WO2000008507A2

WO2000008507A2 - Method and device for automatic focusing and illumination in image-recording systems

Info

Publication number: WO2000008507A2
Application number: PCT/DE1999/002386
Authority: WO
Inventors: Stephan Stach; Lutz MÜLLER
Original assignee: Tuhh-Technologie Gmbh
Priority date: 1998-08-05
Filing date: 1999-08-03
Publication date: 2000-02-17
Also published as: DE19835284A1; AU6325499A; WO2000008507A3; DE19981510D2; WO2000008507B1; DE19835284C2

Abstract

The invention relates to a device or a method for automatic focusing and illumination in image-recording camera systems, wherein an image-recording apparatus (2) for photographing objects (1) is used. The image-recording apparatus (2) can be moved in relation to the object (1) and images having different sharpness and brightness can be made by means of a focusing device and an illumination and/or lighting device (3). The data of the image-recording apparatus (2) are transmitted to a data processing system (18) which automatically regulates focusing and/or illumination for photographing the object (1). The amount of data (which is optionally compressed) processed by the data processing system (18) serves as correcting variable (11) for changing the automatic focusing and/or illumination or lighting of the object (1) to photograph said object (1).

Description

Description: Device and method for the automatic focusing and exposure of image recording systems

The present invention relates to a device and a method for automatic focusing and exposure of image recording systems according to the preambles of claims 1 and 11 and the use of the device and / or the method according to claim 14.

To record objects, there are electronic image recording systems that record static or dynamic objects and forward the corresponding image data to a display device or a data processing system that processes or stores the data. The known image recording systems consist of an image recording device, for example a "CCD camera" (charge coupled device) or a video camera with light-sensitive photo sensors, which record the corresponding object and forward analog or digital image signals to a data processing system.

This data processing system can have different structures. In the case of CCD cameras, for example, it is known to either store the corresponding digital data supplied by the light-sensitive photo sensors on a magnetic tape or a so-called "mini disk", or to process them directly using a computer. In order to be able to better manage the amount of data supplied by the photosensitive photo sensors, these are usually compressed before they are stored on a suitable data carrier in order to reduce the amount of data. The compressed data is then either decompressed to be displayed on a suitable display device or stored to be portable. In these conventional image recording systems, there are different possibilities both to adjust the focusing of the camera lens according to the distance between the camera and the object or to set the exposure time according to the existing lighting of the object to be recorded. So-called "auto-focus" cameras are known, for example, which adjust the sharpness of the recorded image by means of grayscale levels. The image is broken down row by row and column by column into so-called "pixels", each pixel corresponding to a specific gray value. The discrete delimitation of different gray value levels ("threshold") allows the different areas of the recorded object to be separated within the image in order to achieve a certain sharpness. This information is also suitable for automatic focusing of the lens by analyzing the corresponding gray value levels and adjusting the focus in such a way that the best selectivity and thus also the optimal focus can be set with a maximum gradient between the gray value levels.

In addition, conventional systems measure the optimal exposure time for recording the object, which depends on the existing lighting, using the above-mentioned. Grayscale levels, so that an optimal exposure time is set here with a certain gradient between the individual gray value areas or "pixels" of the image.

These known systems have the disadvantage that the storage of the different gray values, that is to say the image information of each “pixel” and the calculation of the individual gray value levels of the gradient and the corresponding dividing line between the individual gray value areas not only takes up a large storage space within the data processing system, but also the computation The optimum settings for automatic focusing and exposure time setting take a lot of time and require fast processors or large and expensive "cash" memories.

In addition, the known systems are complex and expensive and can only be implemented with increased "hardware" expenditure.

The present invention is therefore based on the object of improving the known systems for automatically adjusting the focus or exposure such that the data processing system is not only cheaper and less expensive to produce, but also has fewer components and faster results achieved. In addition, the focus and exposure time setting should be user-independent and the susceptibility to interference of the known image recording systems should be reduced.

The object is achieved according to the invention by the characterizing part of independent claims 1 and 11. Further advantageous refinements of the invention are described in the subclaims. Use of the device according to the invention and the method according to the invention is described in claim 14.

The present invention relates to an apparatus and a method for automatic focusing and exposure of image recording systems, with an image recording device which is movable relative to the object to be recorded and which by means of a focusing direction and an exposure and / or an illumination device have images of objects different sharpness and brightness. The image recording device supplies data to a data processing system and uses the data processing system Data for automatically adjusting the focus or the exposure for recording the object by the image recording device.

For this purpose, a manipulated variable is used to change the focus or the exposure for recording the object, this manipulated variable being determined by the amount of data that the data processing system processes.

The invention is based on the principle that the storage space required for the image data to be stored is greater, the sharper the image of the object is imaged on the photo sensors, and the storage space requirement is greater, the more the illuminance or the exposure. time approaches the optimum of the overall system (object, lenses, recording, transmission and conversion components).

By running through the entire available distance setting range between the object and the camera, i.e. the light-sensitive photo sensors or the focal length range of the lens at constant illuminance, the dependence of the storage space requirement of the image data to be stored on the sharpness set is determined. The image information created during the recording is first converted into digital information in order to then be compressed by an algorithm. This algorithm is designed in such a way that no image information is lost during the compression and the compression rate is variable, so that the storage space requirement of the image data to be stored changes when the parameter distance between the object and the camera or the focal length setting of the lens of the camera used, and when changing the illuminance of the object or the exposure time of the photo sensors also changes. The storage space requirement is therefore related to the maximum compression rate that can be achieved, which in turn depends on the sharpness or brightness of the image.

For example, when walking through the available illuminance range (or the exposure time range) with constant focus setting, the dependence of the storage space requirement on the illuminance (or the exposure duration) of the object is obtained. Both dependencies, that is, the dependency of the storage space requirement on the focal length setting or the distance between the object and the photo sensors and, on the other hand, when the illuminance or exposure time changes, are independent of one another and can therefore be viewed individually. That the storage space requirement of the compressed image information data is variable at the maximum possible compression rate is due to the fact that e.g. B. larger homogeneous areas of the same intensity value (that is, without details) can be summarized without the image losing its information content. Larger homogeneous areas are thus obtained with poorly adjusted sharpness, with many details and thus a low possible compression rate (= high storage space requirement) with well-adjusted sharpness. This means that there is a certain sharpness setting in which the file size after compression is maximum, i.e. the information content in the image is also maximum. If, on the other hand, the picture becomes blurred, picture details disappear, the information content decreases and with it the storage space requirement.

The manipulated variable for setting the focusing or the exposure of the distance or the lighting is the amount of compressed data, the size of the stored data File, the inverse compression rate, or a combination of these sizes. This manipulated variable is passed on to a controller, which then adjusts according to the distance between the image recording device and the object or the focal length of the lens of the image recording device, or accordingly also adjusts the exposure time of the image recording device or the illuminance of the lighting device that illuminates the object.

It is also possible to display the manipulated variable on a display so that the quality of the picture taken can then be determined. The maximum manipulated variable, for example the minimum compression rate, is thus a measure of the optimal setting of the image recording system.

This principle, that is to say the corresponding device or the corresponding method, can also be used in already existing image processing systems which are equipped with the system according to the invention in such a way that the generated image data in the sense of the principle according to the invention for automatic adjustment of the focusing and / or the exposure can be used to record the object by the image recording device.

A preferred embodiment is explained with reference to the drawings. Show:

Fig. 1 shows the basic structure of the invention

Systems; 2 shows the dependence of the storage space requirement on the distance between the object and the camera; 3 shows the dependence of the storage space requirement on the exposure time or the illuminance and Fig. 4 shows the dependence of the storage space requirement on the illuminance / exposure time and the distance / focal length.

Fig. 1 shows the basic structure of the invention

Contraption. An image recording device 2 is arranged above an object 1, the image recording device 2 being located within an adjustment device 17, which adjusts the distance d between the object 1 and the image recording device 2 by means of vertical movement, that is to say adjustment of the image recording device 2. The image recording device 2 has a specific recording cone 15 in order to record objects 1 of different sizes.

The image recording device 2 supplies image signals 9 to an image signal converter 4, which either converts analog signals into digital signals or forwards the digital image signals 9 directly. In addition, the image signal converter 4 is suitable for converting corresponding image signals 9 into digital signals 10, which can be compressed by a compression system 5. The compression system 5 compresses the digital signals 10 arriving from the image signal converter 4 and then forwards data 16 to a memory 6.

A controller 7, which converts manipulated variables 11 accordingly, serves for the automatic adjustment of the focusing or the exposure time. These manipulated variables 11 can be both the compression rate of the compression system and a size of the storage space requirement of the memory 6, that is to say for example the file size of the image file stored in the memory 6 (in KB).

The controller 7 either delivers the manipulated variable 11 directly to a display 8 or converts the manipulated variable 11 into a lighting exposure setting signal 12 or an exposure

/ Focus adjustment signal 13 µm, which are used for automatic focusing or exposure time or illumination.

The illumination setting signal 12 is forwarded to an illumination device 3, which illuminates the object 1 by means of a light cone 14. The exposure / sharpness setting signal 13 is forwarded to the adjusting device 17 or the image recording device 2 in order to either set the distance d between the image recording device 2 and the object 1 there or to control the corresponding exposure time or to adjust the focal length of the image recording device 2 accordingly adjust.

Adjustment device 17 with image recording device 2, image signal converter

4, compression system 5, memory 6 and controller 7 and the corresponding data lines are combined in the data processing system 18.

Fig. 2 shows the dependence of the distance between the

Image recording device 2 and the object 1, that is to say the distance d and the file size of the image file which is stored in the memory 6, which represents a measure of the corresponding storage space requirement. The file size is given on the Y axis in kB.

The values on the X axis correspond to the graduation marks on the focus wheel of the image recording device 2 and are shown here without a unit. The distance d of the exposure / lens system of the camera used in the adjusting device 17 to the object 1 is changed with the focus wheel. However, the focal length of the lens system (objective) can also be changed with a constant object distance d. Both types the focus setting is comparable and corresponds to the X axis in FIG. 2.

The storage space requirement of the compressed image information is plotted on the Y axis. In Fig. 2 11 pictures with different focus settings are made and stored compressed. Depending on the desired degree of optimization, however, more or fewer, for example 20 or 5, recordings are also possible. The file sizes in kB of the compressed image information (storage space required) are then plotted on the Y axis.

In Fig. 2 it can be seen that there is a certain sharpness setting at which the file size is maximum (here: approximately d = -6).

FIG. 3 shows a similar dependency of the storage space requirement as in FIG. 2 with constant sharpness adjustment between the variable exposure time of the photo sensor used or the chosen illuminance of the illuminating device 3. Thus, this system can be used simultaneously for the exposure duration or the illuminance optimally set the object independently of the user and system (regardless of the optical and electronic components used).

3, the degree of brightness of the recorded image is plotted on the X axis, while the Y axis, similar to FIG. 2, indicates the file size of the compressed and stored image data. It can also be seen here that the

The maximum file size is around x = 7. The optimal exposure time or the optimal illuminance can thus be determined from this. Fig. 4 shows the relationships between the illuminance / exposure time, the distance d, that is, the distance between the object 1 and the image recording device 2 or the focal length setting of the lens used in the image recording device 2 and the resulting file size of the stored image, which a Represents a measure of the storage space requirement (also here in kB).

Since the setting of the illuminance is independent of the setting of the sharpness or the setting of the exposure time from the setting of the distance b or vice versa, the storage space requirement can be associated with both parameters, it is possible to show these relationships in a three-dimensional diagram as illustrated in FIG. 4. In Fig. 4 it can be seen that there is a certain focus setting and an illuminance (exposure time) setting in which the storage space requirement and thus the information content of the recording is maximum or the compression rate is minimal.

The correct setting of the illuminance (or exposure time) and the sharpness can be found if the image information continuously runs through the compression algorithm during the actual image acquisition and the size of the compressed image file or the level of the compression rate or a corresponding auxiliary size is continuously displayed on the monitor or is used to set the corresponding components.

The method according to the invention first runs through the entire focus area and thus quickly finds the point of the maximum file size, based on the focus setting. Then move in the diagram of Fig. 4 on the focus curve at a constant illuminance and stop at the maximum. Then the algorithm or the method according to the invention traverses the entire illuminance range by changing the exposure time or the illuminance of the illuminating device 3 or the aperture of the lens and thus quickly finds the maximum in relation to the corresponding file size. The process looks for the illuminance curve with a constant focus setting or vice versa. The maximum (peak) of the "storage space requirement mountain" can thus be determined from any position.

A corresponding compression algorithm is contained in a programmable electronic circuit. The digital image information of the photo sensors is compressed by the compression algorithm and the compressed image information (or the identical image information) plus further information regarding the compression rate of the file size or a corresponding auxiliary size is then used to automatically optimize the sharpness as well as the illuminance or the exposure time adjust.

In addition, the method and the device according to the invention can be used in an image processing system by equipping it with the above-mentioned programmable electronic circuit and permanently compressing the image information with the algorithm and making the corresponding manipulated variable 11 (compression rate, storage space requirement or auxiliary variable) available becomes. As a result, the required sharpness as well as the illuminance or exposure time can be adjusted quickly, easily and inexpensively, automatically or manually, even in conventional image processing systems. The device according to the invention and / or the method according to the invention is particularly suitable for metrological applications and for surface and structure recognition. In this way, for example, material examinations and material tests can be carried out. On the other hand, it is possible to use the device and the method for structural analysis in the field of biology and chemistry, such as in electron microscopy. In a relatively simple manner, a suitable image evaluation can also be used to estimate the quantity of the recorded objects. For example, the number of people, cells, animals or other objects can be recorded.

A special measurement application is the target distance detection and control. With the use of the device according to the invention or the method according to the invention, distances can be determined quickly and reliably, so that distance control, such as distance control, is also possible without problems.

Claims

claims

1. Device for automatic focusing and exposure of image recording systems, with an image recording device (2) for recording objects (1), which is movable relative to the object (1) and by means of a focusing device and an exposure and / or lighting device, images of different sharpness and brightness, and a data processing system (18) which processes data of the image recording device (2), characterized in that the focusing and / or exposure for recording the object (1) by the image recording device (2) by means of the data processing system (18) is adjustable.

2. Device according to claim 1, characterized in that the manipulated variable (11) for changing the focus and / or the exposure for recording the object (1) is the amount of data that the data processing system (18) processes.

3. Apparatus according to claim 1 or 2, characterized in that the data of the image recording device (2) by means of a compression system (5) of the data processing system (18) compressible and in a memory (6) of the data processing system (18) can be stored, the compressed Data and / or the sizes of the memory space in the memory (6) serve as a manipulated variable (11).

4. Device according to one of the preceding claims, characterized in that the recording by the image recording device (2) takes place electronically and the data processing system (18) has an image signal converter (4), which converts the data of the image recording device (2) into a form that can be compressed by the compression system (5).

5. Device according to one of the preceding claims, characterized in that a controller (7) the manipulated variable

(11) for setting the distance (d) between the image recording device (2) and the object (1) and / or for adjusting the focal length of the lens of the image recording device (2) and / or for setting the exposure time of the image recording device (2) and / or Illuminance of a lighting device (3) used.

6. Device according to one of the preceding claims, characterized in that the compression system (5) is a digital signal (10) of the image recording device (2) or

Image signal converter (4) compressed and stored as a file in the memory (6).

7. The device according to claim 6, characterized in that the manipulated variable (11) is the amount of compressed data, the size of the file, the inverse compression rate and / or a combination of these sizes.

8. Device according to one of the preceding claims, characterized in that the manipulated variable (11) on one

Display (8) is displayed.

9. Device according to one of the preceding claims, characterized in that the maximum manipulated variable (11) represents a measure of the optimal setting of the image recording system.

10. Device according to one of the preceding claims, characterized in that the image recording device (2) is a CCD camera.

11. Method for the automatic focusing and exposure of image recording systems, in that objects (1) are recorded by an image recording device (2), the image recording device (2) being moved relative to the object (1) and focused by means of a focusing device, and the object (1) exposed for different lengths by means of different exposure times, or illuminated with different intensities by an illumination device (3), and wherein data from the image recording device (2) are forwarded to a data processing system (18), characterized in that the focusing and / or the exposure for recording the object (1) can be set by the image recording device (2) by means of the data processing system (18).

12. The method according to claim 11, characterized in that the data of the image recording device (2) is compressed by means of a compression system (5) of the data processing system (18) and stored in a memory (6) of the data processing system (18), the compressed ones Data and / or the sizes of the memory space in the memory (6) can be used as a manipulated variable (11) for setting the focus and / or the exposure.

13. The method according to any one of claims 11 or 12, characterized in that the manipulated variable (11) by a controller (7) for adjusting the distance (d) between the image recording device (2) and the object (1) and / or for adjusting the focal length of the lens of the image recording device (2) and / or for setting the exposure time of the image Recording device (2) and / or the illuminance of a lighting device (3) is used.

14. Use of the device and / or the method according to one of the preceding claims for metrological applications and for surface and structure recognition.

15. Use according to claim 14 for target distance detection and control.