JP2005258420A - Device and method for automatic focusing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing device which can conduct automatic focusing of observation objects accurately even from image data in which observation objects mingle with dust, by using a threshold value calculated from the background color of an image data for distinguishing observation objects from dust. <P>SOLUTION: The automatic focusing device is provided with a photographing means 100 which photographs the transmitted light generating from a light source 101 irradiating light to observation objects, an index value operation means 120 which operates an index value that indicates focus information of the observation objects from the image data output from the photographing means 100, and a focus control means 122 which controls the focus of the photographing means 100 in order to obtain the optimum focus position of the observation objects based on the index value. Dust ingredients are removed by using as the background color information of image data, and by conducting an operation of an index value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an autofocus device and an image processing system, and more particularly to an autofocus device and an autofocus method using transmitted light.

  The conventional autofocus device performs high-frequency emphasis on the image data captured by the camera using a high-pass filter in order to determine how much the focus is from the image of the camera, and the absolute value of the output value of the high-pass filter Alternatively, the focus position is determined based on an index value obtained by averaging the squares of the output values, and the objective lens is moved to the determined focus position to perform an autofocus operation (for example, Patent Document 1).

  In particular, a microscope or the like that performs precise analysis is required to accurately focus on the observation target.

  However, in the above-described conventional technique, it may be difficult to accurately perform autofocus on the observation target due to the influence of noise such as dust.

  Therefore, as an autofocus method that reduces the influence of noise, when autofocus is performed using transmitted light, the range of autofocus from the entire field of view captured by the camera is limited to the range where the observation target exists. A method has been proposed in which only image data within the range is subjected to autofocus calculation.

FIG. 9 is a diagram showing a configuration of a conventional autofocus device.
9 includes a light source 901, a film 902, a lens unit 903, an image sensor 904, an A / D converter 905, a calculation unit 906, a control unit 907, a range specifying unit 908, a stepping motor 909, and a sensor drive. Part 910.
The light source 901 irradiates the film 902 with light.

  The lens unit 903 performs zooming and focusing on an image photographed on the film 902. The lens unit 903 is moved and controlled by driving a stepping motor 909.

  The image sensor 904 is a solid-state imaging device provided on the conjoint surface of the lens unit 903 and reads a film image. The movement of the image sensor 904 is controlled by driving the sensor driving unit 910.

The A / D converter 905 performs A / D conversion of image data read by the image sensor 904.
The calculation unit 906 calculates a focus value for the A / D converted image data.

The control unit 907 controls the stepping motor 909 and the sensor driving unit 910 based on the output from the range specifying unit 908 and the output from the calculation unit 906.
The range designation unit 908 designates an image range in advance.

The operation of the autofocus device having such a configuration will be described.
First, light is irradiated from the light source 901 to the film 902, and transmitted light is read by the image sensor 904 through the lens unit 903.

  The A / D converter 905 quantizes the image data output from the image sensor 904. The control unit 907 controls the stepping motor 909 that drives the lens unit 903 and the sensor drive unit 910 that drives the image sensor 904 based on the output signal of the calculation unit 906 and the output signal of the range specifying unit 908.

The automatic focus is executed by using image data in a range where there is a high possibility that an effective image designated in advance by the range designating unit 908 exists, and thereby the optimum focus position is obtained by the calculation unit 906. (For example, refer to Patent Document 2).
Japanese Patent Laid-Open No. 10-042184 (page 3-7, FIG. 1) Japanese Patent Laid-Open No. 2001-154269 (page 18, FIG. 7)

  However, since the conventional autofocus device limits the autofocus range to the periphery of the observation target, it is difficult to set the range when there is a mixture of the observation target and dust. Even when the object is sufficiently large with respect to dust or the like, there is a problem that it is not possible to perform autofocus accurately.

  The present invention has been made to solve the above problems, and provides an autofocus device and an autofocus method capable of performing autofocus reliably and at high speed even when an observation object and dust are mixed. The purpose is to provide.

  In order to solve the above-described conventional problems, an autofocus device according to claim 1 of the present invention includes a light source that irradiates light to an observation target, and transmitted light that is generated by irradiating the observation target with light from the light source. An imaging unit that captures and outputs image data, and an index that calculates background value information from the image data output from the imaging unit and calculates an index value that represents the focus information of the observation target based on the background color information It is characterized by comprising a value calculating means and a focus control means for controlling the focus of the photographing means so as to obtain the optimum focus position of the observation object based on the index value.

  Accordingly, it is possible to provide an autofocus device that can perform accurate autofocus even when dust or the like is mixed in the observation target.

  According to a second aspect of the present invention, there is provided the automatic focusing apparatus according to the first aspect, wherein the index value calculation means includes a background color calculation means for obtaining the background color information from the image data, Threshold value calculation means for obtaining a threshold value of the image data from the background color information, clip means for clipping the image data with the threshold value, and a high frequency component of the image data from an output signal of the clip means And a calculation means for obtaining the index value from the high-pass filter output signal.

  As a result, it is possible to easily discriminate between the observation object and dust from the background color information, and even if dust or the like is mixed in the observation object, appropriate automatic focusing can be performed without being affected by the dust.

  According to a third aspect of the present invention, there is provided the automatic focusing apparatus according to the first aspect, wherein the index value calculation means includes a background color calculation means for obtaining the background color information from the image data, Threshold calculation means for obtaining a threshold value of the image data from the background color information, clip means for clipping the image data with the threshold value, and clipped by the image data or the clip means Selection means for selecting and outputting any of the image data, a high-pass filter for extracting a high-frequency component of the image data from the output signal of the selection means, and a calculation means for obtaining the index value from the high-pass filter output signal It is characterized by having.

  As a result, the observation object and dust can be easily discriminated from the background color information, and even if dust or the like is mixed in the observation object, appropriate automatic focusing can be performed without being affected by the dust. .

According to a fourth aspect of the present invention, in the automatic focusing device according to the third aspect, the focus control means has at least two stages of focus control modes of coarse adjustment and fine adjustment. The selection means selects the image data when the focus control means performs coarse adjustment, and selects the image data clipped by the clip means when the focus control means performs fine adjustment; It is characterized by.
Thereby, even if an observation object and dust are mixed, accurate autofocus can be performed.

The autofocus device according to claim 5 of the present invention is the autofocus device according to claim 3, wherein the focus control means performs the fine adjustment after performing the coarse adjustment. It is characterized by that.
Thereby, an appropriate focal position can be obtained accurately and at high speed.

  The autofocus device according to claim 6 of the present invention is the autofocus device according to claim 2 or 3, wherein the background color calculation means includes a histogram generation means for generating a histogram of the image data, An image intensity value corresponding to the maximum value of the histogram is output as background color information.

  This prevents erroneous detection of background color information due to dark current noise or the like of the CCD element, reduces the influence of dust as much as possible without degrading the performance, and can perform appropriate autofocus.

  According to a seventh aspect of the present invention, there is provided the automatic focusing apparatus according to the second or third aspect, wherein the background color calculation means calculates the maximum value of the image intensity of the image data. And a maximum value of the image intensity obtained by the maximum value calculation means is output as background color information.

  This prevents erroneous detection of background color information due to dark current noise or the like of the CCD element, reduces the influence of dust as much as possible without degrading the performance, and can perform appropriate autofocus.

  According to an eighth aspect of the present invention, there is provided the automatic focusing apparatus according to the second or third aspect, wherein the background color calculation means calculates an average value of an image intensity of the image data. And an average value of the image intensity obtained by the average value calculation means is output as background color information.

  This prevents erroneous detection of background color information due to dark current noise or the like of the CCD element, reduces the influence of dust as much as possible without degrading the performance, and can perform appropriate autofocus.

  According to a ninth aspect of the present invention, in the automatic focusing apparatus according to the second or third aspect, the background color calculation means divides the image data into a plurality of regions, A histogram generating unit for each region for generating a histogram is provided, and an image intensity value corresponding to the maximum value of the histogram of each region is output as background color information of each region.

  As a result, background color information can be obtained for each region, so that it is possible to cope with uneven background colors in the entire image data, and to prevent erroneous detection of background color information due to dark current noise or the like of the CCD element. The effect of dust can be reduced as much as possible without degrading performance, and the object to be observed can be accurately focused.

  According to a tenth aspect of the present invention, in the automatic focusing device according to the second or third aspect, the background color calculation means divides the image data into a plurality of areas, A region-specific maximum value calculating means for obtaining a maximum value of the image intensity, and outputting the maximum value of the image intensity of each region obtained by the region-specific maximum value calculating means as background color information of each region; Features.

  As a result, background color information can be obtained for each region, so that it is possible to cope with uneven background colors in the entire image data, and to prevent erroneous detection of background color information due to dark current noise or the like of the CCD element. The effect of dust can be reduced as much as possible without degrading performance, and the object to be observed can be accurately focused.

  According to an eleventh aspect of the present invention, in the autofocus device according to the tenth aspect, the background color calculation means has the plurality of image intensities obtained by the region-specific maximum value calculation means. The smallest image intensity value among the maximum values is output as background color information.

  As a result, the background color unevenness of the entire image data can be dealt with, and the background color information due to the dark current noise of the CCD element is prevented from being erroneously detected. And focus accurately on the observation target.

  According to a twelfth aspect of the present invention, in the autofocus device according to the second or third aspect, the background color calculation means divides the image data into a plurality of regions, An average value calculation means for each area for obtaining an average value of the image intensity, and outputting the average value of the image intensity in each area obtained by the average value calculation means for each area as background color information of each area; Features.

  As a result, background color information can be obtained for each region, so that it is possible to cope with uneven background colors in the entire image data, and to prevent erroneous detection of background color information due to dark current noise or the like of the CCD element. The effect of dust can be reduced as much as possible without degrading performance, and the object to be observed can be accurately focused.

  According to a thirteenth aspect of the present invention, in the autofocus device according to any one of the first to tenth aspects of the present invention, the observation object is of a predetermined size and is less than noise mixed in the image data. Is also large.

  According to a fourteenth aspect of the present invention, there is provided an autofocus method according to the present invention, wherein transmitted light generated by irradiating light on an observation target is photographed using an image sensor, and image data obtained from the photographed image is used for the image sensor. An autofocus method for focusing, a background color information calculation step for calculating background color information from the image data, a threshold calculation step for calculating a threshold value of the image data from the background color information, and the image data A clip processing step for clipping with the threshold value, a high frequency component extracting step for extracting a high frequency component of the clipped image data, and an index value representing the focus information of the observation target is calculated from the extracted high frequency component An index value calculation step to perform, and obtaining an optimum focus position of the observation target based on the index value Including a focus control step of controlling the focus of the image pickup device, characterized in that.

  Thereby, even when the observation object and dust are mixed, the observation object can be accurately focused.

  In the autofocus method according to the fifteenth aspect of the present invention, the transmitted light generated by irradiating the observation target with light is photographed by using the image sensor, and the image sensor of the image sensor is obtained from image data obtained from the photographed image. An autofocus method for focusing, a background color information calculation step for calculating background color information from the image data, a threshold calculation step for calculating a threshold value of the image data from the background color information, and the image data A clip processing step for clipping with the threshold value, a high frequency component extraction step for extracting the high frequency component of the image data or the data after the clip processing, and a rough adjustment of the focus of the image sensor are extracted from the image data. Select the high frequency component and finely adjust the focus of the image sensor. An index value calculation step for selecting a high-frequency component extracted from the processed image data, calculating an index value representing the focus information of the observation target from the selected high-frequency component, and the observation target based on the index value And a focus control step for controlling the focus of the image sensor so as to obtain an optimal focus position.

  Thereby, even when the observation target and dust are mixed, it is possible to accurately focus on the observation target at high speed and accurately.

  According to the autofocus device of the present invention, a light source that irradiates light to the observation target, a photographing unit that captures the transmitted light generated by irradiating the observation target with light from the light source, and outputs it as image data; Index value calculation means for obtaining background color information from image data output from the photographing means and calculating an index value representing the focus information of the observation target based on the background color information; and the observation target based on the index value A focus control unit that controls the focus of the photographing unit so as to obtain the optimum focus position of the above-mentioned, provides an autofocus device that can perform accurate autofocus even if dust or the like is mixed in the observation target can do.

  Embodiments of an autofocus device and an autofocus method of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of an autofocus device according to Embodiment 1 of the present invention.
The automatic focusing apparatus shown in FIG. 1 includes a light source 101, a plate 102, a photographing unit 100, a camera controller 107, a memory controller 108, a memory 109, an index value calculation unit 120, and a focus control unit 122.
The light source 101 irradiates the plate 102 with light.

  The bottom of the plate 102 is made of a colorless and transparent material such as glass or plastic. In this embodiment, since the CCD camera 105 is disposed below the plate 102, the image data photographed by the CCD camera 105 is transmitted light of the observation target on the plate 102.

  The photographing means 100 photographs transmitted light by irradiating light onto the observation target on the plate 102 from the light source 101, and includes an objective lens unit 103 that performs zooming and focusing, and the objective lens unit 103. The position of the condenser lens 104 that collects the transmitted light, the CCD camera 105 that captures the transmitted light generated when the light source 101 irradiates the observation target on the plate 102, and the objective lens unit 103 are moved. The focus motor 106 is provided.

The camera controller 107 controls the CCD camera 105.
The memory controller 108 controls the memory 109.
The memory 109 stores image data taken by the CCD camera 105.

  The index value calculation means 120 calculates an index value representing the focus information of the observation object from the image data. The index value calculation means 120 includes a background color calculation means 110 for obtaining background color information from the image data, a threshold value calculation means 111 for obtaining a threshold value of the image data from the background color information, and the image data as the threshold value. Clip means 112 for clipping processing, a high-pass filter 113 for extracting a high-frequency component of the image data from the output signal of the clip means 112, and a calculation means 121 for calculating an index value. The background color calculation unit 110 includes a histogram generation unit that generates a histogram of the image data, and outputs an image intensity corresponding to the maximum value of the histogram as background color information. The arithmetic means 121 includes a rectifying means 114 that rectifies the output signal of the high-pass filter 113, and an integrating means 115 that obtains an index value by performing an integral arithmetic process on the output signal of the rectifying means 114. The integration calculation by the integration means 115 means that an average value for all the pixels of one image is obtained from the output signal of the rectification means 114 and used as an index value. In addition, the index value increases as the focus is adjusted.

  The focus control unit 122 controls the focus of the photographing unit 100 so as to obtain the optimum focus position of the observation target based on the index value obtained by the index value calculation unit 120. The focus control unit 122 determines which position is most focused based on the index value obtained by the index value calculation unit 120, and moves to determine the movement amount and movement direction of the objective lens unit 103. An amount / movement direction determining means 116 and a mechanical controller 117 for controlling the focus motor 106 based on the output of the movement amount / movement direction determining means 116 are provided.

  An example of the operation of the autofocus method realized with the above configuration is shown below. Here, the range for searching the focal position is set to 100 μm, and the fineness (step) of the search is set to 10 μm in advance. Further, the observation target placed on the plate 102 has a predetermined size and is larger than noise mixed in the image data.

  At the start of the automatic focus operation, first, the position of the objective lens unit 103 is moved downward by 50 μm corresponding to half of the value of the set focus position search range. Then, the light source 101 is turned on, and light is irradiated to the plate 102 on which the observation target is placed. The light irradiated on the plate 102 is transmitted and is multiplied by the objective lens unit 103. The transmitted light that has passed through the objective lens unit 103 passes through the condenser lens 104 and forms an image on the CCD element of the CCD camera 105. The image (image) connected to the CCD element of the CCD camera 105 is stored as image data in the memory 109 via the camera controller 107 and the memory controller 108, and the index value A is calculated later from the image data stored in the memory 109. To do. An index value calculation method will be described later.

  When the calculated index value A is input, the moving amount / moving direction determining means 116 calculates the moving amount value corresponding to the preset step 10 μm and the moving direction value corresponding to the upward direction. The mechanical controller 117 outputs a signal indicating the amount and direction of movement to the focus motor 106 to move the objective lens unit 103 to a predetermined position. The upward direction refers to the direction in which the objective lens unit 103 is brought closer to the plate 102, and the downward direction refers to the direction in which the objective lens unit 103 is moved away from the plate 102.

  Thereafter, the position of the moved objective lens unit 103 is further moved upward by 10 μm, and photographing is performed with the CCD camera 105. The index value B is obtained from the photographed image in the same manner as described above. Is calculated. This is repeated in order to calculate the index values C, D, and E. Here, the number of times of photographing by the CCD camera 105 is 11 because the focus position search range is 100 μm and the search is set in advance every step 10 μm.

  When the photographing of 11 times by the CCD camera 105 is completed, the moving amount / moving direction determining means 116 has the position of the objective lens unit 103 corresponding to the largest index value among the index values corresponding to the 11 times as the focal point. And outputs a signal indicating the amount and direction of movement to the mechanical controller 117 so that the objective lens unit 103 is moved to that position. The mechanical controller 117 moves the objective lens unit 103 to a predetermined position. Move to the position and end the autofocus operation.

Hereinafter, the calculation of the index value by the index value calculation means 120 will be described in detail with reference to FIG.
First, an image photographed by the CCD camera 105 is stored in the memory 109 as image data via the camera controller 107 and the memory controller 108. For example, when the photographed image is as shown in FIG. 2A, the image shown in FIG. 2A has a place where dust is darker than the background in addition to the observation target. is there. The intensity of the image data on the scanning line at this time is as shown in FIG. 2B, and when the dust is sufficiently smaller than the observation target, the transmitted light of the dust is influenced by the sneak light and the transmitted light of the observation target. As a result, the difference in intensity level appears between the observation object and the dust. Therefore, it is possible to reduce the influence of dust by using this difference in intensity level.

The background color calculation means 110 obtains the background color from the image data as follows.
First, a histogram of an image photographed by the CCD camera 105 is generated, and an image intensity value at which the histogram indicates a maximum value is set as a background color. This is because the background color in the image data occupies a larger area than the observation target, dust, etc., and the number of pixels is maximized. Referring to FIG. 3, for example, when the histogram of the image is as shown in FIG. 3 (a), this histogram shows the dust component shown in FIG. 3 (b) and the histogram shown in FIG. 3 (c). It can be considered as a synthesis result of the observed component to be shown and the background component shown in FIG. That is, since the background has the largest number of pixels in the image, the image intensity at which the histogram of the image shows the maximum value can be determined as the background color.

  The background color obtained in this way is input to the threshold value calculation means 111. Since the dust component smaller than the observation target appears brighter than the observation target due to the influence of the wraparound light, the threshold value calculation unit 111 sets an arbitrary ratio n to the background color based on the background color obtained from the histogram. The applied value is used as a threshold value. A specific calculation method of the threshold ratio n to the background color will be described later.

  The clip unit 112 performs clip processing using the threshold value obtained from the threshold value calculation unit 111 and removes the shaded portion in FIG. 2C, that is, restricts the intensity of the image data using the threshold value. Thereby, referring to FIG. 3 (b), it can be seen that the dust component corresponding to the portion whose intensity is higher than the threshold value can be greatly reduced.

  The output of the clip means 112 is input to the high-pass filter 113, and the high frequency component of the image data is emphasized, as shown in FIG.

  The rectifying means 114 constituting the calculation means 121 takes the absolute value of the output signal of the high pass filter 113. The image data output from the rectifying means 114 is as shown in FIG. In this way, the component emphasized by the high-pass filter 113 can be further enhanced, and the calculation accuracy can be further improved. Here, as the rectifying method by the rectifying means 114, a method of taking the absolute value of the output signal of the high-pass filter 113 is adopted, but a method of squaring the output signal of the high-pass filter 113 and outputting it is adopted. Also good.

  The output signal of the rectifying unit 114 is input to the integrating unit 115 and subjected to integration calculation processing to obtain an index value.

  The index value obtained as described above can reduce the possibility that the dust will be focused because the influence of the dust is effectively reduced.

Next, a threshold value setting method for reducing the influence of dust will be described in more detail.
As described above, the dust component can be deleted as the threshold ratio n with respect to the background color is reduced. On the other hand, if the threshold ratio n is too small, the component to be observed is largely removed, and an appropriate value is obtained. There is a possibility that the focal position cannot be obtained. Accordingly, it is important to determine how much the component to be observed should be removed to determine whether the performance deteriorates, to reduce the threshold as much as possible to remove dust components, and to obtain the threshold ratio n that does not deteriorate the performance. .

Hereinafter, a method for obtaining the threshold ratio n with respect to the background color will be specifically described.
First, the performance of variation allowed for autofocus is determined.
Here, the observation target is a spherical object having a diameter of 10 μm. Further, since the focal position is shifted by about 80 μm due to the distortion of the plate 102, the range of 100 μm is set as the search range for the automatic focus alignment. It should be noted that an appropriate focal point is when the focal point is within 3 μm from the center of the spherical observation target.

  Place a fresh observation target on a new plate 102, set the threshold ratio n to the background color, for example, to 200%, that is, set the threshold value to a value twice the background color so that dust does not enter, For example, automatic focusing is performed 100 times, and the variation in the focal position is measured. The ratio n of the threshold value with respect to the background color is 200% is a setting in which clipping processing based on the threshold value is hardly performed. Since automatic focusing is performed in a state where dust is not mixed in the observation target, there is no shift of the focal position due to the influence of dust, and variation in the focal position is minimized even if clip processing is not performed. It is possible to obtain an appropriate focal position by suppressing to about 0 μm.

  Next, the ratio n of the threshold value with respect to the background color is set to 100%, and the automatic focusing is repeated 100 times to obtain the variation in the focal position. Similarly, the threshold value ratio n is changed to 90%, 80%, 70%, 60%, and 50%, and the variation of the focal position at each ratio is obtained. If the variation in the focal position exceeds 3 μm and the focusing error occurs when the ratio n is set to a certain value or less, it is determined that the component to be observed has been reduced too much by the threshold value. For example, when the ratio is set to 40%, if the variation in focus position after autofocus becomes 3.2 μm, it is determined that the performance is not satisfied, and the threshold ratio n is set to 50% by taking a margin. decide. The threshold ratio n to the background color determined in this way is set to reduce the influence of dust as much as possible while maintaining the performance.

Next, an experiment is performed to confirm whether the determined ratio is appropriate.
The experiment is started after the plate 102 containing the observation object is left in a dusty space for several days, for example, for two days so that the dust enters the plate 102. First, the threshold ratio n is set to 200%, and automatic clipping is performed 100 times when clipping is not performed, and it is confirmed whether or not an error occurs due to focusing on dust. If the occurrence of an error cannot be confirmed, the plate 102 is left for a long period of time to naturally mix dust, or the expected dust is artificially mixed into the plate 102 to prevent the occurrence of focusing error. You may wake up.

  When the occurrence of an error can be confirmed, the threshold ratio n is set to 50%, which is the above-determined ratio, and automatic focusing is performed 100 times, and an appropriate focus can be obtained without focusing on dust. Make sure. In this way, it is possible to experimentally determine the ratio of the threshold that reduces the autofocus error due to dust while satisfying the given performance. This ratio only needs to be obtained once unless the observation object and the CCD camera 105 are changed.

  Next, the effect of the clip process by the clip unit 112 will be described with reference to FIGS. FIG. 5 shows an example of a graph representing a change in index value with respect to a change in focus position when the restriction by the clip unit 112 is applied and when the restriction is not applied.

  When the limitation by the clip unit 112 is not applied, as shown in FIG. 5A, both the index value P1a at the position where the dust is in focus and the index value P2a at the position where the observation target is focused are high, There will be no difference. Accordingly, there is a possibility that the focus control unit 122 at the subsequent stage erroneously performs focus control using the index value P1a to focus on dust.

  On the other hand, when the restriction by the clip unit 112 is applied, as shown in FIG. 5B, the index value P1b at the position where the dust is in focus does not show a large value. Accurate focus control using the value P2b can be performed, and it is possible to prevent the dust from being in focus.

  Furthermore, it demonstrates using FIG. FIG. 6 shows the change in the focal position corresponding to the change in the distance between the objective lens unit and the plate. FIG. 6A shows the position where the position of the objective lens 103a constituting the objective lens unit 103 is P1. 6B shows a state where the dust is in focus, and FIG. 6B shows that the position of the objective lens 103a constituting the objective lens unit 103 is at the position P2, and the observation target is in focus. Indicates the state.

  As shown in FIG. 6A, when the position of the objective lens 103a is at the position P1, the added amount of the high-frequency component of the dust that is in focus and the high-frequency component of the observation target that is not in focus is It becomes an index value at the position P1. This index value corresponds to P1a in FIG. 5A when clip processing is not performed, and corresponds to P1b in FIG. 5B when clip processing is performed.

  On the other hand, as shown in FIG. 6B, when the position of the objective lens 103a is at the position P2, the added amount of the high-frequency component of the dust that is not in focus and the high-frequency component of the observation object that is in focus. Becomes the index value at the position P2. This index value corresponds to P2a in FIG. 5A when clip processing is not performed, and corresponds to P2b in FIG. 5B when clip processing is performed.

  As described above, if the clipping process is performed, focusing can be performed at an optimum position without being affected by dust.

  In such an autofocus device according to the first embodiment, an index value calculation unit 120 that obtains a threshold value from the background color of captured image data, performs clipping processing using the threshold value, and calculates an index value from the clipped image data. And a focus control means 122 that automatically controls the focus of the photographing means 100 based on the index value, so that the observation object and dust are discriminated, and even if the observation object and dust are mixed, It is possible to prevent the dust from being inadvertently focused and accurately focus on the observation target.

  In the first embodiment, the background color calculation unit 110 includes a histogram generation unit that generates a histogram of the image data, and outputs an image intensity corresponding to the maximum value of the generated histogram as background color information. As described above, the background color may be obtained as follows.

  For example, the background color calculation unit 110 includes a maximum value calculation unit that uses the maximum value of the image intensities of all pixels of the image data as background color information. In this case, a pixel having a large image intensity is determined as the background, and the background color of the image data can be obtained based on the determination result. This is because the background is a result of photographing light that does not pass through the observation target or dust, and the background appears brighter because it does not pass through the observation target or dust. However, if the background color of the image data is judged with only one point as the maximum value, the intensity of the background color may be erroneously obtained due to the influence of noise such as a pixel defect of the CCD element. If the background color is judged using a large value (N is an arbitrary value) or a value obtained by averaging N image intensities from the largest value to the Nth largest value, the CCD is determined. It is possible to prevent erroneous detection of the intensity of the background color due to dark current noise of the element or the like.

  The background color calculation means 110 includes average value calculation means that uses the average value of image intensities of all pixels of the image data as background color information. In this case, as described above, when the background occupies more pixels than the observation target or dust, the average value of the image intensity of all the pixels can be obtained as the background color. However, when there are a lot of observation objects and dust, it must be considered that the average value is smaller (darker) than when the observation is not. As a result, erroneous detection due to uneven intensity of the background color can be prevented.

  In addition, the background color calculation unit 110 includes a region-specific histogram generation unit that divides an image into a plurality of regions and creates a histogram in each region. For example, as shown in FIG. 4A, the image is divided into 15 areas A1 to A5, B1 to B5, and C1 to C5, and a histogram in each area is generated. Then, the image intensity corresponding to the maximum value of the histogram of each area is obtained as the background color of each area. Specifically, when the histograms of the regions A1, A2, and B3 are as shown in (b) to (d) of FIG. 4, the intensities I1 to I3 that are the maximum values of the histograms of the regions are set to the respective regions. By setting the background colors of A1, A2, and B3, it is possible to deal with uneven background colors. When the light source 101 lacks luminance uniformity in the field of view on the plate 102, the brightness of the background color is different in the field of view. Since a normal light source has a high luminance at the center of the optical axis and decreases as it moves away from the center, assuming that the center of the optical axis and the center of the visual field are adjusted to the same position, the luminance at the center of the visual field Is bright and the brightness at the edge of the field appears dark. Therefore, if the image is divided into a plurality of areas and the background color information is obtained for each area, the surface of the background color corresponding to the visual field position can be obtained appropriately.

  Further, the background color calculation means 110 includes an area-specific maximum value calculation means for dividing the image into a plurality of areas as shown in FIG. 4A and obtaining the maximum value of the image intensity in each area. . In this case, since the maximum value of the image intensity of each region can be obtained as background color information of each region, an appropriate background color surface can be obtained without being affected by unevenness of the background color. In addition, if the smallest image intensity value is output as background color information of the entire image data among the plurality of image intensity maximum values obtained by the region-specific maximum value calculating means, the background color becomes more uneven. Unaffected background color information can be obtained.

  Further, the background color calculation means 110 includes an average value calculation means for each area for dividing the image into a plurality of areas as shown in FIG. 4A and obtaining an average value of the image intensity in each area. . In this case, since the average value of the image intensity in each region can be obtained as background color information of each region, an appropriate background color surface can be obtained without being affected by the unevenness of the background color at each visual field position.

  Note that the automatic focusing apparatus of the first embodiment is all effective for apparatuses that perform automatic focusing using transmitted light, such as a microscope and a microfilm scanner.

(Embodiment 2)
FIG. 7 is a diagram showing a configuration of an autofocus device according to Embodiment 2 of the present invention. In addition, in the figure, the same code | symbol is attached | subjected about the component same as FIG. 1, and the description is abbreviate | omitted.

  In addition to the configuration of the autofocus device of the first embodiment, the autofocus device of the second embodiment further includes a selection unit 201, an autofocus (hereinafter abbreviated as AF) controller 202, and a parameter setting unit 203. It is a thing. In the second embodiment, it is assumed that the focus control unit 122 has a two-stage focus control mode of fine adjustment and coarse adjustment.

  The selection unit 201 selects the output of the clipping unit 112, that is, the clipped image data when the focus control unit 122 performs fine adjustment, and the memory controller when the focus control unit 122 performs coarse adjustment. The output of 108, that is, image data that has not been clipped is selected and output.

  The AF controller 202 transmits the moving direction and moving amount of the focal position to the moving amount / moving direction determining unit 116 based on the set parameters, and controls the selecting unit 201.

  The parameter setting unit 203 sets a search range and a step from the outside.

Hereinafter, the automatic focusing method according to the second embodiment will be described with reference to FIG.
FIG. 8 shows the relationship between the index value and the focus position when the objective lens position is away from the observation target to some extent. FIG. 8A shows a case where there is dust and clip processing is not performed. b) shows a case where there is dust and clip processing is performed. In FIG. 8, P1c and P1d indicate index values at positions where the dust is in focus, and P2c and P2d indicate index values at positions where the observation target is in focus.

  First, looking at the transition of the index value when the clip processing is not performed and when the clip processing is performed, the transition of the index value in the range of Range-A shown in FIG. However, the index value in the range of Range-A ′ shown in FIG. 8B remains almost zero. This indicates that when the clip process is performed, the timing at which the observation target is not captured when the focus position is shifted from the observation target is earlier.

  In general, when viewing an object in focus with a lens, the range of the in-focus point that can be clearly captured is called the depth of focus, and in the range where the focus position deviates from this depth of focus, the observation target is It will be blurred. For example, when a silhouette is observed, it can be seen that if the silhouette is clearly visible, the silhouette appears dark (dark), but if the focus deviates from the depth of focus, the silhouette appears thin (bright). Therefore, when the focus position deviates from the depth of focus and the silhouette of the observation target becomes lighter, the timing at which the observation target is not captured is earlier in the case where the clip process is performed than in the case where the clip process is not performed.

  In addition, when clip processing is performed, even if only the index values in the range of Range-A ′ shown in FIG. 8B are viewed, there is no difference in the values, and in which direction the index value peaks. I don't know, and I don't know if there is an optimal focus position. As a result, the in-focus position cannot be determined accurately. However, in the case where the clipping process is not performed, if the index value in the range of Range-A shown in FIG. It can be estimated that it exists. Therefore, if a position close to the observation target is searched from a wide range, more information can be obtained without clipping, and the vicinity of the optimum focus position that is the peak of the index value can be quickly found.

  From the above, autofocus processing is divided into two stages of coarse adjustment and fine adjustment, and clip processing is not performed in coarse adjustment, but clip processing is performed at the time of fine adjustment. The focal position can be found.

  The autofocus method of the second embodiment will be specifically described. Here, in the case of coarse adjustment, the focus position is moved every 10 μm within a range of ± 100 μm from the current focus position, the index value at each focus position is calculated, and moved to the vicinity of the observation target. In the case of fine adjustment, the focus position is moved every 1 μm within the range of ± 10 μm from the focus position moved by executing coarse adjustment, the index value at each focus position is calculated, and the optimum focus position I will move to. The focus control unit 122 performs fine adjustment after performing coarse adjustment.

  First, at the start of the autofocus operation, the search range and step are set in the parameter setting means 203. The AF controller 202 transmits the movement direction and movement amount of the focal position to the movement amount / movement direction determining means 116 based on the set parameters.

  Next, the objective lens unit 103 is moved downward by 100 μm corresponding to half of the search range where the coarse adjustment is set, via the mechanical controller 117 and the focus motor 106. Then, the light source 101 is turned on, and an image at that position is taken by the CCD camera 105. The captured image is stored as image data in the memory 109 through the camera controller 107 and the memory controller 108.

  The background color of the image data stored in the memory 109 is calculated by the background color calculation means 110. The threshold value corresponding to the background color is calculated from the calculated background color by the threshold value calculation unit 111. The threshold value is input to the clipping unit 112, and the image data is limited by the threshold value.

  In the second embodiment, since fine adjustment is performed after coarse adjustment, focus control in the case of performing coarse adjustment will be described first.

  In the case of coarse adjustment, image data that has not been clipped is selected by the selection means 201, and this image data is input to the integration means 115 via the high-pass filter 113 and rectification means 114, and the index value is calculated. . The moving amount / moving direction determining means 116 stores the index value and outputs information on the moving amount and moving direction to the mechanical controller 117 so that the objective lens unit 103 is further moved by one step. Here, it is assumed that information indicating that the moving amount is 10 μm and the moving direction is upward is output, and the mechanical controller 117 outputs it to the focus motor 106 based on the information on the moving amount and the moving direction. A signal for execution is output, and the objective lens unit 103 is moved by the focus motor 106. The index value is stored by repeating such operations, and when all the index values in the set search range are calculated, the movement amount / movement direction determining means 116 finally moves the objective lens unit 103 to where. Decide what you want to do.

  The index value obtained as described above gradually increases after starting the autofocus operation, reaches a peak at an appropriate in-focus position, and decreases after that. However, if the index value continues to increase until the last shooting, that is, until the autofocus operation is finished, the movement amount / movement direction determining means 116 determines that an error has occurred and performs the autofocus operation. Then, the position of the objective lens unit 103 is shifted upward by, for example, 150 μm, and the autofocus operation is executed again. Here, since the index value is increasing, it is understood that there is no position where the observation target is focused in the searched range, but there is a high probability that there is a position where the observation target is focused in the upward direction. It is. On the contrary, if the index value continues to decrease to the end, there is a high probability that the position where the observation target is focused is in the downward direction. Further, if it increases halfway and then decreases, the focal position corresponding to the largest index value is in the vicinity of the position where the observation object is focused.

  When the vicinity of the focal position of the observation target can be recognized by the coarse adjustment as described above, the objective lens unit 103 is moved to the vicinity of the focal position, and fine adjustment is started.

  In the case of fine adjustment, image data after clip processing is selected by the selection unit 201, and automatic focusing is performed using the method described in the first embodiment.

  In the second embodiment, in addition to the configuration of the autofocus device of the first embodiment, the selection unit 201 that selects either the output of the clip unit 112 or the output of the memory controller 108, and the selection unit 201 described above. And an AF controller 202 for controlling the focus control means 122 and a parameter setting means 203. In the automatic focus operation in the case of using transmitted light, the focus position is close to the focus position of the observation target by rough adjustment without clip processing. Since the automatic focusing for obtaining the focal position of the observation target is performed by fine adjustment for performing the clip process after the adjustment, the automatic focusing operation on the observation target can be performed quickly and accurately.

  In the second embodiment, the case where the autofocus operation is performed in two stages of coarse adjustment and fine adjustment has been described. However, automatic adjustment is performed in three stages of coarse adjustment, normal adjustment, and fine adjustment, or more stages. A focus operation may be performed. In the case of coarse adjustment, a method of calculating with image data that does not perform clip processing by the clip unit 112 is used. In the case of fine adjustment, the search range is narrower than in the case of the normal adjustment, and the steps are set in the normal adjustment. More finely set than the case, and a method of calculating with the image data clipped by the clip unit 112 is used.

  In the second embodiment, the autofocus operation performed by setting the search range and step has been described. However, a so-called hill climbing method may be used, and the present invention is not limited to this embodiment.

  The automatic focusing apparatus according to the second embodiment is effective for all apparatuses that perform automatic focusing using transmitted light, such as a microscope and a microfilm scanner.

  An autofocus device and an autofocus method according to the present invention include an autofocus unit that accurately adjusts a focus position on an observation target when dust and the like are mixed, and an observation that requires autofocus such as a microscope. Useful for equipment.

It is a figure which shows the structure of the autofocus apparatus by Embodiment 1 of this invention. FIGS. 2A and 2B are diagrams for explaining how to obtain an index value in the automatic focusing apparatus according to the first embodiment. FIG. 2A shows an example of a photographed image, and FIG. 2A shows the intensity of the image data on the scanning line, FIG. 2C shows the intensity of the image data after the clipping process, FIG. 2D shows the intensity of the image data after the high-pass filter process, FIG. 2E shows the intensity of the image data after the rectification process. FIGS. 3A and 3B are diagrams for explaining a background color calculation method in the autofocus device according to the first embodiment. FIG. 3A illustrates an example of a histogram of a photographed image, and FIG. 3 (a) shows the dust components included in the histogram, FIG. 3 (c) shows the components to be observed included in the histogram of FIG. 3 (a), and FIG. 3 (d) shows FIG. ) Shows background components included in the histogram. FIG. 4 is a diagram for explaining a background color calculation method for each area in the autofocus device according to the first embodiment, and FIG. 4A illustrates an example when a captured image is divided into a plurality of areas. 4B shows a histogram in the region A1, FIG. 4C shows a histogram in the region A2, and FIG. 4D shows a histogram in the region B3. FIG. 5A is a diagram for explaining an autofocus method in the autofocus device of the first embodiment, and FIG. 5A shows a relationship between an index value and a focus position when clip processing is not performed. (B) shows the relationship between the index value and the focus position when clip processing is performed. FIG. 6A shows an example of a focus position in the autofocus device of the first embodiment, FIG. 6A shows an example when the dust is in focus, and FIG. 6B shows an observation target. Shows an example when the focus is on. It is a figure which shows the structure of the autofocus apparatus by Embodiment 2 of this invention. FIG. 8A is a diagram for explaining an autofocus method in the autofocus device according to the second exemplary embodiment of the present invention, and FIG. 8A shows a relationship between an index value and a focus position when clip processing is not performed; FIG. 8B shows the relationship between the index value and the focal position when clip processing is performed. It is a figure which shows the structure of the conventional autofocus apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image | photographing means 101 Light source 102 Plate 103 Objective lens unit 104 Condensing lens 105 CCD camera 106 Focus motor 107 Camera controller 108 Memory controller 109 Memory 110 Background color calculating means 111 Threshold value calculating means 112 Clipping means 113 High pass filter 114 Rectifying means 115 Integration means 116 Movement amount / movement direction determination means 117 Mechanical controller 120 Index value calculation means 121 Calculation means 122 Focus control means 201 Selection means 202 AF controller 203 Parameter setting means 901 Light source 902 Film 903 Lens unit 904 Image sensor 905 A / D conversion 906 Calculation unit 907 Control unit 908 Range designation means 909 Stepping motor 910 Sensor drive unit

Claims (15)

A light source for irradiating the observation object with light;
Photographing means for photographing transmitted light generated by irradiating the observation target with light from the light source, and outputting the image data;
Index value calculating means for obtaining background color information from the image data output from the photographing means, and calculating an index value representing the focus information of the observation object based on the background color information;
A focus control means for controlling the focus of the photographing means so as to obtain an optimum focus position of the observation object based on the index value;
An autofocus device characterized by that. The autofocus device according to claim 1,
The index value calculation means includes:
Background color calculation means for obtaining the background color information from the image data;
Threshold value calculating means for obtaining a threshold value of the image data from the background color information;
Clip means for clipping the image data at the threshold value;
A high-pass filter that extracts a high-frequency component of the image data from the output signal of the clip means;
Calculating means for obtaining the index value from the high-pass filter output signal,
An autofocus device characterized by that. The autofocus device according to claim 1,
The index value calculation means includes:
Background color calculation means for obtaining the background color information from the image data;
Threshold value calculating means for obtaining a threshold value of the image data from the background color information;
Clip means for clipping the image data at the threshold value;
Selection means for selecting and outputting either the image data or the image data clipped by the clipping means;
A high pass filter for extracting a high frequency component of the image data from the output signal of the selection means;
Calculating means for obtaining the index value from the high-pass filter output signal,
An autofocus device characterized by that. The autofocus device according to claim 3,
The focus control means has at least two stages of focus control modes of coarse adjustment and fine adjustment.
The selection means is:
Selecting the image data when the focus control means performs coarse adjustment, and selecting the image data clipped by the clip means when the focus control means performs fine adjustment;
An autofocus device characterized by that. The autofocus device according to claim 3,
The focus control means performs the fine adjustment after the coarse adjustment.
An autofocus device characterized by that. The autofocus device according to claim 2 or 3,
The background color calculation means is
A histogram generation means for generating a histogram of the image data;
The image intensity value corresponding to the maximum value of the histogram is output as background color information.
An autofocus device characterized by that. The autofocus device according to claim 2 or 3,
The background color calculation means is
A maximum value calculating means for obtaining a maximum value of the image intensity of the image data;
The maximum value of the image intensity obtained by the maximum value calculating means is output as background color information.
An autofocus device characterized by that. The autofocus device according to claim 2 or 3,
The background color calculation means is
An average value calculating means for obtaining an average value of the image intensities of the image data;
The average value of the image intensity obtained by the average value calculating means is output as background color information.
An autofocus device characterized by that. The autofocus device according to claim 2 or 3,
The background color calculation means is
The image data is divided into a plurality of regions, and a histogram generation unit for each region that creates a histogram of each region is provided.
The image intensity value corresponding to the maximum value of the histogram of each area is output as background color information of each area.
An autofocus device characterized by that. The autofocus device according to claim 2 or 3,
The background color calculation means is
The image data is divided into a plurality of regions, and a region-specific maximum value calculation means for obtaining a maximum value of image intensity in each region is provided,
The maximum value of the image intensity of each area obtained by the maximum value calculation means for each area is output as background color information of each area.
An autofocus device characterized by that. The autofocus device according to claim 10, wherein
The background color calculation means is
Among the maximum values of the plurality of image intensities obtained by the region maximum value calculating means, the smallest image intensity value is output as background color information.
An autofocus device characterized by that. The autofocus device according to claim 2 or 3,
The background color calculation means is
The image data is divided into a plurality of regions, and each region has an average value calculation means for calculating an average value of image intensity in each region,
The average value of the image intensity in each area obtained by the average value calculation means for each area is output as background color information for each area.
An autofocus device characterized by that. The autofocus device according to any one of claims 1 to 10,
The observation object has a predetermined size and is larger than noise mixed in the image data.
An autofocus device characterized by that. An automatic focusing method for photographing transmitted light generated by irradiating light to an observation target using an image sensor, and focusing the image sensor from image data obtained from the photographed image,
A background color information calculation step for calculating background color information from the image data;
A threshold value calculating step for calculating a threshold value of the image data from the background color information;
A clip processing step for clipping the image data with the threshold value;
A high frequency component extracting step for extracting a high frequency component of the clipped image data;
An index value calculating step for calculating an index value representing the focus information of the observation target from the extracted high frequency component;
A focus control step for controlling the focus of the image sensor so as to obtain an optimum focus position of the observation target based on the index value,
An autofocus method characterized by that. An automatic focusing method for photographing transmitted light generated by irradiating light to an observation target using an image sensor, and focusing the image sensor from image data obtained from the photographed image,
A background color information calculation step for calculating background color information from the image data;
A threshold value calculating step for calculating a threshold value of the image data from the background color information;
A clip processing step for clipping the image data with the threshold value;
A high frequency component extracting step for extracting a high frequency component of the image data or the data after the clip processing;
When coarsely adjusting the focus of the image sensor, the high-frequency component extracted from the image data is selected. When finely adjusting the focus of the image sensor, the high-frequency component extracted from the image data after the clip processing is selected and selected. An index value calculating step for calculating an index value representing the focus information of the observation target from the high-frequency component,
A focus control step for controlling the focus of the image sensor so as to obtain an optimum focus position of the observation target based on the index value,
An autofocus method characterized by that.

Images