Optical filtering device and method for using the same

• US 4,908,644 A
• Filed: 03/22/1988
• Issued: 03/13/1990
• Est. Priority Date: 03/23/1987
• Status: Expired due to Term

• Current Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Original Assignee: Asahi Kogaku Kogyo Kabushiki Kaisha
• Inventors: Shindo, Osamu, Toji, Shigeo, Suzuki, Noboru
• Primary Examiner(s): Perkey, W. B.
• Application Number:
  US07/171,794
• Time in Patent Office: 721 Days
• Field of Search: 354/402, 354/406, 354/407, 354/408, 250/201 PF, 364/572, 364/604, 364/728.01, 364/728.02, 364/724.12, 364/819, 364/825, 382/42, 382/49
• US Class Current: 708/315
• CPC Class Codes: G02B 7/365 by analysis of the spatial frequency components of the image
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing

Abstract

A filtering device for carrying out a filtering process in a space domain of image data derived from an external visual image input means and then delivering control information to a controlled driving device with the filtering device containing fundamental operator generation device for generating fundamental operators within the same fundamental operator series, and a filtering processing device for carrying out a convolution of a fundamental operator with an image data array and conducting a sequential series of such convolutions with varying input data based upon data detected at the output of the filter processing, so that the sequential convolution attains an effect equivalent to that attained by the direct convolution of the initial image data array with an expanded operator.

Claims

1. A filtering device for effecting a filtering process in a space-domain of initial image data derived from an external visual image input source, said filtering device comprising:

(a) fundamental operator generation means for generating fundamental operators within at least one fundamental operator series;

(b) filter processing means for convolving an initial input image data array and successive input image data arrays with respective fundamental operators to produce successive output image data arrays representative of the convolved input image data arrays;

(c) means for determining whether each said successive output image data array satisfies at least one predetermined condition; and

(d) means for selectively sending one of said output image data arrays to a post-filter processing device only when each said predetermined condition is satisfied by said one output image data array.

2. A filtering device in accordance with claim 1, further comprising means for sequentially sending said successive output image data arrays back to said filter processing means as said successive input image data arrays whenever each said predetermined condition is not satisfied by said successive output image data arrays.

3. A filtering device in accordance with claim 2, said filter processing means further comprising means for convolving a different fundamental operator from said series with a different input image data array each time an output image data array is sent back to said filter processing means.

4. A filtering device in accordance with claim 1, further comprising means for sequentially and selectively inputting successive output image data arrays generated by said filter processing means back into said filter processing means as successive input image data arrays, and convolving successive input image data arrays with different fundamental operators from said fundamental operator series.

5. A filtering device in accordance with claim 4, wherein said means for determining whether each of said output image data arrays satisfies at least one predetermined condition further comprises means for selectively inputting each successive output image data array into said filter processing means via a feedback loop.

6. A filtering device in accordance with claim 4, further comprising at least one memory storage region which comprises means for receiving successive output image data arrays from said filter processing means and for selectively inputting successive output image data arrays back into said filter processing means.

7. A filtering device in accordance with claim 4, further comprising at least one memory storage region for receiving said initial input image data array from said filter processing means and for selectively inputting said initial input image data array back into said filter processing means.

8. A filtering device in accordance with claim 1, wherein said fundamental operator generation means comprises a plurality of memory storage regions and means for receiving values representative of a variable integer (k), said memory storage regions comprising means for storing original, fundamental operators.

9. A filtering device in accordance with claim 8, wherein said original fundamental operators comprise at least one of the following:

an integration operator I(n,k), a differential operator of the first order D.sup.(+) (n,k), and a differential operator of the second order D"(n,k), each of said integration and differential operators being defined, respectively, as;

space="preserve" listing-type="equation">I(n,k)=(U(n)/2)+(1/4) (U(n+2.sup.k)+U(n-2.sup.k)),

space="preserve" listing-type="equation">D.sup.(+) (n,k)=(178 ) [U(n-2.sup.k)-U(n+2.sup.k)], and

space="preserve" listing-type="equation">D"(n,k)=(U(n)/2)-(1/4) [U(n+2.sup.k)+U(n-2.sup.k)]

where K=0, 1, 2, 3 . . .

10. A filtering device in accordance with claim 8, wherein said fundamental operator generation means comprises means for generating said fundamental operators by using a designated value of integer (k) and selecting one said original fundamental operator from one of said memory storage regions.

11. A filtering device in accordance with claim 1, wherein said fundamental operator generation means further comprises an output terminal for sending said fundamental operators generated by said fundamental operator generation means to said filter processing means.

12. A filtering device in accordance with claim 2, wherein said filter processing means comprises means for sending said output image data arrays to said determining means.

13. A filtering device in accordance with claim 1, said filter processing means comprising at least one input terminal for receiving said initial input image data array from said visual image input source and for receiving output image data arrays from an output image data memory storage region or from said determining means.

14. A filtering device in accordance with claim 1, wherein said determining means comprises means for comparing at least one condition of each of said output image data arrays with respective reference conditions.

15. A filtering device in accordance with claim 14, in combination with said post-filter processing device, said post-filter processing device comprising means for sending a control signal.

16. A filtering device in accordance with claim 15, wherein said control signal is sent to an automatic focus apparatus for a camera.

17. A filtering device in accordance with claim 1, said determining means further comprising means for sending a signal to said fundamental operator generation means, whenever each of said conditions is not satisfied, for selecting an original fundamental operator from a memory storage region in said fundamental operator generation means.

18. A filtering device in accordance with claim 1, further comprising a main program memory comprising means for storing a variable position integer (k), means for sending a signal representative of (k) to said fundamental operator generation means, and means for sending control signals to said filter processing device and to said determining means.

19. A filtering device in accordance with claim 1, in combination with said visual information input source, said source comprising a charge coupled device which is operated at equally spaced sampling intervals.

20. A filtering device in accordance with claim 1, wherein said filter processing means comprises a first memory storage region in which said initial input image data array is stored, and a second memory storage region in which successive output image data arrays are stored.

21. A filtering device in accordance with claim 20, wherein said filter processing means comprises means for selectively placing image data arrays into said first and second memory storage regions, and for recalling said image data arrays from said first and second memory storage regions.

22. A filtering device in accordance with claim 21, wherein said filter processing means comprises means for combining image data arrays stored in said first memory region and in said second memory region.

23. A filtering device in accordance with claim 1, wherein said at least one series of fundamental operators comprises a single series of fundamental operators.

24. A method for effecting a filtering process in a space-domain of an initial image data array derived from an external visual input source, said method comprising:

receiving said initial input image data array in a filter processing device;

generating a plurality of fundamental operators within at least one fundamental operator series;

convolving said initial input image data array with one of said fundamental operators in said filer processing device to produce an initial output image data array;

selectively inputting said initial output data array back into said filter processing device to be convolved with a different one of said fundamental operators by detecting at least one selected condition of said initial output image data array, and determining whether each said selected condition of said output image array satisfies a respective reference condition

generating at least one successive output image data array with said filter processing device and selectively and sequentially sending each successive output image data array, as successive input data arrays, back to said filter processing device, whenever each reference condition is not satisfied by each of said successive output image data arrays;

convolving a different fundamental operator from said fundamental operator series with a successive input image data array each time that a successive output image data array is sent back to said filter processing device;

outputting one of said output image data arrays only when each reference condition is satisfied; and

controlling an automatic focus mechanism of a camera with said signal.

25. A method for effecting a filtering process in a space-domain of an initial image data array derived from an external visual input source, said method comprising:

receiving said initial input image data array in a filter processing device;

generating a plurality of fundamental operators within at least one fundamental operator series;

convolving said initial input image data array with one of said fundamental operators in said filter processing device to produce an initial output image data array;

selectively inputting said initial output image data array back into said filter processing device to be convolved with a different one of said fundamental operators wherein said fundamental operators are generated by generating an original fundamental operator based upon at least one of the following element functions;

##EQU6## where x=n+K(k), K(k) being zero or a function of a variable k and n being the position of image data which has been convolved, wherein all of the fundamental operators in said fundamental operator series are based upon said original fundamental operators, said fundamental operator series containing at least one of the following;

(a) an integration operator I(n,k) defined as;

space="preserve" listing-type="equation">I(n,k)=(U(n/2)+(1/4) [U(n+2.sup.k)+U(n-2.sup.k)];

or

(b) a first order differential operator D.sup.(+) (n,k) defined as;

space="preserve" listing-type="equation">D.sup.(+) (n,k)=(1/2) [U(n-2.sup.k)-U(n+2.sup.k)];

or

(c) a second order differential operator D"(n,k) defined as;

space="preserve" listing-type="equation">D"(n,k)=(U(n)/2)-(1/4) [U(n+2.sup.k)+U(n-2.sup.k)]

where k=0, 1, 2, 3 .

26. A filtering device for effecting a filtering process in a space domain of image data derived from an external visual image input means, said device being adapted to deliver control information to a controlled driving means, said filtering device comprising;

means for generating an original fundamental operator;

filter processing means for convolving an initial input image data array and successive input image data arrays with respective fundamental operators to produce respective output image data arrays; and

means for sequentially convolving each input image data array by sequentially and selectively inputting successive output image data arrays from said filter processing means back into said filter processing means as said successive input image data arrays and by convolving each successive input image data array input back into said filter processing means with a different fundamental operator from said fundamental operator series, wherein said original fundamental operator is based upon at least one of the following element functions;

##EQU7## where x=n+K(k), K(k) being zero or a function of a variable k and n being the position of image data subjected to a filtering process, all fundamental operators in a single fundamental operator series being generated from said original fundamental operator, said original fundamental operator consisting of at least one of an integration operator I(n,k), a differential operator of the first order D.sup.(+) (n,k), a differential operator of the second order D"(n,k), with each of said integration and differential operators being defined below, respectively, as;

space="preserve" listing-type="equation">I(n,k)=(U(n/2)+(1/4)(U(n+2.sup.k)+U(n-2.sup.k)), and

space="preserve" listing-type="equation">D.sup.(+) (n,k)=(1/2)(U(n-2.sup.k)-U(n+2.sup.k)), and

space="preserve" listing-type="equation">D"(n,k)=(U(n)/2)-(1/4)(U(n+2.sup.k)+U(n-2.sup.k))

where k=0, 1, 2, 3.