JPS6216582A - Photo-interrupter - Google Patents

Abstract

PURPOSE:To obtain high resolution without lowering optical transmittance by giving resolution in the direction of the thickness of a light-emitting element chip by using light emission from the end surface of the chip or giving resolution in the direction of the short side of a rectangle while a light-receiving section for a light-receiving element is used as the rectangle. CONSTITUTION:An infrared light-emitting diode chip 11 is loaded on the nose surface of a lead frame 14, and an electrode 12 on the infrared light-emitting diode chip 11 and another lead frame 15 are connected by a gold wire 13. Beams emitted from a GaAs infrared light-emitting diode prepared through a liquid- phase epitaxial growth system are both radiated equally from the upper surface and end surface of the chip. Beams emitted from the end surface having narrow width determined by the thickness of the chip are employed, thus acquiring high resolution. The width of beams emitted from the end surface 16 of the infrared light-emitting diode chip 11 are sufficiently narrow, and this light emission having narrow width is introduced to a light-receiving element 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a photointerrupter, which is an optical sensor that detects an object passing between a light emitting element and a light receiving element.

<Prior Art> As shown in FIG. 4, a photointerrupter includes a light emitting element 41 made of, for example, an infrared light emitting diode, a phototransistor or a photodiode, and an amplification and signal processing circuit inside a holder 45 made of a light-shielding material. A light-receiving element 42 consisting of a one-chip circuit is arranged facing each other, and the light-emitting element 41 and the light-receiving element 42 are connected to lenses 43 and 44.
Each is covered with a translucent resin that forms a . The reason why the lenses 43 and 44 are formed is to increase the light transmission rate from the light emitting element 41 to the light receiving element 42.

In this photointerrupter, a shielding object 4, which is an object to be detected, is used.
6 passes between the light-emitting element 41 and the light-receiving element 42 to block the light emission of the light-emitting element 41, and the shielding object 46 is detected based on the change in the output of the light-receiving element 42.

FIG. 5 shows the change in the output of the light receiving element with respect to the movement of the shielding object. If the resolution is the moving distance of the shielding object required for the output of the light-receiving element to change from, for example, 90% to 10% of the output when there is no shielding, then in the above-mentioned photointerrupter, the light receiving element changes as shown by curve a. Since the output change of the element 42 is gradual, the resolution d' is low. This is due to the diffusion of light by the lens 43 and the width of the opening 49 of the holder 45 that covers the lenses 43,44. In this case, it is a design choice to set the threshold at the output value of the light receiving element, but since there are variations in the output and current amplification factor of light emitting diodes and phototransistors, it is not necessary to adjust them individually. Therefore, any point in the output fluctuation width of curve a becomes the threshold value. The resolution is
In the case of a photointerrupter having the structure described above, the diameters of the lenses 43 and 44 or the width of the opening 49 of the holder 45 that covers the lenses 43 and 44 are dominant.

Therefore, in order to improve the resolution, methods such as narrowing the width of the opening 49 and providing a special slit plate were taken, and as a result, a high resolution d (FIG. 5) was obtained. However, in this method, as the resolution increases, the optical transmission rate decreases, and therefore, there are constraints that reduce the S/N ratio, such as the need to increase the signal amplification factor in the subsequent circuit.

<Object of the Invention> The present invention has been made in view of the above-mentioned circumstances, and its object is to provide a photoinclutter with high resolution and increased light transmission rate.

<Structure of the Invention> According to the present invention, a light-emitting element and a light-receiving element are arranged facing each other, and an object passing between the light-emitting element and the light-receiving element blocks light emission from the light-emitting element, thereby detecting the object. The photointerrupter is characterized in that it is formed so that light emitted from an end face in the thickness direction of the chip of the light emitting element is guided to the light receiving element, and has resolution in the thickness direction of the chip.

<Example> An embodiment of the present invention will be described below.

FIG. 1 shows the cross-sectional structure of the photointerrupter of this embodiment. A light emitting element 1 and a light receiving element 2 are arranged facing each other inside a holder 5 made of a light-shielding material. The light emitting element 1 and the light receiving element 2 are housed in a package 3. made of translucent resin.
4 respectively. The packages 3 and 4 have a rectangular cross-sectional shape and do not form lenses. The light emitting element 1 emits light through the openings 9a+9b of the package 3 and holder 5.
The light is guided to the light receiving element 2 via the S package 4. Shade 6
When the light passes between the light emitting element 1 and the light receiving element 2, the light emitted from the light emitting element 1 is blocked and does not reach the light receiving element 2.

FIG. 2 shows the structure of the light emitting device 1. As shown in FIG. An infrared light emitting diode chip 11 is mounted on the tip surface of the lead frame 14,
The electrode 12 on the infrared light emitting diode chip 11 and another lead frame 15 are connected by a gold wire 13. The area of the electrode 12 on the infrared light emitting diode chip 11 may be set as wide as necessary, and may cover the entire upper surface of the infrared light emitting diode chip 11. The light used as a photointerrupter is light in the direction of arrow A, that is, light emitted from the end surface 16 of the infrared light emitting diode chip 11 in the chip thickness direction.

The light emitted from a gallium arsenide infrared light emitting diode manufactured by liquid phase epitaxial growth is equally emitted from both the top surface and the end surface of the chip. Since this gallium arsenide infrared light emitting diode cannot be assembled into a very narrow chip, the present invention does not use the light emitted from the top surface of the chip as the light output of the photointerrupter due to its large width, and the width is determined by the thickness of the chip. By using light emitted from narrow end faces, high resolution can be obtained.

In this case, the photointerrupter has resolution in the thickness direction of the infrared light emitting diode chip 11. That is, the width of the light emitted from the end face 16 of the infrared light emitting diode chip 11 is sufficiently narrow, and this narrow light emission is guided to the light receiving element 2. Even if there is some variation in the length of the chip side of the infrared light emitting diode chip 11, in this case, the amount of light will only change slightly, and the resolution of the photointerrupter will not be reduced.

FIG. 3 shows the structure of the light receiving element 2. As shown in FIG. A phototransistor chip 21 is mounted on the end of a lead frame 22, and this phototransistor chip 21 and another lead frame 23 are connected by gold wires 24. The phototransistor chip 2-1 has a rectangular light receiving section 25, into which light from the light emitting element 1 is incident. In this case, the photointerrupter has resolution in the short side direction of the light receiving section 25 of the phototransistor chip 21. The area of the light receiving section 250 is reduced, and the phototransistor chip 21
If a Darlington type phototransistor is configured in which an amplification transistor (not shown) is placed in the other part of the phototransistor, even if the current amplification factor of the phototransistor is high, the junction capacitance between the base and the collector is small, so it is difficult to compare the response speed. A fast phototransistor can be obtained.

In the photointerrupter configured as shown in FIG. 1 by combining the above-mentioned light emitting element 1 and light receiving element 2, the curve shown in FIG. The shielding characteristics shown above are obtained, and a high resolution d corresponding to the width of the end face 16 of the infrared light emitting diode chip 11, that is, the chip thickness, or the width of the light receiving portion 25 of the phototransistor chip 21 is obtained. For example, this resolution is practically possible up to 0.2 to Q, 3 mm.

In this embodiment, the light emitted from the chip end face of the light emitting element is used as the optical output of the photointerrupter, and this light is guided to the light receiving element having a rectangular light receiving part. A certain level of high resolution can be obtained by guiding the emitted light to a conventional light-receiving element, or by guiding the emitted light from a conventional light-emitting element to a light-receiving element having a rectangular light-receiving section.

In addition, in the above-mentioned embodiment, the opening 9a of the holder 5
, 9b are not necessary in terms of shielding characteristics, but it is a good idea to limit them to an appropriate size in order to avoid noise such as disturbance light and reflected light from shielding objects.

<Effects of the Invention> As explained above, in the present invention, resolution is provided in the thickness direction of the chip by using light emitted from the end face of the light emitting element chip, or the light receiving part of the light receiving element is made rectangular, and the light receiving part of the light receiving element is made rectangular. Since the resolution is provided in the side direction, high resolution can be achieved without reducing the light transmittance, and the performance of the photoincluctor can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a cross-sectional structure of an embodiment of the present invention, Fig. 2 is a perspective view showing the structure of a light emitting element according to an embodiment of the invention, and Fig. 3 is a perspective view showing the structure of a light receiving element according to an embodiment of the invention. , FIG. 4 is a diagram showing the cross-sectional structure of a conventional example, and FIG. 5 is a graph showing the shielding characteristics of the photointerrupter. ■... Light emitting element 2... Light receiving element 6... Shielding object 11... Infrared light emitting diode chip 16... End face 21... Phototransistor chip 25... Light receiving part

Claims (3)

[Claims] (1) A photointerrupter in which a light-emitting element and a light-receiving element are disposed facing each other, and an object passing between the light-emitting element and the light-receiving element detects the object by blocking the light emission of the light-emitting element. A photointerrupter characterized in that it is formed so that light emitted from an end face in the thickness direction of a chip of the element is guided to the light receiving element, and has a resolution in the thickness direction of the chip. (2) A photointerrupter in which a light emitting element and a light receiving element are disposed facing each other, and an object passing between the light emitting element and the light receiving element detects the object by blocking light emission from the light emitting element. A photointerrupter characterized in that the element has a rectangular light-receiving section and has resolution in the short side direction of the rectangle. (3) The photointerrupter according to claim 1 or 2, which is formed by combining the light emitting element and the light receiving element.