CN1558262A - 180° Large Field of View Ring Panoramic Staring Imaging Method - Google Patents

Abstract

The invention discloses a circular panoramic staring imaging method with a large field of view of 180°. It adopts the cylindrical plane projection method, uses the second-reflection annular lens for the first imaging, realizes the annular panoramic staring imaging, uses the relay lens for the second imaging, obtains the real image, and uses the planar photoelectric imaging device to receive and display the three-dimensional space. The depth of field is a panoramic gaze image of infinity. Advantages of the present invention: This is a 180° large field of view, 360° circular panoramic staring imaging method without moving parts, with small size, light structure, infinite depth of field, and an optical method that can clearly image distant and near objects without focusing , can be used for robot panoramic vision, tunnel, pipeline inner wall inspection, medical endoscopic imaging and panoramic security real-time monitoring such as bank traffic, and can also be applied to 360° panoramic photography.

Description

180° Large Field of View Ring Panoramic Staring Imaging Method

Technical field

The invention relates to a circular panoramic staring imaging method with a large field of view of 180°.

Background technique

Figure 2 is a schematic diagram of the traditional optical imaging method-central projection method, which is a model of visual optics. When the human eye observes the surrounding scenery, visual optics follows the principle of central projection, that is, objects of the same size are closer to the eyes and appear to be It is larger than when the distance is far away, that is, there is a phenomenon that the distance is small and the near is large. Make the human eye feel far and near, and the three-dimensional space is presented in front of our eyes. In order to compress the three-dimensional space into a two-dimensional plane. This is the central projection method. If you want to use a picture to describe the three-dimensional space, you should also draw the distant scenery smaller and draw the nearby scenery larger. And as the distance increases, the observed scenery will become smaller and smaller, and finally disappear slowly.

This method of projecting a three-dimensional space onto a two-dimensional plane is called the central projection method. The point at which the scene finally disappears is called the vanishing point. The vanishing point of the central projection method is on a straight line, which is what people call the horizon. Optical imaging (photography or photography) follows the central projection method to achieve. Since the vanishing point of the central projection method is on a straight line, in order to obtain a 360° panoramic image, an infinite image plane is required, which is actually impossible. In order to ensure a 360° field of view, the optical system must be rotated, so that the entire space cannot be observed at the same time, but can only be scanned in the order of rotation of the imaging system, and the scenes of each area are observed in turn, and then stitched into a panoramic image . Therefore conventional optics cannot obtain panoramic imaging.

The optical system designed according to the central projection method is based on the chief ray imaging of the field of view. According to the classification of the field of view, the photographic objective with a field of view of 60° or more is called a wide-angle objective, and the photographic objective with a field of view of 90° or above is called an ultra-wide-angle objective. For example fisheye lens. Similarly, because the fisheye lens also follows the central projection method, as the field of view expands, the viewing plane becomes curved, and the corresponding relationship between objects and images is complicated. Applications such as security monitoring. It can be seen that the traditional optical system following the central projection method has insurmountable defects when applied to large field of view and panoramic imaging.

Contents of Invention

The purpose of the present invention is to provide a 180° large field of view annular panoramic staring imaging method.

It adopts the cylindrical plane projection method, uses the second-reflection annular lens for the first imaging, realizes the annular panoramic staring imaging, uses the relay lens for the second imaging, obtains the real image, and uses the planar photoelectric imaging device to receive and display the three-dimensional space. The depth of field is a panoramic gaze image of infinity.

Said to adopt the cylindrical plane projection method, and use the annular lens of secondary reflection for the first imaging: it is the first imaging of cylindrical plane projection using the circular lens of spherical secondary reflection, the image is a virtual image, and the imaging method There is no fixed entrance pupil, and it is replaced by a virtual entrance pupil. Each field of view is imaged by a circular aperture, and each object point in the direction of the field of view is formed on the same image point, realizing infinite depth of field.

The relay lens is a spherical relay lens. The planar photoelectric imaging device is CCD or CMOS.

Advantages of the present invention: This is a 180° large field of view, 360° circular panoramic staring imaging method without moving parts, with small size, light structure, infinite depth of field, and an optical method that can clearly image distant and near objects without focusing , can be used for robot panoramic vision, tunnel, pipeline inner wall inspection, medical endoscopic imaging and panoramic security real-time monitoring such as bank traffic, and can also be applied to 360° panoramic photography.

Description of drawings

Fig. 1 is a schematic diagram of a circular panoramic staring imaging optical system with a large field of view of 180°;

Fig. 2 is a schematic diagram of traditional optical center projection method;

Fig. 3 is a schematic diagram of the cylindrical plane panoramic projection method;

Fig. 4 is a schematic diagram of the optical system for the first imaging of the annular panorama;

Figure 5 is a schematic diagram of the optical system for the second imaging of the annular zone of the field of view, in which (a) a schematic diagram of the secondary imaging of the annular lens image, and (b) a schematic diagram of the imaging area;

Figure 6 is a photo of circular panoramic staring imaging, in which (a) indoor far-field and near-field imaging, (b) cylinder inner wall text imaging, (c) scene panoramic imaging.

Detailed ways

The 180° large field of view annular panoramic imaging method uses a cylindrical plane projection imaging method to replace the central projection imaging method in traditional optics, and is a new concept imaging method.

If the three-dimensional space is regarded as a cylinder instead of a spherical body, the image can be expanded into a plane by the method of stretching, and the three-dimensional cylinder is represented by a two-dimensional plane. This projection method is called cylindrical planar projection, and it is the basis for the imaging of annular panoramic lenses. In cylindrical planar mapping, all parallel rays focus on a point, and the vanishing point is the center of the circle. In the traditional central projection method, parallel lines of different directions are focused on different points of a (horizontal) line. Figure 3 is a schematic diagram of the cylindrical planar projection and shows the defined angles that determine the field of view. In the cylindrical plane projection method, the part that can be imaged is the three-dimensional area formed by the two sides of the α angle rotated 360° around the optical axis z. This area is projected onto a circle on the 2D image plane. However, the conical area formed by rotating the two sides of the cone angle 2β around the z-axis for 360° cannot be imaged. This area corresponds to a circle with an inner diameter on a two-dimensional plane as a blind area. Obviously, increasing α and decreasing β can increase the imaging field of view, but the values of these two parameters are limited by the refractive index of existing glasses. The circular panoramic image corresponds to the alpha value that can be obtained, and it is a 360° panoramic staring image. The current design can reach α=60°. Therefore, this method can obtain panoramic imaging with a field angle of 180° and a circular imaging area of 60°×360°.

Fig. 4 is the optical system of annular panoramic imaging, which is the optical realization of the cylindrical plane projection method, and the imaging object is the inner surface of a cylinder (A is the converging point of rays 1, 2, and B is 3, 4, and A and B are on the inner surface of the cylinder above), when _the cylinder tends to infinity, it is the panoramic imaging of the surrounding scenery, and the incident light in the AB area will become the outgoing light 1′, 2 ′, 3′, 4′, and the converging point A′ of 1′, 2′, the converging point B′ of 3′, 4′ is the imaging (virtual image) of the two points A and B, so that the three-dimensional cylindrical surface realizes the For the projection of a two-dimensional plane, the projection plane I is a virtual image plane, and the virtual image plane I is the first imaging of the annular panoramic imaging. A relay lens is added behind the annular lens to enlarge the virtual image surface I into a real image and realize the observation display. Therefore, the optical system of the annular panoramic imaging is shown in Figure 1, which is the secondary imaging process of the annular panoramic method.

The key of annular panoramic imaging is how to ensure the clarity of three-dimensional space imaging under a large field of view. The present invention uses a spherical system to realize clear imaging of annular panoramic imaging. The method is as follows:

(1) Ensure the ideal image height H=f'tgθ (f'-focal length, θ-field angle), while the actual image height L=H=f'θ, when the field angle θ increases, the actual image height f ′θ is smaller than the ideal image height f′tgθ determined by geometric optics, which is its θ/tgθ times, and its linear distortion is:

ΔH=f'(tgθ-θ)

The relative distortion is:

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; tg\&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{\mathrm{<span\; class="notranslate">\; tg\&theta;</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

The ring-shaped panoramic spherical system uses a light stop and coma lens to produce distortion, and its distortion is expressed by the aberration coefficient, then

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; V</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; \&prime;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; tg\&zeta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; J</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; pk</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; up</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>$

In the formula, n-material refractive index, u-ray angle, J-Lagrangian invariant, k and p=1, 2, 3.... Therefore, the aberration generated by the spherical annular lens is compensated by the coma, distortion and chromatic aberration of magnification generated by the relay imaging system to achieve clear imaging (Figure 6 is an imaging photo).

(2) The clear aperture of annular panoramic imaging is related to the field of view angle. It is an annular aperture imaging of the field of view. Its aperture does not need to have a fixed entrance pupil, but is only restricted by a virtual entrance pupil. The virtual entrance pupil is at the On the virtual image plane I of one imaging (Fig. 2), the light rays of each field of view have a strict direction, as shown in Fig. 5, when the light beam passes through point A and point B of the same field of view γ, point A and point B The image points on the image plane are the same point, so when the annular panoramic lens images the external field of view, point A and point B are equally clear, that is, the depth of field is infinite.

(3) The evaluation function of the annular panoramic imaging quality is expressed by the following formula

${\mathrm{<span\; class="notranslate">\; MF</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

In the formula, W _i is the weighting coefficient of the i-th factor, V _i is the actual value of the i-th factor, and T _i is the target value of the i-th factor. The system of the present invention uses the MF ² value to evaluate the imaging quality.

Figure 6 is three examples of circular panoramic imaging. Photo 1 in the figure is the shooting situation with the lens placed horizontally (that is, the position in Figure 4). The distant objects (instrument) and near objects (portraits) in the photo are naturally clear without focusing. Figure 2 is the imaging of the characters on the inner wall of the cylinder. When the lens is placed vertically, the 360° inner view can be imaged in a panoramic manner, as shown in Figure 3, and then the non-linear processing of the mapping is performed by a computer to obtain a panoramic undistorted photo.

Claims (4)

1. A visual field near or surpass 180 ° annular panoramic staring imaging method, it is characterized in that adopting cylinder plane projection method, lens ring with secondary reflection is done imaging for the first time, realize the annular panoramic staring imaging, do imaging for the second time with relay lens, obtain real image, connect with plane photoelectricity image device and receive And demonstration three dimensions, the depth of field is that the panorama of infinity is stared picture.
2. 2. approaching or the method for panoramic imaging in a kind of visual field according to claim 1 above 180 °, it is characterized in that said employing cylinder plane projection method, do imaging for the first time with the lens ring of secondary reflection: be to adopt the lens ring of global face secondary reflection to do the imaging first time of cylinder plane projection, this similarly is the virtual image, and this formation method does not have fixing entrance pupil, replace with virtual entrance pupil, each visual field is by the annular aperture imaging, each object point on the direction of visual field all becomes on same picture point, realizes depth of field infinity.
3. 3. a kind of visual field according to claim 1 is approaching or surpass 180 ° method for panoramic imaging, it is characterized in that said relay lens is the relay lens of global face.
4. 4. a kind of visual field according to claim 1 is approaching or surpass 180 ° method for panoramic imaging, it is characterized in that said plane photoelectricity image device is CCD or CMOS.

Images