JP2005274784A - Image processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quicken focusing operation on a sample on whose surface a light transmissive film is formed. <P>SOLUTION: The respective contrast values c<SB>10</SB>, c<SB>11</SB>and c<SB>12</SB>of respective image data successively picked up when a sample stage 1 is made to descend stepwise are compared with a preset threshold Th. When the contrast values c<SB>10</SB>, c<SB>11</SB>and c<SB>12</SB>are less than the threshold Th, the sample stage 1 is made to descend stepwise by 1st pitch interval width Ha, and when a contrast value c<SB>13</SB>is more than the threshold Th, the sample stage 1 is made to descend stepwise by switching pitch interval width to 2nd pitch interval width Hb smaller than the 1st pitch interval width Ha, and when the contrast value exceeds a peak, the sample stage 1 is made to ascend stepwise by the 2nd pitch interval width Hb and restored to a height position attained when a contrast value c<SB>15</SB>of the peak is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus that shortens the acquisition time of a focused image when a sample such as a semiconductor wafer or a glass substrate of a liquid crystal display is observed through an observation optical system such as a microscope.

  FIG. 9 is a configuration diagram of an observation optical system in the image processing apparatus. A sample 2 such as a semiconductor wafer is placed on the sample stage 1. On the surface 3 of the sample 2, a light-transmitting protective film 4 is formed. Above the sample stage 1, an objective lens 6 of the microscope 5 is provided. Note that the observation light from the objective lens 6 is guided to the eyepiece lens 7 although illustration in the middle is omitted.

  When observing the surface 3 of the sample 2, the sample stage 1 is moved up and down in the same direction as the optical axis P passing through the objective lens 6, and the surface 3 of the sample 2 is the focal plane F of the observation optical system having the objective lens 6. To match. When such a focusing operation is performed by an autofocus mechanism, the focal plane F of the observation optical system having the objective lens 6 may coincide with the surface of the protective film 4 as shown in FIG.

  In order to solve such a problem, Patent Documents 1 and 2 describe a contrast value of image data in order to focus on the surface 3 of the sample 2 in which the protective film 4 is formed on the surface 3. A technique for determining and positioning the sample stage 1 based on the contrast value is described.

In Patent Document 1, as shown in F _{1 to} F ₃ in FIG. 11, the sample stage 1 is lowered at predetermined pitches by intermittent movement, and as shown in FIG. 12, for every pitch interval of the intermittent movement of the sample stage 1. The sample 2 is imaged through the objective lens 6 at the imaging timing. The imaging timing of the sample ₂ is performed every time t ₁ , t ₂ ,..., T ₁₀ every time the sample table 1 stops due to the intermittent motion of the sample table 1, and each image data is acquired by these imaging. . Then, the contrast values c ₁ , c ₂ ,..., C ₁₀ are obtained for each of these image data.

These contrast values are high because the image becomes clear and the contour of the surface of the sample 2 appears clearly if the focal plane F of the observation optical system having the objective lens 6 coincides with the surface of the sample 2. Become. Therefore, the contrast value becomes higher as the intermittent motion of the sample stage 1, as shown in FIG. 12 proceeds, it peaked at time t ₉ to the focus position, then smaller. However, when the interval between the time t ₉ Oite sample table 1 and the objective lens 6 shown a peak value, and when the focal plane F of the observation optical system having an objective lens 6 coincides with the surface of the sample 2. Accordingly, by the sample stage 1 is returned to the interval between the sample stage 1 and the objective lens 6 at time t _9, it is described that the focusing operation is completed.

In Patent Document 2, as shown in FIG. 13, the sample stage 1 is continuously lowered at a constant speed, and the sample 2 is imaged through the objective lens 6 at every constant timing, and each image data is stored. Then, they are each image data each contrast value _{c 1,} c 2, _..., the determined _{c 10,} these contrast value _{c 1,} c 2, _..., when _{c 10} exceeds the peak, when a peak value or displayed as an in-focus image data by reading the image data of the contrast value c _9, it is described that is used. Thus, since the image data when the peak value is shown is read, the operation of returning the sample stage 1 becomes unnecessary, and the time for acquiring the focused image can be shortened compared to Patent Document 1.
Japanese Patent Laid-Open No. 10-48512 JP 2001-59935 A

However, Patent Document 1 captures an image of the sample 2 every time the sample stage 1 is lowered at predetermined pitches by intermittent motion, and contrast values c ₁ , c ₂ ,..., C for each image data acquired by the imaging. _Since the calculation for obtaining ₁₀ is repeated, the load of the calculation process is heavy, and the operation until the focused image is acquired becomes slow.

  In Patent Document 2, if the sample stage 1 and the focal plane F of the observation optical system are separated from each other, image data having a low contrast value is continuously acquired at the start of the focusing operation, and the sample 2 approaches the focal plane F to some extent. Therefore, it is possible to acquire image data having a high contrast value necessary for focus determination. For this reason, when the sample stage 1 and the focal plane F of the observation optical system are separated from each other, it takes time to acquire image data having a high contrast value necessary for focusing determination, and the focusing operation is slowed down. .

  The present invention includes a sample stage on which a sample is placed, an observation optical system that obtains an observation image of the sample, a movement drive unit that relatively changes the distance between the sample stage and the observation optical system by intermittent movement, and observation optics An imaging device that captures an observation image obtained by the system, a contrast calculation unit that calculates and calculates a contrast value of image data of an observation image acquired by imaging of the imaging device, and a contrast value that is obtained in advance by the contrast calculation unit Compared with the set threshold value, if the contrast value is lower than the threshold value, the pitch interval when the interval between the sample stage and the observation optical system by the movement driving unit is intermittently moved is controlled to the first pitch interval width. If the contrast value exceeds the threshold value, the pitch variable control unit that controls the pitch interval to a second pitch interval width narrower than the first pitch interval width, and the interval between the sample stage and the observation optical system When the contrast value obtained by the contrast calculation unit exceeds the peak value every time the intermittent motion is performed with the second pitch interval width, the distance between the sample stage that has obtained the peak value by controlling the movement driving unit and the observation optical system is set. The image processing apparatus includes a focusing control unit that returns and obtains a focused observation image by the observation optical system.

  The present invention includes a sample stage on which a sample is placed, an observation optical system that obtains an observation image of the sample, a movement drive unit that continuously changes the distance between the sample stage and the observation optical system at a relatively constant speed, An imaging device that captures an observation image obtained by the observation optical system at a certain timing, a storage unit that stores image data of the observation image acquired by imaging of the imaging device, and an observation acquired by imaging of the imaging device The contrast calculation unit that calculates and calculates the contrast value of the image data of the image is compared with the contrast value calculated by the contrast calculation unit and a preset threshold value, and if the contrast value is below the threshold value, the movement drive unit The speed at which the distance between the sample stage and the observation optical system is continuously changed is controlled to the first speed, and if the contrast value exceeds the threshold value, the speed is controlled to the second speed that is slower than the first speed. When the contrast value calculated by the contrast calculation unit exceeds the peak value while the interval between the variable speed control unit, the sample stage and the observation optical system is continuously changed at the second speed, the peak value And an in-focus image reading unit that reads out image data from the storage unit as an in-focus image as the in-focus image.

  The present invention can provide an image processing apparatus having a fast focusing operation for a sample having a light-transmitting film formed on the surface.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The same parts as those in FIG. 9 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 is a configuration diagram of an image processing apparatus. The sample stage 1 is provided with a moving mechanism 10. This moving mechanism 10 moves the sample stage 1 at every pitch interval in the same direction (Z direction) as the optical axis P passing through the objective lens 6 during the focusing operation. Make it. The moving mechanism 10 has a configuration in which, for example, a ball screw 12 is connected to a shaft of a motor 11, and a slide body 13 that is screwed into the ball screw 12 is provided on the sample stage 1. The motor 11 is rotationally driven by the motor drive unit 14.

  An imaging device 15 such as a CCD is provided on the optical axis P passing through the objective lens 6. The imaging device 15 captures an observation image of the sample 2 obtained by the observation optical system having the objective lens 6 and outputs the image signal.

  The image capturing unit 16 captures the image signal output from the imaging device 15 and converts the image data into a file. The filed image data is stored in the storage unit 18 under the control of the control unit 17. Note that when multi-threading is used, contrast calculation can be performed by another thread, so that the speed can be increased.

  The image processing unit (contrast calculation unit) 19 reads each image data sequentially stored in the storage unit 18, and for example, on the line L that crosses the image data D in an oblique direction as shown in FIG. The brightness value is read and a contrast value is calculated from the brightness value.

  For example, a semiconductor wafer or a glass substrate of a liquid crystal display as the sample 2 has a lattice-like regular pattern formed on the surface thereof. Even when the brightness value in the same direction as the pattern direction is read for such a lattice pattern and the contrast value is obtained, the contrast value does not represent the contrast value of the entire image data D. On the other hand, the contrast value of the entire image data D is obtained by reading the luminance value on the line L that crosses in an oblique direction. The contrast value of the entire image data D is not limited to reading the luminance value on the diagonal line L, but may be the luminance value on two diagonal lines L intersecting each other. You may read the luminance value in each area | region of four inside corners.

  The control unit 17 controls the pitch interval when the sample stage 1 is moved up and down based on the contrast values sequentially obtained by the image processing unit 19, and has a pitch variable control unit 20 and a focus control unit 21. .

  The pitch variable control unit 20 compares each contrast value sequentially obtained by the image processing unit 19 with a preset threshold value Th. If the contrast value is lower than the threshold value Th, the sample table 1 as shown in FIG. A command is issued to the motor drive unit 14 to control the first pitch interval width Ha, which is a rough pitch interval when the step is lowered, and if the contrast value exceeds the threshold Th, the pitch interval is set to the first pitch interval width. A command for controlling the second pitch interval width Hb narrower than Ha is issued to the motor drive unit 14. For example, the second pitch interval width Hb is preferably set within the depth of field of the observation optical system having the objective lens 6.

  When each contrast value sequentially obtained by the image processing unit 19 exceeds the peak value every time the sample stage 1 is stepped down by the second pitch interval width Hb, the focusing control unit 21 causes the motor driving unit 14 to A reverse rotation command is issued, and the sample stage 1 is stepped up by the second pitch interval width Hb to return to the height position of the sample stage 1 when the peak value of the contrast value is obtained.

  Next, the focusing operation of the apparatus configured as described above will be described.

  At the start of the focusing operation, the sample stage 1 is raised and approached to the objective lens 6. Therefore, in the focusing operation, the sample stage 1 is lowered and moved away from the objective lens 6. Thereby, it can avoid beforehand that the objective lens 6 contact | abuts the sample stand 1 when the sample stand 1 is raised.

As shown in FIG. 4, the variable pitch control unit 20 issues a command to the motor drive unit 14 to lower the sample table 1 with a coarse first pitch interval width Ha. Upon receiving this command, the motor drive unit 14 rotates and drives the motor 11 for a period corresponding to the first pitch interval width Ha, and performs an intermittent motion to stop the motor 11 for a predetermined stop period S after the rotation drive. Make it. As a result, when the motor 11 is driven to rotate at a time corresponding to the first pitch interval width Ha at each time t ₁₀ , t ₁₁ , t ₁₂ , the ball screw 12 is rotated by this rotation, so that the ball screw 12 is screwed. The sample stage 1 is stepped down by the first pitch interval width Ha through the sliding body 13 to be joined.

  In each stop period S each time the sample stage 1 moves down, the imaging device 15 captures an observation image of the sample 2 obtained by the observation optical system having the objective lens 6 and outputs the image signal.

  As an example, the image capturing unit 16 may be a computer interface board with an image processing function. The image capturing unit 16 captures an image signal output from the imaging device 15 and converts the image data into a file. These image data are stored in a storage unit 18 such as a hard disk of a computer under the control of the control unit 17. In addition, if the imaging device 15 always captures an observation image of the sample 2 and outputs the image signal, the image processing unit 19 outputs the image signal from the imaging device 15 for each stop period S of the intermittent motion. Is taken into a file.

  The image processing unit 19 operates according to the focusing operation flowchart shown in FIG. In step # 1, the image processing unit 19 captures the image signal output from the imaging device 15 as described above, converts the image data into a file, and stores the file in the storage unit 18.

The image processing unit 19, at step # 2, reads out the image data sequentially stored in the storage unit 18 sequentially obtains operation each contrast value _{c 10, c 11, c 12} of the image data, in step # 3 The storage unit 18 stores data such as the contrast values c ₁₀ , c ₁₁ , c ₁₂ (= ct), the distance ht between the objective lens 6 and the sample stage 1, times t ₁₀ , t ₁₁ , t ₁₂ .

In step # 4, the variable pitch control unit 20 compares the contrast values c ₁₀ , c ₁₁ , c ₁₂ sequentially obtained by the image processing unit 19 with a preset threshold Th. As a result of this comparison, if each of the contrast values c ₁₀ , c ₁₁ , c ₁₂ is below the threshold Th, the pitch variable control unit 20 steps down the sample stage 1 as shown in FIG. 4 in step # 5. Is maintained at the first pitch interval width Ha.

With such sample table 1 is lowered successively step at a first pitch interval width Ha, the contrast value c ₁₃ of the image data captured by the image capture unit 16 exceeds the threshold value Th, for example, in a time t _13, the pitch variation control unit In step # 6, 20 issues a command to the motor drive unit 14 to switch and control the pitch interval to the second pitch interval width Hb that is narrower than the first pitch interval width Ha. Thereby, the sample stage 1 has the second pitch interval within a range of 2 to 3 times the depth of field of the observation optical system having the objective lens 6 at each time t ₁₃ , t ₁₄ ,..., T ₁₆ , for example. Step down with the width Hb.

Even in a state where the sample stage 1 is switched to the second pitch interval width Hb and stepped down, the image processing unit 19 performs the contrast values c ₁₃ , c ₁₄ ,... Of each image data acquired by the imaging device 15. , C ₁₆ are sequentially calculated and obtained.

When the sample stage 1 is stepped down step by step with the second pitch interval width Hb, the image picked up by the image pickup device 15 is from the unclear state as shown in FIG. 5A from the observation optical system having the objective lens 6. When the focal plane F coincides with the surface of the sample 2, the surface of the sample 2 as shown in FIG. 2B is clearly displayed, and the image becomes unclear as shown in FIG. become. Thereby, the contrast value when the focal plane F of the observation optical system coincides with the surface of the sample 2 becomes a peak value. Here, as shown in FIG. 4, the contrast values c ₁₃ , c ₁₄ ,..., C ₁₆ when the sample stage 1 is stepped down by the second pitch interval width Hb are contrast values c ₁₃ , c ₁₄ , sequentially increases and c _15, is reduced by the contrast value _{c 16.}

Focus control section 21, at step # 8, successively each contrast value determined _c 13 by the image processing unit _19, c 14, _..., is stored as a peak value greater contrast value _{c 15} sequentially compares the _{c 16} together At the same time, it is determined that the contrast peak value c ₁₅ , that is, the in-focus position is exceeded. Then, the focusing controller 21, in step # 9, issues an instruction of reverse rotation to the motor drive unit 14 at time t ₁₆ beyond the contrast value c ₁₅ of the peak value, the sample stage 1 second pitch distance and step is raised by the width Hb, returning the sample stage 1 in the height position when the obtained contrast value c ₁₅ peaks. As a result, the focal plane F of the observation optical system having an objective lens 6 at time t _17, the focusing operation is completed in agreement with the surface of the sample 2.

As described above, according to the first embodiment, the contrast values c ₁₀ , c ₁₁ , c _{12 of} each image data sequentially captured when the sample stage 1 is stepped down and the preset threshold Th If the contrast values c ₁₀ , c ₁₁ , c ₁₂ are below the threshold Th, the sample stage 1 is stepped down by the first pitch interval width Ha, and the contrast value c ₁₃ exceeds the threshold Th. Then, the sample stage 1 is switched to the second pitch interval width Hb that is narrower than the first pitch interval width Ha, and the step descends. When the contrast value exceeds the peak, the sample stage 1 is changed to the second pitch interval width Hb. step moved up back to the height position at which to obtain a contrast value c ₁₅ peaks.

Thereby, the time of the focusing operation | movement which makes the focal plane F of the observation optical system which has the objective lens 6 correspond with the surface of the sample 2 in which the protective film 4 was formed can be shortened. For example, can be completed at time t ₁₇ a focusing operation as shown in FIG. 4, it can be shortened by focusing completion time t ₁₈ time than tg in the conventional.

  Further, for example, the second pitch for obtaining the contrast value of at least three points including the peak value within the depth of field of the observation optical system having the objective lens 6 or within the range of several times the depth of field, for example, 2 to 3 times. Since the focusing operation is performed with the step width lowered by the interval width Hb, the focusing operation can be performed even when the objective lens 6 having a narrow depth of field is used, and even when it is desired to obtain a fine image, the focusing operation can be performed with high accuracy. And the focused image can be acquired.

  Furthermore, even if the focusing operation is performed from a state where the distance between the focal plane F of the observation optical system having the objective lens 6 and the sample 2 is separated, a focused image can be obtained in a shorter time than the conventional technique.

  Next, a second embodiment of the present invention will be described with reference to the drawings. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 6 is a configuration diagram of the image processing apparatus. The difference from the first embodiment of the image processing apparatus is that the motor drive unit 14 issues a command for continuously lowering the motor 11 at a constant speed.

  The imaging device 15 captures an observation image of the sample 2 obtained by the observation optical system having the objective lens 6 at a certain timing and outputs the image signal. Note that the image signal of the moving image continuously output from the imaging device 15 by the image capturing unit 16 may be captured at a certain timing.

  The control unit 17 controls the speed when the sample stage 1 is moved up and down based on the contrast values sequentially obtained by the image processing unit 19, and includes a speed variable control unit 22 and a focused image reading unit 23. .

The speed variable control unit 22 compares the contrast value sequentially obtained by the image processing unit 19 with a preset threshold value Th, and if the contrast value is lower than the threshold value Th, the sample table for the motor driving unit 14 is used. If the command to control the descending speed of 1 to the first speed v ₁ faster than normal is issued and the contrast value exceeds the threshold Th, the descending speed of the sample stage ₁ is set to be slower than the first speed v ₁ . A command for shifting to a speed 2 of ₂ is issued.

  The focused image reading unit 23 obtains the peak value when the contrast value sequentially obtained by the image processing unit 19 exceeds the peak value while the sample stage 1 is continuously lowered at the second speed. Image data at the height position of the sample stage 1 is read from the storage unit 18 as a focused image and displayed on a display or the like.

  Next, the focusing operation of the apparatus configured as described above will be described.

At the start of the focusing operation, the variable speed control unit 22 issues a command to the motor drive unit 14 to continuously lower the sample stage ₁ at a first speed v ₁ that is faster than normal, as shown in FIG. Thereby, the sample stage 1 is continuously lowered at the first speed v ₁ that is faster than usual. At this time, the imaging device 15 captures an observation image of the sample 2 obtained by the observation optical system having the objective lens 6 at every predetermined timing and outputs the image signal. The image capturing unit 16 captures an image signal from the imaging device 15, converts the image data into a file, and stores the file in the storage unit 18. The image processing unit 19 reads out each image data sequentially stored in the storage unit 18 and sequentially calculates and obtains each contrast value c ₂₀ , c ₂₁ , c ₂₂ of these image data.

At this time, since each contrast value c ₂₀ , c ₂₁ , c ₂₂ is lower than a preset threshold value Th, the speed variable control unit 22 makes the sample table 1 with respect to the motor drive unit 14 as shown in FIG. Is maintained at a _first speed v ₁ that is faster than normal. The intervals between the height positions of the sample stage 1 when obtaining these contrast values c ₂₀ , c ₂₁ , c ₂₂ are continuously lowered at the first speed v ₁ at which the sample stage 1 is faster than usual. , Become wider.

If the contrast value c ₂₃ of the image data captured by the image capture unit 16, for example, in a time t ₂₃ is lowered advances of the sample table 1 is above the threshold value Th, variable speed controller 22, a motor drive unit as shown in FIG. 6 14, a command to shift the descending speed of the sample stage 1 to a second speed v ₂ that is slower than the first speed v ₁ is issued.

Since then, the imaging device 15 captures the observation image of the sample 2 obtained by the observation optical system having the objective lens 6 at a certain timing, so that the image processing unit 19 is sequentially stored in the storage unit 18. Each contrast value c ₂₄ , c ₂₅ , c ₂₆ of each image data is sequentially calculated and obtained. At this time, the intervals between the height positions of the sample stage 1 when obtaining the contrast values c ₂₄ , c ₂₅ , and c ₂₆ are set at a second speed v ₂ where the sample stage 1 is slower than the first speed v _1. Since it descends continuously, it becomes narrower. The interval between the height positions of the sample stage 1 is set within the depth of field of the observation optical system having the objective lens 6.

When the focus control unit 21 sequentially compares the contrast values c ₂₄ , c ₂₅ , and c ₂₆ that are sequentially obtained by the image processing unit 19 and determines the largest contrast value c ₂₅ as a peak value, the objective lens at this time It is determined that the focal plane F of the observation optical system having 6 coincides with the surface of the sample 2, and the image data at the height position of the sample stage 1 at the time t ₂₅ when the peach value is obtained is the focused image. Are read out from the storage unit 18 and displayed on a display or the like.

As described above, according to the second embodiment, if the contrast value of each image data sequentially captured when the sample stage 1 is continuously lowered is below the threshold Th, the sample stage 1 is lowered. If the speed is controlled to the first speed v ₁ that is faster than normal and the contrast value exceeds the threshold Th, the descending speed of the sample stage 1 is changed to a second speed v ₂ that is slower than the first speed v _1. The image data at the height position of the sample table 1 that has been shifted and obtained the peak value of the contrast value is read out from the storage unit 18 as a focused image and displayed on a display or the like.

Accordingly, the focusing operation time for matching the focal plane F of the observation optical system having the objective lens 6 with the surface of the sample 2 on which the protective film 4 is formed, for example, as shown in FIG. The focusing operation can be completed even at a time t _{25 which} is shorter than the focusing completion time t ₂₈ by a time th ₂₅ and the distance between the focal plane F of the observation optical system having the objective lens 6 and the sample 2 is separated. The time until it can be shortened.

Further, the distance between the height positions of the sample stage 1 for obtaining the contrast values when the sample stage ₁ is lowered at the relatively slow second speed v ₂ is set as the object field of the observation optical system having the objective lens 6. Since the depth is set within the depth, the focusing operation can be performed with high accuracy and a fine image can be acquired.

  Furthermore, since the image data when the peak value of the contrast value is obtained is read from the storage unit 18 and displayed on a display or the like, there is no need to perform the operation of returning the sample stage 1, and until the focused image is obtained accordingly. Can be shortened.

  Next, a third embodiment of the present invention will be described with reference to the drawings. 1 and 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the case of the sample 2 in which the contrast values of the respective image data sequentially obtained by the image processing unit 19 are low, the respective contrast values may not exceed the threshold Th even in the vicinity of the focal plane F of the observation optical system having the objective lens 6. .

  In order to deal with this case, in the image processing apparatus shown in FIG. 1, the folding distance Lr of the sample stage 1 as shown in FIG. This folding distance Lr is set to approximately 10 to 20 times the depth of field of the observation optical system having the objective lens 6.

  If the contrast control unit 21 sequentially lowers the contrast value obtained by stepping down the sample stage 1 beyond the turn-back distance Lr, the focusing control unit 21 stops stepping down the sample stage 1 and performs the intermittent motion direction. And the sample stage 1 is stepped up at the second pitch interval Hb. Then, when each contrast value reaches the maximum value, the focus control unit 21 determines the height position of the sample stage 1 that has obtained the maximum value as the focus position. In this case, the focus control unit 21 sequentially compares the contrast values obtained sequentially and stores a large contrast value as a peak value. When it is determined that the peak value, that is, the focus position is exceeded, the motor drive is performed again. A reverse rotation command is issued to the unit 14, and the sample stage 1 is returned to the height position when the sample table 1 obtains the peak contrast value.

  On the other hand, in the image processing apparatus illustrated in FIG. 6, the folding distance Lr of the sample stage 1 is set in the focusing control unit 21 as in the image processing apparatus illustrated in FIG. 1.

The focused image reading unit 23 stops the continuous lowering of the sample stage 2 if the contrast values sequentially obtained by sequentially lowering the sample stage 1 exceed the turn-back distance Lr and do not exceed the threshold Th. and continuously increase at a relatively slow second velocity v ₂ by reversing the direction of movement of the sample stage 2. Then, when each contrast value reaches the maximum value, the focused image reading unit 23 determines the height position of the sample table 1 that has obtained the maximum value as the focused position, and stores the image data at this time as a focused image. Read from unit 18.

  As described above, according to the third embodiment, the sample 2 is a special sample 2 with a low contrast value of the image data, and even if the contrast value does not exceed the threshold value Th, it is ensured with a small second pitch interval Ha. A focus peak point is detected, and a focusing operation can be performed with high accuracy within the depth of field of the observation optical system having the objective lens 6 so that a fine image can be obtained.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  In the first and second embodiments, the sample stage 1 is stepped down or continuously lowered, but the observation optical system having the objective lens 6 is stepped up or continuously raised. Also good. In this case, the objective lens 6 is lowered and raised from the height position approaching the sample stage 1 so that the peak of the contrast value appears when the observation optical system is raised.

1 is a configuration diagram showing a first embodiment of an image processing apparatus according to the present invention. The focusing operation | movement flowchart in the same apparatus. FIG. 3 is a schematic diagram showing lines on image data for reading a luminance value in order to obtain a contrast value by an image processing unit in the apparatus. The figure which shows the imaging timing of a sample when a sample stand is intermittently moved in the same apparatus. The schematic diagram which shows the clear state of each image imaged when making it step-fall with the apparatus. The block diagram which shows 2nd Embodiment of the image processing apparatus which concerns on this invention. The figure which shows the imaging timing of a sample when the sample stand is continuously descended at a constant speed in the apparatus. The figure which shows the folding distance of the sample stand in 3rd Embodiment of the image processing apparatus which concerns on this invention. The block diagram of the observation optical system in the conventional image processing apparatus. The figure which shows the malfunction which matches the focal plane of the observation optical system which has the objective lens by the conventional image processing apparatus on the protective film on a sample surface. The figure which shows the intermittent motion of the sample stand by the conventional image processing apparatus. The figure which shows the imaging timing of the sample when carrying out the intermittent motion by the conventional image processing apparatus. The figure which shows the imaging timing of the sample when the sample stand by the conventional image processing apparatus is continuously lowered at a constant speed.

Explanation of symbols

  1: sample stage, 2: sample, 3: sample surface, 4: protective film, 5: microscope, 6: objective lens, 7: eyepiece lens, 10: moving mechanism, 11: motor, 12: ball screw, 13: sliding body , 14: motor drive unit, 15: imaging device, 16: image capturing unit, 17: control unit, 18: storage unit, 19: image processing unit (contrast calculation unit), 20: variable pitch control unit, 21: focusing Control unit, 22: speed variable control unit, 23: focused image reading unit.

Claims (7)

A sample stage on which the sample is placed;
An observation optical system for obtaining an observation image of the sample;
A movement drive unit that intermittently moves the distance between the sample stage and the observation optical system to change relatively,
An imaging device for capturing the observation image obtained by the observation optical system;
A contrast calculation unit for calculating a contrast value of image data of the observation image acquired by imaging of the imaging device;
The contrast value obtained by the contrast calculation unit is compared with a preset threshold value, and if the contrast value is below the threshold value, the distance between the sample stage and the observation optical system by the movement driving unit If the contrast value exceeds the threshold value, the pitch interval is controlled to the first pitch interval width, and the pitch interval is narrower than the first pitch interval width. A variable pitch control unit that controls the width;
When the interval between the sample stage and the observation optical system is intermittently moved at the second pitch interval width, and the contrast value obtained by the contrast calculation unit exceeds a peak value, the movement driving unit is controlled. A focusing control unit that obtains the focused observation image by the observation optical system by returning to the interval between the sample stage and the observation optical system obtained the peak value;
An image processing apparatus comprising: The image processing apparatus according to claim 1, wherein the pitch variable control unit sets the second pitch interval width to 2 to 3 times the depth of field of the observation optical system. If the contrast value obtained by the contrast calculation unit exceeds the threshold even if the contrast value exceeds the focusing range, the focusing control unit reverses the intermittent motion direction of the interval between the sample stage and the observation optical system. When the contrast value obtained by the contrast calculation unit reaches a maximum value every time the interval between the sample stage and the observation optical system is intermittently moved at the second pitch interval, the sample having the maximum value is obtained. The image processing apparatus according to claim 1, wherein the observation image is focused by the observation optical system by returning to a distance between the stage and the observation optical system. A sample stage on which the sample is placed;
An observation optical system for obtaining an observation image of the sample;
A movement drive unit for continuously changing the distance between the sample stage and the observation optical system at a relatively constant speed;
An imaging device that captures the observation image obtained by the observation optical system at certain timings;
A storage unit that stores image data of the observation image acquired by imaging of the imaging device;
A contrast calculation unit for calculating a contrast value of image data of the observation image acquired by imaging of the imaging device;
The contrast value obtained by the contrast calculation unit is compared with a preset threshold value, and if the contrast value is below the threshold value, the distance between the sample stage and the observation optical system by the movement driving unit A speed variable control unit that controls the speed for continuously changing the speed to the first speed, and controls the speed to a second speed that is slower than the first speed if the contrast value exceeds the threshold value. When,
When the interval between the sample stage and the observation optical system is continuously changed at the second speed and the contrast value obtained by the contrast calculation unit exceeds the peak value, the peak value is obtained. A focused image reading unit for reading out the image data from the storage unit as a focused image when the distance between the sample stage and the observation optical system;
An image processing apparatus comprising: If the contrast value does not exceed the threshold value even when the interval between the sample stage and the observation optical system reaches a predetermined folding distance, the focused image reading unit The sample stage obtained by inverting the direction of change of the distance between the sample stage and the distance between the sample stage and the observation optical system at the second speed to obtain the maximum contrast value obtained by the contrast calculation unit The image processing apparatus according to claim 4, wherein the image data at the interval between the image and the observation optical system is read from the storage unit as a focused image. 6. The image processing apparatus according to claim 5, wherein the folding distance is set to 10 to 20 times the depth of field of the observation optical system. The image processing apparatus according to claim 1, wherein the sample has a light-transmitting film formed on a surface thereof.

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