JP3194321B2 - Photo coupler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called photocoupler capable of transmitting a signal between electrically separated systems via light.

[0002]

2. Description of the Related Art The basic structure of a conventional photocoupler is shown in FIG. A light source 101 such as a light emitting diode and a light receiving element 601 such as a photodiode or CdS are
It has a structure sealed inside. In such a photocoupler, when the voltage input to the light source 101 changes, the amount of light emitted from the light source 101 changes, and an output voltage according to the light reception amount-output voltage characteristic of the light receiving element 601 can be obtained. For example, as shown in FIG. 7A, a linear change with respect to the amount of received light or a binary characteristic having a certain threshold as shown in FIG. 7B can be provided. .

[0003]

However, since the output voltage of such an element depends on the amount of received light versus the output voltage characteristic of the light receiving element 601, it has been difficult to output an arbitrary output waveform. Therefore, in order to obtain an arbitrary characteristic, it is necessary to add an external output voltage conversion circuit or the like. For example, in a liquid crystal display, a photocoupler is often used for adjusting luminance and hue, but the characteristic of transmittance with respect to a signal voltage is not linear. To correct this, complicated additional circuits such as an AD / DA conversion circuit and a look-up table are required.

An object of the present invention is to provide a photocoupler capable of taking out an output voltage having an arbitrary relationship with an input voltage by solving such a problem of a conventional device.

[0005]

According to the present invention, a light source, a reflection element whose reflection angle is changed by an externally applied voltage, and a shape of a light receiving portion are changed according to an arbitrary function. And a photoelectric conversion element whose output voltage changes according to the area of light received and received.The elements from the light source are reflected by the reflection element and the reflected light is incident on the photoelectric conversion element. It is characterized by being arranged.

[0006]

According to the present invention, an optical element whose reflection angle can be varied electrically is arranged between a light source and a light receiving element, and the shape of the light receiving section is formed so as to change according to an arbitrary function. By doing so, the output voltage that has been changed only by the amount of received light can be changed by the shape of the light receiving unit.

[0007]

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. The light from the light source 101 is formed into a certain shape by the slit 102. The light that has passed through the slit 102 is reflected by the reflection element 103, and
4 The light receiving unit 105 of the light receiving element 104 has a shape according to a function having a width in a direction in which light moves. The angle of the reflection element 103 can be changed by an external input voltage applied to the drive unit 106. The simplest such element is known as a so-called galvanometer mirror.
Reference numeral 107 denotes a housing for shielding external light. The inside of the housing 107 is treated to prevent diffuse reflection.

The manner in which the output voltage changes in such a structure according to an external input voltage will be described with reference to FIG. In this case, it is assumed that the shape of the light receiving unit 105 is proportional to the moving direction of the light 201. FIG. 2 (a)
Is when light from the light source 101 is reflected at an angle,
The output voltage is equal to the light 201
Is proportional to the length L1. FIG. 2B shows the state when the reflection angle changes due to a change in the input voltage from the outside. The output voltage at this time is proportional to L2, as in FIG. That is, the output voltage with respect to the input voltage is represented by the width L of the light receiving portion with respect to X when the X axis is taken as shown in the figure.
However, if A is a certain positive constant, there is a proportional relationship such as L = AX. Thus, the output voltage can be arbitrarily changed with respect to the input voltage depending on the shape of the light receiving unit. CdS is well known as an element whose photoelectric conversion output changes depending on the area of a light receiving portion.

FIG. 3 shows an example of the shape of the light receiving unit 105 for obtaining another functional relationship. FIG. 3A shows a so-called inversion circuit in which the width L of the light receiving unit with respect to X is L = -AX. FIG.
(B), when the width L of the light receiving portion with respect to X is B as a constant, the output is proportional to the square of the input, such as L = BX ² . FIG.
(B) has a binary characteristic having a certain threshold value.

Here, a slit 102 is used to determine the shape of the light, but this is for making the light from the light source 101 into a certain shape, and is a slit 102 as shown in FIG. No need. For example, the reflection element 10
The reflecting surface of No. 3 may be linear. The resolution of the output voltage can be changed depending on the shape of the light. In addition, an optical element such as a lens can be inserted between the light source 101 and the light receiving element 104 in order to improve the light collecting property. Further, the voltage input to the light source 101 has been described as being constant. However, it is also possible to change the voltage to have a more complicated functional relationship between input and output.

(Embodiment 2) FIG. 4 is a diagram showing a second embodiment of the present invention. As the reflecting element, not a mechanical element as used in the first embodiment, but a so-called optical deflecting element 40 whose reflection direction can be changed by an externally applied voltage.
1 is used.

FIG. 5 shows an example of such a reflection element.
The translucent electrode 501 and the electrode 502 form the variable refractive index medium 50.
3 and a translucent medium 504. Inside the element, the variable refractive index medium 503 and the light transmitting medium 504 form a layer structure having different refractive indexes. The translucent electrode 501 is in contact with the layer structure via a region including the variable refractive index medium 503. Such a layer structure is equivalent to a mirror surface having wavelength selectivity under the condition of so-called Bragg diffraction as long as the layer interval is about the wavelength of light. When the incident light 505 is irradiated, a reflected light 506 is obtained. When a voltage is applied to the electrodes 501 and 502 to change the refractive index of the variable refractive index medium 503, the angle of incidence on the layered structure changes, so that the direction of the emitted light changes and reflected light 507 is obtained. By continuously changing the voltage, continuous light deflection is realized. In this structure, since the structure of the reflection element is simple, it is possible to reduce the size of the entire element. In addition, since there is no mechanical part, mechanical strength against vibration and the like is improved.

[0013]

According to the present invention, it is possible to obtain an output waveform having an arbitrary functional relationship with the input voltage. Therefore, various peripheral circuits, which have been conventionally required to obtain an arbitrary function, become unnecessary, and effects such as reduction in the number of components and improvement in reliability can be expected. In addition, a complicated arithmetic element can be realized by combining the elements of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing that an output voltage changes.

FIG. 3 is an explanatory diagram showing a relationship between a light receiving portion shape and an output voltage.

FIG. 4 is a configuration diagram showing a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a light polarizing element.

FIG. 6 is a configuration diagram showing a conventional technique.

FIG. 7 is a characteristic diagram showing the relationship between the amount of received light and the output voltage in the related art.

[Explanation of symbols]

 Reference Signs List 101 light source 102 slit 103 reflecting element 104 light receiving element 105 light receiving section 106 driving section 107 light shielding casing 201 light 401 light polarizing element 501 transparent electrode 502 electrode 503 refractive index variable medium 504 translucent medium 505 incident light 506, 507 reflected light

Continuation of the front page (56) References JP-A-1-110780 (JP, A) JP-A-63-178036 (JP, U) JP-A-62-33127 (JP, U) JP-A-55-173837 (JP) , U) Actual opening 52-113263 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/12

Claims (2)

(57) [Claims] 1. A light source, a reflective element whose reflection angle changes according to an externally applied voltage, and a photoelectric element whose output voltage changes according to an area for receiving and forming a shape of a light receiving portion so as to change according to an arbitrary function. A photocoupler comprising a conversion element, wherein each element is arranged such that light from the light source is reflected by the reflection element and the reflected light enters the photoelectric conversion element. 2. The photocoupler according to claim 1, wherein the reflection element has a multilayer structure including a transparent electrode and a material interposed between the electrodes and having different refractive indexes.