The field of view of a fish-eye lens
A fisheye lens was a lens with a focal length of about 6 - 16mm and a field of view close to or equal to 180°. It was a type of ultra-wide-angle lens with a field of view close to or equal to 180°. For modern optical applications, the field of view of the fisheye lens often needed to exceed 180 degrees. In this case, it was necessary to switch to a non-linear projection, introducing barrel distortion to project the hemisphere field of view onto a limited flat target. There were four main projection methods, namely, isomedic, isomedic, orthodoxy, and holographic. The most common was isomedic projection. Read more exciting novels for free
Fish-eye lens is
A fisheye lens was a lens with a focal length of about 6 - 16mm and a viewing angle close to or equal to 180°. It was a type of ultra-wide-angle lens. Its front lens was shaped like a parabola and protruded to the front of the lens, which was similar to the eyes of a fish, hence its name. The concept was proposed and developed in 1906. In the 1920s, it was used for the study of cloud formation in meteorology. Robin Hill was the first person to truly create a fisheye lens and use it for commercial use. Mass production began in the 1960s. It was usually composed of a front group of imaging lenses and a rear group of correction lenses. It was divided into half-frame fisheye lenses and full-frame fisheye lenses. It was first used in photography to create artistic photos with a large field of view and large distortion. It was also widely used in fields that required wide-angle imaging, such as surveillance, dome imaging, aerospace cameras, and other industrial, medical, and scientific research fields. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Is the fish-eye lens a concave lens or a concave lens?
Fish-eye lenses were usually composed of a front group of imaging lenses and a rear group of correction lenses. The front group of imaging lenses was generally a concave lens for imaging, but the entire fish-eye lens was a complex optical system. It was not only composed of simple concave lenses or concave lenses, but also through the combination of multiple lenses to correct aberrations, aberrations, and other problems to achieve its special imaging effect, such as the angle of view being close to or equal to 180°. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Fish-eye lens for the seascape
The fisheye lens could be used to capture seascapes and had a unique imaging effect. For example, the AF-S fisheye Nikkor 8 - 15mm f/3.5 - 4.5E ED lens used three pieces of low-dispersion (ED) glass lenses to effectively reduce the horizontal color difference that caused the color halo. It could also achieve high sharpness and contrast at the edge of the image, which could provide good image quality for landscape photography (including seascape). The filter slot was located at the opening of the lens mount, which could be inserted after cutting the third-party filter insert on the market. It provides filter support for seascape shots. There was also a fish-eye lens suitable for shooting seascapes. Its maximum aperture was only f/8, and the viewing angle reached 162°. It used four sets of four optical structures, and the lens was coated with seven layers of RMC to effectively reduce ghostly shadows and glare. When using the fisheye lens to shoot the seascape, you can use its unique perspective. The closer the line to the edge, the more exaggerated the distortion. If you arrange some of the seascape elements that you want to highlight at the edge of the picture, you can exaggerate its distortion, thus forming a special picture effect. If you arrange the main body in the center of the picture, it will be more horizontal. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
computer fish-eye lens
A fisheye lens was a lens with a focal length of about 6 - 16mm and a viewing angle close to or equal to 180°. It was a type of ultra-wide-angle lens. Its front lens protruded toward the front of the lens in a parabola shape, similar to a fisheye. If a computer wanted to use a fisheye lens, it might be used for external cameras and other devices to achieve special shooting effects, such as creating artistic images with large field of view and large distortion. It could be used for creative photography, surveillance, or specific industrial, medical, scientific research, and other fields that required wide-angle imaging. Fisheye lenses were first used in photography. They were developed in 1906 and used to study the formation of clouds in the 1920s. They were mass-produced in the 1960s. They were divided into half-frame fisheye lenses and full-frame fisheye lenses. They were usually composed of a front group of imaging lenses and a rear group of correction lenses. At present, there were also a variety of fisheye lens products that were suitable for different camera mounts. While ensuring the image quality and other functions, they were also developing in the direction of light and portable. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Distortion correction of fish-eye lens
Fish-eye lens distortion correction aims to reduce or eliminate the image distortion effect caused by fish-eye lenses. When correcting the distortion of the fisheye lens, the core was to solve a "good" remap matrix, which rearranged some of the original image's pixel-points (or intervening points) and "pieced" them into a rectangular image."Good" was linked to the final requirement, and different tasks often used different correction/distortion solutions. For example, in the smart security industry, whether it was a monocular camera or a monocular camera, the images captured would have distortions, which was the same as the distortion correction principle of a fisheye camera. For monocular cameras, in order to obtain the corresponding relationship between the camera's coordinate system and the three-dimensional world coordinate system, the barrel distortion and pillow distortion of the camera needed to be corrected. For binocular cameras, in order to do epipolar line alignment and realize depth estimation, the output of the two cameras needed to be transformed into the same coordinate system. Teacher Zhang Zhengyou's chessboard correction method estimated the internal and external parameters and distortion coefficient of the camera through the position coordinates of the marker, and then calculated the remap matrix. This method had a good correction effect for monocular and binocular cameras. In terms of practical operations, fisheye correction can also be performed using python language (only relying on the opencv-python package and numpy package), and fisheye distortion correction can also be performed from code examples such as PILimport Image. In addition, the distortion correction function based on digital image processing was also applied to the fisheye lens correction. This solution required rearranging the arrangement of the elements, but for the ultra-wide system where the edge image quality itself was a big problem, it might lead to the image quality of the most edge area being worse. Some equipment would use the image field redundant design and the sensor to perform the redundant matching of the elements to reduce the side effects of the digital correction. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Full circle fish-eye lens
The reference did not mention anything about the full round fisheye lens. Sorry, I don't know how to answer based on the information I found. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Full-frame fish-eye lens
A full-frame fisheye lens was a type of fisheye lens. The fisheye lens was a type of ultra-wide-angle lens with a focal length of about 6 - 16mm and an angle of view close to or equal to 180°. Its front lens was shaped like a parabola and protruded toward the front of the lens. The functions of the full-frame fisheye lens included: 1. ** Photographic Creation **: Can create artistic photos with a large field of view and large distortion. It can display unique visual effects and shoot images with extremely wide angles of view. The effect of the images is beyond the regular and fixed forms that people see in their daily lives. 2. ** Industrial field **: In some industrial scenes that require wide-angle imaging, such as the monitoring field, it can cover a large monitoring range. 3. ** Scientific research **: It can be applied to the study of cloud formation in Meteorology. It can also be used in aerospace cameras to help obtain wide-angle image information. 4. ** Medical field **: Able to provide wide-angle imaging in specific medical imaging scenarios. 5. ** In terms of imaging, a full-frame fisheye lens can meet the requirements for scenes that require large viewing angles, such as dome imaging. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Fish-eye lens imaging theory
The imaging theory of the fisheye lens was based on its special optical structure design. The fisheye lens had a large spherical curvature, similar to the spherical crystal of a fisheye, and the imaging plane was closer to the lens. The visual effect was similar to a fish observing things on the surface of the water. When the fish was close to the surface of the water, the angle of view could reach a wide angle of nearly 180°. This phenomenon was based on the principle of total reflection and optical reversibility. In terms of structure, the front lens of the fish-eye lens protruded from the front in a parabolic shape in order to maximize the camera angle. It was generally believed that lenses with a focal length of 16mm or shorter were fisheye lenses. However, in engineering, lenses with a viewing angle of more than 140 degrees were collectively referred to as fisheye lenses. In fact, there were also lenses with a viewing angle of more than 270 degrees. In terms of imaging mode, the M12 fisheye lens (180°) generally used vertical or horizontal in-cut imaging mode (mode 1 Circular Fisheye, mode 3 Full Horizontal). At the same time, fisheye lens imaging relied on artificially introducing a large number of barrel distortions to obtain a large field of view, so that it could obtain image information with a large field of view. However, except for the shape of the object in the center of the image, the other parts that should be straight lines had a certain degree of distortion. When matching an image sensor with a fisheye lens, a 1:1 or 4:3 image sensor was generally selected to maximize the use of effective pixelation. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Fish-eye lens for piano teaching
Using a fish-eye lens in piano teaching has certain advantages. The fish-eye lens had a large angle of view and could accommodate more scenes. It could adapt to the needs of shooting in a small space. In a piano teaching scene, such as an online piano lesson, the fish-eye lens could be used to let students see more details of the teaching environment, such as the teacher's overall performance posture, the piano's overall appearance, and so on. However, there were some problems with using a fisheye lens. Due to the distortion of the image, the straight lines around the screen would be bent. When shooting piano teaching content, if you need to show some flat music score or the straight arrangement of the keys, there may be distortion. Therefore, when using it, one had to pay attention to the selection of the shooting angle and content. For example, the subject that needed to be highlighted (such as the teacher's hand movements, etc.) could be placed in the center of the lens because the straight line in the center of the lens could maintain its original state. This was also the brightest and clearest part of the photo to reduce the impact of distortion on the teaching content. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>
Fish-eye lens correction and stitching
The correction and stitching of the fisheye lens involved the following contents: ** 1. Fish-eye lens correction ** 1. ** Extracting the camera's parameters ** - First of all, the fisheye camera's parameters had to be obtained, including the lens distortion model and the camera's internal and external parameters. These parameters could describe the optical characteristics of the fisheye lens and the camera's imaging geometry. 2. ** Distortion correction ** - The distortion in the image was corrected using the obtained camera correction parameters. This was usually achieved by re-projecting each of the elements to make the lines and shapes of the image more straight and natural. 3. ** Perspective transformation (for the corrected shape)** - The image after fisheye correction would often become a circle or hemisphere, so perspective transformation was needed to restore it to a standard rectangular or square shape. This was achieved by adjusting the projection method of the image. 4. ** Image Cropping ** - After the perspective transformation, the image might be distorted or have black edges. Image trimming could remove invalid areas and edges, ensuring that the image was complete and without distortion. In addition, there were other methods of correction: - ** Polar line correction method (for paired images)** - This was a common technique in computer vision. Before use, feature points were extracted from each image using algorithms such as SIFT, URF, and ORB. Then, these feature points were matched to find the corresponding points in the two images. Then, the epipolar line between the two images was calculated using the essential matrix or the fundamental matrix. Finally, each image was corrected by the epipolar line. The correction process included calculating the epipolar lines for each image, calculating the rotation matrix to align the epipolar lines, rotating and translating the images to align the epipolar lines, and trimming and zooming the images to make the distance between the pixels equal. This method is helpful to improve the accuracy and efficiency of disparity calculation and 3D matching. - ** Sphere Projection Method ** - The basic idea was to expand the fisheye image from a spherical surface into a flat image, so that the straight line in the image would still be a straight line after the expansion, thereby eliminating the distortion caused by the fisheye lens. The specific steps were: First, select the appropriate center of the sphere (such as the position of the optical axis of the fisheye lens or the center of the front end), establish a spherical coordinate system (the longitude and latitude correspond to the x and y coordinates of the image respectively), and then map each point of the fisheye image to the spherical surface according to its spherical coordinates to obtain a spherical image. Then, expand the spherical image into a planar image (using methods such as orthonormal or oblique projection), and finally perform post-processing such as distortion removal, trimming, rotation, etc. on the planar image to obtain the corrected image. There was also a correction method that involved self-supervised pre-training: - Firstly, a fish-eye image data set was constructed and the fish-eye image was divided into 2D image blocks. A self-supervised pre-training module was used to perform self-supervised pre-training to extract the fine-grained distortion representation of the fish-eye image. Then, the representation was used to learn the full-scale map flow through the fish-eye image correction module, and the corrected fish-eye image pair was obtained. ** 2. Fisheye lens stitching ** 1. ** Image Capture * - Using multiple fisheye lenses to capture overlapping images, it was necessary to ensure that there was a certain overlap between adjacent images so that subsequent image stitching could be carried out. 2. ** Image correction ** - The image captured by each fisheye lens is corrected and converted into a planar image. The correction algorithm such as the polar line correction method or the spherical projection method can be used. 3. ** Steps to Mosaic Images ** - Characteristic point matching: detect the key points in the image and match these key points between different images. - Image Fusion: Fusing the matched images to obtain a complete panoramic image. 4. ** Post-processing ** - After the mosaic, the panoramic image was adjusted and post-processed, such as cutting, color correction, and distortion removal. In addition, there was another fisheye image correction stitching method: - Firstly, a fish-eye image data set is constructed and divided into 2D image blocks. Self-supervised pre-training is used to extract a fine-grained distortion representation to correct the fish-eye image to obtain a corrected fish-eye image pair. The corrected fish-eye image pair is divided into a target image and a reference image, and the target image's picture element is relocated to the reference image plane by using a map.(The two-dimensional map is directly estimated for the overlapping region in the target image, and the loss of the non-overlapping region is regularized to obtain the target image after the map is obtained). Finally, the target image after the map and the reference image are fed to the Siamesemae network to be mixed to generate the final panoramic mosaic image. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>