JPS5921490B2 - Light amount measurement circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for measuring light intensity suitable for measuring other light fluxes corresponding to a specific light flux, for example, light fluxes within a certain wavelength range. Regarding circuits.

Various measurements have been carried out to compare and measure two types of luminous flux.

A spectrophotometer or colorimeter uses a configuration that measures the reflected light flux from a standard white plate and a sample material, respectively, and calculates the ratio.
A two-color thermometer is configured to calculate the ratio of light amounts for two wavelengths out of the light flux emitted from the object.

In many of these devices, an optical chopper is used to split the two light beams, and the two light beams are compared in a time-division manner. The measurement method of comparing the luminous flux in a time-division manner using an optical chopper as described above is valid under the condition that the quality and quantity of light do not change for a certain period of time. Therefore, it is difficult to measure a luminous flux that has a relatively short duration or a luminous flux that changes rapidly. SUMMARY OF THE INVENTION An object of the present invention is to provide a light amount measuring circuit that can perform comparative measurements even with a light beam having a relatively short duration. In order to achieve the above object, the light amount measuring circuit according to the present invention has the following features:
A first integrating circuit that receives, photoelectrically converts, and integrates a first luminous flux; a second integrating circuit that receives, photoelectrically converts, and integrates a second luminous flux; and an output of the second integrating circuit. and a circuit that connects the output of the second integrating circuit to the display device when the voltage of the first integrating circuit reaches a certain level, It is configured as shown in C to measure the luminous flux.

According to the above configuration, it is possible to directly obtain the integral pupil of the second luminous flux at the time when the first luminous flux is integrated by a certain amount.
The luminous flux ratio can be determined immediately.

The circuit according to the present invention will be explained in more detail below with reference to the drawings and the like.

FIG. 1 is a circuit diagram showing an embodiment of a light amount measuring circuit according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the circuit shown in FIG.

In FIG. 1, Al is an amplifier for controlling the first integrating circuit, and a photoelectric conversion element (photodiode) PdA is connected to the differential input terminal.

An integrating capacitor CAI and a switch SAI are connected between one input terminal and an output terminal of the amplifier Al.
The second integration circuit is also constructed in the same way as the old PdB, B, CBI/S.

The amplifier B2 is an amplifier with an amplification factor of 1 in which 100% feedback is performed between the human outputs, and a holding capacitor CB2 is connected to one input terminal.

This capacitor CB2 is connected to the output terminal of the second integrating circuit via a switch S,2. The output of the first integrating circuit is also connected simultaneously to holding capacitors CA2, A2 and DISPA via switch SA2.

The output of the first integrating circuit is further connected to a comparison input terminal of a comparator COMP.

One input terminal of the comparator COMP is connected to the reference voltage r and generates an output when the output voltage of the first integrating circuit reaches Vr. The switch control circuit CONT receives the output of the comparator COMP and a start signal (Start).
is connected. When the start signal is applied, the switch control circuit CONT opens the six switches SAl and SBl, and starts the integration operations of the first and second integration circuits.

When the output A1 of the first integrating circuit reaches the reference voltage r and receives the output from the comparator COMP, the switch SA2,
SB2 is instantaneously closed. The comparator COMP, switch control circuit CONT, switch SB2, amplifier B2, capacitor C82, etc. form a circuit that connects the output of the second integrating circuit to the display device.

Next, the operation of the circuit having the above configuration will be further explained with reference to FIG.

In FIG. 2, the waveforms α and β respectively indicate the light beams incident on the first integrating circuit and the second integrating circuit, respectively.

The density of the luminous flux β is approximately 1/2 of the density of the luminous flux α.
At the time of TO, the start signal (Start) is switched to 1bi.
When applied to the leg circuit CONT, switches SAl, SB
l is opened, and the first and second integration circuits start photoelectric conversion and integration of the luminous fluxes α and β, respectively. The output VAl of the first integrator circuit and the output VBl of the second integrator circuit gradually rise, and when V1 reaches the voltage Vr at time t1, an output is generated in the comparator COMP, and the switch leg receives the output. The circuit CONT is closed by instantaneously closing 17 the switches SA2 and SB2. As a result, holding capacitor CA2
PCB2 is A! It is filled and held up to VBl. Each voltage is displayed by display elements DISPA and DISPB.

The reference voltage Vr is set as follows.

For example, if the luminous flux α is a luminous flux reflected from a standard white board, the reference voltage of the comparator is set to a voltage corresponding to the reference value.

If the reflectance of a standard white board can be 100%, set Vr = l volts, and let the luminous flux β be the reflected luminous flux from any surface to be measured, then the display voltage of DISPB will immediately become: The voltage indicating the reflectance of the arbitrary surface is, for example, 0.8, 0, 5, etc. At this time D
ISPA is displaying 1.0. If the reflectance of the standard white board is 0.98 or 0.97, if you set Vr = 0.98 volts or 0.97 volts, DISPB will similarly display the reflectance of the arbitrary surface. Can be displayed directly. The circuit according to the present invention can be similarly applied to a two-color thermometer, and a light source with fluctuations like a flame can also be measured.

The first wavelength component in the flame is taken out as an α beam, and the other wavelength components are taken out as a β beam. P
d, IIC, the β luminous flux component relative to the α luminous flux component can be immediately displayed. The wavelength transmission characteristics of a space where smoke or the like exists can also be measured in the same manner. In these cases, even if the intensity of the light source changes, no problem occurs because integration is performed using one as a reference. In either case, since the configuration is such that the other amount is displayed relative to the reference amount, the ratio can be determined without performing complex calculations within the circuit, such as division 6. Various modifications can be made to the embodiments described in detail above within the scope of the present invention. For example, the start signal can be applied to the control circuit CONT in synchronization with the turning on of the light source. Further, in order to facilitate understanding, each switch has been explained using a normal switch, but it is also possible to use a semiconductor switch.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a light 1 measuring circuit according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the circuit shown in FIG. PdA, Pd8...Photoelectric conversion element, CA[,
CBl... Integrating capacitor, SAl, SBl
,SA2,SB2゜lO switchTCA2夛CB2ll
Holding capacitor, Al, Bl... Integrating amplifier, A2, B2...゜゜・Holding amplifier, DISPA
, DISPB...Display element, COMP...
...Comparator, CONT'...Switch control circuit.

Claims (1)

[Claims] 1. A first integrating circuit that receives, photoelectrically converts, and integrates a first luminous flux, a second integrating circuit that receives, photoelectrically converts, and integrates a second luminous flux, and an output of the second integrating circuit. and a circuit that connects the output of the second integrating circuit to the display device when the voltage of the first integrating circuit reaches a certain level, A light intensity measurement circuit configured to measure luminous flux.