JPWO2009128338A1 - Photometric device - Google Patents

Abstract

The light receiving unit (4) of the photometric device (2) includes a light receiving element (4a) arranged at a position corresponding to light on the short wavelength side cut by the cut filter (26), and cut by the cut filter (26). The output of the light receiving element (4a) arranged at a position corresponding to the light on the short wavelength side is used as the dark current output. The arithmetic circuit (6) uses a dark current output as a photometric output from each light receiving element (4a) arranged at a position corresponding to light having a wavelength longer than the shorter wavelength to be cut. A correction circuit (30) is provided for correction.

Description

  The present invention relates to an improvement in a photometric device that splits light from an object to be measured and measures the luminance and the like of each wavelength.

  2. Description of the Related Art Conventionally, a photometric device that splits the wavelength of light from a measurement object and measures the luminance and the like of each wavelength is known.

  In this conventional photometric device, light from a measurement object is dispersed at each wavelength by a diffraction grating, and the light dispersed at each wavelength is received by a solid-state image sensor as a light receiving unit, and output from the solid-state image sensor Based on the above, the luminance, chromaticity, etc. of light of each wavelength are measured.

  In this conventional photometric device, a dark current is output from the solid-state image sensor due to thermal noise even when no light is incident on each light receiving element of the light receiving unit (dark current output).

  Therefore, the dark current output from the solid-state image sensor is detected in a state where the light from the measurement object is not incident on the light receiving unit, and then the light from the measurement object is incident on the light receiving unit and the photometric output from the solid-state image sensor. A photometric device configured to perform a plurality of measurements to detect the difference between the photometric output and the dark current output by calculation and correct the photometric output from each light receiving element by removing the dark current output. Proposed.

In addition, a mask is provided at the end of the light receiving portion so that light from the measurement object does not enter the light receiving device covered with the mask, and the dark current output from the light receiving device covered with the mask and the mask are used. There has also been proposed a photometric device having a simultaneous measurement configuration in which the photometric output from each light receiving element that is not covered is simultaneously detected and the photometric output from each light receiving element is corrected (see, for example, Patent Document 1).
JP 58-158528 A

  By the way, in the photometric device configured to perform the measurement a plurality of times, it is possible to measure accurately, but there is a disadvantage that the measurement takes time.

  In the photometry device having the simultaneous measurement configuration, the measurement speed can be improved, but there is a disadvantage that a mask must be provided in the light receiving unit, and the structure of the light receiving unit must be changed. In addition, the dark current output from each light receiving element is not necessarily uniform, and even if the dark current output from the light receiving element covered with the mask is uniformly subtracted to obtain the photometric output by correction, It is not always possible to remove the dark current output accurately, and it is insufficient from the viewpoint of precise measurement.

  An object of the present invention relates to a photometric device capable of improving the measurement speed without changing the structure of an existing light receiving unit and suppressing a decrease in measurement accuracy.

  A photometric device according to the present invention includes a spectrophotometric optical system that spectrally measures light from an object to be measured, a light receiving unit that receives light separated by wavelength by the spectrophotometric optical system, and photometry of the light receiving unit A spectrophotometric optical system that converts light from a measurement object into a parallel light beam, and a light beam that has passed through the collimator lens is decomposed for each wavelength. A wavelength resolving element, a condensing lens that condenses each light beam decomposed for each wavelength on the light receiving unit, and a cut filter that cuts light on a shorter wavelength side than visible light, and the light receiving unit Has a plurality of light receiving elements that respectively receive the light dispersed for each wavelength, and the plurality of light receiving elements are arranged in a predetermined direction corresponding to the position of the predetermined wavelength of the dispersed light. And the plurality of light receiving elements are arranged in front of each other. The output of the light receiving element arranged at the position corresponding to the light on the short wavelength side cut by the cut filter and arranged at the position corresponding to the light on the short wavelength side cut by the cut filter is a dark current output. The arithmetic circuit uses the dark current output for the photometric output from each light receiving element arranged at a position corresponding to the light having a wavelength on the longer wavelength side than the light on the shorter wavelength side to be cut. A correction circuit for correction is provided.

  In the photometric device of the present invention, it is preferable that the cut filter is provided in front of a collimator lens, and the cut filter is a color glass filter for correcting the sensitivity of each wavelength.

  In the photometric device of the present invention, it is preferable that the cut filter is provided behind a collimator lens, and the cut filter is a color glass filter for correcting the sensitivity of each wavelength.

  In the photometric device of the present invention, it is preferable that the cut filter cuts light having a wavelength of 380 nm or less.

  Furthermore, in the photometric device of the present invention, the correction circuit includes a dark current output of a light receiving element arranged at a position corresponding to light on a short wavelength side cut by the cut filter, and a short wavelength side to be cut. The output of each light receiving element arranged at a position corresponding to the light of each wavelength longer than the light, and the output obtained by measurement in a state where the light does not strike each light receiving element Is stored for each light receiving element, and the correction circuit outputs a dark current output for each light receiving element arranged at a position corresponding to light of each wavelength on the longer wavelength side than light on the short wavelength side. It is preferable to determine based on the ratio.

  According to the present invention, there is an effect that the measurement speed can be improved without changing the structure of the existing light receiving unit and suppressing the decrease in measurement accuracy.

It is explanatory drawing which shows the outline | summary of a structure of the photometry apparatus concerning this invention. It is an optical characteristic figure which shows the transmittance | permeability of the cut filter concerning this invention. It is a top view of the light-receiving part concerning this invention. It is explanatory drawing which shows an example of the dark current output output from the line of each light receiving element concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measurement object 2 Photometry apparatus 4 Light-receiving part 6 Arithmetic circuit 4a Light receiving element 15 Spectrophotometry optical system 26 Color glass filter (cut filter)
27 Collimator lens 28 Diffraction grating (wavelength resolving element)
30 Correction circuit

  Embodiments of a photometric device according to the present invention will be described below with reference to the drawings.

  FIG. 1 is an explanatory diagram showing an outline of the configuration of a photometric device according to the present invention, for example, a spectroradiometer. In FIG. 1, reference numeral 1 denotes an object to be measured such as a liquid crystal panel, a signal lamp, a cold cathode tube, a guide lamp, and an LED, and 2 denotes a photometric device.

  The photometric device 2 includes an optical system 3 that receives light from the measurement object 1, a light receiving unit 4, and a circuit unit 5. The circuit unit 5 includes an arithmetic circuit 6 that calculates photometric characteristics (colorimetric data (luminance, chromaticity, color temperature)) based on the photometric output of the light receiving unit 4, an AC power source 7, a DC-DC power source 8, and an LCD display 9. , An operation key 10, an external synchronization input connector 11, an A / D converter 12, and a CCD analog PCB (CCD analog printed circuit board) 13.

  The arithmetic circuit 6 is composed of, for example, a CPU. The AC power supply 7 and the DC-DC power supply 8 supply power to the arithmetic circuit 6, and the operation keys 10 are used to input various commands required for photometry to the arithmetic circuit 6. The LCD display 9 is used to display photometric characteristics and other commands. The external synchronization input connector 11 is used to instruct the timing for measurement in synchronization with the light emission of the measurement object 1. The CCD analog PCB 13 is used for analog output of the photometric output of the light receiving unit 4. The A / D converter 12 is used to convert the analog output into a digital output and input it to the arithmetic circuit 6.

  The optical system 3 is roughly composed of a collimating optical system 14 and a spectrophotometric optical system 15. The collimating optical system 14 is generally composed of an objective lens 16, an aperture mirror 17, a total reflection mirror 18, relay lenses 19 and 20, a finder shutter 21, and an eyepiece lens 22. Light from the measurement object 1 is guided to the aperture mirror 17 through the objective lens 16, reflected by the aperture mirror 17, and guided to the total reflection mirror 18. The light guided to the total reflection mirror 18 is relayed to the position 1 ′ conjugate with the measurement object 1 by the relay lenses 19 and 20, and the image of the measurement object 1 relayed to the conjugate position 1 ′ is an eyepiece. It is collimated by the measurer via the lens 22. When the finder shutter 21 measures the measurement object 1 with extremely low brightness, external light passes through the relay lenses 20 and 19, the total reflection mirror 18, and the aperture mirror 17 from the eyepiece lens 22 side, and the spectrophotometric optical system 15. It has a role to prevent contamination.

  The spectrophotometric optical system 15 includes an objective lens 16 and an aperture mirror 17 shared with the collimation optical system 14, and also includes a relay lens 23, a bundle fiber 24, a turret plate 25, a colored glass filter 26, a collimator lens 27, and a diffraction grating 28. And a condensing lens 29.

  The aperture mirror 17 has an opening 17a. The aperture mirror 17 is used for brightness adjustment. Here, four types of aperture mirrors are prepared, and FIG. 1 shows a state in which one of the aperture mirrors 17 is inserted in the optical path of the spectrophotometric optical system 15.

  The relay lens 23 forms an image of the measurement object 1 on the incident end face 24 a of the bundle fiber 24. The bundle fiber 24 has a function of mixing light from the measurement object 1 and depolarizing the light. The turret plate 25 includes a through-opening 25a, a 10-fold attenuation ND filter 25b, a 100-fold attenuation ND filter 25c, and a light-shielding portion 25d. The turret plate 25 determines the amount of light emitted from the exit end face 24b of the bundle fiber 24. Play the function of adjusting. The collimator lens 27 has a focal point at the position of the emission end face 24b of the bundle fiber 24, and plays a role of converting the light emitted from the bundle fiber 24 into a parallel light flux.

  As shown in FIG. 2, the colored glass filter 26 serves to correct the sensitivity of each wavelength and to serve as a cut filter that blocks light on a shorter wavelength side than visible light, for example, a shorter wavelength side having a wavelength of 380 nm or less. And fulfill. The transmittance of the colored glass filter 26 is set for each wavelength.

  The diffraction grating 28 has a function as a wavelength resolving element that decomposes the light beam that has passed through the collimator lens 27 for each wavelength. The condensing lens 29 has a role of condensing each light beam decomposed for each wavelength on the light receiving unit 4.

  As shown in FIG. 3, the light receiving unit 4 has a rectangular shape, and has n pieces in the horizontal direction, for example, 128 pieces, 256 pieces, 512 pieces, 1024 pieces, etc., and m pieces in the vertical direction, for example, 128 pieces, 256 pieces. , 512, 1024 light receiving elements. Here, the light receiving elements 4a in the lateral direction are light receiving elements arranged in a fixed direction corresponding to the position of a predetermined wavelength of the dispersed light. The light receiving elements 4a in the vertical direction are collectively formed as one line, and the output for each line corresponding to the position of each wavelength is input to the arithmetic circuit 6 via the A / D converter 12. The light receiving unit 4 (light receiving element) includes a light receiving element disposed at a position corresponding to light on the short wavelength side cut by the colored glass filter 26. For example, FIG. 3 shows four lines of light-receiving elements 4 a arranged at positions corresponding to light on the short wavelength side with a wavelength of 380 nm or less, and light on the short wavelength side cut by the colored glass filter 26. The output from each line of the light receiving element 4a arranged at the position corresponding to is used as the dark current output.

  The arithmetic circuit 6 is provided with a correction circuit 30. The correction circuit 30 includes a dark current output of the light receiving element 4 a arranged at a position corresponding to the light on the short wavelength side cut by the color glass filter 26, and light on the short wavelength side cut by the color glass filter 26. The ratio of the output of each light receiving element 4a arranged at the position corresponding to the light of each wavelength on the long wavelength side and the output obtained by measurement in a state where the light receiving element 4a is not exposed to light. Is stored for each light receiving element 4a.

  In order to make each light receiving element 4a arranged at a position corresponding to the light of each wavelength on the long wavelength side than the light on the short wavelength side cut by the colored glass filter 26 not to receive light, for example, The photometric device 2 is disposed in the dark room, and the outputs of the light receiving elements 4a of the light receiving unit 4 are simultaneously measured.

As shown in FIG. 4, the dark current output for each line of each light receiving element 4 a varies for each light receiving element 4 a and varies for each individual light receiving unit 4. The dark current output for each light receiving element 4a is obtained in advance by measurement. The dark current output of the line of the light receiving element 4a arranged at a position corresponding to the light on the short wavelength side cut by the color glass filter 26 is X ₀ , the light receiving element 4a used for actual photometry of visible light, that is, the color out of the lines of the light receiving element 4a which is arranged at a position corresponding to the light of a wavelength that is not cut by the glass filter 26, for example, when the dark current output of one line and X, the ratio is X / X _0. The storage unit 31 stores this ratio X / X ₀ corresponding to each line. Correction circuit 30 obtains based on the dark current output for each line of the light receiving elements 4a to the ratio X / X _0.

Here, the photometric output from a line of a light receiving element (indicated by reference numeral 4b) at a certain measurement is y, the dark current output from the line of the light receiving element indicated by reference numeral 4b at the time of measurement is y ', If the dark current output of the line of the light receiving element corresponding to the cut short wavelength side light is y ″,
y ′ = y ″ × (X / X ₀ )
Based on the above formula, the correction circuit 30 calculates a corrected dark current output y ′ for each line of each light receiving element 4a at a certain measurement time point, and calculates a photometric output y from the line of each light receiving element 4a. Correction is performed using the dark current output y ′, and precise photometric characteristics are calculated.

  When such correction is performed, accurate correction can be performed even when the dark current output for each line of the light receiving element 4a varies. In addition, accurate correction can be performed even when the dark current output varies due to thermal noise.

Note that the dark current output X ₀ of the line of the light receiving elements 4a corresponding to the light of the cut short-wavelength side, it is also possible to use an average value of the dark current output of a plurality of lines. For example, in FIG. 3, four lines on the short wavelength side are shown as lines corresponding to light having a wavelength cut by the color glass filter 26. In this case, each dark current of the four lines is shown. The sum of outputs can be obtained, and a value obtained by dividing the sum of dark current outputs by 4 can be used as the average dark current output.

  In the above embodiment, a CCD solid-state image sensor is used as the light receiving element, but other light receiving elements such as CMOS can be used. Further, in this embodiment, in order to obtain a dark current output, a filter that cuts the wavelength on the short wavelength side is used, but the region on the short wavelength side from the measurement wavelength is used. A dark current output may be detected and corrected using a filter that cuts the above wavelength or a wavelength of about 830 nm or more. Furthermore, it is possible to detect a dark current output using both a short wavelength side and a long wavelength side using a bandpass filter and use it for correction. The cut filter can also be disposed behind the collimator lens.

Claims (5)

A spectrophotometric optical system for spectrophotometrically measuring light from a measurement object;
A light receiving unit that receives light separated by wavelength by the spectrophotometric optical system;
An arithmetic circuit that calculates photometric characteristics based on the photometric output of the light receiving unit;
The spectrophotometric optical system is:
A collimator lens that converts light from the measurement object into a parallel light beam;
A wavelength resolving element that decomposes the light beam that has passed through the collimator lens for each wavelength;
A condensing lens for condensing each light beam decomposed for each wavelength on the light receiving unit;
It has a cut filter that cuts light on the shorter wavelength side than visible light,
The light receiving unit is
It has a plurality of light receiving elements that respectively receive the light separated for each wavelength,
The plurality of light receiving elements are arranged in a fixed direction corresponding to a position of a predetermined wavelength of the dispersed light, and the plurality of light receiving elements are light on a short wavelength side cut by the cut filter. Is also arranged at the position corresponding to
The output of the light receiving element arranged at a position corresponding to the light on the short wavelength side cut by the cut filter is used as a dark current output,
In the arithmetic circuit, a correction for correcting the photometric output from each light receiving element arranged at a position corresponding to light having a wavelength on the longer wavelength side than the light on the shorter wavelength side to be cut using the dark current output. A photometric device characterized in that a circuit is provided.   The photometric device according to claim 1, wherein the cut filter is provided in front of a collimator lens, and the cut filter is a color glass filter for correcting the sensitivity of each wavelength.   2. The photometric device according to claim 1, wherein the cut filter is provided behind a collimator lens, and the cut filter is a color glass filter for correcting the sensitivity of each wavelength.   The photometric device according to claim 1, wherein the cut filter cuts light having a wavelength of 380 nm or less.   The correction circuit includes a dark current output of a light receiving element arranged at a position corresponding to the light on the short wavelength side cut by the cut filter, and each wavelength on the longer wavelength side than the light on the short wavelength side to be cut. A memory for storing for each light receiving element the ratio of the output of each light receiving element arranged at a position corresponding to the light of the light source and the output obtained by measurement in a state where the light receiving element does not receive light. And the correction circuit obtains a dark current output for each light receiving element arranged at a position corresponding to light of each wavelength on the longer wavelength side than light on the shorter wavelength side based on the ratio. The photometric device according to any one of claims 1 to 3, wherein the photometric device is characterized.

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