JP2010112807A - Optical power meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical power meter for correctly measuring optical power of light to be tested by positively or negatively inclining a spectral sensitivity characteristic of an optical sensor means to a wavelength. <P>SOLUTION: The optical power meter includes: the optical sensor means 11 formed with an array of a plurality of optical sensors S having different spectral sensitivity characteristics whose sensitivity wavelength regions are limited; and a control means 103 for obtaining the optical power based on a signal from the optical sensor means. The control means 103 implements: (a) a weighting operation corresponding to the spectral sensitivity characteristic of different optical sensor, obtains a first optical sensor means A in which the spectral sensitivity characteristic Ra(λ) of the optical sensor is approximately represented as a formula (1): Ra(λ)=aλ+b and a second optical sensor means B in which the spectral sensitivity characteristic Rb(λ) of the optical sensor is approximately represented as a formula (2): Rb(λ)=cλ+d in a wavelength region within a predetermined range ; and (b) obtains a barycentric wavelength of light to be tested from output signals Sa, Sb of the first and second optical sensor means A, B, and calculates the optical power from the barycentric wavelength. The output signals Sa, Sb are represented as a formula (3): Sa=P1*Ra(λ1)+P2*Ra(λ2), and a formula (4): Sb=P1*Rb(λ1)+P2*Rb(λ2). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical power meter that measures the power of light from a fluorescent lamp, light bulb, LED illumination, LED element, LD, LCD (liquid crystal display) or the like as a light source.

  Conventionally, various devices have been proposed as an optical power meter that measures the power of light (light under test) from a light source to be measured such as a fluorescent lamp, a light bulb, and an LED element.

  When the wavelength of the light under test is unknown, the optical power can be measured using an expensive measuring instrument such as an optical spectrum analyzer or a spectroradiometer.

  Further, as an inexpensive configuration, there is an optical power meter that uses an optical sensor using a quantum semiconductor element such as a silicon photodiode having different sensitivity characteristics with respect to a wavelength as a light receiving element.

  Therefore, in such a power meter, in order to accurately measure the optical power, it is necessary to set the wavelength of the light under test to be measured in the device and correct the spectral sensitivity characteristic of the optical sensor for measurement.

  Therefore, in Patent Document 1, as shown in FIGS. 6 to 8 attached to the present application, light receivers A and B as optical sensor means are provided without measuring the wavelength of the light under test from the light source 1 to be measured. An optical power meter that can measure the optical power incident on the aperture 2 with a configuration of two is disclosed.

  That is, in this optical power meter, the light to be tested incident on the aperture 2 is diffused by the diffusion transmission plate 3, and the two light receivers A and B having the glass filter f and the silicon photodiode PD and having different sensitivities are used. To detect.

  Next, light is converted into electricity by the silicon photodiode PD, converted into voltage by the IV conversion circuits (arithmetic circuit and feedback resistor) 4 and 5, and then AD converted by the analog switch 6 by the A / D converter 7 alternately. Then, the data is taken into the CPU 8.

Two light receivers having different sensitivities, that is, the spectral sensitivity characteristic R (λ) has a positive inclination with respect to the wavelength, that is, the light receiver A with Ra (λ) = aλ + b, and a negative inclination, , Rb (λ) = cλ + d is obtained from the output from the light receiver B, the center-of-gravity wavelength λx of the light under test is obtained, and the optical power is measured.
JP 63-127127 A

  In the optical power meter disclosed in Patent Document 1, the sensitivity of the spectral sensitivity characteristics of the two light receivers A and B must change linearly with respect to the wavelength. If this inclination is distorted, a measurement error occurs.

  In general, the optical sensor S for an optical power meter includes an optical filter f and a light receiving element (silicon photodiode) PD.

  However, in general, it is difficult for the colored glass filter of the optical filter f to obtain a characteristic in which the spectral transmittance changes linearly in a relatively broad wavelength range of 400 nm to 700 nm, for example. In addition, the sensitivity gradient of the light receiving element PD is not constant with respect to the wavelength. For example, the sensitivity gradient with respect to the wavelength is different in the wavelength range of 400 nm and the wavelength of 700 nm.

  Further, in the case of mass production of optical sensors, if variations occur in the spectral transmission characteristics of the optical filters and the spectral sensitivity characteristics of the light receiving elements, the variations cannot be corrected due to the configuration.

  Therefore, it is difficult to measure the optical power with high accuracy by the conventional method.

  An object of the present invention is to provide an optical power meter that can accurately measure the optical power of light under test by tilting the spectral sensitivity characteristic of the optical sensor means positively or negatively with respect to the wavelength.

The above object is achieved by an optical power meter according to the present invention. In summary, the present invention provides an optical power meter including a detection unit including an optical sensor unit having sensitivity characteristics in a wavelength range of a predetermined range, and a measurement unit that calculates optical power based on a light reception signal from the detection unit. In
The optical sensor means includes an optical filter and a light receiving element, and is configured by arranging a plurality of optical sensors each having a different spectral sensitivity characteristic in which a sensitivity wavelength region is limited,
The measurement unit includes control means for obtaining optical power based on a signal from the optical sensor means,
The control means includes
(A) Weighting is performed corresponding to the spectral sensitivity characteristics of the different optical sensors, and the spectral sensitivity characteristics of the optical sensors are approximately expressed by Ra (λ) = aλ + b in the wavelength range of the predetermined range. A first photosensor means A represented, and a second photosensor means B approximately represented by the formula Rb (λ) = cλ + d (a ≠ c),
(B) Next, the centroid wavelength of the light under test is obtained from the output signals Sa and Sb of the first optical sensor means A and the second optical sensor means B, and the optical power is calculated from the centroid wavelengths. ,
This is an optical power meter.

According to an embodiment of the present invention, when the optical power is P, the optical power P is represented by the following formula:
P = Sa / {a (d.Sa/Sb-b) / (ac-Sa / Sb) + b}
Is required.

  According to another embodiment of the present invention, the detection unit includes a housing in which the optical sensor means is installed, and the housing has an incident portion opening through which light under test enters. A diffusion plate is provided in the entrance opening.

According to another embodiment of the invention,
The control means of the measuring unit is
An I / V conversion amplifier that converts a current signal, which is a light reception signal from the optical sensor means, into a voltage; an A / D converter that converts a light reception signal from the I / V conversion amplifier into a digital value; First storage means for storing the received light signal converted by the D converter, and second storage means for storing the weighting coefficient,
Using the received light signal stored in the first storage means and the weighting coefficient stored in the second storage means, the sensitivity characteristics of the photosensors are weighted and added together to add together. The first photosensor means A or the second photosensor means B having a characteristic in which the spectral sensitivity characteristic of the subsequent photosensor is inclined in a positive or negative direction with respect to a predetermined wavelength range can be formed. .

  According to the present invention, the optical power of the light under test can be accurately measured by tilting the spectral sensitivity characteristic of the optical sensor means positively or negatively with respect to the wavelength.

  Hereinafter, the optical power meter according to the present invention will be described in more detail with reference to the drawings.

Example 1
The measurement principle of the optical power meter of the present invention is the same as the technique described in Patent Document 1 described in the section of “Background Art”, but briefly described again with reference to FIG. It is.

(Measurement principle)
In FIG. 8, the optical power meter includes two light receivers whose spectral sensitivity characteristics are inclined positively or negatively with respect to the wavelength, that is, a first light receiver A and a second light receiver B.

The spectral sensitivity characteristics Ra (λ) and Rb (λ) of the first light receiver A and the second light receiver B are as follows:
Ra (λ) = aλ + b (1)
Rb (λ) = cλ + d (a ≠ c) (2)
It is expressed. When the first light receiver A and the second light receiver B receive beams of two bright lines having wavelengths of λ1 and λ2 and radiation (light) powers of P1 and P2, the first and second light receivers A and B respectively. , B output signals Sa, Sb are:
Sa = P1 · Ra (λ1) + P2 · Ra (λ2) (3)
Sb = P1 · Rb (λ1) + P2 · Rb (λ2) (4)
It is represented by

Since Ra (λ) and Rb (λ) are straight lines, a centroid wavelength λx represented by the following equation exists between λ1 and λ2 according to the ratio of P1 and P2.
λx = λ1 + P2 (λ2−λ1) / (P1 + P2) (5)
From the above formulas (3), (4), (5),
Sa = (P1 + P2) (aλx + b) (6)
Sb = (P1 + P2) (cλx + d) (7)
Is obtained.

Here, the ratio k of the output signals Sa and Sb of the first and second light receivers A and B is taken,
k = Sa / Sb (8)
From the above formulas (6) and (7),
k = (aλx + b) / (cλx + d) (9)
And this equation can be transformed and
λx = (kd−b) / (a−kc) (10)
Λx can be derived from the ratio k of the light receiver. If λx is obtained, the above equation (6) is used.
P1 + P2 = Sa / (aλx + b)
= Sa / {a (d.Sa/Sb-b) / (ac-Sa / Sb) + b} (11)
The total of incident (light) power can be obtained from the readings Sa and Sb of the output signals of the respective light receivers without the need to know the individual values of P1, P2, λ1, and λ2.

(Whole optical power meter configuration)
An embodiment of an optical power meter 1 according to the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram showing an embodiment of an electrical configuration of the optical power meter 1 in the present embodiment, and FIG. 2 shows a configuration of a detection unit 10 including an optical sensor means 11.

  According to the present embodiment, the optical power meter 1 includes a detection unit 10 and a measurement unit 100. The detection unit 10 includes a housing (casing) 12 in which an optical sensor means 11 is installed. In this embodiment, the detection unit 10 is located on the left side and receives light (light under test) from a light source to be measured. An incident portion opening 13 is provided. In addition, a diffusion plate 14 is installed in the entrance opening 13. The operation of the diffusion plate 14 will be described later.

  The optical sensor means 11 disposed inside the casing 12 is provided with a plurality of optical sensors S (S1, S2, S3,...) In order to detect light diffused by the diffusion plate 14 from the entrance opening 13. Sn-2, Sn-1, Sn). Each optical sensor S includes an optical filter f (f1, f2, f3,... Fn-2, fn-1, fn) and a light receiving element (photoelectric conversion element) PD (PD1, PD2, PD3,... PDn-2, PDn-1, PDn), and each optical sensor S has a limited sensitivity wavelength region.

  That is, according to the present invention, each of the individual optical sensors S1, S2, S3,... Sn-2, Sn-1, and Sn constituting the optical sensor means 11 is shown in FIG. Spectral sensitivity characteristics S′1 (λ), S′2 (λ), S′3 (λ),... S′n−2 (λ), S′n−1 (λ), S′n ( λ). That is, the spectral sensitivity characteristics S′1 (λ), S′2 (λ), S′3 (λ),... S′n−2 (λ), S′n−1 of the individual optical sensors S (Λ) and S′n (λ) have bandpass characteristics. The spectral sensitivity characteristic S ′ of each optical sensor S is obtained by measuring each optical sensor using a spectroscopic means after the optical sensor S is incorporated in the optical power meter.

  Accordingly, a wavelength range that is a predetermined range of the optical sensor means 11 in a plurality of optical sensors S1, S2, S3,... Sn-2, Sn-1, Sn, for example, a detection wavelength of 400 to 600 nm. It constitutes an area.

  Referring to FIG. 1, in this embodiment, the optical power meter 1 includes a plurality of optical sensors S (S1, S2, S3,... Sn-2, Sn-1, Sn that constitute the detection unit 10 described above. ) Is transmitted to the measuring unit 100. The measurement unit 100 includes an I / V conversion amplifier (all gains are equal) 101 that converts a received light signal (current signal) into a voltage, and an A / D conversion that converts a received light signal from the I / V conversion amplifier 101 into a digital value. And a control means (CPU) 103 that receives the light reception signal converted by the A / D converter 102, calculates the optical power, and displays it on the display means 106.

  According to the present embodiment, the control unit 103 stores the light reception signal transmitted from the A / D converter 102 in the RAM (first storage unit) 104, the light reception signal stored in the RAM 104, and Using the weighting coefficient stored in the ROM (second storage means) 105, weighting is performed corresponding to the spectral sensitivity characteristic of each photosensor S, and the addition is performed. Thereby, the optical sensor means can be configured so that the spectral sensitivity characteristics of the combined optical sensor have desired characteristics with respect to a predetermined wavelength range.

According to the present embodiment, at this time, depending on the setting method of the weighting coefficient, the spectral sensitivity characteristic of the photosensor after the summation is in a wavelength range of a predetermined range,
(A) first optical sensor means A having a linear sensitivity characteristic (see FIG. 4) inclined in the positive direction;
(B) second optical sensor means B having a linear sensitivity characteristic (see FIG. 5) inclined in the negative direction;
Is configured.

That is, the spectral sensitivity characteristic SΣ (λ) of the photosensor after the summation is
SΣ (λ) = k1 · S′1 (λ) + k2 · S′2 (λ) +... + KnS′n (λ)
It is represented by k1 to kn are weighting coefficients.

  Due to the first weighting, the spectral sensitivity characteristic SΣ (λ) of the optical sensor S after the addition has a first characteristic Ra (λ) (see FIG. 4) inclined in the positive direction with respect to a predetermined range of wavelength region. The optical sensor means A is formed. In addition, due to the second weighting, the spectral sensitivity characteristic SΣ (λ) of the optical sensor S after the addition has a characteristic Rb (λ) (see FIG. 5) that is inclined in the negative direction with respect to a predetermined wavelength range. Second optical sensor means B is formed.

That is, the spectral sensitivity characteristics Ra (λ) and Rb (λ) of the first and second photosensor means A and B are approximately,
Ra (λ) = aλ + b
Rb (λ) = cλ + d (a ≠ c)
It is represented by

  In this embodiment, the power meter 1 has 16 optical sensors S as the optical sensor means 11. Each photosensor S uses a silicon photodiode as the light receiving element PD. The spectral sensitivity characteristics S′1 (λ), S′2 (λ), S′3 (λ),..., S′16 (λ) (n = 16) of each optical sensor S in this embodiment are illustrated. It is shown in 3.

  That is, according to the present embodiment, the optical sensor means 11 having 16 optical sensors S outputs 16 received light signals having peaks at a pitch of 16 nm from 420 nm to 580 nm as shown in FIG. Note that the number of the optical sensors S is not limited to 16, but may be other numbers if desired.

  FIG. 4 and FIG. 5 show an example of the spectral sensitivity characteristic SΣ (λ) of the optical sensor S after the light receiving signals are weighted corresponding to the spectral sensitivity characteristics of the optical sensor S and added together.

  From FIG. 4, according to the first optical sensor means A of the optical power meter 1 of the present embodiment, it was confirmed that it had a linear characteristic inclined in the positive direction in the wavelength range of 420 nm to 580 nm. Moreover, according to FIG. 5, according to the 2nd optical sensor means B of the optical power meter 1 of a present Example, it has confirmed that it had the linear characteristic inclined in the negative direction in the wavelength range of 420 nm-580 nm.

  As described above, in this embodiment, as shown in FIG. 2, the diffusion plate 14 is installed in the incident portion opening 13 of the casing 12. The operation of the diffusion plate 14 will be described.

  When the incident angle (θ) at which the light under test enters the detector 10 changes extremely, the light distribution is biased.

  According to the present invention, as described above, the optical sensor means 11 is composed of a plurality of optical sensors S1, S2,. Therefore, when the incident angle (θ) of the light under test changes to the detection unit 10 extremely and the light distribution is biased, a plurality of optical sensors S1, S2,. -The light quantity on Sn changes and a measured value changes.

  Therefore, in this embodiment, the diffusion plate 14 is fixed to the incident part opening 13 so as to cover the entire area of the incident part opening 13. As the diffusion plate 14, an opal type diffusion plate (trade name: manufactured by Sigma Koki Co., Ltd.) is preferably used.

  According to the present embodiment, by fixing the diffusion plate 14 to the incident portion opening 13 of the casing 12, the light to be tested incident on the detection portion 10 is diffused and incident, and the incident angle (θ) of the light to be tested changes. Even so, the distribution of the light beam applied to each optical sensor S having a different transmission wavelength is uniform and uniform.

  Therefore, according to the optical power meter 1 of the present embodiment, it is possible to measure the power and chromaticity of the light under test with high accuracy even when the incident angle of the light under test changes.

(Optical power measurement)
As described above, the measurement principle of the optical power meter of the present invention is the same as the technique described in Patent Document 1 described with reference to FIGS. That is, in the above description, by replacing the first light receiver A and the second light receiver B with the first light sensor means A and the second light sensor means B in the present embodiment, respectively, The measurement principle of this example will be understood.

That is, in the present embodiment, the control means 103 for obtaining the optical power based on the signal from the optical sensor means 11 provided in the measuring unit 100 of the optical power meter is:
(A) Weighting is performed corresponding to the spectral sensitivity characteristics of the different optical sensors, and the spectral sensitivity characteristics of the optical sensors are approximately expressed by the formula Ra (λ) = aλ + b in the wavelength range of the predetermined range. First optical sensor means A and second optical sensor means B approximately expressed by the equation Rb (λ) = cλ + d,
(B) Next, the centroid wavelength of the light under test is obtained from the output signals Sa and Sb of the first optical sensor means A and the second optical sensor means B, and the optical power P is calculated from the centroid wavelength. .

The optical power P is expressed by the following formula:
P = Sa / {a (d.Sa/Sb-b) / (ac-Sa / Sb) + b}
Is required.

  Thus, according to the present invention, the optical power of the light under test can be accurately measured by tilting the spectral sensitivity characteristic of the optical sensor means positively or negatively with respect to the wavelength.

It is a block diagram which shows the electrical constitution of one Example of the optical power meter which concerns on this invention. It is a schematic block diagram of one Example of the detection part of the optical power meter which concerns on this invention. It is a figure which shows the relative spectral sensitivity characteristic of each optical sensor which comprises an optical sensor means. It is a figure which shows the relative spectral sensitivity characteristic after the summation of each optical sensor which comprises the 1st optical sensor means A. It is a figure which shows the relative spectral sensitivity characteristic after the summation of each photosensor which comprises the 2nd photosensor means B. FIG. It is a figure which shows an example of the conventional optical sensor. It is the schematic which shows the electrical structure of the conventional optical power meter. It is a figure explaining the measurement principle of the conventional optical power meter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical power meter 10 Detection part 11 Optical sensor means 11A 1st optical sensor means 11B 2nd optical sensor means 12 Casing (housing | casing)
13 entrance aperture 14 diffuser plate 100 measuring unit 101 A / D converter 102 control means 103 RAM (first storage means)
104 ROM (second storage means)
105 Display means f Optical filter PD Light receiving element S Optical sensor

Claims (4)

In an optical power meter including a detection unit including an optical sensor means having sensitivity characteristics in a wavelength region of a predetermined range, and a measurement unit that calculates optical power based on a light reception signal from the detection unit,
The optical sensor means includes an optical filter and a light receiving element, and is configured by arranging a plurality of optical sensors having different spectral sensitivity characteristics, each of which has a limited sensitivity wavelength region,
The measurement unit includes control means for obtaining optical power based on a signal from the optical sensor means,
The control means includes
(A) Weighting is performed corresponding to the spectral sensitivity characteristics of the different optical sensors, and the spectral sensitivity characteristics of the optical sensors are approximately expressed by the equation Ra (λ) = aλ + b in the wavelength range of the predetermined range. A first photosensor means A represented, and a second photosensor means B approximately represented by the formula Rb (λ) = cλ + d (a ≠ c),
(B) Next, the centroid wavelength of the light under test is obtained from the output signals Sa and Sb of the first optical sensor means A and the second optical sensor means B, and the optical power is calculated from the centroid wavelengths. ,
An optical power meter characterized by that. When the optical power is P, the optical power P is expressed by the following formula:
P = Sa / {a (d.Sa/Sb-b) / (ac-Sa / Sb) + b}
The optical power meter according to claim 1, wherein the optical power meter is obtained by:   The detector has a housing in which the optical sensor means is installed, and the housing is provided with an entrance opening through which the light to be tested is incident, and the entrance opening has a diffuser plate. The optical power meter according to claim 1, wherein the optical power meter is installed. The control means of the measuring unit is
An I / V conversion amplifier that converts a current signal, which is a light reception signal from the optical sensor means, into a voltage; an A / D converter that converts a light reception signal from the I / V conversion amplifier into a digital value; First storage means for storing the received light signal converted by the D converter, and second storage means for storing the weighting coefficient,
Using the received light signal stored in the first storage means and the weighting coefficient stored in the second storage means, the sensitivity characteristics of the photosensors are weighted and added together to add together. It is possible to form the first photosensor means A or the second photosensor means B having a characteristic in which the spectral sensitivity characteristic of the subsequent photosensor is inclined in a positive or negative direction with respect to a predetermined wavelength range. The optical power meter according to any one of claims 1 to 3.

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