JP2003161875A - Method and device for automatic focusing by image processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the time required for automatic focusing and to stabilize the retrieval time. <P>SOLUTION: The automatic focusing device is provided with an axis controller, an ITV camera 4, and an image processor which has FIFO memories 22a and 22b which receive the image data and a processor 19 and uses a constitution in which the axis controller changes position of the ITV camera 4 in Z-axis direction. The axis controller changes the relative distance between an object and the ITV camera 4 in the Z-axis direction. The axis controller detects a pre-determined measurement start point and transmits a measurement position arrival signal to an image processor. The image processor, after receiving the measurement position arrival signal, takes in the image data from the ITV camera 4 into the FIFO memories 22a and 22b. Focusing degree for each taking in is calculated by a processor 19. A peak point of the focusing degree is retrieved and the position of the peak point is sent to the axis controller. The ITV camera 4 is controlled to move so as to agree with the position of the peak point. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses image data obtained from an image signal of an image pickup device such as a television camera to realize a high-speed autofocus function when positioning an object to be measured in a minute dimension measuring device or the like. The present invention relates to an autofocus method and apparatus by enabling image processing.

[0002]

2. Description of the Related Art When an object to be measured is imaged by an image pickup apparatus and an image processing apparatus for processing the image signal is used to position the object to be measured, the height direction of the object to be measured with respect to the image pickup apparatus,
That is, in order to prevent the focus from being blurred due to the variation in the Z-axis direction and lowering the positioning accuracy, the imaging device is focused on the object to be measured by the autofocus function.

FIG. 4 shows an example of a mechanism of a positioning device with an autofocus function. Reference numeral 1 is a base on which an XY axis stage 2 is installed, and a Z axis stage 3 is installed vertically to the base 1. IT by Z-axis stage 3
The V camera 4 is mounted so as to be vertically movable in the Z-axis direction (vertical direction). 5 is an object to be measured, and the XY axis stage 2
It is placed and fixed on the upper surface and is movable by the XY axis stage 2 in the X-axis direction in the horizontal plane and in the Y-axis direction orthogonal thereto (the X-axis, the Y-axis and the Z-axis are three orthogonal axes). Form). 6 is a monitor, 7 is an image processing device, and 8 is an XYZ axis control device. The image processing device 7 uses the ITV camera 4 and the XYZ axis control device 8 via an interface.
It is connected to the. The monitor 6 displays the image processing result and the like.

FIG. 5 shows the structure of a conventional image processing apparatus.
FIG. 6 is a time chart showing a conventional autofocus operation when the image processing apparatus of FIG. 5 is used. The conventional autofocus operation is performed by the ITV camera 4 as an image pickup device, which is an object to be measured 5 mounted on the XY axis stage 2 in FIG.
After completing the movement of the XY axis stage 2, the image processing apparatus 7 outputs a Z axis movement command signal 13 to the first measurement position to the XYZ axis control apparatus 8, and the XYZ axis control apparatus 8 In accordance with the command, the Z-axis stage 3 is moved to the command position as shown by the Z-axis moving speed curve 9 in FIG. The XYZ-axis control device 8 outputs the Z-axis movement completion signal 10 to the image processing device 7 after the Z-axis stage 3 reaches the commanded position and the set ring is settled.

When the image processing device 7 receives the Z-axis movement completion signal 10, the image signal (analog signal) 16 from the ITV camera 4 is converted into an A / D converter 17 as shown in FIG.
After being converted to a digital signal by, the image memory 18 is written. During this time, the image capture signal 11 from the capture control circuit 20 becomes active, and after the writing in the image memory 18 is completed, the image processing execution signal 12 is activated and the processor 19 reads the image data signal 21 from the image memory 18 to determine the focus degree. Is calculated. The image processing execution signal 12 is a signal output from the processor 19 to the XYZ axis control device 8, and informs the XYZ axis control device 8 that the processor 19 is executing processing (busy) in the active state. .

Based on the result obtained by the processor 19, the next Z-axis movement command signal 13 is sent from the image processing device 7 to the axis control device 8 again, as shown in the Z-axis movement speed curve 9 in FIG. Then, the Z-axis stage 3 is moved to the command position. By repeatedly executing such an operation, a point at which the degree of focus equal to or higher than the specified value is obtained is searched. When a focusing degree equal to or higher than a prescribed value is obtained, it is common to measure the positioning dimension at that position by a method such as pattern matching.

However, in this method, as can be seen from the Z-axis movement speed curve 9 in FIG. 6, the Z-axis stage 3 is moved and the XYZ-axis control is performed from the image processing device 7 in each cycle for obtaining the focus value for one screen. Since the communication time of the Z-axis movement command signal 13 to the device 8 is long, one cycle becomes long. In addition, depending on the search algorithm, the number of searches to obtain the specified degree of focus varies greatly, and the search time is lengthened especially when measuring defective products that do not achieve the specified degree of focus. Is a problem.

[0008]

As described above, in the autofocus operation of the conventional apparatus, it takes a long time to obtain the prescribed focus degree, and depending on the object to be measured, the prescribed focus degree is obtained. There was a big time variation and it was difficult to operate.

As a publicly known document proposing a device having an autofocus function, Japanese Patent Laid-Open No. 6-229894.
Although there is an official gazette, the details of the autofocus function are not mentioned.

The present invention is intended to eliminate the above-mentioned drawbacks of the prior art, and provides an autofocus method and apparatus by image processing which can shorten the time required for the autofocus operation and stabilize the search time. The purpose is to do.

Other objects and novel features of the present invention will be clarified in the embodiments described later.

[0012]

In order to achieve the above object, an autofocus method by image processing according to the present invention includes an axis control device, an image pickup device, and an image processing device which receives image data from the image pickup device. And a configuration for changing at least the position of the imaging device or the object to be measured in the Z-axis direction by the axis control device, and the axis control device in the Z-axis direction between the object to be measured and the imaging device. The relative distance is continuously changed to detect a predetermined measurement start point by the axis control device, a measurement position arrival signal is sent to the image processing device, and after the measurement position arrival signal is received, The image processing device continuously or intermittently captures image data including the object to be measured from the imaging device, calculates a focus degree for each capture, and searches for a peak point of the focus degree, The position of the peak point is the axis To the control device, and the axis control device moves the imaging device or the object to be measured in the Z-axis direction so as to match the position of the peak point, and combines the object to be measured with the imaging device. It is characterized by setting it at the focal position.

An autofocus device for image processing according to the present invention comprises an axis control device, an image pickup device, and an image processing device for receiving image data from the image pickup device, wherein the axis control device is the image pickup device or the object. At least Z
The image processing apparatus includes a storage unit that takes in image data from the image pickup apparatus and a processor, and the axis control unit controls the object to be measured and the image pickup apparatus. The relative distance in the Z-axis direction between them is continuously changed, and a predetermined measurement start point is detected by the axis control device, and a measurement position arrival signal is sent to the image processing device. Receiving the image processing device, the image data including the object to be measured from the imaging device is continuously or intermittently taken into the storage means, and the focus degree for each taking-in is calculated by the processor, The processor retrieves the peak point of the focus degree, and the processor sends the position of the peak point to the axis control device, and the axis control device selects the image pickup device or the object to match the position of the peak point. Move the measurement object in the Z-axis direction Te, is characterized in that the focus position of the object to be measured with respect to the imaging device.

In the autofocus device based on the image processing, the processor has a region designation function of designating and capturing a partial region of the image data from the image pickup device, and reduced by designating the region. The image data including the object to be measured is temporarily stored in the storage means, and the storage means has a FIFO memory so that it is not overwritten successively when the image data is taken in, and the writing capacity exceeds the capacity of the FIFO memory. It is preferable that the processor reads and processes the data before it is overwritten.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an autofocus method and apparatus by image processing according to the present invention will be described below with reference to the drawings.

Embodiments of an autofocus method and apparatus by image processing according to the present invention will be described with reference to FIGS. 1 to 4. 1 is a block configuration diagram of an image processing apparatus used in the present embodiment, FIG. 2 is a timing chart showing an autofocus operation, FIG. 3 is an explanatory diagram of area designation and capture in the autofocus operation, and FIG. 4 is an autofocus function. FIG. 5 is a perspective view showing an example of a mechanism of the positioning device with an attached device (the mechanical structure of FIG. 4 is as described in the description of the prior art).

In the present embodiment, the XYZ-axis controller 2 controls the XY-axis stage 2 so that the DUT 5 placed on the XY-axis stage 2 in FIG. Then, considering the height variation of the DUT 5 at the same time, the upper limit of the allowable range of the Z-axis stage position for focusing on the DUT 5 is set at the acceleration time of the Z-axis stage 3 in FIG. The Z-axis stage 3 is controlled and moved by the XYZ-axis control device 8 to a movement start point (predetermined position) determined in consideration of the movement distance and time.

The XYZ-axis control device 8 lowers the Z-axis stage 3 from the movement start point before the in-focus position, detects the position of the upper limit of the allowable range, and then measures the measurement position with respect to the image processing device 7. The arrival signal 14 is output. The moving speed of the Z-axis stage 3 at this time is represented by moving speed × capturing interval = detecting interval <required resolution (1), and is set so as to satisfy the above formula (1). Here, the required resolution indicates the range in which the prescribed degree of focusing in the Z-axis stage 3 is obtained. As can be seen from the Z-axis movement speed curve 9 in FIG. 2, the Z-axis stage 3 moves at a constant speed except during acceleration and deceleration. The capture interval is a time interval, and the detection interval is a length interval.

The image processing device 7 is connected to the ITV camera 4 and the XYZ axis control device 8 via an interface, and has the configuration of FIG. 1 in the present embodiment. Upon receiving the measurement position arrival signal 14 from the XYZ axis control device 8, the image processing device 7 waits for a vertical synchronizing signal that comes at the beginning of one frame of the image signal from the ITV camera 4 and starts capturing.

In the present embodiment, the image processing device 7 is configured as shown in the block diagram of FIG. 1, and the A / D converter 17 for converting the image signal (analog signal) of the ITV camera 4 into a digital signal and its digital signal. Asynchronous FIFO (first in first
Out) Memory A 22a and asynchronous FIFO memory B
22b, a processor 1 for reading out image data signals A21a, B21b from the FIFO memories A22a, B22b
9 and the fetch control circuit 20 for outputting the fetch signals A11a and B11b to the FIFO memories A22a and B22b.

In the image processing apparatus 7 of FIG. 1, during normal capture (intermittent capture), the image signal (analog signal) 16 from the ITV camera 4 is converted into a digital signal by the A / D converter 17, and capture control is performed. By the image capture signal A11a from the circuit 20, two screens of 512 pixels × 256 lines (1 field 23a) of FIG. 3 (1 frame: 2
3a + 23b) is entirely written in a FIFO (first-in-first-out) memory A22a, and when the image processing execution signal 12 becomes active, the processor 19
Performs image processing (focus degree calculation, etc.) by taking out the image data signal A21a fetched from the FIFO memory A22a. Then, a peak point of the focus degree at which the focus degree calculation result 15 of FIG. 2 obtained by the calculation by the processor 19 is equal to or higher than the specified focus degree is searched for, and the position of the peak point is held (stored in the processor 19). After that, considering the height variation of the DUT 5, the Z-axis stage 3 reaches the lower limit of the allowable range of the Z-axis stage position for focusing on the DUT 5, or the processor 19 When the peak point of the focusing degree is detected, the XYZ axis control device 8 stops the Z axis stage 3. After the Z-axis stage 3 is stopped, the XYZ-axis control device 8 outputs a Z-axis movement completion signal 10 to the image processing device 7, and the image processing device 7 receiving this signal determines the position of the peak point of the focusing degree as the XYZ-axis. The Z-axis movement command signal 13 is sent to the control device 8 and the Z-axis movement command signal 13 is sent to the XYZ-axis control device 8. As a result, the Z-axis stage 3 indicates that the ITV camera 4 has been designated. Move it so that it matches the position of the peak point of focus.

When the above-mentioned normal capture is performed, the FI is acquired for each capture.
Since the FO memory A22a is initialized and the two screens (1 frame: 23a + 23b) in FIG. 3 are written from the start address of the FIFO memory A22a, it takes some time to write the memory and the processor operates, and the image data is fetched. In some cases, the interval becomes long and the above formula (1) cannot be satisfied. Therefore, the image processing apparatus shown in FIG. 1 can execute the continuous capture described below in parallel with the normal capture.

In the case of executing continuous capture, the general position of the object to be measured 5 in the XY axis directions is measured by the above-mentioned normal capture, and the capture region 24 is measured from the processor 19 as shown in FIG. The processor 19 outputs an area designating signal 25 including information of the vertical offset value n line and the measuring width t line for designating the capture area 24, and the horizontal offset value m pixel and the measuring width s pixel. It is sent to the capture control circuit 20. The capture control circuit 20 issues the image capture signal B11b and sends the A / D signal to the FIFO memory B22b only when the area designated by the area designation signal 25 is reached.
The image signal from the converter 17 is written.

Further, during normal writing, FI is set for each fetch.
While the FO memory A22a is initialized and written from the start address, the FIFO memory B22b is initialized and written from the start address only at the start of continuous operation during continuous capture. Initialization is not performed at the time of fetching, and writing is continued from the next address.

Therefore, the amount of writing is limited,
By continuously writing to the FIFO memory B22b without updating it sequentially, (amount of image captured)-(amount of read and image processed) <(capacity of FIFO memory) (2) While the expression (2) is satisfied, the focus degree can be calculated without interruption even if the capture is continuously performed.

If the calculation processing time is long or the number of consecutive fetches is large and the above equation (2) cannot be satisfied, the processor 19 gives an instruction for intermittent fetch every other field or every one frame. Adjustment is possible by instructing the acquisition control circuit 20 at 25. In that case, it is necessary to adjust the moving speed of the Z-axis stage 3 in accordance with the capturing interval.

The processor 19 reads the image data signal B21b from the FIFO memory B22b in synchronism with the continuous capture, and calculates the focus degree for each captured image unit corresponding to the area 24 in FIG.

The Z-axis stage 3 reaches the lower limit value (predetermined position) of the allowable range of the Z-axis stage position for focusing on the DUT 5 in consideration of the height variation of the DUT 5. Alternatively, when the processor 19 detects the peak point of the focus degree, it issues a command to the capture control circuit 20 to end the image capture, and further commands the XYZ axis control device 8 to move to the peak point detection position.

When the XYZ-axis control device 8 finishes moving the Z-axis stage 3 in accordance with the Z-axis movement command signal 13 from the image processing device 7, (IT is adjusted to match the position of the peak point).
When the V camera 4 has been moved in the Z-axis direction), a Z-axis movement completion signal 10 is sent back to the image processing apparatus 7. The image processing device 7 waits for the Z-axis movement completion signal 10 and fetches the image signal 16 from the ITV camera 4 into the FIFO memory A 22a by normal fetching. In the processor 19, the FIFO
Read the image data signal A21a from the memory A22a,
After the focus degree is calculated, if it is equal to or more than the predetermined value, the detailed position of the DUT 5 is directly measured by a method such as pattern matching.

If the peak point of the focusing degree does not reach the specified value during the continuous search, the DUT 5 is discharged as a defective product.
As a result, even if autofocusing is not possible, the measurement time does not extend abnormally, and whatever measurement object 5 comes, the measurement time is always stable and high-speed measurement is possible.

According to this embodiment, the following effects can be obtained.

(1) The object to be measured 5 using the image processing device 7
A high-speed autofocus function can be provided to prevent the positioning accuracy from degrading due to the out-of-focus position of the DUT during positioning, which leads to high-accuracy positioning and shortened processing time. Can be achieved.

(2) The Z-axis stage 3 is moved at a constant speed within the search range as shown by the Z-axis movement speed curve 9 in FIG. 2, and the image processing device 7 performs continuous (or intermittent) periodic sampling. Thus, all the focusing degrees within the search range are calculated and the peak point is searched. This gives 1
Compared to the conventional method of searching while moving every time image processing is performed, it is possible to omit the moving time between points of the Z-axis stage 3 and the moving command time, and minimize the variation in the searching time. I can do things.

In the case of the present embodiment, although the number of search points tends to increase, it is possible to shorten the moving time and the moving command time, and enable the image processing device 7 to perform the area designation acquisition and the continuous acquisition shown in FIG. By doing so, it is possible to realize high-speed autofocus operation by shortening the image processing time per point.

(3) The processor 19 designates a partial area of the image data from the ITV camera 4 to reduce the data amount so that the data can be taken into the FIFO memory B22b as a storage means, and the image data The write capacity is set to the FIFO so that it is not overwritten at the time of import.
By reading and processing by the processor 19 before the memory B22b exceeds the capacity and is overwritten, it is possible to continuously capture image data with a simple configuration.

(4) Conventionally, the measurement time tends to increase depending on the object to be measured, but in the case of the present embodiment, the measurement time is stable and defective products can be easily detected. Further, since the image processing is used for autofocusing, the positioning processing can be performed as it is, so that the measurement of the DUT 5 can be performed with high accuracy and high speed.

In the above embodiment, the object to be measured 5 is placed on the XY axis stage, the ITV camera 4 is mounted on the Z axis stage, and the ITV camera 4 moves up and down with respect to the Z axis. The present invention is applicable even when the object 5 is placed on the XYZ axis stage and the ITV camera 4 is fixed at a predetermined height.

Although the embodiment of the present invention has been described above, it is obvious to those skilled in the art that the present invention is not limited to this and various modifications and changes can be made within the scope of the claims. Ah

[0039]

As described above, according to the present invention,
By continuously changing the relative distance between the object to be measured and the image pickup device in the Z-axis direction, calculating the focus degree every time sampling is performed at a predetermined interval, searching for the peak point, and driving the Z-axis. Compared with the method of searching while moving every image processing, the Z-axis acceleration / deceleration time and the settling time, which occupy most of the moving time, can be omitted, and the time required for the autofocus operation can be shortened. It is possible to stabilize the search time.

Further, when the image data amount is reduced by designating the area in the image capturing, the FIFO memory is used to perform the image processing at the same time as the capturing so that the processing of one cycle from the image data capturing to the calculation of the focus degree can be performed. By increasing the speed, even if the number of times of processing increases, the entire cycle is shortened and a faster autofocus operation is possible.

Conventionally, the measurement time tends to increase depending on the object to be measured, but the use of the present invention stabilizes the measurement time and makes it easy to detect defective products.

Further, since the image processing is used for the autofocus, the positioning processing can be performed as it is, and the highly accurate and high speed measurement can be performed.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an image processing apparatus used in an embodiment of an autofocus method and apparatus by image processing according to the present invention.

FIG. 2 is a time chart showing an autofocus operation in the embodiment of the present invention.

FIG. 3 is an explanatory diagram in the case of performing area designation fetch in the embodiment of the present invention.

FIG. 4 is a perspective view showing a mechanism of a positioning device with an autofocus function used in the embodiment of the present invention.

FIG. 5 is a block diagram of a conventional image processing apparatus.

FIG. 6 is a time chart showing a conventional autofocus operation.

[Explanation of symbols]

1 base 2 XY axis stage 3 Z-axis stage 4 ITV camera 5 DUT 6 monitors 7 Image processing device 8 XYZ axis control device 9 Z-axis movement speed curve 10 Z-axis movement completion signal 11 Image capture signal 12 Image processing execution signal 13 Z-axis movement command signal 14 Measurement position arrival signal 15 Focus degree calculation result 16 image signals (analog signals) 17 A / D converter 18 image memory 19 processors 20 Capture control circuit 21 Image data signal 22a, 22b FIFO memory 23a and 23b fields 24 Capture area 25 area designation signal

Front page continuation (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) G03B 3/00 AF term (reference) 2F065 AA01 AA06 AA20 DD06 FF04 FF10 FF67 JJ03 JJ19 PP02 PP12 QQ03 QQ24 QQ31 2H011 AA03 BA1 BB03 2H05 BA47 CE14 DA22 5C022 AB28 AC41 AC69

Claims (3)

[Claims] 1. An axis control device, an imaging device, and an image processing device that receives image data from the imaging device, wherein the axis control device positions at least the imaging device or the object to be measured in the Z-axis direction. By changing the relative distance in the Z-axis direction between the object to be measured and the imaging device by the axis control device, and detecting a predetermined measurement start point by the axis control device. Then, a measurement position arrival signal is sent to the image processing device, and after receiving the measurement position arrival signal, the image processing device continuously outputs image data including the object to be measured from the imaging device, or Captures intermittently, calculates a focus degree for each capture, searches for a peak point of the focus degree, sends the position of the peak point to the axis control device, and the axis control device determines the position of the peak point. To match the imaging device or the device under test Move the object in the Z-axis direction,
An autofocus method by image processing, characterized in that the object to be measured is brought into a focused position with respect to the imaging device. 2. An axis control device, an imaging device, and an image processing device for receiving image data from the imaging device, wherein the axis control device determines at least the position of the imaging device or the object to be measured in the Z-axis direction. The image processing apparatus includes a storage unit that takes in image data from the image pickup apparatus and a processor, and the axis control apparatus causes a Z-axis direction between the DUT and the image pickup apparatus. By continuously changing the relative distance of the axis control device to detect a predetermined measurement start point, send a measurement position arrival signal to the image processing device, and receive the measurement position arrival signal The processing device continuously or intermittently captures the image data including the object to be measured from the imaging device into the storage unit, calculates the focus degree for each capture by the processor, and calculates the focus degree. Find the peak point Wherein the processor sends the position of the peak point on the axis control device, shaft controller, to match the position of the peak point, the image pickup apparatus or the measured object by moving the Z-axis direction,
An autofocus device by image processing, wherein the object to be measured is brought into a focused position with respect to the image pickup device. 3. The image processing apparatus has an area designating function of designating and capturing a partial area of image data from the image pickup device, and an image including the object to be measured reduced by designating the area. The data is temporarily stored in the storage means, and the storage means has a FIFO memory so that it is not sequentially overwritten when the image data is captured, and the writing capacity is overwritten before the writing capacity exceeds the capacity of the FIFO memory. 3. The autofocus device for image processing according to claim 2, wherein the autofocus device reads out and performs processing by a processor.