JPH07270946A - Reproducing device and recording method as well as recording medium - Google Patents

Abstract

PURPOSE:To realize a reproducing device, recording method and recording medium capable of markedly lowering an error rate. CONSTITUTION:The reproducing device 10, recording method and recording medium capable of markedly lowering the error rate are realized by setting the length of the second dots in the arranging directions of the first and second dots larger than the length of the first dots at the time of forming the first dots to allow transmission of light and the second dots to shield the light on the translucent recording medium and recording digital information by combination of the arrangement of the first and second dots and setting the slice level at the time of reproducing the digital information by irradiating the recording medium with light and subjecting the transmitted light to photoelectric conversion by using a photoelectric conversion means 23, at <50[%] when the signal level corresponding to the first dots among the outputs of the photoelectric conversion means 23 is set at 100[%] and the signal level corresponding to the second dots at 0[%].

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial Application Conventional Technology (FIGS. 17 and 18) Problem to be Solved by the Invention (FIGS. 17 and 18) Means for Solving the Problem (FIGS. 1 to 16) Action (FIGS. 1 to 16) Example (1) Overall structure of reproducing apparatus (FIGS. 1 to 4) (2) Structure of movie film (FIGS. 5 to 13) (3) Operation of example (FIGS. 1 to 15) (4) Implementation Effects of Examples (FIGS. 1 to 15) (5) Other Examples (FIGS. 1 to 16) Effects of the Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus, a recording method and a recording medium, for example, a reproducing apparatus for a movie film,
And a recording method for recording digital data on a movie film, and a method suitable for application to a movie film.

[0003]

2. Description of the Related Art Conventionally, as shown in FIG. 17, a 35 [mm] movie film 1 used in a movie theater has feed holes (hereinafter 2 are sequentially provided at a predetermined interval, and a row of these two perforations 2 (hereinafter referred to as a first and a second perforation row, respectively) 3A, 3B. Image information and audio information consisting of analog signals are optically recorded in predetermined areas 4 and 5 of the film 1 sandwiched therebetween. In this case, in the movie film 1 of this type, areas outside the perforation rows 3A and 3B in the width direction (hereinafter, referred to as outside areas of the perforation rows 3A and 3B) 6A and 6B are usually used. Area between each perforation 2 (hereinafter referred to as inter-perforation area) 7
There is no signal recorded in.

Therefore, in this type of movie film 1, conventionally, the digitalized audio information and the like in these areas 6A, 6B and 7 are white (the portion where the film is not exposed).
It has been proposed to improve the sound quality of reproduced sound by optically recording with a binary pattern of black and black (a portion where the film is exposed) (Japanese Patent Application No. 4-356935, International Patent No. WO92). / 14239).

[0005]

By the way, in the conventional reproduction of a digital signal recorded on an optical disk or the like, it is judged whether the digital information detected from the recording medium is a logical "1" or a logical "0". A threshold value (hereinafter, referred to as a slice level) is set to 100 [%], which is a signal level corresponding to the middle level of the eye pattern, that is, the logic "1" of the reproduction signal before binarization, and the logic "0". Is set to a value corresponding to 50 [%] when the signal level corresponding to is set to 0 [%].

In this case, in reproduction on such a recording medium, even if dust, scratches, defects during formation, etc. are present on the signal recording surface of the disk, these are both logic "1" and logic "0". Even if the slice level is set in this way, it will cause no noise, and no problem occurs. However, in reproducing the digital information recorded in the movie film 1 in a binary pattern of white and black as described above, the movie film 1 is illuminated and the transmitted light is observed to obtain the digital information. Dust, scratches, and defects during printing block off the light due to the fact that the white part (hereinafter referred to as white dot) is erroneously detected as black (hereinafter referred to as black dot). It is easy to occur. Therefore, in the reproduction of such digital information,
There is a problem that noise is likely to occur in the reproduction information corresponding to the white dots in the reproduction signal.

That is, the reproduction signal obtained by reproducing the digital information optically recorded on the movie film 1 as described above is plotted on the horizontal axis, and the white dot is represented by a logical "1" (100 [% ]), The black dot is a logical "0" (0
Looking at the logic level when [%]) is plotted along the vertical axis, as is clear from the photograph in FIG. 18,
It can be seen that a lot of noise exists on the white dot side (upper side in FIG. 18). Therefore, the above-mentioned movie film 1
In the reproduction of the digital signal recorded in (3), if the slice level is set in the middle of the eye pattern, it is likely to be affected by these noises, and the error rate during reproduction becomes high.

The present invention has been made in view of the above points, and an object thereof is to propose a reproducing apparatus, a recording method, and a recording medium capable of significantly reducing the error rate.

[0009]

In order to solve such a problem, in the present invention, digital information is transmitted by a combination of an arrangement of a first dot 41 which transmits light and a second dot 40 which blocks light. Recorded translucent recording medium 11
In a reproducing device that irradiates light to the optical recording medium 11 and reproduces digital information based on the transmitted light L2 of the light L1 transmitted through the recording medium 11, photoelectric conversion means 23 for photoelectrically converting the transmitted light L2,
A digitalization means 30 for reproducing the digital information by binarizing and digitizing the output of the photoelectric conversion means 23 is provided, and the slice level when the output of the photoelectric conversion means 23 is binarized in the digitalization means 30 is provided. , The signal level corresponding to the first dot 41 of the output of the photoelectric conversion means 23 is set to 100 [%], and the second dot 40
50% when the signal level corresponding to is set to 0%
Set to less than.

Further, in the present invention, the slice level is set within the range of 20% to 40% of the signal level corresponding to the first dot 41 in the output of the photoelectric conversion means 23.

Further, in the present invention, a first dot 41 that transmits light and a second dot 40 that blocks light are formed on the semitransparent recording medium 11, and the first and second dots 4 are formed.
In the recording method for recording digital information by the combination of the arrangements of 1 and 40, the first and second dots 4 are
The length of the second dot 41 in the arrangement direction of 1 and 40 is made larger than the length of the first dot 40.

Further, in the present invention, in the semitransparent recording medium 11 in which the digital information is optically recorded by the combination of the arrangement of the first dot 41 which transmits light and the second dot 40 which blocks light, First and second dots 4
The length of the second dot 41 in the arrangement direction of 1 and 40 is made larger than the length of the first dot 40.

Further, in the present invention, the recording medium is the movie film 11, and the digital information is digitalized audio information.

[0014]

In the first aspect of the invention, the slice level when the output of the photoelectric conversion means 23 is binarized by the digitalization means 30 is defined as the first dot 4 of the output of the photoelectric conversion means 23.
The signal level corresponding to 1 is set to 100 [%] and the signal level corresponding to the second dot 40 is set to less than 50 [%] when it is set to 0 [%]. It is possible to make it less susceptible to noise caused by dust attached to the first dot 41 and scratches formed on the first dot 41.

Further, in the second invention, the length of the second dot 41 in the arrangement direction of the first and second dots 41, 40 is made larger than the length of the first dot 40. The cross zero level of the eye pattern of the reproduction signal S4 before binarization can be matched with the slice level during reproduction.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) Overall Structure of Playback Device In FIG. 1, reference numeral 10 denotes a playback device as a whole, which can play back the digital information recorded in the movie film 11. That is, in the movie film 11, the parts corresponding to those in FIG.
As shown in FIG. 3, the digital sound track 12 is placed in the outer area 6A, 6B of each perforation row 3A, 3B.
A and 12B are respectively provided, and the digital sound information (hereinafter referred to as digital sound information) and tracking information in the digital sound track are white as shown in FIG. 3 (the film is not exposed). Area) and black (the area where the film is exposed), and is optically recorded with a 2-dimensional area of 3 dots × 3 tracks as 1 byte.

The movie film 11 is sequentially fed at a predetermined traveling speed in the traveling direction indicated by an arrow a by a film feeding mechanism (not shown in FIG. 1). Therefore,
As is clear from this, in this reproducing apparatus 10, the light source 2
The light source light L1 emitted from 0 is condensed using the optical system 21 composed of a condensing lens or the like, and is irradiated to the digital sound track 12A (12B) from one side of the movie film 11 and transmitted at this time. The light L2 is focused on the light receiving surface of the array CCD 23 using the optical system 22. In this case, as shown in FIG. 4, the CCD 23 sequentially scans at a timing based on the timing signal S1 supplied from the vertical synchronizing circuit 31 of the signal processing unit 30 to obtain an RF obtained based on the transmitted light L2.
The signal S2 is sent to the vertical synchronizing circuit 31 and the low-pass filter circuit 3
2 and so on.

The vertical synchronizing circuit 31 generates the above-mentioned timing signal S1 on the basis of the RF signal S2, and sequentially outputs this timing signal CC.
Send to D23. The low-pass filter circuit 32 is
A low-frequency signal component is extracted from the RF signal S2, and this is RF
The low-frequency signal S3 is sent to the AGC / auto bias circuit 33, and the AGC / auto bias circuit 33 outputs R
After the F low frequency signal S3 is amplified to a signal of a predetermined level, it is sent to the level comparator 34 as a comparison target signal S4.
At this time, when the signal level of the comparison target signal S4 with respect to the white dot is 100 [%] and the signal level with respect to the black dot is 0 [%], the level comparator 34 sets the signal level of the white dot to 30 [%]. ] A comparison reference signal S5 having a signal level corresponding to the above is sequentially supplied from the slice level setting unit 35.

Thus, the level comparator 34 binarizes the comparison target signal S4 with the signal level of the comparison reference signal S5 as the slice level by sequentially comparing the signal levels of the comparison reference signal S5 and the comparison target signal S4. The binary signal S6 of the logical level obtained as a result is applied to the horizontal synchronizing circuit 36.
And the signal input terminal of the D flip-flop circuit 37. The horizontal synchronizing circuit 36 generates a clock of a predetermined frequency based on the binarized signal S6 and sends it to the clock input terminal of the D flip-flop circuit 37 as a channel clock signal S7.

Further, the D flip-flop circuit 37 sends the data based on the binarized signal S6 one bit at a time to the 9-8 conversion circuit 38 at a timing based on the clock frequency of the channel clock signal S7 as the reproduction digital signal S8. . 9-8 conversion circuit 38 reproduces digital signal S
The 9-bit data obtained based on 8 is converted into 8-bit data, and this is sent to the error correction circuit 39 as a modulated reproduction digital signal S9. Thus, in the reproducing apparatus 10, the error correcting circuit 39 thereafter performs the predetermined signal processing on the modulated reproduced digital signal S9 to obtain the final reproduced signal S10, and the reproduced sound is presented based on the reproduced signal S10. It is designed to let you.

(2) Structure of movie film In reproducing the digital information of this type, when the slice level is shifted from the middle level of the reproduced signal when binarizing the reproduced signal, the center of the eye pattern (cross zero). The level (hereinafter referred to as the cross zero level) and the slice level do not match, resulting in weaker defocusing or a narrower phase margin (weaker to jitter) and other playback conditions during playback. I have a problem to do. Therefore, in this movie film 11, as shown in FIG. 5 (A), the digital sound track 1
The black dots 40 and the white dots 41 are formed such that the length of the black dots 40 in the track direction of 2A and 12B (the CCD line direction) is larger than the length of the white dots 41 by a predetermined amount.

By doing so, FIG.
This is because the center of the eye pattern of the comparison target signal S4 can be made to coincide with the slice level of the reproducing apparatus 10 as shown in (B), which deteriorates the reproducing condition when reproducing the digital audio information in this movie film 11. It is designed so that it can be prevented. In practice, in the movie film 11, the read digital audio information is the optical systems 20 to 22 and the low pass filter circuit 3 of the reproducing apparatus 10.
2 (hereinafter, these are collectively referred to as reproduction systems 20 to 32)
In consideration of the limitation of the pass frequency band in the above, the magnitude of the duty of the black dot 40 in the track direction of the digital sound tracks 12A and 12B is determined by the following procedure.

That is, a data string to be recorded is shown in FIG.
In the case of (A), first, each sample (“1” or “0”) of the data string 50 is arranged by a predetermined number of times to create a data string 51 as shown in FIG. 6B (in this case, By arranging 16 times each), and by replacing a predetermined number from the end of each sample group in the array of “1” corresponding to “1” in FIG. For example, a data string 52 as shown in FIG. 6C is created (in this case, the last three “1” s are replaced with “0” s). Incidentally, the data string 52 of FIG.
6A, when optically recording the data string 50 of FIG. 6A on the movie film 11, the size of the white dot 41 is reduced to 13/16, and the duty of the white dot 41 is set to about 40%. This corresponds to the recording pattern in the case.

Next, a fast Fourier transform (FFT) is applied to the data string 52 of FIG. 6C to obtain the spectrum of the recording pattern as shown in FIG.
The spectrum of the waveform of the comparison target signal S4 (FIG. 4) is calculated by multiplying by 32 pass frequency bands. In this case, for example, assuming that the pass frequency band of the reproduction systems 20 to 32 has a 100 [%] roll-off characteristic toward the frequency twice the clock frequency of the timing signal S1 (FIG. 4) as shown in FIG. The waveform spectrum of the target signal S4 is as shown in FIG. Further, a fast inverse Fourier transform (IFFT) is applied to this, and the obtained waveform is overwritten for each detection window width (or an integral multiple thereof) to obtain an eye pattern of the comparison target signal S4 as shown in FIG. Then, the cross zero level of the eye pattern of the comparison target signal S4 in this duty is detected from the eye pattern.

In this way, in the work of determining the duty of the black dot 40 of the movie film 11, the same calculation is executed for various duties to determine the cross zero level of the eye pattern of the comparison target signal S4 in each duty. Sequential detection is performed, and the duty of the black dot 40 is determined from the detection result so that the cross zero level of the eye pattern of the comparison target signal S4 matches the slice level (30 [%] in the case of logic "1" in this embodiment). is doing. For example, when the pass frequency bands of the reproduction systems 20 to 32 have the characteristics as shown in FIG. 8, the same calculation as described above is sequentially performed on the data string 50 of FIG. The ideal slice level (that is, the cross zero level of the eye pattern) is sequentially plotted for each duty, and a graph as shown in FIG. 11 is obtained.

Therefore, as is clear from this graph,
In the reproduction systems 20 to 32 of such a pass frequency band, when the slice level is set to 30 [%], when reproducing the digital audio information recorded in the movie film 11, white dots 40 in the track direction at the time of recording are reproduced. The duty of 40
It can be seen that the digital information can be reproduced in an optimum state by setting [%].

In the case of the embodiment, as a means for recording the digital audio information on the movie film 11 so that the duty of the white dot 41 in the track direction becomes small, a plurality of LEDs 60 as shown in FIG. 12 are arranged at predetermined intervals in the track direction. The LED array 61 is formed by opening and sequentially arranging. Here, usually, a movie film uses a picture negative film in which only the picture of the movie is recorded and a sound negative film in which only the sound of the movie is recorded. ) Are printed so that they match.

Therefore, when the digital audio information is recorded on the movie film 11, each L of the LED array 61 shown in FIG.
By sequentially blinking the ED 60 based on the supplied digital audio information as necessary (in FIG. 12, it is assumed that the shaded LED 60 emits light), so that FIG.
As shown in FIG. 13B, the negative film 62 is exposed, and the negative film 62 is used to expose the positive film 63 (that is, the film that becomes the movie film), as shown in FIG. 13B. The black dots are larger than the white dots.

In this case, each LED 60 of the LED array 61
The size of the interval is selected so that the cross zero level of the eye pattern of the comparison target signal S4 matches the slice level (30 [%] in the case of the logic "1" in this embodiment). Thus, it is possible to prevent weakening of the differential focus during reproduction, or narrowing of the phase margin of the comparison target signal S4.

(3) Operation of the Embodiment With the above configuration, the CCD 23 in this reproducing apparatus 10
Comparison target signal S4 based on the RF signal S2 output from
Is a slice level corresponding to 30% when the signal level corresponding to the white dot 41 in the comparison target signal S4 is 100% and the signal level corresponding to the black dot 40 is 0%. Binarize with. Therefore, this playback device 1
When it is 0, it is difficult to be influenced by noise generated on the white dot 41 side of the comparison target signal S4, and as a result, the digital audio information optically recorded on the movie film 11 can be reproduced at a low error rate.

In practice, the dot size is 18 × 18 [μm ² ],
For three formats of 24 × 24 [μm ² ] and 36 × 36 [μm ² ], the byte error rate is changed by sequentially changing the ratio of the slice level to the signal level of the white dot 41 of the digital audio information recorded in the movie film 11. As a result of measurement, a graph as shown in FIG. 14 was obtained. As is clear from this graph, the slice level that gives the optimum value of the error rate is around 30% of the signal level corresponding to the white dot 41 in the reproduced signal before binarization,
By setting the slice level in this way, it has been found that the error rate can be improved by one digit as compared with the conventional case.

In order to binarize the slice level, the signal level corresponding to the white dot 41 of the previous reproduced signal is 30
Setting around [%] has an advantage of widening the management margin (allowable range) of the film concentration during film production. In other words, as a sound negative film, "EASTMAN Digital
"Sound Recording Film 2374 (35mm)" (manufactured by Kodak Co.) and used as a positive film "EASTMAN Co
lor Print Film 5384 (35mm) "(manufactured by Kodak Co., Ltd.) and slice levels of 42% (f1) and 32% (f
2) and 22 [%] (f3), the error rate was measured while sequentially changing the density of the black film 40 of the positive film (hereinafter referred to as the positive density). As a result, a graph as shown in FIG. was gotten.

In this case, as is apparent from the graph, the minimum value of the error rate is the smallest when the slice level is 32%, and the minimum value of the error rate becomes larger as the slice level becomes larger or smaller than 32%. The size of the minimum value gradually increases. Therefore, the margin of positive density for making the error rate during playback to the normal level (about 10 ^-2 units) can be widest when the slice level is about 20 to 40 [%]. It is possible to widen the margin of the film density management.

In this experiment, the size of the black dots 40 was set to 18 × 18 [μm ² ] and the density of the black dots of the negative film (hereinafter referred to as the negative density) was set to 2.6. Also, as a place to measure the positive density, All at the top of the negative film
One (all black) and All Zero (all white) areas are provided, the negative density measures the density of All One (all black) area, and the positive density is the All Zero (all white) area of the negative film, that is, the positive film. The density of the All One (all black) area was measured. Further, in this movie film 11, the duty of the black dot 40 in the track direction of the digital sound tracks 12A and 12B is increased so that the cross zero level of the eye pattern of the comparison target signal S4 coincides with the slice level in the reproducing system. By doing so, it is possible to prevent the phase margin at the time of reproduction from becoming narrow and from becoming weak to the differential focus. Therefore, it is possible to prevent the reproduction condition from being deteriorated during reproduction.

(4) Effect of Embodiment According to the above configuration, the slice level is compared with the comparison target signal S.
By setting the signal level to about 30% of the signal level for the white dot 41 of No. 4, when reproducing the digital audio information from the movie film 11, the dust and white on the white dot 41 of the movie film 11 are reproduced. It is possible to reduce the influence of noise caused by scratches and the like formed on the dots 41, and thus to realize a reproducing device capable of significantly reducing the error rate.

When the movie film 11 is recorded, the length of the black dot 40 in the track direction of the digital sound tracks 12A and 12B is set to a predetermined amount larger than the length of the white dot 41 depending on the pass frequency band of the reproducing apparatus 10. By making the length longer, the slice level at the time of reproducing the digital audio information and the cross zero level of the eye pattern of the comparison target signal S4 can be matched, thus preventing the reproduction condition at the time of reproduction from deteriorating. can do.

(5) Other Embodiments In the above-described embodiments, the case where the slice level during reproduction is set to 30% has been described, but the present invention is not limited to this, and the point is to slice. The level is shifted from the black dot 40 side so as to match the cross zero level of the eye pattern of the comparison target signal S4 (that is, the signal level corresponding to the white dot 41 in the comparison target signal S4 is set to 100 [%], and the black dot If the signal level corresponding to 40 is less than 50% when the signal level is 0%, the slice level may be other than 30%.

Also in this case, if the slice level is set to about 20 to 40% of the signal level corresponding to the white dot 41 in the comparison target signal S4, almost the same effect as the above embodiment can be obtained. .

In the above embodiment, the case where the first invention is applied to the reproducing apparatus for the digital audio information recorded on the movie film 11 has been described.
The present invention is not limited to this, and the point is that a semitransparent recording medium on which digital information is optically recorded is irradiated with light by a first dot that transmits light and a second dot that blocks light to transmit the transmitted light. If it is a reproducing device that reproduces the digital information by observing
It is also suitable for being applied to various reproducing apparatuses.

Further, in the above-described embodiment, when the digital audio information is recorded on the movie film 11, FIG.
Although the case where two LED arrays 61 are used has been described, the present invention is not limited to this, and the spatial light modulator 80 in which the shutter windows 80A by electro-optical elements as shown in FIG. 16 are arranged in two stages, for example. May be used.

Further, in the above-mentioned embodiment, the case where the second invention is applied to the movie film 11 has been described, but the present invention is not limited to this, and the point is that the first dot that transmits light is used. The present invention can be applied to various other recording media as long as it is a semi-transparent recording medium in which digital information is optically recorded by the combination of the arrangement of the second dot for blocking light and the second dot.

Further, in the above-described embodiment, the second aspect of the present invention is that the digital audio information is used for each perforation sequence 3
The digital audio information recorded in the outer areas 6A, 6B of A, 3B or the relevant digital audio information is recorded in each perforation sequence 3A, 3B.
The case where the invention is applied to the movie film 11 recorded in the outer areas 6A and 6B of B has been described, but the present invention is not limited to this, and the digital information is recorded in the inter-perforation area 7, for example. It can also be applied to movie films.

[0044]

As described above, according to the first aspect of the invention, the semitransparent digital information is optically recorded by the combination of the arrangement of the first dot that transmits light and the second dot that blocks light. In the reproducing apparatus for irradiating the recording medium with light and reproducing the digital information based on the transmitted light of the light transmitted through the recording medium, a slice for binarizing the output of the photoelectric conversion means for photoelectrically converting the transmitted light. The signal level corresponding to the first dot in the output of the photoelectric conversion means is set to 100.
[%] And the signal level corresponding to the second dot is set to less than 50 [%] when the signal level is 0 [%]. It is possible to reduce the influence of noise caused by the scratch formed on the first dot, and thus it is possible to realize a reproducing device capable of significantly reducing the error rate.

According to the second aspect of the invention, the first dot that transmits light and the second dot that blocks light are formed on the semitransparent recording medium, and the first dot and the second dot are arranged. When recording digital information by combination, the first and second
By making the length of the second dot in the array direction of the dot larger than the length of the first dot, the crossing of the slice level at the time of reproducing the digital information and the eye pattern of the reproduced signal before binarization. It is possible to realize a recording method and a recording medium that can be matched with the zero level, and thus can significantly reduce the error rate while preventing the reproduction condition during reproduction from being deteriorated.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a reproducing apparatus according to an embodiment.

FIG. 2 is a plan view showing a structure of a movie film according to an embodiment.

FIG. 3 is a plan view for explaining a digital sound track of a movie film.

FIG. 4 is a block diagram showing a configuration of a signal processing unit.

FIG. 5 is a plan view for explaining the configuration of the digital sound track and a characteristic curve diagram showing an eye pattern at this time.

FIG. 6 is a schematic diagram showing an example of a data sequence recorded in a movie film.

FIG. 7 is a characteristic curve diagram showing a spectrum of a recording data pattern.

FIG. 8 is a characteristic curve diagram showing an example of a pass band limiting characteristic of a reproducing system.

9 is a characteristic curve diagram showing a spectrum of a comparison target signal subjected to pass band limitation in FIG.

10 is a characteristic curve diagram showing an eye pattern of a comparison target signal subjected to pass band limitation in FIG.

FIG. 11 is a characteristic curve diagram showing the optimum slice level of the comparison target signal subjected to the pass band limitation of FIG. 8 corresponding to each duty of black dots.

FIG. 12 is a schematic plan view showing an example of recording means for digital audio information.

13 is a schematic plan view showing a negative film on which digital audio information is recorded by using the LED array of FIG. 12 and a positive film on which the digital audio information is recorded by using the negative film. is there.

FIG. 14 is a characteristic curve diagram showing a relationship between an error rate and a slice level in each format.

FIG. 15 is a characteristic curve diagram showing the relationship between the error rate and the positive density at each slice level.

FIG. 16 is a schematic plan view showing another embodiment.

FIG. 17 is a schematic plan view showing the structure of a conventional movie film.

FIG. 18 is a photograph showing an oscilloscope waveform for explaining noise generated in a reproduced signal.

[Explanation of symbols]

1, 11 ... Movie film, 12A, 12B ... Digital sound track, 10 ... Playback device, 23 ... C
CD, 30 ... Signal processing unit, 32 ... Low-pass filter circuit, 33 ... AGC / auto bias circuit, 34 ...
Level comparator, 35 ... Slice level setting unit, 37 ...
… D flip-flop circuit, 38 …… 9-8 conversion circuit, 4
0 ... Black dot, 41 ... White dot, S2 ... RF signal, S4 ... Comparison target signal, S5 ... Comparison reference signal.

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[Procedure amendment]

[Submission date] July 15, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 18

[Correction method] Change

[Correction content]

FIG. 18

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G11B 20/10 321 A 7736-5D

Claims (5)

[Claims] 1. A semitransparent recording medium on which digital information is optically recorded is irradiated with light by a combination of a first dot that transmits light and a second dot that blocks light, and the recording is performed. In a reproducing apparatus for reproducing the digital information based on the transmitted light of the light transmitted through the medium, a photoelectric conversion means for photoelectrically converting the transmitted light and an output of the photoelectric conversion means are binarized to be digitalized. Digital output means for reproducing the digital information, and the slice level at which the output of the photoelectric conversion means is binarized by the digital conversion means is the first slice of the output of the photoelectric conversion means. The signal level corresponding to the dot is set to 100%, and the signal level corresponding to the second dot is set to less than 50%, which is 0%. That playback device. 2. The slice level is set within a range of 20% to 40% of a signal level corresponding to the first dot in the output of the photoelectric conversion means. The reproducing device according to claim 1. 3. A digital information is formed by forming a first dot for transmitting light and a second dot for blocking light on a semitransparent recording medium, and combining the first and second dots. In the recording method for recording, the length of the second dot in the arrangement direction of the first and second dots is made larger than the length of the first dot. 4. A first dot that transmits light and a second dot that blocks light.
In a semitransparent recording medium in which digital information is optically recorded by a combination of the arrangement of the first dot and the second dot, the length of the second dot in the arrangement direction of the first and second dots is set to the first dot. A recording medium characterized by having a length larger than the length. 5. The recording medium according to claim 4, wherein the recording medium is a movie film, and the digital information is digitalized audio information.