RU2749363C1 - Device for automated calibration of video cameras of various spectral ranges - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to the field of measuring equipment and relates to a device for automated calibration of video cameras of various spectral ranges. The device consists of a universal test object, the images of which are simultaneously contrasting in the ultraviolet, visible and infrared ranges of the optical spectrum, at least one light source that is switched on during the calibration of cameras that fix the light reflected from the test object, an opaque screen to protect the user's eyes from radiation from the source light and means for adjusting the position of the calibrated camera in the working space with six degrees of freedom.

EFFECT: invention is aimed at providing possibility of calibrating cameras of different spectral ranges and reducing the torque requirements of motorized linear translators and turntables.

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Description

The invention relates to the field of computing and can be used to determine and bring to the specified values the parameters of video cameras of the ultraviolet, visible and infrared (IR) wavelength ranges.

A number of devices for calibrating cameras of different - visible and IR - spectral ranges are known from the prior art, for example: patent CN 204695399, published on June 29, 2015, IPC: G06T 7/00 (2006.01); patent CN 204287725, published 04.22.2015, IPC: G06B 43/00 (2006.01), G01J 5/52 (2006.01); patent CN 204301863, published 04/29/2015, IPC: G01J 5/52 (2006.01), G01M 11/00 (2006.01); patent RU 2672466, published on November 14, 2018, IPC: G06T 7/80 (2017.01).

These devices consist of ordered elements with a priori known spatial coordinates. All of them imply the presence of elements, the images of which are high-contrast at once in several ranges of the optical spectrum, i.e. also have thermal contrast. Camera calibration with the help of such devices (universal test objects) assumes their sequential shooting from several angles. However, none of the above inventions contains in their design means for adjusting the position along the linear and angular coordinates.

The control device for calibrating videogrammetric systems (patent RU 2645432, published 02/21/2018, IPC: G01C 11/00 (2006.01)), selected as a prototype as the closest in terms of a set of features, lacks this drawback. The specified control device contains the actual test object with a plurality of markers, as well as a means for regulating its position in the measurement working space, while the control means is made in the form of a mechanism with six degrees of freedom.

At the same time, the control device of the prototype, when installed indoors, does not allow calibrating cameras in those ranges of the optical spectrum that are practically absent in the spectrum of lighting devices used to illuminate rooms, and are not passed through by glazing windows - for example, cameras in the ultraviolet range of UV-C.

The second disadvantage of the prototype is that when used for automation of motorized mechanisms to ensure the movement of the test object along three angular and three linear coordinates (i.e., with six degrees of freedom) in the case of massive test objects (which, as a rule, and are test objects for the calibration of multi-spectral cameras) it requires the use of motorized linear translators and turntables with a high torque.

The technical problem solved by the creation of the claimed invention is the lack of devices for automated calibration of cameras of various spectral ranges, including ultraviolet.

The technical result of the invention lies in the creation of such a device and is achieved by the fact that the control device for calibration includes sources for illuminating the test object in the required ranges of the optical spectrum, and to protect the user's eyes from the action of radiation from the light sources, it provides for the presence of opaque screens.

Also, in order to reduce the torque requirements of motorized linear translators and turntables used to change the angles of shooting a test object during camera calibration, it is proposed to move and rotate not the test object itself, but the camera, which, as a rule, has smaller him weight and dimensions.

The design of the proposed device for calibration is shown in Fig. 1. It consists of a base 1 (for example, a honeycomb optical plate), on which motorized mechanisms are rigidly fixed to ensure the movement of the camera 2 along three linear (in depth, horizontal and vertical) and three angular (in azimuth, elevation and roll) coordinates : Linear translators 3, 4 and 5 and turntables 6, 7 and 8, respectively. The camera 2 is attached to the turntable using the camera arm 9. On opposite sides of the base 2, there is a universal test object 10 and at least one light source 11 s a wide radiation pattern in at least one of the ranges of the optical spectrum, in which the camera captures not the intrinsic radiation of the test object, but the light reflected from it: ultraviolet, visible, near-IR or short-wave IR. To protect the user's eyes from the radiation of the light source 11, an opaque screen 12 is fixed on the base 1 (for clarity, only its left and rear walls are shown in Fig. 1, and the front and right walls, as well as the cover are not shown). To automate the change of shooting angles, issue commands to capture a frame and save frames with images of the test object, a power and control device 13 is used. Commands and supply voltages from a power and control device 13 are transmitted to camera 2, linear translators 3-5 and turntables 6 -8 for cables 14, 15-17 and 18-20, respectively. Cable 21 is designed to power the electric heater of the universal test object 10.

The device is used as follows. To calibrate multi-spectral cameras using motorized devices 3-5 and 6-8, according to commands from the power supply and control device 13, the angular and spatial position of the calibrated camera 2 is changed so that the universal test object 10 is observed from different angles, and its entire image falls into into the frame of camera 2 and was at least 50% of the area of the frame. By changing the shooting angles so that the images of the universal test object 10 are located both in the central part of the camera frames and at the edges, a series of frames taken from different angles is saved. At each shooting angle (the recommended number of angles is at least 15) in each of the frames, the pixel coordinates of the control points (markers of the test object) are automatically selected, which are then used in the calibration algorithm, for example, according to the method described in (Zhang Z. A Flexible new technique for camera calibration // IEEE Transactions on Pattern Analysis and Machine Intelligence. - 2000. - Vol.22 (11). - P. 1330-1334).

At the same time, to calibrate the cameras fixing the reflected light - UV-C, visible, near-IR and short-wave IR ranges - turn on the light source (s) 11 of the corresponding optical range of the spectrum for forced illumination of the test object 10. To calibrate the cameras of the medium-wave and long-wave IR ranges, fixing their own thermal radiation of the universal test object, switching on the illumination source is not required, since they perceive its own radiation in the wavelength ranges of 3-5 and 8-12 microns, respectively.

Claims (1)

A device for automated calibration of video cameras of various spectral ranges, containing a test object and a means for adjusting the position in the measurement working space with six degrees of freedom, characterized in that it contains a universal test object, the images of which are simultaneously contrasting in the ultraviolet, visible and infrared optical ranges spectrum, at least one light source switched on during the calibration of cameras that fix the light reflected from the test object, and an opaque screen to protect the user's eyes from the radiation of the light source, while the spatial and angular positions are controlled by six degrees of freedom not for the test object , and for the calibrated chamber.

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