JPH10275221A - Image input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable image data by correcting the luminance value of image data based on the ratio of the period of an image pickup synchronizing signal and a previously set period to output image data of a fixed luminance value even when the image pickup synchronizing signal is fluctuated. SOLUTION: When an image data signal E is inputted from an image pickup control part 23, its luminance value is corrected. In this case the period of the image pickup synchronizing signal B measured by a period measuring part 22 and a fixed reference signal previously set from a reference signal generation part 24 are inputted to a luminance correcting part 25 to correct the luminance value of image data based on the ratio of them. Namely the part 25 calculates the ratio R=T2/T1 of the period T1 of the measured image pickup synchronizing signal and a reference period T2 from two inputted periods. Image data obtained by T2/T1-folding the luminance value of image data at the signal E of inputted image data is outputted as a corrected image data signal H.

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. 5 is a diagram showing the principle of a conventional image input device. According to FIG. 5, 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 mounted on the XY stage 12,
The image of the object to be measured is transmitted to the line sensor 1 via the objective lens 2.
7, and the formed image is captured by the line sensor 17. The XY stage 12 moves along a guide 3 that guides the XY stage in the Y direction. An image signal of an image captured by the line sensor 2 is generated by the linear encoder 13 every time the XY stage 12 moves a certain distance in the Y direction. The image data is output as image data in synchronization with the imaging synchronization signal, and is stored in storage means (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 amount of charge accumulated in the CCD (charge-coupled device) of the line sensor 17 while the XY stage 12 moves by the predetermined distance is output as an image signal in synchronization with the imaging synchronization signal. Then, each time the XY stage 12 moves by a certain distance, this image signal is output, and by scanning the entire imaging range, image data of the device under test can be obtained. At this time, the imaging synchronization signal is transmitted to the XY stage 1
Since the image data is output for every two fixed distance movements, the obtained image data is stored without displacement as a set of image data at predetermined intervals in the Y direction.

[0004]

FIG. 6 shows a timing chart of the image pickup synchronizing signal and the amount of electric charge stored in the CCD (charge imaging device) of the line sensor 17. This charge amount corresponds to the luminance value of the image data. FIG. 6 (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 charge gradually accumulated in the CCD of the line sensor 17 is
The charge is output in synchronization with the imaging synchronization signal, and the electric charge is accumulated 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 is constant, and the luminance value of the image data is also constant as shown in FIG.

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.
Therefore, as shown in FIG. 6 (b), the charge accumulation time T1 of the image data of the luminance value originally output at the predetermined reference period T2 fluctuates.
There is a problem that the luminance value of the output image data also fluctuates and stable image data cannot be obtained.

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.

Accordingly, an object of the present invention is to provide an XY stage 1
Provided is an image input device that can output image data with a constant luminance value and obtain stable image data even when the imaging synchronization signal fluctuates due to the relative speed of the line sensor 17 and the line sensor 17 fluctuating. That is.

[0009]

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 thereof; movement detecting means for detecting a predetermined constant distance movement of the line sensor and outputting an imaging synchronization signal for each constant distance movement; Image data output means for outputting as image data in synchronization with the imaging synchronization signal, cycle measurement means for measuring a first cycle T1, which is a cycle of the imaging synchronization signal, and And a correcting means for correcting a luminance value of the image data based on a ratio to a second cycle T2 which is a cycle of the image input apparatus.

According to a second 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; A stage to be placed, and driving means for moving the stage in a direction perpendicular to the scanning direction of the line sensor,
Movement detection means for detecting movement of the stage at a predetermined constant distance and outputting an imaging synchronization signal for each movement of the predetermined distance; and image data output means for outputting the image signal as image data in synchronization with the imaging synchronization signal And a cycle measuring means for measuring a first cycle T1 which is a cycle of the imaging synchronization signal; and the image data based on a ratio of the first cycle to a second cycle T2 which is a preset cycle. And a correction means for correcting the luminance value of the image.

Preferably, the correction by the correction means is performed by multiplying the luminance value of the image data by T2 / T1. As a result, the luminance value of the image data can be made constant, and stable image data can be obtained.

[0012]

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 a 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 which is used for operating the measurement control unit 20 and processing image data sent from the measurement control unit 20. The personal computer 30 is connected with a printer 31, a keyboard 32, a mouse 33, a monitor 34, and the like, and further has an image processing board 35 for processing image data sent from the measurement control unit 20.

The image input unit 10 first includes an XY stage 12 on a base 11 on which an object to be measured is placed.
Is provided. 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 including a one-dimensional photoelectric conversion element whose scanning direction is the X direction, and an optical system 1 that forms an image of an object to be measured on an imaging surface of the one-dimensional photoelectric conversion element.
6 and. Then, the light from the light source 18 is guided to the image input unit 10 by an optical fiber 19 or the like, and the light is radiated to the measured object according to the type of the measured object such as a semiconductor wafer mounted 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 scanning movement of the XY stage 12, and controls the XY
Each time the stage 12 moves a predetermined distance, the linear encoder 13 outputs an imaging synchronization signal B. Then, the cycle of the imaging synchronization signal B according to the moving speed is measured by the cycle measuring unit 22. Further, the imaging control unit 23 outputs an imaging control signal C to control the imaging of the line sensor 17 and outputs an image signal D from the line sensor 17 as an image data signal E in synchronization with the imaging synchronization signal B. . Further, a brightness correction unit 25 for correcting the image data signal E is provided. The brightness correction unit 25 includes a reference cycle generation unit 24 for generating a reference cycle obtained from a predetermined moving speed of the XY stage 12. , And the measurement period signal G output from the period measurement unit 22. The brightness correction unit 25 will be described later in detail. Further, the measurement control unit 20 is provided with a light source control unit 27 that performs ON / OFF of the light source 18 and the like.

The corrected image data signal H corrected by the brightness correction unit 25 is input to the personal computer 30 and displayed on the monitor 34. 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, the object to be measured is imaged by the line sensor 17 whose scanning direction is the X direction while moving at a constant speed in the Y direction along with the movement of the XY stage 12. The image signal D is input to the imaging control unit 23. Then, the imaging control unit 23 performs A / D conversion on the image signal D and outputs it as an image data signal E in accordance with the imaging synchronization signal B. At this time, as described above, the period of the imaging synchronization signal B changes due to the change in the moving speed of the XY stage 12, and thereby the brightness value of the image data signal E changes.

Therefore, in the present embodiment, in the brightness correction section 25, the image data signal E
Is input, the luminance value is corrected as follows. That is, the period of the imaging synchronization signal measured by the period measuring unit 22 and a predetermined reference period preset from the reference period signal generating unit 24 are input to the luminance correction unit 25, and based on the ratio therebetween. Thus, the luminance value of the image data is corrected.

More specifically, the luminance correction unit 25 calculates the period T1 of the measured imaging synchronization signal from the two input periods.
A ratio R = T2 / T1 between the reference period T2 and the reference period T2 is calculated. Then, image data obtained by multiplying the luminance value of the image data in the input image data signal E by T2 / T1 is output as the corrected image data signal H.

FIG. 2 shows the relationship between the period of the imaging synchronization signal B and the luminance values of the image data before and after the correction. As shown in FIG. 2, the moving speed of the XY stage 12 is lower than the set speed,
If the period T1 of the imaging synchronization signal is longer than the reference period T2 (period T1a in the figure), the luminance value Q1 of the image data
Is larger than the brightness value Q3 when the imaging synchronization signal T1 is equal to the reference cycle T2, but the brightness correction unit 25 performs a correction to multiply Q1 by T2 / T1a to obtain the brightness value in the reference cycle T2. It is corrected to Q3. Also, the moving speed of the XY stage 12 is faster than the set speed,
If the period T1 of the imaging synchronization signal is shorter than the reference period T2 (period T1b in the figure), the luminance value Q2 of the image data
Is smaller than the brightness value Q3 in the reference cycle T2, but the brightness correction unit 25 sets Q2 to T2 / T1b.
By performing the multiplication correction, the luminance value is corrected to the luminance value Q3 in the reference cycle T2. FIG. 2 is based on the assumption that the DUT has the same luminance.

As described above, when the moving speed of the XY stage 12 fluctuates and the period of the imaging synchronization signal B fluctuates, the luminance value of the image data at that time is converted into a luminance value in the reference period T2. Thus, it is possible to obtain stable image data having a constant luminance value. That is, as shown in FIG. 2, when the period T1 of the imaging synchronization signal B is different from the reference period T2, the image data at that time is multiplied by the ratio R to correct the image data of the luminance value in the reference period T2. can do.

When the period T1 of the imaging synchronization signal B is the same as the reference period T2 (period T1c in the figure),
In the brightness correction unit 25, the input image data is multiplied by the same size (T2 / T1c = 1), so that the brightness value Q3 does not change.

FIG. 3 is a block diagram of an image input device 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 drive unit 40 for driving a line sensor 17 described later in the Y direction is provided, and the linear encoder 43 outputs the imaging synchronization signal B every time the line sensor 17 moves a predetermined distance. The driving section 40 is controlled by a line sensor control signal J from a line sensor control section 26 in the measurement control section 20. Then, similarly to the first embodiment, the same correction as described above is performed on the image data signal E based on the ratio between the measured period T1 of the imaging synchronization signal B and the above-described reference period T2. Can be made constant. 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, in this embodiment, the luminance is corrected to a constant value by the luminance correction unit 25 even if the speed varies.

FIGS. 4A and 4B are schematic views showing a driving unit 40 for moving the line sensor 17 in the present embodiment, wherein FIG. 4A is a top view thereof, and FIG. )
3 is a sectional view taken along line AA ′ of FIG.

According to FIG. 4A, 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, by moving one of the line sensor 17 and the object to be measured, an image of the object to be measured is taken, and when the moving speed varies. Is used to correct the image data of the imaged image based on the ratio between the period T1 of the imaging synchronization signal and a preset reference period T2.

In the image input device of 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, the XY stage 12 is fixed, and the line sensor 17 is fixed as shown in FIG.
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 XY stage 1 in the first configuration
Reference numeral 2 may be a rotary drum type stage that rotates about an axis parallel to the scanning direction of the line sensor 17 as a rotation center.

[0029]

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, the luminance value of image data of the captured image is kept constant even when the moving speed fluctuates. be able to.

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 relationship between a cycle of an imaging synchronization signal B and luminance values of image data before and after correction.

FIG. 3 is a block diagram of an image input device according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing a driving unit of the line sensor 17;

FIG. 5 is a diagram illustrating the principle of a conventional image input device.

FIG. 6 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 Period measurement unit 23 Imaging control unit 24 Reference period generation unit 25 Brightness correction unit 40 Drive unit 43 Linear encoder

Claims (3)

[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, Movement detection means for detecting movement of a predetermined fixed distance and outputting an imaging synchronization signal for each movement of the fixed distance; image data output means for outputting the image signal as image data in synchronization with the imaging synchronization signal; Cycle measuring means for measuring a first cycle T1 which is a cycle of an imaging synchronization signal; and a brightness value of the image data based on a ratio of the first cycle to a second cycle T2 which is a preset cycle. An image input device, comprising: a correction unit that corrects an image. 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 a predetermined direction, movement detecting means for detecting a predetermined constant distance movement of the stage, and outputting an imaging synchronization signal for each constant distance movement, and synchronizing the image signal with the imaging synchronization signal. Image data output means for outputting as image data; cycle measurement means for measuring a first cycle T1 which is a cycle of the imaging synchronization signal; second cycle T2 which is a preset cycle and a preset cycle And a correcting means for correcting the luminance value of the image data based on the ratio of the image data. 3. The image processing apparatus according to claim 1, wherein the correction unit sets the luminance value of the image data to T2 / T1.
An image input device characterized by multiplying.