JPS6330682B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a track interval detection device for a record player, and its purpose is to compensate for differences in the reflectance of records with a simple configuration, and to always ensure automatic operation. The purpose is to enable song interval detection.

Generally, when a record player plays an LP record on which a plurality of songs have been recorded, for example, a song interval detection device is used to automatically play any song on the record. The above-mentioned track interval detection device is provided with an optical sensor including a light emitter and a light receiver at the tip of a tone arm or a sensor arm, and the arm moves the optical sensor in the radial direction on the record. By using the difference between the reflected output level at the sound groove of the record and the reflected output level between songs between the sound grooves, is optically detected, and
When detecting a track interval on a record using the optical track interval detection device as described above, the reflected output level at the sound groove of the record at the output of the optical sensor that receives the reflected light from the record. In order to take advantage of the fact that the reflected output level between songs on a record is higher than that of the record, the threshold level is set to a value that is higher than the reflected output level at the above-mentioned sound groove and lower than the reflected output level between the above-mentioned songs. However, when there is an output equal to or higher than this threshold level, it is customary to output an inter-music signal pulse to perform inter-musical detection.

In other words, in a song interval detection device using a reflective optical sensor, the light emitted from the emitter onto the record surface and reflected to the receiver is detected between the song gaps between the tone grooves of the record. from the part,
Since most of the reflected light from the sound groove is scattered, the amount of reflected light changes in proportion to the size of the flat area in the effective area (field of view) on the record for the light receiving section, and the The track pitch in the inter-track feed groove portion is sufficiently wider than the track pitch in the tone groove portion, and the smaller the track pitch on the record, the less the amount of reflected light. Therefore, when an optical sensor is scanned in the radial direction on a record, it is possible to obtain a signal according to the surface condition of the record, and the track pitch changes suddenly (becomes coarse) in the track feed groove area and becomes flat. Since the area is increased, a large output signal can be obtained. Then, by comparing the output signal from the optical sensor with a predetermined threshold level, it is determined that a large output signal that changes rapidly is the part of the inter-song feed groove, and inter-song detection is performed. be able to.

However, in the track-to-track detection device using the reflective optical sensor described above, the reflected output level from the optical sensor decreases as the width of the track-to-track feed groove becomes narrower. In some cases, the reflected output level at the inter-track feed groove may be lower than the specified threshold level, and in such cases, it may be determined that the inter-track feed groove is actually an inter-track feed groove. There was a problem in that it was not possible to judge the difference between songs, resulting in errors in detecting the intervals between songs. On the other hand, if the threshold level is set lower to prevent such errors in track interval detection, the track pitch will suddenly become coarser to record a large amplitude in the sound groove. When scanning a recorded record, the reflected output level becomes large in the part of the sound groove where the track pitch changes greatly, and the track pitch is determined to be an inter-track feed groove even though it is not supposed to be an inter-track feed groove. There was a problem in that errors occurred when detecting between songs.

The present invention eliminates such conventional drawbacks, and the present invention will be described below with reference to drawings of embodiments.

1 and 2 show an example of the structure of the song interval detection device of the present invention, in which 1 is a light emitting device such as a lamp or a light emitting diode, and 2 is optically coupled to the light emitting device 1. The light emitter 1 and the light receiver 2 are provided at the tip of a tone arm or other sensor arm (not shown), and are connected to an optical sensor 3.
The light emitting device 1 illuminates the record when it is moved in the radial direction on the record.
The angle is set so that the reflected light from the light enters the light receiver 2. 4 is inverter 5, transistor
This is a drive circuit for the light emitter 1, which is composed of TR ₁ , TR ₂ , resistors R ₁ , R ₂ , R ₃ , etc., and the light emitter 1 is connected between the collector of the transistor TR ₂ and the resistor R ₃ . has been done. 6 is a transistor TR ₃ ,
This is a pulse generation circuit composed of TR ₄ , resistors R ₄ to R ₇ , capacitors C ₁ and C _{2 ,} etc., and the pulse output from the collector of the transistor TR ₄ is applied to the inverter 5 of the drive circuit 4. . Reference numeral 7 denotes an amplifier circuit composed of an operational amplifier A ₁ , a variable resistor VR ₁ for adjusting the amount of feedback, etc., to which the output from the photodetector 2 is input. Reference numeral 8 denotes a bandpass filter composed of an operational amplifier A ₂ , a capacitor C ₃ , resistors R ₈ to R ₁₀ , a coupling capacitor C ₃ and the like, to which the output from the amplifier circuit 7 is applied. 9 is a diode D ₁ , an analog switch 10,
11. A peak hold circuit composed of an operational amplifier _A5 , resistors _R11 to _R13 , a capacitor _C5 , etc., to which the output of the amplifier circuit 7 that has passed through the bandpass filter 8 is added. 12 is an inverter 13, a one-shot multivibrator 14,
15, a phase shifter composed of resistors R ₁₄ , R ₁₅ , capacitors C ₆ , C ₇ , etc., which is connected to the pulse generating circuit 6
The pulse output from is added to adjust the phase appropriately, and the output is applied to the peak hold circuit 9 as a sampling pulse. 16 is a signal processing circuit that generates an inter-song feed groove pulse when the reflected output at the inter-song feed groove portion is large with respect to the threshold voltage, and automatically follows the threshold voltage according to the inter-song feed groove pulse. The output from the peak hold circuit 9 is added thereto. Reference numeral 17 denotes an output circuit consisting of a one-shot multivibrator 20, resistors R ₂₁ , R ₂₂ , capacitor C ₁₀ , etc., to which the output from the signal processing circuit 16 is added and an inter-song signal is output. Here, as shown in FIG. 2, the signal processing circuit 16 includes a differentiating circuit 21 consisting of a resistor _R16 and a capacitor _C8 , operational amplifiers _A4 , _A5 , an electronic switch 22, a hold capacitor _C9 , and a dividing resistor R. ₁₇ , _R18 , a comparator 23, etc.

In the track interval detection device having such a configuration, the generator 1 is pulse-driven by the pulse output from the pulse generation circuit 6, the light receiver 2 receives the reflected light from the record surface, and the reflected output is sent to the amplifier circuit. Add to 7. The reflected output is amplified by the amplification circuit 7 and then passed through a bandpass filter 8 and applied to a peak hold circuit 9 to hold the peak value. When the light emitter 1 constituting the optical sensor 3 is driven in pulses in this manner, the current applied to the light emitter 1 can be set to be large, so that the luminance of light emission can be increased and the sensitivity of the light receiver 2 can be increased. By peak-holding the reflected output from the light receiver 2 using the peak-hold circuit 9, signal detection can be made more reliable. Further, by using the bandpass filter 8, the influence of ambient light can be reduced, and the detection between songs can be improved. Next, the output of the peak hold circuit 9 is applied to the signal processing circuit 16. Here, the output from the peak hold circuit 9 as shown in FIG _. The signal is amplified and converted into the signal shown in FIG. 3b. One of the outputs of the above operational amplifier _A4 is connected to the comparator 23.
one directly, and the other to the electronic switch 22. This electronic switch 22 is normally turned off and is controlled by the output of a comparator 23. Therefore, the electronic switch 22, which is normally turned off, is turned on when there is an output from the comparator 23, and instantaneously charges the output of the operational amplifier _A4 to the capacitor _C9 in the next stage, and uses the charge voltage of the capacitor _C9 to power the operational amplifier _A5. The voltage shown in FIG. 3c, divided by the resistors R ₁₇ and R ₁₈ , is applied to the comparator 22 as a threshold voltage. In other words, the signal processing circuit 16 holds the peak value of the pulse height from the operational amplifier _A4 , and supplies a voltage obtained by multiplying this peak value by a certain ratio to the comparator 23 as a threshold voltage. operational amplifier
A above operational amplifier by comparing the pulse signal from ₄
When the pulse signal from A ₄ is large, it is determined that it is the inter-track feed groove portion, and the determination pulse shown in FIG. 3d is outputted to the output terminal 19 of the comparator 23. At the same time, the charge voltage of capacitor _C9 is reset, and the new pulse height peak value is held again. Therefore, when the optical sensor 3 is moved on the record by the arm, whether it is a record having a wide track-to-track feed groove or a record having a narrow track-to-track feed groove, the position shown in FIG. As shown in a and b, the threshold voltage changes automatically based on the judgment pulse corresponding to the inter-track feed groove portion, and does not become lower than the pulse at the part of the sound groove where the track pitch is large. As a result, a correct positive inter-song detection pulse is always output to the comparator 23. The one-shot multivibrator 20 provided in the output circuit 17 is effective in preventing chattering.

FIG. 5 shows another embodiment of the signal processing circuit. The difference between FIG. 5 and FIG. 2 is that the peak hold/reset circuit 51 is replaced by an integrating circuit 5 consisting of a resistor R ₅₁ and a capacitor C ₅₁ having a large time constant.
2 and a diode _D51 , and is configured to be rapidly discharged in the negative direction and hold the peak value. The output of the peak hold/reset circuit 51 is applied to one side of the comparator 23, a predetermined voltage is held by a diode _D52 , and a bias is applied to the other side, and the output of the operational amplifier _A4 is applied to the other side through a resistor _R52 . I'm trying to add it.
Note that the resistor _R53 is a feedback resistor. In a signal processing circuit having such a configuration, when the output from the peak hold circuit 9 shown in _FIG . The signal is then converted into the signal shown in FIG. 6b. One of the outputs of the operational amplifier _A4 is applied to the comparator 23 through the resistor _R52 , and the other is applied to the peak hold/reset circuit 5.
Added to 1. When there is a negative pulse at the input of this peak hold/reset circuit 51, the diode _D51 is turned on and the charge of the capacitor _C51 is rapidly discharged, the potential of _C51 is also rapidly reduced, and the magnitude of the negative pulse is memorized. be done. As a result, the signal shown in FIG. 6c is applied to the output of the peak hold/reset circuit 51 as a threshold voltage. At this time, the other input of the comparator 23 is held at a predetermined voltage by the diode _D52 , and the threshold voltage from the peak hold/reset circuit 51 does not fall below the voltage set by the diode _D52 . There isn't. and,
When the comparator 23 compares the threshold voltage from the peak hold/reset circuit 51 with the signal from the operational amplifier _A4 , it outputs the determination pulse shown in FIG. 6d. The peak hold/reset circuit 51 is reset when a negative pulse is received, and performs the operation of recharging the capacitor _C51 . In other words, the signal processing circuit holds the peak value of the pulse height from the operational amplifier _A4 , applies a voltage obtained by multiplying this peak value by a certain ratio to the comparator 23 as a threshold voltage, and outputs the voltage between this threshold voltage and the operational amplifier A4. Compare the pulse signals from the operational amplifier _A4 , and when the pulse signal from the operational amplifier _A4 is large, determine that it is the inter-track feed groove portion, and output a determination pulse;
At the same time, the charge voltage of capacitor _C51 is reset to maintain the new pulse height peak value. Therefore, even on a record disc in which a large amplitude is recorded in the sound groove, it is possible to detect the interval between songs without error.

As described above, according to the present invention, one of the reflected outputs from the optical sensor applied to the comparator is automatically changed according to the inter-track feed groove pulse, and is used as the threshold voltage. This method has the advantage that it is possible to reliably detect a track interval even if the record has a reflectance, and that it can also reliably detect a track interval even if the reflectance within one record is different.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the track interval detection device for a record player of the present invention, Fig. 2 is a circuit connection diagram of the main parts of the device, and Figs. 3 and 4 are explanations of the operation of the device. 5 is a circuit diagram of the main part showing another embodiment of the track interval detection device for a record player according to the present invention, and FIG. 6 is an explanatory diagram of its operation. 1... Emitter, 2... Light receiver, 3... Optical sensor, 4... Drive circuit, 6... Pulse generating circuit, 7
...Amplification circuit, 8...Band pass filter, 9...
...Peak hold circuit, 12...Phase shifter, 16...
...Signal processing circuit, 17...Output circuit, 21...Differentiating circuit, 22...Electronic switch, 23...Comparator, 51...Peak hold/reset circuit.

Claims (1)

[Scope of Claims] 1. A light emitting device that irradiates a record disc and a light receiver that receives reflected light from the light emitter that irradiates the record disc, and is moved in the radial direction of the record disc. an optical sensor, a signal processing means for setting a threshold voltage corresponding to the track-to-track feed groove pulse output in accordance with the movement of the optical sensor, and a signal processing means that passes the reflected output from the optical sensor and the signal processing means. and a comparator to which the reflected output from the optical sensor is added as an input, and the threshold voltage to the comparator is equal to the peak value of the inter-track feed groove pulse outputted every time the optical sensor crosses the inter-track feed groove. A track interval detection device for a record player, characterized in that the track interval detection device for a record player is configured to automatically follow and change settings according to the music. 2. The signal processing means includes a switching means that is controlled by switching based on a judgment pulse from a comparator, a voltage holding means that holds the peak value of the inter-track feed groove pulse from the optical sensor that passes through this switch, and this voltage holding means. 2. The track interval detection device for a record player according to claim 1, further comprising voltage dividing means for applying a voltage obtained by multiplying the holding voltage by a certain ratio to the comparator as a threshold voltage. 3. The record according to claim 1, wherein the signal processing means is comprised of an integrating circuit to which the inter-track feed groove pulses from the optical sensor are applied, and diodes inserted across a resistor of this integrating circuit. Player's song interval detection device. 4. The track interval detection device for a record player according to claim 3, wherein one input of a comparator to which the output of the integrating circuit is applied as a threshold voltage is held at a predetermined voltage by a diode. 5. Track interval detection for a record player according to claim 1, 2, or 3, characterized in that the reflected output from the optical sensor is applied to a comparator and signal processing means through a differentiating circuit. Device. 6. Claim 1, characterized in that the inter-song detection pulse from the comparator is outputted through a one-shot multivibrator.
The song interval detection device for a record player according to item 2 or 3.