JP3058218B2 - Radiation measurement equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detector of a radiation measuring apparatus for measuring physical quantities (basis weight, moisture, etc.) of paper, plastic, rubber, etc. using a semiconductor radiation detector.

[0002]

2. Description of the Related Art When radiation (eg, β-rays) passes through a material layer, the energy gradually increases due to ionization and excitation.
And attenuates, and further undergoes such inelastic scattering many times, and the traveling direction changes. Therefore, as the physical quantity (eg, thickness) of the measurement object increases, the number of transmitted β-rays decreases. Devices that measure the physical quantities of various sheet-like substances by applying such a principle are known.

In such a radiation applied measuring apparatus, as shown in FIG. 4, a radiation source (hereinafter, simply referred to as a radiation source) 1 and a radiation detector (hereinafter, simply referred to as a detector) 2 are arranged to face each other.
In the meantime, the measurement is performed with the measured object 3 interposed therebetween. As shown in FIG. 5, the spatial intensity distribution of the radiation from the radiation source is the strongest at the front, and becomes weaker as the distance from the front increases. Therefore, when the radiation source 1 and the detector 2 move relatively in the X, Y or Z directions, there is a problem that the radiation dose incident on the detector 2 changes and the output fluctuates.

Conventionally, a device as shown in FIG. 6 has been proposed as a device for removing this kind of output fluctuation. In FIG. 6, the detector and the radiation source are arranged to face each other with the object to be measured interposed therebetween as in the case of FIG. 4, but reference numeral 10 denotes a plurality of rectangularly-shaped electrically insulating materials (dead zones). One radiation detecting element 2b having the same sensitivity is arranged in the partitioned frame. One side of the frame is, for example, 1 mm, and the width of the frame is, for example, about 50 μm.

FIG. 1A is a diagram showing a spatial intensity distribution of a radiation source. A circle 1b at the center of the radiation detector 2 indicates a range of energy intensity equal to or higher than a predetermined value. In the above configuration, the detection element near the center of the circle 1b outputs a high electric signal, and the elements on the outer periphery output a low electric signal. In this conventional example, the outputs of the elements having a certain output value or more among the outputs of the respective detection elements are summed to obtain the output of the detector.

According to the above configuration, the distribution of radiation can be measured two-dimensionally, and even if the position of the radiation source and the detector are relatively shifted by = Δa in the X direction and = Δb in the Y direction, detection is possible. The output of the vessel is constant. The value at which the output of the detector is truncated is selected in accordance with the intensity of the radiation source, the distance between the radiation source and the detector, the number of elements, the amount of expected deviation, and the like.

[0007]

In the above-mentioned conventional example, the radiation detector needs an area large enough for the expected deviation in the X and Y directions. However, there is a problem that a large detector causes an increase in cost. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has as its object to provide a radiation detector capable of reducing the size and cost of the detector.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a radiation application measuring apparatus of the present invention detects radiation emitted from a radiation source and passing through an object to be measured by a semiconductor radiation detector. In a radiation applied measurement apparatus for measuring a physical quantity of an object to be measured, the detection elements of the semiconductor radiation detector include four detection elements of the same shape and the same sensitivity arranged in a cross on the same plane, and the radiation Are arranged so that the center of the four detection elements illuminates the center of the four detection elements.
Clock or counter clock to output the signal corresponding to the
When V ₁ , V ₂ , V ₃ , V _{4 in the} direction, the center of the radiation
Wherein V ₁ ~V ₄ and X or Y direction deviation of the center of the detecting element and
(V ₁ + V ₄ ) / (V ₂ + V ₃ ) or (V ₁ +
_{V 2) / (V 3 +} V 4) to previously obtain the relationship in advance, from the increase and decrease of the individual signals of the detector that occurs when the center of the four detection elements of said release <br/> ray is deviated A position shift signal is derived, and a measurement signal is self-corrected based on the signal.

[0009]

When the radiation transmitted through the object to be measured is applied to the center of the four detection elements, a signal of the same magnitude is output from each element, and the position of the source and the detector is displaced in the X or Y direction. The signal from each element changes according to the deviation amount. The shift amount is derived from the signal change, and various characteristics are obtained by comparing with the characteristics obtained in advance.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a configuration diagram showing one embodiment of the present invention. In the figure, reference numeral 2 denotes a radiation detector, for example, a detector is formed on a single semiconductor wafer by a known method, and is divided into four equal parts by a linear dead zone having a width of about 10 μm. A ₁ to A ₄ is a amplifier connected to each detector. These amplifiers are fixed in such a manner that their division directions are aligned with the X and Y shift directions of the source and the detector. The configuration other than the detector is the same as the conventional configuration.

In the above configuration, assuming that there is no deviation between X and Y between the radiation source and the detector, and that the β-ray transmitted through the object to be measured is uniformly irradiated on the detector, the output from each amplifier is assumed. V _{1 to} V ₄ are as follows. V ₁ = V ₂ = V ₃ = V ₄ That is, V ₁ + V ₄ = V ₂ + V ₃ , V ₁ +
V ₂ = V ₃ + V _{4 When} the source and the detector are displaced in the X direction, V ₁ + V ₂ = V ₃ + V ₄ is maintained, but V ₁ + V ₄ and V ₂ + V ₃
Will be different.

Next, when the source and the detector are displaced, V ₁ + V ₄
= V ₂ + V ₃ is maintained, but the values of V ₁ + V ₂ and V ₃ + V ₄ are different. Therefore, for example, as shown in FIG. 2, the displacement in the X or Y direction and (V ₁ + V ₄ ) / (V ₂ + V ₃ ) or (V ₁
If the relationship of + V ₂ ) / ( V ₃ + V ₄ ) is obtained in advance, the amount of deviation can be estimated based on the output from each element.

When the basis weight of the measured object changes, V₁~ V_Four
Greatly changes, the index of X is ｛(V₁+ V_Four)-
(V_Two+ V_Three)｝ / (V₁+ V_Two+ V_Three+ V_Four) And Y
The index of ｛(V₁+ V_Two)-(V_Three+ V_Four)｝ / (V
₁+ V_Two+ V_Three+ V_Four). On the other hand, for example for thickness gauge
When obtaining a grammage signal, the sum signal of four detection elements  V₀= V₁+ V_Two+ V_Three+ V_FourUse That is, X or Y direction
If there is a deviation in the direction, the sum signal V₀Changes (note that V₀of
Change rate ΔV, ΔV / V₀Is about 0.5%). Follow
For example, as shown in FIG.
₀, The amount of deviation is calculated from FIG.
Ra V₀Can be corrected. This ΔV is in the X direction
-A (ΔX)^Two, Y-direction shift -a
(ΔY)^TwoCan be represented by the following approximate expression.

Therefore, the displacement in the X direction is a '[{(V ₁ + V ₄ )-(V ₂ + V ₃ )} / (V ₁ + V ₂ + V ₃ + V ₄ )] ² The displacement in the Y direction is a' [｛( V ₁ + V ₂ ) − (V ₃ + V ₄ )｝ / (V ₁ + V ₂ + V ₃ + V ₄ )] a ′ is set so that ² can be approximated to the curve of FIG. 3, and V ₀ = V ₁
If it is added to + V ₂ + V ₃ + V ₄ , the shift amount in the X and Y directions can be corrected. Here, an error with respect to the vertical (Z) displacement between the radiation source and the detector will not be discussed, but the vertical displacement is corrected by another method.

[0015]

According to the present invention, four detection elements having the same shape and the same sensitivity are arranged in a cross on the same plane so that the center of the radiation irradiates the centers of the four detection elements. And the sign of the signal output corresponding to these detection elements.
Let V ₁ , V ₂ , V ₃ , V ₄ be clockwise or counterclockwise.
The X or Y direction of the center of the radiation and the center of the detector
Deviation of direction with the detecting element of the _{V 1 ~V 4 (V 1 +} V 4) /
(V ₂ + V ₃ ) or (V ₁ + V ₂ ) / (V ₃ + V ₄ )
The position shift signal is derived in advance from the increase and decrease of the individual signals of the detector generated when the center of the radiation and the center of the four detection elements are shifted, and the measurement signal is self-corrected based on the signal. Therefore, the area of the detector can be reduced as compared with the conventional one, and a semiconductor radiation detector with reduced cost can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a displacement amount and an output between a radiation source and a detector.

FIG. 3 is an explanatory diagram showing a relationship between a shift amount between a radiation source and a detector and a change rate of an output.

FIG. 4 is a diagram illustrating a positional relationship between a radiation source and a detector.

FIG. 5 is a diagram illustrating an intensity distribution of a radiation source.

FIG. 6 is an explanatory diagram of a conventional example. DESCRIPTION OF SYMBOLS 1 Radiation source 2 Radiation detector 2b Radiation detection element 3 Object to be measured 10 Insulation material.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01T 1/24 G01N 9/24 G01T 1/29

Claims (1)

(57) [Claims] A semiconductor radiation detector for detecting radiation emitted from a radiation source and passing through an object to be measured, and measuring a physical quantity of the object to be measured; vessel's detecting element disposed in field shape in the same plane four detection elements of the same sensitivity in the same shape, arranged so that the center of the radiation irradiates the center of the four detection elements, these detection Output corresponding to the element
V ₁ the sign of the signal in a clockwise or counterclockwise direction that, V _2, V
_3, when the V _4, the center and the detection elements of the radiation center of the
The X or Y direction misalignment with detector elements of the V ₁ ~V ₄ (V ₁
+ V ₄ ) / (V ₂ + V ₃ ) or (V ₁ + V ₂ ) / (V ₃ +
V ₄ ), the center of the radiation and 4
A radiation application measuring apparatus characterized in that a position shift signal is derived from an increase or decrease in individual signals of a detector generated when the centers of two detection elements are shifted, and a measurement signal is self-corrected based on the signal. .