JPH0410573B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention is based on the fact that the luminance distribution for each wavelength of light radiated from a black body at a certain temperature differs depending on the temperature of the black body according to the Wynn-Blank law. Detects the ratio of brightness in the wavelength range of
Regarding a color thermometer that determines temperature by the ratio,
In particular, the division circuit for obtaining the ratio is constructed from a D/A converter, a counting circuit, and the like.

As shown in FIG.
Rotary filter 1 with seed filters 1A, 1B
The optical system includes an optical system that allows the light to enter the photoelectric conversion element 2 through the .

This rotary filter 1 is rotated by a motor 5, and a two-phase alternating current generator 6 is connected to the motor 5 in addition to the rotary filter 1.

Furthermore, using the output of the two-phase alternating current generator 6,
A separation circuit 3 separates the electrical output of the photoelectric conversion element 2 into two outputs corresponding to the brightness of the wavelength component of the light beam that has passed through the two types of filters 1A and 1B, and each separated output is converted into a DC signal. rectifier circuits 4A, 4B, and these two rectifier circuits 4A, 4B.
The present invention includes a division circuit 10 for obtaining the ratio of the outputs of , and an indicator 20 for indicating the ratio output of the division circuit 10 .

As shown in FIG. 2, the division circuit 10 includes two input terminals 10A and 10B, one terminal 10B connected to a reference voltage terminal (ref), and a D/A converter 11 having a digital input terminal. , a linearization correction circuit 30 connected to both terminals 10A and 10B, a subtraction circuit 14 that obtains the difference between the analog output of the D/A converter 11 and the output of the linearization correction circuit 30, and this subtraction An absolute value amplifier 15 that obtains the absolute value of the output of the circuit 14, a variable frequency oscillator 12 whose oscillation frequency changes depending on the output of the absolute value amplifier 15, and a variable frequency oscillator 12 that counts the output of this oscillator 12 and converts the counted value into a digital signal. It is composed of an up/down counter 13 that outputs an output, and a polarity discrimination circuit 16 that discriminates the polarity of the output of the subtraction circuit 14 and instructs the counting direction of the counter 13.

Furthermore, the output terminal of the digital signal of the counter 13 is connected to the address input terminal, and the ROM 17 outputs the color temperature value expressed in a 4-digit decimal number, and the temperature value stored in each address of this ROM 17 is instructed. A four-digit indicator 20 is provided.

As shown in FIG. 5, the linearization correction circuit 30 includes a first analog switch 31 connected between one input terminal 10A and an output terminal 39.
a, 31b...31n and the first resistor 32a,
32b...32n, and second analog switches 33a, 33b...3 connected between the other input terminal 10B and the output terminal 39.
3n and second resistors 34a, 34b...34n
The first and second analog switches, which operate in pairs, are each closed by the output of the upper two digits of the ROM 17, and the output terminal 39 is ,
The subtraction circuit 14 along with the output of the D/A conversion converter 11
It is connected to the.

As shown by the dotted line X in FIG. 4, the ROM 17 stores in advance a correspondence table in which the color temperature display signal read out by the digital signal applied to the address terminal linearly corresponds to the digital signal. ing.

Next, the operation of the color thermometer of the present invention configured as described above will be explained.

When the light beam 8 radiated from the object to be measured 7 passes through the rotary filter 1 and enters the photoelectric conversion element 2,
From the photoelectric conversion element 2, an output with a waveform shown in FIG.
Two types of filters 1 are created using the output of the phase alternating current generator 6.
When separated into two outputs (A, B in Fig. 3) with peak values a and b corresponding to the brightness of the wavelength components that have passed through A and 1B, and converted to DC by rectifier circuits 4A and 4B, the peak values a and b are It is possible to obtain two DC voltages corresponding to .

These two DC voltages are each divided by the divider circuit 1
0 to two input terminals 10A and 10B.

The D/A converter 11 outputs an analog output V X proportional to the product of the voltage V _B applied to the reference voltage terminal (ref) and the digital signal V _D applied to the digital _{input terminal, that is, V X =} Since it generates an analog output of V _B・V _D ……(1), the subtraction circuit 14
, this analog output V _X and input terminal 10
The voltage _V A applied to A and 10B and processed by the linearization correction circuit 30 is compared to obtain a differential voltage between the two, V _S =S _X ~V _A (2).

This differential voltage V _S is applied to the absolute value amplifier 15 and amplified, and then drives the variable frequency oscillator 12 to obtain an oscillation output with a frequency proportional to the absolute value of the differential voltage V _{S .} is also applied to the polarity determining circuit 16 to determine its polarity.

The oscillation output of the variable frequency oscillator 12 is applied to the up/down counter 13 together with the output of the polarity discrimination circuit 16, and the variable frequency oscillator 1 is applied in the up or down direction according to the output of the polarity discrimination circuit 16.
The oscillation output of 2 is counted and the counted value is led to the D/A converter 11 and ROM 17.

Then, when the count value of this counter 13 becomes equal to _the analog output _V
Since the output of the oscillator 12 ceases, the oscillation of the oscillator 12 stops, and the counter 13 continues to hold the count value up to that point.

Note that the count value V _D of the counter 13 at the start of operation is an indefinite value unless it is cleared, but no matter what indefinite value it starts from, it will reach V _B · V _D − V _A = 0. The oscillation operation of the variable frequency oscillator 12 and the counting operation of the counter 13 are performed until the point is reached, and each operation is stopped when the point is reached.

At this time, the count value held in the counter 13
From the above formula (1), V _D becomes V _D = V _X / V _B ... (3), and since V _X = V _A , V _D = V _A / V _B ... (4) is obtained. and the analog voltage V _B applied to the input terminal 10B and the analog voltage V B applied to the input terminals 10A and 10B,
The ratio V _A /V _B to the analog voltage V _A processed by the linearization correction circuit 30 can be obtained as a digital signal.

On the other hand, the ROM 17 stores a correspondence table between the digital signal representing the ratio and the color temperature, so by addressing with the digital signal representing the ratio, the color temperature is output and the indicator 20 is used to indicate it. It is.

It would be convenient if the color temperature of the object to be measured 7 corresponds linearly with the digital signal, as shown by the dotted line X in FIG. Based on the characteristics, a relationship as shown by the solid line Y in FIG. 4 is exhibited.

Therefore, the linearization correction circuit 30 corrects the relationship between the digital signal and the color temperature, indicated by the solid line Y in FIG. 4, to the linear shape indicated by the dotted line X in FIG.

In other words, the 4-digit 10 is output from the ROM17.
One pair of analog switches of the linearization correction circuit 30 is closed by the signal of the upper two digits of the color temperature value expressed in base numbers, and the signal applied to the input terminal 10A is The signal applied to the input terminal 10B is guided to the output terminal 39 via the first resistor, and the signal applied to the input terminal 10B is guided to the output terminal 39 via the second resistor, and both are added.

At this time, the first resistor is used to adjust the gain by changing the amount of attenuation, and operates to change the slope (P-Q) to the slope (P-R) as shown in Figure 4. , the second resistor operates to translate the condition changed to slope (P-R) to slope (T-Q').

That is, the input voltage Va applied to the linearization correction circuit 30 from the terminals 10A and 10B
and Vb are weighted and added by the first resistors 32a to 32n and the second resistors 34a to 34n to generate an output voltage of A.Va+B.Vb (5). And the division circuit 10
When this output voltage is divided by the input voltage Vb, it becomes (A.Va+B.Vb)/Vb, and when this formula is transformed, it becomes A(Va/Vb)+B...(6).

The constant A is set by the first resistors 32a to 32n, and the constant B is set by the second resistors 34a to 34n.

In this way, for example, by adjusting the slope and deviation of the first and second resistors for each temperature range divided by 100°C,
Even with the correspondence table uniformly stored in the ROM 17, it is possible to change the characteristic shown by the solid line Y in FIG. 4 to the characteristic shown by the dotted line X, that is, linearize it.

As explained above, according to the color thermometer of the present invention, just by using one D/A converter, two
It is possible to obtain the ratio of two analog signals and at the same time obtain the digital value of that ratio.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the color thermometer of the present invention, FIG. 2 is a circuit diagram of a dividing circuit which is a main part of the device shown in FIG. 1, and FIG. Figure 4 is a waveform diagram used to explain the operation of the device; Figure 4 is a characteristic curve diagram used to explain the linearization operation; Figure 5 is a linearization correction used in the division circuit in Figure 2. It is a circuit diagram of a circuit. 1... Rotating filter, 2... Photoelectric conversion element, 3
... Separation circuit, 4A, 4B ... Rectifier circuit, 10...
...Division circuit, 11... D/A converter, 12... Oscillator, 13... Up/down counter, 14
... Subtraction circuit, 17 ... ROM, 20 ... Indicator, 30 ... Linearization correction circuit.

Claims (1)

[Claims] 1. 2. Included in the light rays radiated from the object to be measured.
means for obtaining first and second electrical signals corresponding to the luminance of two wavelength components; a rise correction circuit; and a division circuit that obtains a ratio between the second electrical signal and the output of the linearization correction circuit; the division circuit includes a variable frequency oscillator; It has an up-down counter for counting output, a reference voltage input terminal to which the second electric signal is applied, and a digital input terminal to which the digital output of the up-down counter is applied, and the second electric signal has an up-down counter. A D/A that outputs an analog voltage corresponding to the product of the electrical signal and the above digital output.
The variable frequency oscillator is equipped with a converter and a subtraction circuit that compares the output of the linearization correction circuit with the analog voltage and outputs the difference between the two, and the variable frequency oscillator calculates the absolute value of the difference until the absolute value of the difference becomes zero. The up-down counter performs counting operation by oscillating at a frequency proportional to the value, and the digital output of the up-down counter controls the first resistor and the second resistor in the linearization correction circuit. A color thermometer characterized by controlling each resistance value of a resistor and making the counted value correspond to a color temperature.