JP2005538368A - Dimensional calibration method and system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a size calibration method and system for supplying a reliable value for a plurality of different playback modes of a digital camera in a short time, which enables measurement of a test object without error.
In a method for calibrating a size of an electronically generated image to be examined, which is generated by a downstream digital camera operable in a plurality of different playback modes, first a designated playback mode of the digital camera (3) is provided. , A reference calibration value (21c, 21d) indicating the ratio of the test object size to the image size is determined and stored with the designated playback mode (21b), and then for the calibration, the correction for the playback mode A factor is derived by comparing the stored playback mode (21b) with the actual used playback mode (16) of the digital camera (3), and the correction factor and the stored reference An actual calibration value is calculated from the calibration values (21c, 21d).

Description

  The present invention relates to a method for calibrating the size of an electronically generated image of a test object generated by an optical device having a downstream (back-end) digital camera operable in different playback modes. Furthermore, the present invention is a system for calibrating a size of an electronically generated image of a test object, and is arranged downstream of the optical apparatus for imaging the test object and the optical apparatus. And a digital camera for generating the image configured to have a plurality of different reproduction modes, and a calibration means configured to correlate the test object dimension with the selected image dimension. About. The invention further relates to a computer program and a computer program product for performing the method of the invention in a computing unit.

  In order to measure the structure of the imaged test object, the dimensions of the problem area of the test object are associated with the selected image area and are indicated or displayed. In a conventional dimensional calibration process, for example, in the case of a digital image, the length (width or horizontal dimension) and height (vertical dimension) of a (single) pixel are associated with the length and height of the corresponding region to be examined. . For the measurement of the structure to be examined, the latter (area to be examined) is selected (area or position specified), the number of associated pixels is specified, and the dimensions of the surface to be examined are based on calibration values Is required. This method is used inter alia for the measurement of microscopic structures. In this regard, for example, in the case of a microscope, the test object size corresponding to one pixel is stored in the form of a reference table, for example, for each optical magnification. For example, the pixel size (for example, in the horizontal direction) is 1 μm at an optical magnification of 10 ×, 0.5 μm at a magnification of 20 ×, 0.25 μm at a magnification of 40 ×, etc. in the subject space. If the horizontal pixel size is different from the vertical pixel size, the table entries need to be increased accordingly. Then, for (one) image calibration, the corresponding list item depends on the selected image acquisition condition (usually a specific optical magnification) in order to obtain the relevant pixel size or actual calibration value. Selected.

  There are several known methods for obtaining appropriate calibration values in optical devices having different selectable magnifications.

  In one such method (hereinafter referred to as “list method”), a micrometer level test object, for example a grating having a specific grating spacing, is incorporated into an optical device, the optical magnification of which is Known. Such a micrometer level test object is imaged and a corresponding image is displayed, for example, on a computer monitor. A distance (e.g. in the horizontal direction) is then selected on the micrometer-level image of the object to be examined and the number of pixels within the distance is determined. A calibration value is then obtained for the selected or specified optical magnification of the optical device from the ratio of the actual length of distance (known to the micrometer level test subject) to the number of pixels. Is done.

  Unlike the mathematical method described below, in the list method, an associated calibration value is then (typically possible) for each possible (possible) setting (value) of the optical device. Calculated for each optical magnification and stored in a list or look-up table. In contrast, the mathematical method corrects the stored calibration value based on the ratio between the magnifications (ratio between the stored reference magnification and the actual magnification used) for a specific optical magnification. The stored calibration values are also used for images acquired using different optical magnifications.

  Downstream of the optical device is often a digital camera that further processes, records, and / or transmits the image from the optical device to a computer (where the image is displayed to the user on the monitor). For example, the applicant's digital camera “DC 100” has a normal reproduction mode (765 × 581 pixels) and an interpolated reproduction mode (1146 × 871 pixels), and the digital camera “DC 100”. 350 F ″ has a standard playback mode of 1300 × 1030 pixels and a binning mode of 650 × 515 pixels. The above dimensional calibration method can only be used in an error-free manner if the digital camera is operated in the very playback mode in which calibration is performed. If the process is switched to another mode, the number of pixels per image area (area) will change, so the previous calibration value may cause inaccurate results for the measurement, so the dimension calibration must be performed again .

  Thus, typically a list with calibration values for all possible camera playback modes is generated and saved. Since there can be many playback modes (eg standard, binning, interpolation, multi-shot, etc.), this method is a long list, especially when each (realizable) possible magnification of the optical device needs to be additionally considered. (Multiple) will be used. Generation of such a list (reference table)-and the access time to the table items during measurement of the subject to be examined--requires a great deal of time, and an inappropriate camera mode is selected from the list. There is even the danger of end.

  Therefore, an object of the present invention is to provide a region to be examined (imaged) generated in an image display unit by a downstream (backward) digital camera (of the optical device) that uses a plurality of reproduction modes different from the optical device. It is to provide a dimension calibration method that enables multiple) dimension measurement, which is a reliability for different playback modes of a digital camera that allows error-free measurement of a subject to be measured. The purpose is to supply a high value in a short time. A further object (object) of the present invention is to provide a corresponding system for dimensional calibration and a computer program (product) for dimensional calibration.

  In order to solve the above problems, the method of the present invention first obtains a reference calibration value indicating a ratio of a (known) test object size to a corresponding image size for a specified reproduction mode and specifies the specified value. For the dimensional calibration, a correction factor for the playback mode is derived by comparing the stored playback mode with the playback mode that is actually used. An actual calibration value is calculated from the correction factor and the stored reference calibration value.

  According to the invention, it is sufficient to calibrate the camera system for (arbitrary) (one) specified playback mode. This playback mode used must be stored in the list. When the dimension measurement is performed during processing (or operation), the actual (current) calibration value is calculated from the stored value. By comparing the actual playback mode against the stored playback mode, a correction factor is derived, and an actual (current) calibration value is obtained from the correction factor and the stored reference calibration value.

  The actual playback mode of the (digital) camera can be entered manually or determined automatically. In the case of automatic determination, it is possible to inquire about the camera playback mode in which the software related to dimensional calibration is actually used, or the digital camera transmits the actual playback mode to the related software. To do.

  The present invention can be used for a single magnification setting of an optical device, but is also suitable for use with a plurality of different selectable optical magnification settings. Note that the terms “magnification setting” or “magnification factor (plurality)” of the optical device represent a plurality of different settings of the optical device. However, since these different settings usually affect the magnification of the optical apparatus, the following description will be limited to this case.

  In one embodiment of the invention, (one) corresponding reference calibration value is determined and stored for each of the magnification factors of the optical device, thereby (invention) combined with the above list method. When the magnification setting of the optical device changes, reference calibration values belonging to the associated magnification factor are identified in the stored list and a query of the stored playback mode of the camera is also performed. Then, as described above, by comparing the stored playback mode with the playback mode actually used, a correction factor for the playback mode is derived, and from the correction factor and the stored reference calibration value, the actual A calibration value is calculated.

  In a further advantageous embodiment of the invention, a (one) reference calibration value is determined and stored with the specified magnification factor for the (arbitrary) (one) specified magnification factor of the optical device. Thus, the present invention is combined with the mathematical methods described above. Thus, according to the present invention, a list item will have three variables: a specified playback mode, a specified magnification factor, and a corresponding reference calibration value. The actual dimensional calibration is then performed by comparing the actually used magnification factor with the stored magnification factor and deriving a (one) correction factor for the stored reference calibration value for the magnification factor. Is done. Then, a correction factor for the playback mode is derived by comparing the camera playback mode actually used with the stored playback mode. From the two derived correction factors and the stored reference calibration value, the actual calibration value is calculated.

  The reference calibration value associates a known subject dimension with an image dimension on the image display unit. It is convenient to represent the image dimensions in pixels. If the horizontal pixel size is different from the vertical pixel size, a distinction must be made between these two directions. In this case, different reference calibration values for the horizontal and vertical directions can be determined and stored, or the stored reference calibration values for one direction can be used to calculate the corresponding reference calibration values for the other direction. It is possible to ask.

  The correction factor used for the reference calibration value for the playback mode is the number of pixels supplied by the digital camera in the specified and stored playback mode within the predetermined image area and the playback actually used. Conveniently the ratio to the number of pixels in the mode. In this case, the actual calibration value can be calculated by simply multiplying the reference calibration value by the correction factor. Similarly, the correction factor for the magnification factor of the optical device can be expressed as the ratio between the stored magnification factor and the magnification factor actually used. In this case, the actual calibration value can be easily calculated by multiplying the stored reference calibration value by the correction factor for the playback mode and the correction factor for the magnification factor.

  As described above, the camera mode can be manually entered or automatically determined for the actual dimensional calibration being performed. The same applies to the magnification factor actually used in the optical device.

  A size calibration system for an electronically generated image of an object to be examined has an optical device for imaging the object to be examined and an image arranged downstream of the optical device (post-positioned) and having different reproduction modes. A digital camera for generating an image, and possibly further a display system in this connection (for example a computer with a display monitor for further storage and processing of the image), and an object measurement And calibration means for associating the selected image dimensions. Conventional calibration means are calibrated with known test object dimensions and then associates the corresponding test object dimensions with the selected image dimensions. In accordance with the present invention, the dimensional calibration system stores in advance (precedently) a reference calibration value indicating a ratio of a test object size and an image size in a designated playback mode of the camera, and is further associated with the reference calibration value. A storage unit is also provided for storing the playback mode. The system further comprises a calculation unit for calculating the actual calibration value from the calibration value stored by the correction factor for the playback mode. This correction factor is derived from a comparison between the actually used playback mode and the stored playback mode. These storage units and calculation units thus make it possible to carry out the method of the invention for dimensional calibration.

  If the optical device of the system of the present invention is operable with different magnification factors, the storage unit will pre-determine (several) reference calibration values for each possible (possible) magnification factor of the optical device. Conveniently configured to store).

  Also in this case, the storage unit can be configured to store in advance (preceding) the first reference calibration value for the specified magnification factor of the optical device and to store the magnification factor. , And the calculation unit can be configured to calculate a correction factor for the magnification factor, the correction factor being determined by comparing the actual magnification factor with the stored magnification factor, and the actual In addition to the correction factor for the playback mode, it is taken into account as a further correction factor when calculating the calibration value.

  The optical device can be configured as a microscope or a macroscope, among other things, having an adjustable optical magnification (eg, having a magnification converter such as a zoom optical system).

  The system of the present invention transmits the playback mode and / or the magnification factor actually used to the calculation unit, or makes an inquiry (inquiry) by the calculation unit regarding the playback mode and / or the magnification factor actually used. Conveniently having means to enable.

  The method of the invention can usually be performed by a computer program executed in a suitable computing unit. In the simplest case, the necessary calculation can be limited to the division / multiplication calculation process. Conveniently, the computer program is executed on the computing unit of the system of the invention. The computer program can be stored in a CD-ROM, a flexible disk, a hard disk drive or the like in addition to an appropriate data recording medium such as an EEPROM or a flash memory. The computer program accesses the stored data, i.e. the stored playback mode and the corresponding stored reference calibration value, determines (confirms) the actual playback mode of the camera, and then from them Calculate the calibration value. As mentioned above, the computer program can additionally take into account different magnification factors of the optical device.

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

  FIG. 1A is a schematic diagram of a size calibration system for an image region (plurality) of an electronically generated image (in this example, displayed on the monitor 2 of the computer 4) of a test object. The system further comprises an optical device for imaging the object to be examined, in this example a microscope 1 and a digital camera 3 downstream (that is, arranged downstream of the optical device). The camera 3 transmits individual images (plurality) or image sequences (plurality) to the computer 4. The computer 4 temporarily stores the individual images or image sequences for display on the monitor 2. The computer 4 can be used in the usual manner for image storage and / or processing. The illustrated system can display and measure the structure of a test object that can only be detected using a microscope.

  FIG.1 (b) shows the example of the image analysis by a dimension measurement. For this purpose, in this example, a scale (scale) 13 indicating a dimensional relationship with respect to the test object space, that is, the test object itself is superimposed on the images 11 and 12 by superimposition. For real-time dimension measurement, the structure to be measured to be measured is often selected (positioned or region-specific marking) by means of a pointing device (mouse) and then the result of the dimension measurement is displayed. The images 11 and 12 are respectively associated with the original images 8 and 9, and the original images 8 and 9 are obtained in different playback modes of the camera 3, respectively. For example, image 8 is acquired in the 764 × 581 pixel playback mode, and image 9 is acquired in the 1146 × 871 pixel playback mode. In order to be able to carry out the measurement without errors, the calibration values need to be adapted according to the playback mode of the (digital) camera 3. This can be clearly seen from the change in the dimensions of the scale 13 in this example.

  In the example of FIG. 1, the (digital) camera 3 has two different playback modes and the microscope has different optical magnification settings (10 ×, 20 ×, 40 ×, 50 ×, 100 ×, etc.). Conventionally, for each of the magnification factors and for each of the (digital) camera 3 playback modes, a corresponding (one) calibration value (or scaling factor) has to be obtained from the table 10. The calibration value (s) typically image (imaging) a micrometer level test object having a known dimension (s), and then an image corresponding to the (single) known object (test object) dimensions. Obtained by associating dimensions. Thus, this calibration procedure must be performed for each of the playback modes and for each of the optical magnifications, but this is time consuming and labor intensive. Furthermore, for image analysis, a large table 10 must be searched to obtain an accurate calibration value / scaling factor. This method is time consuming and may result in access to inappropriate table items.

  FIG. 2 shows an example of the system of the present invention for dimensional calibration and image analysis, where like reference numerals refer to like system elements. The computer 4 of the system of the present invention includes a reference calibration value 21c that represents the ratio of the test object size and the image size in the designated playback mode (camera mode) 21b of the camera 3 and its unit 21d (see FIG. 2B). .)) In advance (previous) and for storing the associated playback mode 21b. This storage can be achieved in the form of the table 21 shown in FIG. The system of the present invention further comprises a calculation unit for calculating the actual calibration values from the stored reference calibration values 21c, 21d.

  The camera 3 used in the embodiment shown in FIG. 2 has a plurality of different playback modes (camera modes) 21 b named “standard”, “interpolation” and “binning” in the table 21. The microscope 1 used is configured to be operable with a plurality of different optical magnification settings (values) as described in the column 21 a of the table 21. The storage unit of the system of the present invention stores corresponding reference calibration values 21c, 21d in the form of table 21 (as elements of table 21) for the specified playback mode 21b and specified magnification factor 21a. Configured. The first step (calibration) of the calibration method of the present invention can be performed in a conventional manner, for example, by a micrometer level test subject having a (single) known dimension. However, according to the present invention, the playback mode (camera mode) 21b of the (digital) camera 3 is also acquired and stored. For this purpose, the (digital) camera 3 supplies a playback mode (camera mode) 16 corresponding to the digital image 15, while the microscope 1 supplies a magnification factor 17 as information. In the case of square (ie, height and width equal) pixels, the sector to be examined having a known dimension is then selected (position or area designation mark) on the digital image 15 and the digital camera's The number of associated pixels is read (detected) and the corresponding reference calibration value is calculated. This value calculated in step 18 indicates, for example, a dimension in the object space corresponding to the width / height of one pixel. The result of step 18 is the table 21 shown. In this embodiment, the (one) reference calibration value is further divided (classified) into a numerical value 21c and an associated unit 21d, but listed for each magnification factor 21a and one designated camera playback mode 21b. Has been.

  Next, a dimension measurement procedure when performing image analysis processing will be described with reference to FIG.

  In order to perform this process, the digital camera 3 also supplies information related to the actual playback mode (camera mode) 16 in addition to the digital image 15. The microscope 1 supplies information regarding the actual (optical) magnification factor 17. These information elements can be actively transmitted to the computing unit of the system or queried by the computing unit. In step 22, the corresponding row (or line) in the table 21 containing the associated magnification factor 21a is selected based on the information regarding the optical magnification. In step 23, the stored playback mode 21b of the camera 3 is queried (inquired) and compared with the playback mode actually used by the camera 3. At the same time, the stored reference calibration values 21 c (dimension information) and 21 d (units) are read from the relevant row of the table 21. By comparing the stored playback mode (camera mode) 21b with the playback mode (camera mode) 16 that is actually used, a correction factor is calculated and a correct actual calibration value is obtained from the correction factor. .

  The calculation factor is easily calculated for the specified image area by determining the ratio of the number of pixels in the stored playback mode (camera mode) 21b to the number of pixels in the playback mode 16 actually used. The The stored reference calibration values 21c, 21d are then multiplied by this correction factor to generate the actual calibration value.

  Next, in order to measure the dimensions of the structure to be examined, a specific area is selected on the screen 2 (position or area designation marking), and the dimension of the selected area is determined using the calibration values already obtained. Calculated and displayed as needed (step 24). As shown in FIG. 1B, the scales 13 can be overlapped (incident incident) in parallel (alongside) or additionally.

  The present invention enables error-free dimension measurement when image acquisition (generation) is performed using a digital camera having a plurality of different playback modes. Since the need for storage can be kept to a minimum, processing of the data to be stored and accessing the stored data requires little time. At the same time, the reliability of image analysis is improved.

(A) A schematic diagram of an example of a system for image acquisition and for dimensional calibration and image analysis. (B) A procedure for measuring the structure to be examined according to the prior art. (A) Schematic diagram of an example of a system for image acquisition and dimensional calibration and image analysis of the present invention. (B) The first step of an example of the method of the invention for dimensional calibration. Second step of an example of the method (dimension calibration procedure) of the present invention for image analysis and dimension measurement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical apparatus / microscope 2 Monitor 3 Digital camera 4 Computer 8 Image produced | generated by 1st camera playback mode 9 Image produced | generated by 2nd camera playback mode 10 Table which has calibration value (plurality) 11 After dimension calibration Image 8
12 Image 9 after dimensional calibration
13 Scale (Scale)
15 Digital image 16 Actual playback mode (camera mode)
17 Microscope magnification factor (optical magnification)
18 Reference variable (plurality) determination step 21 Table 21a Microscope stored magnification factor (optical magnification)
21b Camera stored playback mode (camera mode)
21c Reference calibration value (numeric variable)
21d Unit of reference calibration value 22 Step to select from reference list 23 Step to calculate actual calibration value 24 Image dimension calibration step

Claims (16)

In a method for calibrating the size of an electronically generated image of a subject to be produced, produced by a downstream digital camera operable in different playback modes
First, for the designated playback mode of the digital camera (3), reference calibration values (21c, 21d) indicating the ratio of the test object size to the image size are obtained and together with the designated playback mode (21b). Stored and then for size calibration, a correction factor for the playback mode is derived by comparing the stored playback mode (21b) with the actual used playback mode (16) of the digital camera (3). And an actual calibration value is calculated from the correction factor and the stored reference calibration values (21c, 21d),
A dimension calibration method characterized by the above. Using an optical device (1) operable with different magnification factors,
2. A method according to claim 1, characterized in that for each magnification factor of the optical device, a corresponding reference calibration value is determined and stored. Using an optical device (1) operable with different magnification factors,
For the specified magnification factor of the optical device, a reference calibration value (21c, 21d) is determined and stored with the specified magnification factor (21a), and then the actually used magnification factor (17) and 2. The dimensional calibration according to claim 1, wherein a correction factor is derived for the reference calibration values (21 c, 21 d) for the magnification factor by comparing with the stored magnification factor (21 a). Method. 4. The size calibration method according to claim 1, wherein the number of pixels of the digital camera (3) in one direction such as horizontal or vertical direction is used as the image size. . The ratio between the number of pixels in the designated and stored playback mode (21b) and the number of pixels in the playback mode (16) actually used within a preset image area is a reference for the playback mode. The dimensional calibration method according to claim 4, wherein the dimensional calibration method is used as a correction factor for a calibration value. A dimensional calibration method according to any one of claims 1 to 5, wherein a microscope or a macroscope is used as the optical device (1). 7. The camera mode (16) actually used for dimensional calibration is entered manually or determined automatically, according to any one of claims 1-6. Dimension calibration method. The method according to claim 1, wherein the magnification factor (17) that is actually used is manually entered or automatically determined. A system for calibrating a size of an electronically generated image of a test object, comprising:
An optical device for imaging the test object;
A digital camera for generating the image, arranged downstream of the optical device and configured to have a plurality of different reproduction modes;
A system configured to have a calibration means for associating a subject dimension with a selected image dimension;
Pre-stored reference calibration values (21c, 21d) indicating the ratio between the test object size and the image size in the playback mode (21b) specified in advance for the digital camera (3), and the associated A storage unit for storing the playback mode (21b), and a calculation unit for calculating the actual calibration values (21c, 21d) from the stored calibration values according to the correction factor for the playback mode (16) ,
A dimension calibration system, characterized in that the correction factor is derived from a comparison of the playback mode (16) actually used and the stored playback mode (21b). The optical device (1) is configured to be operable with a plurality of different magnification factors,
10. A dimensional calibration system according to claim 9, wherein the storage unit is configured to pre-store reference calibration value (s) for each possible magnification factor of the optical device. The optical device (1) is configured to be operable with a plurality of different magnification factors,
The storage unit is pre-stored with reference calibration values (21c, 21d) for the specified magnification factor (21a) of the optical device (1) and configured to store the magnification factor (21a); And the calculation unit is configured to calculate a correction factor for the magnification factor;
The correction factor is determined by comparing the actual magnification factor (17) and the stored magnification factor (21a) and is considered as a further correction factor in the calculation of the actual calibration value. The dimensional calibration system according to claim 9. The dimensional calibration system according to any one of claims 9 to 11, wherein the optical device (1) is a microscope or a macroscope. Transmits the actually used playback mode (16) of the digital camera (3) to the calculation unit or allows the calculation unit to query the playback mode (16) actually used The dimensional calibration system according to any one of claims 9 to 12, further comprising: means. Transmit the actually used magnification factor (17) of the optical device (1) to the calculation unit or allow the calculation unit to query the actually used magnification factor (17) The dimensional calibration system according to any one of claims 9 to 13, further comprising: means. A computer program having program code means,
Computer program adapted to carry out the method as defined in at least one of claims 1 to 8 when said computer program is executed in a computer or a corresponding computing unit, in particular a computing unit of the system of claim 9. . A computer program product having program code means stored in a computer readable data recording medium,
Computer configured to execute the method as defined in at least one of claims 1 to 8 when said computer program product is executed in a computer or a corresponding computing unit, in particular a computing unit of the system of claim 9. Program product.

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