because there is a delay of about Become. As a result, the recording waveform 8 corresponding to the rising portion of the signal level of the input audio signal S1 is distorted, making it impossible to obtain a reproduced signal faithful to the input audio signal S1.

Furthermore, the third drawback is that the frequency characteristic of the configuration shown in Figure 7 is 20% when a white nozzle is provided at the input end.
It exhibits a characteristic in which components of ~60 [Hz] are attenuated by about 20 to 40 [dB] and remain. Therefore, this low frequency component is recorded and reproduced superimposed on the audio signal, resulting in distortion of the reproduced signal. Incidentally, in order to avoid this, it may be possible to select the cutoff frequency of the smoothing circuit 15 to be low, but in this case, the response characteristics will be further delayed, which will exacerbate the above-mentioned second drawback, which is not desirable. do not have.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and
The present invention attempts to obtain an information recording device free from the above-mentioned drawbacks by effectively eliminating sharp inflection points in the waveform of a level detection signal without causing overmodulation due to response delay. .

[Summary of the invention]

In order to achieve this purpose, the present invention includes:
When a change in the signal level of an input audio signal is detected, the detected signal is double integrated to obtain an average level position signal.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 9, 21 is a level detection circuit;
As shown in FIG. 10A, the input audio signal S11 is compared with the large level reference signals L11, L12 and the small level reference signals L21, L22, and the input audio signal S11 is
When the signal level of the input audio signal S11 is large, as shown in FIG. 10B, the input audio signal S11 becomes the positive high level reference signal L.
The high level detection signal S rises to the logic "H" level in the section higher than 11 and the section where the input audio signal S11 is lower than the negative large level reference signal L12, and falls to the logic "L" level in the other sections.
Send 12. Also, when the signal level of the input audio signal S11 is high or at a medium level, the first
As shown in FIG. A small level detection signal S13 that falls to the logic "L" level is sent out in other sections.

Thus, as shown in FIG. 10A, the audio signal S
11 is in the large signal level section W1 (the amplitude of the audio signal S11 is in the large level reference signal L11, L1
2), logic "H" pulses are generated one after another as the large level detection signal S12 and the small level detection signal S13 (FIG. 10B and C). Further, when the audio signal S11 is in the medium signal level section W2 (when the amplitude of the audio signal S11 is in the level range between the large level reference signals L11, L12 and the small level reference signals L21, L22),
Logic "H" pulses are generated one after another as the small level detection signal S13 (FIG. 10C), whereas the large level detection signal S12 maintains the logic "L" level (FIG. 10B). Furthermore, when the audio signal S11 is in the small signal level section W3, the large level detection signal S12 and the small level detection signal S13 maintain the logic "L" level (FIGS. 10B and C).

The large level detection signal S12 and the small level detection signal S13 are applied to serialization circuits 22 and 23 having a retriggerable mono-multivibrator configuration. The serialization circuits 22 and 23 are repeatedly triggered each time, for example, by the rising edge of each pulse sent out as the large level detection signal S12 and the small level detection signal S13. Thus, when the pulse arrives as the large level detection signal S12, the continuity circuit 22 becomes a positive potential (for example, +2.5 [V]) corresponding to the logic "H" level, and when the pulse arrives as the large level detection signal S12. When the voltage has not arrived, the continuation signal S14 (FIG. 10D) having a potential corresponding to the logic "L" level (for example, 0 [V]) is sent out.

Furthermore, the continuity circuit 23 outputs the small level detection signal S13.
When a pulse has arrived, the potential becomes a potential corresponding to a logic "H" level (for example, 0 [V]), and when a pulse does not arrive as a small level detection signal S13, it becomes a negative potential corresponding to a logic "L" level. A continuous signal S15 (FIG. 10F) having a potential of (for example, -5.0 [V]) is sent out.

These continuous signals S14 and S15 are applied to first stage integration circuits 24 and 25, respectively. Integrating circuits 24 and 25 include amplitude limiting circuits, and thus the integrated output S16 of integrating circuit 24 is
When the continuation signal S14 is at the logic "H" level (that is, +2.5 [V]), the amplitude limit value N1 is maintained as shown in FIG. 10E, and the continuation signal S14
is at the logic "L" level (that is, 0 [V]), maintains 0 [V] as the center level, and the integral output S17 of the integrating circuit 25 is the continuous signal S15.
When is at the logic "H" level (i.e. 0 [V]), the center level is 0 [V] as shown in Figure 10G.
is maintained, and the continuity signal S15 is at logic "L".
The amplitude limit value N2 is maintained at the level (ie, -5 [V]).

In contrast, the continuity signals S14 and S15 fall from the logic "H" level to the logic "L" level,
Or when rising from the logic "L" level to the logic "H" level, the integral output S of the integrating circuits 24 and 25
16 and S17 draw change curves e and g that fall or rise exponentially (Fig. 10E)
and G).

These integral outputs S16 and S17 are connected to the resistor 26
and 27 are added to each other at a summing point 28, thereby producing a summing output S18 which combines the integral outputs S16 and S17 via the center level (0 [V]) as shown by the broken line in FIG. 10H.
is obtained, which is applied to the second stage integration circuit 29.

This second stage integration circuit 29 integrates the value of the addition output S18 at each point in time, and as a result, the 10th
As shown by the solid line in Figure H, the addition output S18
When it reaches the center level of 0 [V], it maintains 0 [V], and when it reaches the first limit value N1, it increases linearly,
When the first limit value N1 falls exponentially to the center level (or vice versa), this is quadratic integrated, and the second limit value N2 is calculated from the center level.
When it falls exponentially (or rises vice versa), it is quadratic integrated and the second limit value N2
When , a second stage integral output S19 that decreases linearly is obtained.

This second stage integrated output S19 is applied to the summing point 31 through the resistor 30, and is added to the audio signal S20 applied to the summing point 31 through the resistor 32.
For example, it is output as a drive signal S21 to a galvanometer. Here, the input audio signal S11 is the analog-digital conversion circuit 35 - digital delay circuit 36 - digital-analog conversion circuit 3
7, and this delayed output S22 is obtained as an audio signal S20 via a buffer amplifier circuit 39. The delay amount of the delay circuit 38 is mainly determined by the first stage integrating circuits 24 and 25,
The second stage integrating circuit 29 selects a value approximately equal to the amount by which the average level position signal S19 is delayed from the input audio signal S11.

Thus, as shown in FIG. 10I, the film 40 has average level positions X41 and X42 that change symmetrically across the center line X3 in response to the average level position signal S19 obtained from the second stage integrating circuit 29.
An exposure locus 42 is obtained by exposure-recording a recording waveform 41 centered at .

In the above configuration, when the signal level of the input audio signal S11 changes from high level to medium level to low level as shown in sections W1, W2, and W3 in FIG. 10A, the level detection circuit 21 responds. The output S14 of the continuity circuit 22 is theoretically “H” (+2.5
[V]), "L" (0 [V]), and "L" (0 [V]) (Fig. 10D), and the continuity circuit 23
Output S15 of logic “H” (0 [V]), “H” (0 [V])
[V]), "L" (-5 [V]) (Fig. 10F). Therefore, the output S of the first stage integrating circuit 24
16 is the first limit value N1, center level (0 [V]),
It changes like the center level (0 [V]) (10th
E), the output S17 of the integrating circuit 25 changes from the center level (0 [V]) to the center level (0 [V]) to the second limit value N2 (FIG. 10G).

Here, the outputs S16 and S17 (E and G in FIG. 10) of the integrating circuits 24 and 25 are respectively in the section W
1 to section W2, and falls exponentially when moving from section W2 to section W3, from the center value to second limit value N2. . Therefore, waveform portions j and k at this transition form a sharply changing inflection point.

In this way, the integral output S1 with inflection points j and k
6 and S17 are added at addition point 28,
In order, the first limit value N1, the center value (0 [V]), the second
The addition output S18 changes like the limit value N2 of
(FIG. 10H) is obtained, which is integrated in the second stage integration circuit 29. Of this integral output S19, the portions corresponding to the limit values N1 and N2 linearly rise and fall, and the portion corresponding to the center value (0 [V]) maintains a constant value.

On the other hand, a portion of the integral output S19 corresponding to the exponentially falling waveform portion is double integrated. The waveform portions j and k that result in an inflection point
changes become smoother, losing their sharpness and becoming smoother.

Therefore, the movement of the average level positions X41 and X42 during exposure recording on the film 40 is performed based on this smoothly changing integral output S19 (FIG. 10I), so that the recording waveform 41 of the exposure locus 42
There is no sudden change in the change in , and therefore there is no possibility of distortion such as pop noise occurring in the reproduced audio signal.

In the above case, the signal level of the input audio signal S11 decreases in the order of high level, medium level, and low level. When changing between levels, it similarly operates to prevent pop noise from occurring. For example, the 11th
As shown in FIG.
As shown in FIG. 11B, the average level position signal S19 obtained at the output end of the stage integration circuit 29 has a smooth change in the waveform portion corresponding to the sharp change in the signal level of the input audio signal S11.
As a result, no pop noise occurs in the reproduced audio signal.

In addition, since the change in the average level position signal S19 has become smooth in this way, its frequency characteristics are as shown by curve Q1 in FIG. 12, and when white noise shown by curve Q2 is input, the frequency component, a drop of nearly 50 [dB] is obtained, and therefore the distortion of the reproduced signal (for example, the average level position signal S
It is possible to prevent the occurrence of cross-modulation distortion that may occur when the audio signal S20 is superimposed on the audio signal S20.

Furthermore, the timing of the level change of the input audio signal S11 can be appropriately matched to the change timing of the average level position signal S19 by the delay circuit 38, thereby effectively avoiding the possibility of overmodulation occurring in the exposure trajectory 42. can. Therefore, if retriggerable mono multivibrators are used as the serialization circuits 22 and 23 as in the embodiment of FIG. 9, the pulses of the large level detection signal S12 and the small level detection signal S13 of the level detection circuit 21 The level of the input audio signal S11 is always triggered by the last pulse when the level of the input audio signal S11 is no longer available (this means that the level of the input audio signal S11 has suddenly changed upward or downward). The timing of the change and the fall and timing of the continuous signals S14 and S15 can always be determined by the limited operating time of the mono multivibrator, and therefore, this is necessary when adjusting the timing to prevent overmodulation. It can be done easily. Incidentally, unless a retriggerable serialization circuit is used, the fall of the serialization signal will not be constant and will vary, so there is a risk that the timing will be off and overmodulation will occur.

Although the present invention is applied to the case where exposure recording is performed using a light beam in the above description, the present invention is not limited to this, and may also be applied to cases where a laser beam, an electron beam, etc. are used.
It can be widely applied to exposure recording.

〔Effect of the invention〕

As described above, according to the present invention, a two-stage integrating circuit is provided to obtain a signal level detection signal corresponding to a change in the signal level of an input audio signal, so that the average level position can be adjusted to the signal level during exposure recording. It is possible to prevent exposure recording that causes pop sounds when moving in response to changes in the detection signal. In addition, by making the signal level detection signal change smoothly in this way, it is possible to provide frequency characteristics that do not cause unnecessary distortion, and it is also possible to easily match the timing of the signal level detection signal and the input audio signal. It is possible to obtain an information recording device that can perform various functions.

[Brief explanation of drawings]

Figures 1 to 6 are schematic diagrams for explaining the conventional exposure recording method, Figure 7 is a schematic connection diagram showing a conventional ground noise reduction circuit, and Figure 8 is a signal diagram showing the signals of each part of the circuit. 9 is a waveform diagram, and FIG. 10 is a block diagram showing an embodiment of the information recording device according to the present invention.
The figure shows signal waveform diagrams of each part, Figures 11 and 12.
The figures are a signal waveform diagram and a frequency characteristic curve diagram for explaining the effects. 21... Level detection circuit, 22, 23... Continuation circuit, 24, 25... First stage integration circuit, 29...
...Second stage integration circuit, 38...Delay circuit.

Claims (1)

[Claims] 1. When forming an exposure trajectory by projecting an exposure beam whose width changes in accordance with the input audio signal onto the film, the average level position of the exposure trajectory is controlled according to the signal level of the input audio signal. In the information recording device made, there is provided a level detection circuit that compares the input audio signal with a predetermined reference level signal, a continuation circuit that continuizes the comparison output of this level detection circuit, and a continuation output of this continuation circuit. and a second integrating circuit that integrates the integrated output of the first integrating circuit and sends it out as the average level position signal during exposure recording. Recording device.