JPH07146174A - Photometer - Google Patents

Abstract

PURPOSE:To provide a photometer for optically reducing a system error generated when giving values to all fluxes of light between light sources with different distribution of light and shape using an integrating sphere. CONSTITUTION:Based on the concept of the mutual reflection incidence illuminance coefficient within an integrating sphere, a cylindrical oblique incidence light shielding ring 7 is provided at a position surrounding the periphery of a light receiver 5 for providing an optical means for improving the incidence angle characteristics of the light receiver of a band with the integrating sphere at the light-reception part of the integrating sphere and the cylinder height of the oblique incidence light shielding ring 7 is set to shield the oblique incidence angle at a light reception angle of approximately 70-90.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photometric device comprising an integrating sphere for measuring total luminous flux.

[0002]

2. Description of the Related Art When an integrated sphere is used to measure the total luminous flux of a light source, almost no measurement error appears in the measurement data of a light source of the same type as the total luminous flux standard. That is, since the light bulb is currently used as the total luminous flux standard, the total luminous flux measurement of the light bulb can be realized with relatively high accuracy. However, a number of measurement errors are involved in measuring the total luminous flux of a light source such as a fluorescent lamp, which has a different shape, light distribution, spectral distribution, and self-absorption characteristic from the light bulb. Of these, errors due to shape and light distribution have been partially confirmed by experiments, etc., but a general correction method has not been found yet.

The principle of total luminous flux measurement with an integrating sphere is illustrated in FIG. In FIG. 6, the inner wall surface of the integrating sphere is painted white with barium sulfate or the like, and its reflectance is 0.95 to
Generally, it takes a value of 1.00. A straight tube fluorescent lamp 2 is attached to the center of the integrating sphere 1. Further, the integrating sphere 1 has a light receiving window 4, and a light receiver 5 is attached thereto. A light shielding plate 3 is provided between the light receiving window 4 and the straight tube fluorescent lamp 2 so that the light of the straight tube fluorescent lamp 2 does not directly enter the light receiving window 4. Further, since the total luminous flux standard light bulb with the value of the total luminous flux attached to the center of the integrating sphere, the light shield plate 3 does not reach the light receiver of the light bulb or the straight tube fluorescent lamp as shown in FIG. The shape is provided with such a fluorescent lamp light-shielding portion 3a and a light bulb light-shielding portion 3b.

[0004]

In such an integrating sphere, the light emitted from the light source repeats mutual reflection in the integrating sphere, and each point in the integrating sphere has a certain brightness. . This brightness distribution is ideally uniform, but it is not uniform because the light shielding plate 3 is interposed.
That is, even if both light sources have the same total luminous flux, the illuminance at each point of the integrating sphere takes different values even in the light receiving window 4 because the light bulb and the fluorescent lamp have different shapes and light distributions. The illuminance will be different. Therefore, as a result, a systematic error is included in the measured value. This error changes according to the shape of the light source and the light distribution.

The present invention is intended to solve the above-mentioned problems. A systematic error that occurs when the total light flux between light sources having different light distributions and shapes is valued by using an integrating sphere is considered to be a systematic error in the measurement optical system. It is an object of the present invention to provide a photometric device that can be improved.

[0006]

In order to solve this problem, the photometric device according to the present invention improves the incident angle characteristic of the light receiver in the integrating sphere band based on the concept of the mutual reflection incident illuminance coefficient in the integrating sphere. A cylindrical oblique incident light blocking ring is provided at a position surrounding the light receiving part of the illuminometer, or a cylinder with a conical raised bottom having a diameter larger than that of the circular photometric window is provided. Install a light receiver on the top of the conical raised bottom inside, or in the circular photometric window,
Forming a pair of light-shielding projections to eliminate sudden changes in the illuminance coefficient of mutually opposite incidents by a light-shielding plate provided on the integrating sphere, forming a circular photometric window in an annular shape, or dividing this annular circular photometric window into two It is also made into a shape.

[0007]

As a result, it becomes possible to perform more accurate correction by returning to the essence of the systematic error by optically correcting the measured values individually instead of the conventional method that has been mainly performed. become.

[0008]

EXAMPLES An example of the present invention will be described below. The mutual reflection characteristics when there is a shading plate in the integrating sphere is calculated by using a reflection surface (inner wall surface, shading plate, photometric window) as a set of convex polygonal element surfaces, and calculating the form factor between the element surfaces. Can be represented by the method of calculating The element surface is assumed to be a uniform diffuse reflection surface with uniform illuminance and reflectance, and the form factor F _ji of the element j with respect to the element i is calculated as the illuminance value given to the element i by the element j having a unit luminous flux divergence. it can.
Further, if E _ai and E _{(a + 1) i} are increments of diffused illuminance after reflection a times and (a + 1) times in the element i, the effective reflectance r _ai is r _ai = E _{(a + 1) i.} Can be expressed as / E _ai ,
It is clear that the light converges at a substantially constant number of reflections regardless of the reflectance of the element surface and the initial illuminance value. Therefore, the mutual reflection calculation may be performed until the effective reflectance converges, and the final illuminance value Ei in the element i can be expressed by the following equation, where b is the number of reflections when the effective reflectance converges.

[0009]

[Equation 1]

Here, E _0i represents the initial illuminance of the element i, ρ _j represents the reflectance of the element j, and r _{(b-1) i} represents the effective reflectance of the element i after b times of reflection. Using this calculation method, the inter-reflection incident illuminance coefficient K (θ, φ) of the integrating sphere when the point light source is located at the center of the integrating sphere is calculated, and an example of the values of θ, φ starting from the light receiving window is used as an example. When illustrated, it becomes like FIG. That is, it can be said that FIG. 8 represents the illuminance by the light flux incident on the light receiving window 4 from each point on the inner wall surface of the integrating sphere. Fig. 8 shows one calculation result when a point light source exists at the center of the integrating sphere, but in the case of a rod-shaped light source that emits light even at a position outside the center of the integrating sphere, such as a straight tube fluorescent lamp, its position If K (θ, φ) is calculated for each time and the illuminance incident on the light receiving window can be obtained from the sum of these calculation results, and if the center of the light source is located at the center of the integrating sphere, The characteristics almost similar to are obtained. It can be seen from FIG. 8 that K (θ, φ) is very small around 0 ° to 30 ° where the value of θ is small, that is, around the light receiving window.
It can be seen that there is a maximum value of K (θ, φ) before and after °.
Further, it is known that this maximum value greatly changes depending on the position of the light shielding plate and the shape of the light source. Needless to say, the above simulation is based on the assumption that the oblique incident angle characteristic of the light receiver matches the cosine law.

FIG. 1 is a sectional view of a main part of a photometric device showing a first embodiment of the present invention. In FIG. 1, reference numeral 6 denotes a dome-shaped diffuser plate provided on the front surface of the light receiver 5 in order to match the light-receiving angle characteristic with the cosine law, and the light diffused here enters the light receiver 5 and undergoes photoelectric conversion. It is converted into an electric signal. Also,
The oblique incident light shield ring 7 has a cylindrical shape and is installed so as to surround the diffuser plate 6 as a center, and has a low mutual reflection incident illuminance coefficient in the vicinity of θ = 0 ° to 30 ° and the mutual reflection incident illuminance coefficient. Of large fluctuation of θ = 30 ° -40
Incident light from around °, that is, the acceptance angle is about 70 °
It has a function of blocking the oblique incident angle of ˜90 °. Here, when θ is 40 °, the light receiving angle corresponds to 70 °. As a result, it is possible to significantly reduce the systematic error that occurs when valuing the total luminous flux between light sources having different shapes. In addition, it is important that the inner side surface of the incident light blocking ring 7 is black matte coating so that it does not serve as a secondary light source when viewed from the diffusion surface of the light receiving portion. Further, it is desirable that the outer surface of the incident light shielding ring 7 is coated with white diffusion similar to the inner wall surface of the integrating sphere so as not to reduce the mutual reflection efficiency in the integrating sphere.

FIG. 2 is a sectional view of a main part of a photometric device showing a second embodiment of the present invention. In FIG. 2, the integrating sphere has a circular light receiving window 4, and a cylindrical portion 8 of a cylinder with a conical raised bottom having a diameter larger than the circular shape is installed outside the integrating sphere, and at the opening of the cylindrical portion 8. Has a conical raised bottom 9 connected thereto. Further, the light receiver 5 is installed on the top of the raised bottom portion 9 of the cone, and the light receiver 5 limits the light receiving angle by the light receiving window 4 to approximately 0 ° to 40 °, and the oblique incident angle of approximately 70 ° to 90 °. By providing the function of blocking light, it is possible to significantly reduce the systematic error that occurs when the total luminous flux is priced, even if the shape of the light source changes. Also,
The inner surface of the cylindrical portion 8, the conical raised bottom portion 9 and the outer wall surface of the integrating sphere inside the cylindrical portion 8 are painted black so that the incident light from the light receiving window 4 does not reach the light receiver 5, that is, 70 ° to 90 °.
In addition to absorbing incident light of 90 °, the trap space formed by the cylindrical portion 8 and the conical raised bottom portion 9 is utilized to gradually guide the reflected light to the connecting portion between the cylindrical portion 8 and the conical raised bottom portion 9 to reduce stray light. I am working. In this case, the cylinder 8
If the diameter of the is larger than the light receiving window, stray light is reduced.

Next, as a third embodiment of the present invention, FIG.
A means for optically removing the concave portion of the mutual reflection incident illuminance coefficient by the light shielding plate as shown in FIG. 3 will be described with reference to FIG. FIG. 3 is a plan view showing the light-shielding protrusions provided in the circular light-receiving window 4 of FIG. 2, and the two light-shielding protrusions 10 are provided in a radial direction parallel to the longitudinal direction of the light-shielding plate. The effect of fluctuations can be eliminated optically. In this case, it goes without saying that the structures and characteristics of the cylindrical portion 8, the conical raised bottom portion 9 and the light receiver 5 are the same as those in FIG.

A fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 shows the shape of the light receiving window of FIG.
1 is set, and as a result, 0 ° <θ shown in FIG.
A light source having a different shape or the like is provided with a function of blocking obliquely incident light incident at a light-receiving angle of 70 ° to 90 ° and 0 ° to 20 ° corresponding to <40 ° and 140 ° <θ <180 °, respectively. The systematic error that occurs when valuing the total luminous flux can be significantly reduced. Here, the central light shielding portion 13 of FIG. 4 plays a role of shielding obliquely incident light that is incident at a light receiving angle of 0 to 20 °.

Furthermore, a fifth embodiment of the present invention will be described. In this embodiment, as shown in FIG. 5, the ring-shaped light receiving window 11 of FIG.
The central light shield 13 is mechanically fixed to the integrating sphere by the central light shield support 14. The two central light-shielding portion support portions 14 are provided in alignment with the longitudinal direction of the light-shielding plate, and the central light-shielding portion 13 is fixed to the light-shielding plate 40, so that the 40 ° shown in FIG.
It is possible to optically remove the influence of the concave portion of the inter-reflection incident illuminance coefficient by the light shielding plate, where φ exists in the vicinity of 90 ° and 270 ° when <θ <140 °. It is needless to say that the structures and characteristics of the cylinder 8, the conical raised bottom portion 9 and the light receiver 5 are the same as those in FIG. 2 also in FIGS. 4 and 5.

[0016]

As described above, according to the present invention, the optical means for improving the incident angle characteristic of the light receiver attached to the integrating sphere is provided based on the concept of the mutual reflection incident illuminance coefficient in the integrating sphere. , The systematic error that occurs when the total light flux between light sources with different shapes and light distributions is calculated by using an integrating sphere, and it is possible to realize a more accurate correction that returns to its essence, and it is practical. Great value.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a photometric device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of a photometric device according to a second embodiment of the present invention.

FIG. 3 is a plan view of an essential part of a photometric device according to a third embodiment of the present invention.

FIG. 4 is a plan view of a main part of a photometric device according to a fourth embodiment of the present invention.

FIG. 5 is a plan view of an essential part of a photometric device according to a fifth embodiment of the present invention.

FIG. 6 is a side view and a top view illustrating a schematic configuration of a conventional integrating sphere.

FIG. 7 is a plan view showing another example of the light shielding plate of the integrating sphere.

FIG. 8 is a diagram illustrating an example of a mutual reflection incident illuminance coefficient of an integrating sphere.

[Explanation of symbols]

 1 integrating sphere 2 fluorescent lamp 3 light-shielding plate 4 light-receiving window 5 light-receiver 6 diffuser plate 7 oblique incident light light-shielding ring 8 cylindrical portion 9 conical raised bottom 10 light-shielding protrusion 11 ring-shaped light-receiving window 12 2 split ring-shaped light-receiving window 13 central light-shielding portion 14 center Light shield support

Claims (7)

[Claims] 1. A photometric device comprising an integrating sphere for measuring the total luminous flux, which has an illuminance meter light-receiving part and a cylindrical oblique incident light shielding ring surrounding the illuminance meter. 2. A cylindrical oblique incident light shielding ring has a function of shielding oblique incident light having a cylindrical height of approximately 70 ° to 90 °, the inner surface of the ring is black matte coated, and the outer surface is white. The photometric device according to claim 1, wherein the photometric device is diffusion coated. 3. A total luminous flux measuring integrating sphere having a circular photometric window, a cylinder with a cone-raised bottom having a diameter larger than the circle, and a light receiver installed in the cylinder at the top of the cone-raised bottom. A photometric device. 4. The light blocking angle of oblique incident light formed by the circular photometric window and the light receiver is approximately 70 ° to 90 °, and the inner surface of the cylinder and the inner surface of the conical raised bottom portion are coated with black matte coating to approximately 70 °. The photometric device according to claim 3, wherein a trap space for trapping obliquely incident light of ˜90 ° is formed. 5. The pair of circular photometric windows are formed at a radial position parallel to the longitudinal direction of the shading plate in order to exclude a sudden change in the inter-reflection incident illuminance coefficient due to the shading plate provided on the integrating sphere. The photometric device according to claim 4, further comprising a light-shielding protrusion. 6. The photometric device according to claim 4, wherein the circular photometric window is formed in an annular shape so as to exclude a portion where a coefficient of mutual reflection incident illuminance due to a light shielding plate provided on the integrating sphere is excluded. 7. The ring-shaped circular photometric window for excluding the portion where the mutual reflection incident illuminance coefficient suddenly changes due to the light-shielding plate has a shape bisected in a direction perpendicular to the longitudinal direction of the light-shielding plate. Photometric device.