JPS61265702A - Detector for lead-out in record player - Google Patents

Abstract

PURPOSE:To output a lead-out signal by generating a sampling pulse at an interval of 140 deg.-160 deg. of a turning angle of a turntable so as to detect the lead- out accurately without malfunction even with a warp of a record disc. CONSTITUTION:A sampling pulse generator 4 is synchronized with the turning of the turntable and outputs a sampling pulse at a turning angle of 140 deg.-160 deg. each. A computing element 5 reads a speed signal outputted from a speed sensor 1 synchronously with the sampling pulse and calculate a mean speed by using the speed signal sampling by the n-th sampling pulse and the speed signal sampled by the (n+1)-th sampling pulse. The mean speed signal from the arithmetic means is compared with a predetermined reference signal to extract a lead-out signal by a comparison means 2, allowing to detect the lead-out accurately with less effect of warp of a record disc and to detect surely the lead-out even for a record disc having one circle only of the lead-out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an end detection device for automatic return of a tone arm of an automatic record player.

BACKGROUND OF THE INVENTION In recent years, so-called automatic record players that detect the end of playing a record and automatically return the tone arm have become mainstream, and there is a demand for improved accuracy of end detection devices that detect the end of playing a record.

An example of a conventional end detection device for a record player will be described below with reference to the drawings.

FIG. 3 shows a block diagram of a conventional end detection device for a record player. In FIG. 3, reference numeral 1 denotes a speed sensor, which outputs a speed signal proportional to the speed at which a pickup cartridge (both not shown) provided at the tip of the tone arm moves along the groove of the record. 2 is a comparator which compares the reference signal output by the reference signal generator 3 and the speed signal output by the speed sensor 1, and outputs a terminal signal 4 when the speed signal is higher than the reference signal.
Output.

According to the above configuration, the pickup cartridge takes advantage of the fact that the pitch of the lead-out groove provided at the end of the record is larger than the pitch of the lead-out groove provided in the middle part of the song, and the pickup cartridge Sometimes the comparator will not output a termination signal because the speed signal is smaller than the reference signal;
Conversely, when moving along the lead-out groove at the end, the speed signal becomes larger than the reference signal and the comparator outputs the end signal.

Problems to be Solved by the Invention However, with the above configuration, if the record is eccentric, the output 6 of the speed sensor becomes wavy as shown in Figure 4, and even during the performance, the P point Since the speed signal 6 becomes larger than the reference signal 8 at , the comparator outputs a termination signal.

That is, there is a problem in that the tone arm returns even during a performance because the eccentricity causes the speed signal to be erroneously output in an excessive amount.

In order to solve the above-mentioned problems, the present invention is capable of accurately detecting the end of a record without causing malfunction even if there is eccentricity in the record, and outputting an end signal. An object of the present invention is to provide an end detection device for a record player that can reliably detect the end of a record that is not provided.

Means for Solving the Problems In order to solve the above-mentioned problems, the end detection device for a record player of the present invention has a rotation angle of 1400 degrees.
A sampling pulse generating means that generates a sampling pulse every ~16 d, and a speed signal outputted from a speed sensor in synchronization with the sampling pulse outputted from the sampling pulse generating means, to obtain the average speed signal. and a comparing means for comparing the average speed signal from the calculating means with a predetermined reference signal and extracting a termination signal.

According to the present invention, with the above-described configuration, the speed signal output from the speed sensor is averaged, and the influence of eccentricity of the record is reduced, thereby making it possible to accurately detect the end of the record. Furthermore, with a sampling interval of 14d to 160°, sampling can be performed three times during one rotation of the turntable, and even for records with only one round of the lead-out groove at the end, the speed signal at the lead-out groove can be can be sampled at least twice, and the end can be detected reliably.

Embodiment Hereinafter, an end detection device for a record player according to an embodiment of the present invention will be described with reference to the drawings. Components having the same functions as those in FIG. 3 are given the same numbers and their explanations are omitted.

FIG. 1 shows a block diagram, and 4 is a sampling pulse generator. The sampling pulse generator is synchronized with the rotation of a turntable (not shown) and outputs a sampling pulse at every rotation angle of 16o0. 6 is an arithmetic unit, which is synchronized with the sampling pulse [2] reads the speed signal output from the speed sensor 1, and calculates the speed signal Mn sampled by the n-th sampling pulse Pn and the n+1-th sampling pulse pn+1.
An average speed signal vn=(man n+man n+t)/2 is calculated from the two signals sampled by speed signal man n+1.

In Figure 2, 6 is the speed signal output from the speed sensor when the record has eccentricity, 7 is the average speed signal averaged by the calculator, and 8 is the reference signal output from the reference signal generator. It shows. In the figure, section M is within the song of the record, and section B is the section of the lead-out groove at the end of the record. Also Pn+ 'n+1'''t
P@*PH+1'' is the sampling point of the sampling pulse output from the sampling pulse generator, and its period is synchronized with the rotation angle of 16 cf' of the turntable.

Average speed signal 7n+ 7n+1...
. . , respectively, then 76≧vn, vn+, old . . . (1) always holds true between them and the value Td of the reference signal 8. Also, in section B, the average speed signal 71
The value of n' 7m+1 is vm t Vm++°
°.

If so.

vd ku vm, 7m+1...
...(2) always holds true.

Now, let's say speed ratio kama. , Tn=-6n+6+8=IC5ino-
-------(3). Here, en is the original speed signal that should be obtained when the stylus tip traces the groove of the record when there is no eccentricity at all, and e is an error signal that appears due to eccentricity and changes sinusoidally.

Here, the average speed signal vn obtained when the sampling period is θ1 can be expressed as (4) (4).

In the above equation (4), the second term is an error signal, so if it is set to '0', the influence of eccentricity can be completely ignored. In this case, θ=π radian.

However, it is known that some commercially available records have only one turn of the lead-out groove at the end.

This will be referred to as a 1-turn record below, and in a 1-turn record, the sampling period θ is set to π(18
0°), in the worst case, sampling may be performed only once at the portion where the pitch of the lead-out grooves is maximum.

At this time, since vd>Vn, the comparator cannot output a termination signal.

Therefore, it is necessary to make the sampling period θ1 smaller than π, so if we set 01 = -π (1600), the formula (box is V n = - (e n-4 - e n+ , ) + K
5in(θ+-w) aos-yr, and it can be seen that the value of the second term error signal is 0.26 times that of no correction at all.

Here, θ1=danπ, but some commercially available records include (1) Maximum eccentricity of the record: 0.3ff (2)
Minimum pitch of lead-out groove 3H (3) Maximum pitch of sound groove and feed groove 1 Because there is a limit of 1 ILM, 01 must be within a range that does not malfunction in all of these cases.
All you have to do is set .

As described above, according to this embodiment, the sampling pulse generator 2 and the speed sensor are output from the sampling pulse generator 2 at every 1so' rotation angle of the turntable, and in synchronization with the sampling pulse output from the sampling pulse generator. By providing a calculation means for extracting the output speed signal and calculating the average speed signal, the end can be accurately detected even for records with eccentricity, and the lead-out groove at the end can be turned around only once. Accordingly, it is possible to obtain a record end detection device that has an excellent characteristic of being able to reliably detect the end of a record even when there is no record.

Further, in the above embodiment, the sampling pulse generator 4, the comparator circuit 2, and the arithmetic circuit 6 are provided separately, but it is also possible to replace all of these with a microprocessor.

Effects of the Invention As described above, the present invention includes a speed sensor that extracts the moving speed of a tone arm as a speed signal, a sampling pulse generating means that generates a sampling pulse every 1600 degrees of rotation angle of a turntable on which a record is mounted, and the sampling pulse a calculation means for extracting the speed signal outputted from the generation means and obtaining an average speed signal; and a calculation means for comparing the average speed signal from the calculation means with a predetermined reference signal to obtain a terminal signal. By providing a comparison means for taking out the record, it is possible to reduce the influence of eccentricity of the record, accurately detect the end, and reliably detect the end even for records where the end lead-out groove only goes around once. An excellent record player end detection device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the terminal end detection device for a record player according to the present invention, FIG. 2 is a waveform diagram showing signals in the device shown in FIG. 1, and FIG. 3 is a terminal end of a conventional record player. A block diagram showing an example of a detection device, and FIG. 4 is a waveform diagram showing signals in the device shown in FIG. 3. 1...Speed sensor, 2...Comparator, 3
...Reference signal generator, 4...Sampling pulse generator. 6... Arithmetic unit, 6... Speed signal, 7.
...Average speed signal, 8...Reference signal. □ Name of agent: Patent attorney Toshio Nakao and 1 other person
Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] A speed sensor that extracts the moving speed of the tone arm as a speed signal when the pickup cartridge installed at the tip of the tone arm moves along the groove of the record, and a 140° rotation angle of the turntable on which the record is mounted.
A sampling pulse generating means that generates sampling pulses every 160° to 160°, and a speed signal outputted from the speed sensor in synchronization with the sampling pulse outputted from the sampling pulse generating means, and an average speed signal thereof. and a comparison means for comparing the average speed signal from the calculation means with a predetermined reference signal to extract a termination signal. Detection device.