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Optical sensor and electronic device

A light sensor, photoelectric technology, applied in the field of light sensor

Active Publication Date: 2013-04-03
SHARP KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0023] Therefore, such a voltage increases the voltage drop between the two terminals

Method used

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  • Optical sensor and electronic device
  • Optical sensor and electronic device
  • Optical sensor and electronic device

Examples

Experimental program
Comparison scheme
Effect test

Embodiment approach 1

[0082] (Circuit structure of light sensor)

[0083] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0084] figure 1 The circuit configuration of the photosensor according to the first embodiment is shown. The light sensor includes a phototransistor represented by an equivalent circuit composed of a photodiode 11 (photoelectric conversion element), a transistor 12 , and a resistor 13 in a light receiving element 1 . The light-receiving element 1 is a two-terminal light-receiving element that outputs a signal by changing the potential of one terminal from the fixed potential of the other terminal by changing the circuit current when light is input. In this embodiment, the terminal at a fixed potential is grounded. Conversely, it is also possible to set the power supply voltage Vcc to a fixed potential. In addition, the light receiving element 1 has a first current mirror circuit 14 composed of transistors 14a a...

Embodiment approach 2

[0094] (Circuit structure of light sensor)

[0095] The optical sensor according to Embodiment 1 has a structure in which photocurrent is amplified by the second current mirror circuit 15 . However, in this structure, especially when the photocurrent is small, the potential fluctuation of the sensor may become insufficient. Therefore, as in the photosensor of Embodiment 2, by converting the photocurrent or the amplified photocurrent to a voltage, and driving the transistor by switching (switching) when reaching a specific voltage, a larger the fixed current. This is advantageous because the electric potential of the sensor can be stably increased.

[0096] refer to figure 2 The circuit configuration of the photosensor according to Embodiment 2 will be described. figure 2 The light sensor shown is in place of the figure 1 The light receiving element 1 is provided with the structure of the light receiving element 2 . and figure 1 The same structure uses the same compon...

Embodiment approach 3

[0103] (Circuit structure of light sensor)

[0104] refer to image 3 The circuit configuration of the photosensor according to Embodiment 3 will be described. image 3 The light sensor shown is in place of the figure 2 The light receiving element 2 is provided with the structure of the light receiving element 3 . and figure 2 The same structure uses the same component number, and the detailed description is omitted.

[0105] The light receiving element 3 includes a current source composed of a third current mirror circuit 31 and a resistor 32 as a current source provided in parallel with the photodiode 11 . Furthermore, an input-side transistor 31 a in the third current mirror circuit 31 is connected to an output detection terminal of the light receiving element 3 via a resistor 32 . The transistor 31 b on the output side of the third current mirror circuit 31 inputs a current to the first current mirror circuit 14 , which is an amplifier common to the photodiode 11 . ...

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PUM

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Abstract

The invention relates to an optical sensor and an electronic device. When no light enters a photodiode, a second current mirror circuit operates. Consequently, a current that decreases a potential difference between two terminals of a light-receiving element flows into a transistor of the second current mirror circuit and an output of an optical sensor becomes low. Meanwhile, when light enters the photodiode, a transistor of the light-receiving element is turned on and the second current mirror circuit stops operating. Consequently, the current that decreases the potential difference between the two terminals of the light-receiving element is stopped in the transistor of the second current mirror circuit and the output of the optical sensor becomes high. This makes it possible to provide an optical sensor that has a circuit in which an output of a light-receiving element does not depend on a photocurrent and that is capable of operating at a high speed.

Description

technical field [0001] The present invention relates to an optical sensor for object detection or object motion speed detection, and relates to an optical sensor using a photo interrupter which requires a light receiving element to be two terminals. Background technique [0002] In the detection of the lens movement speed of a digital camera, etc., a photointerrupter with two terminals as a light receiving element is used. In addition, conventionally, phototransistors have been used as light-receiving elements of photo-interrupters. [0003] Figure 7 The structure of a conventional light receiving element using a phototransistor is shown. When light is input to this light receiving element, an amplified current obtained by multiplying the photocurrent by hfe flows between the output detection terminal and GND, thereby generating a potential difference in the external resistor. And, by this potential difference, the voltage of the output detection terminal drops, enabling ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01J1/44
CPCG01J1/44H03F3/08
Inventor 冈田教和
Owner SHARP KK
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