JPS6316003Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a tone arm position detection device.

Conventionally, a mechanism for optically detecting the position of a tone arm consists of a light-emitting element and a light-receiving element arranged in opposing positions, and a light-shielding plate having a slit corresponding to the lowered or returned position of the tone arm. Something was hot. However, in this optical detection method, since the determination is based on the presence or absence of the output of the light receiving element, in order to know the arbitrary position of the tone arm, such as each disk size or return position, it is necessary to detect the light emission at opposite positions. The circuit becomes complicated because a plurality of sets of elements and light-receiving elements are used, and in the case of one set, processing must be performed by a circuit. Therefore, recently, a method has been proposed in which the size of the slit is changed to change the output of the light receiving element, and the position of the tone arm is detected based on the output.

However, this method has the disadvantage that it is necessary to clearly differentiate the size of the slits in order to obtain a clear difference in the output of the light-receiving elements, and that it takes time and effort to process the slits.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tone arm position detection device that eliminates the above-mentioned drawbacks.

In other words, in this invention, the sensitivity of light receiving elements such as phototransistors and photodiodes is not constant for all wavelengths, but peaks at a certain wavelength, and the relative sensitivity decreases like a so-called Gaussian curve. Even if the illuminance of the light receiving element is constant, an arbitrarily colored filter is provided on the optical path of the light receiving element, and by changing the amount of light transmitted through this filter, the output of the light receiving element is made to differ. .

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the tone arm position detection device of the present invention. In FIG. 1, 1 is a tone arm, 2 is a horizontal rotation shaft of the tone arm 1, and 3 is a rotation plate attached to the horizontal rotation shaft 2 that rotates with the horizontal rotation of the tone arm 1; 4a, 4
b and 4c are through holes provided in the rotating plate 3 with the same size, 5a and 5b are filters attached to the through holes 4a and 4b, and 6a and 6b are through holes 4a and 4 provided in the rotating plate 3, respectively. A light-emitting element and a light-receiving element are arranged opposite to 4b and 4c and form a photocoupler 6. Through holes 4a, 4b, 4 provided in the rotating plate 3 attached to the horizontal rotating shaft 2 of the tone arm 1
C corresponds to disk sizes of 30cm, 25cm, and 17cm, respectively.

Filters 5a, 5b are provided in the through holes 4a, 4b.
is attached, and no filter is provided in the through hole 4c.

The filter 5a is made of a transparent filter colored, for example, blue, and the filter 5b is made of a transparent filter colored, for example, yellow.

Therefore, in this state, when the tone arm 1 is moved from the armrest (not shown) onto the record, outputs corresponding to the through holes 4a, 4b, and 4c are obtained (see FIG. 2). That is, since the blue filter 5a is provided in the through hole 4a, the amount of light transmitted is small and the output of the light receiving element 6b is small.
Since the yellow filter 5b is provided in the section b, the amount of light transmitted is medium and the output of the light receiving element 6b is medium, and the light transmitting section 4c is not provided with a filter, so the light is transmitted as is. This increases the output of the light receiving element 6b.

This output is sent to the level comparator 7 as shown in Figure 3.
is applied to output terminals A, B, and level comparator 7.
By outputting from either terminal of C, the position of the tone arm can be easily detected.

As described above, the present invention includes a rotating plate that rotates as the tone arm rotates, a plurality of through holes of the same shape provided in the rotating plate corresponding to different disk sizes, and a rotating plate that rotates as the tone arm rotates. It consists of a light-emitting element and a light-receiving element arranged in positions facing the through-hole of the plate and forming a photocoupler, and a filter provided in the through-hole to make the output of the photocoupler different, and the output of the photocoupler can be made different by the filter. Since it is configured to detect different positions of the tone arm, there is no need to change the size of the through hole or provide multiple sets of light emitting elements and light receiving elements as in the conventional case. The position of the tone arm can be reliably detected by clearly giving a difference in the outputs of the light receiving elements of the photocoupler set.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the tone arm position detection device of the present invention, Fig. 2 is an output diagram of the photocoupler when passing through a rotary plate having a through hole with a filter attached, which is the gist of the present invention; FIG. 3 is a block diagram showing an example of detecting the position of a tone arm using the output of a photocoupler. 3...Rotating plate, 4a, 4b, 4c...Through hole, 5
a, 5b...Filter, 6a...Light emitting element, 6
b... Light receiving element.

Claims (1)

[Scope of utility model registration request] a rotating plate that rotates as the tone arm rotates;
a plurality of identically shaped through holes provided in the rotary plate corresponding to different disk sizes; a light emitting element and a light receiving element disposed at positions opposite to the through holes of the rotary plate and forming a photocoupler; A tone arm position detecting device comprising a filter provided in the through hole to vary the output of the photo coupler, and detecting different positions of the tone arm by varying the output of the photo coupler.