Method and apparatus for adjusting installation flatness of lens in real time

1. A method for adjusting the installation flatness of a lens in real time, comprising:

acquiring an image comprising a plurality of testing charts captured by a camera in real time, wherein the image comprises at least two groups of testing charts corresponding to different positions of a camera photosensitive surface;

pre-processing the image comprising the plurality of testing charts to separate the at least two groups of testing charts from the image,

wherein the step of pre-processing the image includes:

performing filtering on the image to obtain testing chart regions in different directions; and

performing image binarization on the testing chart regions to separate the at least two groups of testing charts from the image;

calculating and displaying, based on each group of testing charts separated from the image, a real-time resolution value associated with the camera photosensitive surface for each group of testing charts in real time; and

adjusting the installation angle of the optical axis of the camera lens relative to the photosensitive surface in real time based on at least one of the real-time resolution values associated with the camera photosensitive surface for each group of testing charts.

2. The method of claim 1 , wherein each group of testing charts comprises at least one testing stripe set, each testing stripe set comprises a plurality of testing stripes spaced apart from each other, and the distances between the testing stripes increase or decrease gradually in a direction perpendicular to the spacing direction of the testing stripes.

3. The method of claim 1 ,

wherein each group of testing charts comprises a first testing stripe set and a second testing stripe set;

wherein the first testing stripe set comprises a plurality of first testing stripes spaced apart from each other in a first direction and extending in a second direction perpendicular to the first direction, with the distances between the first testing stripes increasing or decreasing gradually in the second direction; and

wherein the second testing stripe set comprises a plurality of second testing stripes spaced apart from each other in the second direction and extending in the first direction, with the distances between the second testing stripes increasing or decreasing gradually in the first direction.

4. The method of claim 1 , wherein the at least two groups of testing charts comprises five groups of testing charts, wherein four groups of testing charts of the five groups of testing charts correspond to four corners of the camera photosensitive surface and a fifth group of testing charts of the five groups of testing charts corresponds to the center of the camera photosensitive surface.

5. The method of claim 1 , wherein the step of calculating and displaying, based on each group of testing charts separated from the image, the real-time resolution value associated with the camera photosensitive surface for each group of testing charts in real time comprises:

sampling each group of testing charts by row or by column to obtain a plurality of stripe square-wave signals, wherein each group of testing charts is associated with at least one stripe square-wave signal;

performing Fourier transformation on the plurality of stripe square-wave signals to produce spectrum charts, wherein each stripe square-wave signal corresponds to a respective spectrum chart of the plurality of spectrum charts; and

calculating and displaying the real-time resolution value associated with the camera photosensitive surface for each group of testing charts based on the spectrum chart of each stripe square-wave signal.

6. The method of claim 5 , wherein the step of calculating the real-time resolution value associated with the camera photosensitive surface for each group of testing charts based on the spectrum chart of each stripe square-wave signal comprises:

calculating an average frequency amplitude A aver and a characteristic frequency amplitude A t of each stripe square-wave signal based on the spectrum chart of the stripe square-wave signal;

determining whether the characteristic frequency amplitude A t of each stripe square-wave signal satisfies a condition based on the following formula:

A t / A aver >Thres

wherein Thres is a preset threshold; and

for each group of testing charts, determining a resolution value corresponding to the associated stripe square-wave signal to be the real-time resolution value associated with the camera photosensitive surface for the group of testing charts if the characteristic frequency amplitude A t of the associated stripe square-wave signal satisfies the condition.

7. The method of claim 5 , further comprising:

before the step of performing Fourier transformation on the plurality of stripe square-wave signals, removing a direct-current (DC) component of each stripe square-wave signal through the following operation:

x ′( k )= x ( k )-mean( x ( k ));

wherein x(k) is the stripe square-wave signal before the DC component is removed, mean(x(k)) is the average value of the stripe square-wave signal before the DC component is removed, and x′(k) is the stripe square-wave signal after the DC component is removed.

8. The method of claim 1 , further comprising:

before pre-processing the image, rotating the image comprising the plurality of testing charts captured by the camera according to the following formula:

{

x

0

=

x

⁢

⁢

cos

⁢

⁢

θ

+

y

⁢

⁢

sin

⁢

⁢

θ

+

m

y

0

=

-

x

⁢

⁢

sin

⁢

⁢

θ

+

y

⁢

⁢

cos

⁢

⁢

θ

+

n

,

wherein, m=−0.5W cos θ−0.5H sin θ+0.5W 0 ,

n=0.5W sin θ−0.5H cos θ+0.5H 0 ,

x 0 and y 0 represent the horizontal coordinate and the vertical coordinate of a pixel point in the image respectively before the rotation,

x and y represent the horizontal coordinate and the vertical coordinate of the pixel point in the image respectively after the rotation,

H 0 and W 0 represent the height and the width of at least one testing chart of the plurality of testing charts in the image respectively before the rotation,

H and W represent the height and the width of the at least one testing chart in the image after respectively after the rotation, and

θ represents rotation angle.

9. The method of claim 1 , wherein the step of pre-processing the image further comprises:

performing gray processing on the image comprising the plurality of testing charts; and

performing morphological filtering on the gray processed image to obtain the testing chart regions in different directions.

10. An apparatus for adjusting the installation flatness of a lens in real time, the apparatus comprising:

a target;

a processing system; and

a display device,

wherein the target is configured to present at least two groups of testing charts corresponding to different positions of a camera photosensitive surface,

wherein the processing system is configured to:

receive an image comprising the at least two groups of testing charts captured by the camera,

pre-process the image comprising the at least two groups of testing charts to separate the at least two groups of testing charts from the image, the processing system being further configured to:

perform filtering on the image to obtain testing chart regions in different directions: and

perform image binarization on the testing chart regions to separate the at least two groups of testing charts from the image, and

calculate a real-time resolution value associated with the camera photosensitive surface for each group of testing charts in real time based on each group of testing charts separated from the image, and

wherein the display device is configured to:

receive the real-time resolution value associated with the camera photosensitive surface for each group of testing charts from the processing system, and

display the real-time resolution value for each group of testing charts, so that a user adjusts an installation angle of an optical axis of the lens relative to the camera photosensitive surface in real time based on the real-time resolution value associated with the camera photosensitive surface of the camera for each group of testing charts.

11. The apparatus of claim 10 , wherein each group of testing charts comprises at least one testing stripe set, each testing stripe set comprises a plurality of testing stripes spaced apart from each other, and the distances between the testing stripes change gradually in a direction perpendicular to a spacing direction of the testing stripes.

12. The apparatus of claim 10 ,

wherein each group of testing charts comprises a first testing stripe set and a second testing stripe set;

wherein the first testing stripe set comprises a plurality of first testing stripes spaced apart from each other in a first direction and extending in a second direction perpendicular to the first direction, with the distances between the first testing stripes varying gradually in the second direction; and

wherein the second testing stripe set comprises a plurality of second testing stripes spaced apart from each other in the second direction and extending in the first direction, with the distances between the second testing stripes varying gradually in the first direction.

13. The apparatus of claim 10 , wherein the at least two groups of testing charts comprises five groups of testing charts, wherein four groups of testing charts of the five groups of testing charts correspond to four corners of the camera photosensitive surface and a fifth group of testing charts of the five groups of testing charts corresponds to the center of the camera photosensitive surface.

14. The apparatus of claim 10 , wherein the processing system is configured to:

sample each group of testing charts by row or by column to obtain a plurality of stripe square-wave signals, wherein each group of testing charts is associated with at least one stripe square-wave signal;

perform Fourier transformation on the plurality of stripe square-wave signals to produce spectrum charts, wherein each stripe square-wave signal corresponds to a respective spectrum chart of the plurality of spectrum charts; and

calculate the real-time resolution value associated with the camera photosensitive surface for each group of testing charts based on the spectrum chart of each stripe square-wave signal.

15. The apparatus of claim 14 , wherein the processing system is configured to:

calculate an average frequency amplitude A aver and a characteristic frequency amplitude A t of each stripe square-wave signal based on the spectrum chart of the stripe square-wave signal;

determine whether the characteristic frequency amplitude A t of each stripe square-wave signal satisfies a condition according to the following formula:

A t / A aver >Thres

wherein Thres is a preset threshold; and

for each group of testing charts, determining a resolution value corresponding to the associated stripe square-wave signal to be the real-time resolution value associated with the camera photosensitive surface for the group of testing charts if the characteristic frequency amplitude A t of the associated stripe square-wave signal satisfies the condition.

16. The apparatus of claim 14 , wherein the processing system is configured to:

before performing Fourier transformation on the plurality of stripe square-wave signals, remove a direct-current (DC) component of each stripe square-wave signal through the following operation:

x ′( k )= x ( k )-mean( x ( k ));

wherein x(k) is the stripe square-wave signal before the DC component is removed, mean(x(k)) is the average value of the stripe square-wave signal before the DC component is removed, and x′(k) is the stripe square-wave signal after the DC component is removed.

17. The apparatus of claim 10 , wherein the processing system is configured to rotate the image comprising the at least two groups of testing charts captured by the camera according to the following formula:

{

x

0

=

x

⁢

⁢

cos

⁢

⁢

θ

+

y

⁢

⁢

sin

⁢

⁢

θ

+

m

y

0

=

-

x

⁢

⁢

sin

⁢

⁢

θ

+

y

⁢

⁢

cos

⁢

⁢

θ

+

n

,

where, m=−0.5W cos θ−0.5H sin θ+0.5W 0 ,

n=0.5W sin θ−0.5H cos θ+0,5H 0 ,

x 0 and y 0 represent the horizontal coordinate and the vertical coordinate of a pixel point in the image respectively before the rotation,

x and y represent the horizontal coordinate and the vertical coordinate of the pixel point in the image respectively after the rotation,

H 0 and W 0 represent the height and the width of at least one testing chart of the plurality of testing charts in the image respectively before the rotation,

H and W represent the height and the width of the at least one testing chart in the image respectively after the rotation, and

θ represents rotation angle.

18. The apparatus of claim 10 , wherein the processing system is further configured to:

perform gray processing on the image comprising the at least two groups of testing charts; and

perform morphological filtering on the gray processed image to obtain the testing chart regions in different directions.

19. The method of claim 1 , wherein each group of testing charts in the image comprises more than one testing chart.

20. The apparatus of claim 10 , wherein each group of testing charts presented by the target comprises more than one testing chart.