integrating sphere
By covering the diffusive coating of the integrating sphere with a hydrophobic coating, the problem of the integrating sphere efficiency being affected by humidity was solved, and a more stable optical measurement effect was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YOKOGAWA ELECTRIC CORP
- Filing Date
- 2022-08-25
- Publication Date
- 2026-05-12
AI Technical Summary
The efficiency of existing integrating spheres is easily affected by changes in drying conditions, leading to optical measurement errors.
A hydrophobic coating is applied to the diffusion coating of the integrating sphere to suppress moisture absorption caused by humidity and maintain the stability of the coating reflectivity.
The optical measurement accuracy of the integrating sphere was improved, the efficiency fluctuations caused by humidity changes were reduced, and stable light and color measurements were achieved.
Smart Images
Figure CN115727949B_ABST
Abstract
Description
[0001] Cross-reference of related applications
[0002] This application claims priority to Japanese Patent Application No. 2021-140491, filed in Japan on August 30, 2021, the disclosure of which is incorporated herein by reference in its entirety. Technical Field
[0003] This invention relates to an integrating sphere. Background Technology
[0004] An integrating sphere is an optical component used to diffuse and homogenize light from a light source. For example, Patent Document 1 discloses a total luminous flux measuring device including an integrating sphere. In this case, in measuring the total luminous flux of a directional light source, since the measured value varies depending on the measurement direction, it is necessary to repeatedly measure in all directions. Even directional light sources, such as LEDs (Light Emitting Diodes), diffuse repeatedly within the integrating sphere. Therefore, the brightness within the integrating sphere is uniform. Thus, by measuring the brightness within the integrating sphere only once, a measured value proportional to the total luminous flux emitted by the light source can be obtained. However, the light from the light source becomes homogeneous due to repeated scattering and reflection within the integrating sphere, and a portion of it reaches the detector. Therefore, the measured value weakens depending on the reflectivity within the integrating sphere. The proportion of usable light in the incident light is called the efficiency of the integrating sphere. In the case of using an integrating sphere with unknown efficiency, a calibration light source with a known total luminous flux is measured, and the relative luminous flux is measured relative to it, thereby determining the total luminous flux of the object being measured. If the efficiency of the integrating sphere changes during a series of measurements using the integrating sphere, measurement errors will occur; therefore, it is important to prevent variations in the efficiency of the integrating sphere.
[0005] Existing technical documents
[0006] Patent Document 1: Japanese Patent Publication No. 07-146175
[0007] Existing integrating spheres suffer from the problem that their efficiency varies depending on the dryness of the integrating sphere. Summary of the Invention
[0008] The purpose of this invention is to suppress the variation in the efficiency of the integrating sphere by suppressing the moisture absorption of the integrating sphere, thereby improving the accuracy of optical measurements using the integrating sphere.
[0009] Some embodiments of the integrating sphere include: a hollow member; a diffusing coating disposed on the inner surface of the hollow member, which causes light from a light source to be scattered and reflected within the hollow member to become diffused light, wherein a hydrophobic coating is covered on the diffusing coating in the integrating sphere.
[0010] This suppresses the absorption of moisture from the surrounding humidity by the diffusing coating. As a result, it suppresses the decrease in the reflectivity of the diffusing coating and suppresses the variation in the efficiency of the integrating sphere caused by the surrounding humidity.
[0011] In one embodiment, the hydrophobic coating contains a single hydrophobic resin.
[0012] This suppresses the absorption of moisture from the surrounding humidity by the diffusing coating. As a result, it suppresses the decrease in the reflectivity of the diffusing coating and suppresses the variation in the efficiency of the integrating sphere caused by the surrounding humidity.
[0013] Furthermore, diffusing coatings typically consist of barium sulfate powder fixed with gaps between it, causing light reflection at the powder-air interface and resulting in diffusivity. In the case of a hydrophobic coating composed solely of a single hydrophobic resin, the hydrophobic resin penetrates between the barium sulfate powder particles, reducing the reflectivity at the barium sulfate interface, thus decreasing the efficiency of the integrating sphere. The integrating sphere of the present invention has a lower efficiency than an integrating sphere without a hydrophobic coating, but it suppresses variation.
[0014] In one embodiment, the hydrophobic coating contains a powder of a hydrophobic resin and a binder of a hydrophobic resin.
[0015] As a result, light reflection is also caused at the interface between the hydrophobic resin powder and the hydrophobic resin binder. The hydrophobic coating has the function of light diffusion. Therefore, compared with the case of implementing a hydrophobic coating composed of only a single hydrophobic resin, the efficiency of the integrating sphere is improved and the variation of the integrating sphere efficiency is suppressed.
[0016] In one embodiment, the hydrophobic resin powder is transparent at the wavelength of the light and has a particle size larger than the wavelength of the light.
[0017] This suppresses the decrease in the efficiency of the integrating sphere.
[0018] In one embodiment, the adhesive of the hydrophobic resin is transparent at the wavelength of the light and has a refractive index that differs from that of the powder by more than 0.02.
[0019] This suppresses the decrease in the efficiency of the integrating sphere.
[0020] In one embodiment, the hydrophobic resin includes fluoropolymers, silicone resins, polypropylene, polyethylene, or polyethylene terephthalate.
[0021] This suppresses the decrease in the efficiency of the integrating sphere.
[0022] According to the present invention, since the moisture absorption of the integrating sphere is suppressed, thereby suppressing the variation in the efficiency of the integrating sphere, the accuracy of optical measurements using the integrating sphere is improved. Attached Figure Description
[0023] Figure 1 This illustrates an example of applying the integrating sphere of the comparative example to a color measuring device.
[0024] Figure 2 This refers to an integrating sphere representing one embodiment of the present invention.
[0025] Figure 3 This represents the relative change over time in the rate of change of the efficiency of the integrating sphere for the comparative example. The initial value is set to 100%.
[0026] Figure 4 The relative change over time represents the rate of change of the efficiency of the integrating sphere in Example 1 of the invention. The initial value at the start of the measurement is set to 100%.
[0027] Explanation of reference numerals in the attached figures
[0028] 10, 20 Integrating sphere, 1 Hollow component, 2 First opening, 3 Second opening, 4 Diffusion coating, 5 Hydrophobic coating, 30 Light source, 40 Reflector, 50 Cylindrical mirror, 60 Measured object, 70 Collimating lens, 80 Beam splitter. Detailed Implementation
[0029] Embodiments of the present invention will now be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or equivalent constituent elements.
[0030] Reference Figure 1 This illustrates an example of applying the integrating sphere 10 of the comparative example to a color measuring device.
[0031] The integrating sphere 10 includes: a hollow member 1; a first opening 2 for guiding light from the light source 30 into the hollow member 1; and a second opening 3 for guiding diffused light diffused within the hollow member 1 to the outside of the hollow member 1. The first opening 2 is located on the upper part of the hollow member 1 (on the side of the light source 30). The second opening 3 is located on the lower part of the hollow member 1 (on the light-receiving side).
[0032] A diffusing coating 4 is provided on the inner surface of the hollow component 1, which scatters and reflects light from the light source 30 within the hollow component 1 to become diffused light. The diffusing coating 4 generally contains barium sulfate powder and binders such as polyvinyl alcohol (PVA).
[0033] For example, light from a light source 30, such as a white LED, enters the hollow member 1 through the first opening 2, diffuses sufficiently within the hollow member 1, and is emitted as diffused light from the second opening 3 outward from the hollow member 1. A portion of the diffused light emitted from the hollow member 1 is reflected by a cylindrical mirror 50 configured to surround the optical axis and illuminates the object to be measured 60. The vertically upward diffused light scattered by the object to be measured 60 is captured by a reflecting mirror 40 and a collimating lens 70, and its reflection intensity is measured by a beam splitter 80. The reflectivity of the object to be measured 60 is measured by pre-recording the reflection intensity of a reflecting member with known reflectivity. Here, the diffused light emitted from the integrating sphere 10 is uniformly distributed, thus illuminating the object to be measured 60 with the same intensity regardless of direction. Therefore, even if the object to be measured 60 has directional characteristics of reflectivity, stable measurements can be performed regardless of the setting angle of the object to be measured 60.
[0034] However, the PVA contained in the diffusing coating 4 is hydrophilic and absorbs moisture from the surrounding humidity. The absorbed moisture causes the PVA to swell, filling the gaps between the barium sulfate powder particles, sometimes reducing the reflectivity of the diffusing coating 4. Even a slight decrease in the reflectivity of the diffusing coating 4 results in a significant change in the efficiency of the integrating sphere 10 due to repeated reflections within the sphere. Therefore, the efficiency of the integrating sphere 10 in the comparative example varies depending on the surrounding humidity, leading to unstable measurements. For example, when measuring the total luminous flux of the light source 30, a measurement error occurs if the efficiency of the integrating sphere 10 changes from the calibration light source to the light source of the test object 60. Furthermore, in the case of a light source used for color measurement, a measurement error occurs if the efficiency of the integrating sphere changes from the calibration reflector to the test object 60. This is because the drying process of the integrating sphere 10 progresses due to heat from the light source and the apparatus, and its efficiency changes until the integrating sphere 10 is fully dried. Especially in paper mills, in color measuring devices used to determine the color of paper during manufacturing, the sensor is sometimes heated and kept at a constant temperature to suppress the effects of temperature changes during the manufacturing process. In this case, the drying of the integrating sphere 10 may also proceed, causing changes in the efficiency of the integrating sphere 10. To avoid these measurement errors, several hours of standby are required until the changes in the efficiency of the integrating sphere 10 converge.
[0035] In contrast, this embodiment solves the aforementioned problems. Specifically, this embodiment suppresses the variation in the efficiency of the integrating sphere based on ambient humidity. Therefore, stable light intensity or color measurement can be achieved.
[0036] Reference Figure 2 The integrating sphere 20 of this embodiment will be described.
[0037] The integrating sphere 20 includes: a hollow member 1; a first opening 2 for guiding light from a light source; and a second opening 3 for guiding diffused light diffused within the hollow member 1 to the outside of the hollow member 1. The first opening 2 is located on the upper part (light source side) of the hollow member 1. The second opening 3 is located on the lower part (light receiving side) of the hollow member 1. However, the number of openings provided in the integrating sphere 10 is not limited to this and can be arbitrarily determined. For example, a single opening can serve as both a light input and output port, or a light source can be provided within the integrating sphere 10. Hereinafter, the case where the integrating sphere 20 includes the first opening 2 and the second opening 3 will be described in detail, but the present invention is not limited thereto.
[0038] A diffusing coating 4 is provided on the inner surface of the hollow component 1, which causes light from the light source to be scattered and reflected within the hollow component 1 to become diffused light.
[0039] A hydrophobic coating 5 is applied over the diffusion coating 4. That is, the hydrophobic coating 5 is applied over the diffusion coating 4.
[0040] Hollow component 1 is obtained by hollowing out an easily processed and highly reflective metal such as aluminum by any or known method, such that its inner surface is shaped as a sphere.
[0041] The diffusing coating 4 is formed on a metal such as aluminum, which is the raw material of the hollow component 1, by any or known spraying method. The diffusing coating 4 causes light incident from the first opening 2 into the hollow component 1 to diffuse within the hollow component 1. The diffusing coating 4 may contain powder such as barium sulfate and a binder such as polyvinyl alcohol (PVA). In this case, in the diffusing coating 4, the powder such as barium sulfate is supported on the binder such as PVA.
[0042] A hydrophobic coating 5 is applied onto a diffusion coating 4. The hydrophobic coating 5 inhibits the absorption of moisture from the surrounding environment by the diffusion coating 4. As a result, the decrease in reflectivity of the diffusion coating 4 is suppressed, and the fluctuation in the efficiency of the integrating sphere 20 caused by ambient humidity is also suppressed.
[0043] The hydrophobic coating 5 may contain a hydrophobic resin. The hydrophobic resin may include fluoropolymers such as polytetrafluoroethylene (PTFE), silicone resins, polypropylene, polyethylene, or polyethylene terephthalate.
[0044] The hydrophobic coating 5 can also be composed of a single hydrophobic resin.
[0045] Alternatively, the hydrophobic coating 5 may also contain hydrophobic resin powder and a hydrophobic resin binder. In this case, the hydrophobic resin powder is supported on the hydrophobic resin binder in the hydrophobic coating 5. As a result, the hydrophobic resin powder deeply penetrates the spaces between the barium sulfate powder contained in the diffusing coating 4, preventing the spaces from being filled and thus suppressing the decrease in reflectivity of the diffusing coating 4. That is, the hydrophobic coating 5 also has the function of light diffusion, thus suppressing the decrease in efficiency of the integrating sphere 20.
[0046] From the viewpoint of improving diffusion effect, the hydrophobic resin powder is preferably transparent at the wavelength of light from the light source and has a particle size larger than the wavelength of light. Specifically, the hydrophobic resin powder preferably has a particle size of 0.5 μm or more under visible light. Furthermore, from the viewpoint of improving diffusion effect with a defined thickness of the hydrophobic coating (e.g., 50–1000 μm), the hydrophobic resin powder preferably has a particle size of 50 μm or less. Additionally, the particle size of the hydrophobic resin powder is appropriately selected by a sieve having a mesh size corresponding to the particle size.
[0047] From the viewpoint of integrating sphere efficiency, the hydrophobic resin binder is preferably transparent at the wavelength of light from the light source and has a refractive index that differs from the refractive index of the hydrophobic resin powder by more than 0.02.
[0048] From the viewpoint of the efficiency of the integrating sphere, its hydrophobic properties, and its ability to fix the hydrophobic resin powder, the mixing ratio of the hydrophobic resin powder and the hydrophobic resin binder is preferably in the range of 0:100 to 50:50 by volume, and more preferably in the range of 40:60 to 50:50.
[0049] A hydrophobic resin powder and a hydrophobic resin binder are dispersed in a solvent such as butyl acetate, and applied to the inner surface of a hollow component 1 covered by a diffusion coating film 4 using any or known spraying method. The coating amount is preferably 50-1000 g per square meter (when dry). Furthermore, in Figure 2 The diagram shows a morphology where a distinct interface is formed between the diffusing coating 4 and the hydrophobic coating 5. However, the adhesive of the hydrophobic resin contained in the hydrophobic coating 5 penetrates into and fixes the diffusing coating 4. Therefore, when the hydrophobic coating 5 is composed of a single hydrophobic resin, a distinct interface may not sometimes be formed.
[0050] [Example]
[0051] (Comparative Example)
[0052] In the comparative example, an existing integrating sphere (made of barium sulfate powder immobilized by PVA, with a film thickness of 500 μm) was used.
[0053] (Example 1 of the invention)
[0054] In Example 1, a hydrophobic coating is applied to a diffusion coating in an existing integrating sphere using the aforementioned spraying method. This hydrophobic coating contains silicone resin as a binder for the hydrophobic resin and PTFE powder as a hydrophobic resin powder. The particle size of the hydrophobic resin powder is 20 μm. The coating amount is 200 g per square meter (when dry). Furthermore, the mixing ratio of the hydrophobic resin powder to the hydrophobic resin binder is 50:50 by volume.
[0055] (Example 2 of the invention)
[0056] In Invention Example 2, a hydrophobic coating composed of a single fluoropolymer (specifically PTFE) is formed relative to the existing integrating sphere.
[0057] For each invention example and comparative example, the time variation of the rate of change of the integrating sphere's efficiency was investigated. Furthermore, the wavelength of the light used in the measurement ranged from 400 nm to 680 nm, and the light intensity was averaged to obtain the result. Figure 3 and Figure 4 Indicates the result. For example... Figure 3 As shown, in the comparative example, before the power is turned on, the efficiency of the integrating sphere decreases due to moisture absorption caused by the ambient humidity. Furthermore, as the power is turned on, the integrating sphere dries as the device temperature rises, and its efficiency gradually changes. In contrast, as... Figure 4 As shown, in Invention Example 1, moisture absorption is not caused by ambient humidity even before the power is turned on, and the efficiency of the integrating sphere remains constant before and after the power is turned on. Furthermore, in Invention Example 2, an efficiency of only about 30% is obtained compared to the comparative example, but in Invention Example 1, an efficiency of about 60% is obtained compared to the comparative example.
[0058] The present invention has been described above based on the accompanying drawings and embodiments. However, it should be noted that those skilled in the art can make various modifications and alterations based on the present invention. Therefore, it should be understood that these modifications and alterations are included within the scope of the present invention.
[0059] Industrial applicability
[0060] According to the present invention, the performance of the integrating sphere is improved in terms of suppressing the variation of the integrating sphere's efficiency due to ambient humidity. Furthermore, according to the present invention, stable light intensity or color measurement can be achieved. Specifically, optical characteristic measurements using the integrating sphere of the present invention can be performed immediately because the integrating sphere's efficiency stabilizes immediately after power-on. Furthermore, since changes in the integrating sphere's efficiency can be suppressed even with variations in ambient humidity, more stable measurements can be achieved. For example, in the case of measuring the total luminous flux of a light source, changes in the integrating sphere's efficiency from the calibration light source to the light source of the object being measured are suppressed, thereby suppressing measurement errors. Furthermore, in the case of a light source used for color measurement, changes in the integrating sphere's efficiency from the calibration reflector to the object being measured are suppressed, thereby suppressing measurement errors. Moreover, in an apparatus equipped with an integrating sphere, changes in the integrating sphere's efficiency caused by the drying process of the integrating sphere due to heat emitted by the apparatus itself and the heat emitted by the light source itself are suppressed, thus enabling stable measurements immediately after the apparatus is powered on. However, the scope of application of the present invention is not limited to the applications illustrated herein.
Claims
1. An integrating sphere, comprising: Hollow components; A diffusing coating is disposed on the inner surface of the hollow component, and light from a light source is scattered and reflected within the hollow component to become diffused light. The integrating sphere is characterized in that... A hydrophobic coating is then applied over the diffusion-grade coating. The diffusing coating contains barium sulfate powder and polyvinyl alcohol binder. The hydrophobic coating contains hydrophobic resin powder and a hydrophobic resin binder. The hydrophobic resin powder is transparent at the wavelength of the light. The adhesive of the hydrophobic resin is transparent at the wavelength of the light.
2. The integrating sphere according to claim 1, characterized in that, The hydrophobic resin powder has a particle size larger than the wavelength of the light.
3. The integrating sphere according to claim 1 or 2, characterized in that, The hydrophobic resin binder has a refractive index that differs from that of the powder by more than 0.
02.
4. The integrating sphere according to claim 1 or 2, characterized in that, The hydrophobic resin includes fluoropolymers, silicone resins, polypropylene, polyethylene, or polyethylene terephthalate.