JPH0145124B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic music selection detection device used in a record player.

The automatic music selection detection device is used to select and reproduce a desired music piece from among a plurality of music pieces recorded on the same side of a record.

As a means of selecting a desired track, light from a light source is irradiated onto the record, and the reflected light is incident on a photoelectric conversion device, which selects the recording band where the track is recorded, that is, the location where the sound groove is, and the space between each track. The non-recording zone, that is, the area without a sound groove, is detected by a detection device using a change in the level of the conversion output of the photoelectric conversion device caused by the difference in reflectance, and each of the recording zones is assigned an address. The music is stored in a storage device, the address corresponding to the desired song is read out as appropriate, and a drive device linked to the tone arm is driven based on the readout output.

For example, a conventional automatic music selection detecting device 20 configured as shown in FIG. The light reflected from the sound groove is converted into an electrical signal by a photoelectric conversion element. The conversion output of the photoelectric conversion element 4 is:
The signal is amplified by a preamplifier 5. The output of the preamplifier 5 is divided into a signal that is directly extracted and a signal that is extracted from the output of the preamplifier 5 via an integrating circuit 6, and each signal is differentially amplified. Vessel 7
is supplied to

The output of the differential amplifier 7 is compared with a predetermined comparator level in a level comparator 8, and the output exceeding this comparator level is taken out as an output.

The output of the level comparator 8 is supplied to a counting circuit 110 via a waveform shaping circuit 9 such as a Schmitt circuit. This counting circuit 1
0 drives a counting output indicating which recording band of the record 3 the record needle 14 attached to the cartridge 15 is located by counting the output from the waveform shaping circuit 9. circuit 11
supply to. This drive circuit 11 supplies an output corresponding to each recording band to the sweep device 13 of the tone arm 16. A command circuit 12 for commanding a desired piece of music is connected to the sweeping device 13. The automatic music selection detection device 20 configured as described above includes the sweep device 1
3 is controlled by a command circuit 12, and the record stylus 14 is positioned in the unrecorded zone immediately before the recording zone in which the desired song is recorded, so as to locate the beginning of the song.

However, in the conventional automatic music selection detection device 20, if the lighting around the record player is too bright and strong light enters the photoelectric conversion element 4, or if a record with a high reflectance such as a color record is used, , the DC component of the output of the photoelectric conversion element 4 increases and the output of the preamplifier 5 becomes saturated, resulting in malfunction.

Therefore, if the gain of the preamplifier 5 is lowered so that the output of the preamplifier 5 does not become saturated, the output of the differential amplifier 5 becomes smaller and the level comparator 8 The problem arises that the level is not reached. Of course, the level comparator output cannot be obtained unless the comparator level is reached.

The present invention has been developed in view of the above-mentioned circumstances, and uses a simple configuration to reliably distinguish output between recorded and non-recorded bands of a record without being affected by strong scattered light as a disturbance. An object of the present invention is to provide a detection device for automatic music selection that can obtain the following.

Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment.

In FIG. 2 showing the basic configuration of the automatic music selection detection device according to the present invention, the automatic music selection detection device 3
Reference numeral 0 denotes a photoelectric conversion element 23 that receives light emitted from the light source 21 onto the record 22 and reflected, and a differential amplification element 23 whose output from the photoelectric conversion element 23 is supplied to one input terminal 24a. 24, and an integrating circuit 25 that negatively feeds back the output of the differential amplifier 24 to the other input terminal 24b of the differential amplifier 24. configured to obtain a signal. Note that in this automatic music selection detection device 30, similarly to the above-described conventional automatic music selection detection device 20, the light from the light source 21 is irradiated onto the record 2 through the reflecting mirror 26, and the record needle 27 traces the light from the light source 21. The photoelectric conversion element 23 converts the light reflected near the sound groove of the record 22
It is converted into an electrical signal by Also, the tone arm 29 is equipped with the cartridge 28 provided with the record stylus 27. The feeding operation is performed by a sweeping device (not shown).

In the automatic music selection detection device 30 having the above-mentioned principle configuration, the differential amplifier 24 whose differential output is negatively fed back via the integrating circuit 25 functions as a type of level comparator. Since the comparator level of the differential amplifier 24 fluctuates depending on the output of the integrating circuit 25, the differential amplifier 24 performs a level comparator operation that extracts only the peak value of the conversion output from the photoelectric conversion element 23. It is possible to output a detection signal that can clearly distinguish between a recorded band and a non-recorded band on the record disc 22.

The specific circuit configuration of the essential parts of the automatic music selection detection device 30 according to the present invention, which has the above-mentioned principle configuration, will be explained using the embodiments shown in FIGS. 3 to 5. Note that in each embodiment, common components are indicated by common symbols.

That is, in each embodiment, a phototransistor 31 is used as the photoelectric conversion element 23. This phototransistor 31 has its collector connected to a positive power supply terminal 32 and its emitter grounded via a resistor 33. Further, as the differential amplifier 24, an operational amplifier 41 is used. And Figure 3,
In the embodiment shown in FIGS. 4 and 5, the emitter of the phototransistor 31 and the operational amplifier 41 are
The positive input terminal 41a of the operational amplifier 41 is connected, and the output terminal 41c of the operational amplifier 41 is connected to the negative input terminal 41b of the operational amplifier 41 via the integrating circuit 25.

In the embodiment shown in FIG. 3, the charging resistor 5
1 and a capacitor 52 are connected in series.
An RC integration circuit is used as the integration circuit 25. In the integrating circuit 25 in this embodiment, the charging resistor 51 is connected to the cathode of a diode 53 for backflow prevention whose anode is connected to the output terminal 41c of the operational amplifier 41. A connection point with the capacitor 52 is grounded via dividing resistors 54 and 55. The connection point between the dividing resistors 54 and 55 is connected to the negative input terminal 41b of the operational amplifier 41. In the integrating circuit 25 having such a configuration, the diode 53 prevents the discharge current from the capacitor 52 from flowing through the charging resistor 51, so the charging time constant and the discharging time constant can be set independently. can.

Furthermore, in the embodiment shown in FIG.
The output terminal 41c of No. 1 acts as a backflow prevention means.
It is connected to the charging resistor 51 of the RC integration circuit via an emitter follower circuit composed of an NPN transistor 61. That is, the base of the NPN transistor 61 is connected to the connection point between the resistors 62 and 63 connected in series between the output terminal 41c and the ground, and the emitter of the NPN transistor 61 is connected to the charging resistor 51. It is grounded via an emitter resistor 64. The integrated output obtained at the connection point between the charging resistor 51 and the capacitor 52 is supplied to the negative input terminal 41b of the operational amplifier 41 via dividing resistors 54 and 55.

Furthermore, in the embodiment shown in FIG.
The integral output of the integrating circuit 25 in the embodiment shown in the figure is supplied to the negative input terminal 41b of the operational amplifier 41 through a non-inverting amplifier circuit configured with a second operational amplifier 71. I'm starting to do that. That is, the second operational amplifier 71 includes the feedback resistor 72, the feedback resistor 73, and the input resistor 74 connected in series between the negative input terminal 41b of the operational amplifier 41 and the ground. The output terminal and the negative input terminal are connected via 73, forming a non-inverting amplifier circuit. The feedback resistor 73 is used to set the gain of the non-inverting amplifier circuit by using a variable resistor whose resistance value can be freely adjusted.

In the automatic music selection detection device 30 according to the present invention shown in each embodiment as described above, the tone arm 29
When swept in the radial direction of the record 22, one input terminal of the operational amplifier 41 constituting the differential amplifier 24 receives a signal from the phototransistor 31 as the photoelectric conversion element 23 as shown in FIG. A converted output with a waveform as shown in is supplied. That is, the reflectance of the record 22 is small in areas with sound grooves because the sound grooves form a diffusely reflecting surface, and in areas without sound grooves, the reflectance is high because of the gloss. As shown in FIG. 6A, m, n, corresponding to the sound groove of the record 22,
The photoelectric conversion element 23 outputs a conversion output with a low output level at o, p, etc., and a high output level at e, f, g, etc. corresponding to a location without a sound groove. Furthermore, the output of the operational amplifier 41 is supplied to the other terminal of the operational amplifier 41 constituting the differential amplifier 24 via a backflow prevention element such as the diode 53 or the NPN transistor 61. The integrating circuit 25 integrates the output of the operational amplifier 41 and supplies an integrated output with gentle undulations as shown in FIG. 6B.

The conversion output by the photoelectric conversion element 23 and the integrated output by the integration circuit 25 differ depending on the lighting conditions around the record player. For example, when strong reflected light enters the photoelectric conversion element 23,
The output level increases relatively as shown by broken lines in FIGS. 6A and 6B. However, the differential amplifier 2
The output of 4 is always unchanged as shown in FIG. 6C, and has signal parts m, n, o, p and non-signal parts e,
The waveform is such that f, g, and h can be accurately distinguished. That is, when the differential amplifier 24 integrates its output, it operates as a floating comparator that uses the integrated output from the integrating circuit 25 as the comparator level, and as a result, it functions as an unsaturated amplifier, and the input signal The level comparator operates regardless of the SN ratio.

The sensitivity of the differential amplifier 24, which operates as a floating level comparator, depends on the integrated output of the integrating circuit 25, which is determined by the charging time constant and discharging time constant of the integrating capacitor 52 of the integrating circuit 25. becomes. That is, in this automatic music selection detection device 30, by changing the value of the charging resistor 51, the charging time constant of the integrating capacitor 52 is changed, and the rise characteristic of the integral output shown in FIG. 6B is obtained. can be changed, and the comparison sensitivity of the floating comparator to the no-signal portions e, f, g, and h by the differential amplifier 24 can be variably set. In addition, each of the above dividing resistors 5
By changing the values of 4 and 55, the discharge time constant of the integrating capacitor 52 can be changed, and the falling characteristic of the integral output shown in FIG. The comparison sensitivity of the floating comparator to the signal portions m, n, o, and p by the width filter 24 can be variably set. In this automatic music selection detection device 30, the output terminal 41c of the operational amplifier 41 is connected to the integrating capacitor 52 via the diode 53 and the NPN transistor 61 which serve as the backflow prevention means. The discharge current from 25 does not flow through the charging resistor 51. Therefore, the charging time constant of the integrating capacitor 52 is determined by the values of the dividing resistors 54 and 55, and is not affected by changing the value of the charging resistor 51. Therefore, in this automatic music selection detection device 30, by independently setting the discharging time constant and discharge time constant of the integrating capacitor 52, it is possible to easily set the integrating circuit 25 to a desired integration characteristic. The above differential amplifier 24
The above no-signal part e of the floating comparator by
Comparative sensitivity for f, g, h and the signal portion m,
It is possible to easily optimize the comparative sensitivities for n, o, and p by setting them independently, and as a result, the recording band of the record disc 22 can be adjusted without being affected by strong scattered light as a disturbance. It is possible to accurately identify the recording band at all times.

As described above, in the detection device for automatic music selection according to the present invention, there is provided a photoelectric conversion element that receives light irradiated onto a record from a light source and reflected, and an output from the photoelectric conversion element that is connected to a first input terminal. a differential amplifier supplied to the differential amplifier; an integrating circuit that negatively feeds back the output of the differential amplifier to a second input terminal of the differential amplifier; and the differential amplifier and integrating circuit. and a backflow prevention means provided between the differential amplifier and the charging current to prevent reverse flow of the charging current supplied from the differential amplifier to the integrating circuit, and configured to obtain a detection output signal via the differential amplifier. Particularly, since the output of the differential amplifier is supplied to the integration circuit through the backflow prevention means, the charging time constant and the discharging time constant can be set independently to obtain desired integration characteristics. The above-mentioned differential amplifier, which can be easily set and has the above-mentioned integrating circuit in a negative feedback loop, performs amplifying operation in an unsaturated manner, and can be used as a floating level comparator with the integrated output from the above-mentioned integrating circuit as the comparator level. As a result, only the peak value of the output of the photoelectric conversion element can be reliably extracted, and the recording band and non-recording band of the record can be accurately identified at all times.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional automatic music selection detection device. FIG. 2 is a block diagram showing the basic structure of the automatic music selection detection device according to the present invention. FIG. 3, FIG. 4, and FIG. 5 are circuit diagrams of respective embodiments showing specific configurations of essential parts of the automatic music selection detection device according to the present invention. Figure 6 shows
FIG. 3 is a waveform diagram showing each output waveform for explaining the operation of the automatic music selection detection device according to the present invention. 21...Light source, 22...Record, 23...
Photoelectric conversion element, 24...Differential amplifier, 25...
Integral circuit.

Claims (1)

[Claims] 1 a photoelectric conversion element that receives light irradiated onto a record from a light source and reflected; a differential amplifier whose output from the photoelectric conversion element is supplied to a first input terminal; an integrating circuit that negatively feeds back the output of the amplifier to a second input terminal of the differential amplifier;
a backflow prevention means provided between the differential amplifier and the integrating circuit to prevent backflow of the charging current supplied from the differential amplifier to the integrating circuit; A detection device for automatic music selection configured to obtain a detection output signal.