JPS58133665A - Reproduction end detector in information reproducer - Google Patents

Abstract

PURPOSE:To detect the end of reproduction surely at the program end independently of the length of recorded program, by detecting that the output erasing state of a comparing means generating an output, when a signal level in response to a reproducing information signal is larger than a prescribed threshold value, continues for a prescribed time or over. CONSTITUTION:A signal demodulated at a signal demodulator 19 is, e.g., a video signal and unnecessary fluctuation of a voltage is eliminated at a clamp circuit 20 as required. Thus, a demodulation signal reproduced to an accurate level is inputted to the 1st comparison circuit having a prescribed threshold value VTH1. The output of the comparator 21 is integrated at a low pass filter 22 and compared with a prescribed threshold value VTH2 at the 2nd comparison circuit 23 and inputted to a timer 24 having a prescribed time constant tau. The timer 24 generates an output detecting that the output erase state of the comparison circuit 23(low level) continues for a prescribed time tau or over, and a discrimination circuit 25 of the next stage generates a reproduction end signal in response to this output.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an endogenous end detection device in a reproducing apparatus for information recording media such as video discs and digital audio discs.

Video discs and digital audio discs have
Video information signals and audio information signals are recorded at high density so that the distance from the electrically connected track is approximately 1 to 2 μm. Therefore, even if these discs are played back at high speed, they can be played back for a long time. Devices that play these discs (hereinafter referred to as players) generally include:
- A so-called playback end detection device is provided to detect when the playback of the disc has ended, and the playback end detection signal output from this playback end detection device is used to stop the rotation of the disc after the end of playback or to stop the disc from repeating playback. It is used as a signal to carry out.

As shown in FIG. 1, the conventional playback end detection device includes a detection switch 3 fixed at a predetermined position in the radial direction of the disk 1, that is, in the moving direction of the pickup section 2, and detects the inner circumference (or Playback starts from the outermost circumference (
or the innermost circumference), and when the reproduction is completed, the detection switch 3 is actuated by the pickup section 2 to generate a reproduction end detection signal, and a controller for controlling the pickup section 2 and the spindle motor 4. The configuration was such that it supplied to 5.

Here, a program with a playback time of about 30 minutes to 1 hour can be recorded on one side of the disc, but the actual length of the recorded program varies depending on the case. The end radius position on the disk differs depending on the Therefore, as shown in FIG. 2, when the actual information recording portion B is smaller than the information recording portion 8 of the disc 1 and the playback time thereof is quite short, the playback end detection device having the above-mentioned configuration In this case, since the detection switch 3 is fixed at the outermost (or innermost) position, it takes a long time to detect the end of playback after the program has finished playing, and the player cannot play any information during this time. Since the disk continues to rotate without any interruption, power consumption is wasted and the user is forced to operate, for example, a playback end switch provided on the operation unit.

In order to eliminate this drawback, it is possible to record an end code using a digital signal on the disk, but adding a device for digital processing would be expensive.
Furthermore, there is a relatively high possibility that malfunctions will occur due to misreading of the code, which is undesirable.

The present invention has been made in view of the above-mentioned points, and provides an optical information reproducing device that can reliably detect the end of playback at the end of a program regardless of the length of the recorded program with an inexpensive configuration. An object of the present invention is to provide a playback end detection device.

The playback end detection device according to the present invention detects that the output disappearing state of the comparison means, which generates an output when the signal level corresponding to the playback information signal is greater than a predetermined threshold, continues for a predetermined time or more, thereby detecting the end of playback. The configuration is such that it makes a determination and generates a reproduction-end detection signal.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a configuration diagram showing an embodiment of the present invention.

In the figure, a light beam such as a laser beam emitted from a light source 11 is incident on an objective lens 14 via a beam splitter 12 and a tracking mirror 13, and is focused onto the information recording surface of a disk 16 that is rotationally driven by a spindle motor 15. has been done. The information recording surface of the disk 16 is made of a vapor-deposited surface of aluminum or the like, and the light beam irradiated onto this recording surface is reflected by convex portions (or concave portions) called bits that form information tracks. be done. This reflected light enters the polarization plane 17 of the beam splitter 12 through approximately the same optical path as that at the time of incidence.
Due to the interaction between the /4 wavelength plate and the coherent nature of the laser light, the light is further reflected at the polarization plane 17 and irradiated onto the light receiving element 18 that performs photoelectric conversion. Since the light irradiated onto the light receiving element 18 is modulated by the bits on the disk 16, its intensity changes at a period corresponding to the presence or absence of the bits. In this way, it is possible to reproduce the high frequency signal recorded on the information recording surface, and the output of the light receiving element 18 is input to the signal demodulator 19 via a head amplifier (not shown) that mainly amplifies the high frequency. Ru.

The signal demodulated by the signal demodulator 19 is, for example, a video signal, and unnecessary fluctuations in voltage are removed by the clamp circuit 20 as necessary. The demodulated signal thus reproduced to an accurate level is input to the first comparator circuit 21 having a predetermined steel wire VTI-11. The output of this comparison circuit 21 is integrated in a low-pass filter 22, and the -second
After being compared with a predetermined threshold value VTH2 by the comparison circuit 23,
The signal is input to a timer circuit 24 having a predetermined time constant τ.

When the timer circuit 24 detects that the output horn disappearing state (low level) of the comparator circuit 23 continues for a predetermined period of time or more, it generates an output, and in response to this output, the next stage discriminating circuit 25 outputs a reproduction end detection signal. Occur.

Next, the operation of this configuration will be explained based on the waveform diagram of FIG. 4. Note that the waveforms shown in FIG. 4 correspond to the symbols shown in FIG. The reproduced RF low signal a) is demodulated by a signal demodulator 19 and output as, for example, a video signal lb). Since this video signal (b) tends to be unstable due to time axis fluctuations, it is clamped to the sync tip level by the clamp circuit 20 (C), the first comparison circuit 2
1 sets the b signal (C) to a predetermined threshold VT corresponding to the Y component.
Only when HI is exceeded, a high level output (d) is generated and supplied to the low pass filter 22. By comparing the output (e) integrated by the O-pass filter 22 with a predetermined threshold value VTH2 in the second comparison circuit 23, a portion without video information (Y component) is detected (f). At this time, even during the regular program, the video information signal reaches the predetermined threshold value V.
It is possible that the TI-12 may be rotated once (for example, when the entire screen becomes completely black), so only if no video information is detected for a relatively long time τ after the video information disappears. A timer circuit 24 is provided to detect the end of reproduction, and this timer circuit 24 outputs a high level output (0) when a time τ has elapsed since the output (f) of the comparison circuit 23 transitioned to a low level. Occur.

The determination circuit 25 determines that the reproduction has ended upon generation of this output (a), and generates a reproduction end detection signal.

In this way, after the program signal ends, a horizontal synchronization signal, a color burst signal, and a black level signal are sequentially sent out.If a so-called black burst signal is recorded, if an unmodulated signal is recorded, or if the pit is In the case of a so-called mirror state in which no
Therefore, it is possible to accurately generate a reproduction end detection signal.

The discrimination circuit 25 is constituted by a flip-flop etc. which is reset when the player is initialized. Further, various applications are conceivable, such as not only stopping the rotation of the disk in response to the reproduction end detection signal, but also performing a repeat reproduction operation.

According to the present invention, it is possible to reliably detect the end of a program signal with an inexpensive configuration, and it is particularly effective when the program signal ends in the middle of the recording surface of a disk.

In the above embodiment, the case where the present invention is applied to a video disc player has been described, but the present invention is not limited to this, but can be applied to a wide range of information recording medium playback devices such as digital audio disc players. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional example, Fig. 2 is a plan view showing a program recording state of a disk, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is a block diagram showing an embodiment of the present invention. FIG. 3 is a waveform diagram for explaining the operation. Explanation of the signs of the main negative part 1.16... Disk, ′ ″ ″ 2... Pickup section ・ ;1. . 3... Detection switch 11... Light source 12... Beam splitter 14... Objective lens 18... Light receiving element 19...・Signal demodulator 21.23... Comparison circuit

Claims (1)

[Claims] Comparing means for generating an output when a signal level corresponding to a reproduction information signal is higher than a predetermined threshold; and detecting means for detecting each time an output disappearing state of the comparing means continues for a predetermined time or more, A playback end detection device for an information playback device, characterized in that the output of the means is derived as a playback end detection signal.