CN201277864Y - Inner Orientation Element and Distortion Tester - Google Patents

Abstract

The utility model relates to an internal orientation element and distortion tester applied to a digital aerial camera, which includes a light source and a turntable, and the tester also includes a collimator; on the same optical axis. The utility model provides an internal orientation element and distortion tester with simple structure, convenient operation and high precision.

Description

Inner Orientation Element and Distortion Tester

technical field

The utility model relates to the field of aviation and aerospace photogrammetry, in particular to an internal orientation element and distortion tester applied to a digital aerial camera.

Background technique

Photogrammetry has developed rapidly in the application field of topographic map compilation, gradually forming a photogrammetry technology system and a complex photogrammetry instrument system. In photogrammetry, a photogrammetry camera is used to take pictures of the earth's surface or other ground features from a long distance, and then measure the spatial distribution of the ground features on the photogrammetry instrument. It is an important means of surveying and drawing topographic maps and other special maps, and an important part of remote sensing technology.

There are generally two types of cameras:

One is the traditional film aerial camera. The imaging device uses photosensitive film to record the image. First, a latent image is formed on the photosensitive film, and after developing and fixing, a negative film that is completely opposite to the real object can be formed, that is, a negative film; finally, an image that is completely consistent with the real object can be obtained after re-shooting, developing and fixing. , the positive film.

The second is a digital aerial camera. With the development of charge-coupled device imaging devices (CCD, CMOS), digital space photogrammetry cameras and digital aerial photogrammetry cameras have been successfully developed internationally in recent years. Compared with the traditional film aerial camera, the difference of the digital aerial camera is that the imaging device in the traditional camera - film, is changed to a charge-coupled device imaging device such as CCD or CMOS. At the same time, the digital aerial photography camera has a series of incomparable advantages: (1) It eliminates the process of developing and fixing the film, directly obtains the digital image, simplifies the procedure of post-processing, and saves the cost; (2) In addition to being able to obtain In addition to the geometric position data of the ground target, its multi-spectral image can also be obtained; (3) The error caused by film processing and scanning is reduced, and the accuracy of the obtained digital map is higher. Therefore, digital aerial camera will be the development direction of aerial photogrammetry and will become the main equipment of aerial photogrammetry.

As the key equipment of aerial photogrammetry, digital aerial camera also needs to be calibrated regularly, especially the calibration of internal orientation elements and distortion difference. Whether it is a traditional film-type aerial camera or a digital aerial camera, the specific items that need to be calibrated in the laboratory are: 1. The inner orientation element-the principal distance f _k , the coordinates of the principal point of the image (x ₀ , y ₀ ); 2. Distortion is poor. Therefore, in order to match the promotion and use of digital aerial cameras, it is necessary to study the corresponding calibration method and establish a calibration device.

For the traditional film-type aerial camera, the target pattern plate is used to measure the distortion by detecting the inner orientation element and the distortion difference. The test device is shown in Figure 1, and the test method is as follows: in order to determine the coordinate position of the principal point of the image (x ₀ , y ₀ ), the camera needs to be measured twice during the test process, one for the horizontal direction and one for the vertical direction, and The vertical direction test is actually performed in the horizontal direction by rotating the camera 90°.

Now take the horizontal direction as an example to introduce the specific test method: install the grid plate on the frame plane of the aerial camera, adjust the grid plate to coincide with each frame mark, and illuminate the grid plate with a light source; The object direction of the camera is installed on the turntable facing the measuring telescope, and the camera is adjusted so that the entrance pupil is located at the center of rotation of the turntable. While turning the turntable, use the measuring telescope to observe the image formed by the standard grid plate through the camera, and use the turntable to record the angle corresponding to each image height. After the test in the horizontal direction, rotate the camera 90° to readjust, repeat the above steps, and continue to observe in the horizontal direction. According to the test data in the horizontal and pitch directions and the corresponding data processing formula, the azimuth elements, the coordinates of the main point of the image and the distortion difference in the tested camera are calculated.

Because digital aerial cameras replace traditional photosensitive film with CCD or CMOS detectors, the mature verification methods and verification items of previous film aerial cameras will no longer be applicable. At present, the use of digital aerial photography cameras in our country has just started, and the calibration method of digital aerial photography cameras is still blank. This instrument is to solve the calibration problem of digital aerial photography cameras.

Utility model content

In order to solve the above-mentioned technical problems existing in the background technology, the utility model provides a simple structure, convenient operation and high precision internal orientation element and distortion tester.

The technical solution of the utility model is: the utility model provides an inner orientation element and distortion tester, including a light source and a turntable, and its special feature is that the inner orientation element and distortion tester also includes a collimator; The collimator is located between the light source and the turntable, and placed on the same optical axis as the light source.

The above-mentioned turntable is a two-dimensional turntable.

The above-mentioned two-dimensional turntable is a high-precision digital display two-dimensional turntable.

The above-mentioned high-precision digital display two-dimensional turntable is a high-precision digital display two-dimensional turntable with a 27-bit shaft encoder and a resolution of 0.01″.

The above-mentioned light source is a point light source, a laser light source or a surface light source.

The utility model has the advantages of:

1. Simple structure. The utility model only needs a parallel light pipe, a turntable and a light source to realize the calibration of the camera, which greatly simplifies the structure of the original internal orientation elements and the distortion tester.

2. Easy to operate. The utility model adopts a high-precision digital display two-dimensional turntable, which can be controlled by a computer to achieve precise positioning, and the positioning accuracy is better than 2". The tester can simultaneously measure different Distortion data under azimuth and elevation angles is convenient for operators, saves time and effort, and greatly improves measurement efficiency.

3. High precision. The precision turntable adopted by the utility model has high precision and stable performance, and can realize precise positioning, and the total precision of the turntable is better than 0.7″; the image processing software performs histogram equalization, digital filtering, and edge enhancement on the images recorded by the aerial camera , optimal threshold selection and other algorithms to remove noise from the image and make the target clearer. At the same time, the sub-pixel subdivision technology is adopted, and the window image is enlarged and displayed accordingly. The center of mass algorithm is used to accurately interpret the coordinate position of the star point target to obtain a 1/10 image. The resolution of the element, the measurement accuracy is greatly improved.

4. Data processing is convenient and quick. The image processing software can directly read the angle information of the turntable and the coordinate data of the star point target, and finally calculate the azimuth elements, the coordinates of the main point of the image and the distortion difference in the measured camera quickly and accurately according to the corresponding data processing formula.

5. Good real-time performance and strong extension function. The utility model has a simple structure, and is convenient for many people to observe the whole testing process at the same time. At the same time, not only can the distortion of the optical system be tested with high precision, but also the focal length and imaging quality of the system under test can be measured in real time.

Description of drawings

Figure 1 is a schematic diagram of the detection structure of a traditional film-type aerial camera;

Fig. 2 is a schematic structural view of a preferred embodiment of the present invention.

Detailed ways

Referring to Fig. 2, the utility model provides a tester for internal orientation elements and distortion, including a light source 1 and a turntable 3, and the tester for internal orientation elements and distortions also includes a collimator 2; the collimator 2 is located between the light source 1 and the turntable 3 between, and placed on the same optical axis 5 as the light source 1.

The turntable 3 may be a two-dimensional turntable or a high-precision digital display two-dimensional turntable. The high-precision digital display two-dimensional turntable adopts a 27-bit shaft encoder and the resolution can reach 0.01". And the light source 1 is a point light source, a laser light source or other surface light sources.

When the utility model is in use, its specific test method is: install a star point target at the focal plane of the collimator 2 and illuminate it with the light source 1, form an infinite distance target through the collimator 2, and take the measured digital aerial photography The camera 4 is fixed on the two-dimensional turntable, and the installation position of the digital camera 4 under test is adjusted so that the entrance pupil is located at the rotation center of the digital display turntable, and the position of the collimator 2 is adjusted so that the camera is aligned with the collimator 2.

The test is divided into 2 steps:

Step 1: Test of Azimuth Direction:

Align the digital aerial camera 4 under test with the collimator 2, lock the pitch angle of the two-dimensional turntable, rotate the azimuth angle of the two-dimensional turntable to obtain the standard angle in the azimuth direction, and use the digital aerial camera 4 to collect the collimator 2. For the image of the star point target on the image plane, the coordinate position of the star point image is interpreted by the image processing software, and the angle value of the precision turntable is recorded.

Step 2: Test of pitch direction:

Align the digital camera 4 under test with the collimator 2, lock the azimuth angle of the two-dimensional turntable, rotate the pitch angle of the two-dimensional turntable to obtain the standard angle in the pitch direction, and use the digital camera 4 to collect the stars at the image plane of the collimator. For the image of the point target, the coordinate position of the star point image is interpreted by the image processing software, and the angle value of the precision turntable is recorded.

Based on the test data of the precision turntable in the azimuth and pitch directions and the coordinates of the star point target, the inner azimuth elements, the coordinates of the main point of the image and the distortion difference of the tested camera are calculated according to the inner azimuth elements and the distortion difference data processing formula.

Claims (5)

1, a kind of elements of interior orientation and distortion tester comprise light source and turntable, it is characterized in that: described elements of interior orientation and distortion tester also comprise parallel light tube; Described parallel light tube between light source and turntable, and and light source place on the same optical axis.

2, elements of interior orientation according to claim 1 and distortion tester is characterized in that: described turntable is two-dimentional turntable.

3, elements of interior orientation according to claim 2 and distortion tester is characterized in that: described two-dimentional turntable is a high precision digital display two dimension turntable.

4, elements of interior orientation according to claim 3 and distortion tester is characterized in that: described high precision digital display two dimension turntable is to adopt 27 shaft-position encoders and resolution can reach 0.01 " high precision digital display two dimension turntable.

5, according to claim 1 or 2 or 3 or 4 described elements of interior orientation and distortion testers, it is characterized in that: described light source is pointolite, LASER Light Source or area source.

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