JPS59192924A - Color temperature gauge - Google Patents

Abstract

PURPOSE:To obtain the ratio of two analog signals only by use of one A/D converter and also to obtain the digital value of the ratio by using a dividing circuit which consists of the A/D converter and a counting circuit. CONSTITUTION:The oscillation output of a variable frequency oscillator 12 is applied to an up/down counter 13 together with the output of a polarity deciding circuit 16 to count the oscillation output according to the output of the circuit 16, and the counted value is led to a D/A converter 11 and an ROM17. The counter 13 holds the current counted value VD when an analog output VX converted on the basis of a voltage VB applied to a reference voltage terminal ref becomes equal to the output VA of a linearization correcting circuit 30. In this case, VD=VX/VB, so VD=VA/VB because VX=VA, thereby obtaining the ratio VA/VB. On the other hand, a correspondence table containing digital signals showing ratios and color temperatures is stored in the ROM17, so a signal is used for address assignment to output the corresponding color temperature, which is indicated on an indicator 20.

Description

Detailed Description of the Invention This invention is based on the fact that the brightness distribution of the wavelength of light radiated from a black body at a certain temperature differs depending on the temperature of the black body according to Lye/Blank's law. Regarding a color thermometer that detects the ratio of brightness in different wavelength ranges and determines the temperature based on the ratio, in particular, the division circuit that obtains the ratio is D/
It consists of an A converter, a counting circuit, etc.

As shown in Fig. 1, the light beam (8) radiated from the object to be measured (7) is passed through a light receiving lens (9), and a rotating filter (IA) and (IB) having two types of filters (IA) and (IB) with different passing wavelengths.
The optical system includes an optical system that causes the light to enter the light conversion element (2) through the light source (1).

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

Furthermore, a rectifier circuit (4A) converts the electrical output of the photoelectric conversion element (2) into a DC signal by converting each of the two filtered outputs into DC signals, using the output of the two-phase AC generator (6).
4B), a division circuit 0I that obtains the ratio of the outputs of these two rectifier circuits (4A) and (4B), and an indicator (A) that indicates the ratio output of this division circuit 00. .

The division circuit (10, as shown in FIG.
B) is connected to the reference voltage terminal (ref), and the D/A converter α has a digital input terminal; a subtraction circuit 04) that obtains the difference between the analog output of the D/A converter U and the output of the correction circuit for nearization (7), and an absolute value amplifier that obtains the absolute value of the output of this subtraction circuit CL4). α uniform, a variable frequency oscillator 1μ whose oscillation frequency changes depending on the output of this absolute value amplifier αυ, and this oscillation! The polarity of the output of the up/down counter (which counts the output of 12 and outputs the counted value as a digital signal and the subtraction circuit 04) is determined, and the output of the counter (13) is determined.
It is composed of a sex discrimination circuit 0 which instructs the direction of counting.

Furthermore, the digital signal output terminal of the counter (1'3) is connected to the address input terminal, and the ROM (L71 and this RO
4 Instructing the temperature value stored in each address of MQ71
It is equipped with a digit indicator (1).

As shown in FIG. 5, the linearization correction circuit (7) includes first analog switches (3ta) and (31b) connected between one input terminal (IOA) and the output terminal -.
)'--(31n) and the first resistor (32a).

(32b) ...... (32n) and a second analog switch (33a), (33
b)......(33n) and the second resistor (
34a), (34b) ... --= (34n), and each of the first and second analog switches that operate in pairs is The output terminal (G) is connected to the subtraction circuit 04) together with the output of the R/A conversion converter θ.

The ROM (17) has a correspondence table in which the color temperature display signal read out by the digital signal applied to the address terminal corresponds linearly to the digital signal, as shown by the dotted line (X) in Figure 4. It is stored in advance.

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) enters the photoelectric conversion element (2) through the rotating filter (1), the photoelectric conversion embryo (2) passes through the rotating filter (1). Since the output of the waveform shown in Fig. 3C corresponding to the brightness of the passing light beam is obtained, it is processed by two types of filters ( LA)
, (IB) are divided into two outputs with peak values a and b corresponding to the brightness of the wavelength component (Fig. 3 A, B), and converted to DC by the rectifier circuits (4A) and (4B), respectively. , two DC voltages corresponding to peak values a and b can be obtained.

These two DC voltages are each divided by a divider circuit (II
It is applied to two input terminals (10A) and (IOB).

A D/A converter (one is an analog output VX proportional to the product of the voltage VB applied to the reference voltage terminal (ref) and the digital signal VD applied to the digital input terminal, i.e., VX = VB- Since an analog output of VD--(1) is generated, in the subtraction circuit αΦ, this analog output VX and the input terminal (IOA), (I
The voltage VA applied to OB) and processed by the linearization correction circuit (G) is compared, and the difference voltage between the two is Vs=V
X -VA--(2) is obtained.

This difference voltage Vs is applied to the absolute value amplifier a and amplified first, and then drives the variable frequency oscillator (12) to obtain an oscillation output with a frequency proportional to the absolute value of the difference voltage vs. vs is also applied to the polarity determining circuit Qth to determine its polarity.

Variable frequency oscillator (oscillation output of 1st pin is polarity discrimination circuit a)
The output of the variable frequency oscillator α is applied to the amplifier down counter Qll in the up or down direction according to the output of the polarity determining circuit α9,
The count value is led to the 1)/A converter (11) and the ROMQη.

Then, the count value of this counter α is converted into an analog output VX based on the voltage VB applied to the reference voltage terminal (ref), and a linearization correction circuit (7).
When the output of the subtraction circuit a→ becomes equal, the output of the subtraction circuit a→ stops, the oscillator stops oscillating, and the counter α continues to hold the previous count value.

At this time, the count value VD held in the counter U becomes VD = ■X/VB (3) from the above formula (1), and since VX = 'VA, VD
VA/VB'...-(4) is obtained 4],
Analog voltage VB marked on input terminal (lOB)
and the analog voltage V applied to the input terminals (IOA) and (IOB) and processed by the linearization correction circuit (G).
The ratio of VA/VB to A can be obtained as a digital signal.

On the other hand, the ROM (Iη stores a correspondence table between the digital signal representing the ratio and the color temperature), so by addressing it with the digital signal representing the ratio, the color temperature is output and the stiffness is instructed. The vessel (a) is used to give instructions.

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 Figure 4, but the optical system, photoelectric conversion element, and various circuits Based on the characteristics of the parts, a relationship as shown by the solid line (Y) in FIG. 4 is established.

Therefore, the linearizing auxiliary iE circuit (to) corrects the relationship between the digital signal and color temperature, shown by the solid line (Y) in Figure 4, to the linear shape shown by the dotted line (X) in Figure 4. .

That is, among the color temperature values outputted from the ROMQ71 and expressed in a 4-digit lO number, the signals of the upper two digits are used to output the analog signal that is paired with the linearization correction circuit (7).
Close each pair of switches and connect the input terminal ('l0
The signal applied to A) is passed through the first resistor to the output terminal Q.
1, the signal applied to the input terminal (10B) is guided to the output terminal (G) via the second resistor, and the two are added.

At this time, the first resistor changes the amount of attenuation to obtain the gain Xt, and as shown in FIG.
) to a slope (P-R), and the second resistor changes the state changed to a slope (P-R) to a slope (T-Q
').

In this way, for example, by adjusting the slope and shift of the first and second resistors for each temperature range divided by 100°C, even if the correspondence table is uniformly stored in ROMoη, The IIJ function is to change the characteristic shown by the solid line (Y) to the characteristic shown by the dotted line (X) in FIG. 4, that is, to linearize it.

As explained above, according to the color thermometer of the present invention, by using only one D/A converter, 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 the drawing]

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 waveform diagram used in the division circuit in Figure 2; It is a circuit diagram of a circuit. ■... 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

Claims (1)

[Claims] means for obtaining two electrical signals corresponding to the brightness of two wavelength components included in the light beam radiated from the temperature-measuring object;
a linearizing hli positive circuit that adds two electrical signals via a first resistor and a second resistor, respectively;
a division circuit that obtains a ratio between one of the two electrical signals and the output of the linearization correction circuit;
The divider circuit includes an oscillator, an amplifier down counter for counting the output of the oscillator, a reference voltage input terminal to which one of the two electrical signals is marked +JF], and an amplifier down counter for counting the output of the oscillator. 1)/Has a digital input terminal to which a digital output is applied and outputs an analog voltage.
A converter, and a subtraction circuit that compares the other of the two electrical signals with the analog voltage and controls the counting operation of the up/down counter based on the difference between the two; For color temperature use, the digital output of the amplifier down counter corresponds to the above color temperature.