JPS61239123A - Photodetector - Google Patents

Abstract

PURPOSE:To expand the measuring range of a photoelectric converting element by detecting an output from the photoelectric converting element, and making the incident light on the photoelectric converting element variable. CONSTITUTION:The light which has transmitted through a light depreciating element 5 and has been made incident on a photoelectric converting element 1 is inputted to a comparator 4 through an amplifier 2. In this case, the comparator 4 having a hysteresis characteristic compares an output voltage of the amplifier 2, and a reference voltage of a reference voltage generator 3, generates an H level signal in case when the output voltage from the amplifier 2 is lower than the reference voltage, and generates a signal of an L level in case when said output voltage is higher than the reference voltage. When the signal of an L level has been generated, the transmittivity of the light depreciating element 5 is lowered in order to limit the incident light on the photoelectric converting element 1, and also switches a feedback resistance by interlocking an amplification degree changeover switch 6. In this way, in case when the light of a range being out of the linearity has been made incident, an output of the amplifier 2 of the photoelectric converting element 1 is detected, and the incident light is limited electrically, therefore, the measuring range of the photoelectric converting element 1 can be expanded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is characterized by detecting the output from a photoelectric conversion element and expanding the measurement range of the photoelectric conversion element by varying the incident light to the photoelectric conversion element. The present invention relates to a photodetector.

Prior Art FIG. 6 shows the configuration of a conventional photodetector using a photoelectric conversion element. 11 is a photoelectric conversion element that generates a current according to the amount of incident light; 12 is an amplifier that amplifies the output of the element 11; 13 is a switch that switches the feedback resistor 14 and 14' of the amplifier;
A display 16 displays an output value corresponding to the amount of light, for example, an illuminance value.

In a photodetector using this type of photoelectric conversion element, the range in which incident light can be correctly detected is limited by the linearity of the photoelectric conversion element. In such a photodetector, in order to detect incident light in a range that deviates from the linearity of the photoelectric conversion element, it is necessary to detect incident light within the linearity range of the photoelectric conversion element 110 without changing the spectral sensitivity of the photoelectric conversion element 110. It was necessary to limit the light and to change the amplification degree of the amplifier 12 in accordance with changes in the light incident on the photoelectric conversion element.

For this reason, the incident light is restricted by attaching and detaching a metal plate 16 with a plurality of openings in front of the photoelectric conversion element, and the amplification degree of the amplifier is changed by switching the feedback resistor. Ta.

Problems to be Solved by the Invention However, with this method of using a light attenuation plate such as a metal plate, it is necessary to manually attach and remove the light attenuation plate, and when attaching and removing the light attenuation plate, there are problems. It is conceivable that the light attenuation plate may be damaged or that dirt may adhere to the light receiving surface of the photoelectric conversion element. Figure 6 shows an example of actual measurements of errors in output values caused by dirt that adhered to the light-receiving surface of the photoelectric conversion element when attaching and removing the attenuation plate in a photodetector using a attenuation plate. There is a maximum error of 4%.

The present invention solves the problems caused by the method of mechanically restricting the light incident on the photoelectric conversion element by attaching and detaching the attenuation plate, accurately detects the incident light on the photoelectric conversion element, and measures the photoelectric conversion element. The purpose is to expand the scope.

Means for Solving the Problems The present invention provides a photoelectric conversion element that generates a current according to the amount of incident light, an amplifier that amplifies the output of the photoelectric conversion element, a reference voltage generator that generates a reference voltage, and an amplifier. In addition to detecting the output and comparing it with a reference voltage, there is also a comparator with hysteresis characteristics, a dimming element that controls the incident light to the photoelectric conversion element based on the output of the comparator, and an amplifier that operates in conjunction with the operation of the dimming element. It consists of an amplification degree changeover switch that changes the feedback resistance.

Effect of the present invention By configuring the photodetector as described above, the incident light to the photoelectric conversion element is electrically changed according to the output value from the amplifier that amplifies the output of the photoelectric conversion element, and The feedback resistance of the amplifier can be switched in conjunction with changes in the light incident on the photoelectric element. Therefore, if light in a range that deviates from its linearity is incident on a photoelectric conversion element, the output from the amplifier of the photoelectric conversion element is detected and the incident light is electrically limited, so the measurement range of the photoelectric conversion element is can be expanded.

Embodiment FIG. 1 shows a circuit diagram of a photodetector in an embodiment of the present invention. @1 In the figure, 1 is a photoelectric conversion element that generates a current according to the amount of incident light, 2 is an amplifier that amplifies the output of the photoelectric conversion element, 3 is a reference voltage generator that generates a reference voltage, and 4 is the output of the amplifier. A comparator that detects and compares it with a reference voltage and has a hysteresis characteristic, 6 is a dimming element that controls the incident light to the photoelectric conversion element by the output of the comparator, and 6 is a dimming element that controls the amplifier in conjunction with the operation of the dimming element. An amplification changeover switch for changing over the feedback resistors 7 and 7', and 8 an indicator.

FIG. 2 shows a configuration diagram of the light receiving section in the photodetector of the present invention. In FIG. 2, a diffuser plate 9 and a diffuser plate 9' are used to prevent errors from occurring in measured values due to the influence of polarized light when measuring polarized light.

In such a photodetector, light that passes through the light attenuation element 6 and enters the photoelectric conversion element 1 is amplified by the amplifier 2 and input to the comparator 4 . At this time, the comparator 4 compares the output voltage of the amplifier 2 and the reference voltage output from the reference voltage generator 3, and when the output voltage from the amplifier 2 is lower than the reference voltage, a high level signal is output. occurs, and when the output voltage from the amplifier 2 becomes higher than the reference voltage, that is, when strong light outside the range in which the linearity of the photoelectric conversion element 1 can be maintained is incident on the photoelectric conversion element 1, the low (L)
ow) level signal. When a low level signal is generated, in order to limit the light incident on the photoelectric conversion element 1, the transmittance of the dimming element 5 is lowered and the amplification changeover switch 6 is operated to switch the feedback resistor. Here, if the comparator 4 does not have a hysteresis characteristic, when the light attenuation element 5 limits the incident light to the photoelectric conversion element 1, the output voltage from the amplifier 2 will be lower than the reference voltage, so the comparison A high level signal is generated from the device 4, which increases the transmittance of the dimming element 6, and also causes the amplification changeover switch 6 to change over the feedback resistor.

Therefore, when strong light outside the range in which the linearity of the photoelectric conversion element 1 can be maintained continues to enter the photoelectric conversion element 1, the comparator 4 outputs a high level signal and a low level signal.
The level signals are output alternately, and the change in the transmittance of the light attenuating element 6 and the switching of the feedback resistor occur intermittently (chattering phenomenon), and accurate setting of the transmittance of the light attenuator 6 and setting of the feedback resistor. I can't do it. Therefore, the comparator 4 is provided with a hysteresis characteristic as shown in FIG.
When an OW level signal is generated, the fifth set voltage is lowered by a set value of the reference voltage than the output voltage value from the amplifier 2 of the incident light limited by the light attenuation element 5.
Even if the optical power is input as shown in the figure, the chattering phenomenon does not occur because the operating range of the comparator 4 is expanded as shown in FIG.

Similarly, when the incident light on the light attenuation element 6 decreases and becomes lower than the reference voltage, a high level signal is generated from the comparator 4, and the transmittance of the light attenuation element 5 increases. The feedback resistor is switched and the reference voltage is returned to the high level set value to prevent the chattering phenomenon.

Furthermore, in order to simplify the explanation, in the embodiment, switching between the attenuation rate and the feedback resistance of the dimmer element 1 is described as one stage, but by providing a plurality of comparators 4 and feedback resistors, the dimmer element 1 By changing the applied voltage to the light attenuating element 1,
It is possible to set the transmittance in multiple stages, for example, 1/10''/100, and to switch the feedback resistance, further expanding the measurement range by □.

Effects of the Invention According to the present invention, the measurement range of a photodetector using a photoelectric conversion element can be expanded.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a photodetector according to an embodiment of the present invention, Figure 2 is a configuration diagram of its light receiving section, Figure 3 is a diagram showing the hysteresis characteristics of a comparator, and Figure 4 is a diagram of the photoelectric conversion element. Figure 6 is a circuit diagram of a conventional photodetector. Figure 6 is a photodetector using a light attenuation plate, and when the light attenuation plate is attached and removed, the photoelectric conversion element is This is a diagram showing the error caused in the output value due to dirt attached to the light receiving surface. 1...Photoelectric conversion element, 2...Amplifier,
3... Reference voltage generator, 4... Comparator, 5... Dimming element, 6... Amplification degree changeover switch, 7.7'.・River/return resistance. Name of agent: Patent attorney Toshi Nakao (Male)
Postal Zehaku 2 Figure 343 Figure V2 k/. Base 1 is a special edition of 4 drawings

Claims (1)

[Claims] A photoelectric conversion element that generates a current according to the amount of incident light, an amplifier that amplifies the output of the photoelectric conversion element, a reference voltage generator that generates a reference voltage, and a hysteresis system that detects the output of the amplifier and compares it with the reference voltage. It consists of a comparator with a characteristic, a dimming element that controls the incident light to the photoelectric conversion element by the output of the comparator, and an amplification changeover switch that switches the feedback resistance of the amplifier in conjunction with the operation of the dimming element. Photodetector.