Image correction device and image correction method thereof

1. Technical Field

The present disclosure relates to an image correction device and an image correction method for the image correction device.

2. Description of Related Art

A typical camera module includes a lens module and an image sensor. The lens module and the image sensor may not be aligned accurately. A center of an image taken by the camera module may deviate from a center of the image sensor. The deviation may render the test (e.g., the test of resolution) of the camera module inaccurately. In addition, the deviation may deteriorate the imaging quality of the camera module.

Therefore, it is desirable to provide an image correction device and an image correction method, which can overcome the above-mentioned limitations.

FIG. 1 is a block diagram of an image correction device according to an embodiment.

FIG. 2 is a plane view of a test chart according to one embodiment.

FIG. 3 shows an image of the test chart and four separated channel images, which are divided from the image according to different color channels.

FIG. 4 is a flow chart of an image correction method according to an embodiment.

Referring to FIG. 1 , an image correction device 30 according to an exemplary embodiment is shown. The image correction device 30 includes an image capturing module 31 , a first calculating module 33 , a second calculating module 35 , and a third calculating module 37 , and a correction module 39 .

The image capturing module 31 includes an image sensor 311 with a center. Coordinates of the center of the image sensor 311 are represented by (Xo, Yo). The image capturing module 31 is configured (i.e., structured and arranged) for taking an image 20 of a test chart 10 , as seen in FIGS. 2-3 . In the present embodiment, the image capturing module 31 is a video graphics array (VGA) camera module.

In the present embodiment, the test chart 10 is a substantially rectangular monochromatic picture. The test chart 10 includes one group of black stripes positioned in the middle thereof and four groups of black stripes respectively positioned in four corners. Each group of black stripes includes six equidistant parallel black stripes. Each black stripe is substantially a parallelogram. A center of the group of black stripes in the middle of the test chart 10 is coincident with the center of the test chart 10 . In the present embodiment, the size of the image 20 is 640 by 480 (640×480) pixels. The image 20 at least includes the group of black stripes in the middle of the test chart 10 , and the center of the group of black stripes is coincident with the center of the image 20 . The center of the group of black stripes means a center of a geometric figure formed by the whole group of black stripes.

The first calculating module 33 is configured for calculating coordinates of a center of each black stripe of the group of black stripes in the middle of the image 20 . The first calculating module 33 includes an image separating unit 331 , a first computing unit 333 , a brightness threshold setting unit 335 , a comparing unit 337 , and a second computing unit 339 .

Referring to FIG. 3 , the image separating unit 331 is configured for separating the image 20 according to different color channels, thus obtaining a Gr channel image 203 . In the present embodiment, referring to FIG. 3 , the image 20 is divided based on four different color channels, i.e., a red channel (R channel), a blue channel (B channel), a green-red channel (Gr channel), and a green-blue channel (Gb channel), thus obtaining an R channel image 201 , a B channel image 202 , a Gr channel image 203 , and a Gb channel image 204 . The size of each of the images 201 - 204 is 320 by 240 (320×240) pixels.

The first computing unit 333 is configured for computing a user-defined brightness of each pixel of the Gr channel image 203 . The user-defined brightness of a particular pixel is calculated according to the following method: choosing a square pixel area of n by n (n×n) pixels, which is centered at the particular pixel, calculating a sum of an actual brightness of each pixel within the square pixel area, dividing the sum by the total number of pixels within the square pixel area (i.e., n×n). In the present embodiment, n is equal to 77. A boundary of the square pixel area may be parallel or unparallel to a long line of the Gr channel image 203 .

The brightness threshold setting unit 335 is configured for setting a brightness threshold. The brightness threshold may be a user-defined brightness of a center of the Gr channel image 203 . The user-defined brightness of the center of the Gr channel image 203 is calculated as follows: choosing a rectangular pixel area of m by n pixels in the center of the Gr channel image 203 , calculating a sum of an actual brightness of each pixel within the rectangular pixel area, and dividing the sum by the total number of pixels within the rectangular pixel area (i.e., m×n). In the present embodiment, m is equal to 8, and n is equal to 4. In other embodiments, m may be equal to n.

The comparing unit 337 is configured for comparing a user-defined brightness of each pixel with the brightness threshold, and determining whether a pixel belongs to a black stripe based on the comparing result. If the user-defined brightness of a pixel is less than the brightness threshold, the comparing unit 337 determines that the pixel is positioned in a black stripe.

The second computing unit 339 is for computing coordinates of a center of each black stripe of the group of black stripes in the middle of the Gr channel image 203 according to coordinates of pixels positioned in each black stripe.

A method for calculating the coordinates of the center of a black stripe will be described with an example as follows. First, coordinates of four vertices of the black stripe (i.e., a top left vertex, a top right vertex, a bottom left vertex, and a bottom right vertex) are respectively supposed to be (1, 1), (3, 1), (0, 2), and (2, 2). Then, an X-coordinate of the center of the black stripe is calculated using the following equation: (0+3)/2=1.5, and a Y-coordinate of the center of the black stripe is calculated according to the equation: (1+2)/2=1.5. Accordingly, the coordinates of the center of the black stripe is (1.5, 1.5).

The second calculating module 35 is for calculating coordinates (Xc, Yc) of the center of the image 20 based on coordinates of centers of black stripes of the group of black stripes in the middle of the image 20 . In the present embodiment, the coordinates of the centers of six black stripes of the group of black stripes in the middle of the image 20 are respectively represented by (X1, Y1), (X2, Y2), (X3, Y3), (X4, Y4), (X5, Y5), and (X6, Y6). An X-coordinate of the image 20 is calculated according to the equation Xc=(X1+X2+X3+X4+X5+X6)/6, while a Y-coordinate of the image 20 is calculated based on the equation Yc=(Y1+Y2+Y3+Y4+Y5+Y6)/6.

The third calculating module 37 is configured for calculating a coordinate deviation (ΔX, ΔY)=(Xc−Xo, Yc−Yo) between the center of the image 20 and the center of the image sensor 311 .

The correction module 39 is for inputting the coordinate deviation (ΔX, ΔY) into the image sensor 311 via an inter-integrated circuit ( 12 C). The image sensor 311 corrects images according to the coordinate deviation (ΔX, ΔY).

Referring to FIG. 4 , a method for correcting images using the image correction device 30 according to one embodiment will be described as follows.

In step S 1 , the image 20 of the test chart 10 is taken using the image capturing module 31 . The image 20 at least includes the group of black stripes in the middle of the test chart 10 , and the center of the group of black stripes is coincident with the center of the image 20 .

In step S 2 , coordinates of a center of each black stripe of the group of black stripes in the middle of the image 20 are calculated.

In step S 3 , coordinates (Xc, Yc) of the center of the image 20 are calculated based on coordinates of centers of black stripes of the group of black stripes in the middle of the image 20 .

In the present embodiment, the coordinates of the centers of six black stripes of the group of black stripes in the middle of the image 20 are respectively represented by (X1, Y1), (X2, Y2), (X3, Y3), (X4, Y4), (X5, Y5), and (X6, Y6). An X-coordinate of the image 20 is calculated according to the equation Xc=(X1+X2+X3+X4+X5+X6)/6, while a Y-coordinate of the image 20 is calculated based on the equation Yc=(Y1+Y2+Y3+Y4+Y5+Y6)/6.

In step S 4 , a coordinate deviation (ΔX, ΔY)=(Xc−Xo, Yc−Yo) between the center of the image 20 and the center of the image sensor 311 is calculated.

In step S 5 , the coordinate deviation (ΔX, ΔY) is input into the image sensor 311 via an inter-integrated circuit (I2C), and then the image 20 is corrected according to the coordinate deviation (ΔX, ΔY).

Sub-steps of the step S 2 will be described as follows.

In step S 21 , referring to FIG. 3 , the image 20 is separated according to different color channels, thus obtaining a Gr channel image 203 .

In step S 22 , a user-defined brightness of each pixel of the Gr channel image 203 is calculated.

In step S 23 , a brightness threshold is set.

In step S 24 , a user-defined brightness of each pixel is compared with the brightness threshold, and it is determined whether a pixel belongs to a black stripe based on the comparing result. If the user-defined brightness of a pixel is less than the brightness threshold, the comparing unit 337 determines that the pixel is positioned in a black stripe.

In step S 25 , coordinates of a center of each black stripe of the group of black stripes in the middle of the Gr channel image 203 are calculated according to coordinates of pixels positioned in each black stripe.

In the present embodiment, the step S 2 is conducted using the Gr channel image 203 because the Gr channel image 203 has the highest contrast of the four channel images. In alternative embodiments, the step S 2 may be conducted based on other channel images, e.g., the R channel image.

While various embodiments have been described, it is to be understood that the disclosure is not limited thereto. To the contrary, various modifications and similar arrangements (as would be apparent to those skilled in the art), are also intended to be covered. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.