JP2017120200A5 - - Google Patents

Description

Spectroradiometer

  The present invention relates to a spectral radiation measurement apparatus.

  The total luminous flux is measured as one index indicating the brightness of the light source. The measurement of the total luminous flux is calculated by comparing the measured value of the total luminous flux measured using a standard light source with the measured value of the light source to be measured (Patent Documents 1 and 2). Conventionally, a standard light bulb has been exclusively used as a standard light source for measuring the total luminous flux. In recent years, lighting fixtures using light-emitting diodes (also referred to as solid-state element illumination) have been widely used. For solid-state element illumination, a spectral radiation measurement device using a standard bulb is used. Total luminous flux is being measured.

JP 2009-103654 A JP 2010-271235 A

  However, when measuring the total luminous flux of solid-state lighting using a conventional spectroradiometer that uses a standard light bulb, the total luminous flux is accurately measured because the emission spectrum and light distribution characteristics of the solid-state lighting differ greatly from those of a standard light bulb. There were cases where it was not possible.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a spectral radiation measuring apparatus capable of accurately measuring the total luminous flux of a lighting fixture using a light emitting diode or the like.

In order to achieve the above object, a spectroradiometry apparatus according to an aspect of the present invention includes:
An entrance slit; a dispersion unit that changes an exit angle of incident light incident from the entrance slit according to a wavelength; and an exit slit that emits light in a specific wavelength band among the light dispersed by the dispersion unit. A spectroscope equipped with,
Light introducing means for irradiating the incident slit with light emitted from the light source to be measured as diffused light;
A standard light source as a reference for spectral distribution measurement;
With
The standard light source includes a light emitting diode and a phosphor excited by light from the light emitting diode,
A spectral distribution Ps (λ) of the standard light source, a second derivative Ps ″ (λ) of the spectral distribution Ps (λ), a width of the entrance slit, a dispersion characteristic of the dispersion means, and a width of the exit slit. The wavelength width Δλ (nm) of the slit function defined based on the above satisfies the relationship of the following formula (1) in the wavelength range of 380 nm to 780 nm.
Δλ ² × ( | Ps ″ (λ) | / Ps (λ)) <0.5 (1)

  According to the spectral radiation measuring apparatus according to one aspect of the present invention configured as described above, it is possible to provide a spectral radiation measuring apparatus that can accurately measure the total luminous flux of a lighting fixture using a light emitting diode or the like.

It is a schematic diagram which shows the structure of the spectral radiation measuring apparatus of embodiment which concerns on this invention. It is a graph which shows the measurement result of the spectral distribution of white LED marketed. It is a graph which shows the calculation result of the measurement error at the time of performing spectral radiation measurement using white LED as a standard light source based on the spectral distribution shown in FIG. 2A. It is typical sectional drawing which shows the state which attached the standard light source 1 which concerns on embodiment to the folder. It is a top view which shows the structure of the standard light source 1 which concerns on embodiment. It is a graph which shows the spectral distribution of the light source of A type and B type which concern on the standard light source 1 of embodiment. It is a graph which shows the calculation result of the measurement error at the time of performing spectral radiation measurement using the light source of A type and B type as a standard light source based on the spectrum distribution shown in Drawing 4A.

  Hereinafter, a spectral radiation measuring apparatus according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the spectral radiation measurement apparatus according to the embodiment includes a light introducing unit 10, a spectroscope 20, and a detector 30, and further includes a standard light source 1 as a reference for spectral distribution measurement.

In the spectral radiation measurement apparatus, the light introducing unit 10 includes an integrating sphere 10 a, a light source mounting unit 11, an emitting unit 12, and a light shielding plate 13, and is emitted from a measured light source provided in the light source mounting unit 11. The light introducing means emits the light having the intensity that is averaged without depending on the shape of the light source to be measured and the light distribution characteristics. More specifically, the inner wall of the integrating sphere 10a is a diffuse reflection surface, and light from the light source to be measured is multiple-reflected by the inner wall of the integrating sphere 10a, and the reflected diffused light irradiates the inner wall of the integrating sphere 10a. Then, the inner wall of the integrating sphere 10a is evenly irradiated from the light source to be measured regardless of the direction and distance. In this way, a part of the uniformly irradiated light (diffuse reflected light) is taken out from the emitting unit 12 and irradiated onto the incident slit surface of the spectrometer 20. By such a light introducing section, a constant ratio of light is always emitted from the emitting section 12 with respect to the total light flux (total light flux) emitted from the light source to be measured. The light shielding plate 13 is disposed between the light source mounting portion 11 and the light emitting portion 12 so that light emitted from the light source to be measured is not directly emitted from the light emitting portion 12, and the inner wall of the integrating sphere 10a. Only the light reflected by the light is taken out from the emitting part 12.
A member denoted by reference numeral 14 is a self-absorption correcting light source.

  The spectroscope 20 includes an entrance slit plate 21 formed with an entrance slit plate 21, a dispersion means 22, and an exit slit plate 23 formed with an exit slit 23 s. Here, the entrance slit 21 s and the exit slit 23 s are set so that the slit wavelength width is the same, for example. The dispersing means 22 includes a plane mirror 22M1, a collimator mirror 22Mc, a diffraction grating 22G, a focusing mirror 22Mf, and a plane mirror 22M2. In the spectroscope 20 configured as described above, incident light incident from the incident slit 21 s is dispersed according to the wavelength and irradiated onto the output slit plate 23. Of the light irradiated on the exit slit plate 23, only the light having a specific wavelength irradiated on the exit slit 23s is emitted. The spectroscope 20 also includes a control unit that controls the direction of the diffraction grating 22G. By changing the direction of the diffraction grating 22G by the control unit, the wavelength band of light emitted from the output slit 23s is changed. be able to.

  The detector 30 measures the intensity of light in a specific wavelength band emitted from the exit slit 23 s of the spectrometer 20.

  Here, in particular, the spectral radiation measurement apparatus of the present embodiment includes a standard light source 1 including a light emitting diode and a phosphor excited by light from the light emitting diode, instead of a standard light bulb that has been conventionally used. Yes. Then, the spectral distribution Ps (λ) of the standard light source 1, the secondary differential coefficient Ps ″ (λ) of the spectral distribution Ps (λ), the width of the entrance slit 21s, the dispersion characteristics of the dispersion means 22, and the exit slit 23s. The wavelength width Δλ (nm) of the slit function defined on the basis of the width is set so as to satisfy the relationship of the following formula (1) in the wavelength range of 380 nm to 780 nm. As described above, when the wavelength width Δλ of the slit function is 2.5 nm, the spectral distribution can be measured with a measurement error of 1% or less. Since the standard light source 1 including the phosphor excited by the light from the light emitting diode is provided, the total luminous flux of the solid light source illuminator with a light emission spectrum and light distribution characteristics greatly different from that of the standard light bulb can be accurately measured. Rukoto becomes possible.

Δλ ² × ( | Ps ″ (λ) | / Ps (λ)) <0.5 (1)

  Hereinafter, the measurement accuracy of the spectral radiation measuring apparatus including the standard light source 1 including the light emitting diode and the configuration of the standard light source 1 will be described in detail. The present invention has been made as a result of repeated studies by the present inventors in order to solve various problems of the spectral radiation measuring apparatus using a standard bulb. Including.

  When evaluating the spectral radiant flux (or spectral irradiance, hereinafter referred to as spectral distribution) of a light source to be measured using a spectral radiometer having a finite slit wavelength width Δλ calibrated with a standard light source. Due to the influence of the slit function of the spectroscope 20, an error occurs in the spectral distribution of the light source to be measured. This error ultimately affects the radiant flux value of the light source to be measured, which is the wavelength integration amount.

  In general, solid-state element illumination has a steep spectral distribution as compared with a standard bulb, and thus, for example, it has been considered difficult to use a solid-state light source including a light-emitting diode as a standard light source of a spectroradiometer. . For example, when a white LED having a steep peak in a part of the wavelength range is used as the standard light source, it is assumed that the effect of the slit function of the spectroscope 20 appears significantly.

  Therefore, the present inventors have studied paying attention to the fact that the change of the second derivative will be large in the vicinity of the peak in the spectral distribution of the standard light source.

The spectral distribution of the light source to be measured, when _{P t (λ), P t} (λ) is the measured value at the time of measuring the light source to be measured with a spectral radiometer R _{t (lambda),} measured standard light source with a spectral radiometer The measured value R _s (Λ) at the time and the spectral distribution P _s (λ) of the standard light source are given by the following expression (2) (JIS Z 8724 and the like).

  In equation (2), λ is the wavelength of light, Λ is the wavelength of the spectroradiometer, and H (Λ) is the response at the wavelength Λ of the spectroradiometer.

Based on the above equation (2), in order to evaluate the error due to the influence of the slit function,
(I) The measured value R (Λ) of the spectroradiometer is given by the slit function g (λ, Λ) of the spectroradiometer, the response H (Λ) of the spectroradiometer, and the spectral distribution P (λ) of the light source: Given by equation (3)
(Ii) Further, assuming that the slit function g (λ, Λ) is given by an isosceles triangle having a slit wavelength width Δλ, the expression (3) can be approximated by the expression (4). 5) was obtained.
Here, it is generally known that the slit function is an isosceles triangle, and there is no problem with the assumption in (ii).

(5)

From the above equation (5), the error based on the spectral distribution of the standard light source and the slit function of the spectroscope is proportional to the square of (Ps ″ (λ) / Ps (λ)) and the slit wavelength width Δλ (nm). I understand.
According to the equation (5), when the slit wavelength width Δλ is 2.5 nm, if a light source having a spectral distribution satisfying the equation (1) is used as a standard light source, the spectral distribution is 1% or less with a measurement error. It can be seen that can be measured.

Measurement Error When Using White LED as Standard Light Source First, the present inventors first measured the spectral distribution of a commercially available white LED using Equation (5) and used the white LED as a standard light source. The measurement error in the case of spectral radiation measurement was evaluated.
FIG. 2A shows the spectral distribution of the white LED. FIG. 2B shows the measurement error calculated based on the formula (5) for the spectral distribution of the white LED. This error evaluation was performed in the range of 410 nm to 780 nm because the white LED to be evaluated hardly emits light having a wavelength of 410 nm or less.

  From the above evaluation results, when spectral emission measurement is performed using a white LED as a standard light source, as shown in FIG. 2B, the measurement error in the wavelength range of 510 nm or less is large, but the wavelength range of more than 510 nm is relatively a measurement error. Was confirmed to be small. Even if the measurement error is relatively small in the wavelength range greater than 510 nm, the error is still large compared to the case where the standard bulb is used in the wavelength range greater than 510 nm. The white LED used for this evaluation is a blue light emitting diode (gallium nitride based semiconductor light emitting diode) having a peak wavelength near 455 nm and a phosphor that emits light having a wavelength longer than that of the excitation light when excited by the light of the blue light emitting diode. It is a white LED containing (cerium-activated yttrium aluminum garnet (YAG) phosphor), and light emission in the wavelength region of 500 nm or less is dominated by the light of the blue light-emitting diode, and in the wavelength region greater than 500 nm The light of the phosphor is dominant.

In the present embodiment, based on the above evaluation results, the standard light source 1 including a light emitting diode is configured with the following concept.
(A) First, it is preferable that the light of the phosphor is dominant in a wider range than the white LED.
Specifically, a light emitting diode having a shorter wavelength than that of the blue light emitting diode used in the white LED is used, and instead of the light emitting diode having a steep peak in the blue region, the change in the amount of change in the intensity distribution (in the spectral distribution). The light of the phosphor whose inclination change, that is, the second derivative of the spectral distribution) is smaller than the light emitting diode is made dominant. Thereby, the secondary differential coefficient of the spectral distribution can also be reduced for the blue region.
(B) In order to reduce the secondary differential coefficient of the spectral distribution in a short wavelength region (for example, a wavelength region of 380 nm to 410 nm) where light from the light emitting diode is dominant, a plurality of types of light emitting diodes having different wavelengths are used. It is preferable. Here, in the present specification, a range of 380 nm to 430 nm having a particularly short wavelength among visible light is referred to as a near ultraviolet region, and a light emitting diode having a peak wavelength in the near ultraviolet region is referred to as a near ultraviolet light emitting diode.
(C) Furthermore, it is preferable to use a plurality of types of phosphors in order to emit light in a wide wavelength range from blue to red except for a short wavelength range where light from the light emitting diode is dominant.

The standard light source 1 in the spectral radiation measurement apparatus of the embodiment is configured based on the concept described above, and an example thereof is shown in FIG. 3B.
A standard light source 1 shown in FIG. 3B includes four near-ultraviolet light-emitting diodes 1a having a peak wavelength of 380 nm, twelve near-ultraviolet light-emitting diodes 1b having a peak wavelength of 390 nm, and 10 having a peak wavelength of 400 nm. A plurality of near ultraviolet light emitting diodes 1c and four near ultraviolet light emitting diodes 1d having a peak wavelength of 410 nm are mounted. Of the 30 near ultraviolet light emitting diodes, 15 near ultraviolet light emitting diodes (2 near ultraviolet light emitting diodes 1a, 6 near ultraviolet light emitting diodes 1b, 5 near ultraviolet light emitting diodes 1c, 2 Near ultraviolet light emitting diodes 1d) are connected in series, the remaining 15 near ultraviolet light emitting diodes are connected in series, and the two series circuits are connected in parallel. Here, the near-ultraviolet light-emitting diodes each have a p-side electrode and an n-side electrode on the light-emitting surface side, and adjacent near-ultraviolet light-emitting diodes are connected by a wire 7.
FIG. 3B shows an example using four types of near-ultraviolet light-emitting diodes each having a peak wavelength in the near-ultraviolet region, but the standard light source 1 of the present embodiment has a peak in the ultraviolet region (wavelength region less than 380 nm). You may comprise so that the light emitting diode which has a wavelength may be included. Examples of the near-ultraviolet light emitting diode or the light emitting diode having a peak wavelength in the ultraviolet region include a light emitting diode made of a nitride semiconductor such as AlGaN.

  In the standard light source 1 of the embodiment, the phosphor layer is provided so as to cover the 30 near-ultraviolet light emitting diodes, and the phosphor layer emits the first phosphor that emits blue light and the first phosphor that emits yellow light. 2 phosphors and a third phosphor that emits red light. Here, in the standard light source 1 of the embodiment, one or more of the first to third phosphors or each of them may include two or more types of phosphors.

  The standard light source 1 of the embodiment further includes a translucent resin that covers the near-ultraviolet light emitting diode and the phosphor layer. This translucent resin preferably contains a light diffusing material, whereby the direct light from the light emitting diode and / or the light from the phosphor can be diffused and made uniform and emitted to the outside. .

  As described above, the standard light source 1 shown in FIG. 3B is attached to the light source attachment portion 11 while being held at a predetermined position of the folder 5 shown in FIG. 3A. The folder 5 is provided with a Peltier element 3 that cools the standard light source 1 and suppresses the temperature rise of the standard light source 1 during operation.

  Based on the example shown in FIG. 3B above, the A type standard light source 1 and the B type standard light source 1 are produced, and the spectral radiation measuring apparatus of the embodiment using the A type standard light source 1 and the B type standard light source are used. The measurement error in the wavelength region of 380 nm to 780 nm was evaluated by the above formula (5) for each of the spectral radiation measurement apparatuses of the embodiment using 1. In the evaluation of this measurement error, the slit wavelength width Δλ was 5 nm.

here,
A type standard light source 1 is
As a near ultraviolet light emitting diode, as described above,
Four near ultraviolet light emitting diodes 1a having a peak wavelength of 380 nm;
12 near-ultraviolet light emitting diodes 1b having a peak wavelength of 390 nm;
10 near-ultraviolet light emitting diodes 1c having a peak wavelength of 400 nm;
Four near-ultraviolet light emitting diodes 1d having a peak wavelength of 410 nm;
Use
As a first phosphor that emits blue light, a phosphor (SCA) represented by (SrCaBaMg) ₅ (PO ₄ ) ₃ Cl: Eu is used,
As a second phosphor that emits yellow light, a phosphor (LAG) represented by Lu ₃ Al ₅ O ₁₂ : Ce is used,
As a third phosphor that emits red light, a phosphor (CASN) represented by CaAlSiN ₃ : Eu was used.

The B type standard light source 1 is
As a near ultraviolet light emitting diode, as described above,
Four near ultraviolet light emitting diodes 1a having a peak wavelength of 380 nm;
12 near-ultraviolet light emitting diodes 1b having a peak wavelength of 390 nm;
10 near-ultraviolet light emitting diodes 1c having a peak wavelength of 400 nm;
Four near-ultraviolet light emitting diodes 1d having a peak wavelength of 410 nm;
Use
As the first phosphor that emits blue light, _BaMgA l0 _O 17: phosphor represented by Eu phosphors (BAM) used,
As a second phosphor that emits yellow light, a phosphor (LAG) represented by Lu ₃ Al ₅ O ₁₂ : Ce is used,
As a third phosphor that emits red light, a phosphor (CASN) represented by CaAlSiN ₃ : Eu was used.

  The A-type standard light source 1 and the B-type standard light source 1 are configured in the same manner except that the material of the first phosphor that emits blue light is different.

FIG. 4A shows the spectral distribution of the A type standard light source 1 and the spectral distribution of the B type standard light source 1. FIG. 4B shows the measurement error of the spectral radiation measurement apparatus using the A type standard light source 1 and the measurement error of the spectral radiation measurement apparatus using the B type standard light source 1.
4A and 4B respectively show the spectral distribution of the white LED and the standard light bulb, and the measurement error of the spectral radiation measurement apparatus using the white LED and the standard light bulb as a standard light source.

  As shown in FIG. 4B, the measurement error of the spectral radiation measurement apparatus using the A type standard light source 1 and the measurement error of the spectral radiation measurement apparatus using the B type standard light source 1 are both in the wavelength range of 380 nm to 780 nm. It was confirmed that it can be reduced to 4% or less. This measurement error is an error when the slit wavelength width Δλ is 5 nm. For example, if the slit wavelength width Δλ is 2.5 nm or less, it means that the measurement error can be 1% or less. It can be used as a standard light source.

  As described above, the standard light source satisfying the formula (1) necessary for reducing the measurement error to 1% or less in the spectroradiometer having the spectroscope having the slit wavelength width Δλ of 2.5 nm used as standard. It has been shown by the A type and B type standard light sources 1 of the present embodiment that can be realized by a light source combining a light emitting diode and a phosphor.

  In the above, an example of a standard light source that replaces the standard light bulb with the A type and B type standard light sources 1 having a specific structure has been shown. Spectral radiation by appropriately changing the type of light emitting diode, the type of phosphor, and a combination thereof. It goes without saying that a light source that can be used as a standard light source in the measuring apparatus, that is, a standard light source that satisfies the formula (1) can be realized.

For example, the A type and B type standard light sources 1 are configured using four types of near ultraviolet light emitting diodes having different peak wavelengths. For example, one or a plurality of ultraviolet light emitting diodes in the ultraviolet region having a peak wavelength of 380 nm or less are used. The standard light source may be configured by using one kind or a plurality of kinds of phosphors that emit visible light when excited by ultraviolet light.
For example, the standard light source 1 can include two or more types of light emitting diodes having different peak wavelengths (for example, four types of light emitting diodes having different peak wavelengths) in the range of 360 nm to 430 nm.

  Moreover, the standard light source 1 can also be comprised including 1 or more types of light emitting diodes in the range of 360 nm-380 nm. In this way, it is possible to realize a standard light source in which the light emission of the phosphor is dominant in the required measurement range of 380 nm to 780 nm. In general, since the spectral distribution of the phosphor is gentler than that of the light emitting diode, it can be easily understood that the second derivative of the spectral distribution can be reduced in the measurement range of 380 nm to 780 nm.

In addition, as described in the background section, when the total luminous flux of solid-state element illumination is measured with a conventional spectral radiation measurement device using a standard bulb, the emission spectrum and light distribution characteristics of the solid-state element illumination are different from those of the standard bulb. In some cases, the total luminous flux cannot be measured accurately due to the large difference.
In this regard, a light source in which a light emitting diode and a phosphor are combined can realize various emission spectra by appropriately changing the type of the light emitting diode, the type of the phosphor and the combination thereof. Various light distribution characteristics can be realized by appropriately changing the shape of the light-transmitting resin that covers the light emitting diode and the phosphor. Therefore, it is possible to realize a standard light source suitable for the light emission spectrum and light distribution characteristics of the light source to be measured, and to reduce measurement errors due to differences in the light emission spectrum and light distribution characteristics.

  In the spectral radiation measuring apparatus of the above embodiment, the example using the integrating sphere 10a as the light introducing means to the spectroscope 20 has been described. However, the present invention is not limited to this, and the standard light source and the light source to be measured Can be used as light introducing means as long as the light from the light source can be incident on the spectroscope 20 in a state of being equalized regardless of the direction and distance from the light source.

For example, in addition to using an integrating sphere as the light introducing means that can be used in the spectral radiation measurement apparatus of the embodiment,
(I) JISZ8724, Annex C. 1, means for vertically irradiating light from a light source to the diffuse reflection surface defined in condition b, and introducing diffuse reflection light in a 45 ° direction from the normal line of the diffuse reflection surface;
(Ii) JISZ8724, Appendix C. 1, means for introducing the diffused transmitted light against the diffused transmission surface defined in condition c.
In this specification, diffuse reflection light and diffuse transmission light incident on the spectroscope are collectively referred to as diffuse light.

DESCRIPTION OF SYMBOLS 1 Standard light source 1a, 1b, 1c, 1d Near-ultraviolet light emitting diode 3 Peltier element 5 Folder 7 Wire 10 Light introduction part 10a Integrating sphere 11 Light source attachment part 12 Output part 13 Light-shielding plate 14 Light source for self-absorption correction 20 Spectrometer 21 Incident slit Plate 21s Entrance slit 22 Dispersing means 23 Exit slit plate 23s Exit slit 22M1, 22M2 Planar mirror 22Mc Collimator mirror 22G Diffraction grating 22Mf Focusing mirror 30 Detector

Claims (5)

An entrance slit; a dispersion unit that changes an exit angle of incident light incident from the entrance slit according to a wavelength; and an exit slit that emits light in a specific wavelength band among the light dispersed by the dispersion unit. A spectroscope equipped with,
Light introducing means for irradiating the incident slit with light emitted from the light source to be measured as diffused light;
A standard light source as a reference for spectral distribution measurement;
With
The standard light source includes a light emitting diode and a phosphor excited by light from the light emitting diode,
A spectral distribution Ps (λ) of the standard light source, a second derivative Ps ″ (λ) of the spectral distribution Ps (λ), a width of the entrance slit, a dispersion characteristic of the dispersion means, and a width of the exit slit. A spectral radiation measurement apparatus characterized in that the wavelength width Δλ (nm) of the slit function defined based on the above satisfies the relationship of the following formula (1) in a wavelength range of 380 nm to 780 nm.

Δλ ² × ( | Ps ″ (λ) | / Ps (λ)) <0.5 (1)
The light emitting diode has a peak wavelength in the ultraviolet to near ultraviolet region,
The phosphor is
A first phosphor that emits blue light when excited;
A second phosphor that emits yellow light when excited;
And a third phosphor that emits red light when excited. 2. The spectral radiation measuring apparatus according to claim 1, wherein:   The spectral radiation measuring apparatus according to claim 2, wherein the first phosphor includes two different kinds of phosphors.   4. The spectral radiation measurement apparatus according to claim 1, wherein the light emitting diode includes two or more types of light emitting diodes having different peak wavelengths in a range of 360 nm to 430 nm.   4. The spectral radiation measurement apparatus according to claim 1, wherein the light emitting diode includes four types of light emitting diodes having different peak wavelengths in a range of 360 nm to 430 nm.