JPH10274508A - Image input device - Google Patents

Abstract

(57) Abstract: Provided is an image input device having a constant luminance value and capable of obtaining image data synchronized with a position. A line sensor including a one-dimensional photoelectric conversion element that captures an image of an object and outputs an image signal, a driving unit that moves the line sensor in a direction perpendicular to a scanning direction thereof,
Position detection means for detecting the position of the line sensor, image pickup control means for acquiring an image signal from the line sensor at regular intervals and outputting the image signal as image data, and a line at the time of output of the image signal detected by the position detection means An image processing device for obtaining a position of image data based on a position of the sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device using a one-dimensional photoelectric conversion element, and more particularly to an image input device for inspection and measurement used for surface inspection of a lead frame or a semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing the principle of a conventional image input device. According to FIG. 6, a line sensor 17 having a one-dimensional photoelectric conversion element whose scanning direction is the X direction, and an XY stage 12 movable in the X direction and the Y direction which is a direction perpendicular to the X direction are provided. . An object to be measured such as a semiconductor wafer (not shown) is placed on the XY stage 12, and an image of the object to be measured is formed on the line sensor 17 via the objective lens 2. 17
Is imaged. The XY stage 12 moves along a guide 3 for guiding it in the Y direction, and the line sensor 2
Each time the XY stage 12 moves a certain distance in the Y direction, an image signal is output as image data in synchronization with an imaging synchronization signal generated from the linear encoder 13, and the image data is stored in a storage unit (not shown).

As described above, the object to be measured is an XY stage 1
2 while being moved at a constant speed in the Y direction, an image is taken by the line sensor 17 whose scanning direction is the X direction. At this time, the electric charges accumulated in the CCD (charge-coupled device) of the line sensor 17 while the XY stage 12 moves by the predetermined distance are output as image signals in synchronization with the imaging synchronization signal. Then, the XY stage 12 scans the entire imaging range in the Y direction, so that two-dimensional image data of the measured object can be obtained. At this time, since the imaging synchronization signal is output every time the XY stage 12 moves by a certain distance, the obtained image data is stored without displacement as a set of image data at predetermined intervals in the Y direction.

[0004]

FIG. 7 shows a timing chart of the image pickup synchronizing signal and the amount of electric charge accumulated in the CCD (electric charge imaging element) of the line sensor 17. This charge amount corresponds to the luminance value of the image data. FIG. 7 (a)
According to the above, each time the XY stage 12 moves a predetermined distance in the Y direction at a constant speed, an imaging synchronization signal is output. And
The electric charge gradually accumulated in the CCD of the line sensor 17 is
It is output in synchronization with the imaging synchronization signal, and is accumulated again until the next imaging synchronization signal is output.

As described above, in the above-described conventional image input device, the imaging synchronization signal is output from the linear encoder 13 every time the linear image pickup device moves by a predetermined distance.
Is determined by the moving speed of the XY stage 12. At this time, if the moving speed of the XY stage 12 is constant, the period T1 is constant, and the luminance value of the image data is also constant as shown in FIG. In this example, the measured object has a uniform luminance.

However, usually, the moving speed of the XY stage 12 slightly fluctuates due to the influence of its mechanical accuracy. Therefore, the cycle T1 of the imaging synchronization signal fluctuates, and as a result, the imaging time for each cycle fluctuates.
Accordingly, as shown in FIG. 7 (b), the luminance value of the image data, which should have been output at the predetermined reference period T2, also fluctuates due to the fluctuation of the charge accumulation time T1. There is a problem that accurate image data cannot be obtained.

On the other hand, as described above, the linear encoder 13
Instead of outputting an imaging synchronization signal every time the XY stage 12 detects movement of a predetermined distance, imaging may be performed by outputting an imaging synchronization signal at a fixed period. In this case, XY
Even if the moving speed of the stage 12 fluctuates, an image signal having a constant luminance value is always output because the imaging time is constant. However, when the moving speed fluctuates, the correspondence with the position coordinates on the image data becomes inaccurate, and the image may be distorted.

The line sensor 17 is connected to the XY stage 1
In the case of movement with respect to 2, the problem of speed fluctuation similarly arises. Therefore, the line sensor 17 and the XY stage 12
When the relative speed of the image fluctuates, the image data becomes unstable.

Therefore, an object of the present invention is to provide an XY stage 1
An image input device that has a constant luminance value and can obtain image data synchronized with the position even when the imaging synchronization signal fluctuates due to the relative speed of the line sensor 17 and the line sensor 17 fluctuating. To provide.

[0010]

According to a first aspect of the present invention, there is provided a line sensor having a one-dimensional photoelectric conversion element for imaging an object and outputting an image signal.
Driving means for moving the line sensor in a direction perpendicular to the scanning direction, position detecting means for detecting the position of the line sensor, acquiring the image signal from the line sensor at regular intervals, and converting the image signal to an image. Imaging control means for outputting data as data, and image processing means for obtaining the position of the image data based on the position of the line sensor at the time of outputting the image signal detected by the position detection means. Image input device.

According to a second aspect of the present invention, there is provided a line sensor having a one-dimensional photoelectric conversion element for picking up an image of an object and outputting an image signal; A stage to be moved, driving means for moving the stage in a direction perpendicular to the scanning direction of the line sensor, position detecting means for detecting the position of the stage, and acquiring the image signal from the line sensor at regular intervals. Imaging control means for outputting the image signal as image data, and image processing means for obtaining a position of the image data based on a position of the stage at the time of outputting the image signal detected by the position detection means. An image input device characterized in that:

In the image input device according to the present invention, the obtained image data are combined with reference to the coordinates of the position detected by the position detecting means, so that the entire object to be measured is free from distortion. Image data can be obtained.

[0013]

Embodiments of the present invention will be described below. However, the technical scope of the present invention is not limited to this embodiment.

FIG. 1 is a block diagram of an image input apparatus according to the first embodiment of the present invention. The image input device includes an image input unit 10 and a measurement control unit 20 that controls the image input unit 10. Further, the image input device has a personal computer 30. This personal computer 30
Is used for operation of the measurement control unit 20 and processing of image data sent from the measurement control unit 20. The personal computer 30 includes a printer 31 and a keyboard 3
2, mouse 33, monitor 34, etc. are connected.
An image processing board 35 for processing image data sent from the measurement control unit 20 is mounted.

The image input unit 10 is provided with an XY stage 12 which is placed on a base 11 and on which an object to be measured is placed. The XY stage 12 has, for example, a driving unit (not shown) therein, and can move in the X direction and the Y direction in FIG. 5 described above. Then, the linear encoder 13 serving as an imaging synchronization scale detects the movement of the XY stage 12 in the Y direction, and outputs an imaging synchronization signal B every time the XY stage 12 moves by a certain distance. Further, an imaging unit 15 is attached to a column 14 extending upward from the base 11.
The imaging unit 15 includes a line sensor 17 having a one-dimensional photoelectric conversion element whose scanning direction is the X direction, and an optical system 16 for forming an image of an object to be measured on an imaging surface of the one-dimensional photoelectric conversion element. I have. Then, the light from the light source 18 is transmitted to the optical fiber 1.
The light is guided to the image input unit 10 at 9 or the like, and the object is irradiated with light according to the type of the object to be measured such as a semiconductor wafer placed on the XY stage 12. That is, incident illumination is performed from above the object to be measured, or transmitted illumination is performed from below the object to be measured.

The measurement control unit 20 has a stage control unit 21 that outputs a stage control signal A to control the scan movement of the XY stage 12. X controlled by it
According to the movement of the Y stage 12, the linear encoder 13
Outputs an encoder signal B.

The encoder signal B is output each time the XY stage 12 moves a predetermined distance, and is input to the encoder coordinate detector 22. The encoder coordinate detector 22 can detect the moving distance of the XY stage 12 in the Y direction, that is, the encoder coordinates (the position of the XY stage 12) by sequentially counting the input encoder signal B.

Further, a clock signal D having a predetermined cycle is input from the clock signal generator 25 to the imaging start signal generator 24. Then, the imaging start signal generator 24 outputs an imaging start signal C every time a predetermined number of clock signals D are generated, for example.

The output imaging start signal C is input to the imaging control unit 23 and the coordinate storage unit 26. First, the imaging control unit 23 outputs an imaging control signal E based on the imaging start signal C, and controls the imaging of the line sensor 17. The line sensor 17 outputs an image signal F captured between the previous imaging control signal E and the current imaging control signal E to the imaging control unit 23 based on the imaging control signal E. Imaging control unit 23
A / D-converts the image signal F and outputs it to the personal computer 30 as an image data signal H. Therefore, the image data signal H is output at regular intervals, but does not correspond to the variation in the position due to the speed variation of the XY stage 12.

On the other hand, when the imaging start signal C is input to the coordinate storage section 26, the coordinate storage section 26 synchronizes with the imaging start signal C and reads the Y of the XY stage 12 counted by the encoder coordinate detection section 22. The direction coordinates (encoder coordinate signal B ′) are read and stored. Then, it outputs to the personal computer 30 as a coordinate data signal G.

Further, the measurement control section 20 is provided with a light source control section 27 for turning on / off the light source 18 and the like. Further, from the personal computer 30, various command signals I necessary for measurement such as setting of the moving speed of the XY stage 12 or start of measurement are sent to the measurement control unit 20.

In such an image input device, in the embodiment of the present invention, when the image signal E is output from the line sensor 17 based on the imaging start signal C output at a constant period, the coordinate storage unit 26 stores the position of the XY stage 12 in the Y direction, that is, the encoder coordinates from the encoder coordinate detection unit 22. Then, the image data signal H output from the imaging control unit 23 and the coordinate storage unit 26
Are input to the personal computer 30 in synchronization with each other.

Therefore, when the edge position is obtained by using the image data obtained by the image input device, each image data obtained from the image data signal H corresponds to the line coordinates positioned at a constant interval. With reference to the encoder coordinates to be calculated, it is obtained by an interpolation operation or the like. This method will be described below.

FIG. 2 is a diagram showing the correspondence between the line coordinates of the image data and the encoder coordinates. FIG. 2 shows the line coordinates on the horizontal axis and the encoder coordinates on the vertical axis. For example, the position information of the encoder coordinates included in the coordinate data signal G corresponding to the image data signal H on the ninth line is P9. Show. Similarly, positions corresponding to the image data signals H on the tenth, eleventh, and twelfth lines are P10, P11, and P12, respectively.

According to FIG. 2, at a line coordinate having a constant interval, for example, the moving speed of the XY stage 12 at the time of imaging the tenth line is faster than the moving speed of the XY stage 12 at the time of imaging the ninth line, and the XY stage 12 is kept constant. The distance between the encoder coordinates P10 and P11 is longer than the distance between the encoder coordinates P9 and P10 because the distance moves longer during the cycle. Further, the moving speed at the time of imaging the 11th line is 1
Since the moving speed is lower than the moving speed at the time of imaging the 0th line, the interval between the encoder coordinates P11 and P12 is shorter than the interval between the encoder coordinates P10 and P11.

On the other hand, the image data signal H is first subjected to image processing by the image processing board 35, and the position of the edge thereof is measured from the image data. Y of the image edge
Since the coordinates Q are line coordinates in the image data signal H, it is necessary to convert the line coordinates into encoder coordinates based on the coordinate data signal G when obtaining the actual position of the edge position. At this time, assuming that the image edge coordinates Q are obtained as, for example, 9.35, the conversion into the encoder coordinates based on the coordinate data signal G is performed, for example, as follows.
This can be performed by linear interpolation proportional to the distance between P9 and P10. That is, the coordinates Pn of the obtained image edge coordinates Q in the encoder coordinates can be obtained by the following equation. Pn = P9 + (P10−P9) × (9.35-9) In FIG. 2, the coordinates Pn are obtained by connecting the point L and the point M with a straight line, and the straight line and the Y coordinate (9.35) of the image edge coordinate Q. Corresponds to the encoder coordinates at the intersection N of.

As described above, even when the moving speed of the XY stage 12 fluctuates, the coordinates of the image data included in the image data signal H are converted into the encoder coordinates based on the encoder coordinates included in the coordinate data signal G. Accordingly, it is possible to obtain accurate image data synchronized with the position of the encoder coordinates.

FIG. 3A shows the line sensor 1.
FIG. 7 is a diagram illustrating an imaging range in each imaging of No. 7; The horizontal axis indicates the encoder coordinates, and the vertical axis indicates the charge amount. The width in the Y direction of the one-dimensional photoelectric conversion element (hereinafter, referred to as a CCD pixel) of the line sensor 17 is, for example, Δd, and the width of one line in encoder coordinates, that is, the imaging distance ΔL, which is the movement distance during one imaging, is also, for example. Assuming that Δd, imaging of one line by the line sensor 17 is performed by moving the XY stage 12 to ΔL, that is, Δ
This is performed during d movement. According to FIG. 3A, the imaging of the ninth line starts at the position of the CCD pixel of the line sensor 17 at the position of C1, and ends at the position of C2. The imaging of the tenth line is performed from the position C2 to the position C3. Accordingly, as shown in FIG. 3A, the imaging range that contributes to the image signal F output at one time is determined by setting the imaging distance ΔL to Δd
Then, it becomes 2Δd.

At this time, for example, the encoder coordinates stored in the coordinate storage unit 26 in synchronization with the image signal F obtained by imaging the ninth line are the width ΔL of the ninth line which is the position of the line sensor 17 at the start of scanning. This is the left end P9 of the image data. Similarly, coordinates corresponding to the tenth and eleventh image signals F are P10 and P11. However, FIG.
As shown in (a), in each image signal F, the position where the acquired charge amount, that is, the luminance value is the largest, is almost at the center of the imaging range, and the above-described image edge coordinates Q are at the center of the imaging range. Are the coordinates corresponding to the coordinates PT9.

Therefore, by converting the image edge coordinates Q (9.35) to the encoder coordinates based on the center coordinates PT9 of the imaging range, it becomes possible to obtain more accurate image data without measurement errors. For example, 9th line and 10th line
The central coordinate PT9 of the imaging range of the line is obtained by PT9 = (P9 + P10) / 2 PT10 = (P10 + P11) / 2. Therefore, for example, the conversion of the image edge coordinates Q (9.35) to the encoder coordinates is performed by linear interpolation proportional to the distance between PT9 and PT10 based on the center coordinates PT9 and P10 of the imaging range, as described above. Done. That is, the coordinates PTn of the obtained image edge coordinates in the encoder coordinates can be obtained by the following equation. PTn = PT9 + (PT10-PT9) × (9.35-
9) In FIG. 3B, this coordinate PTn is a point L in FIG.
And a point L 'and a point M' corresponding to the point M are connected by a straight line, and correspond to the encoder coordinates at the intersection N 'of the straight line and the Y coordinate (9.35) of the image edge coordinates Q. This makes it possible to obtain more accurate image data without measurement errors.

In FIG. 3A, the CCD pixels of the line sensor 17 are displayed as moving for convenience of the drawing, but the XY stage 12 actually moves with respect to the line sensor 17. . In the embodiment of the present invention, since the line sensor 17 and the XY stage 12 only need to move relatively, the movement of the line sensor 17 with respect to the XY stage 12 and the movement of the XY stage 12 with respect to the line sensor 17 are substantially the same. Has the effect of

FIG. 4 is a block diagram of an image input apparatus according to a second embodiment of the present invention. In the present embodiment, a fixed stage 12 ′ is provided instead of the XY stage 12, and the line sensor 17 is moved in the Y direction instead of the movement of the XY stage 12.
Specifically, a driving unit 40 for driving a line sensor 17 described later in the Y direction is provided. Each time the line sensor 17 moves by a predetermined distance, the linear encoder 43
Is output. The driving unit 40 receives a line sensor control signal J from the line sensor control unit 28 in the measurement control unit 20.
Is controlled by

Then, as in the first embodiment, the same conversion processing as described above is performed on the basis of the output image data signal H and coordinate data signal G, so as to correspond to the position of the linear encoder 13. Image data can be obtained. Further, since the line sensor 17 is lighter in weight than the XY stage 12, its movement control is relatively easy. Therefore, the speed fluctuation is suppressed lower, and it is possible to perform more accurate movement control. However, even if the speed fluctuates, accurate image data can be obtained based on the image data signal H and the coordinate data signal G according to the present embodiment.

FIG. 5 is a schematic diagram showing a driving unit 40 for moving the line sensor 17 according to the present embodiment. FIG. 5 (a) is a top view thereof, and FIG. )
3 is a sectional view taken along line AA ′ of FIG.

According to FIG. 5A, the line sensor 17 extending in the X direction moves along the scan guide 41 extending in the Y direction. A linear encoder 43 is arranged along the scan guide 41, and the position of the line sensor 17 is read by an encoder head 42 provided integrally with the line sensor 17. The line sensor 17 is driven by, for example, an ultrasonic motor 44.

As described above, in the embodiment of the present invention, when either the line sensor 17 or the object to be measured is moved to capture an image of the object to be measured, the relative movement speed varies. Even in such a case, by performing image processing of the image data signal based on the encoder coordinates stored in synchronization with the image signal output each time, accurate image data without unevenness in imaging can be obtained.

In the image input device according to the present embodiment, as shown in FIG. 1, when the XY stage 12 moves and the line sensor 17 is fixed, the optical system 16 is integrated with the line sensor 17. In other words, as shown in FIG. 4, the XY stage 12 is fixed and the line sensor 17 is fixed.
Move, the optical system 16 is connected to the line sensor 1.
The optical system 16 is integrated with the XY stage 12 when the XY stage 12 moves and the line sensor 17 is fixed, in addition to the second configuration that is integrated with the XY stage 12, that is, moves together with the line sensor 17. That is, X
A third configuration (not shown) that moves together with the Y stage 12, and the XY stage 12 is fixed, and when the line sensor 17 moves, the optical system 16 is integrated with the XY stage 12, ie, the XY stage. This can be realized in four configurations of a fourth configuration (not shown) fixed together with the configuration 12.

The stage 12 in the first configuration
May be a rotary drum type stage whose center of rotation is an axis parallel to the scanning direction of the line sensor 17.

[0039]

As described above, according to the present invention,
In an image input device that captures an image of an object to be measured by moving a line sensor or an XY stage, even if the movement speed fluctuates, the image is stored in synchronization with the output of a captured image signal. Based on the encoder coordinates, it is possible to obtain accurate image data having no displacement and having a constant luminance value.

Further, by moving the line sensor instead of the XY stage, the moving speed can be controlled more accurately, so that the speed fluctuation can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image input device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a coordinate conversion process of image data.

3A is a diagram illustrating an imaging range in each time of imaging by a line sensor 17, and FIG. 3B is a diagram illustrating a coordinate conversion process based on center coordinates of the imaging range. It is.

FIG. 4 is a block diagram of an image input device according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram showing a driving unit 40.

FIG. 6 is a diagram showing the principle of a conventional image input device.

FIG. 7 is a timing chart of a conventional imaging synchronization signal and a luminance value of image data.

[Explanation of symbols]

 Reference Signs List 12 XY stage 13 Linear encoder 17 Line sensor 22 Encoder coordinate detection unit 23 Imaging control unit 24 Imaging start signal generation unit 25 Clock signal generation unit 26 Coordinate storage unit 40 Drive unit 43 Linear encoder

Claims (2)

[Claims] 1. A line sensor having a one-dimensional photoelectric conversion element for capturing an image of an object and outputting an image signal, driving means for moving the line sensor in a direction perpendicular to a scanning direction thereof, Position detecting means for detecting a position, image capturing control means for acquiring the image signal from the line sensor at a constant period, and outputting the image signal as image data, and outputting the image signal detected by the position detecting means. Image processing means for obtaining the position of the image data based on the position of the line sensor. 2. A line sensor having a one-dimensional photoelectric conversion element for imaging an object and outputting an image signal, a stage on which the object is mounted, and a stage perpendicular to a scanning direction of the line sensor. Driving means for moving the stage in any direction, position detecting means for detecting the position of the stage, image capturing control means for acquiring the image signal from the line sensor at a constant cycle, and outputting the image signal as image data, An image input device, comprising: image processing means for obtaining the position of the image data based on the position of the stage at the time of outputting the image signal detected by the position detection means.