JPH01144871A - Image input device - Google Patents

Abstract

PURPOSE:To always obtain a focussed image by generating a summed-up image of images from plural-distance image pickup device, extracting an image of maximum/minimum output in an extent where thus obtained second order differential value is negative/positive and obtaining a synthetic image out of extracted images. CONSTITUTION:The plural-distance image pickup device 1 picks up the image of an object of image pickup in plural scenes corresponding to different image forming distances, and a summed-up image forming means 2 sums the picked up plural images. A second order differentiating means 3 second order differentiates this summed-up image to obtain a second order differential image, and a decision means 4 extracts an image in maximum value or minimum value respectively in respective areas corresponding to the positiveness or negativeness of the value of the second order differential image. Further, an image synthesizing means 5 synthesizes images in each area thus extracted. As a result, a fully focussed image can be obtained even for such an object of image picking-up that its image pickup distance in the image pickup device varies beyond the range of the depth of focus of an image pickup lens.

Description

[Detailed Description of the Invention] [Summary] Regarding an image input device that can obtain in-focus images over the entire surface of a target object having multiple height levels, the in-focus state can be obtained from images of a multiple distance imaging device. By selecting and compositing only images, it is now possible to obtain fully focused images even for subjects whose imaging distance varies beyond the focal depth range of the imaging lens. a multi-distance imaging means for imaging an object to be imaged on a plurality of screens corresponding to different imaging distances, a sum image creation means for taking the sum of the plurality of images, and a sum image second-order differentiating means for obtaining a second-order differential image by second-order differentiating the second-order differential image; determining means for extracting an image that takes the maximum or minimum value in each region depending on whether the value of the second-order differential image is positive or negative; and image composing means for composing an image by composing the regions.

[Industrial application field]

The present invention relates to an image input device that can obtain an image that is in focus over the entire surface of a target object having multiple height levels.

In an imaging device, when multiple target objects are located at different distances from the imaging lens, or when each part of the surface of the same target object is located at a different distance from the imaging lens, the distance If the difference is not within the depth of focus determined by the lens, it is usually not possible to capture a clear image with all parts in focus.

However, in practice, it is necessary to obtain an image that is in focus over the entire surface even when the range in which the imaged object exists exceeds the depth of focus range of the imaging lens. There are cases.

[Conventional technology]

Conventionally, methods for capturing images of such a wide range of objects include methods of moving a sensor placed on the imaging plane with respect to a fixed imaging lens according to the imaging distance, or using a half mirror, etc. A method of dividing the optical path of the imaging lens □ and arranging sensors at different focal positions to capture an image has been used.

FIG. 5 shows an example of a conventional multi-distance imaging device, in which the sensor is moved.

In FIG. 5, the imaging lens 11 is fixedly provided to the imaging device. On the imaging plane, the height is detected by a sensor 12 such as a COD area sensor (video camera sensor), and the sensor 12 is mounted on a moving stage 13 and is configured to be movable according to the imaging distance. .

Now, from the center of the imaging lens 11 to the object to be imaged 141°1
4. 14. The distance to
'1 s am, the distance from the lens center to the imaging plane, that is, the imaging distance is bIs bMp bm
, the moving stage 13 is controlled to set the imaging distance a
1 to tLs so that the imaging distance becomes bM-63, focused images can be obtained for all of the imaged objects 141 to 141.

FIG. 6 shows another example of the conventional multi-distance imaging device, in which a plurality of sensors are used.

In FIG. 6, the optical path of the imaging lens 11 is divided by half mirrors 151 and 15, and each sensor 1
21 = 12m -121, but at this time, from the center of the imaging lens 11 to each sensor 12+,
Distance up to 12*-12m, i.e. imaging distance bit t
6*e bM is the imaged object 141.14. ,1
4. The focusing distance is selected to be the focusing distance when the distance to the object, that is, the imaging distance is '11'l*α1. Therefore, in the case of FIG. 6 as well, the objects to be imaged 141 to 14. A focused image can be obtained for all of the following.

[Problem that the invention seeks to solve]

In the conventional multi-distance imaging device as shown in FIGS. 5 and 6, it is possible to image an object to be imaged at an imaging distance corresponding to a certain imaging distance in a focused state. However, objects to be imaged at other imaging distances are not within the focal depth range of the imaging lens, and therefore cannot be imaged in focus.

FIG. 7 shows an example of an image taken by a conventional multi-distance imaging device, where (α) shows the relationship between the imaging device and the object to be imaged, and the object is When the imaging surface 16 is tilted from the vertical, the imaging distance differs for each part of the fr 16. Each part of the current surface 16 161.16 m
16s is assumed to have progressively smaller chronic injury distances, and the images taken by the sensor 12 are shown in (b) when the imaging distances are set according to the respective imaging distances.

(a), cd). In each image, the portions corresponding to the imaging distances 161 and 16 i6g are in focus, but the other portions are out of focus and a clear image cannot be obtained.

The present invention aims to solve such problems, and by selecting and combining only in-focus images from images taken by a multi-distance imaging device, the imaging distance can be adjusted to the depth of focus of the imaging lens. The object of the present invention is to make it possible to obtain a completely focused image even for an object to be imaged that changes over a range.

[Means for solving problems]

FIG. 1 shows the basic configuration of the present invention, which includes a multi-distance imaging means 1, a sum image forming means 2, a second-order differentiating means 3, a determining means 4, and an image synthesizing means 5. It is designed with a focus on

The multi-distance imaging means 1 images an object to be imaged on a plurality of screens corresponding to different imaging distances.

The sum image forming means 2 calculates the sum of the plurality of captured images.

The second-order differentiating means 3 performs second-order differentiation on the sum image to obtain a second-order differential image.

The determining means 4 extracts an image that takes the maximum or minimum value in each region depending on whether the value of the second-order differential image is positive or negative.

The image synthesizing means 5 synthesizes images for each extracted region.

[For production]

The same object to be imaged is imaged on a plurality of screens corresponding to different imaging distances depending on the focal depth range of an imaging lens. Then, all the captured images are added together to create a sum image. The sum image thus created is second-order differentiated to obtain a second-order differential image represented by the second-order differential value of each point. Then, depending on whether the value of the second-order differential image is positive or negative, an image having the maximum or minimum value in each region is extracted from the plurality of captured images. A composite image is then obtained by combining the images of all the extracted regions.

The second-order differential image takes a value of 0 at the boundary between dark and light on a grayscale screen, a positive value for a light pattern on a dark background, and a negative value for a dark pattern on a light background. Are known. The image center amount corresponding to the positive or negative range of the second-order differential image also has a large value in the focused image. Therefore, all parts of the image synthesized as described above are in focus. In this way, it is possible to obtain a fully focused image even for an object to be imaged whose imaging distance to the object varies beyond the depth of focus range of the imaging lens.

〔Example〕

FIG. 2 is a block diagram showing the overall configuration of an embodiment of the present invention. In the same figure, 21 is a multi-range imaging device, which has a configuration as shown in FIG. 6 or FIG. 6, etc.
It includes an imaging lens and a sensor such as a CCD area sensor, and can obtain n images corresponding to n imaging distances. 22 is an image input circuit that digitizes the image signal obtained from the imaging device 21 and outputs it for each image. This signal is input to an original image memory 23 consisting of three sides and stored for each image.

In the embodiment of FIG. 2, in order to further perform image processing, the sum image generation circuit 24. It has a sum image memory 25°, a second-order differential circuit 262, a judgment circuit 272, an image composition circuit 28°, and a composite image memory 29. Each part is interconnected via a bus 30, and operates according to a certain sea case under the control of a control circuit 31. The n images configured to do so are stored in the three-sided frame memory 23. as described above. Each image is stored in the original image memory 23 consisting of ~23%.

Each memory 23 in the original image memory 23. ~23%
, the image tl(
x, y) to 8 (X, Y) are stored. Here, X and Y represent coordinates on the image plane.

The sum image creation circuit 24 inputs (X, Y) to f% (z,
Create the sum F(X, Y) of y). That is, F(X, Y
) is F(X, Y)=, Σft(z, y) ・
...(1) ml The sum image created in this way is stored in the sum image memory 25.
is memorized.

Next, the second-order differential circuit 26 performs second-order differentiation on the sum image F'(X, Y) to create a second-order differential image G(X, Y). That is, the second-order differential image G (X, Y) determination circuit 27 determines whether the value of the second-order differential image G (X, Y) is positive or negative, and extracts the image from the original image memory 23 according to the determination result. That is, for the region (11G(X,Y)<0, Mat l/
Extract i l.

(2) For the region G(X, Y>>0, MifL[
Extract fs l.

Here, Mat l/, l and Mjs[/jl are images corresponding to the imaging distance bi at which the image output is maximum or minimum, respectively.

FIG. 4 explains extraction of a second-order differential image. In the figure, (b)) indicates an image/area having a certain pattern. ) indicates the output when the image area of the dove is scanned in the X-r direction, 6 is the output corresponding to the imaging distance b1 closest to the focus, G p 'M *..., h is the imaging distance away from the secondary focus position b* e h
This is the output corresponding to a e...-, bs. (6) is the output p (=e, +tr, +...
+gs). (d) is the second-order differential output G(=C,X2 +p)Fl for the Waji La image
As described above, the image Maz I til with the maximum value is selected for the area where a<a, and the image Win (fil) with the minimum value is selected for the area where G>0.

In Figure 4, (1) shows the case of a light pattern on a dark background.
(2) shows the case of an agricultural pattern on a light background; in either case, by selecting the image with the minimum or maximum output depending on the sign or negative of the second-order differential value G, it is possible to extract the image closest to the in-focus state. It is shown.

The image synthesis circuit 28 reads out the image extracted by the determination circuit 27 from its memory, and stores it in the synthesized image memory 29.
write to the corresponding position in .

The control circuit 31 completes such processing for all images in the original image memory 23 and outputs an image signal from the composite image memory 29 when writing to all areas in the composite image memory 29 is completed. . This image is a desired image, and its entire surface is composed of a region in focus.

〔Effect of the invention〕

As explained above, according to the present invention, a sum image of images from multiple distance imaging devices is created and the second-order differential value thereof is determined. In the range of , the image with the minimum output is extracted and a composite image is obtained from the extracted images, so even if the imaging distance changes beyond the focal depth range of the imaging lens, the entire image will be covered. It is possible to obtain an image that is in focus.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIG. 2 is a diagram showing the overall configuration of an embodiment of the present invention, and FIG. 3 is a diagram showing the configuration for image processing in the embodiment of FIG. 2.゛ Figure 4 is a diagram explaining the extraction of a second-order differential image, Figure 5
Figure 6 is a diagram showing an example of a conventional multiple distance imaging device; Figure 6 is a diagram showing another example of a conventional multiple distance imaging device; Figure 7 is a diagram showing an example of an image taken by a conventional multiple distance imaging device. be. 21... Multiple distance imaging device 22... Image input circuit 23... Original image memory 24... Sum image creation circuit 25... Sum image memory 26... Second order differential circuit 27... Judgment circuit 28...-Image synthesis circuit 29...Composition image mesori 30...Bus 31...Control circuit

Claims (1)

[Scope of Claims] Multi-distance imaging means (1) for imaging an object to be imaged on a plurality of screens corresponding to different imaging distances, and sum image creation means (2) for calculating the sum of the plurality of images taken. and second-order differentiating means (3) for second-order differentiating the sum image to obtain a second-order differential image; a determining means (4) for extracting; and an image synthesizing means (4) for synthesizing images for each extracted area;
5) An image input device comprising: