JPH1019680A - Optical angle characteristic measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the measurement error of chromaticity or luminance to perform a highly precise measurement by forming at least one of a plurality of lenses by a multilayer coating film, and reducing the difference in reflectance of P, S components of a polarized emitted light from a measuring surface. SOLUTION: A measuring head 1 having a lens or the like in the inner part takes the image of a subject as the two-dimensional angle image. The image pickup data is processed by a data processing unit 2, and the display of a color monitor 4 is controlled to display a distribution map of chromaticity or luminance by angle, for example, with polar coordinates. Since the taken angle image is formed according to the direction of the light emitted from a measuring surface, the position of each picture element taking the angle image is conformed to the direction of the emitted light. Of a plurality of lenses of the head 1, at least one lens having a large incident angle of measuring light is coated with a multilayer evaporated film to form a coating film. Thus, even when the measuring light is a linear polarized light, the difference in reflectance of P, S components can be reduced, and the measurement error of chromaticity or luminance of the subject can be reduced to perform a highly precise measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical angle characteristic measuring device for measuring an angular characteristic of an object having different chromaticity and luminance depending on an observation angle, and more particularly to an optical angle characteristic measuring apparatus having polarized light. The present invention relates to an optical angle characteristic measuring device capable of measuring with high accuracy.

[0002]

2. Description of the Related Art It is known that the color of a liquid crystal display panel changes or the brightness decreases as the viewing angle increases. Such characteristics are improved to increase the viewing angle. This has become a major issue in the development of liquid crystal display panels. Therefore, an optical angle characteristic measuring device capable of easily measuring the viewing angle characteristic of a liquid crystal display panel is demanded.

Conventionally, in an apparatus for measuring a two-dimensional light distribution of a point light source such as a semiconductor laser or an optical fiber emission end, a two-dimensional intensity distribution is provided at a position corresponding to an emission angle instead of a type in which a light receiving part is mechanically swung. A measuring device for forming a distribution image has been proposed (Japanese Patent Publication No. 3-4858).
According to such a measuring device, it is not necessary to mechanically change the angle, so that there is an advantage that the measurement in the angular direction can be performed simultaneously and collectively. Further, as an improvement of the above measuring device, there has been proposed a measuring device which is capable of measuring a two-dimensional light distribution by providing an illuminating means for illuminating the measured object when the measured object does not emit light by itself. (Japanese Patent Application Laid-Open No. Hei 5-28838).

[0004]

Problems to be Solved by the Invention
In the measuring apparatus described in Japanese Patent Application Laid-Open No. 4858 and Japanese Patent Application Laid-Open No. Hei 5-2888638, as shown in FIG. An objective lens 11 that collects light emitted from the surface S at a position corresponding to the angle θ and forms an angle image i at a rear focal point is used. Objective lens 11
Is generally composed of a plurality of lens groups.

When the emission angle of light from the object under test 10, that is, the viewing angle θ is large, the incident angle at which the measurement light enters the lens surface becomes large, as shown in FIG. Further, this measurement light passes through the lens a plurality of times with the incident angle with the lens surface and the emission angle from the lens surface being large. In general, when light is incident on media having different refractive indices, reflection occurs at the boundary surface. The reflectance is a function of the refractive index and the incident angle of the two media. Will increase. Moreover, by transmitting through a plurality of lenses, the loss due to reflection is accumulated for each transmission, and the amount of transmitted light is reduced.

In order to suppress this, a coating for preventing reflection is applied to the lens surface. However, even if a general photographic multi-coating is applied, the entire range of visible light can be prevented. , It is difficult to keep the reflectance of light having a large incident angle low.

The reflectance varies depending on the vibration direction of the light, that is, the P component and the S component. However, when the light passes through a plurality of lenses, the difference in the reflectance increases. The difference between the reflectance of the P component and the reflectance of the S component is caused by the fact that only a light beam passing through a narrow portion of the lens contributes to the image formation.
In an optical system such as that described above, it appears remarkably.

FIG. 14 is a diagram for explaining the P component and the S component of the objective lens 11 when the incident light is linearly polarized light. For convenience of explanation, the objective lens 11 is constituted by one lens. In FIG. 14, the center of curvature of the first surface (incident surface) of the objective lens 11 is point C, the center of the first surface is point O, the front focus (position of the object to be measured) is point S, and the rear focus (field of view). The point at which the square image is formed is point O ′.

It is assumed that light emitted from point S at a viewing angle θ enters point A on the first surface of objective lens 11. At this time, since the incident surface is a surface including △ SAC, if the light emitted from the point S is linearly polarized light that oscillates in that surface, all the light components become P components with respect to the lens.

On the other hand, the azimuth is 90 from the point S at the same viewing angle θ.
The light emitted in different directions enters the point B on the first surface of the objective lens 11. At this time, since the incident surface is a surface containing △ SBC, all the linearly polarized light oscillating in the plane containing △ SAC becomes an S component with respect to the lens.

The light incident on the points A and B is reflected by the rear focal point O '.
The points A ′ and B ′ in the plane including the point are reached. In particular, when the F-number of the objective lens 11 is dark, the points A 'and B'
Since the width of the light beam contributing to the image formation at the point becomes narrower, this light beam passes through only the portions near the points A and B at the position of incidence on the objective lens 11.

Therefore, in this case, at the point A ', almost P
An image is formed only by the light of the component, at point B ′, an image is formed only by the light of almost the S component, and at other azimuth points, the light is composed of the P component and the S component at a ratio corresponding to the angle of the azimuth. Form an image.

When the light emitted from the object has the same intensity in all directions, an image having the same brightness is formed at points A 'and B'. When the light to be emitted is linearly polarized light, the reflectances of the P component and the S component are different, and hence the transmittances are different. Therefore, if the orientation of the polarization plane is different, an image having the same brightness is not formed, and the measurement error is reduced. Will happen. This measurement error is particularly caused by the incident angle ∠SA
It increases when C and ∠SBC are large.

In the case where the object to be measured is a liquid crystal display panel, the emitted light has passed through the linear polarizing film, so that it is almost completely polarized, and the above-described problem occurs. In particular, when a lens is used, the angle of incidence of the light emitted from the liquid crystal display panel on the lens increases as the viewing angle to be measured increases, so that the polarization characteristics appear remarkably. Also,
In the case of an object to be measured other than the liquid crystal display panel having a large polarization degree, the measurement is similarly adversely affected.

However, none of the measuring devices described in JP-B-3-4858 and JP-A-5-288638 consider the case where the light emitted from the object to be measured has polarized light. Therefore, there is no disclosure of a configuration for eliminating a measurement error due to the polarization.

Conventionally, when the measurement light is linearly polarized light,
In some cases, linear polarization was changed to circular polarization by passing through a wave plate or Fresnel rom prism, and measurement was performed to remove errors due to linear polarization. The prism is not suitable for measuring an object to be measured having a wide viewing angle because the range of the incident angle at which the linearly polarized light can be converted into the circularly polarized light is not wide.

Therefore, when measuring light emitted from an object to be measured over a wide viewing angle as in a liquid crystal display panel, the above-mentioned quarter-wave plate or Fresnel ROM is placed between the object to be measured and the objective lens. Even if a prism is provided, it is difficult to remove an error due to linearly polarized light over a wide viewing angle.

The present invention solves the above-mentioned problem, and occurs when light emitted from an object to be measured has polarized light.
It is an object of the present invention to provide an optical angle characteristic measuring device capable of correcting a measurement error of an optical angle characteristic relating to the luminance and chromaticity.

[0019]

According to the present invention, there is provided a lens system for forming an angle image based on light from a measurement surface of an object to be measured;
Imaging means for imaging the angular image formed, comprising a plurality of pixels arranged two-dimensionally, wherein the lens system is constituted by a plurality of lenses, and at least one of the plurality of lenses is provided. The sheet is provided with a coating film composed of a plurality of layers, and the difference between the reflectance of the P component and the S component in the lens system of the light emitted from the measurement surface of the object having polarized light is in the visible wavelength range. (Claim 1).

According to this configuration, an angle image based on the light emitted from the measurement surface of the object to be measured is formed by the lens system, and two-dimensionally captured by each pixel. Since the angle image is formed corresponding to the direction of the light emitted from the measurement surface,
The position of each pixel that has captured the angle image corresponds to the direction of light emitted from the measurement surface. Here, at least one of the plurality of lenses constituting the lens system has a coating film made up of a plurality of layers, so that light emitted from the measurement surface of the device under test has polarized light. However, the difference between the reflectance of the P component and the S component in the lens system is reduced over the visible wavelength range, thereby reducing the measurement error caused by the difference in the reflectance.

The lens system includes an objective lens group for forming an angular image based on light from a measurement surface of the object to be measured, which is disposed near the front focal point, on the rear focal plane, and the imaging means for capturing the angular image. And a relay lens group for re-imaging an image on the imaging surface, and the coating film is formed on at least one of the lens groups (claim 2).

According to this configuration, an angular image based on the light emitted from the measurement surface of the object to be measured arranged near the front focal point of the objective lens group is formed on the rear focal plane of the objective lens group. This angle image is re-imaged and two-dimensionally captured by each pixel. Since the angle image is formed corresponding to the direction of the light emitted from the measurement surface, the position of each pixel that has captured the angle image corresponds to the direction of the light emitted from the measurement surface. Since the coating film is formed on at least one of the objective lens group and the relay lens group, the difference between the reflectances of the P component and the S component in the lens system is reduced over the visible wavelength range. This reduces the measurement error caused by the difference in reflectance.

Further, the coating film is composed of a first layer, a second layer, and a third layer which are sequentially laminated from the air side to the lens substrate side.
Layer, a fourth layer, and a fifth layer, and the refractive indices n ₁ , n ₂ , n ₃ , n ₄ , and n ₅ of the respective layers are n ₁ <1.4, n ₂ > 2.0, 1.4
≦ n ₃ ≦ 2.0, n ₄ <1.4, 1.4 ≦ n ₅ ≦ 2.0 (claim 3).

According to this configuration, at least one of the plurality of lenses constituting the lens system includes the first layer, the second layer, and the third layer that are sequentially stacked from the air side to the lens substrate side.
Layer, a fourth layer, and a fifth layer, and the refractive indices n ₁ , n ₂ , n ₃ , n ₄ , and n ₅ of the respective layers are n ₁ <1.4, n ₂ > 2.0, 1.4
≦ n ₃ ≦ 2.0, n ₄ <1.4, 1.4 ≦ n ₅ ≦ 2.0, the coating film is formed so that even when the light emitted from the measurement surface of the object to be measured has polarized light, The difference in the reflectance between the P component and the S component in the lens system is reduced over the visible wavelength range, thereby reducing the measurement error caused by the difference in the reflectance.

Also, a lens system for forming an angle image based on light from the measurement surface of the object to be measured, and an imaging system comprising a plurality of two-dimensionally arranged pixels for capturing the formed angle image Means, storage means for storing polarization characteristics of image data obtained by the imaging means using the polarization direction obtained in advance as a parameter, input means for inputting the polarization direction of light from the measurement surface of the device under test, And a compensating means for extracting a corresponding polarization characteristic from the polarization characteristic stored in the storage means using the polarization direction, and correcting the image data by the imaging means using the polarization characteristic. (Claim 4).

According to this configuration, an angle image based on the light emitted from the measurement surface of the object to be measured is formed by the lens system, and two-dimensionally captured by each pixel. Since the angle image is formed corresponding to the direction of the light emitted from the measurement surface,
The position of each pixel that has captured the angle image corresponds to the direction of light emitted from the measurement surface. On the other hand, from among the polarization characteristics of the imaging data obtained by the imaging means using the polarization direction obtained and stored in advance as a parameter, the corresponding polarization direction of the light emitted from the measurement surface of the input device is used. The polarization characteristics are extracted. Then, the imaging data of the imaging unit is corrected using the extracted polarization characteristics. Therefore, by correcting the imaging data using the polarization characteristics of the imaging unit, a measurement error caused by polarization of the light emitted from the measurement surface of the device under test is reduced.

Also, a lens system for forming an angle image based on light from the measurement surface of the object to be measured, and an imaging system comprising a plurality of two-dimensionally arranged pixels for capturing the formed angle image Means, disposed between the object to be measured and the lens system, the polarization direction changing means for changing the polarization direction of light from the measurement surface of the object to be measured, and the polarization direction in each of the changed polarization direction An averaging means for calculating an average value of image data obtained by the imaging means (claim 5).

According to this configuration, an angle image based on the light emitted from the measurement surface of the object to be measured is formed by the lens system, and two-dimensionally captured by each pixel. Since the angle image is formed corresponding to the direction of the light emitted from the measurement surface,
The position of each pixel that has captured the angle image corresponds to the direction of light emitted from the measurement surface. Here, the polarization direction of light emitted from the measurement surface of the measurement object is changed by the polarization direction changing means disposed between the measurement object and the lens system, and imaging is performed in each of the changed polarization directions. The two-dimensional image is taken by the means. Then, by calculating the average value of the imaging data in each of the changed polarization directions, the measurement error caused by the polarization of the light emitted from the measurement surface of the device under test is reduced.

Further, in the optical angle characteristic measuring apparatus according to any one of claims 1 to 5, a color separation means for causing the imaging means to perform imaging with a spectral sensitivity approximate to a color matching function;
Stimulus value calculating means for calculating a tristimulus value for each pixel from the image data obtained by the image pickup means (claim 6).

According to this configuration, an angle image based on the light emitted from the measurement surface of the object to be measured is formed by the lens system, and two-dimensionally imaged by each pixel with a spectral sensitivity close to the color matching function. Thus, tristimulus values are calculated for each pixel. Since the angle image is formed corresponding to the direction of the light emitted from the measurement surface, the position of each pixel that has captured the angle image corresponds to the direction of the light emitted from the measurement surface. Here, at least one of the plurality of lenses constituting the lens system has a coating film made up of a plurality of layers, so that light emitted from the measurement surface of the device under test has polarized light. But
The difference between the reflectances of the P component and the S component in the lens system is reduced over the visible wavelength range, whereby the measurement error caused by the difference in the reflectance is reduced, and the tristimulus value is accurately calculated.

[0031]

FIG. 10 is a view showing an embodiment of an optical angle characteristic measuring apparatus according to the present invention, wherein (a) is a block diagram showing a control configuration, and (b) is an overall configuration diagram. . This embodiment comprises a measuring head 1, a data processing unit 2,
It comprises a host computer 3 and a color monitor 4, and measures an optical angle characteristic of a device to be measured such as a self-luminous object such as a liquid crystal display panel with a built-in backlight.

The measuring head 1 has a lens and the like inside, as described later, and forms a two-dimensional angular image of an object to be measured and picks up the image. The data processing unit 2 is connected to an output side of the measuring head 1 and stores a ROM 21 for storing a value calculated in advance and an R for temporarily storing data.
It has a built-in AM 22 and performs data processing to be described later on the image data obtained by the measuring head 1. The data processing unit 2 controls the display of the color monitor 4, and displays a marker indicating the optical axis of the measuring head 1 on the output from the measuring head 1, or displays an image obtained by the measuring head 1. The data is displayed two-dimensionally as it is, or the contents after data processing are displayed in a required format, for example, polar coordinates, and a distribution diagram of luminance and chromaticity according to angles is displayed.

The host computer 3 comprises, for example, a personal computer and controls the measuring operation of the measuring head 1 and the data processing of the data processing unit 2. By doing so, control is performed. Further, various calculations are performed from the data obtained by the data processing unit 2, and as a result, for example, a cross-sectional view of the distribution diagram of the luminance and chromaticity in a certain direction φ is displayed on the monitor 31.

The color monitor 4 is, for example, a CRT or an LCD.
It comprises a panel or the like, and displays a measurement result from the data processing unit 2 and the like.

FIG. 11 is a diagram showing the internal configuration of the measuring head 1, and FIG.
FIG. 3 is a diagram illustrating an example of a lens configuration of the objective lens 11. The measuring head 1 includes an objective lens 11, a relay lens system 12,
The filter 13 and the imaging means 14 are arranged on the optical axis L.

The objective lens 11 is, as shown in FIG.
The light emitted from the measurement surface S having a certain degree of spread is collected at a position corresponding to the angle of the object to be measured, which is constituted by a plurality of lens groups and is arranged such that the measurement surface S is located at the front focal point. Thus, an angle image i is formed at the rear focal point. Assuming that the inclination angle of the measurement light beam with respect to the optical axis L is θ and the focal length of the objective lens 11 is f, h = f · θ. Here, h is the image height of the angle image i. Note that the relationship between h and θ need not be linear but may correspond to one-to-one.

The relay lens system 12 includes a rear reduction lens 12b and a lens group of a field lens 12a for condensing the light on the reduction lens 12b, and reduces the angle image i on the light receiving surface of the two-dimensional imaging means 14. And re-image. Note that the imaging unit 14 may directly receive the angle image i. However, if the size of the angle image i is larger than the size of the light receiving surface of the imaging unit 14, the entire angle image i cannot be received. For this reason, the entire angle image i can be received by re-imaging while the angle image i is reduced by interposing the relay lens system 12.

The filters 13 are arranged, for example, on concentric circles of a rotating disk (not shown) having a rotation axis at a position distant from the optical axis L, and each have a color matching function x (λ) of the International Commission on Illumination (CIE). ), y (λ), z (λ), and three optical filters that cause the imaging unit 14 to perform imaging with a spectral sensitivity that is equal to or close to these, and performs color separation of the angle image i.

The rotating shaft of the rotating disk is connected to a driving shaft of a motor (not shown) whose driving is controlled by the host computer 3. Then, at the time of light reception, the optical filters are controlled so as to be positioned on the optical axis L in a predetermined order as shown in FIG.

The image pickup means 14 includes, for example, a large number of photoelectric conversion elements (hereinafter referred to as pixels) such as photodiodes arranged in a two-dimensional matrix, and a charge having a level proportional to the amount of received light converted by each pixel. Having a charge storage unit for storing the charge and a transfer unit for outputting the stored charge
D. The imaging means 14 is arranged so that the light receiving surface of each pixel coincides with the re-imaging position of the angular image i by the relay lens system 12, and by receiving light with the pixels arranged in a two-dimensional matrix, The angle image i is taken two-dimensionally.

Here, the spectral transmittance characteristics of each optical filter of the filter 13 correspond to the color matching functions x (λ), y (λ), z (λ), and the spectral transmittance characteristics of the lenses 12a and 12b. In addition to the spectral sensitivity characteristics of the image pickup means 14, spectral sensitivity equal to or close to the color matching functions x (λ), y (λ), z (λ) is obtained. As a result, the output data of the imaging unit 14 corresponds to the tristimulus values X, Y, and Z.

FIG. 12 is a view for explaining the relationship between the direction of the measurement light beam emitted from the measurement surface S and the angle image i. FIG.
In No. 2, a UV orthogonal coordinate system having the optical axis L as the origin is provided on the surface on which the angle image i is formed. At this time, assuming that the coordinates of a point on the angular image i are (u ₁ , v ₁ ), the distance ₁ (u ₁ ² + v ₁ ² ) of the point from the origin is the inclination angle θ of the measuring ray with respect to the optical axis L. Is proportional to

[0043]

１ (u ₁ ² + v ₁ ² ) ∝θ.

The direction of the angle image i, that is, the tilt angle tan (v ₁ / u ₁ ) with respect to the x-axis is determined by the azimuth φ at which the measuring light beam enters.

[0045]

## EQU2 ## It is expressed by Arc tan (v ₁ / u ₁ ) = φ.

Therefore, the incident angle θ and the incident azimuth φ of the measurement light beam are uniquely determined by the coordinates of the angle image i in the UV orthogonal coordinate system.

Next, data processing performed by the data processing unit 2 will be described. The CIE tristimulus values X, Y and Z are
Assuming that the color matching function is x (λ), y (λ), z (λ) and the spectral distribution of the measured object is P (λ), it is calculated from Equation 3. Here, k is a constant.

[0048]

(Equation 3)

Then, from the tristimulus values X, Y, Z, the chromaticity x,
y is

[0050]

X = X / (X + Y + Z), y = Y / (X + Y + Z)

When the object to be measured is a liquid crystal panel,
The colors are formed by additive mixing of three primary colors of R, G and B. In such a case, the light receiving sensitivity of the measurement system is equal to the color matching function x
Even when they do not match (λ), y (λ), z (λ), true tristimulus values X, Y, Z can be calculated. This calculation procedure is described in detail in JP-A-6-323910, but will be briefly described below.

The spectral characteristics of the constituent colors R, G, B of the DUT are represented by R
(λ), G (λ), B (λ), and let r, g, b be the light quantity of each color,
The spectral emissivity characteristic P (λ) of the device under test is

[0053]

P (λ) = rR (λ) + gG (λ) + bB (λ)

When this is received with spectral sensitivity of the color matching functions x (λ), y (λ), z (λ),

[0055]

X = {P (λ) x (λ) dλ = {{rR (λ) + gG (λ) + bB (λ)} × (λ) dλ = r∫R (λ) x (λ) dλ + g} G (λ) x (λ) dλ + b∫B (λ) x (λ) dλ = rX R + gX G + bX B, X R = ∫R (λ) x (λ) dλ X G = ∫G (λ) x ( lambda) becomes _{dλ X B = ∫B (λ)} x (λ) dλ.

Similarly,

[0057]

## EQU7 ## Y = rY _R + gY _G + bY _B Z = rZ _R + gZ _G + bZ _B

When these are represented by a matrix, Equation 8 is obtained.

[0059]

(Equation 8)

On the other hand, when light is received at spectral sensitivities x ′ (λ), y ′ (λ) and z ′ (λ) that do not match the color matching function of CIE,

[0061]

X ′ = ∫P (λ) x ′ (λ) dλ = r∫R (λ) x ′ (λ) dλ + g∫G (λ) x ′ (λ) dλ + b∫B (λ) x ′ ( λ) dλ = rX ′ _R + gX ′ _G + bX ′ _B , X ′ _R = ∫R (λ) x (λ) dλ X ′ _G = ∫G (λ) x (λ) dλ X ′ _B = ∫B (λ ) x (λ) dλ.

Similarly,

[0063]

Y ′ = rY ′ _R + gY ′ _G + bY ′ _B Z ′ = rZ ′ _R + gZ ′ _G + bZ ′ _B

When these are represented by a matrix, Equation 11 is obtained. Equation 12 is obtained from Equation 11. And Equation 8 and Equation 1
From Equation 2, Expression 13 is obtained.

[0065]

[Equation 11]

[0066]

(Equation 12)

[0067]

(Equation 13)

As described above, by calculating the matrices A and A'- ¹ in advance and storing them in the ROM 21, the outputs X ', Y',
True tristimulus values X, Y, and Z can be calculated from Z ′.

The data processing unit 2 is also adapted to perform an operation for correcting a shift in white color. That is, the matrices A and A ′ ⁻¹ and the matrix B shown in Expression 14 are calculated in advance, and the matrix B × A × A ′ ⁻¹ is calculated, and the calculation result is stored in the ROM 21 of the data processing unit 2.
To be stored. Then, the true tristimulus values X, Y, and Z are calculated by using Equation 14 to correct the deviation in white.

[0070]

[Equation 14]

As described above, since the true tristimulus values X, Y, Z are calculated for each pixel of the image pickup means 14, the chromaticity x, y is calculated by equation (4). Further, the luminance becomes Y.

A specific calibration light source is used when obtaining the matrices B, A, and A'- ^1. However, the measurement accuracy is determined by matching the spectral characteristics of the light source with the spectral characteristics of the device under test. Can be improved.

Next, the operation of this device will be described.
If, for example, a liquid crystal module with a built-in backlight is disposed at the front focal point of the objective lens 11, the light beam emitted from a certain area on the liquid crystal module surface will be on the rear focal plane of the objective lens 11 and The light is condensed at a position corresponding to the direction, and a two-dimensional angle image i is formed.

The angle image i is color-separated by each optical filter of the filter 13 and received by the image pickup means 14 to be converted into an electric signal. At this time, the optical filters are sequentially replaced by a motor or the like as the filter 13, and the color matching function x (λ),
Electric signals corresponding to y (λ) and z (λ) are sequentially output.

Then, the electric signal is subjected to arithmetic processing in the data processing unit 2 according to the above-described procedure, and the luminance and chromaticity of the angle image i are obtained. Then, as described above, the inclination angle θ and the incident azimuth φ of the measurement beam with respect to the optical axis L are determined from the coordinates of the angle image i in the UV orthogonal coordinate system. Optical angle characteristics of luminance and chromaticity are obtained for the angle θ and the incident direction φ.

As described above, according to the present embodiment, the angle characteristic of the tristimulus value is obtained by performing color separation with the filter 13, so that the angle characteristic of the luminance and the chromaticity of the measured object can be measured. Can be. Also, since there is no mechanical scanning, the measurement time can be greatly reduced.

For example, when the object to be measured is a liquid crystal module with a built-in backlight, the luminance and chromaticity of the white light can be measured by measuring with all three primary colors of R, G, and B turned on. . Further, when the measurement is performed in a state where only R is turned on and G and B are turned off, R, that is, red luminance and chromaticity can be measured.

The object to be measured is not limited to the liquid crystal module, and the optical angle characteristics of luminance and chromaticity can be similarly calculated for a general self-luminous object.

Further, by displaying the result of each pixel of the image pickup means 14 two-dimensionally on the color monitor 4, it is possible to create a distribution diagram of luminance and chromaticity when viewed from various directions. .

The position of the filter 13 is not limited to the position between the reduction lens 12b and the image pickup means 14, but the same effect can be obtained if it is between the measurement surface S and the image pickup means 14.

The filter 13 may be an integral type formed on the CCD (pixel) of the image pickup means 14 corresponding to each CCD (pixel). The imaging means 14 in this case corresponds to a device in which R, G, B color filters in a normal color CCD are replaced with optical filters corresponding to color matching functions x (λ), y (λ), z (λ). I do. When such an imaging unit 14 is used, an output of an electric signal corresponding to the tristimulus values X, Y, and Z can be obtained by one measurement. However, since the spectral sensitivity of the optical filter corresponding to each pixel is different, one color is obtained by three adjacent pixels, and if the pixel pitch is the same, the spatial resolution of the imaging unit 14 is reduced to 1/3. descend.

Incidentally, the color matching function x (λ) is λ ≒ 500 nm
X ≒ 0, and has two local maxima on both sides.

[0083]

X (λ) = x ₁ (λ) + x ₂ (λ)

[0084]

X = X ₁ + X ₂

Accordingly, the filter 13 has a color matching function x (λ)
Instead, a four-element configuration may be used using an optical filter approximating x ₁ (λ) and x ₂ (λ). In this case, X is X ₁ or X ₂ in each equation, and X ₁ , X ₂ ,
After calculating Y and Z, if X is calculated using Equation 16, tristimulus values X, Y and Z are obtained.

Since X ₁ can be approximated to 0.1672Z,
Equation 16 is

[0087]

X = X ₁ + X ₂ = 0.1672Z + X ₂

Therefore, the filter 13 has a color matching function x (λ)
Instead of using an optical filter approximating x ₂ (λ)
It is good also as a sheet composition. In this case, X in each formula
Is defined as X _2, and after calculating X ₂ , Y, and Z according to Equation 13,
When X is calculated using Expression 17, tristimulus values X, Y, and Z are obtained.

Next, a first embodiment for correcting a measurement error due to polarization of light emitted from an object to be measured will be described with reference to FIGS. FIG. 1 is a diagram showing a lens 11a which is one lens constituting the objective lens 11. FIG. In the first embodiment, as shown in FIG. 1, a multi-layer deposited film W1 to W
5 is given.

This multilayer vapor deposition film needs to satisfy the following points. It should be given priority to suppress the reflectance difference between the P component and the S component. However, if the absolute reflectance is high, it leads to a decrease in measurement light, an increase in ghost and flare caused by the lens, and causes a measurement error. To suppress both the reflectance difference between the P component and the S component and the absolute value of the reflectance. Since the range of the viewing angle to be measured is wide, the above must be satisfied up to the range where the incident angle of the measuring light is large. Since the color of the object to be measured is measured, the above condition must be satisfied in the range of visible light, that is, in the wavelength range of 400 nm to 700 nm.

Table 1 below shows the refractive indices of the multilayer vapor-deposited films satisfying the above conditions. The vapor-deposited films of the first layer W1 to the fifth layer W5 are arranged from the air side to the lens substrate side. Coated on the surface.

[0092]

[Table 1]

In general, the P component and the S component of linearly polarized light have the same wavelength, behave differently even when passing through a deposited film having the same refractive index and the same thickness, and have different reflectances. . Therefore, the first layer W1 to the fifth layer W shown in Table 1 above
5 is coated on the surface of the lens substrate,
The difference between the reflectances of the P component and the S component can be reduced on average by the interference of light in each layer.

Table 2 below shows the first layers W1 to W1 shown in Table 1 above.
It shows a preferred example of a deposited film composed of a fifth layer W5.

[0095]

[Table 2]

FIGS. 2 to 5 show the reflectance of the P component and the S component in the visible light range having a wavelength of from 400 nm to 700 nm. FIG. 2A shows the present embodiment, that is, FIG. (B) shows a comparative example, that is, a lens provided with a five-layer antireflection film described in JP-B-54-38904. The incident angles in each figure are 0 ° in FIG. 2, 60 ° in FIG. 3, 70 ° in FIG. 4, and 80 ° in FIG.

As shown in FIGS. 2A and 2B, when the incident angle is 0 °, there is no difference between the reflectances of the P component and the S component in both the present embodiment and the comparative example. In the comparative example, reflection is better prevented over the entire visible light range.

However, as the incident angle increases, in the comparative example, FIGS. 3 (b), 4 (b), and 5 (b)
As shown in the figure, the average value of the difference between the reflectances of the P component and the S component is large. On the other hand, in the present embodiment, as shown in FIGS. 3A, 4A, and 5A, the average value of the difference between the reflectances of the P component and the S component as compared with the comparative example. Is well suppressed.

When the deposited films of the first layer W1 to the fifth layer W5 shown in Table 2 are coated on the surface of the lens substrate, FIG.
As shown in (a), FIG. 4 (a), and FIG. 5 (a), the magnitudes of the reflectances of the P component and the S component are reversed at a certain wavelength. For example, in FIG. 3A, the reflectance of the P component and the reflectance of the S component are reversed around the wavelengths of 420 nm and 570 nm. That is, in the vicinity of wavelengths of 420 nm and 570 nm, the reflectances of the P component and the S component match. By performing the coating shown in Table 2 above, the difference between the reflectances of the P component and the S component is reduced on average in a wavelength range where the reflectance does not match.

FIG. 6 is a diagram showing the transmittance of the P component and the S component of all the lenses constituting the objective lens 11 according to the present embodiment and the comparative example. In FIG.
P 'and S' show the case of the comparative example. As shown in FIG. 6, according to the present embodiment, P
The difference in transmittance between the component and the S component is better suppressed than in the comparative example.

In the present embodiment, the coating of the multi-layered vapor-deposited film is applied only to the necessary lens among the plurality of lenses constituting the objective lens 11, that is, the lens having a large incident angle of the measuring light due to the configuration. It has been subjected. Also, not only Table 2 but also Table 1 according to the refractive index of each lens.
Are coated with a plurality of types of multi-layer deposited films. Thereby, as shown in FIG. 6, good transmission characteristics with a small difference in transmittance between the P component and the S component are obtained.

As described above, according to the first embodiment, the surface of the lens constituting the objective lens 11 is coated with a multilayer vapor-deposited film. The difference between the reflectance of the component and the reflectance of the S component can be reduced, whereby the measurement error of the color and luminance of the device under test caused by the difference in reflectance can be reduced, and highly accurate measurement can be performed.

Next, a second embodiment for correcting the polarization characteristics of the optical angle characteristic measuring apparatus according to the present invention will be described. FIG. 7 is a configuration diagram of an illumination light source for polarization correction. In the second embodiment, the polarization characteristics of the measurement device are obtained in advance using the illumination light source 5 for polarization correction, and the measurement values are corrected using the results.

The illumination light source 5 for polarization correction is arranged to face the measuring head 1 on the optical axis L and across the measurement surface S when performing the measurement for polarization correction. The measuring surface S is composed of a plate 15 and a rotation holding portion 16 and the like.
Is illuminated from the back side.

The integrating sphere 50 has an inner wall coated with a white diffuse reflection paint such as MgO or BaSO _4, provided with a sample opening 501 and a light source opening 502, and mixes the light beam 52 incident from the light source opening 502. The calibration plate 15 arranged on the measurement surface S of the sample opening 501 is diffused and illuminated, and the optical axis of the illumination light emitted from the sample opening 501 coincides with the optical axis L of the measurement head 1. They are arranged to match.

The lamp 51 is composed of, for example, a fluorescent lamp or the like.
It is arranged near the light source opening 502 of the integrating sphere 50 and is turned on by the host computer 3 via a light emitting circuit (not shown).
The light is controlled to be turned off.
Are incident on the integrating sphere 50 through the opening 502.

The sample opening 501 is provided so as to illuminate a wider area than the area of the measurement surface S covering the incident angle of the light beam that can be measured by the optical system of the measurement head 1. Further, the light source opening 502 is provided at a position beyond the maximum incident angle theta _M measurable by the optical system of the measuring head 1. Thereby, it is possible to prevent the occurrence of uneven illumination due to the opening.

As the calibration plate 15 disposed on the measurement surface S of the sample opening 501, a diffusion plate 15a and a polarizer 15b
Can be installed. The diffusion plate 15a transmits non-polarized diffused light and emits it to the measurement head 1, and the polarizer 15b transmits only linearly polarized light having a predetermined polarization plane and emits it to the measurement head 1. is there. The rotation holding unit 16 includes a holding unit that rotatably holds the calibration plate 15 and a motor that rotationally drives the holding unit.
This is to rotate the polarizer 15b mounted as described above.

In the second embodiment, the data processing unit 2 performs a correction operation described later, and the input unit 31 of the host computer 3 comprises a keyboard.
This is for inputting measurement data of the polarization direction φ and the degree of polarization K of the object to be described later.

Next, the measurement procedure will be described with reference to FIG. FIG. 8 is a diagram illustrating the polarization characteristics of this device. The polarization characteristics of the device are measured, and the R
It is stored in the OM 21 in advance. That is, first, non-polarized light is measured with the diffusion plate 15a as the calibration plate 15 mounted on the polarization correction illumination light source 5 (P in FIG. 8), and then the polarizer 15b is mounted as the calibration plate 15 and rotated. The polarizer 15b is rotated by the holding unit 16 to measure linearly polarized light using the vibration direction as a parameter (Q in FIG. 8). Then, a deviation ΔI% of the measured value with respect to the oscillation direction φ of the linearly polarized light is obtained and stored in the ROM 21 of the data processing unit 2 in advance.

By a known method using a polarizer or the like,
The polarization direction φ and the degree of polarization K of the device under test are measured, and the data is input using the input unit 31. The degree of polarization K is K ≦ 1
In the case of perfect polarization, K = 1.

[0112]

M _C = M / (1 + ΔI · K / 100) ΔI is determined from the input polarization direction φ, and the above equation (18) is calculated using the ΔI and the degree of polarization K for the measured value M of the object to be measured.
Performs correction calculation according, obtaining a correction value M _C.

The measurement of linearly polarized light with the vibration direction stored in the ROM 21 as a parameter, that is, Q in FIG.
Assuming that the vertical direction is 0 °, 180 points may be measured every 1 °, or 6 points may be measured every 30 °. When the vibration direction φ of the object to be measured is intermediate between the data stored in the ROM 21, interpolation may be performed.

As described above, according to the second embodiment, the polarization characteristics of the device are measured in advance and stored in the ROM 21,
Since a value obtained by correcting the measured value of the object to be measured using the polarization characteristics is used as the measurement result, the polarization characteristic of the device causes the difference in reflectivity between the P component and the S component of the incident measurement light to be generated. Reduce the measurement error of the color and brightness of the measured object,
Highly accurate measurement can be performed. Therefore, even when not only the objective lens 11 and the relay lens system 12 but also the imaging unit 14 has polarization characteristics, highly accurate measurement can be performed.

When the polarization degree of the object to be measured can be approximated to K = 1, K = 1 is set in the above equation (18), and the measurement and input of the polarization degree K may not be performed.

Next, a description will be given of a third embodiment for correcting the polarization characteristics of the optical angle characteristic measuring device according to the present invention. FIG. 9 is a main part configuration diagram of the third embodiment. The third embodiment includes a polarization switching unit 6 disposed between the DUT 10 and the measuring head 1 and a rotation holding unit 7 that holds the polarization switching unit 6.

The polarization switching section 6 is composed of a half-wave plate for rotating the plane of polarization of linearly polarized light. The rotation holding unit 7 includes a holding unit 71 that rotatably holds the polarization switching unit 6 and a motor 72 that rotates the holding unit 71, and rotates the polarization switching unit 6.

The host computer 3 controls the operation of the rotation holding unit 7 as shown in a measurement procedure example described later, and the data processing unit 2 performs correction calculation as shown in the measurement procedure example described later. Is what you do.

Next, measurement procedures (1) and (2) will be described. (1) The polarization switching unit 6 is rotated at a constant speed, and the time for one rotation is T
Then, so that nT / 2 = light receiving time (n: integer),
The measurement is performed by controlling the operations of the rotation holding unit 7 and the imaging unit 14. (2) When a half-wave plate is used as the polarization switching unit 6,
The polarization switching unit 6 is rotated by a predetermined angle, and the average value of the measured values at each angular position is set as the measured value. For example, the polarization switching unit 6 is rotated by π / 4m for 2 m times (where m ≧ 1), and the measured value obtained each time the light is rotated is stored in the RAM 22, and the average value of the measured values for 2m times is calculated. Let it be the measurement result.

Note that a Faraday cell may be used as the polarization switching section 6. A Faraday cell is a polarization plane rotation device that uses the Faraday effect in which the direction of oscillation, that is, the plane of polarization, rotates when linearly polarized light passes through the cell in the direction of a magnetic field. In this case, since the rotation angle of the polarization plane is proportional to the strength of the magnetic field, instead of a mechanism for rotatably holding the Faraday cell, an AC voltage applying unit for changing the strength of the magnetic field is provided, and the vibration direction is provided. May be changed over time.

As described above, according to the third embodiment, the measurement is performed by rotating the oscillation direction of the linearly polarized light of the light emitted from the object to be measured. In this case, it is possible to reduce the measurement error of the color and luminance of the object to be measured caused by the difference between the reflectances of the P component and the S component, and to perform highly accurate measurement. Therefore, the objective lens 11
Even if not only the relay lens system 12 but also the imaging means 14 has polarization characteristics, highly accurate measurement can be performed.

The present invention is not limited to the above-described embodiments, but may employ a combination of the first and second embodiments. That is, at least a part of the lens constituting the objective lens 11 is coated with a multilayer vapor-deposited film as shown in Table 1 above, and the polarization characteristics of the device are measured and stored in the ROM 21. Alternatively, a value obtained by correcting the measurement value of the device under test may be used as the measurement result.

Further, the present invention relates to the first embodiment and the third embodiment.
A form in which the embodiment is combined may be adopted. That is, at least a part of the lens constituting the objective lens 11 is coated with a multilayer vapor-deposited film shown in Table 1 above, and the measurement is performed by rotating the oscillation direction of the linearly polarized light of the light emitted from the object to be measured. It may be.

According to these embodiments, even when the light emitted from the object to be measured is linearly polarized light, the measurement error of the color and luminance of the object to be measured caused by the linearly polarized light is further reduced, and the measurement accuracy is further improved. be able to.

[0125]

As described above, according to the first aspect of the present invention, a coating film composed of a plurality of layers is formed on at least one of a plurality of lenses constituting a lens system. Even if the light emitted from the measurement surface of the device under test has polarized light, the difference between the reflectances of the P component and the S component in the lens system can be reduced over the visible wavelength range. The measurement error caused by the difference between the two can be reduced, and the luminance of the DUT having a wide viewing angle can be measured with high accuracy.

Further, an objective lens group for forming an angular image based on light from the measurement surface of the object to be measured arranged in the vicinity of the front focal point on the rear focal plane and the angular image on the imaging plane of the imaging means are reproduced. Of a lens system consisting of a relay lens group to form an image,
By forming the coating film on at least one of the lens groups, even if the light emitted from the measurement surface of the object to be measured has polarized light, the difference between the reflectances of the P component and the S component in the lens system can be reduced to a visible wavelength. Thus, the measurement error caused by the difference in reflectance can be reduced, and the luminance of an object to be measured with a wide viewing angle can be measured with high accuracy.

Further, the coating film is composed of a first layer, a second layer, and a third layer which are sequentially laminated from the air side to the lens substrate side.
Layer, a fourth layer, and a fifth layer, and the refractive indices n ₁ , n ₂ , n ₃ , n ₄ , and n ₅ of the respective layers are n ₁ <1.4, n ₂ > 2.0, 1.4
By setting ≦ n ₃ ≦ 2.0, n ₄ <1.4, 1.4 ≦ n ₅ ≦ 2.0, even if the light emitted from the measurement surface of the DUT has polarized light, the P component and the S component The difference in reflectance can be reduced over the visible wavelength range, whereby the measurement error caused by the difference in reflectance can be reduced, and the luminance of the DUT with a wide viewing angle can be measured with high accuracy. .

According to the fourth aspect of the present invention, the polarization characteristics of the light emitted from the measurement surface of the object to be measured are stored by storing the polarization characteristics of the image data obtained by the imaging means using the polarization direction obtained in advance as a parameter. The corresponding polarization characteristics are extracted from the stored polarization characteristics using the above, and the imaging data of the imaging unit is corrected using the extracted polarization characteristics. A measurement error caused by having polarized light can be reduced, and thereby, the luminance of an object to be measured having a wide viewing angle can be measured with high accuracy.

According to the fifth aspect of the present invention, the polarization direction changing means for changing the polarization direction of the light emitted from the measurement surface of the measurement object is provided between the measurement object and the lens system. Since the average value of the imaging data in each of the changed polarization directions is obtained, it is possible to reduce a measurement error caused by the fact that light emitted from the measurement surface of the device to be measured has polarized light, thereby providing a wide visual field. The luminance of the measured object at the corner can be measured with high accuracy.

Further, by causing the image pickup means to pick up an image with a spectral sensitivity close to the color matching function and calculating tristimulus values for each pixel from the image pickup data by the image pickup means, the color of the DUT having a wide viewing angle can be obtained. It can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a lens constituting an objective lens of a first embodiment for correcting a polarization characteristic of an optical angle characteristic measuring device according to the present invention.

FIG. 2 is a diagram showing reflectances of a P component and an S component in a visible light range of a wavelength of 400 nm to 700 nm when an incident angle is 0 °,
(A) shows the case of the present embodiment, and (b) shows the case of the comparative example.

FIG. 3 is a diagram showing reflectances of a P component and an S component in a visible light range of a wavelength of 400 nm to 700 nm when an incident angle is 60 °,
(A) shows the case of the present embodiment, and (b) shows the case of the comparative example.

FIG. 4 is a diagram showing reflectances of a P component and an S component in a visible light range of a wavelength of 400 nm to 700 nm when an incident angle is 70 °,
(A) shows the case of the present embodiment, and (b) shows the case of the comparative example.

FIG. 5 is a diagram showing reflectances of a P component and an S component in a visible light range of a wavelength of 400 nm to 700 nm when an incident angle is 80 °,
(A) shows the case of the present embodiment, and (b) shows the case of the comparative example.

FIG. 6 is a diagram showing the transmittances of the P component and the S component of all the lenses constituting the objective lens according to the first embodiment and the comparative example of the optical angle characteristic measuring device according to the present invention.

FIG. 7 is a configuration diagram of a polarization correction illumination light source included in a second embodiment for correcting the polarization characteristics of the optical angle characteristic measurement device according to the present invention.

FIG. 8 is a diagram illustrating polarization characteristics of the optical angle characteristic measuring device.

FIG. 9 is a main part configuration diagram of a third embodiment for correcting a polarization characteristic of the optical angle characteristic measurement device according to the present invention.

FIG. 10 is a diagram showing an embodiment of an optical angle characteristic measuring device according to the present invention, wherein (a) is a block diagram showing a control configuration, and (b) is an overall configuration diagram.

FIG. 11 is an internal configuration diagram of a measuring head used in the embodiment.

FIG. 12 is a diagram illustrating the relationship between the direction of a measurement light beam emitted from a measurement surface and an angle image i.

FIG. 13 is a diagram illustrating a lens configuration example of an objective lens.

FIG. 14 is a diagram for explaining a P component and an S component in an objective lens when incident light is linearly polarized light.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Measuring head 10 Object to be measured 11 Objective lens (lens system) 12 Relay lens system (lens system) 12a Field lens 12b, 12c, 12d Reduction lens 13 Filter (color separation means) 14 Imaging means 15 Calibration plate 15a Diffusion plate 15b Polarization Child 16 rotation holding unit 2 data processing unit (correction unit, average calculation unit, stimulus value calculation unit) 21 ROM (storage unit) 22 RAM 3 host computer 31 input unit (input unit) 4 color monitor 5 polarization correction illumination light source 50 Integrating sphere 51 Lamp 6 Polarization switching unit (polarization direction changing means) 7 Rotation holding unit W1 to W5 First layer to fifth layer (coating film)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaru Okumura 2-3-13 Azuchicho, Chuo-ku, Osaka City Inside Osaka International Building Minolta Co., Ltd. (72) Hirozo Tani 2-chome Azuchicho, Chuo-ku, Osaka-shi No. 13 Osaka International Building Minolta Co., Ltd. (72) Inventor Iwao Usui 2-3-13 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd.

Claims (6)

[Claims] 1. An imaging system comprising: a lens system for forming an angle image based on light from a measurement surface of an object to be measured; and a plurality of pixels arranged two-dimensionally, and for imaging the formed angle image. Means, the lens system is composed of a plurality of lenses, at least one of the plurality of lenses is formed with a coating film composed of a plurality of layers, the polarized light of the DUT An optical angle characteristic measuring device, wherein a difference between reflectances of a P component and an S component of light emitted from a measurement surface in the lens system is reduced over a visible wavelength range. 2. The lens system according to claim 1, further comprising: an objective lens group configured to form an angular image based on light from a measurement surface of the object to be measured disposed in the vicinity of a front focal point on a rear focal plane; 2. The optical angle characteristic measuring apparatus according to claim 1, further comprising: a relay lens group for re-imaging an image on the imaging surface, wherein the coating film is formed on at least one of the lens groups. 3. The coating film includes a first layer, a second layer, a third layer, a fourth layer, and a fifth layer sequentially laminated from the air side to the lens substrate side. Rates n ₁ , n ₂ ,
n ₃ , n ₄ and n ₅ are n ₁ <1.4, n ₂ > 2.0, 1.4 ≦ n ₃ ≦ 2.
An optical angle characteristic measuring device, wherein 0, n ₄ <1.4, 1.4 ≦ n ₅ ≦ 2.0. 4. A lens system for forming an angle image based on light from a measurement surface of an object to be measured, and an imaging system comprising a plurality of pixels arranged two-dimensionally and capturing the formed angle image. Means, storage means for storing polarization characteristics of image data obtained by the imaging means using the previously determined polarization direction as a parameter, input means for inputting the polarization direction of light from the measurement surface of the device under test, And extracting a corresponding polarization characteristic from the polarization characteristic stored in the storage unit using the polarization direction, and correcting the image data by the imaging unit using the polarization characteristic. Characteristic optical angle characteristic measuring device. 5. An imaging system comprising a lens system for forming an angle image based on light from a measurement surface of an object to be measured and a plurality of pixels arranged two-dimensionally, and for capturing the formed angle image. Means, disposed between the object to be measured and the lens system, the polarization direction changing means for changing the polarization direction of light from the measurement surface of the object to be measured, and the polarization direction in each of the changed polarization direction An optical angle characteristic measuring device, comprising: an average calculating means for calculating an average value of image data obtained by the imaging means. 6. An optical angle characteristic measuring device according to claim 1, wherein said color separation means causes said image pickup means to pick up an image with a spectral sensitivity close to a color matching function, and said image pickup means. An optical angle characteristic measuring device comprising: a stimulus value calculating means for calculating a tristimulus value for each pixel from image data.