JP3203901B2 - Measurement position correction arithmetic processing device and radiation intensity measurement device - 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 intensity measuring device.

[0002]

2. Description of the Related Art Conventionally, there is a method of measuring a radiation intensity of a luminous body by constructing a measuring optical system called a telecentric optical system. FIG. 11 shows a conventional measurement optical system. This optical system has an object point 4 outside the optical axis as shown in FIG.
(In the case of FIG. 11, the principal ray (light passing through the center of the aperture of the aperture 6) coming out of the light source 16 to be measured) is parallel to the optical axis. (That is, the aperture is set at the position of the focal point f). The feature of this optical system is that the image height on the projection plate 7 does not change with the movement of the object point in the optical axis direction because the principal ray is parallel in the object space.

[0003] An image of the light source 16 to be measured is formed on the projection plate 7, and light is incident on a light receiver 8 which is close to the projection plate 7 through a sufficiently small hole provided in the projection plate 7. The radiation intensity at is measured. Since the magnification of the image is determined by the ratio of the focal length f and the distance from the aperture 6 to the projection plate 7, the actual distance from the optical axis to the position (measurement position) where light is incident on the light receiver from the actual optical axis to the object The conversion to the distance to point 4 can be obtained by an easy calculation. The radiation intensity at the measured position (output of the light receiver 8) is defined as the radiation intensity at the converted position. Generally, the focal length f of the image space and the aperture 6
When the ratio of the distance from the to the projection plate 7 is set to 1: 1, there is no need to perform magnification conversion. In this case, the position of the light receiver 8 is the position of the object point 4 (however, the image is upside down, left, right, and upside down). Therefore, the sign is reversed.)

[0004]

SUMMARY OF THE INVENTION
When used to measure the radiant intensity of an internal luminous body isolated by a medium different from the medium in which the measurement optical system is present, such as a discharge arc present in the arc tube of a discharge lamp, for example, Light emitted from an object point on the body undergoes refraction development at an interface between different media, and then enters a focal point in an image space. This will be described with reference to FIG.

FIG. 12 shows the trajectory of a light beam 10 transmitted from the object point 4 of the luminous body 3 through the luminous tube 2 and the trajectory of the light beam 11 when the existence of the luminous tube 2 is not considered. , A state in which a difference of a distance δ1 occurs perpendicular to the optical axis. Therefore, in order to derive the actual position of the object point 4 of the light emitting body 3 from the measurement position of the light receiver 8, it is necessary to correct the value of the measurement position in consideration of the distance δ1.

[0006] Further, if the error generated cannot be ignored even after the above correction is performed, it is necessary to improve the measurement accuracy by a new measurement method.

The present invention provides a measurement position correction arithmetic processing device and a radiation intensity measurement device which determine the actual position of an object point of a light emitter from the measurement position of a light receiver and further have a correction method for improving measurement accuracy. The purpose is to:

[0008]

In order to achieve the above object, the present invention uses the following means.

[0009] First, it exists in the arc tube of the discharge lamp.
Measure the radiant intensity of the illuminant, and at least
A light source to be measured and the center of the lens.
The aperture centers of the apertures are arranged on the same optical axis in the order described above.
The aperture and the lens and the receiver
The focal length f of the lens from the lens to the optical device
Measurements for radiant intensity measuring devices placed at remote locations
A position correction arithmetic processing device, wherein the optical axis is an x-axis,
The axis passing through the center of the arc tube and perpendicular to the optical axis is the y-axis,
The inner radius of the arc tube of the constant light source is a, the outer radius is b, and the radiation intensity is
The refractive index of the medium 1 in which the degree measuring device is
The refractive index is n2, the apparent emission existing on the outer wall surface of the arc tube
When the y coordinate of the position of the object point of the light body is yn,

[0010]

(Equation 3)

According to the equation (3), yn is a light emitting object
A measurement position correction arithmetic processing device that converts the value into ym, which is the y coordinate of the position of the point, and outputs the converted value.

Second, it is present in the arc tube of the discharge lamp.
A radiation intensity measurement device that measures the radiation intensity of a luminous body.
At least at the focal point of the lens and the lens.
Light source to be measured and the lens
The center of the aperture and the center of the aperture of the aperture are on the same optical axis.
And the light source to be measured and the lens
A medium on the optical axis between
The distance from the measured point of the constant light source to the optical axis, and the measured point
A light beam emitted toward the light receiver from
Make the distance from the light ray after passing through the medium equal to the optical axis.
It is a radiation intensity measuring device characterized by the following.

[0013] Thirdly, there is an electric discharge lamp in the arc tube.
Measure the radiant intensity of the
A light source to be measured and the center of the lens.
Are arranged on the same optical axis, and the lens is
Placed between the aperture and the light source to be measured, and
A aperture is disposed between the lens and the receiver.
A radiation intensity measuring device, wherein the optical axis is the x-axis, and the arc tube is
An axis perpendicular to the optical axis passing through the center, the y axis, the light source to be measured
The inner radius of the arc tube is a, the outer radius is b, and the radiation intensity is measured.
The refractive index of the medium 1 where the device is present is n1, the refractive index of the arc tube
To n2, the apparent luminous body existing on the arc tube outer wall surface.
The y coordinate of the position of the object point is yn, and further from the center of the arc tube.
Distance L1 to the lens center, light from the lens center
Distance L2 to the intersection of the axis and the aperture, in the lens
Distance L3 from the center to the x coordinate of the position where the light receiver is arranged,
When the focal length f on the image space side of the lens is

[0014]

(Equation 4)

The arithmetic processing of h1 and h2 is performed by (Equation 4).
Calculating means, and the output of the calculating means is
The center of the opening of the aperture is set to the y-axis by a distance of h1.
A first driving means for moving in parallel and an output of the arithmetic means;
The light receiver is flat on the y-axis by the distance of h2, which is the force.
A second driving means for moving to a row is provided.
This is a radiation intensity measuring device .

[0016]

With this configuration, it is possible to provide a radiation intensity measuring apparatus having a correction method for obtaining the actual position of the object point of the luminous body from the measurement position of the light receiver.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a radiation intensity measuring apparatus according to the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 shows a radiation intensity measuring apparatus according to a first embodiment of the present invention.

In FIG. 1, 1 is a radiation intensity measuring apparatus of the present invention, 2 is an arc tube, 3 is a light emitter, 4 is an object point, 5 is a lens, 6 is an aperture, 7 is a projection plate, 8 is a light receiver, Reference numeral 9 denotes a measurement position correction arithmetic processing unit.

In order to set the magnification to 1: 1 and focus the image on the projection plate 4, the center of the light emitting tube 2 of the light source to be measured is placed at a position twice as long as the focal length on the object space side. Is disposed at a position twice the focal length on the image space side. In such a configuration, the trajectory of the light beam 10 after the light emitted from the object point 4 of the luminous body 3 has passed through the luminous tube 2 and the trajectory indicated by the light beam 11 when the existence of the luminous tube 2 is not considered. In this case, since a difference of a distance δ1 occurs perpendicularly to the optical axis, the position measured by the light receiver from the optical axis (in the case of this embodiment, since the magnification is 1: 1, the position is measured perpendicularly from the optical axis of the light beam 11). Distance, i.e., the measured position on the outer wall of the arc tube through which the light passes, is equal to the position of the light receiver from the optical axis).

The optical axis is the x-axis, the axis passing through the center of the arc tube and perpendicular to the optical axis is the y-axis, the medium 1 in which the radiation intensity measuring device exists is air, and the refractive index is n1 = 1, and the arc tube is Is quartz and the refractive index is n2 = 1.46,
Inner radius a = 6 mm and outer radius b =
In the case of 7 mm and the case where the inner radius a of the arc tube is 14 mm and the outer radius b is 15 mm, the y coordinate yn of the position on the outer wall surface of the arc tube where the radiation intensity is measured is +15 mm to -15 mm.

Further, by inputting the a, b, n1, n2 and yn,

[0023]

(Equation 5)

A measurement position correction arithmetic processing means 9 for converting yn into ym and outputting the result is provided.

FIG. 2 shows a radiation intensity measuring apparatus according to the present invention, in which light emitted from an object point 4 of a luminous body 3 radiates parallel to the optical axis, is refracted at an inner wall point m of the luminous bulb 2, and At the outer wall point n, and travels again in parallel with the optical axis.

The optical axis is the x axis, the axis passing through the center of the arc tube and perpendicular to the optical axis is the y axis, the inner radius of the arc tube is a, the outer radius is b, and the refraction of the medium 1 in which the radiation intensity measuring device exists. The rate is n1,
By inputting the refractive index of the material of the arc tube 2 to n2 and the y coordinate yn of the position on the outer wall of the arc tube at which the radiation intensity was measured to the measurement position correction arithmetic processing means, the corrected distance indicated by ym (that is, The procedure for outputting the y-coordinate of the object point 4) will be described below.

Α is

[0028]

(Equation 6)

At the point n, according to the law of refraction,

[0030]

(Equation 7)

## EQU1 ## Therefore, β = α−θ point m (xm, ym), point n (xn, yn) = (bcos
θ, yn), the number of straight lines mn having an inclination of an angle β with respect to the x-axis is expressed as ym−yn = tanβ (xm−bcosα). On the other hand, the equation of a circle having an inner radius a is xm ² + yn ² = a ² , and the coordinates (x
m, ym),

[0032]

(Equation 8)

Ym = xmtanβ + (yn-bcosαtanβ)

The position of the object point 4 of the luminous body 3 can be obtained as an output by incorporating the measurement position correction arithmetic processing means 9 operating as described above into the radiation intensity measuring device.

The correction values ym and y obtained by this method
The ratio of the difference δ1 with n to yn is shown in the graph of FIG. Generally, the discharge arc of a discharge lamp has a radius of about half of the inner radius of the arc tube.
In the case of mm, about 5% of the measurement position near the end of the luminous body, inner radius 1
In the case of 4 mm, it is possible to realize a measurement position correction of about 3%. By combining the measurement position correction arithmetic processing means with a conventional radiation intensity measurement device, without performing any operation on the conventional measurement optical system, it is possible to perform a measurement position correction process in a short time, and in the luminous body The position of the object point can be known.

When the inner radius is 6 mm or less or when the thickness of the arc tube is 1 mm or more, the ratio of δ1 to yn is further increased, so that the radiation intensity measuring device is more effective.

In this embodiment, the aperture 6 and the projection plate 7 are used in order to set the enlargement magnification to 1: 1 and to simplify the arithmetic processing.
Is set equal to the distance between the center of the lens 5 and the aperture 6. However, even if the distance between the aperture 6 and the projection plate 7 is set arbitrarily, the same applies if the measured value is converted in consideration of the magnification. Measurement position correction calculation processing is possible.

In this embodiment, the incident angle of light on the light receiving surface of the light receiver 8 is not particularly considered. However, the response of the light receiving surface depends on the incident angle of light and poses a problem in measurement. In this case, a light-receiving device having a spherical light-receiving surface may be used, or a rotation driving means may be provided to the light-receiving device 8 so that the light-receiving surface is always perpendicular to the incident light.

(Embodiment 2) FIG. 4 shows a radiation intensity measuring apparatus according to a second embodiment of the present invention.

In FIG. 4, the center of the light emitting tube 2 of the light source to be measured is positioned at twice the focal length on the object space side in order to set the magnification to 1: 1 and focus the image on the projection plate 4. ,
The projection plate 7 is arranged at a position twice the focal length on the image space side. FIG. 4 shows the state of the measuring optical system. In such a configuration, the inner radius of the arc tube of the light source to be measured is a
= 6 mm, outer radius b = 7 mm, and the material of the arc tube is quartz.

A medium 12 which is made of quartz and has a section whose cross section is a curved surface having a center of curvature o at the same position, an inner surface having a radius of 6 mm and a central angle of 180 °, and an outer surface having a radius of 7 mm and a central angle of 180 °.
At an arbitrary position on the optical axis between the center of the arc tube 2 and the lens 5, a center of curvature o exists on the optical axis, and the medium 12
Is arranged between the center of curvature o and the arc tube 2.

In such a configuration, light emitted from the object point 4 of the luminous body 3 is refracted when passing through the arc tube, and is refracted again when passing through the medium 12. in this case,
According to the law of ray regression, the distance of the object point 4 from the optical axis is equal to the distance from the optical axis after passing through the medium 12.

According to this method, the position of the light receiver 8 from the optical axis becomes equal to the position of the object point 4 of the luminous body 3 from which the light is emitted. It is possible to correspond to the object point 4 of the luminous body 3 without applying.

In this embodiment, the distance between the aperture 6 and the projection plate 7 is equal to the distance between the center of the lens 5 and the aperture 6 in order to make the magnification ratio 1: 1. Even if the distance from the object 3 is set arbitrarily, the position of the object point 4 of the light emitting body 3 can be easily obtained by converting the measured value in consideration of the magnification.

In this embodiment, the incident angle of light with respect to the light receiving surface of the light receiver 8 is not particularly taken into consideration. However, in the case where the responsivity of the light receiving surface depends on the incident angle of light and poses a problem in measurement. In this case, a light-receiving device having a spherical light-receiving surface may be used, or a rotation driving means may be provided to the light-receiving device 8 so that the light-receiving surface is always perpendicular to the incident light.

(Embodiment 3) FIG. 5 shows a radiation intensity measuring apparatus according to a third embodiment of the present invention.

In FIG. 5, the optical axis is the x axis, the axis passing through the center of the arc tube and perpendicular to the optical axis is the y axis, the medium 1 in which the radiation intensity measuring device is present is air, and the refractive index is n1 = 1,
The material of the arc tube is quartz and its refractive index is n2 = 1.46.
And the distance L from the center of the arc tube 2 to the center of the lens 5
1 = 400 mm, optical axis and aperture 6 from center of lens 5
L2 = 200 mm to the intersection with the distance L3 = 4 from the center of the lens 5 to the x coordinate of the position where the light receiver 8 is arranged.
00 mm and the focal length in the image space is f = 200 mm. This is shown in FIG.

The inner radius a of the arc tube 2 of the light source to be measured is a = 6 mm,
When outer radius b = 7 mm, inner radius a of arc tube 2 = 14 m
m, the outer radius b = 15 mm, the y-coordinate yn of the position on the outer wall surface of the arc tube whose radiation intensity is to be measured is +15 mm to
-15 mm.

In the radiation intensity measuring apparatus of this embodiment, if the trajectory of light emitted from an arbitrary point on the outer wall of the arc tube is traced in reverse to the object point of the illuminator, strictly speaking, It is not a ray emitted parallel to the optical axis. This is shown in FIG. This occurs because the refraction interface at point m and the refraction interface at point n are not exactly parallel. Conversely, it means that light radiated from the object point of the luminous body parallel to the inner wall of the arc tube does not radiate parallel to the optical axis when radiating from the outer wall of the arc tube through refraction. FIG. 7 shows this state, and FIG. 8 shows a radiation intensity measuring optical system in consideration of the deviation η of the emitted light from the optical axis. The optical system shown in FIG. 8 uses n on the outer wall surface of the arc tube to be measured.
In order to track light emitted at an angle of η from a point, the center of the aperture of the aperture 6 is positioned at h1 from the optical axis, and
Is moved to the position of h2 to perform measurement.

In FIG. 7, the optical axis is the x axis, the axis passing through the center of the arc tube and perpendicular to the optical axis is the y axis, the inner radius of the arc tube is a,
The outer radius is b, the refractive index of the medium 1 in which the radiation intensity measuring device is present is n1, the refractive index of the material of the arc tube 2 is n2, and the y coordinate yn of the position on the outer wall surface of the arc tube whose radiation intensity is to be measured is calculated. The procedure in which h1 and h2 are output by input to the processing means will be described below.

Α is

[0052]

(Equation 9)

At the point n, according to the law of refraction,

[0054]

(Equation 10)

Is as follows. Therefore, if β = α−θ, the point m (xm, ym) and the point n (xn, yn) =
The equation of a straight line mn passing through (bcos θ, yn) and having an inclination of an angle β with respect to the x-axis is expressed as ym-yn = tanβ (xm-bcosα). On the other hand, the equation of the circle having the inner radius a is xm ² + ym ² = a ^2. By solving the above simultaneous equations, the coordinates (xm, ym) of the point m are obtained.

[0056]

[Equation 11]

Ym = xmtanβ + (yn-bcosαtanβ)

From the coordinates (xm, ym) of the obtained point m,

[0059]

(Equation 12)

The light emitted from the point n travels in parallel to the optical axis only when the boundary surface between the point m and the point n is parallel, and the incident angle at the point n is θ + (γ−α ), The refraction angle becomes α + (γ−α) = γ, and parallelism is realized. Since the refractive ratio at the interface of the medium depends only on the refractive index of the medium,

[0061]

(Equation 13)

Is established. This κ is calculated at n points (Equation 1)
Since the refraction angle satisfies the refraction ratio of 3), the deviation angle η between the light emitted from the outer wall of the arc tube and the optical axis is η = α−κ.

In the radiation intensity measuring optical system shown in FIG. 8 constructed on the basis of these, a distance L 1 from the center of the arc tube 2 to the center of the lens 5, and a distance L 1 from the center of the lens 5 to the intersection of the optical axis and the aperture 6. The distance L2, the distance L3 from the center of the lens 5 to the x-coordinate of the position where the light receiver 8 is arranged, the focal length in the image space as f, and light emitted at an angle η from point n is virtually the optical axis. The distance from the point considered to be emitted from above to the center of the lens 5 is S1, the distance from the center of the lens 5 to the point where light intersects the optical axis in the image space is S2,
Assuming that the position of the light at the center of the lens 5 is h, the position of the aperture center of the aperture 6 from the optical axis is h1, and the position of the light receiver 8 from the optical axis is h2, an image of the lens of this optical system is formed. ceremony,

[0064]

[Equation 14]

## EQU10 ## Therefore, the sought h1 and h1
2 is

[0066]

(Equation 15)

[0067]

(Equation 16)

Is obtained. By inputting the value of h1, which is the output of the arithmetic processing means 13 performing such an operation, to the driving means 14 of the aperture 6 connected to the aperture 6, the above h is obtained.
The center of the aperture of the aperture 6 is moved parallel to the y-axis by a distance of 1 and the value of h2, which is the output of the arithmetic processing means 13, is input to the driving means 15 of the light receiver 8 connected to the light receiver 8. After moving the light receiver 8 parallel to the y-axis by the distance h2, the light intensity is measured by the light receiver 8.

The relationship between the y-coordinate yn of the position on the outer wall surface of the arc tube where the radiation intensity is to be measured, the movement distance h1 of the aperture 6 and the movement distance h2 of the light receiver 8 obtained by this method is shown. FIG. 9 shows a case where the inner radius is 6 mm, and FIG. 10 shows a case where the inner radius of the arc tube 2 is 14 mm. According to this method, it is possible to accurately track light emitted from an arbitrary object point of the light-emitting body 3, and the position of the object point and the light receiver 8
It became possible to completely correspond to the position.

In this embodiment, the outputs h1 and h2 of the arithmetic processing means 13 are input to the two types of driving means 14 and 15, but the two inputs h1 and h2 are received, and the aperture 6 and the light receiver 8 are supported by one. The support may be fixed to both ends of the tool, and a supporting point may be provided on the support to form a mechanical interlocking driving means for driving the support.

In this embodiment, the outputs h1 and h2 of the processing and arithmetic processing means 13 are input to the two kinds of driving means 14 and 15, but the two inputs h1 and h2 are received and the aperture 6
Alternatively, the light receiver 8 may be fixed to both ends of a single support, and a fulcrum may be provided on the support to form a mechanical interlocking driving means for driving the support.

In this embodiment, the incident angle of light on the light receiving surface of the light receiver 8 is not particularly considered. However, the responsivity of the light receiving surface depends on the incident angle of light and causes a problem in measurement. In this case, a light-receiving device having a spherical light-receiving surface may be used, or a rotation driving means may be provided to the light-receiving device 8 so that the light-receiving surface is always perpendicular to the incident light.

[0073]

As described above, in the present invention, in consideration of the refraction of the radiated light by the light receiving tube, which has not been performed in the prior art in the radiation intensity measuring apparatus, (1) the measurement position is input and the position of the object point is input. Is provided in the apparatus, the measurement position correction processing can be performed in a short time.

(2) By arranging a new medium in the measuring optical system, it is possible to realize an apparatus configuration that does not require the measurement position correction processing.

(3) Arithmetic processing means for inputting the position to be measured and outputting the position of the object point, the moving distance of the aperture, and the moving distance of the light receiver, and inputting the moving distance and moving the aperture and the light receiver By providing the two driving means, the position of the object point of the light emitter and the position of the light receiver can be completely matched, and the accuracy of radiation intensity measurement can be improved.

If the measurement is performed by moving the light receiver two-dimensionally on the projection plate, the radiation intensity distribution of the light emitter can be measured. Further, by using a light receiver provided with a spectral optical system, it becomes possible to measure the spectral radiation intensity and the spectral radiation intensity distribution. Therefore, using the above-described apparatus for measuring the radiation intensity distribution of the discharge arc of a discharge lamp,
It is very effective for analyzing the physical properties of the discharge arc in the arc tube.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a radiation intensity measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for deriving a measurement position correction distance according to the first embodiment;

FIG. 3 is a measurement position correction characteristic diagram according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a radiation intensity measuring apparatus according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a radiation intensity measuring apparatus according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram for deriving a drive distance of an aperture and a light receiver according to a third embodiment.

FIG. 7 is an explanatory diagram for deriving a drive distance of an aperture and a light receiver according to a third embodiment.

FIG. 8 is an explanatory diagram for deriving a drive distance of an aperture and a light receiver according to a third embodiment.

FIG. 9 is a driving distance characteristic diagram of an aperture and a photodetector according to a third embodiment of the present invention.

FIG. 10 is a driving distance characteristic diagram of an aperture and a photodetector according to a third embodiment of the present invention.

FIG. 11 is a configuration diagram of a conventional optical system for measuring radiation intensity.

FIG. 12 is a configuration diagram of a conventional optical system for measuring radiation intensity.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 medium 2 arc tube 3 illuminant 4 object point 5 lens 6 aperture 7 projection plate 8 light receiver 9 measurement position correction arithmetic processing means 12 medium 13 arithmetic means 14, 15 drive means 16 light source to be measured

Continuation of front page (56) References JP-A-61-130832 (JP, A) JP-A-2-302879 (JP, A) JP-A 64-3265 (JP, U) JP-A-4-32852 (JP) , Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01J 1/00-1/60 G01N 21/00-21/01 G01N 21/17-21/61

Claims (3)

(57) [Claims] 1. A luminous intensity of a luminous body existing in an arc tube of a discharge lamp is measured, and at least a lens, an aperture, and a light receiver are provided, and a light source to be measured, a center of the lens, and an opening center of the aperture have the same optical axis. A measurement position correction arithmetic processing unit used for a radiation intensity measurement device disposed above the above-mentioned order and the aperture is disposed between the lens and the light receiver at a position away from the lens by a focal length f of the lens. Wherein the optical axis is the x axis, the axis passing through the center of the arc tube and perpendicular to the optical axis is the y axis, the inner radius of the arc tube of the light source to be measured is a, the outer radius is b, and the radiation intensity measurement is performed. The refractive index of the medium 1 in which the device is present is n1, and the refractive index of the arc tube is n.
2. When the y-coordinate of the position of the object point of the apparent luminous body present on the outer wall surface of the arc tube is yn, According to (Equation 1), the yn is set to y at the position of the object point of the luminous body.
A measurement position correction arithmetic processing unit, which converts the value into ym, which is a coordinate, and outputs the converted value. 2. A radiation intensity measuring device for measuring the radiation intensity of a luminous body present in an arc tube of a discharge lamp, comprising: at least a lens; an aperture disposed at a focal position of the lens; And the center of the lens and the center of the aperture of the aperture are arranged on the same optical axis in the order described above, and a medium is arranged on the optical axis between the light source to be measured and the lens. A light beam emitted from the measured point to the optical receiver from the measured point to the optical axis, wherein the distance from the measured light source to the optical receiver is equal to the distance from the light beam transmitted through the medium to the optical axis. A radiation intensity measuring device, characterized in that: 3. A luminous intensity of a luminous body present in a luminous tube of a discharge lamp is measured, and at least a lens, an aperture, and a light receiver are provided, and a light source to be measured and a center of the lens are arranged on the same optical axis. The lens is a radiation intensity measuring device disposed between the aperture and the light source to be measured, and the aperture is disposed between the lens and the light receiver, wherein the optical axis is the x-axis, the light emission is The axis passing through the center of the tube and perpendicular to the optical axis is the y-axis, the inner radius of the light emitting tube of the light source to be measured is a, the outer radius is b, the refractive index of the medium 1 in which the radiation intensity measuring device is present is n1, and the light emission is The refractive index of the tube is n2, and the y coordinate of the position of the object point of the apparent luminous body existing on the outer wall surface of the luminous tube is y
n, a distance L1 from the center of the arc tube to the center of the lens, a distance L2 from the center of the lens to an intersection between the optical axis and the aperture, and a distance L3 from the center of the lens to the x coordinate of a position where the light receiver is arranged. , Where the focal length f of the lens on the image space side is: A first driving means for providing an operation means for performing the operation processing of h1 and h2 according to (Equation 2), and moving the center of the aperture opening parallel to the y-axis by the distance of h1 which is the output of the operation means; And a second driving means for moving the light receiver parallel to the y-axis by a distance of h2 which is an output of the calculating means.