JPS5921492B2 - Light amount measurement circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light amount measurement circuit, and more specifically, a light amount measurement circuit for measuring the reflected light or transmitted light of an object to measure the characteristics of the object, or for measuring the luminous flux from a light source. Regarding circuits.

When measuring the amount of light as described above, it is necessary to calculate the relationship between two types of light fluxes.

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.Also, a two-color thermometer uses These devices are configured to calculate the ratio of two amounts of light from the emitted light flux (・), and these devices use an optical chopper to split the two light beams (・, time-divisionally). 2
By adopting a configuration that compares two luminous fluxes,
. Also, the circuit was relatively large. SUMMARY OF THE INVENTION An object of the present invention is to provide a light amount measuring circuit that can display the relationship between two types of light fluxes by using a pair of light flux integrating circuits and processing their integral values. In order to achieve the above object, the light amount measuring circuit according to the present invention includes a first integrating circuit that photoelectrically converts and integrates a first luminous flux, and a second integrating circuit that photoelectrically converts and integrates a second luminous flux. , a control circuit for defining integration periods of the first and second integrating circuits, an arithmetic circuit for processing integration results of the first and second integrating circuits, and displaying the arithmetic results of the arithmetic circuits. The display device is configured to calculate and display the relationship between two types of light beams.

According to the above configuration, the object of the present invention can be completely achieved.

The light amount measuring circuit according to the present invention will be explained in more detail below with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of the light amount measuring circuit according to the present invention.

In this embodiment, the control circuit activates the first and second integrating circuits simultaneously, and calculates the time ratio by dividing the time required for each integrated voltage to reach a common constant voltage. This is intended to determine the amount of light of the second beam relative to the first beam.

In the figure, Pdl is a photoelectric element (for example, a photodiode) arranged to receive the first beam α, and Pd is a photodiode arranged to receive the second beam β. .

The first integrating circuit includes a photodiode Pdl, and an amplifier A to which the photodiode Pdl is connected to a differential input terminal.
1. It consists of a capacitor C1 connected between the input and output terminals of the amplifier A1 and forming a feedback circuit.
An integral control switch S1 is connected in parallel to the capacitor C1.

The second integrating circuit is similarly composed of a photodiode Pd2, an amplifier A2, and a capacitor C2.
An integral control switch S2 is connected in parallel.

The output of each integrating circuit is connected to one input terminal of comparators COMP1 and COMP2, respectively. ing.

The other input terminals of COMP1 and COMP2 are connected to a reference voltage point Ref, and are configured to generate an output when the output of each integrating circuit reaches Vref. Gate G is a gate that opens with a signal from the control circuit CONT and closes with a signal from COMPl.
Send to OUNTl.

Gate G2 opens with a signal from control circuit CONT, and CO
It is a gate that closes with the signal of MP2, and while it is open, the pulse from the oscillator 0SC is sent to the counter COUNT2.
Send to.

The oscillator 0SC is a precisely controlled equally spaced pulse, which is connected to a counter COUNTl and a counter COUNTl.
The count number of 2 is proportional to the open time of gates Gl and G2.

The output of each counter is connected to an arithmetic circuit Ar, and the arithmetic circuit calculates the result of dividing the count number of COUNT2 by the count number of COUNT1.

DISP is a display device for displaying the calculation results.

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

In FIG. 2, (α, β) indicates temporal changes in the luminous flux α and the luminous flux β.

In this example, the density of the luminous flux α is about twice as large as that of β. When the circuit is started at time T, the control circuit CO
NT switches the first and second integrating circuits S,
, S2 is opened. As a result, the output voltages of the first and second integrating circuits each start to rise as shown in FIG. 2 (, , V2). The density of the luminous flux α is larger than that of β
・The slope for cause is larger.

At the same time that Sl and S2 are opened, gates Gl and G2 are also opened by the output of the control circuit CONT, allowing the oscillation pulse of the oscillator 0SC to pass through.

When the output voltage V1 of the first integrating circuit reaches Vref (time T2), the output of COMP1 is applied to the gate G1, closing the gate G1.

At this point, gate G2 is still open (・te℃・ru. Time T3
When the output voltage V2 of the second integrating circuit reaches Vref, the gate q closes. When the count number of the counter COUNTl is n1 and the count number of the counter COUNT2 is N2, the arithmetic circuit Ar'('N2/N) is calculated, and the result of the arithmetic operation is displayed on the display device.

FIG. 3 is a circuit diagram showing a second embodiment of the light amount measuring circuit according to the present invention.

゛In this embodiment, the first and second integrating circuits are started simultaneously by the control circuit, and after operating for a certain period of time, the voltage ratio of each integrated voltage is calculated and displayed by the analog calculation circuit. It is.

The first integration circuit includes Pdl, Al, and Cl, and the integration period is regulated by switch S1.

The second integration circuit includes Pd2, A2, and C2, and the integration period is regulated by switch S2. Switches S3 and S4 are for holding and connecting. Amplifier A3 is an amplifier with an amplification factor of 1, and is connected to one input terminal, and outputs the voltage at the terminal of the holding capacitor C3, which is exactly multiplied by one.

There is a variable resistor VR2 at the output terminal of 3A3.
is connected as a load. One terminal of the variable resistor VR, is connected to the constant voltage source E, and R,,VR2
The voltage dividing terminals of motor M
It is moved by h Capacitor C4 and amplifier A4 form a holding circuit for the output voltage of the second integrating circuit. At the output terminal of amplifier M,
A series circuit of resistors R1 and R2 is connected as a load (・
Ru. The voltage dividing terminal of R and the connection point of resistors R1 and R2 are connected to the input terminal of a comparator COMP, and the output of the comparator COMP is a motor drive circuit MD capable of driving the motor M in forward and reverse directions. It is connected to L.

When the motor M rotates in the forward and reverse directions, the voltage dividing terminals of the variable resistors VRl and VR2 are raised and lowered, and the divided voltage of VRl changes in an analog manner and is displayed on the display device DISP. VR2-C
OMP-MD-M-R2 forms a negative feedback loop, and when the voltage at the divided voltage terminal of R2 becomes equal to 4R2/(R, +R2), the motor M stops, and the voltage dividing ratio at that time Two voltages corresponding to will be displayed by DISP. The control circuit CONT includes the switches S, S2,
In addition to controlling the order of S3 and S4, the motor. This is a control circuit that determines the operation period of the drive circuit MD and the display start timing of the display device DISP. Next, the function and operation of the circuit having the above configuration will be explained in more detail with reference to FIG.

In Fig. 4, L・te (α, β) are photodiodes Pd, ,
Change in the luminous flux incident on Pd2, (Sl, S2) is the operation of the integrating leg switch, (Vl, V2) is the change in the output voltage of the first and second integrating circuits, (S3, S4) is the connection switch S3 , S4 operation, (3, V4) is the holding amplifier A
3. The output voltage of A4 (MD) indicates the operating period of the motor 1 drive circuit.

At time t1, 匍? The circuit CONT causes switches Sl,
When S2 is turned off, the first and second integrating circuits each start integrating, and the integrated voltage gradually increases. After a certain period of time has elapsed, at time T2, the control circuit CONT instantaneously turns on the holding connection switches S3 and S4, and the voltages V, V2 at that time appear at the outputs of the holding amplifiers A3 and A4 and are held (the (See Figure 4 V3 and V4).

After that, from time T3 to T4, the motor drive
D operates, the output terminals of VR, , VR2 are moved, and an analog equilibrium state is formed.

That is, by analog calculation, a voltage corresponding to the ratio of V3 and V4 appears at the output terminal of VRl, and that voltage is then applied to the display device DIS by the control signal of the control circuit.
Displayed by P. In this embodiment, the feedback circuit described above forms an analog arithmetic circuit. FIG. 5 is a circuit diagram showing a third embodiment of the light amount measuring circuit according to the present invention.

In this embodiment, the luminous flux density of the luminous flux incident on the photoelectric conversion element of the first integrating circuit is larger than the luminous flux density of the luminous flux incident on the photoelectric conversion element of the second integrating circuit L.
The conditions (α>β) are set.

However, if (β>α), it is sufficient to replace the luminous flux.
Then, the control circuit activates the first and second integrating circuits simultaneously until the voltage of the second integrating circuit becomes equal to the integrated voltage when the first integrating circuit performs unit time integration. Find the second integration time.

Then, the difference between the second integral time and the unit time is calculated and displayed on the display device.

According to this configuration, by rationally selecting the zero digit of the display device and the unit time, the density of the luminous flux α can be determined as a percentage of β.
It is possible to display a large L.

In FIG. 5, the first integrating circuit for integrating the light beam α at L is formed by a photodiode Pdl, an amplifier A1, and a condenser C1, and the integration is started by opening a switch S. Similarly, the second integrating circuit that integrates the luminous flux β is Pd2,
A2 and C2 are formed, and the integration is started by opening the switch S2. Switch S3 is switch Sl,
This is a hold/connection switch that is instantaneously closed after a certain period of time has passed after S2 is opened.

The capacitor C3 is a holding capacitor, and the amplifier A3 is a holding amplifier with an amplification of 1 that outputs the voltage of the capacitor C3.

The output of this amplifier A3 is connected to the reference voltage input terminal of the comparator COMP. The output of the second integrating circuit is connected to the other input terminal of COMP, and the integrated voltage V2 of the second integrating circuit is equal to the holding voltage 3 of the amplifier A3.
Generates output when . Gate G.

, and G are gates for transmitting the reference time pulse of the oscillator CK (or 0SC) to the arithmetic circuit Ar.
Gate G. 、． Gl is controlled by the converter circuit CONT to open at the time T, when the switches S1 and S2 are opened, and the gate GO is closed at the time T2 when the switch S, is turned on. Gate G1 closes at the time T3 of occurrence of the output of said COMP. The oscillator 0SC oscillates a pulse train at regular intervals, and the pulse frequency varies from time T to T.
Up to 2, 10n (n: an integer of at least 2), for example 1000, are generated in a fixed period of time.

In order to facilitate understanding, 1000 pieces will be explained below as an example. The time from time t1 to T2, hereinafter the unit time is:
It may be considered as a time interval during which 1000 pulses are generated.

Each counter G.

, G, are input to an arithmetic circuit Ar, where the count number N, of G1 and G. Count number N. (NO
<N,) is calculated, and the result is displayed on the display device DIS
Displayed as P. By selecting the digit position of the display device DISP, it is possible to directly display what percentage the density of the luminous flux α is greater than the density of the luminous flux β. Next, the reason will be briefly explained.

If the output voltage of the first integrating circuit when the luminous flux α is integrated from time t1 to T2 (unit time) is V, (=V3), it is proportional to α between three single positions, so V3=αK(T2-t
1)・・・・・・・・・・・・・・・・・・1. 'K
:Constant Next, the time (T3-t1) until the output voltage of the second integrating circuit reaches the above-mentioned V3 is determined by the following equation.

32βK (T3-t1)・・・・・・・・・・・・
...2 From equation 12 above, (T3-T,) and (T, -
The following three equations are given by calculating the time difference between T, )';

VV(Trt,)-(T2-t1)="-"...
・・・・・・・・・3βKaK Divide the above equation by (T2-T,). In equation 4, T3-T, is proportional to N, and T2-t1
is N.

Since it is proportional to , the following equation can be obtained by transforming equation 4. 16
υ R The right side of equation 5 shows how many degrees Celsius the α luminous flux is compared to the β luminous flux.

The numerator on the left side is calculated by the arithmetic circuit Ar shown in FIG.
N is the denominator. is 1000 in this example, and is given on the display device side as the scale of the digit of the display device, so there is no need to actually calculate it (゛.NO=1000, n1=120
If it is 0, then it becomes N,-NO2200, and if the 0 digit of the display device is between the last 3 and 4 digits, the display will be 0.2, indicating that the α luminous flux is 20% more than the β luminous flux. be done.

The control circuit CONT is connected to the opening point Tl of the switches S, , S2.
, s3.

And as a clock for these time controls, an oscillator 0SC
The oscillation output is supplied to CONT. Next, the function and operation of the light amount measuring circuit having the above configuration will be explained with reference to FIG.

In FIG. 6, (α, β) shows the temporal change in the light flux to be measured, (Sl, S2) shows the operation of the integral control switch, and S shows the operation of the hold/connect switch. (1,
V2, 3) indicate the output voltages of the first integrating circuit, the second integrating circuit, and the holding circuit, respectively.

GO and GI indicate the opening time of each gate. At time T, the switches S, , S2 are opened by the control circuit CONT, and the gate G is opened.

, Gl is opened. As shown in FIG. 6 (Vl, 2, V,), the output voltage V, of the first integrating circuit is larger than V2. The control circuit CONT outputs 1000 pulses from 0SC.
At the moment when the unit is received, switch S3 is instantaneously closed, and gate G is closed. Close. By closing switch S3,
Capacitor C3 is charged to voltage 1 (=3) at time T, and the output of amplifier A3 becomes 3. The output voltage V, of the amplifier A2 gradually increases, and when this voltage V, is reached, the comparator COMP generates an output and closes the gate G1. Gate G. Pulse N passed through. Pulse N that passed through G1
, the difference is calculated in the arithmetic circuit Ar, and the difference is displayed on the display device DISP.
It was established as a sect. As described above, this display directly indicates how many percentage points the density of the α-luminous flux is greater than the density of the β-luminous flux. In this example, when the difference is calculated, (αβ)/β can be calculated with a simple calculation.As explained in detail above, according to the present invention, two types of luminous fluxes are integrated, and the integral value is The relationship between these luminous fluxes can be displayed by calculating the following method.

Furthermore, since both luminous fluxes are integrated, sufficient sensitivity can be obtained by adjusting the measurement time.

Conversely, short-time photometry is also possible when a sufficient amount of light is available. Furthermore, since the entire device can be formed from a semiconductor circuit, the device can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of a photometric circuit according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the circuit shown in FIG. 1, and FIG. 3 is a photometric circuit according to the present invention. 4 is a waveform diagram for explaining the operation of the circuit shown in FIG. 3, and FIG. 5 is a circuit diagram showing a third embodiment of the photometric circuit according to the present invention. 6 are waveform diagrams for explaining the operation of the circuit shown in FIG. 5. Pdl, Pd2...Photoelectric element (photodiode), A
l, A2... Integrating differential amplifier, A3, A4... Holding amplifier, Cl, C2... Integrating capacitor, C3,
C4... Holding capacitor, Sl, S2... Integral control switch, S3, S4... Holding connection switch, CO
MPl, COMP2, COMP... Comparator, GO, G
,,G2...gate, 0SC(CK)...oscillator,
COUNTl, COUNT2... Counter, Ar...
・Arithmetic circuit, DISP...display device, CONT...
Sequential control circuit, VRl, VR2...variable resistor, Rl
, R2...Resistance, MD...Motor control circuit, M...
·motor.

Claims (1)

[Scope of Claims] 1. A first integrating circuit that photoelectrically converts and integrates a first luminous flux; a second integrating circuit that photoelectrically converts and integrates a second luminous flux; Two types of circuits each consisting of a control circuit for defining the integration period of the integrating circuit, an arithmetic circuit for processing the integration results of the first and second integrating circuits, and a display device for displaying the arithmetic results of the arithmetic circuit. A light amount measurement circuit that calculates and displays the relationship between the luminous fluxes. 2. The first and second integrating circuits are caused to start integration at the same time by the control circuit, and the time required for each to reach a common constant voltage is divided by the arithmetic circuit to obtain a time ratio; 2. The light amount measuring circuit according to claim 1, wherein the time ratio is displayed by the display device. 3. The first and second integrating circuits are caused to simultaneously start integration by the control circuit, and after a certain period of time has elapsed, the voltage ratio of the respective integrated voltages is calculated by an arithmetic circuit using analog processing. 2. The light amount measuring circuit according to claim 1, wherein the light amount measuring circuit is configured to display the voltage ratio on the display device. 4. Under the condition that the luminous flux density of the luminous flux incident on the photoelectric conversion element of the first integrating circuit is greater than the luminous flux density of the luminous flux incident on the photoelectric conversion element of the second integrating circuit, the control circuit and a second integration circuit to start integration at the same time, and find a second integration time until the second integration voltage becomes equal to the integration voltage when the first integration circuit performs unit time integration; The arithmetic circuit causes the second
2. The light amount measuring circuit according to claim 1, configured to calculate the difference between the integral time and the unit time and display the difference on the display device.