JPH05107038A - Image sensing apparatus - Google Patents

Abstract

PURPOSE:To obtain picked-up image data having the stabilized luminance value by correcting the fluctuation in luminance of the picked-up image data caused by the fluctuation of a moving speed in an image sensing apparatus wherein the image of an object is picked up with a line sensor with the object being moved at a constant speed and the two-dimensional image is recorded. CONSTITUTION:A linear encoder 7 generates pulses at every constant distance interval of an XY stage 5. Thus, an image-sensing synchronizing signal (b) is obtained. The luminance value of the image data (d), which are picked up in synchronization with the image-sensing synchronizing signal (b), is fluctuated with the speed fluctuation of the XY stage 5. Then, the period time of the image-sensing synchronizing signal (b) is measured with a period measuring part 8. The luminance value equivalent to the difference between the measured period time and the reference period time is corrected with a luminance correcting part 9. Thus, the corrected image data (g) having the stabilized luminance value are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus, and more particularly to an image pickup apparatus which can be applied to a picked-up image input of an apparatus for automatically inspecting a defective appearance of a semiconductor wafer, a printed circuit board or the like by an image processing method.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a conventional image pickup apparatus. The image pickup apparatus shown in FIG. 2 is an optical lens 2 for enlarging and imaging a chip surface of a semiconductor wafer 1 as an object.
And the line sensor 3 which captures the enlarged image and outputs the video signal a, and the imaging timing of the line sensor 3 which receives the imaging synchronization signal b is controlled by the imaging control signal c, and the video signal a is A / D. An image pickup control section 4 for converting and outputting an image data signal d, and an XY stage 5 on which the semiconductor wafer 1 is placed and which moves in the scanning direction (X direction) of the line sensor 3 and in a direction (Y direction) perpendicular thereto. Then, the stage control signal e controls the step movement of the XY stage 5 in the X direction by a constant distance, and the stage control unit 6 performs the constant speed feed control in the Y direction and the movement distance of the XY stage 5 in the Y direction. A linear encoder 7 as an imaging synchronization scale for detecting and outputting a imaging synchronization signal b by generating a pulse at constant distance intervals, and an image memory 10 for recording an image data signal d. Having.

First, while the semiconductor wafer 1 is controlled and moved in the Y direction by the XY stage 5, the line sensor 3 scans and images in the X direction. Further, the image pickup control unit 4 matches the image pickup timing of the line sensor 3 with the image pickup synchronization signal b from the linear encoder 7, and the video signal a is A / D.
The image data signal d is converted and output. Here, the resolution of the linear encoder 7 is matched with the optical resolution,
By sequentially recording the image data signal d in the image memory 10, the two-dimensional image of the target chip can be recorded without displacement.

When this conventional image pickup apparatus is applied to the automatic defect inspection by the image processing method, the image processing is performed on the image recorded by the above operation.

When the entire surface of the semiconductor wafer 1 is imaged, the semiconductor wafer 1 is step-moved in the X-direction by the XY stage 5 after the above-described operation is completed, the above-mentioned operation is performed again, and this operation is repeated. Image the entire surface.

[0006]

In the conventional image pickup apparatus described above, the image data picked up by the line sensor is directly recorded in the image memory in synchronization with the image pickup synchronizing signal from the linear encoder. Here, the cycle time of the imaging synchronization signal is X
Although it is determined by the speed of the Y stage, the speed of the XY stage always changes due to the influence of the drift of the stage control unit and the accuracy of the XY stage mechanism unit. Therefore, the cycle time of the imaging synchronization signal also fluctuates, and the fluctuation of this cycle time fluctuates the light receiving time of the line sensor for each imaging cycle. Therefore, the brightness value of the image data also fluctuates and a stable captured image is obtained. There was a drawback that I could not get.

[0007]

An image pickup apparatus of the present invention includes a line sensor for picking up an image of an object formed by an optical lens and outputting a video signal, and a line sensor for mounting the object. Y, which is a direction perpendicular to the X direction, which is the scanning direction of
A stage that moves in the Y direction, a stage controller that performs constant-speed feed control of the stage in the Y direction, and a Y of the stage.
Image synchronizing signal that outputs an image capturing synchronizing signal at fixed intervals of movement in the direction, the image capturing timing of the line sensor is synchronized with the image capturing synchronizing signal, and the video signal is A / D converted to obtain an image data signal. , A cycle measuring section that measures the cycle time of the imaging synchronization signal for each cycle, and a reference cycle calculated from the cycle time measured by the cycle measuring section and the Y-direction movement set speed. A brightness correction unit that compares the time and corrects the brightness value of the image data signal by a value corresponding to the difference.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The image pickup apparatus shown in FIG. 1 includes an optical lens 2 for enlarging and forming an image on a chip surface of a semiconductor wafer 1 as an object, and a line sensor 3 for picking up the enlarged image and outputting a video signal a.
And the line center 3 in response to the imaging synchronization signal b from the outside.
The image pickup control section 4 which controls the image pickup timing of the image signal a by the image pickup control signal c, outputs the image data signal d by A / D converting the image signal a, and the semiconductor wafer 1 are placed, and the scanning direction of the line sensor 3 The XY stage 5 moving in the (X direction) and the direction (Y direction) perpendicular thereto, and the XY stage 5 are subjected to step movement control of a constant distance in the X direction by the stage control signal e, and in the Y direction. A stage controller 6 that performs constant-speed feed control, and a linear function as an imaging synchronization scale that detects the moving distance of the XY stage 5 in the Y direction and outputs a imaging synchronization signal b by generating a pulse at constant distance intervals. The encoder 7, the cycle measuring unit 8 that measures the cycle time of the imaging synchronization signal b for each cycle, and outputs the measured value as the cycle time data signal f, the cycle time data signal f, and the Y direction moving device. Comparing the reference period time which is calculated from the velocity, the image data signal d by a value corresponding to the difference
It has a brightness correction section 9 for correcting the brightness value of 1 to output a corrected image data signal g, and an image memory 10 for sequentially recording the corrected image data signal g.

First, while the semiconductor wafer 1 is moved by the XY stage 5 at a constant Y speed, the line sensor 3 scans and images in the X direction. Further, the image pickup control unit 4 matches the image pickup timing of the line sensor 3 with the image pickup synchronizing signal b from the linear encoder 7, and A / D-converts the video signal a to output the image data signal d. Linear encoder 7
Generates a pulse at every constant distance of the movement of the XY stage in the Y direction, and therefore the cycle time of the imaging synchronization signal d is determined by the moving speed of the XY stage in the Y direction. Here, the Y-direction moving speed of the XY stage is controlled to be constant by the stage control unit 4, but always changes due to the influence of the drift of the stage control unit 4, the accuracy of the mechanical unit of the XY stage 5, and the like. Therefore, the synchronization time of the imaging synchronization signal b also changes,
Since the light reception time of the line sensor 3 for each image pickup cycle changes due to the change of the cycle time, the brightness value of the image data signal d also changes.

Then, next, the cycle measuring section 8 measures the cycle time of the imaging cycle signal b, and the brightness correcting section 9 obtains the cycle time data signal f with the reference cycle time calculated from the Y-direction movement set speed. The brightness values of the image data signal d are compared and corrected, and the corrected image data signal g is output. As a result, the corrected image data signal g becomes image data having a stable luminance value. Here, the resolution of the linear encoder 7 is made to match the optical resolution,
By recording the corrected image data signal g in the image memory 10, the two-dimensional image of the target chip can be stably recorded in both position and brightness.

When this embodiment is applied to the automatic defect inspection by the image processing method, the image processing is performed on the image recorded by the above operation.

When the entire surface of the semiconductor wafer 1 is imaged, after the imaging by the above operation is completed, the semiconductor wafer 1 is stepwise moved in the X direction by the XY stage 5, the above operation is performed again, and this operation is repeated. Image the entire surface.

[0014]

The image pickup apparatus of the present invention measures the cycle time of the image pickup synchronizing signal of the image data picked up in synchronization with the image pickup synchronizing signal from the image pickup synchronizing scale, and calculates from the constant speed movement set speed of the stage. Since the brightness value is corrected by a value corresponding to the difference compared with the reference time of the imaging cycle, it is possible to obtain image data having a stable brightness value even if the stage speed changes. is there.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional imaging device.

[Explanation of symbols]

 1 semiconductor wafer 2 optical lens 3 line sensor 4 imaging control unit 5 XY stage 6 stage control unit 7 linear encoder 8 cycle measuring unit 9 brightness correction unit 10 image memory a video signal b imaging synchronization signal c imaging control signal d image data signal e Stage control signal f Period time data signal g Corrected image data signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H04N 5/235 9187-5C 7/18 B 8626-5C // H01L 21/66 A 8406-4M

Claims (1)

[Claims] 1. A line sensor for picking up an image of an object formed by an optical lens and outputting a video signal, and a direction perpendicular to an X direction which is a scanning direction of the line sensor on which the object is placed. A stage that moves in the Y direction, and a stage control unit that performs constant-speed feed control of the stage in the Y direction.
An imaging synchronization scale that outputs an imaging synchronization signal at constant intervals of movement of the stage in the Y direction, and an imaging timing of the line sensor in synchronization with the imaging synchronization signal,
Further, an image pickup control unit for A / D converting the video signal and outputting an image data signal, and a cycle time of the image pickup synchronizing signal is 1
A cycle measuring unit that measures each cycle is compared with a cycle time measured by the cycle measuring unit and a reference cycle time calculated from the Y-direction movement set speed, and a value corresponding to the difference between the cycle time of the image data signal An image pickup apparatus comprising: a brightness correction unit that corrects a brightness value.