JP6076205B2 - Image acquisition device and focus method of image acquisition device - Google Patents

Description

  The present invention relates to an image acquisition device and a focus method of the image acquisition device.

  As a conventional image acquisition apparatus, for example, there is an apparatus described in Patent Document 1. In this apparatus, light from a test object is divided by a half prism and received by a photoelectric conversion element formed of a two-dimensional imaging element such as a CCD area image sensor. The control circuit of the photoelectric conversion element has a scanning area setting unit that can arbitrarily set two scanning areas for two-dimensionally scanning the light receiving surface. Then, focusing control is executed based on the focusing error signal of the light received in the two scanning areas set by the scanning area setting unit.

JP-A-8-320430

  In the conventional apparatus described above, the light from the test object is divided using a half prism. For this reason, it is difficult to ensure the amount of light in the photoelectric conversion element, and the detection accuracy of the focal position of the sample may be reduced. Further, when the light amount of the focus position detection light is increased, the light amount of the imaging light of the test object is decreased, and it may be difficult to secure the light amount at the time of imaging.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an image acquisition apparatus that can secure a light amount during imaging and can accurately detect the focal position of a sample and a focusing method thereof. To do.

  In order to solve the above problems, an image acquisition apparatus according to the present invention includes a stage on which a sample is placed, a light source that irradiates light toward the sample, and an objective lens that is disposed so as to face the sample on the stage. , And a light guide optical system including a light branching unit that branches the optical image of the sample into a first optical path for image acquisition and a second optical path for focus control, and field drive for moving the field position of the objective lens with respect to the sample Means, a first imaging means for acquiring a first image based on the first optical image branched into the first optical path, and a second image based on the second optical image branched into the second optical path. The second imaging means to be acquired, the second image is analyzed, the focal point calculation means for calculating the focal point information of the sample based on the analysis result, and the operations of the visual field driving means and the second imaging means are controlled. And an operation control means that is disposed in the second optical path and An optical path difference generating member that generates an optical path difference in the second optical image along the in-plane direction of the image plane, and the second imaging means has a plurality of pixel rows and is capable of rolling readout. An image sensor is provided, and the operation control unit is configured to detect a predetermined part of the sample in the field of view of the objective lens by the field driving unit so that a light image of the predetermined part in the sample is exposed in each pixel row of the two-dimensional image sensor. It is preferable to synchronize the movement and the rolling readout of the two-dimensional image sensor.

In this image acquisition device, the optical path length difference of the second optical image can be formed without branching the light in the second optical path for focus control by arranging the optical path difference generating member. Therefore, the amount of light to the second optical path necessary for obtaining the focal position information can be suppressed, and the amount of light when the first imaging unit performs imaging can be ensured. Further, in this image acquisition device, a light image of a predetermined part (the same part) in the sample is exposed at each pixel line of the second imaging unit by using a delay in the reading timing of image data in each pixel line in rolling reading. As described above, the movement of the predetermined portion of the sample within the field of view of the objective lens and the rolling readout are synchronized. Since the optical path difference generating member is arranged in the second optical path, the image data from each pixel row includes contrast information equivalent to that when the focal position of the objective lens is changed in the same part of the sample. Therefore, the in-focus information can be calculated quickly and accurately based on the information.
Moreover, it is preferable that the optical path difference generating member has a plane inclined with respect to a plane orthogonal to the optical axis of the second optical path. Thereby, the optical path difference of the 2nd optical image by an optical path difference production | generation member can be formed suitably.

  Further, the focal point calculation means can calculate the focal point information of the sample based on the difference in contrast value of the image data read out by at least two pixel columns among the pixel columns of the two-dimensional image sensor. preferable. In this case, in the second imaging unit, an optical image focused on before the optical image incident on the first imaging unit (front pin) and an optical image focused on later (rear pin), respectively. You can get it. By using the difference between the contrast values of these image data, the focal point information of the sample can be calculated with high accuracy.

  Further, it is preferable that the focal point calculation means calculates the focal point information of the sample based on the distribution of contrast values of the image data read by each pixel column of the two-dimensional image sensor. In this case, the focal point information of the sample can be accurately calculated based on the contrast value distribution of the image data.

  Further, the focus method of the image acquisition apparatus according to the present invention includes a stage on which a sample is placed, a light source that irradiates light toward the sample, an objective lens that is disposed so as to face the sample on the stage, and A light guide optical system including a light branching unit that branches the optical image of the sample into a first optical path for image acquisition and a second optical path for focus control; and a field driving unit that moves the field position of the objective lens with respect to the sample. A first imaging means for acquiring a first image based on the first optical image branched into the first optical path, and a second image based on the second optical image branched into the second optical path. The second imaging means, the second image is analyzed, the focal point calculation means for calculating the focal point information of the sample based on the analysis result, and the operation for controlling the operations of the visual field driving means and the second imaging means And a focus method of an image acquisition device comprising: Thus, an optical path difference generating member that generates an optical path difference in the second optical image along the in-plane direction of the imaging surface of the second imaging unit is disposed in the second optical path, and a plurality of second imaging units are provided. Using a two-dimensional image sensor having a plurality of pixel columns and capable of rolling readout, and by means of visual field driving means so that a light image of a predetermined part of the sample is exposed to each pixel column of the two-dimensional image sensor by the operation control means. The movement of a predetermined part of the sample within the field of view of the objective lens is synchronized with the rolling readout of the two-dimensional image sensor.

  In this focusing method of the image acquisition device, the optical path length difference of the second optical image can be formed without splitting the light in the second optical path for focus control by arranging the optical path difference generating member. Therefore, the amount of light to the second optical path necessary for obtaining the focal position information can be suppressed, and the amount of light when the first imaging unit performs imaging can be ensured. Further, in this focusing method of the image acquisition apparatus, a delay in the readout timing of image data in each pixel column in rolling readout is used, and an optical image of a predetermined part (same part) in the sample is obtained in each pixel of the second imaging unit. The movement of a predetermined portion of the sample within the field of view of the objective lens and the rolling readout are synchronized so that the exposure is performed in a row. Since the optical path difference generating member is arranged in the second optical path, the image data from each pixel row includes contrast information equivalent to that when the focal position of the objective lens is changed in the same part of the sample. Therefore, the in-focus information can be calculated quickly and accurately based on the information.

  According to the present invention, it is possible to secure the amount of light at the time of imaging and to accurately detect the focal position of the sample.

It is a figure which shows one Embodiment of the macro image acquisition apparatus which comprises the image acquisition apparatus which concerns on this invention. It is a figure which shows one Embodiment of the micro image acquisition apparatus which comprises the image acquisition apparatus which concerns on this invention. It is a figure which shows an example of a 2nd imaging device. It is a figure which shows an example of the combination of an optical path difference production | generation member and a 2nd imaging device. It is a block diagram which shows the functional component of an image acquisition apparatus. It is a figure which shows an example of the scanning of the visual field of the objective lens with respect to a sample. It is a figure which shows the mode of the synchronization of the movement of the predetermined site | part of the sample within the visual field of an objective lens, and the rolling reading of a 2nd imaging device, (a) is the positional relationship of the visual field of an objective lens, and a division area, ( b) The predetermined part of the sample for each pixel column and the timing of exposure and readout of the image sensor are shown. It is a figure which shows the subsequent state of FIG. It is a figure which shows the subsequent state of FIG. It is a figure which shows the analysis result of the contrast value in case the distance to the surface of a sample corresponds with the focal distance of an objective lens. It is a figure which shows the analysis result of the contrast value in case the distance to the surface of a sample is longer than the focal distance of an objective lens. It is a figure which shows the analysis result of the contrast value in case the distance to the surface of a sample is shorter than the focal distance of an objective lens. It is a figure which shows an example of the contrast information processed with a focusing calculation part. 3 is a flowchart showing a focusing operation of the image acquisition apparatus shown in FIGS. 1 and 2. It is a figure which shows the modification of an optical path difference production | generation member. It is a figure which shows another modification of an optical path difference production | generation member. It is a figure which shows another modification of an optical path difference production | generation member.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an image acquisition device and a focus method of the image acquisition device according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of a macro image acquisition device constituting an image acquisition device according to the present invention. FIG. 2 is a diagram showing an embodiment of a micro image acquisition device constituting the image acquisition device according to the present invention. As shown in FIGS. 1 and 2, the image acquisition device M includes a macro image acquisition device M1 that acquires a macro image of the sample S and a micro image acquisition device M2 that acquires a micro image of the sample S. . The image acquisition device M sets, for example, a plurality of line-shaped divided regions 40 (see FIG. 6) with respect to the macro image acquired by the macro image acquisition device M1, and each divided region 40 is subjected to high magnification by the micro image acquisition device M2. It is a device that generates a virtual slide image that is a digital image by acquiring and synthesizing.

  As shown in FIG. 1, the macro image acquisition apparatus M1 includes a stage 1 on which a sample S is placed. The stage 1 is an XY stage that is driven in the horizontal direction by a motor or actuator such as a stepping motor (pulse motor) or a piezoelectric actuator. The sample S to be observed with the image acquisition device M is a biological sample such as a cell, for example, and is placed on the stage 1 in a state of being sealed with a slide glass. By driving the stage 1 in the XY plane, the imaging position with respect to the sample S can be moved.

  The stage 1 can reciprocate between the macro image acquisition device M1 and the micro image acquisition device M2, and has a function of transporting the sample S between both devices. In macro image acquisition, the entire image of the sample S may be acquired by one imaging, or the sample S may be divided into a plurality of regions and imaged. The stage 1 may be provided in both the macro image acquisition device M1 and the micro image acquisition device M2.

  A light source 2 that irradiates light toward the sample S and a condenser lens 3 that condenses the light from the light source 2 onto the sample S are disposed on the bottom side of the stage 1. The light source 2 may be arranged so as to irradiate light obliquely toward the sample S. A light guide optical system 4 that guides a light image from the sample S and an imaging device 5 that captures a light image of the sample S are disposed on the upper surface side of the stage 1. The light guide optical system 4 includes an imaging lens 6 that forms an optical image from the sample S on the imaging surface of the imaging device 5. The imaging device 5 is an area image sensor that can acquire a two-dimensional image, for example. The imaging device 5 acquires the entire image of the light image of the sample S incident on the imaging surface via the light guide optical system 4 and stores it in a virtual slide image storage unit 39 described later.

  As shown in FIG. 2, the micro image acquisition device M2 has a light source 12 and a condenser lens 13 similar to those of the macro image acquisition device M1 on the bottom surface side of the stage 1. A light guide optical system 14 that guides a light image from the sample S is disposed on the upper surface side of the stage 1. The optical system that irradiates the sample S with light from the light source 12 employs an excitation light irradiation optical system for irradiating the sample S with excitation light and a dark field illumination optical system for acquiring a dark field image of the sample S. May be.

  The light guide optical system 4 includes an objective lens 15 disposed so as to face the sample S, and a beam splitter (light branching means) 16 disposed at a subsequent stage of the objective lens 15. The objective lens 15 is provided with a motor or actuator such as a stepping motor (pulse motor) or a piezo actuator that drives the objective lens 15 in the Z direction orthogonal to the mounting surface of the stage 1. By changing the position of the objective lens 15 in the Z direction by these driving means, the focal position of the imaging in the image acquisition of the sample S can be adjusted. The focus position may be adjusted by changing the position of the stage 1 in the Z direction, or by changing the positions of both the objective lens 15 and the stage 1 in the Z direction.

  The beam splitter 16 is a part that branches the optical image of the sample S into a first optical path L1 for image acquisition and a second optical path L2 for focus control. The beam splitter 16 is disposed at an angle of about 45 degrees with respect to the optical axis from the light source 12. In FIG. 2, the optical path passing through the beam splitter 16 is the first optical path L1, and the beam splitter 16 The optical path reflected by 16 is the second optical path.

  In the first optical path L 1, an imaging lens 17 that forms an optical image (first optical image) of the sample S that has passed through the beam splitter 16, and an imaging surface is disposed at the imaging position of the imaging lens 17. A first imaging device (first imaging means) 18 is arranged. The first imaging device 18 is a device that can acquire a one-dimensional image (first image) based on a first light image of the sample S. For example, a two-dimensional CCD image sensor capable of TDI (Time Delay Integration) driving. Or a line sensor is used. Further, if the method of sequentially acquiring the image of the sample S while controlling the stage 1 at a constant speed, the first imaging device 18 can acquire a two-dimensional image such as a CMOS image sensor or a CCD image sensor. It may be a device. The first images picked up by the first image pickup device 18 are sequentially stored in a temporary storage memory such as a lane buffer, and then compressed and output to an image generation unit 38 to be described later.

  On the other hand, in the second optical path L2, a field adjustment lens 19 for reducing the optical image (second optical image) of the sample reflected by the beam splitter 16, a second imaging device (second imaging means) 20, and Is arranged. In addition, an optical path difference generation member 21 that causes an optical path difference in the second optical image is disposed in the front stage of the second imaging device 20. The field adjustment lens 19 is preferably configured so that the second light image is formed on the second imaging device 20 with the same size as the first light image.

  The second imaging device 20 is a device that can acquire a two-dimensional image (second image) based on the second optical image of the sample S. The second imaging device 20 has a two-dimensional imaging device that has a plurality of pixel columns and can perform rolling readout. An example of such a two-dimensional imaging device is a CMOS image sensor. The imaging surface 20a of the second imaging device 20 is disposed so as to substantially coincide with the XZ plane orthogonal to the second optical path L2. On the imaging surface 20a of the second imaging device 20, as shown in FIG. 3A, a plurality of pixel columns 20b in which a plurality of pixels are arranged in a direction perpendicular to the readout direction are arranged in the readout direction. .

  In the second imaging device 20, as shown in FIG. 3B, a reset signal, a readout start signal, and a readout end signal are output based on the drive cycle of the drive clock, so that each pixel column 20b is output. Exposure and readout are controlled. The exposure period of one pixel column 20b is a period from discharge of charge accompanying a reset signal to reading of charge accompanying a read start signal. In addition, the readout period of one pixel column 20b is a period from the start of charge readout accompanying the readout start signal to the end of charge readout accompanying the readout end signal. Note that a read start signal for the next pixel column can also be used as a read end signal.

  In rolling readout, readout start signals output for each pixel column 20b are sequentially output at a predetermined time difference. The reading speed in the rolling reading is controlled by the time interval of the reading start signal for reading each pixel column 20b. If the time interval of the read start signal is shortened, the read speed is increased, and if the time interval of the read start signal is increased, the read speed is decreased. The adjustment of the reading interval between the adjacent pixel columns 20b and 20b can be performed, for example, by adjusting the frequency of the driving clock, setting the delay period during the reading period, and changing the number of clocks that define the reading start signal.

  The optical path difference generating member 21 is a glass member that generates an optical path difference in the second optical image along the in-plane direction of the imaging surface 20a. In the example shown in FIG. 4A, the optical path difference generating member 21 has a prism shape with a right-angled triangular section, and is in the in-plane direction of the imaging surface 20a, that is, on the imaging surface 20a accompanying the scanning of the sample S. It arrange | positions so that thickness may increase continuously along the moving direction (Z direction) of a 2nd optical image. Further, the optical path difference generating member 21 is disposed so as to have a plane inclined with respect to a plane orthogonal to the optical axis of the second optical path L2. Therefore, the second optical image incident on the imaging surface 20a is directed from one end portion in the Z direction (upper end portion in FIG. 4B) to the other end portion (lower end portion in FIG. 4B) on the imaging surface 20a. The light path becomes longer. Moreover, it is preferable that the optical path difference generation member 21 is disposed so that the surface facing the second imaging device 20 is parallel to the imaging surface 20a of the second imaging device. Thereby, refraction of light by the surface facing the second imaging device 20 can be reduced, and the amount of light received by the second imaging device 20 can be ensured.

  FIG. 5 is a block diagram illustrating functional components of the image acquisition apparatus. As shown in the figure, the image acquisition apparatus M includes a computer system including a CPU, a memory, a communication interface, a storage unit such as a hard disk, an operation unit 31 such as a keyboard, a monitor 32, and the like. Further, the image acquisition apparatus M includes, as functional components of the control unit 33, a stage driving unit 34, an objective lens driving unit 35, an operation control unit 36, a focal point calculation unit 37, and an image generation unit 38. And a virtual slide image storage unit 39.

  The stage driving unit 34 is a part that functions as a visual field driving unit that moves the visual field position of the objective lens 15 with respect to the sample S. The stage drive unit 34 is configured by a motor or actuator such as a stepping motor (pulse motor) or a piezoelectric actuator, for example. The stage drive unit 34 moves the stage 2 in the XY directions with respect to a plane having a predetermined angle (for example, 90 degrees) with respect to a plane orthogonal to the optical axis of the objective lens 15 based on the control by the operation control unit 36. Thereby, the sample S fixed to the stage 2 moves with respect to the optical axis of the objective lens 15, and the visual field position of the objective lens 15 with respect to the sample S moves.

  More specifically, the stage driving unit 34 scans the stage 1 on which the sample S is placed at a predetermined speed based on the control by the operation control unit 36. The scanning of the stage 1 relatively sequentially moves the imaging field of the sample S in the first imaging device 18 and the second imaging device 20. In order to image the entire sample S, in the image acquisition apparatus M, the operation control unit 36 has the objective lens 15 for the sample S in the scanning direction along the imaging line Ln (n is a natural number) composed of a plurality of divided regions 40. Control to move the visual field position.

  As the movement of the visual field position of the objective lens 15 with respect to the sample S between the adjacent imaging lines Ln, for example, as shown in FIG. 6, a bidirectional scan in which the scanning direction is reversed between the adjacent imaging lines Ln is employed. Alternatively, the scanning direction may be a unidirectional scanning in which the imaging lines Ln are in the same direction. Note that a random scan in which the visual field position of the objective lens 15 is randomly moved between the divided regions 40 may be used.

  Further, although the scanning speed of the stage 1 during image acquisition is constant, there is actually a period in which the scanning speed is unstable due to the influence of vibration of the stage 1 immediately after the start of scanning. For this reason, each of the acceleration period in which the scanning width longer than that of the divided region 40 is set, the stage 1 is accelerated, the stabilization period until the scanning speed of the stage 1 is stabilized, and the deceleration period in which the stage 1 is decelerated is It is preferable that this occurs when scanning outside the divided area 40. Thereby, it is possible to acquire an image in accordance with a constant speed period in which the scanning speed of the stage 1 is constant. Note that imaging may be started during the stabilization period, and the data portion acquired during the stabilization period after image acquisition may be deleted. Such a method is suitable when using an imaging device that requires idle reading of data.

  Similar to the stage drive unit 34, the objective lens drive unit 35 is configured by a motor or actuator such as a stepping motor (pulse motor) or a piezoelectric actuator. The objective lens driving unit 35 moves the objective lens 15 in the Z direction along the optical axis of the objective lens 15 based on the control by the operation control unit 36. Thereby, the focal position of the objective lens 15 with respect to the sample S moves.

  The objective lens driving unit 35 does not drive the objective lens 15 during the analysis of the focal position by the in-focus calculation unit 37, and moves the objective lens 15 in the Z direction until the analysis of the next focal position is started. It is preferable to drive only along one direction. In this case, during the scanning of the sample S, the analysis period of the focal position and the objective lens driving period based on the analysis result occur alternately. By not changing the positional relationship between the objective lens 15 and the sample S during the analysis of the focal position, the analysis accuracy of the focal position can be ensured.

  The operation control unit 36 is a part that controls the operations of the second imaging device 20 and the stage driving unit 34. More specifically, the operation control unit 36 has a visual field V of the objective lens 15 by the stage driving unit 34 so that an optical image of a predetermined part in the sample S is exposed by each pixel row 20b of the second imaging device 20. The movement of the predetermined portion of the sample S in the inside and the rolling readout of the second imaging device 20 are synchronized.

  As shown in FIG. 7A, the operation control unit 36 moves the sample S within the visual field V of the objective lens 15 at a constant speed when the visual field V of the objective lens 15 moves in one divided region 40. The stage drive unit 34 is controlled so that Further, as illustrated in FIG. 7B, the operation control unit 36 moves the imaging Sb of the optical image of the sample S on the imaging surface 20 a of the second imaging device 20 and each pixel column on the imaging surface 20 a. The stage drive unit 34 and the second imaging device 20 are controlled so that the reading direction of 20b matches. When using an imaging device that can variably set the reading speed for rolling reading, the operation control unit 36 changes the reading speed for rolling reading based on the moving speed of the sample S within the field of view V of the objective lens 15. May be.

  The exposure time in each pixel row 20b is set based on at least the width of the predetermined portion Sa of the sample S in the scanning direction and the moving speed of the predetermined portion Sa of the sample S within the field of view V of the objective lens 15. More preferably, the magnifications of the objective lens 15 and the field adjustment lens 19 are also considered. Thereby, the optical image of the predetermined part Sa of the sample S can be exposed by each pixel row 20b.

  At time T1, as shown in FIG. 7B, the imaging Sb of light from the predetermined portion Sa of the sample S on the imaging surface 20a of the second imaging device 20 is the first pixel row 20b in the imaging region. Is reached, exposure of the first pixel row 20b is started. At time T2, as shown in FIG. 8A, the position of the predetermined portion Sa of the sample S within the field of view V of the objective lens 15 is moved. At this time, as shown in FIG. 8B, the image Sb of light from the predetermined portion Sa of the sample S reaches the second pixel row 20b in the imaging region, and the second pixel row 20b. The exposure is started. Further, at the timing when the image Sb of light from the predetermined portion Sa of the sample S passes through the first pixel row 20b, reading of the first pixel row 20b is started.

  Further, at time T3, as shown in FIG. 9A, the position of the predetermined portion Sa of the sample S in the field of view V of the objective lens 15 further moves in the scanning direction. At this time, as shown in FIG. 9B, the imaging Sb of the light from the predetermined portion Sa of the sample S reaches the third pixel row 20b of the imaging region, and the third pixel row 20b. The exposure is started. Further, reading of the second pixel row 20b is started at the timing when the image Sb of light from the predetermined portion Sa of the sample S passes through the second pixel row 20b. Furthermore, the reading of the first pixel column 20b is completed simultaneously with the reading of the second pixel column 20b.

  Thereafter, the movement of the predetermined portion Sa of the sample S within the field of view V of the objective lens 15 and the rolling readout in the pixel column 20b are performed in the same procedure until the predetermined number of pixel columns is reached. The image data read from each pixel row 20b is all image data for the same part of the sample S. Further, since the optical path difference generating member 21 is arranged in the second optical path L2, the image data read from each pixel row 20b is obtained when the focal position of the objective lens 15 is changed for the same part of the sample S, respectively. Contrast information equivalent to is included. The image data read by each pixel row 20b is sequentially output to the in-focus calculation unit 37.

  In addition, it is preferable that the 2nd imaging device 20 can switch the reading direction of rolling reading. In this way, even when the scanning direction of the visual field position of the objective lens 15 with respect to the sample S changes as in bidirectional scanning or random scanning, the moving direction of the imaging Sb of the light from the sample S and the second imaging device 20 The readout direction of each pixel column 20b can be easily matched.

  When the objective lens driving unit 35 can move the light guide optical system 14 including the objective lens 15 in the X and Y directions, the operation control unit 36 determines that the optical image of the predetermined part in the sample S is the second imaging device 20. The movement of a predetermined portion of the sample S within the field of view V of the objective lens 15 by the objective lens driving unit 35 and the rolling readout of the second imaging device 20 may be synchronized so that each pixel row 20b is exposed. . In this case, the objective lens driving unit 35 functions as a visual field driving unit that moves the visual field position of the objective lens 15 with respect to the sample S.

  The focal point calculation unit 37 is a part that analyzes the second image acquired by the second imaging device 20 and calculates the focal point information of the sample S based on the analysis result. As a calculation method of the in-focus information in the in-focus calculation unit 37, for example, a front pin / rear pin method or a contrast distribution method is adopted.

  When the front pin / rear pin method is used, the in-focus calculation unit 37 selects the pixel column 20b of at least two pixel columns 20b among the pixel columns 20b of the second imaging device 20. As described above, in the second optical path L2, the thickness continuously increases along the moving direction (Z direction) of the second optical image on the imaging surface 20a accompanying the scanning of the sample S. An optical path difference generating member 21 is disposed. Therefore, in the second imaging device 20, based on the positions of the two pixel columns 20b to be selected, an optical image focused on before the first optical image incident on the first imaging device 18 (front pin) ) And a focused optical image (rear pin) later. The focal point calculation unit 37. The difference between the contrast values of the image data read by the selected pixel row 20b is obtained.

  As shown in FIG. 10, when the focal position of the objective lens 15 is in alignment with the surface of the sample S, the image contrast value of the front pin and the image contrast value of the rear pin substantially coincide, and the difference between these values is Nearly zero. On the other hand, as shown in FIG. 11, when the distance to the surface of the sample S is longer than the focal length of the objective lens 15, the image contrast value of the rear pin becomes larger than the image contrast value of the front pin. The difference value is positive. In this case, the focal point calculation unit 37 outputs instruction information to the effect that the objective lens 15 is driven in a direction approaching the sample S to the objective lens driving unit 35. In addition, as shown in FIG. 12, when the distance to the surface of the sample S is shorter than the focal length of the objective lens 15, the image contrast value of the rear pin is smaller than the image contrast value of the front pin. The difference value is negative. In this case, the focal point calculation unit 37 outputs instruction information indicating that the objective lens 15 is driven in a direction away from the sample S to the objective lens driving unit 35.

  When the front pin / rear pin method is used, the in-focus calculation unit 37 has a pixel column 20b corresponding to the front pin and a pixel column corresponding to the rear pin so as to be symmetrical with respect to the pixel column 20b corresponding to the focus center. 20b is selected. The pixel row 20b corresponding to the focus center is a sample that passes through the second optical path L2 and the optical path difference generation member 21 with an optical path length that matches the optical path length of the optical image of the sample S imaged by the first imaging device 18. This refers to the pixel row 20b on which the S light image is incident. For example, when the pixel column 20b corresponding to the focus center is the kth pixel column 20b, the in-focus calculation unit 37, for example, the (k−m) th pixel column 20b and the (k + m) th pixel. Each of the columns 20b is selected. By setting m according to the degree of unevenness of the sample S, the accuracy of the in-focus information can be improved.

  When the contrast distribution method is used, the focal point calculation unit 37 acquires the contrast information of the image data from the plurality of pixel columns 20 b of the second imaging device 20. In the example illustrated in FIG. 13, the contrast value of the image data from the first pixel column 20 b to the n-th pixel column 20 b in the second imaging device 20 is illustrated, and the pixel in the i-th column. The contrast value of the image data in the column 20b is a peak value. In this case, the in-focus calculation unit 37 generates in-focus information assuming that the focus position of the objective lens 15 is the in-focus position when the predetermined portion Sa of the sample S is exposed in the i-th pixel row 20b. To do. The contrast value may be a contrast value in a specific pixel among the pixels included in each pixel column 20b, or an average value of contrast values of all or a part of the pixels included in each pixel column 20b. May be.

  The image generation unit 38 is a part that combines the acquired images to generate a virtual slide image. The image generation unit 38 sequentially receives the first image output from the first imaging device 18, that is, the image of each divided region 40, and synthesizes them to synthesize the entire image of the sample S. Then, an image having a lower resolution than this is created based on the composite image, and the high resolution image and the low resolution image are associated with each other and stored in the virtual slide image storage unit 39. In the virtual slide image storage unit 39, an image acquired by the macro image acquisition device M1 may be further associated. The virtual slide image may be stored as a single image, or may be stored as a plurality of divided images.

  Subsequently, a focusing operation in the above-described image acquisition apparatus M will be described.

  As shown in FIG. 14, in the image acquisition device M, when the stage drive unit 34 starts moving the stage 1, the field of view V of the objective lens 15 moves along one imaging line Ln (step S11). Further, the predetermined portion Sa of the sample S in the field of view V of the objective lens 15 is formed so that the image Sb of the light image from the predetermined portion Sa in the sample S is exposed in each pixel row 20b of the second imaging device 20. Is synchronized with the rolling readout of the second imaging device 20 (step S12). Then, the focal point information in the divided area 40 is calculated based on the contrast value of the image data acquired in each pixel row 20b (step S13), and the focal position of the objective lens 15 is adjusted based on the calculated focal point information. Then, the divided area 40 is imaged (step S14). Thereafter, it is determined whether or not the calculation of the focal point information has been completed for the desired imaging line Ln (step S15). If the acquisition of the focal point information has not been completed, the next imaging line Ln is determined. The field of view V of the objective lens 15 is moved (step S16), and the processes of steps S11 to S15 are repeatedly executed.

  As described above, in the image acquisition device M, the optical path length difference of the second optical image is formed by the arrangement of the optical path difference generating member 21 without branching the light in the second optical path L2 for focus control. it can. Therefore, the amount of light to the second optical path L2 necessary for obtaining the focal position information is suppressed, and the amount of light when the first imaging device 18 performs imaging can be secured. Further, in this image acquisition device M, a light image of a predetermined part (same part) in the sample S is used for each image of the second imaging device 20 by using the delay of the readout timing of the image data in each pixel row 20b in the rolling readout. The movement of the predetermined portion of the sample S within the field of view V of the objective lens 15 and the rolling readout are synchronized so that the pixel row 20b is exposed. Since the optical path difference generating member 21 is arranged in the second optical path L2, the image data from each pixel row 20b is equivalent to the case where the focal position of the objective lens 15 is changed in the same part of the sample S. Contrast information is included, and in-focus information can be calculated quickly and accurately based on the information.

  Further, in the image acquisition device M, the second imaging device 20 is configured by using a two-dimensional imaging device capable of rolling readout. Therefore, by arranging the optical path difference generating member 21 in the second optical path L2, It becomes unnecessary to drive the objective lens 15 when calculating the in-focus information of the objective lens 15. Therefore, the occurrence of vibration or the like during focus control can be suppressed.

  In the image acquisition device M, the sample is calculated based on the difference between the contrast values of the image data read by at least two pixel rows 20b among the pixel rows 20b of the second imaging device 20 by the focus calculation unit 37. S focus information is calculated. In this method, in the second imaging device 20, a light image focused on before the light image incident on the first imaging device 18 (front pin) and a light image focused on later (rear pin). And can be acquired respectively. By using the difference between the contrast values of these image data, the in-focus information of the sample S can be calculated with high accuracy. In the image acquisition device M, the focal point calculation unit 37 calculates the focal point information of the sample S based on the distribution of the contrast values of the image data read by each pixel row 20b of the second imaging device 20. Is done. In this method, the focal point information of the sample can be accurately calculated based on the distribution of contrast values of the image data.

  In the case where the focal point calculation unit 37 uses the front pin / rear pin method for calculating the focal point information of the sample S, the scanning of the visual field position of the objective lens 15 is bidirectional scanning (see FIG. 6). In place of the optical path difference generating member 21 shown in FIG. 4, as shown in FIG. 15, the thickness of the moving direction (Z direction) of the second optical image on the imaging surface 20a accompanying the scanning of the sample S is as follows. It is necessary to use an optical path difference generating member in which a continuously thick portion and a continuously thin portion are provided symmetrically.

  In the example shown in FIG. 15A, the optical path difference generating member 41A has a prism shape with a triangular cross section, and is arranged so that the top portion substantially coincides with the central portion in the Z direction of the imaging surface 20a. In this example, the second optical image incident on the imaging surface 20a has the longest optical path at the center portion in the Z direction on the imaging surface 20a, and the optical path becomes shorter toward both end portions in the Z direction on the imaging surface 20a. In the example shown in FIG. 15B, the optical path difference generation member 41B is configured by combining two glass members having a prism shape with a right-angled cross section, and each glass member is one half region in the Z direction on the imaging surface 20a. And the other half region, respectively. In this example, the optical path becomes the longest at the end in the Z direction on the imaging surface 20a, and the optical path becomes shorter from the end in the Z direction on the imaging surface 20a toward the center. In the example shown in FIG. 15C, the optical path difference generating member 41C has an isosceles trapezoidal cross section, and the inclined surface overlaps one end region and the other end region in the Z direction on the imaging surface 20a. Is arranged. In this example, the optical path length does not change in the center portion in the Z direction on the imaging surface 20a, and the optical path becomes shorter toward the both end portions in the Z direction only at the end portion in the Z direction.

  In the case where the focal point calculation unit 37 uses the front pin / rear pin method for calculating the focal point information of the sample S, the scanning of the visual field position of the objective lens 15 is a one-way scan, and the focal point calculation unit 37 performs the sample S When the contrast distribution method is used to calculate the in-focus information, the optical path difference generating members 21 and 31A to 31C can be used, and for example, the optical path difference generating member shown in FIG. 16 can be used.

  In the example shown in FIG. 16A, the optical path difference generation member 41D has a prism shape with a right-angled cross section, and is arranged so that the inclined surface overlaps only one half region in the Z direction on the imaging surface 20a. In this example, in the region where the optical path difference generation member 41D is arranged, the optical path becomes shorter toward the center portion in the Z direction. In the example shown in FIG. 16B, the optical path difference generating member 41E has a trapezoidal cross section and is disposed so that the inclined surface overlaps the entire imaging surface 20a. In this example, the optical path is uniformly shortened from one end side in the Z direction of the imaging surface 20a toward the other end side.

  In addition, in the optical path difference generating members 21 and 41A to 41E, the thickness continuously increases or decreases, but as shown in FIG. 17, a plurality of glass members having different dimensions in the Z direction are combined in order of dimensions, and the thickness is increased. You may use the optical path difference production | generation member 51 which changes in steps. Even when such an optical path difference generating member 51 is used, the same effect as that of the above-described embodiment can be obtained. In this case, the dimensional difference in the Z direction in each glass member is preferably an integer multiple of the dimension in the Z direction of each pixel column 20b in the second imaging device 20. In addition, it is preferable that the position of the edge portion in the Z direction of each glass member and the position of the edge portion in the Z direction of each pixel row 20b are matched.

  In the above-described embodiment, an apparatus for generating a virtual slide image has been exemplified. However, the image acquisition apparatus according to the present invention may be various as long as the apparatus acquires an image while scanning a sample at a predetermined speed with a stage or the like. It can be applied to the device.

  DESCRIPTION OF SYMBOLS 1 ... Stage, 12 ... Light source, 14 ... Light guide optical system, 15 ... Objective lens, 16 ... Beam splitter (light branching means), 18 ... 1st imaging device (1st imaging means), 20 ... 2nd Imaging device (second imaging means), 20a ... imaging surface, 20b ... pixel row, 21, 41A to 41E, 51 ... optical path difference generating member, 34 ... stage driving unit (field driving means), 36 ... operation control unit ( Operation control means), 37... In-focus calculation unit (in-focus calculation means), L1... First optical path, L2... Second optical path, M... Image acquisition apparatus, M1. Apparatus, S ... sample, Sa ... predetermined part, V ... field of objective lens.

Claims (5)

A stage on which the sample is placed;
A light source that emits light toward the sample;
An objective lens disposed so as to face the sample on the stage, and a light branching unit that branches the optical image of the sample into a first optical path for image acquisition and a second optical path for focus control. Optical optics,
Visual field driving means for moving the visual field position of the objective lens with respect to the sample;
First imaging means for acquiring a first image by a first optical image branched into the first optical path;
A second imaging means for acquiring a second image by a second optical image branched into the second optical path;
In-focus calculation means for analyzing the second image and calculating in-focus information of the sample based on the analysis result;
Operation control means for controlling operations of the visual field driving means and the second imaging means;
An optical path difference generating member disposed in the second optical path and causing an optical path difference in the second optical image along an in-plane direction of an imaging surface of the second imaging unit;
The second imaging means has a two-dimensional imaging device having a plurality of pixel rows and capable of rolling readout,
The operation control unit is configured to detect a predetermined region of the sample in the field of view of the objective lens by the visual field driving unit so that a light image of the predetermined region of the sample is exposed in each pixel row of the two-dimensional image sensor. An image acquisition apparatus characterized by synchronizing movement and rolling readout of the two-dimensional image sensor.   The image acquisition apparatus according to claim 1, wherein the optical path difference generation member has a plane that is inclined with respect to a plane orthogonal to the optical axis of the second optical path.   The in-focus calculation means calculates the in-focus information of the sample based on a difference between contrast values of image data read out by at least two pixel columns among the pixel columns of the two-dimensional image sensor. The image acquisition apparatus according to claim 1, wherein:   The in-focus calculation unit calculates the in-focus information of the sample based on a distribution of contrast values of image data read by each pixel column of the two-dimensional image sensor. 2. The image acquisition device according to 2. A stage on which the sample is placed;
A light source that emits light toward the sample;
An objective lens disposed so as to face the sample on the stage, and a light branching unit that branches the optical image of the sample into a first optical path for image acquisition and a second optical path for focus control. Optical optics,
Visual field driving means for moving the visual field position of the objective lens with respect to the sample;
First imaging means for acquiring a first image by a first optical image branched into the first optical path;
A second imaging means for acquiring a second image by a second optical image branched into the second optical path;
In-focus calculation means for analyzing the second image and calculating in-focus information of the sample based on the analysis result;
An operation control unit that controls operations of the visual field driving unit and the second imaging unit;
An optical path difference generating member that generates an optical path difference in the second optical image along the in-plane direction of the imaging surface of the second imaging means is disposed in the second optical path;
As the second imaging means, a two-dimensional imaging device having a plurality of pixel columns and capable of rolling readout is used.
The operation control means causes the visual field drive means to expose the predetermined portion of the sample within the field of the objective lens so that a light image of the predetermined portion of the sample is exposed in each pixel row of the two-dimensional imaging device. A focus method for an image acquisition apparatus, wherein movement and rolling readout of the two-dimensional image sensor are synchronized.

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