JPS6215939B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a record size detection device for detecting the size of a record placed on a turntable of a record player. FIGS. 1 and 2 are structural diagrams showing the path of light to a light receiving element for optically detecting the record size. In FIGS. 1 and 2, 101 is a turntable, 102 is a rubber sheet, and 103 is the outer circumference of each record size. 104 is a light receiving hole for detecting the record size;
5 is a light guide tube for guiding light, and 106 is a light receiving element for photoelectric conversion. There are two sets of three light receiving holes 104 corresponding to the record sizes of 30 cm, 25 cm, and 17 cm, and the outer circumference 103 of the record sizes of 30 cm and 25 cm.
Between a and 103-b, there is a light receiving hole 104-a1,
104-a2 has a light receiving hole 10 between the outer circumferences 103-b and 103-c of the record size of 25 cm and 17 cm.
4-b1, 104-b2 is record size 17cm
A light receiving hole 104-c is provided on the inner circumference side of the outer circumference 103-c.
1,104-c2 is provided. Moreover, the light receiving holes 104-a, 104-b, and 104-c are installed on different radial lines, and the light receiving holes 104-a1 and 104-a
2,104-b1 and 104-b2 and 104-
c1 and 104-c2 are each installed on the same diameter line. Each light receiving hole is provided with a light guide tube (for example, made of glass fiber, prism, epoxy plate, etc.) 105 that guides the light incident on the light receiving hole toward the outer circumference of the turntable. . If there is no record on the turntable,
Each light-receiving hole and light guide tube guide indoor light (in case the indoor light is weak, an auxiliary light source such as a lamp may be used) toward the outer circumference of the turntable. These lights irradiate the light receiving element 106 when the optical axis coincides with the light receiving element 106 due to the rotation of the turntable, and the light receiving element 106 converts this light into an electrical signal. This light receiving element 1
The irradiation to the light receiving element 106 is chronological.
The electrical signal output is as shown in 201 in FIG. Next, when a 17 cm record is placed on the turntable, the light receiving holes 104-c1 and 104-c2 are blocked by the record, and the path of light from the room light or auxiliary light source to the light pipe 105 is blocked. . Therefore, the output electrical signal of the light receiving element 106 becomes as shown in 202 in FIG. Similarly, when a 25 cm record is placed on the turntable, the output signal of the light receiving element 106 is as shown at 203 in FIG. 3. Furthermore, when a 30 cm record is placed on the turntable, all of the light receiving holes 104 are covered by the record, so no light is irradiated to the light receiving element 106, and the output electrical signal of the light receiving element 106 is The result will be as shown in Figure 3 204. It is assumed that the light receiving element 106 is isolated so that only the light that has passed through the light guide tube 105 is irradiated onto the light receiving element 106, and there is no irradiation from other paths. Here, assuming that the time required for one rotation of the turntable is 2t ₀ , the output electric signal of the light receiving element 106 has a time relationship as shown in FIG. In other words, the light receiving holes 104-a1, 104-a2, 104-b1
and 104-b2 and 104-c1 and 104-c
2 are installed exactly on the same diameter line, and there is no change in the rotational speed such as wow or flutter in the rotation of the turntable, a1 to a in Fig. 3.
2, the repetition time of the light reception pulses b1 to b2 and c1 to c2 is _t0 . Therefore, by counting the received light pulses (rising edges or falling edges of the received light pulses) during the t ₀ period, the record size on the turntable can be detected. Table 1 shows the relationship between record size and received light pulse.
Shown below.

[Table] Next, a conventional detection circuit that determines the record size from the electrical signal of the obtained pulse train will be described. Figure 4 is an example. In Figure 4,
301 is a light receiving element corresponding to 106 in FIG.
02 is a waveform shaping circuit, 303 is a counter that counts the received light pulses, 304 is a latch circuit that temporarily holds the count at the end of counting the received light pulses, and 305 is an output terminal for size detection. 30
9 is a rotational speed signal of the turntable drive motor; 308 is a switch that becomes conductive when the turntable reaches a steady state circuit and enables record size detection; 307 and 306 are counters that set the counting period of light reception pulses; This is a count comparison circuit. The output of the comparison circuit 306 is connected to the latch timing input terminal 304-c of the latch circuit 304 and the reset terminal 30 of the counters 303 and 307.
3-R and 307-R. Next, the operation of this circuit will be explained. When the turntable reaches steady rotation, the switch 308 is turned on and the record size detection operation begins. The counter 307 counts the rising or falling edges of the rotational speed signal 309 for driving the motor of the turntable, and this count value is sent to the comparison circuit 306.
is compared with the set value. Since two sets of light receiving holes are provided as shown in FIG. 1, the setting value of this comparison circuit 306 is set to a value corresponding to the time t ₀ required for half a rotation of the turntable. counter 3
When the count value of 07 exceeds the set value of the comparison circuit 306, the output of the comparison circuit 306 is inverted, and this signal is sent to the reset terminal 307- of the counter 307.
Since the voltage is applied to R, the count value of the counter 307 is reset to zero. Therefore, the output of the comparison circuit 306 is further inverted and returns to the original state. These situations are shown in waveforms 1, 2, and 3 in FIG. The repetition time of the pulse of output 3 of the comparator circuit 306 in FIG. 5 corresponds to the time t ₀ required for the turntable to rotate half a revolution. The counter 303 counts the light reception pulse (rising or falling edge of the light reception pulse) during this period _t0 , and the count value is transferred to the latch circuit 304 and held by the pulse of output 3. Thereafter, the count value of the counter 303 is reset and the received light pulses are counted again. Here, the latch circuit 304
Assuming that the outputs of are binary parallel signals n ₀ and n ₁ , the relationship between the record size, the number of received light pulses, and n ₀ and n ₁ is as shown in Table 1. Next, the problems of the conventional circuit shown in FIG. 4 will be described. Here, suppose that a 17 cm record is placed on the turntable, and the received light pulses b1, a1, b shown in the received light pulse signal 202 in FIG.
If the rising edges of 2 and a2 are given the symbols A, B, C, and 2 as shown in FIG. If the repetition time of the received light pulse set is equal to the count time t ₀ of the received light pulse, then
In the case of 4, if the rising edge and b are 6, b and c are counted, each count value is 2, and from Table 1 it is determined that it is a 17 cm record. However, as shown in FIG _.
If it is shorter, the rising edges of the received light pulse are counted, and the count value is 3.
According to Table 1, it is incorrectly determined that there is no record. Conversely, if the repetition time of the light-receiving pulse set is longer than the count time _t0 of the light-receiving pulse as shown in FIG.
The record is incorrectly determined. The above is about a 17cm record, but in the same way when there is no record or when a 25cm record is placed on the turntable, the standard count value is 3 pieces and 1 piece,
Each of these results in an erroneous count of ±1, resulting in an erroneous determination of the record size. Count time of received light pulse
The first reason for the difference in repetition time between t ₀ and the received pulse set is uneven rotation of the turntable.
The repetition time of the light receiving pulse set fluctuates due to so-called wow and flutter, and secondly, the light receiving hole set 10
4-a1, b1, c1 and 104-a2, b2, c
Second, there is an installation error, and third, there is an error in the optical axis angle of the light pipe that guides light from the light receiving hole to the light receiving element. The cause of these record size false positives is
This is unavoidable when considering mass production. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a record size detection device that does not cause erroneous determination of record size. Conventional record size detection devices measure the counting period t ₀ of the received light pulse and the number of received light pulses during the time t ₀ .
Because the ON/OFF time pattern is random,
As mentioned above, erroneous determination of the record size occurred due to uneven rotation of the turntable, mounting accuracy of the light receiving hole, etc. Therefore, the present invention sets a counting period of the light receiving pulse from the time when the light receiving pulse is detected, that is, using the light receiving pulse as a trigger, and sets a counting period of the light receiving pulse that is sufficient to cover up to three light receiving pulses, and By making the repetition time t of the light receiving pulse set shorter than ₀ , the counting period and the temporal pattern of ON and OFF of the light receiving pulses are kept constant, and the effects of uneven rotation of the turntable, mounting accuracy of the light receiving hole, etc. This is to prevent misjudgment of record size. DESCRIPTION OF THE PREFERRED EMBODIMENTS The record size detection device according to the present invention will be described below with reference to embodiments shown in the drawings. A specific example of the record size detection device of the present invention is shown in FIG. In FIG. 6, 501 is a light receiving element corresponding to the light receiving element 106 in FIG. 1, 502 is a waveform shaping circuit, 503 is a counter that counts the number of light receiving pulses, and 504 is a temporary count number at the end of counting the light receiving pulses. Latch circuit to hold, 5
05 is an output terminal for size detection. 506 is a reset priority type RS flip-flop, 507 is a two-input OR circuit, 508 is a gate circuit that conducts or cuts off the signal path, 509 is a counter that sets the count time of the light reception pulse, and 512 is the pulse and pulse of the light reception pulse signal. Counters 510 and 513 are counters 509 and 51 that measure the OFF time of
511 is a two-input OR circuit, and 514 is a rotational speed signal for driving the motor of the turntable. Next, the basic operation shown in FIG. 6 will be explained. Basically, a received light pulse signal of a light receiving element 501 is waveform-shaped by a waveform shaping circuit 502, and a counter 503 counts the received light pulses. This count value is temporarily held by the latch circuit 505, and the output terminal 505
5 and output to n ₁ and n ₂ as binary parallel signals. In addition, during the count period of the light reception pulse, the flip-flop 506 is set by the light reception pulse,
The gate circuit 508 uses the output of this flip-flop.
is made conductive, the counter 509 counts the rise or fall of the rotation speed signal for driving the turntable motor, which is a signal with a frequency corresponding to the rotation speed, and this count value corresponds to the count time of the received light pulse. It is set by comparing it with the set value of circuit 510. The output of the comparison circuit 510 mentioned above is applied to the reset terminal 509-R of the counter 509 via the OR circuit 511, so when the count value of the counter 509 or the set value of the comparison circuit 510 is exceeded, the counter 509 is reset. Generates a pulse. This pulse simultaneously changes the count value of the counter 503 to the latch circuit 504.
This becomes a latch timing signal transmitted to the output terminal 505, holds the count value at the output terminal 505, resets the counter 503, resets the flip-flop 506, and turns off the gate circuit 508. Also, a counter 512, a comparison circuit 513 and
The OR circuit 507 is a circuit for when no light reception pulse is inputted, such as when a 30cm record is placed on a turntable, and the counter 512 counts the pulses of the light reception pulse signal and the pulse OFF period, and the comparison circuit 513 By comparing the count value of the counter 512 with the set value, when no light reception pulse is input for a certain period of time or more, the output of the comparison circuit 513 resets the counter 512 and generates a pulse. The output pulse of the comparison circuit 513, like the output pulse of the comparison circuit 510 described above, serves as a latch timing signal for holding the count value of the counter 503, that is, zero at this time, in the latch circuit. FIG. 7 shows waveforms at various parts in FIG. 6. In FIG. 7, 1 is the light reception pulse signal, 2 is the output of the flip-flop 506, 3 is the count value of the counter 509, 4 is the output of the comparison circuit 510, 5 is the count value of the counter 503, and 6 is the light reception pulse of the output terminal 505. 7 is the count value of the counter 512, 8 is the output of the comparison circuit 513, and 9 is the output of the OR circuit 51. Here, as shown in 1 in Figure 7, the ON time width of the light receiving pulse of the light receiving pulse signal is ta, and the OFF time width of the light receiving pulse and the light receiving pulse in the light receiving pulse group is ta.
tb, the repetition time of the received light pulse set is t ₀ , and the seventh
As shown in Figure 3, the setting value of the comparator circuit 510 is
Tp is tp in terms of time, and if 3ta + 2ta < tp ... (1) to - (3ta + 2ta) > tp ... (2), then if the received light pulse does not correspond to the beginning of the received light pulse set in time series, the flip-flop 5
Even if the record size detection operation is started at the timing when 06 is set, the counting period tp of the received light pulses will always be completed before the beginning of the next set of received light pulses is received, as shown in equation (2). Therefore, from now on, the flip-flop 506 will always be set with the received light pulse corresponding to the head of the set of received light pulses. At this time, flip-flop 5
With the output of 06, the gate circuit becomes conductive, and a counter 509 counts the rise or fall of the rotational speed signal 514. When the count value of this counter 509 exceeds the set value Tp of the comparator circuit 510, tp in terms of time, the comparator circuit 510
The output of 10 is inverted, and this signal is sent to the OR circuit 511.
Reset terminal 509- of counter 509 via
Since the voltage is applied to R, the count value of the counter 509 is reset to zero, and the output of the comparison circuit 510 is further inverted to return to its original state. That is, as shown at 3 and 4 in FIG. 7, the output of the comparator circuit 510 generates a pulse after a time tp after receiving the light reception pulse corresponding to the head of the light reception pulse set in time series. This pulse is processed by the counter 503 as described above.
This serves as a latch timing signal for transferring the count value of 0 to the latch circuit, and also serves as a reset signal for counter 503 and flip-flop 506. The above situation is shown in 1 to 6 in FIG. Note that the dotted line in FIG. 7 shows the case where the light reception pulse signal from point A to point B in the figure is similarly received during the period from point C to point D. In addition, a counter 512, a comparison circuit 513 and an OR
As described above, the circuit 507 is a circuit for when no light reception pulse is input, such as when a 30 cm record is placed on a turntable. Here, if the set value of the comparator circuit 513 is Tβ, converted to time is tβ, and tβ>to...(3), then the dotted lines from point A to point B and from point C to CD in FIG. When a light reception pulse is input, the count value of the counter 512 is reset by the light reception pulse, so that it does not exceed the set value Tβ of the comparison circuit 513. However, when no light reception pulse is inputted, as from point B to point E in FIG. , the output of the comparison circuit 513 generates a pulse, as shown at 7 and 8 in FIG. At this time, the count value of the counter 503 is reset after the count period of the light reception pulse in the previous stage, and is zero since there is no light reception pulse thereafter. The count value zero of this counter 503 is the same as that of the previous comparison circuit 5.
13 is transferred to latch circuit 504, and counters 509, 512 and flip-flop 506 are reset. These situations are shown by solid lines from points B to F in 1 to 8 in FIG. Based on the number of light pulses received at the output terminal 505 of the latch circuit obtained as described above, the record size can be determined based on the relationship between the size and the number of light pulses shown in Table 1. As described above, the present invention uses the light reception pulse corresponding to the beginning of the light reception pulse set as a trigger, sets the light reception pulse count period tp, and uses the light reception pulse count period tp to repeat the light reception pulse set. The rotation of the turntable is made shorter than the time to, and when there is no light pulse, such as with a 30 cm record, by making sure that there is no light pulse for a time tβ, which is longer than the repetition time to of the light pulse set, the turntable can be rotated. It is possible to prevent the conventional erroneous determination of the record size due to unevenness, errors in the mounting accuracy of the light receiving holes, etc. According to the present invention, it is possible to prevent erroneous counting of the number of light-receiving pulses due to uneven rotation of the turntable, errors in mounting accuracy of the light-receiving holes, etc., that is, erroneous determination of the record size, and to reliably detect the record size. Furthermore, this can be achieved with a relatively simple circuit configuration.

[Brief explanation of the drawing]

Figures 1 and 2 are a plan view and cross-sectional view of a turntable for optically detecting the record size, Figure 3 is a waveform diagram showing the pattern of the received light pulse signal, and Figure 4 is a conventional record size diagram. A block diagram of the detection device, FIG. 5 is a waveform diagram of each part of a conventional record size detection device, FIG. 6 is a block diagram showing an embodiment of the record size detection device of the present invention, and FIG. 7 is an embodiment of the present invention. FIG. 3 is a waveform diagram of each part for explaining the operation of the FIG. 501: Light receiving element, 503: Counter, 50
4: Latch circuit.

Claims (1)

[Claims] 1. A first time comparison device is connected to the output of a first time measurement device that starts measuring time by triggering the pulse of the output signal of a record size detector that generates a number of pulses corresponding to the record size in time series. A second time comparing device is provided at the output of the second time measuring device for measuring the OFF time of the pulse of the output signal of the record size detector, and an output of a counter for counting the pulse of the output signal of the record size detector. A storage device for storing the count value of the counter is provided, and the output signals of the first and second time comparison devices are used as a timing signal for transferring the count value of the counter to the storage device and as a reset signal for the counter. A record size detection device characterized by: