JPH07220326A - Light guiding device - Google Patents

Abstract

PURPOSE:To improve the transmission efficiency of a light transmission line and to ensure the stable photodetection value by providing the concave and convex and faces on a light guiding member set opposite to the photodetecting surface and the photodetector of the guiding member respectively. CONSTITUTION:A center prism 27 of a light guiding member has a concave photodetecting surface 27a. Meanwhile the side prisms 31 and 32 opposite to the phototransistors 26 and 26 of a photodetector have the convex lower end faces as the emission surfaces 31a and 32a respectively at both side parts of the light guiding member where the phototransistors 26 are attached. Thus the prism 27 and the prisms 31 and 32 of the light guiding member function as lenses so as to reduce the loss of light due to the dispersion of light in both incident and emission modes. Therefore the light transmission efficiency is improved and the stable photodetection value is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide device suitable for use in a device for detecting the beginning and end of a tape such as a video cassette, an audio cassette or a digital audio cassette.

[0002]

2. Description of the Related Art Conventionally, as a light guide device used for a tape deck, a light emitting element is provided at the center of a wiring board, and light from this light emitting element is guided to both sides so as to pass through a running path of a tape. A plastic central prism is installed in the center of the chassis, and plastic side prisms that receive the light from the central prism and guide it to each light receiving element are installed on both sides of the chassis to detect the beginning and end of the tape. What you have done is known.

[0003]

However, in the conventional tape deck, although the end faces of the central prism and the prisms on both sides through which light goes in and out are formed to be flat, the surface is uneven, so that the scattering of light occurs. However, there is a problem that the amount of received light becomes unstable and the amount of received light becomes unstable due to a deviation of the optical axis due to an attachment error of each prism. The present invention has been made in view of the above points, and an object of the present invention is to obtain a stable light receiving amount by increasing the transmission efficiency of a light transmission path, and thus to accurately detect the end and beginning of a tape. It is an object of the present invention to provide a light guide device suitable for use in a tape deck that can be manufactured.

[0004]

In order to solve the above-mentioned problems, the light guide device of the present invention is configured such that the light receiving surface of the light guide member is formed in a concave shape and the light guide member on the side facing the light receiving element. Is characterized in that the end face of is formed in a convex shape. Further, it is characterized in that the light of the light emitting element is guided to the light receiving element through the prism and the optical fiber.

[0005]

According to the light guide device of the present invention, since the end surface of the prism, which is the light guide, has a lens function, the loss due to scattering at the time of incidence and emission of light is reduced. Further, by using an optical fiber as a light guide, the loss of light is reduced and the light guide path can be set freely.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a main part of a light guide device of the present invention,
2 to 4 are views showing a tape deck having the light guide device of the present invention, and FIG. 5 is a view showing another embodiment of the present invention.
In the figure, 1 is a deck chassis, 2 is a rotatable head cylinder in which a recording / playback head or the like is mounted on the deck chassis 1, and 3 and 4 stand on slide bodies 7 and 8 which slide and guide via rails 5 and 6. The tape loading pins 10 and 11 are provided for winding the magnetic tape 9a of the video cassette 9 around the head cylinder 2, and supply and take-up reel shafts for engaging reels of the video cassette 9, and 12 for recording audio signals and the like. A head, 13 is an erasing head, 14 is a capstan, and 15 is a pinch roller.

Reference numeral 16 is a cassette holder for supporting the video cassette 9, and reference numerals 17 and 18 are left and right guide plates on which the cassette holder 16 is movably attached to a cassette loading / unloading position or a recording / reproducing position by standing on the upper surface of the deck chassis 1. 1
9 is a tape running motor for rotating the capstain 14,
Reference numeral 20 denotes a loading motor for driving the tape loading lever 21, the cassette loading gears 22, 22 and the like. The tape loading lever 21 is slid by the loading motor 20 to rotate the cassette loading gears 22, 22 forward and backward to rotate the cassette. The holder 16 is configured to reciprocate.

Further, below the deck chassis 1 is shown in FIG.
As shown in, the wiring board 23 on which the recording / reproducing circuit, the motor control circuit, and the like are assembled is screwed through the spacer 24.
Light emitting diode 2 which is a light emitting element
5 and the phototransistors 26, 26, which are light receiving elements, are directly attached and fixed to the central portion and both side portions of the wiring board 23.

On the other hand, in the central portion of the deck chassis 1 corresponding to the light emitting diode 25, a square prism-shaped central prism 27 made of acrylic resin is provided.
The central prism 27 facing the light emitting diode 25 is locked and fixed by a hook 28 provided by an outsert.
The lower end surface of is a concave light receiving surface 27a, and the central prism 27 is provided with a left reflecting surface 29 and a right reflecting surface 30 at the upper end thereof so that the light from the light emitting diode 25 is not scattered to the center. It is configured to enter the prism 27 and be guided to both sides via the left reflecting surface 29 and the right reflecting surface 30.

Further, on the side portions where the phototransistors 26, 26 are assembled, side prisms 31, 32 of a rectangular prism shape made of acrylic resin are locked and fixed by hooks 33 integrally formed on the guide plates 17, 18. And the respective side prisms 3 facing the phototransistors 26, 26.
Emitting surfaces 31a, 3 having lower end surfaces of 1, 32 formed in a convex shape
2a. The light from the left reflecting surface 29 and the right reflecting surface 30 of the central prism 27 is used as inspection holes 33a, 33a, 34, 34 of the video cassette 9 at the recording / reproducing position.
And the transparent tapes 35, 36 at the beginning and end of the magnetic tape 9a.
Is passed through to enter the upper ends of the bilateral prisms 31 and 32, and is bent downward by the respective reflecting surfaces 31b and 32b to detect the end and the start of the magnetic tape 9a. The right side prism 3
2 is formed in a crank shape, and a reflecting surface 32 is provided on the way.
c and 32d are formed. By configuring the present embodiment as described above, the emission direction of light can be changed by changing the convex shape of the side prism, the arrangement position of the phototransistor which is the light receiving element can be changed, and the restriction of the component position on the circuit arrangement is limited. Can be eliminated.

FIG. 5 is a front view of the essential parts showing another embodiment of the light guide device of the present invention. In this embodiment, instead of the above-mentioned side prisms 31, 32, optical fibers 38,
39 and the convex lenses 40 and 41, the central prism 27
Light from the left anti-slope 29 and the right reflection surface 30 of the video cassette 9 at the recording / reproducing position is used as the inspection holes 33a, 33a, 3 of the video cassette 9.
4, 34 and the transparent tape 3 at the beginning and end of the magnetic tape 9a
5 and 36, and from the convex lenses 40 and 41 on both sides to the upper ends 38a of the optical fibers 38 and 39,
The light from the lower end portions 38b and 39b is guided to each phototransistor 26, and the end and the start of the magnetic tape 9a are detected. Since other configurations and operations are similar to those of the above-described embodiment,
The same components and the like are designated by the same reference numerals and the description thereof will be omitted.

[0012]

As described above, since the light guide member of the present invention is configured as described above, the loss due to the scattering of light at the entrance and exit of the prism is reduced, so that the light transmission efficiency is reduced. It is possible to obtain a stable amount of received light by increasing. Further, since an optical fiber is used, it is possible to absorb variations in manufacturing dimensions, and therefore, it has an excellent feature such as being inexpensive.

[Brief description of drawings]

FIG. 1 is a front view of a main part showing an embodiment of a light guide member of the present invention.

FIG. 2 is a plan view of a tape deck to which the light guide member of the invention is applied.

FIG. 3 is a bottom view of FIG.

FIG. 4 is likewise a plan view showing cassette loading.

FIG. 5 is a front view of the main part showing another embodiment of the present invention.

[Explanation of symbols]

 1 Deck Chassis 9 Video Cassette 9a Magnetic Tape 25 Light Emitting Diode (Light Emitting Element) 26 Phototransistor (Light Sensing Element) 27 Central Prism (Light Guide Member) 27a Light Receiving Surface 29 Left Anti-Slope 30 Right Reflecting Surface 31, 32 Side Prism (Conducting) Optical member) 31a, 32a Emission surface 31b, 32b Anti-slope surface 38, 39 Optical fiber

Claims (2)

[Claims] 1. A light guide device, wherein the light receiving surface of the light guide member is formed in a concave shape and the end surface of the light guide member facing the light receiving element is formed in a convex shape. 2. A light guide device, which guides light of a light emitting element to a light receiving element via a prism and an optical fiber.