JPH04269637A - Photoelectric conversion apparatus - Google Patents

Abstract

PURPOSE:To improve responsiveness by using a photomultiplier tube as the output amplifier of a photoelectric converter element, utilizing the gain adjusting function in a broad range provided in the photomultiplier tube, and making bias ray incident on the photoelectric converter element. CONSTITUTION:A photomultiplier tube 1 has a cathode electrode 1k having the photoelectric surface which discharges photoelectrons, diode electrodes 1d in plural stages and one anode electrode 1a. A photoelectric conversion element 4 for converting incident light ray into the electric signal is connected between the electrode 1k of the photomultiplier tube 1 and a variable DC voltage source 2. The electrode 1a is connected to the input terminal of an operation amplifier 3 for converting current into voltage. A first light source 5 emits a specified amount of bias light rays 12 which is to become the bias on the element 4 in addition to the incident light ray 13 which is to be converted into the electric signal. A second light source 11 emits the specified amount of light ray 14 on the electrode 1k. Therefore, the incident light ray 13 whose amount is changed is converted into the electric signal so that the linearity of the electric signal with respect to the intensity is maintained, and the responsiveness is improved.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD This invention relates to a photoelectric conversion device that converts an incident light beam whose amount of incident light varies over a wide range into an electrical signal. The present invention relates to a photoelectric conversion device with improved responsiveness.

0002

2. Description of the Related Art When a solar cell or a PIN photo diode is used as a photoelectric conversion element in an optical temperature measuring device such as a color thermometer or a brightness thermometer, an amplifier for amplifying the output of the photoelectric conversion element is used. Transistor amplifiers connected in multiple stages and amplifiers integrated into ICs were used.

0003

[Problem to be solved by the invention] The amount of light incident on the solar cell or PIN photo diode that becomes the photoelectric conversion element is
The amount of light changes significantly over tens of thousands of lx, and the output of the photoelectric conversion element may also change significantly. If you try to amplify that output using a normal amplifier, the gain of the amplifier will increase over 100 db or more. Since it is necessary to adjust the gain over a wide range and it is extremely difficult to adjust the gain over such a wide range, there is a limit to the amount of incident light that can be tolerated.
If the amount of incident light was too large, it had to be limited by an aperture.

0004

[Means for Solving the Problems] Therefore, the present invention was devised to solve such problems, and uses a photomultiplier tube as an amplifier to amplify the output of a photoelectric conversion element. , the response is improved by making use of the wide range gain adjustment function of the photomultiplier tube and by making a bias beam incident on the photoelectric conversion element.

[0005]

[Embodiment] (Technology on which the present invention is based) As shown in FIG. 3, a photomultiplier tube 1 includes a cathode electrode 1k having a photocathode that emits photoelectrons when light 10 is incident thereon, and a plurality of stages of dynodes. It comprises an electrode 1d and one anode electrode 1a.

In normal use, a DC variable voltage source 2 applies a voltage that increases sequentially to the cathode electrode 1k and all dynode electrodes 1d through a plurality of voltage dividing resistors R connected in series. I'll keep it. When light enters the cathode electrode 1k, photoelectrons proportional to the amount of incident light are emitted from the cathode electrode 1k, so the photoelectrons are
2 for each collision with the dynode electrode 1d of each adjacent stage.
This increases the number of secondary electrons, which are finally captured by the anode electrode 1a. An output voltage proportional to the amount of incident light is obtained from a load resistor RL connected to this anode electrode 1a.

As described above, even when the amount of light incident on the cathode electrode 1k is small and the number of emitted photoelectrons is small, the amount of electrons captured by the anode electrode 1a is large, and the photomultiplier tube 1 has a high gain. Equipped with an amplification function. Then, by adjusting the voltage applied from the DC variable voltage source 2 to the voltage dividing resistor R, the multiplication factor can be set to 102 to 1011.
It is possible to significantly change the number of times.

(Configuration) As shown in FIG. 1, a variable voltage source 2
A photomultiplier tube 1 is used in which a voltage that increases sequentially is applied to all dynode electrodes 1d through a voltage dividing resistor R connected in series with the cathode electrode 1k of the photomultiplier tube 1. A photoelectric conversion element 4, such as a solar cell or a PIN photo diode, which converts incident light into an electrical signal is connected between the anode electrode 1a and the DC variable voltage source 2.
is connected to the input terminal of an operational amplifier 3 that converts current into voltage.

In addition to the incident light beam 13 to be converted into an electric signal, a first light source 11 supplies a constant amount of bias light beam 12 to the photoelectric conversion element 4 as a bias.
A second light source 11 such as a light emitting diode is provided which always irradiates a constant amount of light 14 to the cathode electrode 1k of the photomultiplier tube 1.

The output of the operational amplifier 3 is used for signal processing and is led to a peak detection circuit 8. The peak value output of the peak detection circuit 8 is compared with a reference voltage ref in a comparator circuit 9. The deviation is fed back to the DC variable voltage source 2 to form an automatic gain control system that adjusts the generated voltage.

When a photoelectric conversion device including the photomultiplier tube 1 and photoelectric conversion element 4 of the present invention is applied to, for example, a color thermometer, a solar cell or a PI that becomes the photoelectric conversion element 4 is used.
A rotary filter 6 is provided in the middle of the incident optical path to the N photodiode, which has two types of filters 6a and 6b with different passing wavelengths, λa and λb, and a light shielding part 6c that blocks the light beam, and is rotated by a motor 7. .

(Operation) When no light beam is incident on the photoelectric conversion element 4, no current is generated from the photoelectric conversion element 4. Even if a certain amount of light is incident, current cannot flow, so the cathode electrode is 1k.
It does not emit more photoelectrons.

However, when a light beam is incident on the photoelectric conversion element 4, a current proportional to the amount of the incident light is generated, and photoelectrons of the same amount as the generated current are emitted from the cathode electrode 1k of the photomultiplier tube 1. The photoelectrons emitted from the cathode electrode 1k are multiplied by the dynode electrodes 1d of each stage, then captured by the anode electrode 1a, and input into the operational amplifier 3 as a current.

At this time, the current generated from the anode electrode 1a of the photomultiplier tube 1 is proportional to the amount of light incident on the photoelectric conversion element 4, and is also proportional to the gain of the photomultiplier tube 1.

The gain of the photomultiplier tube 1 is determined by the voltage applied to the voltage dividing resistor R by adjusting the DC variable voltage source 2, that is,
By adjusting the voltage applied between the cathode electrode 1k and the dynode electrodes 1d of each stage, it is possible to significantly change the gain to 102 to 1011 times. Even if the voltage changes significantly, amplification can be achieved with an optimal gain by adjusting the voltage generated by the DC variable voltage source 2.

However, accurate signal processing cannot be performed unless the current generated from the anode electrode 1a of the photomultiplier tube 1 when the amount of light incident on the photoelectric conversion element 4 is zero is used as a reference value. The filter 6 is provided with a light shielding part 6c.

A rotary filter 6 having filters 6a and 6b that pass two wavelengths λa and λb and a light shielding part 6c.
When the light beam incident on the photoelectric conversion element 4 is changed, the impedance of the photoelectric conversion element 4 becomes extremely high when the light is blocked by the light shielding part 6c, and the impedance of the photoelectric conversion element 4 and the anode electrode 1a of the photomultiplier tube 1 are changed. Due to the remaining electrons, even if the amount of incident light changes as shown in A of FIG. 2, the waveform of the signal output from the anode electrode 1a of the photomultiplier tube 1 remains as shown in B of FIG. , and the responsiveness deteriorates significantly.

Therefore, if the first light source 5 always makes the bias light beam 12 of a constant amount of weak light enter the photoelectric conversion element 4, the photoelectric conversion element 4 will never be in a high impedance state. A waveform signal that follows changes in the amount of incident light can be obtained, and responsiveness can be improved.

[0019]

[Effect] As explained above, according to the photoelectric conversion device of the present invention, even if the amount of incident light changes significantly, the gain of the photomultiplier tube that operates as an amplifier can be changed significantly. It is possible to faithfully convert an incident light beam into an electrical signal while maintaining linearity, and by always allowing a bias light beam to enter the photoelectric conversion element, it improves responsiveness to sudden changes in the amount of incident light. can.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a photoelectric conversion device of the present invention.

FIG. 2 is a waveform diagram used to explain the operation of the photoelectric conversion device shown in FIG. 1;

FIG. 3 is a circuit diagram used to explain the technology underlying the photoelectric conversion device of the present invention.

[Explanation of symbols]

1 Photomultiplier tube 2 DC variable voltage source 3 Operational amplifier 4 Photoelectric conversion element 5 First light source 6 Rotating filter 7 Motor 11 Second light source 12 Bias ray 13 Incident ray

Claims (2)

[Claims] 1. A photomultiplier tube comprising a cathode electrode having a photocathode that emits photoelectrons corresponding to the amount of incident light, a plurality of stages of dynode electrodes, and an anode electrode; A voltage dividing resistor connected in series to apply voltage, a DC power source to apply a DC voltage to the voltage dividing resistor, and a photoelectric conversion element connected between the DC power source and the cathode electrode and into which the light beam to be converted is incident. , a first beam that makes a substantially constant bias beam incident on the photoelectric conversion element;
and a second light source that makes a substantially constant light beam incident on the cathode electrode of the photomultiplier tube, the current generated from the photoelectric conversion element is amplified by the anode electrode of the photomultiplier tube. A photoelectric conversion device characterized by deriving current as an electric current. 2. A variable DC voltage source is used as a DC power supply that applies a DC voltage to the voltage dividing resistor, and the gain of the photomultiplier tube is adjusted by changing the voltage generated by the variable DC voltage source. The photoelectric conversion device according to claim 1.