JP2013152145A - Optical inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical inspection device which can inspect a chromaticity value appropriately.SOLUTION: According to the present invention, an optical inspection device 10 includes: a calibration unit 13 which performs an arithmetic calculation, so as to calibrate a light intensity of each wavelength measured by a spectrum measurement unit 12; a chromaticity conversion unit 14 which converts a light intensity of each wavelength, calibrated by the calibration unit 13, to a chromaticity value; and a determination unit 15 which compares the chromaticity value obtained by conversion performed at the chromaticity conversion unit 14 with a predetermined inspection reference, so as to determine whether a light emitting product is good or not. The calibration unit 13 includes: a multiplication constant calculation unit 131 which calculates, before inspection of the light emitting product, a multiplication constant using a known light intensity of a reference light source and a measurement light intensity that is obtained when the reference light source is measured by the spectrum measurement unit 12; a difference calculation unit 132 which performs a calculation for each wavelength, before inspection of the light emitting product, to find a difference value between the known light intensity of the reference light source and the measurement light intensity multiplied by the multiplication constant; and an addition calculation unit 133 which multiplies, before inspection of the light emitting product, a light intensity of the light emitting product, measured by the spectrum measurement unit 12, by the multiplication constant and adds the difference value thereto.

Description

  The present invention relates to an optical inspection apparatus, and more particularly to an optical inspection apparatus that calibrates a measurement error by numerical calculation processing.

  It is said that the chromaticity difference that can be identified by human eyes is about ± 0.01 in chromaticity coordinates (x, y) in the case of white. In white LEDs (Light Emitting Diodes), manufacturing variations due to variations in the wavelength and intensity of excitation light, variations in the amount of phosphor applied, and the like are currently larger than this. Therefore, in white LED production factories and application factories such as liquid crystal televisions using white LEDs, the quality is controlled by inspecting the chromaticity values of the white LEDs at high speed. An optical inspection apparatus is used for such inspection.

  In the optical inspection device, the light intensity for each wavelength of the light emitting product to be inspected is measured, and the chromaticity value is calculated from the light intensity for each wavelength based on a known conversion formula. As chromaticity values, tristimulus values X, Y, Z and chromaticity coordinates (x, y) in the XYZ color system are generally used. The quality of the luminescent product is determined based on whether or not the obtained chromaticity value satisfies a predetermined inspection standard.

  Hereinafter, a method for calculating the chromaticity coordinates (x, y) from the light intensity for each wavelength will be briefly described with reference to FIGS.

FIG. 9 is a diagram illustrating the light intensity for each wavelength of the white LED.
A white LED having a light intensity I (λ) (λ is a wavelength) shown in FIG. 9 uses a semiconductor element that emits blue light and a phosphor that converts blue excitation light into green or red. is there. The light intensity I (λ) is obtained by dividing the wavelength range of 380 nm to 780 nm into 1 nm widths, has a steep peak near the blue range of 440 nm, and the green range of around 530 nm and the red range. It has a relatively gentle peak near a certain 640 nm.

FIG. 10 is a diagram showing the color matching functions x (λ), y (λ), z (λ) of the XYZ color system.
FIG. 11 is a diagram illustrating a calculation process for obtaining tristimulus values X, Y, and Z of the XYZ color system.

  The three functions {I (λ) × x (λ)}, {I (λ) × y (λ)}, and {I (λ) × z (λ)} shown in FIG. 11 are the wavelengths shown in FIG. Each light intensity I (λ) is multiplied by the color matching function x (λ), y (λ), z (λ) shown in FIG. 10 for each wavelength. The tristimulus values X, Y, and Z of the XYZ color system are the functions {I (λ) × x (λ)}, {I (λ) × y (λ)}, and {I (λ) × z, respectively. By integrating (λ)} with respect to the wavelength, the following equations (1a) to (1c) are obtained. k is a constant given by 683 lm / W.

X = k∫ {I (λ) × x (λ)} dλ (1a)
Y = k∫ {I (λ) × y (λ)} dλ (1b)
Z = k∫ {I (λ) × z (λ)} dλ (1c)
Between the tristimulus values X, Y, and Z of the XYZ color system and the chromaticity value x and chromaticity value y in the chromaticity coordinates (x, y), the following equations (2a) and (2b) are obtained. It holds.

x = X / (X + Y + Z) (2a)
y = Y / (X + Y + Z) (2b)
In order to inspect the chromaticity value thus obtained with high accuracy, it is necessary to calibrate the optical inspection apparatus using a reference light source.

  Specifically, Patent Document 1 discloses a spectroscopic measurement apparatus that performs calibration using a reference light source. In the spectroscopic measurement device described in Patent Document 1, when the light intensity for each known wavelength and the reference light source are measured with the spectroscopic measurement device using a reference light source for calibration whose light intensity for each wavelength is known The spectral sensitivity of each light receiving element is obtained by solving an equation established between the output voltage and the output voltage of the light receiving unit obtained in the above and used for calibration.

JP-A-62-2899736

  The light intensity for each wavelength (hereinafter referred to as known light intensity P (λ)) obtained by measuring a reference light source having a known light intensity for each wavelength with a high-accuracy spectroscopic measurement device has a small measurement error and is reliable. Because it is considered high, it is used as the standard for calibration of optical inspection equipment.

  By comparing the light intensity at each wavelength obtained by measuring the reference light source with the optical inspection apparatus (hereinafter referred to as measured light intensity Q (λ)) with the known light intensity P (λ) as a reference, the optical inspection apparatus The error of the spectroscopic measurement unit can be extracted.

  In the conventional optical inspection apparatus as shown in Patent Document 1, the ratio of the light intensity at each wavelength is used as a method for comparing the measured light intensity Q (λ) with the known light intensity P (λ). The ratio of the light intensity at each wavelength is determined as a proportional coefficient α (λ) as shown in the following equation (3).

α (λ) = P (λ) / Q (λ) (3)
When measuring a luminescent product, the proportionality coefficient α (λ) obtained using a reference light source is used to determine the light intensity for each wavelength obtained by measuring the luminescent product with an optical inspection device (hereinafter referred to as luminescent product light intensity R ( λ))) is multiplied for each wavelength to calibrate. The light intensity Rα (λ) after calibration is expressed by the following equation (4).

Rα (λ) = α (λ) × R (λ) (4)
However, since the conventional optical inspection apparatus calibrates using only the proportionality coefficient α (λ) depending on the wavelength, when inspecting a light emitting product whose light intensity changes sharply depending on the wavelength, such as a white LED, The error sometimes became rather large. The optical inspection device has a problem that the chromaticity value of the luminescent product cannot be properly inspected if the error becomes large due to calibration and the non-defective product is determined to be defective or the defective product is determined to be non-defective. there were.

  Therefore, the present invention has been made to solve the above-described problems, and provides an optical inspection device capable of calibrating so that the chromaticity value of a luminescent product can be appropriately inspected. With the goal.

  In order to achieve the above object, according to one aspect of the present invention, an optical inspection device includes a spectroscopic unit that splits light from a light emitting product and a light receiving unit that receives light dispersed by the spectroscopic unit. A calibration unit that calibrates the light intensity for each wavelength measured by the spectroscopic measurement unit by numerical calculation processing, and a chromaticity that converts the light intensity for each wavelength calibrated by the calibration unit into a chromaticity value in chromaticity coordinates. A conversion unit; and a determination unit that compares the chromaticity value converted by the chromaticity conversion unit with a predetermined inspection standard to determine whether the luminescent product is good or bad. The calibration unit includes a multiplication constant calculation unit that calculates a multiplication constant based on the known light intensity of the reference light source and the measurement light intensity obtained when the reference light source is measured by the spectroscopic measurement unit before the light emission product is inspected, and the light emission product Before the inspection, the difference calculation unit that calculates the difference value between the known light intensity of the reference light source and the measured light intensity multiplied by the multiplication constant for each wavelength, and the luminescent product measured by the spectroscopic measurement unit during the luminescent product inspection And an addition operation unit for calibrating the light intensity of the light emitting product by multiplying the light intensity by a multiplication constant and adding the difference value.

Preferably, the multiplication constant is a constant value regardless of the wavelength.
Preferably, the multiplication constant calculation unit calculates the multiplication constant so that the maximum value of the known light intensity of the reference light source matches the maximum value of the measurement light intensity of the reference light source.

Preferably, the light receiving section has a substantially constant light receiving sensitivity for each wavelength.
Preferably, the addition calculation unit does not multiply the light intensity of the luminescent product measured by the spectroscopic measurement unit by a multiplication constant, and the calibration unit calculates the maximum of the known light intensity of the reference light source by the multiplication constant calculated by the multiplication constant calculation unit. The output of the light receiving unit is adjusted so that the value matches the maximum value of the measurement light intensity of the reference light source.

  According to the optical inspection apparatus of the present invention, the multiplication constant is calculated as an error independent of the wavelength among the errors generated between the known light intensity of the reference light source and the light intensity obtained by measurement, and the wavelength The difference value is calculated as an error that depends on. The optical inspection apparatus according to the present invention calibrates the measured value of the luminescent product using a multiplication constant that does not depend on the wavelength, so that the luminescent product whose light intensity changes sharply according to the wavelength like a white LED can be obtained. Even when inspecting, the chromaticity value of the luminescent product can be appropriately inspected.

It is a block diagram which shows the structure of the optical inspection apparatus which concerns on embodiment of this invention. 5 is an inspection flowchart showing a flow of processing of an inspection method in the optical inspection apparatus according to the embodiment of the present invention. It is a figure which shows the relationship between the light intensity for every known wavelength of a reference | standard light source, and the light intensity for every wavelength obtained when a reference | standard light source is measured with the optical inspection apparatus which concerns on embodiment of this invention. In the optical inspection apparatus which concerns on embodiment of this invention, it is a figure which shows the difference value calculated | required from the light intensity for every known wavelength of a reference light source, and the light intensity for every wavelength obtained when a reference light source is measured. In the optical inspection apparatus which concerns on embodiment of this invention, it is a figure which shows the relationship between the light intensity for every wavelength of the luminescent product which is a test object, and the light intensity for every wavelength after calibration. It is a figure which shows the error which arises in the process which calculates a tristimulus value in the optical inspection apparatus which concerns on embodiment of this invention. In the optical inspection apparatus which concerns on embodiment of this invention, it is a figure which shows the error of the chromaticity value in the chromaticity coordinate obtained by test | inspecting the luminescent product which is a test object. It is a figure which shows the light reception sensitivity for every wavelength of a spectroscopic measurement part. It is a figure which shows the light intensity for every wavelength of white LED. FIG. 4 is a diagram illustrating color matching functions x (λ), y (λ), and z (λ) of an XYZ color system. It is a figure explaining the calculation process which calculates | requires the tristimulus values X, Y, and Z of an XYZ color system. It is a figure which shows a mode that the proportionality coefficient is dependent on a wavelength in the conventional optical inspection apparatus. In the conventional optical inspection apparatus, it is a figure which shows the relationship between the light intensity for every wavelength of the luminescent product which is a test object, and the light intensity for every wavelength after calibration. It is a figure which shows the error of the chromaticity value in the chromaticity coordinate obtained by test | inspecting the luminescent product which is a test object in the conventional optical inspection apparatus.

(Embodiment)
The light intensity for each wavelength (hereinafter also referred to as spectrum) obtained by inspecting the light source with the optical inspection device includes an error derived from the spectroscopic measurement unit of the optical inspection device (an error of the spectroscopic measurement unit) and a measurer. And errors derived from arbitrarily set measurement conditions (measurement condition errors).

  The error of the spectroscopic measurement unit is the wavelength resolution of the spectroscopic element of the spectroscopic unit, stray light generated by the surface reflection of the spectroscopic element, the spread of the light receiving sensitivity of the light receiving unit of the light receiving unit, the sensitivity variation of the light receiving unit, This is due to variations in the installation of the components. The error of the spectroscopic measurement unit is generally determined at the time of shipment of the optical inspection apparatus.

  Measurement condition errors include light source and light receiving unit installation conditions (position and tilt of light source and light receiving unit, distance and arrangement of light source and light receiving unit, etc.), light source control information (voltage value and limit current value applied to light source) Etc.) and control information of the light receiving unit (such as the exposure time of the light receiving element and the amplification factor of the amplifier). The measurement condition error can be arbitrarily adjusted by the measurer.

  Errors caused by these factors can be distinguished from errors that depend on the wavelength, where the error increases or decreases depending on the wavelength, and errors that do not depend on the wavelength, where a certain error occurs regardless of the wavelength. it can. Note that the constant error regardless of the wavelength is not limited to the case where a constant error occurs in the entire range of the wavelength to be measured, and the range of the wavelength to be measured is divided into a plurality of ranges. It may be a case where a certain error occurs in the range.

  In the optical inspection apparatus according to the embodiment of the present invention, the chromaticity value of the luminescent product is determined by calibrating the value measured for the luminescent product in consideration of the error that does not depend on the wavelength and the error that depends on the wavelength. Provided is an optical inspection device that can be appropriately inspected. Hereinafter, an optical inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an optical inspection apparatus according to an embodiment of the present invention. The light source 1 is a reference light source having a known spectrum or a luminescent product to be inspected. The light emitting product to be inspected is a light emitting element such as a white LED or an applied product using the light emitting element.

  1 includes a control unit 11, a spectroscopic measurement unit 12, a calibration unit 13, a chromaticity conversion unit 14, a determination unit 15, and a data storage unit 16. The spectroscopic measurement unit 12 includes a light guide unit 121, a spectroscopic unit 122, and a light receiving unit 123. The calibration unit 13 includes a multiplication constant calculation unit 131, a difference calculation unit 132, and an addition calculation unit 133. The data storage unit 16 includes a known light intensity storage unit 161, a calibration coefficient storage unit 162, an inspection standard storage unit 163, and a determination result storage unit 164. The calibration coefficient storage unit 162 includes a multiplication constant storage unit 162a and a difference storage unit 162b.

  The control unit 11 controls the voltage value or current value applied to the light source 1, the timing of turning on the power, and the like based on the control information of the light source 1 preset by the measurer, and causes the light source 1 to emit light. Further, the control unit 11 controls the spectroscopic measurement unit 12 based on the control information of the light receiving unit 123 preset by the measurer, and causes the spectroscopic measurement unit 12 to split and receive the light of the light source 1. Furthermore, the control unit 11 controls the spectroscopic measurement unit 12, the calibration unit 13, the chromaticity conversion unit 14, the determination unit 15, and the data storage unit 16 to operate in conjunction with each other such as transmitting and receiving various data.

  The spectroscopic measurement unit 12 splits the light emitted from the light source 1 for each wavelength, converts the obtained spectrum into an electrical signal, and transmits the electrical signal to the calibration unit 13.

  The light guide unit 121 includes a light guide element (not shown) such as an optical fiber. The light guide unit 121 captures light emitted from the light source 1 and guides the captured light to the spectroscopic unit 122 without being attenuated.

  The spectroscopic unit 122 includes spectroscopic elements (not shown) such as a diffraction grating, a prism, and an optical filter, and splits the light taken in through the light guide unit 121.

  The light receiving unit 123 includes a plurality of light receiving elements (not shown) and an amplifier (not shown) arranged such as a photodiode array, and is set in the control unit 11 such as the exposure time of the light receiving elements and the amplification factor of the amplifier. Based on the control information, the light split by the spectroscopic unit 122 is converted into an electrical signal and transmitted to the calibration unit 13.

  The calibration unit 13 calibrates the spectrum by performing various numerical calculation processes on the spectrum of the light source 1 received from the light receiving unit 123.

  The multiplication constant calculator 131 stores the known spectrum of the reference light source (known light intensity of the reference light source) (hereinafter also referred to as known light intensity P (λ)) stored in the known light intensity storage unit 161 and the light receiving unit 123. For obtaining a multiplication constant, which will be described later, for a spectrum (measured light intensity of the reference light source) (hereinafter also referred to as measured light intensity Q (λ)) obtained when the reference light source is measured by the spectroscopic measurement unit 12 do.

  The difference calculation unit 132 uses the multiplication constant stored in the multiplication constant storage unit 162a for the measured light intensity Q (λ) received from the light receiving unit 123 and the known light intensity P (λ) stored in the known light intensity storage unit 161. The difference calculation is performed using and the result is transmitted to the difference storage unit 162b.

  The addition calculation unit 133 converts the light-emitting product received from the light-receiving unit 123 into a spectrum (light intensity of the light-emitting product) obtained when the spectroscopic measurement unit 12 measures the light-emitting product (hereinafter also referred to as light-emitting product light intensity R (λ)). On the other hand, an addition operation is performed using the multiplication constant stored in the multiplication constant storage unit 162 a and the difference value stored in the difference storage unit 162 b, and the result is transmitted to the chromaticity conversion unit 14.

  The chromaticity conversion unit 14 converts the spectrum received from the addition calculation unit 133 into chromaticity values (chromaticity values at chromaticity coordinates), and transmits the conversion result to the determination unit 15.

  The determination unit 15 compares the chromaticity value received from the chromaticity conversion unit 14 with the inspection standard stored in advance in the inspection standard storage unit 163 to determine the quality of the luminescent product, and determines the determination result as the determination result storage unit 164. Send to.

  The data storage unit 16 supplies various data used for the numerical calculation processing of the calibration unit 13 and the determination of the determination unit 15, and stores the calculation result of the calibration unit 13 and the determination result of the determination unit 15.

  The known light intensity storage unit 161 stores the known light intensity P (λ) and transmits it to the multiplication constant calculation unit 131 and the difference calculation unit 132 in accordance with the control of the control unit 11.

The calibration coefficient storage unit 162 stores the calculation result calculated by the calibration unit 13.
The multiplication constant storage unit 162 a stores the multiplication constant calculated by the multiplication constant calculation unit 131 and transmits the multiplication constant to the difference calculation unit 132 and the addition calculation unit 133 according to the control of the control unit 11.

  The difference storage unit 162 b stores the difference value calculated by the difference calculation unit 132 and transmits the difference value to the addition calculation unit 133 according to the control of the control unit 11.

  The inspection standard storage unit 163 stores the inspection standard used for determining the quality of the luminescent product and transmits it to the determination unit 15 according to the control of the control unit 11.

The determination result storage unit 164 stores the result of the determination unit 15 determining the quality of the light emitting product.
Hereinafter, an inspection method in the optical inspection apparatus 10 will be described with reference to FIG.

  FIG. 2 is an inspection flowchart showing a flow of processing of the inspection method in the optical inspection apparatus 10 according to the embodiment of the present invention.

  First, the known light intensity P (λ) is stored in the known light intensity storage unit 161 (S101). The known light intensity P (λ) is obtained by measuring the spectrum of the reference light source with higher accuracy than the optical inspection apparatus 10. For example, the known light intensity P (λ) is a high level possessed by a laboratory or calibration organization that has been certified based on international standards. It was measured using a precision spectrometer. Since the known light intensity P (λ) is a highly reliable measurement value, it is used as a reference for calibration of the optical inspection apparatus 10.

  Next, the control unit 11 applies a voltage to the reference light source based on the control information of the reference light source preset by the measurer, and causes the reference light source to emit light (S102). The control information of the reference light source includes a voltage value and a limit current value applied to the reference light source, a timing when the power is supplied to the reference light source, and a length thereof.

  Subsequently, the control unit 11 controls the spectroscopic measurement unit 12 based on the control information of the light receiving unit 123 preset by the measurer, and acquires the measurement light intensity Q (λ) (S103). The control information of the light receiving unit 123 includes the exposure time of the light receiving unit 123, the timing of starting exposure, the amplification factor of the amplifier, and the like.

  Next, the multiplication constant calculation unit 131 uses the known light intensity P (λ) stored in the known light intensity storage unit 161 in step S101 and the measured light intensity Q (λ) acquired in step S103 to use the multiplication constant. A is obtained (S104). The multiplication constant A is a constant value regardless of the wavelength, and is specifically determined so that the maximum value of the measured light intensity Q (λ) matches the maximum value of the known light intensity P (λ). That is, assuming that the wavelengths at which the known light intensity P (λ) and the measured light intensity Q (λ) have the maximum values are λp and λq, respectively, the multiplication constant A is expressed by the following equation (5).

A = P (λp) / Q (λq) (5)
Subsequently, the multiplication constant A obtained in step S104 is stored in the multiplication constant storage unit 162a (S105).

  Next, the difference calculation unit 132 multiplies the measured light intensity Q (λ) acquired in step S103 by the multiplication constant A obtained in step S104, and the known light stored in the known light intensity storage unit 161 in step S101. A difference value β (λ) is obtained by calculating a difference from the intensity P (λ) (S106). The difference value β (λ) is expressed by the following equation (6).

β (λ) = P (λ) −A × Q (λ) (6)
Subsequently, the difference value β (λ) obtained in step S106 is stored in the difference storage unit 162b (S107).

  Using the difference value β (λ) thus obtained, the light emission product light intensity R (λ) is calibrated as follows.

  First, the inspection standard of the luminescent product is stored in the inspection standard storage unit 163 (S108). The inspection standard is an allowable range of chromaticity values determined according to the type, application, rank, and the like of the luminescent product. Generally, tristimulus values X, Y, Z and chromaticity coordinates (x, y) in the XYZ color system are used. ). When the chromaticity value obtained by inspecting the luminescent product with the optical inspection device 10 satisfies the inspection standard, the luminescent product is determined as a non-defective product.

  Next, the control unit 11 turns on the light emitting product based on the control information of the light emitting product preset by the measurer, and causes the light emitting product to emit light (S109). The control information of the light emitting product includes a voltage value and a limiting current value applied to the light emitting product, a timing at which the power to the light emitting product is turned on, and a length thereof, and may be the same as the control information of the reference light source set in step S102. Generally, it is different.

  Subsequently, the control unit 11 controls the spectroscopic measurement unit 12 based on the control information of the light receiving unit 123 preset by the measurer, and acquires the light emission product light intensity R (λ) (S110). The control information of the light receiving unit 123 is the exposure time of the light receiving unit 123, the timing of starting exposure, the amplification factor of the amplifier, and the like, and may be the same as the control information of the light receiving unit 123 set in step S103, but generally different. .

  Next, the addition operation unit 133 multiplies the light emission product light intensity R (λ) acquired in step S110 by the multiplication constant A stored in the multiplication constant storage unit 162a in step S105, and further stores the difference in step S107. The light intensity Rβ (λ) after calibration is obtained by calculating the addition with the difference value β (λ) stored in the unit 162b (S111). The light intensity Rβ (λ) after calibration is expressed by the following equation (7).

Rβ (λ) = A × R (λ) + β (λ) (7)
Next, the chromaticity conversion unit 14 converts the calibrated light intensity Rβ (λ) into a chromaticity value in the same format as the inspection standard stored in the inspection standard storage unit 163 (S112). Conversion to the chromaticity value is performed as described in the equations (1a) to (1c), the equations (2a), and (2b) with reference to FIGS.

  Next, the determination unit 15 compares the chromaticity value converted in step S112 with the inspection standard stored in the inspection standard storage unit 163 in step S108, and determines the quality of the luminescent product (S113).

  Finally, the determination result obtained in step S113 is stored in the determination result storage unit 164 (S114). At this time, not only the determination result but also the light intensity Rβ (λ) after calibration obtained in step S111, the chromaticity value obtained in step S112, the control information of the light emitting product used in step S109, and the like are also determined. It may be stored in the storage unit 164.

  When the inspection is continued for the light emitting product having the same inspection standard, the steps S101 to S108 can be omitted, and the process can be continued from step S109. When inspecting light emitting products having different inspection standards, steps S101 to S107 can be omitted, and it is sufficient to continue from step S108.

  The reason why the optical inspection device 10 according to the embodiment of the present invention can obtain the chromaticity value with higher accuracy than the conventional optical inspection device will be described below. First, the reason why the chromaticity value can be appropriately inspected by the arithmetic processing for multiplying by a multiplication constant independent of the wavelength will be described with reference to FIGS.

FIG. 3 is a diagram showing the relationship between the known light intensity P (λ) and the measured light intensity Q (λ).
When the measurement light intensity Q (λ) was obtained, the measurement light intensity Q (λ) was shifted by 1 nm to the short wavelength side as a whole compared to the known light intensity P (λ), and took the maximum value at the wavelength λq. To do. Furthermore, it is assumed that the light intensity at each wavelength of the measured light intensity Q (λ) is 90% of the light intensity at the wavelength corresponding to the known light intensity P (λ).

  In the optical inspection apparatus 10, an error generated between the measured light intensity Q (λ) and the known light intensity P (λ) is divided into an error dependent on the wavelength and an error independent of the wavelength. Calibrate the independent error.

  The optical inspection apparatus 10 calibrates the measurement light intensity Q (λ) in the light intensity direction (vertical axis direction) by multiplying by a constant multiplication constant A regardless of the wavelength, and uses the known light intensity P as a reference. The maximum value of (λ) is used. That is, the multiplication constant A, which is a constant value regardless of the wavelength, is obtained from the light intensity Q (λq) at the peak wavelength λq of the measured light intensity Q (λ) and the known light intensity P ( The light intensity P (λp) at the peak wavelength λp of λ) is determined so as to match.

A = P (λp) / Q (λq) = 1 / 0.90 (8)
Subsequently, the difference value β (λ) is calculated by calculating the difference between the known light intensity P (λ) and the measured light intensity Q (λ) multiplied by the multiplication constant A as shown in the following equation (9). Get. Since the error that does not depend on the wavelength is calibrated by multiplying the multiplication constant A that is a constant value regardless of the wavelength, the difference value β (λ) is obtained by extracting the error that depends on the wavelength.

β (λ) = P (λ) −A × Q (λ) (9)
FIG. 4 is a diagram showing the difference value β (λ) obtained from the measured light intensity Q (λ) in the optical inspection apparatus 10 according to the embodiment of the present invention.

The light intensity R (λ) of the luminescent product is calibrated using the difference value β (λ) obtained in this way.
A luminescent product is generally a different type of light source than a reference light source. Therefore, the light emitting product is also a white LED having a peak in the blue wavelength range like the reference light source, but the peak wavelength λr is 10 nm shorter than the peak wavelength λp of the known light intensity P (λ) of the reference light source. Suppose that it is on the wavelength side.

  By calculating the multiplication constant A and the difference value β (λ) to the light emission product light intensity R (λ) as in the following equation (10), the error depending on the wavelength is corrected to the light intensity Rβ (λ) after calibration. Can be reflected correctly.

Rβ (λ) = A × R (λ) + β (λ) (10)
FIG. 5 is a diagram showing a relationship between the light emission product light intensity R (λ) and the calibrated light intensity Rβ (λ) in the optical inspection apparatus 10 according to the embodiment of the present invention.

  As shown in equation (10), the error independent of the wavelength is calibrated by multiplying the light emission product light intensity R (λ) by the multiplication constant A, and the error depending on the wavelength is added by adding the difference value β (λ). Can be calibrated. Further, by multiplying by the multiplication constant A, the relative magnitude of the difference value β (λ) with respect to the light emission product light intensity R (λ) can be adjusted. Therefore, the optical inspection apparatus 10 can mitigate the influence on the calibration due to the difference in wavelength, compared to the case where calibration is performed using only the proportionality coefficient α (λ). Therefore, the optical inspection device 10 can suppress an increase in error due to calibration even when inspecting a light emitting product whose light intensity changes sharply depending on the wavelength, such as a white LED.

  The above description with reference to FIGS. 3 to 5 is summarized. First, the known light intensity P (λ) and the measured light intensity Q (λ) of the reference light source are used by using the multiplication constant A that does not depend on the wavelength. The error that does not depend on the wavelength generated between and is calibrated. Next, an error dependent on the wavelength can be extracted by obtaining the difference value β (λ). Then, by multiplying the light intensity of the light emitting product to be inspected by the multiplication constant A and adding the difference value β (λ), it is possible to appropriately reflect the wavelength dependent error and the wavelength independent error. Therefore, the optical inspection device 10 can appropriately inspect the chromaticity value of the luminescent product than the conventional optical inspection device.

  Next, the chromaticity value is compared with the conventional optical inspection apparatus in which the optical inspection apparatus 10 calculates a ratio by an arithmetic process that obtains a difference between the known light intensity P (λ) and the measured light intensity Q (λ). The reason why it can be properly inspected will be described with reference to FIG.

  FIG. 6 is a diagram illustrating errors that occur in the process of calculating tristimulus values in the optical inspection device 10. Function a is plotted against the right vertical axis, and function b and function c are plotted against the left vertical axis. The functions a to c are results obtained by measuring the same light emitting product.

The function a is a product for each wavelength of the light intensity J (λ) obtained by measurement with a high-accuracy spectrometer and the color matching function z (λ). The tristimulus value Z _a obtained from the function a is expressed by the following equation (11a) as in the equation (1c).

Z _a = k∫ {J (λ) × z (λ)} dλ (11a)
The function b is an error Δ _b (λ generated between the function a and the product of the light intensity obtained by inspection with the optical inspection device 10 and the color matching function z (λ) for each wavelength. ). The function c is an error Δ _c () generated between the function a and the product of the light intensity obtained by inspection with a conventional optical inspection apparatus and the color matching function z (λ) for each wavelength. λ). The tristimulus values Z _b and Z _c obtained from the functions b and _c are expressed by the following equations (11b) and (11c).

Z _b = Z _a + k∫Δ _b (λ) dλ (11b)
Z _c = Z _a + k∫Δ _c (λ) dλ (11c)
First, paying attention to the error Δ _b (λ), since the area of the positive part and the area of the negative part are substantially equal, the integrated value of the error Δ _b (λ) becomes substantially zero. Therefore, tristimulus values Z _b is approximately equal to the tristimulus value Z _a, it can be said that a high accuracy. On the other hand, since the error Δ _c (λ) has a negative area larger than a positive area, a negative value remains even if integrated.

  That is, in the optical inspection device 10 according to the embodiment of the present invention, errors in the spectrum due to calibration are canceled out in the course of calculation of chromaticity conversion, so that errors in tristimulus values are reduced. On the other hand, in the conventional optical inspection apparatus, since the rate at which the error is canceled in the calculation process of chromaticity conversion is small, the error of the tristimulus value is difficult to reduce. Therefore, the optical inspection apparatus 10 can inspect the chromaticity value more appropriately than the conventional optical inspection apparatus.

  FIG. 7 is a diagram showing errors in chromaticity values at chromaticity coordinates obtained by inspecting a light-emitting product to be inspected in the optical inspection apparatus 10 according to the embodiment of the present invention.

  The chromaticity value is represented by chromaticity coordinates (x, y), and the horizontal axis represents the difference between the true value of the chromaticity value x and the chromaticity value x obtained by the optical inspection device 10. The vertical axis represents the difference between the true value of the chromaticity value y and the chromaticity value y obtained by the optical inspection device 10. The true value of the chromaticity value x and the chromaticity value y is a chromaticity value obtained by measuring the same luminescent product with a spectroscopic measurement device capable of measuring the chromaticity value with higher accuracy than the optical inspection device 10. It is. Plotted are chromaticity values obtained by inspecting a specific light emitting product (number of samples is 1) with the optical inspection device 10 a plurality of times (the number of inspections is 50).

  In the measurement error of the chromaticity value shown in FIG. 7, the chromaticity value x is all within ± 0.0050, and the chromaticity value y is almost within ± 0.0020. As described above, the chromaticity difference that can be identified by the human eye is about ± 0.01. In the optical inspection device 10, it can be seen that the maximum value of the chromaticity value error is less than half of the chromaticity difference that can be identified by the human eye.

  In order to show that the chromaticity value can be properly inspected by the optical inspection apparatus 10, the light intensity R (λ) of the luminescent product obtained by inspecting the same luminescent product with the conventional optical inspection apparatus is expressed as a proportional coefficient α. Calibrate using (λ) and compare inspection results. Hereinafter, a description will be given with reference to FIGS.

  In the conventional optical inspection apparatus, it is assumed that the measurement light intensity Q (λ) shown in FIG. In the conventional optical inspection apparatus, the proportionality coefficient α (λ) is obtained by the above-described equation (3). The light intensity Rα (λ) after calibration obtained by calibrating the light emitting product light intensity R (λ) using the proportionality coefficient α (λ) is expressed by the above-described equation (4).

  FIG. 12 is a diagram showing how the proportionality coefficient α (λ) depends on the wavelength in a conventional optical inspection apparatus.

  FIG. 13 is a diagram showing a relationship between the light emission product light intensity R (λ) and the calibrated light intensity Rα (λ) in a conventional optical inspection apparatus.

  From the light intensity Rα (λ) after calibration obtained in this way, the chromaticity value is calculated based on the above-described equations (1a) to (1c), and equations (2a) and (2b).

  FIG. 14 is a diagram showing an error in chromaticity values in chromaticity coordinates obtained when a light emitting product to be inspected is measured in a conventional optical inspection apparatus.

  The chromaticity value is represented by chromaticity coordinates (x, y), and the horizontal axis represents the difference between the true value of the chromaticity value x and the chromaticity value x obtained by a conventional optical inspection apparatus. The vertical axis represents the difference between the true value of the chromaticity value y and the chromaticity value y obtained by a conventional optical inspection apparatus. The true value of the chromaticity value x and the chromaticity value y is the chromaticity obtained by measuring the same luminescent product with a spectroscopic measurement device capable of measuring the chromaticity value with higher accuracy than a conventional optical inspection device. Which is the same value as the true value of the chromaticity value x and chromaticity value y in FIG. 14 and the inspection result in the optical inspection apparatus 10 shown in FIG. 7 are obtained by inspecting the same light emitting product (the number of samples is 1) the same number of times (inspection number is 50 times). Only the arithmetic processing is different.

  The measurement result shown in FIG. 14 shows that the error of the chromaticity value x is distributed in the range from +0.0070 to -0.0040, and the error of the chromaticity value y is distributed in the range from +0.016 to -0.010. As a result, an error equal to or greater than the chromaticity difference that can be identified by the human eye has occurred.

  Comparing FIG. 6 with FIG. 14, it can be seen that the error of the chromaticity value is greatly reduced in the optical inspection device 10 according to the embodiment of the present invention. Therefore, it can be said that the optical inspection device 10 can appropriately inspect the chromaticity value as compared with the conventional optical inspection device.

  In the above description, the multiplication constant A is a constant value regardless of the wavelength in all wavelength ranges. However, the present invention is not limited to this, and the wavelength ranges are, for example, blue, green, red For example, different multiplication constants may be used for each wavelength range.

  Further, the magnitude of the light intensity of the measurement light intensity Q (λ) is adjusted such that the maximum value of the known light intensity P (λ) of the reference light source matches the maximum value of the measurement light intensity Q (λ) of the reference light source. If it is not necessary, it is only necessary to calculate the difference value between the known light intensity P (λ) and the measured light intensity Q (λ) without using the multiplication constant A. By doing so, it is not necessary to multiply the light emission product light intensity R (λ) for each wavelength by the multiplication constant A at the time of inspection of the light emitting product, so that it is possible to reduce the calculation processing amount of the addition operation unit 133. Therefore, it is possible to realize the optical inspection apparatus 10 capable of performing inspection at higher speed.

  In the above description, the multiplication constant A is obtained so that the maximum value of the known light intensity P (λ) matches the maximum value of the measured light intensity Q (λ). However, the present invention is not limited to this. . For example, the multiplication constant A may be obtained so that the minimum value of the known light intensity P (λ) matches the minimum value of the measured light intensity Q (λ). Alternatively, the multiplication constant A may be obtained so that the known light intensity P (λs) at the arbitrary wavelength λs matches the measured light intensity Q (λs). Alternatively, the multiplication constant A may be obtained so that the average value of the light intensity of the known light intensity P (λ) and the average value of the light intensity of the measurement light intensity Q (λ) match.

  In the above description, as shown in the equation (9), the measured light intensity Q (λ) is multiplied by the multiplication constant A to obtain the difference value β (λ) from the known light intensity P (λ). However, the present invention is not limited to this. The multiplication constant A may be arbitrarily determined so that the measured light intensity Q (λ) and the known light intensity P (λ) coincide with each other. Therefore, for example, as shown in the following formulas (12a) to (12c), the measured light intensity is multiplied not by the measured light intensity Q (λ) but by the multiplication constant A to the known light intensity P (λ). A difference value from Q (λ) may be calculated.

A = Q (λq) / P (λp) (12a)
β (λ) = Q (λ) −A × P (λ) (12b)
Rβ (λ) = A × R (λ) + β (λ) (12c)
Alternatively, the magnitude of the light intensity may be adjusted by multiplying the measured light intensity Q (λ) and the known light intensity P (λ) by different multiplication constants.

  In the above description, the case where white is generated using a semiconductor element that emits blue and a phosphor that converts blue excitation light into green or red has been described. However, the present invention is not limited to this. Absent.

  By the way, the spectroscopic measurement unit 12 of the optical inspection device generally has different light receiving sensitivities depending on wavelengths depending on the material of the light receiving unit.

  FIG. 8 is a diagram showing the light receiving sensitivity for each wavelength of the spectroscopic measurement unit 12. The function d shown in FIG. 8 is the light reception sensitivity for each wavelength of the spectroscopic measurement unit of a certain optical inspection device, and the function e is the light reception sensitivity for each wavelength of the spectroscopic measurement unit of another optical inspection device.

  The function e has a light reception sensitivity difference of up to about three times for each wavelength, whereas the function d has a smaller light reception sensitivity difference for each wavelength than the function e and can be said to be almost constant. When inspecting a light emitting product in which the light intensity is distributed over a wide wavelength range, such as a white LED, it is better to use a spectroscopic measurement unit whose light receiving sensitivity for each wavelength is substantially constant as in the function d. Can be inspected with high accuracy.

(Modification)
In the optical inspection device 10 according to the embodiment of the present invention, the case where the difference value β (λ) is added after multiplying the multiplication constant A in calibrating the light emitting product light intensity R (λ) to be inspected has been described. However, the present invention is not limited to this. By controlling the spectroscopic measurement unit 12 and the calibration unit 13 as follows, the arithmetic processing for multiplying the light emission product light intensity R (λ) by the multiplication constant A can be omitted.

  When the multiplication constant calculating unit 131 obtains the multiplication constant A so that the maximum value of the known light intensity P (λ) and the maximum value of the measured light intensity Q (λ) match, the multiplication constant A is transmitted to the light receiving unit 123. To do. The light receiving unit 123 adjusts the output voltage by changing the exposure time of the light receiving element (not shown) and the amplification factor of the amplifier (not shown) according to the multiplication constant A.

  In this case, the calculation process in which the addition calculation unit 133 multiplies the multiplication constant A becomes unnecessary, and the calculation processing amount of the addition calculation unit 133 can be reduced. Therefore, it is possible to realize the optical inspection apparatus 10 capable of performing inspection at higher speed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Light source, 10 Optical inspection apparatus, 11 Control part, 12 Spectrometer part, 121 Light guide part, 122 Spectrometer part, 123 Light receiving part, 13 Calibration part, 131 Multiplication constant calculating part, 132 Difference calculating part, 133 Addition calculating part, 14 chromaticity conversion unit, 15 determination unit, 16 data storage unit, 161 known light intensity storage unit, 162 calibration coefficient storage unit, 162a multiplication constant storage unit, 162b difference storage unit, 163 inspection standard storage unit, 164 determination result storage unit .

Claims (5)

An optical inspection device for inspecting the quality of a luminescent product,
A spectroscopic measurement unit including a spectroscopic unit that splits light from the light emitting product; and a light receiving unit that receives the light split by the spectroscopic unit;
A calibration unit that calibrates the light intensity for each wavelength measured by the spectroscopic measurement unit by numerical calculation processing;
A chromaticity conversion unit that converts light intensity for each wavelength calibrated by the calibration unit into chromaticity values in chromaticity coordinates;
A determination unit that compares the chromaticity value converted by the chromaticity conversion unit with a predetermined inspection standard and determines the quality of the luminescent product, and
The calibration unit is
Before the inspection of the luminescent product, a multiplication constant calculation unit that calculates a multiplication constant based on a known light intensity of a reference light source and a measurement light intensity obtained when the reference light source is measured by the spectroscopic measurement unit;
Before the inspection of the luminescent product, a difference calculation unit that calculates a difference value between the known light intensity of the reference light source and the measured light intensity multiplied by the multiplication constant for each wavelength;
An addition operation unit that calibrates the light intensity of the luminescent product by multiplying the light intensity of the luminescent product measured by the spectroscopic measurement unit by the multiplication constant and adding the difference value when inspecting the luminescent product; Including optical inspection equipment.   The optical inspection apparatus according to claim 1, wherein the multiplication constant is a constant value regardless of a wavelength.   3. The multiplication constant calculation unit according to claim 2, wherein the multiplication constant calculation unit calculates the multiplication constant so that a maximum value of the known light intensity of the reference light source matches a maximum value of the measurement light intensity of the reference light source. Optical inspection device.   The optical inspection apparatus according to claim 1, wherein the light receiving unit has a substantially constant light receiving sensitivity for each wavelength. The addition operation unit does not multiply the light intensity of the luminescent product measured by the spectroscopic measurement unit by the multiplication constant,
The calibration unit receives the light reception so that the maximum value of the known light intensity of the reference light source and the maximum value of the measurement light intensity of the reference light source coincide with each other according to the multiplication constant calculated by the multiplication constant calculation unit. The optical inspection apparatus according to claim 1, wherein the output of the unit is adjusted.

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