JPH0464016B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Field of the Invention The present invention relates to a radiation thermometer using an image sensor such as a CCD.

(2) Prior Art Conventionally, the output of a radiation thermometer has a large range of change in incident energy, and the analog calculation circuit for linearization is complex and requires many adjustments.
Furthermore, in order to obtain a digital signal, an expensive, high-resolution A-D converter of about 16 bits was required.

(3) Purpose of the Invention In view of the above points, the purpose of the present invention is to provide a radiation thermometer that can digitally measure the temperature of an object to be measured at low cost, with high precision, and with high reliability using an image sensor or the like. It is to be.

(4) Embodiments of the Invention In the present invention, radiation energy from an object to be measured is separated by a spectroscopic means, and incident on each pixel for each wavelength, and each pixel output corresponding to a plurality of wavelengths is sequentially generated by pulses from a pulse generator. Comparing means for comparing the image sensor to be read and each pixel output of this image sensor with a fixed value and generating an output when they match, and corresponding to a pixel number based on the output of this comparing means and the pulse of the pulse generator. This radiation thermometer is equipped with a counter means for generating an output corresponding to the wavelength, and a memory for outputting the temperature from the pixel number output corresponding to the wavelength of the counter means.

The principle of this invention is as follows.

Spectral radiance L(λ, T) and wavelength λ of thermal radiation,
Planck's radiation law holds between thermodynamic temperature T, and as shown in FIG. 1, a constant curve is formed with respect to temperature T. In a given wavelength region, L
At a point where (λ, T) is a constant value Lo, temperatures T ₁ , ..., Tn are uniquely determined for wavelengths λ ₁ , ..., λn. In other words, the temperature of the object to be measured is determined from the detected wavelength by detecting which wavelength among the plurality of detection signals for the plurality of wavelengths has a constant output value.

In other words, Planck's radiation law is L(λ, T)=2C ₁ /λ ⁵ 1/exp(C ₂ /λT)−1...(
1) (C ₁ , C ₂ ; constants) For example, when radiant energy is separated with a spectrometer and incident on an image sensor (imaging device) such as a CCD, the output of each element (pixel) of the image sensor is Vλ is a function of the corresponding wavelength λ and temperature T, and is expressed by the following equation.

Vλ=A(λ)・L(λ,T)...(2) (A(λ); Spectral sensitivity including optical system and elements) Each pixel of the image sensor and wavelength have a one-to-one correspondence. Since the wavelength λ is a function of the pixel number N, the pixel output V of the pixel number N is a function of the pixel number N and the temperature T, and is expressed by the following equation.

V(N,T)=A(λ(N))・L(λ(N),
T)=A(λ(N))2C ₁ /λ(N) ⁵ 1/exp(C ₂ /λ
(N)T)-1
...(3) Equation (3) is often a bivalent function as shown in Figure 2 due to the wavelength characteristics of spectral sensitivity and spectral radiance, but in an appropriate wavelength range it can be regarded as a monovalent function.

When formula (3) is modified, the temperature T becomes the following formula using the Nth pixel output V(N) and the corresponding wavelength λ(N).

T=f(V(N), λ(N)) =C ₂ /λ(N) 1/ln(2C ₁ /λ(N) ⁵ A(λ(N)
))/V(N)+1)
...(4) If a condition is given for a constant value Vs in equation (4), T becomes a monovalent function of only the wavelength λ, that is, the pixel number N, and the following equation is obtained.

T=g(N) =C ₂ /λ(N) 1/ln(2C ₁ /λ(N) ⁵・A(λ(
N))/Vs+1)
(5) This shows that if the pixel number N at which the pixel output becomes a constant value Vs is determined, the temperature T at that time can be uniquely determined.

FIG. 3 is a configuration explanatory diagram showing an embodiment of the present invention.

In the figure, 1 is the object to be measured, 2 is an optical system consisting of a lens etc. that condenses the radiation energy from the object to be measured 1, S is a slit that narrows down the luminous flux, and 3 is a prism that separates the light from the optical system 2. , a spectroscopic means such as a diffraction grating, and 4 makes the light separated by the spectroscopic means 3 and focused by the lens 2' enter each element to generate output signals corresponding to a plurality of wavelengths λ ₁ ,..., λn.
An image sensor such as a CCD, 5 a comparator that compares the pixel output of each element of the image sensor 4 with a constant voltage value Vs, and generates an output signal when they match; 6 a comparator that generates a pulse signal that drives the image sensor 4; A counter that counts the generated pulses of the pulse signal generator 7 and outputs the element number N based on the output of the comparator 5. 8 is a memory such as a ROM that generates a temperature output in response to the element number output of the counter 6. be. This memory 8 contains a certain value in advance.
A table of temperature T determined by Vs and wavelength is stored, and the comparator 5, counter 6, etc. constitute a calculation means, and this calculation means may be constituted by a microcomputer.

In other words, the radiant energy from the object to be measured 1 that has been focused and separated by the optical system 2 and the spectroscopic means 3 is incident on each element of the image sensor 4, and each element outputs an output corresponding to the incident wavelength λ ₁ ,..., λn. generate a signal,
They are sequentially read out using pulse signals from the pulse signal generator 7, and the counter 6 performs counting in synchronization with the pulse signals. The comparator 5 sequentially compares the outputs of the image sensor 4, and when they match the constant value Vs, causes the counter 6 to stop counting, and stores the count value N (corresponding to each element position of the image sensor 4) at that time in the memory 8. Output to. The memory 8 outputs a temperature T at which the output for the wavelength corresponding to this count value N becomes a constant value Vs. Note that this temperature T can also be obtained by calculation,
A digital output signal directly corresponding to the temperature can be obtained from the output of the counter 6.

In the above example, an image sensor is used as a detector, but radiant energy that has been spectrally divided continuously may be incident on one element.

(5) Summary of the Invention As described above, the present invention provides a detector that receives radiant energy from an object to be measured and generates output signals corresponding to multiple wavelengths, and an output signal corresponding to multiple wavelengths of this detector. The radiation thermometer is equipped with arithmetic device means for calculating the temperature of the object to be measured based on the wavelength at which the signal has a predetermined value.

(6) Effects of the invention Since the temperature is determined from a constant value output using a multi-wavelength signal, the arithmetic unit is simple and a digital signal can be obtained directly, which eliminates the need for expensive A-
A D converter is not required, making it inexpensive and highly reliable.

Also, if the noise in the output V of the radiation thermometer is △V, the temperature resolution △T determined by the noise △V
The ratio between T and the temperature T at that time is determined as follows.

When the spectral radiance L(λ, T) is approximated using the index n instead of equation (1), the following equation is obtained.

L=kT ⁿ (k is a constant) ...(6) Also, the following equation is obtained from equation (2).

V=AL ...(2)' From equation (6), △L=nkT ^n-1 △T = nT ^-1 L△T ∴△T/T=1/n △L/L ...(7) . Also, from equation (2)', △V=A△L, (7)
The formula is: △T/T=1/n △V/A/V/A = 1/n △V/V (8). Furthermore, it is known from Wien's formula that n=C ₂ /λT...(9) holds true.

That is, in the present invention, since the measurement is performed with V constant, ΔV is constant regardless of temperature, and ΔV/V is constant depending on the temperature T.

Also, as can be seen from Figure 1, as the temperature T increases, the measurement wavelength λ also moves in the shorter direction, so from equation (9), the range of change in the n value is smaller than that of a normal radiation thermometer. few.

From this, in equation (8), the n value on the right side, △V/
V is almost constant, and ΔT/T changes less in the measurement temperature range than in a normal radiation thermometer, and is less affected by changes in temperature resolution, making it possible to measure temperature with high accuracy.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams of the present invention, and FIG. 3 is a configuration explanatory diagram showing an embodiment of the present invention. 1...Object to be measured, 2...Optical system, 3...Spectroscopy means, 4...Image sensor, 5...Comparator, 6
...Counter, 7...Pulse signal generator, 8...
memory.

Claims (1)

[Claims] 1. An image sensor in which radiant energy from an object to be measured is separated by a spectroscopic means and incident on each pixel for each wavelength, and each pixel output corresponding to a plurality of wavelengths is sequentially read out by a pulse from a pulse generator, and this image sensor Comparing means for comparing each pixel output with a constant value and generating an output when they match; counter means for generating an output corresponding to the pixel number based on the output of the comparing means and the pulse of the pulse generator; A radiation thermometer comprising a memory for outputting a temperature from a pixel number output corresponding to a wavelength of a counter means.