JP2007264087A - Focus state detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus state detecting device capable of detecting the optional focus state of a camera with a simple configuration. <P>SOLUTION: The focus state detecting device detects the focus state of the camera by utilizing the fact that the area of a blurred area 3a formed in the center of the radial parts of a test pattern 3 formed into a radial pattern reflected in a picked-up image G by the camera changes to increase or decrease in accordance with the focus state of the camera. The device is equipped with: an extraction means for extracting the blurred area 3a from the picked-up image G reflected in the test pattern 3 picked up by the camera based on a luminance signal; a calculation means for calculating the area of the blurred area 3a extracted by the extraction means; and a detection means for detecting the focus state of the camera based on the size of the area of the blurred area 3a calculated by the calculation means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a focus state detection device that detects a focus state of a camera.

  Cameras that do not have an autofocus function (for example, in-vehicle cameras) require focus adjustment at the assembly stage.

  In a conventional focus adjustment device, a test pattern is captured by a camera, a frequency component in a predetermined band is extracted from the video signal of the captured image, and the voltage level in the frequency component corresponds to the definition of the image Then, the focus state of the camera is adjusted to just focus by adjusting the camera adjuster and adjusting the lens position of the camera so that the voltage level in the frequency component becomes maximum.

  Patent Document 1 is known as a prior art related to such focus adjustment.

JP 2005-292779

  However, in the conventional focus adjustment device, when the frequency component of the predetermined band is not included in the video signal of the captured image, the frequency component of the predetermined band is extracted again from the video signal of the captured image. There was a drawback that it was necessary.

  As a solution to this drawback, a filter circuit for extracting frequency components in a plurality of bands is provided, and frequency components in a plurality of bands are extracted in advance by the filter circuit, and a frequency in a band in which the frequency components are sufficiently contained. It is conceivable to adjust the focus using the components.

  In any case, the conventional focus adjustment device and the above-mentioned proposal have a drawback that the device becomes complicated because a frequency component extraction filter (that is, a complicated circuit) is used.

  In addition, since the conventional focus adjustment device cannot detect a focus state other than just focus, there is a disadvantage that the focus state of the camera cannot be adjusted to an arbitrary focus state.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a focus state detection apparatus that can detect an arbitrary focus state of a camera with a simple configuration.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that the area of a blur region generated in a predetermined range of a test pattern of a predetermined pattern reflected in a captured image of the camera is increased or decreased according to the focus state of the camera. And a focus state detection device for detecting a focus state of the camera, wherein the test pattern has a high luminance color region and a low luminance color region so that the width of at least one of them gradually increases. An extraction means for extracting the blur region based on a luminance signal from the captured image in which the test pattern captured by the camera is captured, and extracted by the extraction means. And calculating means for calculating the area of the blurred area, and based on the size of the area of the blurred area calculated by the calculating means, the focus state of the camera is determined. Detection means for output, but with a.

  According to a second aspect of the present invention, the extraction unit performs contour extraction processing, binarization processing, and expansion processing on the captured image in order to extract the blur region from the captured image. .

  According to the first aspect of the present invention, the blur area is extracted based on the luminance signal from the captured image in which the test pattern of the radiation pattern captured by the camera is reflected, the area is calculated, and the size of the area is calculated. Since the focus state of the camera is detected based on this, it is possible to easily detect a focus state other than just focus based on the size of the area.

  In addition, since the focus state of the camera is detected by obtaining the area of the blurred region based on the luminance signal of the captured image, that is, since the frequency component of the captured image is not used, it is not necessary to use a frequency component extraction filter as in the past. The apparatus can be configured with a simple configuration.

  According to the second aspect of the present invention, the contour extraction process, the binarization process, and the expansion process are sequentially performed on the captured image to extract the blurred region from the captured image, so that a known image processing technique is used. Thus, a blurred region can be easily extracted from the captured image.

  FIG. 1 is a schematic configuration diagram of a focus adjustment device using the focus state detection device according to this embodiment.

  As shown in FIG. 1, the focus adjustment device 1 adjusts the focus state to a predetermined focus state, for example, at the assembly stage of a camera (for example, an in-vehicle camera) 5 that does not have an autofocus function.

  The focus adjustment device 1 is a camera based on a test pattern 3 having a predetermined pattern, a driving device 7 that adjusts the lens position of the camera 5 back and forth along the optical axis direction, and a test pattern 3 reflected in a captured image of the camera 5. Based on the detection result of the focus state detection unit 9 (focus state detection device) 9 for detecting the focus state 5 and the focus state detection unit 9, the drive device 7 is driven so that the focus state of the camera 5 becomes a predetermined focus state. And a control unit 11 for controlling.

  Here, the camera 5 includes, for example, a substantially cylindrical holder unit 5a, an optical lens unit 5b inserted from one end of the holder unit 5a, and a CCD or CMOS inserted from the other end of the holder unit 5a. And the like, and an image is obtained by forming light from a predetermined imaging range on the light receiving surface of the imaging element 5c by the lens unit 5b.

  The lens unit 5b is coupled to the holder portion 5a by an adjuster portion 5d. By rotating the adjuster 5d, the lens unit 5b moves along the axial direction of the holder 5a. The focus state of the camera 5 is adjusted by the movement of the lens unit 5b. The adjuster portion 5d has a driven gear portion 5e on its outer peripheral portion so that it can be driven and rotated by the drive device 7.

  The test pattern 3 has a pattern in which a high luminance color region and a low luminance color region are alternately repeated so that the width of at least one of them gradually increases. Specifically, here, for example, as shown in FIG. 2, the test pattern 3 includes a linear black region 3B that is a low luminance color (for example, black) region and a line that is a high luminance color (for example, white) region. The white pattern 3W has a radial pattern (that is, a pattern in which both widths are alternately repeated in the circumferential direction so that the width of both of them gradually increases from the center point toward the radially outer side). ing.

  As shown in FIG. 3, the focus state detection unit 9 has an area of a blurred region 3 a generated in a predetermined range (here, the radiation center) of the test pattern 3 of a predetermined pattern (here, a radiation pattern) reflected in the captured image G of the camera 5. However, the focus state of the camera 5 is detected by utilizing the fact that the camera 5 changes in accordance with the focus state (that is, the area of the blurring region 3a becomes smaller as the focus state of the camera 5 approaches the just focus). To do.

  In general, when the test pattern 3 is a pattern in which a high luminance color region and a low luminance color region are alternately repeated so that the width of at least one of them gradually increases in the same direction, a camera is used. According to the focus state of 5, the blurred region is generated in the relatively narrow portion of the test pattern.

  As shown in FIG. 1, the focus state detection unit 9 includes an extraction unit 9 a that extracts a blur region 3 a based on a luminance signal from a captured image G in which a test pattern 3 captured by the camera 5 is captured, and an extraction unit 9 a. Calculating means 9b for calculating the area of the blurred region 3a extracted by the above, and detecting means 9c for detecting the focus state of the camera 5 based on the size of the area of the blurred region 3a calculated by the calculating means 9b.

  The extraction unit 9a performs a cutout process, a contour extraction process, a binarization process, and an expansion process on the captured image G in order to extract the blurred region 3a from the captured image G.

  More specifically, in the above-described cutting process, a portion where the test pattern 3 is reflected is cut out from the captured image G as shown in FIG. In the contour extraction process, as shown in FIG. 5, a differential filter (for example, Prewitt filter) is applied to the luminance signal of the cut out portion, and the contour of the radiation pattern of the test pattern 3 is extracted. In the binarization process described above, as shown in FIG. 6, in each pixel, pixels having a luminance equal to or higher than a predetermined value are set to white, and pixels having a luminance lower than the predetermined value are set to black. In the above expansion processing, as shown in FIG. 7, if at least one pixel is white in the vicinity of each pixel, the pixel is made white. As a result, the test pattern 3 (radiation pattern) reflected in the captured image G is obtained. ), The non-blurred region 3b is white, and the blurred region (blurred region) 3a is black. In this way, the blurred region 3a is extracted from the captured image G as a black region.

  The calculating unit 9b calculates the area of the black region (blurred region) 3a in the predetermined range (for example, the central portion) 3c (see FIG. 7) of the image extracted by the extracting unit 9a (here, the predetermined range 3c). By calculating the number of pixels of the black area 3a in the inner area), the area of the blurred area 3a is calculated.

  The detection unit 9c detects the focus state of the camera 5 as a numerical value (a numerical value determined according to the area of the blurred region 3a) based on the calculation result of the calculating unit 9b.

  As shown in FIG. 1, the drive device 7 is engaged with the driven gear portion 5e of the adjuster portion 5d of the camera 5 to rotate the adjuster portion 5d, and a drive portion 7b that rotates the drive gear portion 7a. Is provided.

  The control unit 11 compares the detection result of the focus state detection unit 9 with a predetermined threshold value set in advance (threshold value corresponding to the predetermined focus state), and drives the drive device 7 so that both values match. By driving and controlling the unit 7b, the lens position of the lens unit 5b of the camera 5 (relative position in the optical axis direction from the light receiving surface of the image sensor 5c) is adjusted. Note that the focus state of the camera 5 is adjusted to a desired focus state by setting the predetermined threshold value to a desired threshold value.

  Next, the operation of the focus adjustment device 1 will be described.

  First, as shown in FIG. 1, the camera 5 is installed on a predetermined fixing base (not shown) such that the drive gear portion 7a of the drive device 7 meshes with the driven gear portion 5e of the adjuster portion 5d. In this state, the test pattern 3 is arranged in front of the camera 5 and the test pattern 3 is imaged by the camera 5.

  The captured image G (see FIG. 3) is output to the focus state detection unit 9, and, as described above, is extracted from the captured image G in which the test pattern 3 is reflected by the extraction unit 9a based on the luminance signal. The area 3a is extracted, the area of the extracted blurred area 3a is calculated by the calculating means 9b, and the focus state of the camera 5 is detected by the detecting means 9c based on the size of the area of the blurred area 3a.

  Then, the control unit 11 compares the detection result of the focus state detection unit 9 with a predetermined threshold value (threshold value corresponding to the predetermined focus state). If they match, the camera 5 is in the predetermined focus state, and the focus adjustment is finished. On the other hand, if the two do not match, the values of the two match. The driving unit of the driving device 7 is driven and controlled, and the lens position of the lens unit 5b of the camera 5 is adjusted. Thus, the focus state of the camera 5 is adjusted to a predetermined focus state.

  According to the focus adjustment device 1 configured as described above, the blur region 3a is extracted from the captured image G in which the test pattern 3 having a predetermined pattern (here, a radiation pattern) captured by the camera 5 is reflected based on the luminance signal. Since the area is extracted and calculated, and the focus state of the camera 5 is detected based on the size of the area, a focus state other than just focus can be easily detected based on the size of the area.

  Further, since the focus state is detected by obtaining the area of the blurred region 3a based on the luminance signal of the captured image, that is, since the frequency component of the captured image is not used, it is not necessary to use the frequency component extraction filter as in the prior art. The state detection device (and hence the focus adjustment device 1) can be configured with a simple configuration.

  In addition, since the contour extraction process, the binarization process, and the expansion process are sequentially performed on the captured image to extract the blurred region 3a from the captured image, the image can be easily extracted from the captured image using a known image processing technique. The blurred area 3a can be extracted.

  In this embodiment, the radiation pattern test pattern is used as the test pattern 3, but instead, a test pattern 3 ′ having a concentric pattern as shown in FIG. 8 or a test having a concentric rectangular pattern as shown in FIG. A pattern 3 ″ or a striped test pattern 3 ′ ″ as shown in FIG. 10 may be used.

  More specifically, in the concentric test pattern 3 ′ shown in FIG. 8, the annular black region 3B ′ and the annular white region 3W ′ are gradually increased in width from the central portion 3s ′ toward the radially outer side. The pattern is repeated alternately in the radial direction so as to increase (the black region 3B ′ may be a line having a constant width without increasing the width). In the test pattern 3 ′, a blurred region is generated in a relatively narrow central portion including the central portion 3 s ′ in accordance with the focus state of the camera 5.

  Further, the test pattern 3 ″ having a concentric rectangular pattern in FIG. 9 has a rectangular black region 3B ″ and a rectangular white region 3W ″, both of which are radially outward from the central portion 3s ″. The pattern is repeated alternately in the radial direction so as to gradually increase (the black region 3B ″ may be a line having a constant width without increasing the width). In the test pattern 3 ″, a blurred region is generated in a relatively narrow central portion including the central portion 3s ″ according to the focus state of the camera 5.

  Further, the striped test pattern 3 ′ ″ in FIG. 10 has a linear black region 3B ′ ″ and a linear white region 3W ″ ′ whose center width is a center line (here, an oblique line). The pattern is alternately repeated in the direction orthogonal to the center line 3s ′ ″ so as to gradually increase from 3s ′ ″ toward the outside in the direction orthogonal to the center line 3s ′ ″. Line 3s' '' may be a vertical line or a horizontal line). In the test pattern 3 ′ ″, a blurred region is generated in a relatively narrow central portion including the center line 3s ′ ″ according to the focus state of the camera 5.

It is a block diagram of the focus adjustment apparatus which concerns on embodiment of this invention. It is an example figure of a test pattern (radiation pattern). It is a figure explaining the relationship between a focus state and a blurring area. It is the figure which cut out the part in which the test pattern was reflected from the captured image. It is the figure which performed the contour extraction process to the part cut out of FIG. FIG. 6 is an example of an image obtained by performing binarization processing on the image subjected to contour extraction processing in FIG. 5. FIG. 7 is an example of an image obtained by performing an expansion process on the binarized image of FIG. 6. It is an example figure of the modification (concentric pattern) of a test pattern. It is an example figure of the other modification (concentric rectangular pattern) of a test pattern. It is an example figure of the other modification (striped pattern) of a test pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Focus adjustment apparatus 3 Test pattern 3a Blurred area 5 Camera 7 Drive apparatus 9 Focus state detection part 9a Extraction means 9b Calculation means 9c Detection means 11 Control part

Claims (2)

Focus state detection that detects the focus state of the camera by utilizing the fact that the area of the blur region generated in the predetermined range of the test pattern of the predetermined pattern reflected in the captured image of the camera changes in accordance with the focus state of the camera A device,
The test pattern has a pattern in which a high luminance color region and a low luminance color region are alternately repeated so that the width of at least one of them gradually increases,
Extraction means for extracting the blur region based on a luminance signal from within a captured image of the test pattern captured by the camera;
Calculating means for calculating the area of the blurred region extracted by the extracting means;
Detecting means for detecting a focus state of the camera based on the size of the area of the blurred region calculated by the calculating means;
A focus state detection device comprising: 2. The focus according to claim 1, wherein the extraction unit sequentially performs contour extraction processing, binarization processing, and expansion processing on the captured image to extract the blurred region from the captured image. State detection device.

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