JPS6058816B2 - automatic brightness thermometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic brightness thermometer using a photodiode as a photoelectric conversion element.

In general, an automatic brightness thermometer is an automated optical pyrometer, but this automatic brightness thermometer replaces the human eye with a photoelectric conversion element to determine the brightness of the object to be measured and the comparison radiator. .

Conventional automatic brightness thermometers alternately guide the radiant energy of the object to be measured and the comparison radiator to the photoelectric conversion element via a rotating sector, so that the deviation in the brightness of the object to be measured and the comparison radiator becomes zero. Many of them automatically control the brightness of the comparison radiator. However, such a device using a rotating sector has a problem with its operating life because it employs a rotating mechanism. The present invention has been made in view of these points, and uses a photodiode with a high optical system gain instead of the above-mentioned rotating sector to provide the same effect as the rotating sector and to be stable even at low brightness. This is an automatic brightness thermometer that can provide output. Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 is an electrical connection diagram showing one embodiment of the present invention.

An optical system 1 composed of lenses, mirrors, etc. forms an optical image of an object to be measured X onto a photodiode D. Similarly, the optical image of the comparison radiator R is formed on the photodiode D2. As the comparison radiator R, for example, a tungsten light bulb is used. Here, photodiodes D and D.
It is necessary to have a set of characteristics. Recent advances in semiconductor manufacturing technology have made it easy to obtain photodiodes with uniform characteristics. The photoelectric conversion outputs of the photodiodes D and D2 are output from the switches SW and SW.

The signal is inputted to the first integrator 2 and the second integrator 3 via. The first integrator/divider 2 includes an operational amplifier 20 and a capacitor C.
1 and a switch SW3. A capacitor Cl is connected between the input and output terminals of the operational amplifier 20, and a switch SWa is connected to both ends of the capacitor Cl. Like the first integrator 2, the second integrator 3 also includes an operational amplifier 30, a capacitor Co, and a switch SW. It is made up of. 5 is a comparator that compares the output signal of the first integrator 2 and the reference voltage s.

A hold circuit 4 holds the output of the second integrator 3 using the output of the comparator 5.

Reference numeral 6 denotes an amplifier that amplifies the difference between the output of the hold circuit 4 and the reference voltage s.

Reference numeral 7 designates a first control circuit that receives the outputs of the comparator 5 and the pulse generator 8 and controls the on/off of the switches SW1 to SW4.

Reference numeral 9 denotes a second control circuit that receives the output of the amplifier 6 and drives the comparison radiator R.

10 is a temperature conversion circuit that receives the output of the control circuit 9 and converts it into a corresponding temperature signal.

11 is an output terminal for taking out the output of the temperature conversion circuit 10 to the outside.

The operation of the circuit configured in this way will be explained below. When an optical image of the object to be measured X is formed on the photodiode D1 via the optical system 1, a photocurrent corresponding to the radiant energy of the object to be measured X flows through the photodiode.

Furthermore, since the radiant energy changes exponentially with the temperature of the radiation source, the photocurrent of the photodiode changes significantly. Therefore, it is necessary to perform automatic gain control on the circuit that receives the photocurrent of the photodiode. Assuming that the switch SWl is now closed, the photocurrent of the photodiode D1 is input to the integrator 2.

Here, the switches SW1 and SW3 are connected to the period T of the output of the pulse generator 8 as shown in FIG. 2a. It is turned on and off by the output of the first control circuit 7 which is synchronized with . Figure 2b shows switch SWl and C shows switch SW3 on and off.
FIG. 3 is a diagram showing off characteristics. In these characteristic diagrams, the ゛゜1゛ level corresponds to switch-on, and the 460 level corresponds to switch-off. In Figure 2b, Ts
Sui. This shows the period during which the switch SWl is on. FIG. 2d shows the output waveform of the integrator 2 controlled by the switches SWl and SW3. Switch SWl
is on, the switch SW3 is off, and the photocurrent of the photodiode D1 is integrated by the integrator J2. The output of the integrator 2 gradually increases in the negative direction as shown in the figure. The output of this integrator 2 is connected to one input of the following comparator 5. The moment the output of the integrator 2 reaches upper s, the output of the comparator 5 is inverted. FIG. 2e shows the comparator 5
The first control circuit 7 turns off the switch SWl and turns on the switch SW3 after a certain period of time. When the switch SW3 is turned on, the integrator 2 is reset and therefore comparator 5
The output also returns to the state before the change. Here, switch SWl
The period during which Ts is closed is inversely proportional to the magnitude of the radiant energy from the object to be measured. That is, when the radiant energy is large, the period Ts becomes short, and when the radiant energy is small, the period Ts becomes long. That is, the circuit composed of the photodiode D1, the switch SWl, the integrator 2, the comparator 5, and the first control circuit 7 is configured so that the final integrated photocurrent output of the integrator 2 is always equal to the reference voltage s. This constitutes an automatic gain control circuit in which the integration time Ts is varied. That is, it shows that stable operation can be performed even in the case of low luminance. On the other hand, switches SW2 and S
W4 also performs on/off operations in synchronization with the switches SW1 and SW3, respectively.

The second f is a diagram showing the operation of the switch SW2, and the second g is a diagram showing the operation of the switch SW4. The second integrator 3 integrates the photocurrent of the photodiode D2 which has received the radiation energy of the comparison radiator R during the above-mentioned period Ts. 2 is a diagram showing the output waveform of the second integrator 3.The final output of the second integrator 3 is held in the hold circuit 4 by the signal from the comparator 5. amplifier 6
sends a signal to the second control circuit 9 so that the deviation between the output of the hold circuit and the reference voltage -Es becomes zero. FIG. 2 is a diagram showing how the output of the hold circuit 4 approaches the reference voltage s. The second control circuit 9 receives the output of the amplifier 6 and drives the comparison radiator R so that the reference voltage s becomes equal to the output of the hold circuit 4.

Then, when the reference voltage s becomes equal to the output of the hold circuit 4, the radiant energy of the object to be measured X and the comparison radiator R correspond to each other. The temperature conversion circuit 10 receives the output of the second control circuit 9, converts it into a signal corresponding to the temperature, and outputs the signal to the output terminal 11. In this way, a signal output corresponding to the temperature is generated at the output terminal 11, and it can be used as a brightness thermometer. Furthermore, since all of the above operations are performed automatically, it can be used as an automatic brightness thermometer. As described above in detail, according to the present invention, it is possible to realize an automatic brightness thermometer that does not use a mechanical part such as a rotating sector and can provide a stable output even at low brightness.

[Brief explanation of the drawing]

FIG. 1 is an electrical connection diagram showing one embodiment of the present invention, and FIG.
This figure is a diagram showing operating waveforms of each part of the circuit diagram shown in FIG. 1. 1...Optical system, 2, 3...Integrator, 4...
...Hold circuit, 5...Comparator, 6.
...Amplifier, 8...Pulse generator, 7,9...
...control circuit, 10 ...temperature conversion circuit,
11... Output terminal, 20, 30... Operational amplifier, SWl to SW4... Switch, Dl, D2
...Photodiode, upper S...Reference power supply, X
...Measurement object, R...Comparison radiator.

Claims (1)

[Claims] 1. Two photodiodes, an optical system that guides the radiant energy from the object to be measured and the comparison radiator to the two photodiodes, two integrators that integrate the output current of each of the photodiodes, and a device to be measured. a comparator for comparing an integrator output signal on the photodiode side corresponding to the object with a reference signal; a circuit for controlling the integration time of the two integrators based on the comparator output signal; a circuit that controls the radiant energy of the comparison radiator so that the deviation between the integrator output signal on the photodiode side and the reference signal becomes zero; and a circuit that converts the control signal of the comparison radiator into a signal corresponding to temperature. An automatic brightness thermometer consisting of a circuit.