JP3350244B2 - Method and apparatus for measuring transmission strain - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the degree of distortion of a light-transmitting object such as a glass plate or a curved glass plate. In particular, the present invention relates to a transmission distortion measuring method for measuring a degree of distortion based on light transmitted through a light-transmitting object to be measured, and an improvement of an apparatus therefor.

[0002]

2. Description of the Related Art Generally, when the degree of distortion of a window glass of a vehicle window glass or an architectural window glass is large, there is an adverse effect that an external view seen through the window glass is distorted. Therefore, for quality control, it is necessary to keep the degree of distortion of the window glass within a predetermined range.

[0003] Conventionally, examples of this type of window glass strain measurement technique include the following. The transmission strain of the measured object is calculated by evaluating the vertical and horizontal diameters of polka dot data photographed through the measured object such as a window glass using a regular pattern composed of polka dots. Using a regular pattern consisting of points such as laser light arranged at predetermined pitch intervals along the vertical direction and the horizontal direction, the distance change between the discrete bright point coordinates of the point group photographed through the object to be measured. Then, the transmission strain of the device under test is calculated.

[0004] As another technique for measuring the strain of window glass of this type, there is a technique disclosed in, for example, JP-A-3-199946. In this method, a screen for irradiating a predetermined bright line is installed on the back surface of an object to be measured such as a window glass, and an imager such as an ITV camera is installed in front of the object to be measured. A bright line is photographed through the object to be measured over the entire area of the object to be measured, and the transmission distortion of the object to be measured is measured from the photographed data.

[0005]

However, in the method for evaluating the vertical and horizontal diameters of a polka dot pattern, for example, the center position of the polka dot pattern is accurately detected in order to accurately determine the vertical and horizontal diameters. There must be. For this reason, the processing for measuring the transmission distortion becomes complicated due to restrictions on the resolution of the imaging system and the like required when performing processing using an ITV camera or the like, and an extremely long processing time is required. On the other hand, in the method using a regular pattern composed of point group arrays, transmission distortion is calculated based on the distance between points.
Therefore, in order to accurately measure transmission distortion, distance data between points is required at a relatively high density, and a correspondingly large measurement range of the object to be measured by the imager cannot be secured. Conversely, if the data density of the distance between points is made coarse, the risk of overlooking local distortion existing between points increases.

[0006] Further, in any of the transmission strain measuring methods, I
While moving an image pickup device such as a TV camera, a polka dot pattern or a group of points is photographed through an object to be measured. Therefore, due to mechanical vibration or the like when moving the imager,
An error easily occurs in the measurement distance. Furthermore, since the imaging range of the imaging device at one time is narrow, it is necessary to repeat the movement and imaging processing many times. Thus, a correspondingly long processing time is required. When an imager is used, the defocus may occur. Therefore, the dimensional error of the vertical diameter and the horizontal diameter of the polka dot pattern becomes large, and the error of the coordinate position of the discrete luminescent spot of the point group becomes large, and as a result, the technical problem that the measurement accuracy of the transmission distortion decreases. Occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problems, and can accurately measure transmission distortion while minimizing the influence of defocus caused by an image pickup means.
It is an object of the present invention to provide a method and apparatus for measuring a transmission strain which can simplify a measurement process and can easily cope with a wide measurement range.

[0008]

That is, the present invention provides:
As shown in FIG. 1, a background screen 2 on which a predetermined regular pattern 3 is drawn is installed on the back surface of a light-transmitting DUT 1, and an image pickup unit capable of performing line scanning in front of the DUT 1. 4 is set, and the entire area of the measurement range of the DUT 1 is sequentially line-scanned by the imaging means 4, whereby the DUT 1
Is a method of measuring the transmission distortion of the device under test 1 from the photographed data after photographing the background screen 2 through the camera, wherein the regular pattern 3 of the background screen 2 is a triangular wave-shaped unit continuously extending in a predetermined direction. It is characterized in that the patterns 3a are arranged at equal pitch intervals.

In such a method invention, a method for measuring the transmission distortion of the DUT 1 from the photographing data may be appropriately selected. On the other hand, as shown in FIG. 1, a device invention that embodies the method invention is a triangular wave-shaped unit that is installed on the back side of a light-transmitting DUT 1 and extends substantially continuously in a predetermined direction. Background screen 2 having regular pattern 3 in which patterns 3a are arranged at equal pitch intervals
And an image pickup means 4 installed on the front side of the DUT 1 and capable of line scanning, and at least one of the DUT 1, the image pickup means 4 and the background screen 2 are appropriately moved. A measurement range control unit 5 for photographing the background screen 2 through the DUT 1 by sequentially scanning the entire measurement range of the object 1 and a regular pattern of the background screen 2 with the line scanning of the imaging unit 4 A pattern change point detecting means 6 for detecting a change point 3; and a pattern line segment extracting means 7 for extracting each pattern line of the triangular wave unit pattern 3a from the pattern change points detected by the pattern change point detecting means 6. And a feature point calculating means 8 for calculating a feature point from each pattern line segment extracted by the pattern line segment extracting means 7, and feature point coordinates for when the object 1 is not interposed are stored in advance. Reference feature point storing means 9
And the feature point coordinates and the reference feature point storage means 9 via the DUT 1 calculated by the feature point calculation means 8
And distortion evaluation means 10 for evaluating the transmission distortion of the DUT 1 by comparing the characteristic point coordinates with the characteristic point coordinates.

In such technical means, the following are exemplified as the background screen 2. One is to arrange an illuminating light source on the back side of the transmissive screen member on which the opaque regular pattern 3 is drawn,
A light source for illumination is installed on the back side of an impermeable screen member on which a regular pattern of transparency 3 is drawn. A light-transmitting material, and a light-emitting paint or the like in which a regular pattern 3 is drawn on a screen member, and the regular pattern 3 is irradiated with light from the outside may be used. In this way, these or other various means are appropriately selected and used as the background screen 2.

Regarding the arrangement direction of the regular pattern 3,
You can select any direction determined in advance,
Considering the easiness of processing, those arranged in the vertical or horizontal direction are preferable. Regarding the shape of the triangular wave unit pattern 3a of the regular pattern 3, the inclination angles θ1 and θ2 of the triangular wave unit pattern 3a with respect to a reference line (a line extending in a direction perpendicular to the arrangement direction of the regular pattern 3) are θ1.
= Θ2, θ1> θ2 or θ1 <θ2. Considering the easiness of processing, the relationship of θ1 = θ2 is preferable. However, if the inclination angles θ1 and θ2 of the triangular-wave-shaped unit pattern 3a are too small, the hatched portion of the triangular-wave may become unrecognizable due to distortion.
゜ is appropriately selected. The arrangement pitch P1 of the triangular wave unit patterns 3a may be appropriately selected within a range that can be resolved by the resolution of the imaging means 4. If the width pitch P of the triangular-wave-shaped unit patterns 3a and the arrangement pitch P1 between the unit patterns 3a are set to be substantially the same, the pattern change points (boundary points of the unit patterns 3a) at the time of scanning have uniform dimensions. It is possible to easily distinguish between a pattern change point and noise.

The imaging means 4 may be appropriately selected as long as it can photograph the background screen 2 through the DUT 1. If a CCD line sensor camera, a photo sensor arranged in a matrix, and an image sensor arranged in each pixel unit are used for the imaging means 4, the presence or absence of light reception in each pixel unit can be easily measured, and the data It is preferable from the viewpoint that the handling of the material becomes easy. The scanning direction of the imaging means 4 is arbitrary. Considering the easiness of the processing, the scanning direction of the imaging means 4 is set to the triangular wave unit pattern 3
a in the arrangement direction (in other words, the triangular wave unit pattern 3
(a direction perpendicular to the direction in which a extends).

As the measuring range control means 5, the DUT 1
Is required to be able to be photographed by the imaging means 4 and the regular pattern 3 on the background screen 2 can be photographed via the DUT 1. For example, the DUT 1
Alternatively, the imaging unit 4 may be appropriately step-moved (rotated or linearly moved), the imaging unit 4 and the DUT 1 may be respectively step-moved, or the imaging unit 4 and the background screen 2 may be appropriately step-moved. The measurement range is controlled by selection.

The pattern change point detecting means 6 may be appropriately selected as long as it detects a boundary point of the regular pattern 3 traversed by the scanning line of the imaging means 4. It is preferable to employ an edge detection method that can accurately detect the boundary points of the regular pattern 3 even if the image captured by the imaging unit 4 is out of focus.

The pattern line segment corresponds to each side of the triangular wave unit pattern 3a. The pattern segment extracting means 7 for recognizing the pattern segment can be appropriately selected as long as the pattern segment is extracted from the locus of the extracted pattern change point. In order to accurately extract a pattern line segment, the pattern line segment extraction means 7 determines, for example, a least square approximation straight line based on the pattern change point sequence, or obtains the properties of the regular pattern 3 (the inclination angle, the pattern width pitch, It is preferable to remove noise from the pattern change point sequence in consideration of the pattern pitch).

The feature point calculating means 8 can calculate the feature points of the regular pattern 3 from the extracted pattern line segments, for example, the intersection of each pattern line, the center line of each parallel pattern line, and the like. If there is, you can select it appropriately. As the reference feature points, feature points obtained by directly photographing the background screen 2 without the DUT 1 may be used, or the DUT 1 without transmission distortion may be actually measured. Alternatively, a feature point obtained by theoretically analyzing the regular pattern 3 of the background screen 2 may be used. In the present invention, these are defined as when the object 1 is not substantially interposed.

The distortion estimating means 10 calculates the amount of distortion by comparing the characteristic point calculated by the characteristic point calculating means 8 with the reference characteristic point, displays the numerical value as it is, and allows the operator to calculate the transmission distortion. The magnitude may be evaluated, or after calculating the distortion amount, it may be configured to determine whether or not the distortion amount is within a reference distortion amount that is an allowable range.

[0018]

According to the above-mentioned technical means, the measuring range control means 5 appropriately moves at least one of the device under test 1, the image pickup device 4 and the background screen 2, and the image pickup device 4 The regular pattern 3 of the background screen 2 is photographed through the DUT 1 over the entire measurement range 1. In the regular pattern 3, triangular-wave-shaped unit patterns 3a continuously extending in a predetermined direction, for example, a vertical direction, are arranged at an equal pitch P1. In this case, the triangular wave unit pattern 3a
May be substantially continuous in the vertical direction. For example, there may be an allowable discontinuity in view of the resolution of the imaging unit 4 and the like. For this reason, with the line scanning of the imaging means 4,
The pattern change point detecting means 6 detects a boundary portion of the triangular wave unit pattern 3a crossed by the scanning line as a pattern change point. In such a pattern change point detection process,
Even if the image taken by the imaging means 4 is out of focus, the pattern change point can be accurately detected by appropriately setting the threshold value of the contrast of the transmitted light amount. This is because a point of a constant light amount can be set as a pattern change point by setting a threshold value of the contrast of the transmitted light amount, and this pattern change point is defined by a boundary line (a boundary line) of the triangular wave-shaped unit pattern 3a having a constant arrangement pitch P1. On the edge).

The pattern segment extracting means 7 extracts a pattern segment based on the detected pattern change point. At this time, the pattern change points are to be arranged along the boundary of the triangular-wave-shaped unit pattern 3a (the inclination angles θ1 and θ2 are uniquely determined in advance).
Even if the transmission distortion is large to some extent, it is expected that the pattern change points are arranged substantially along the inclination angle of the triangular-wave-shaped unit pattern 3a, and accordingly, the pattern line segment is easily extracted from the pattern change point sequence.

Thereafter, the feature point calculating means 8 calculates a feature point such as an intersection of each pattern line from the extracted pattern line. In this way, the feature point coordinates calculated by the strain evaluation unit 10 and the feature point coordinates of the reference feature point storage unit 9 are compared, and the transmission distortion of the DUT 1 is evaluated.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the accompanying drawings. 2 and 3 show an embodiment of a transmission strain measuring apparatus to which the present invention is applied. In the figure, reference numeral 20 denotes a workpiece (in this embodiment, a windshield of an automobile) as an object to be measured. This work 20
Is held in a predetermined inclined posture on a rotatable work table 21 via a holder 22.
Reference numeral 23 denotes a table drive motor for rotating the work table 21 within a predetermined angle range (about 160 ° in this embodiment), and reference numeral 24 denotes a vertical movement of the work 20 by adjusting the position of the holder 22 on the work table 21. This is a work position adjustment actuator for adjusting a position and a posture angle.

Reference numeral 30 denotes a background screen provided on the back side of the work 20. This background screen 30
A light-transmitting screen sheet 31 is provided on the front surface of a screen frame (not shown), and a predetermined light-impermeable regular pattern 32 is formed on the surface of the screen sheet 31.
Is provided. Further, on the back side of the screen sheet 31, a number of rod-shaped light sources 33 are vertically arranged at predetermined pitch intervals so that the screen sheet 31 is irradiated with light from the back side.

In this embodiment, the regular pattern 32 is formed, as shown in FIG. 4, by forming a triangular-wave-shaped unit pattern 321 extending in the vertical direction at a predetermined pitch P1 (7.5 mm in this embodiment) in the horizontal direction. They are arranged in a range of M × N (780 × 3420 mm in this embodiment) as a whole. Here, the triangular-wave-shaped unit pattern 321 has a width dimension pitch P (7.5 mm in this embodiment) and a pitch P2 in the vertical direction at an inclination angle of 45 ° with respect to a horizontal reference line (this embodiment). Is formed every 7.5 mm).

Reference numeral 40 denotes a CCD line sensor camera (hereinafter referred to as a CC in this embodiment) installed on the front side of the work 20.
D camera). In this embodiment, 4096 CCDs are used as an image sensor, and the CCDs are driven by a two-phase driving method (a method in which odd-numbered CCD groups and even-numbered CCD groups are driven in two phases). Has become. The distance between the CCD camera 40 and the screen sheet 31 of the background screen 30 is set to about 3 m in this embodiment. The above CCD camera 40
Is fixedly installed on a movable support bracket 41 rotatable around a horizontal axis. By transmitting the rotational movement of the camera rotation servomotor 42 to the movable support bracket 41 via the transmission gear 43, the tilt posture can be changed. In this embodiment, the above CC
The elevation angle α and the depression angle β of the D camera 40 are set so as to be about + 35 ° to −25 °. Reference numeral 44 denotes a CCD camera 40 mounted on the rotating shaft of the movable support bracket 41.
Is a rotary encoder that detects the attitude angle of the robot.

Reference numeral 50 denotes a sequence control unit for automatically controlling a series of photographing processes by the CCD camera 40. This sequence control unit 5
0 generates a motor drive signal from the motor controller 51, controls the drive of the table drive motor 23 and the camera rotation servomotor 42 via the drivers 52 and 53, and controls the CCD camera 40 via the camera drive unit 54.
Is controlled. When the processing sequence of the sequence control unit 50 is set or changed, a direct instruction is given at the console 55 or based on an instruction signal from an image processing control unit 60 described later. What should I do?

Reference numeral 60 denotes an image processing control unit connected to the CCD camera 40, the rotary encoder 44, and the sequence control unit 50 via an input / output interface 61. This unit 60 processes the photographing data of the CCD camera 40 and
Various information including transmission distortion of 0 is obtained, and the information is output to the monitor 62 and the printer 63.

Next, details of the input / output interface 61 used in this embodiment will be described. FIG. 5 shows a configuration of a sensor interface board 70 for receiving a signal from the CCD camera 40 in the input / output interface 61. In the figure, reference numeral 71 denotes an analog-to-digital converter for converting an input analog signal into digital data; 72, a FIFO line buffer for sequentially storing digital data for one line scan of the CCD camera 40;
3 is shading &
A data correction circuit for performing mask control; 74, a ring-shaped frame memory for temporarily storing digital data for which the correction processing of the data correction circuit 73 has been completed; and 75, a ring for temporarily storing digital image signals for output. Frame memory (video memory), 76 is a video memory control circuit for controlling reading / writing of the video memory 75, 77 is a digital / analog converter for converting a digital image signal read from the video memory 75 into an analog signal, 78 is a sensor A board control unit in which a program for controlling the interface board 70 is stored, a change point detection unit 79 for performing a pattern change point detection process described later, and a change point detection unit 80
9 is a ring buffer memory for storing the pattern change points detected at 9.

In this embodiment, the analog-to-digital converter 71 basically converts an analog signal into digital data, and furthermore, the odd-numbered and even-numbered CCD replacement sensitivity difference caused by the two-phase driving method of the CCD camera 40. Are averaged to remove noise due to the CCD sensitivity difference.

Next, the processing steps of the transmission distortion measuring apparatus according to this embodiment will be described. Now, the sequence control unit 50 rotates the CCD camera 40 and the work 20 as needed by step rotation, and uses the CCD camera 40 to photograph the regular pattern 32 of the background screen 30 through the work 20 over the entire area of the work 20.

At this time, as shown in FIG. 6, an analog signal is fetched from the CCD camera 40 every time the CCD camera 40 scans a line, and is subjected to A / D conversion. Then, through filtering, shading correction and mask control are performed. Done.

The digital data having undergone such processing is temporarily stored in the frame memory 74. In parallel with this, a change point detection section 79 performs a pattern change point detection process. FIG. 7 shows the details of the process of detecting the pattern change point.
This is schematically shown using. As shown in FIG.
Transparent part / non-transparent part (white,
The pattern (regular pattern 32) pitch (expressed as black) is equal and uniform. This relationship is always maintained even if the scanning position of the CCD camera 40 moves in the sub-scanning direction indicated by the arrow in the figure. Therefore, if the CCD camera 40
Even if the photographed image is out of focus, the white / black pattern has the same pitch, so as shown in FIG.
If the threshold value where the contrast of the received light amount becomes 50% is set as the threshold value, the defocus at the boundary point between the white pattern and the black pattern is canceled. As a result, an accurate pattern change point (edge) (in FIG. 7B, x = x1 to
x7) are detected and sequentially stored in the ring buffer memory 80.

Thereafter, the main CPU (or signal processor) sequentially reads the coordinate data of the pattern change point from the ring buffer memory (change point storage memory) 80, and performs a pattern line segment extraction process. At this time, the pattern change point coordinates should be arranged along the boundary of the triangular wave unit pattern 321. Therefore, even if the workpiece 20 has transmission distortion, it should be recognized continuously at an angle of about 45 ° with respect to a reference line formed of a horizontal line. After removing noise from the pattern change point detected from this viewpoint, a straight line formula of the pattern line segment is calculated by obtaining a least square approximation straight line based on the pattern change point coordinate sequence.

Thereafter, the intersection coordinates of the continuous pattern line as the feature point coordinates are obtained from the straight line equation obtained by the above calculation. At this time, a point at which each pattern line segment intersects at a substantially right angle may be calculated as an intersection. Therefore, it is possible to remove the intersections of the line segments other than the pattern line segments during the calculation process, and only the necessary intersection coordinates are obtained.

Thereafter, the main CPU (or signal processor) performs a distortion evaluation process based on the coordinates of the intersection. Now, assuming that the inspection work 20 is distorted, distortion occurs in the image of the regular pattern 32 obtained by photographing with the CCD camera 40, for example, as surrounded by a broken-line circle in FIG. . For this reason, the pitch of the pattern change point position is disturbed, which affects the inclination of the extracted pattern line segment and is directly reflected on the extracted intersection coordinates. In this embodiment, the intersection coordinates obtained by photographing the background screen 30 without a workpiece, in other words, the intersection coordinates in a state without distortion are stored as reference data in, for example, a disk memory. Then, a matching process is performed between the intersection coordinate data obtained by actually measuring the work 20 and the reference intersection coordinate data, the amount of distortion is obtained by the following calculation, and the amount of distortion of the work 20 can be evaluated.

As shown in FIG. 8 (b), it is assumed that the intersection name corresponding to the reference intersection coordinate data is appended with '. At this time, for example, the vector CD is represented by CD (→), and the inner product of CD (→) and C′D ′ (→) is represented by <CD (→)
* C'D '(→)> and the length of CD (→)
(→) |, the angle θ _H between CD (→) and C′D ′ (→) is θ _H = cos ⁻¹ ｛<CD (→) * C ′
D '(→)> / (| CD (→) | * | C'D' (→)
|)｝. Similarly, CA (→) and C'A '
The angle θ _V formed with (→) is θ _V = cos ⁻¹ ｛<CA
(→) * C'A '(→)> / (| CA (→) | * | C'
A ′ (→) |)}. Thus, the distortion amount θ at the point C
Is obtained by a weighted average value of these two angles (α is a weighting coefficient), and θ = αθ _H + (1−α) θ _V. In this case, if α <0.5, it is possible to obtain a distortion amount in which the distortion in the vertical direction is more important than the distortion in the horizontal direction. In particular, if it is not necessary to place weight in the vertical and horizontal directions, α may be set to 0.5.

When the amount of distortion at each intersection is calculated in this way, it is determined whether or not it is within a predetermined allowable level of the amount of distortion, and the display of the amount of distortion mapping on the monitor 62 and the determination result are displayed. Is output.

As described above, according to the transmission distortion measuring apparatus of this embodiment, the signal from the CCD camera 40 can be processed in real time until the pattern change point is detected, and the main CPU (or signal processor) can process the signal. Since the processing also has a high data compression ratio, high-speed processing can be realized. Also, in this embodiment,
Since the CCD camera 40 is used, a horizontal resolution of about eight times that of a normal ITV camera (about 1/500) can be obtained. Accordingly, as compared with the method of evaluating the vertical and horizontal diameters of the polka dot pattern, not only high-speed processing is possible but also high-precision measurement is possible despite the simple processing. Furthermore, in this embodiment, since the amount of distortion can be calculated from the disturbance of the continuous triangular wave-shaped unit pattern, the regular pattern consisting of the point group sequence is used, and the distortion is calculated based on the change in the discrete luminescent spot coordinates of the point group sequence. Compared to the method of calculating the quantity, it is possible to measure the strain in a narrow narrow area more efficiently.

[0038]

As described above, according to the present invention, the regular pattern drawn on the background screen is devised in the type in which the regular pattern of the background screen is photographed by the imaging means via the measured object. By doing
The transmission distortion can be accurately measured by minimizing the influence of defocus caused by the imaging means, and the measurement process can be simplified and a wide measurement range can be easily accommodated. In particular,
According to the device invention of the present invention, these requests can be reliably and easily realized.

Furthermore, the use of a triangular wave pattern as the regular pattern is particularly effective for measuring the transmission strain of a glass sheet for an automobile. In some cases, the glass plate for an automobile is provided with a ceramic print such as black on a peripheral portion thereof. When the ceramic print and the regular pattern of the background overlap, there is a concern about a detection error of a change point of the pattern. However, since the pattern has a triangular wave shape as in the present invention, it becomes easy to remove the detection data of the ceramic printed portion on the periphery as irregular data. That is, if there is a significant difference between the detected data and the data that will be detected, this data may be removed from the distortion evaluation data. Therefore, when a ceramic printed part is detected, its detection data is based on a pattern along the peripheral shape of the glass plate, so it can be clearly distinguished from this pattern detection data, and the pattern change point is accurately recognized. As a possible pattern shape, a triangular wave pattern is very preferable. By removing the data in this way, it goes without saying that the accuracy of quantifying the amount of distortion is improved. Further, since the portion removed as described above is the peripheral portion of the glass plate, the present invention can also extract the contour shape of the glass plate (measured object).

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a transmission distortion measuring method and apparatus according to the present invention.

FIG. 2 is an explanatory view showing one embodiment of a transmission strain measuring apparatus according to the present invention.

FIG. 3 is a view as viewed from an arrow III in FIG. 2;

FIG. 4 is an explanatory diagram showing a specific example of a regular pattern of a background screen.

FIG. 5 is an explanatory diagram illustrating a specific example of the sensor interface board according to the embodiment;

FIG. 6 is an explanatory diagram illustrating a transmission distortion measuring process according to the embodiment.

FIG. 7A is an explanatory diagram showing a relationship between a regular pattern and a scanning line of a CCD line sensor camera, and FIG. 7B is an explanatory diagram schematically showing a pattern change point detection process.

8A is an explanatory diagram illustrating an example of photographing data when a workpiece has a distortion, and FIG. 8B is an explanatory diagram schematically illustrating a calculation process of a distortion amount.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DUT, 2 ... Background screen, 3 ... Regular pattern, 3a ... Triangular wave unit pattern, 4 ... Imaging means, 5 ...
Measurement range control means, 6 ... Pattern change point detection means, 7 ...
Pattern line segment extraction means, 8 ... feature point calculation means , 9 ... reference feature point storage means, 10 ... distortion evaluation means

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/84-21/958 G01B 11/00-11/30

Claims (4)

(57) [Claims] 1. A background screen (2) in which a predetermined regular pattern (3) is drawn on the back surface of a light-transmitting DUT (1).
On the other hand, an imaging means (4) capable of line scanning is installed in front of the DUT (1), and this imaging means (4) sequentially scans the entire measurement range of the DUT (1). By photographing the background screen (2) through the DUT (1), the transmission distortion of the DUT (1) is measured from the photographed data. A method for measuring transmission distortion, wherein a pattern in which triangular-wave-shaped unit patterns (3a) extending substantially continuously in a predetermined direction are arranged at equal pitch intervals is used as the regular pattern (3). 2. The transmission distortion measuring method according to claim 1, wherein the width dimension of the triangular wave unit pattern is equal to the pitch interval of the triangular wave unit pattern. 3. A regular pattern in which triangular-wave-shaped unit patterns (3a) arranged on the back side of a light-transmissive DUT (1) and extending substantially continuously in a predetermined direction are arranged at equal pitch intervals. A background screen (2) having (3), an image pickup means (4) installed in front of the object to be measured (1) and capable of line scanning, an object to be measured (1), the image pickup means (4) and the background At least one of the screens (2) is appropriately moved, and the entire area of the measurement range of the device under test (1) is sequentially line-scanned by the imaging means (4), so that the background screen ( Measurement range control means (5) for photographing 2)
A pattern change point detecting means (6) for detecting a change point of the regular pattern (3) of the background screen (2) in accordance with the line scanning of the imaging means (4); and a pattern change point detecting means (6) A pattern line segment extracting means (7) for extracting each pattern line segment of the triangular wave-shaped unit pattern (3a) from the pattern change point detected in (1), and each pattern extracted by the pattern line segment extracting means (7) Feature point calculating means (8) for calculating a feature point from a line segment; reference feature point storing means (9) in which feature point coordinates are stored in advance when not passing through the device under test (1); (8)
The transmission distortion of the device under test (1) is evaluated by comparing the feature point coordinates calculated via the device under test (1) with the feature point coordinates of the reference feature point storage means (9). A transmission strain measuring device (10). 4. The transmission distortion measuring apparatus according to claim 3, wherein a width dimension of the triangular wave unit pattern is equal to a pitch interval of the triangular wave unit pattern.