CN209446767U - Radiant correction apparatus and system - Google Patents

Abstract

The utility model discloses a kind of radiant correction apparatus and system, the radiant correction device includes: controller, image-forming module；The controller is electrically connected with the image-forming module；The controller is for sending acquisition instructions up to the image-forming module；The image-forming module is used to obtain reflected image when receiving the acquisition instructions and is sent to the controller.The utility model is able to achieve the imaging device of multispectral camera while operation exposure, under environment locating for the airborne narrow bandwidth multispectral camera of synchronous acquisition, the reflected image of corresponding wave band, and then obtain its spoke luminance data, and the radiation characteristic of the environmental images according to acquired in spoke luminance data amendment multispectral camera, realize the accurate radiant correction to image data.

Description

Radiation correction device and system

Technical Field

The utility model relates to an image sensor's radiometric calibration field, in particular to be applied to unmanned aerial vehicle's machine carries multispectral camera's of narrow bandwidth imaging module's radiometric calibration device and system.

Background

The radiometric correction of the remote sensing data is a basic link of the quantification of the remote sensing data, and the relationship between the actual radiometric value of the corresponding pixel and the ground object of the imaging module (image sensor) and the relative value of the imaging module can be obtained only through the radiometric correction, so that the calculation result is verified and corrected.

Currently, the most widely used radiation calibration method is to use the radiation characteristics of a known standard reflector to correct the radiation characteristics of a target to be measured, or use a surface feature spectrometer to obtain the surface feature reflectivity and solar irradiance, so as to achieve the purpose of radiation correction. However, because the flight height of the light and small unmanned aerial vehicle is low, the carried imaging module has a small picture, and if the radiation calibration method is used, a large-area reflecting plate needs to be laid.

The Sequoia multispectral sensor developed by Parrot company in France is provided with a sunlight sensor which can be arranged at the top of an unmanned aerial vehicle body, so that irradiance values corresponding to four wave bands of the Sequoia multispectral sensor can be obtained, and airborne real-time correction is realized. However, the fish-eye lens of the sunlight sensor has a large field angle, so that glare appears when the observation angle is directed to the solar altitude, and the sum of irradiance of all light sources obtained by the sunlight sensor does not represent ambient light components, so that the correction error is large.

SUMMERY OF THE UTILITY MODEL

The to-be-solved technical problem of the utility model is to provide a radiation correction device and system in order to overcome the great defect of method error that carries out the correction to the environment image that unmanned aerial vehicle gathered among the prior art.

The utility model discloses an above-mentioned technical problem is solved through following technical scheme:

a radiation correction device, the radiation correction device comprising: a controller, an imaging module;

the controller is electrically connected with the imaging module;

the controller is used for sending a collection instruction to the imaging module;

the imaging module is used for acquiring a reflection image and sending the reflection image to the controller when receiving the acquisition instruction.

Preferably, the radiation correction apparatus further comprises:

a reflector body provided with a diffuse reflection plate;

the incident body and the reflecting body form an included angle;

the imaging module is arranged on the incident body and is positioned on one side close to the diffuse reflection plate;

the diffuse reflection plate is used for reflecting the light source to the imaging module.

Preferably, the radiation correction device further comprises a connecting device;

two ends of the connecting device are respectively connected with the reflecting body and the incident body;

the connecting device is used for adjusting an included angle between the reflecting body and the incident body.

Preferably, the included angle ranges from 30 degrees to 45 degrees.

Preferably, the imaging module comprises a photosensitive sensor and a plurality of imaging subunits;

each imaging subunit includes: a filter, an imaging fiber and a microlens;

and the light source reflected by the diffuse reflection plate passes through the filter, the imaging optical fiber and the micro lens to reach the photosensitive sensor.

Preferably, the imaging module comprises a main imaging unit and a plurality of single-channel imaging units;

the plurality of single-channel imaging units are dispersedly arranged around the main imaging unit;

the main imaging unit comprises an imaging objective lens, an anti-aliasing filter, an infrared filter, a micro lens, a Bayer filter and a photodiode, and a light source reflected by the diffuse reflection plate passes through the imaging objective lens, the anti-aliasing filter, the infrared filter, the micro lens and the Bayer filter to reach the photodiode;

the single-channel imaging unit comprises a filter, an imaging objective lens, a parallel light mirror and a photodiode, and a light source reflected by the diffuse reflection plate passes through the filter, the imaging objective lens and the parallel light mirror to the photodiode.

Preferably, the reflection body is provided with a chute, and the diffuse reflection plate slides in and is fixed on the reflection body through the chute.

A radiation correction system, the radiation correction system comprising: a server and the radiation correction device of any one of the above;

the server is in communication connection with the radiation correction device and the unmanned aerial vehicle to be corrected;

the server is used for sending the acquisition instruction to the radiation correction device when the distance between the radiation correction device and the unmanned aerial vehicle is within a preset range.

The utility model discloses an actively advance the effect and lie in: the utility model discloses can realize multispectral camera's image device when the operation is exposed, under the environment that multispectral camera of synchronous acquisition machine carrier narrow bandwidth was located, the reflection image of corresponding wave band, and then acquire its radiance value data to revise the radiation characteristic of the environment image that multispectral camera acquireed according to this radiance value data, realize the accurate radiation correction to image data.

Drawings

Fig. 1 is a first structural schematic diagram of a radiation correction device according to embodiment 1 of the present invention.

Fig. 2 is a second schematic structural diagram of a radiation correction device according to embodiment 1 of the present invention.

Fig. 3 is a schematic block diagram of a radiation correction apparatus according to embodiment 1 of the present invention.

Fig. 4 is an installation diagram of the radiation correction device according to embodiment 1 of the present invention.

Fig. 5 is a schematic block diagram of a radiation correction system according to embodiment 2 of the present invention.

Detailed Description

The present invention will be more clearly and completely described below with reference to the accompanying drawings.

Example 1

The present embodiment provides a radiation correction device suitable for an imaging module of an onboard narrow bandwidth multispectral camera on an unmanned aerial vehicle, as shown in fig. 1-3, the radiation correction device comprising: a controller 6, an imaging module 3, a reflecting body 4, an incident body 2 and a connecting device 5. The controller 6 is electrically connected to the imaging module 3. The reflecting body 4 and the incident body 2 are connected by a connecting means 5. The imaging parameters, specifications and performances of the imaging module 3 adopted by the radiation correction device are the same as those of the imaging module to be corrected on the unmanned aerial vehicle.

The reflector body 4 is provided with a diffuse reflection plate 1, which is a standard diffuse reflection plate with certain lambertian characteristics and is used for reflecting light sources in the environment, namely sunlight. Lambertian characteristics refer to that the radiation brightness of a radiation surface source emitted to each direction is different and directional, and if the radiation brightness does not change along with the direction x (x is the intersection angle between the radiation brightness direction and the plane normal), such a radiation body is called a lambertian body. At present, the diffuse reflection plate coating uses common composite diffuse reflection coating materials including spectra, Infragel, Permaflect, etc., the main components of which include barium sulfate, polytetrafluoroethylene, water-based ethane and other synthetic chemical components, and different materials have different reflectivities.

The reflecting body is provided with a sliding chute, the diffuse reflection plate slides in through the sliding chute and is fixed on the reflecting body, and similar to a drawer type structure, a user can replace standard diffuse reflection plates with different reflectivity at any time according to application requirements of different scenes.

The incident body is used for installing the imaging module, the imaging module is located on one side close to the diffuse reflection plate, namely the imaging module faces the diffuse reflection plate, and the imaging module can receive the light source reflected by the diffuse reflection plate.

Specifically, in this embodiment, the imaging module may adopt a dot matrix imaging array (see fig. 1) or an area matrix imaging array (see fig. 2), which may be selected by a user. The lattice imaging device is light and convenient to integrate because the optical fiber bundle is small in size; the area array imaging device has the advantages that the composition and the imaging performance of the slave device are consistent with those of an airborne terminal, so that the influence caused by system difference can be reduced in data processing, and the reliability is high.

The dot matrix imaging array includes a photosensor and a plurality of imaging subunits 31. Each imaging subunit includes: a filter, an imaging fiber and a micro lens. The imaging subunits are dispersedly arranged on the incident body, the imaging optical fibers are perpendicular to the incident body, and a certain included angle is formed between the incident ends of the imaging optical fibers and the normal vector of the diffuse reflection plate. The central axis of each imaging optical fiber is parallel to the central axis of the photosensitive sensor. The interval between adjacent imaging subunits is determined according to the field angle of the imaging optical fiber, and the adjacent fields are ensured not to be overlapped. Preferably, the plurality of imaging subunits adopt imaging optical fibers of the same size and are arranged at equal intervals. The area of the filter is larger than the area of the cross section of the imaging fiber. In this embodiment, the surface of filter plates has a layer of oxide film, and the optical characteristic of filter plates corresponds each other with the optical characteristic of the filter plates in the imaging module on the unmanned aerial vehicle. The light source reflected by the diffuse reflection plate is incident from the incident end of the imaging optical fiber through the filter, is transmitted by the imaging optical fiber and is converged by the micro lens array to form a bundle of imaging optical fiber cluster, and is imaged on the photosensitive sensor to obtain a reflected image, wherein a group of light spots are displayed on the reflected image.

The area array imaging array includes a main imaging unit 32 and a plurality of single channel imaging units disposed around the main imaging unit. The main imaging module comprises a first area array photosensitive sensor, the first area array photosensitive sensor comprises an imaging objective lens, an anti-mixing filter, an infrared filter, a micro lens, a Bayer filter and a photodiode, and a light source reflected by the emission body passes through the imaging objective lens, the anti-mixing filter, the infrared filter, the micro lens, the Bayer filter and the photodiode. Each single-channel imaging unit comprises a second area array photosensitive sensor, the second area array photosensitive sensor comprises a filter, an imaging objective lens, a parallel light lens and a photodiode, and a light source reflected by the emission body passes through the filter, the imaging objective lens and the parallel light lens to the photodiode. And the outer side surfaces of the filters of the main imaging unit and the single-channel imaging unit are coated with a layer of oxidation film. The optical characteristics of the filter correspond to the optical characteristics of the filter in the imaging module on the drone.

The connecting device 5 is used for adjusting an included angle between the reflecting body and the incident body, when radiation correction is carried out, the included angle between the reflecting body and the incident body is preferably 30-45 degrees, and at the moment, the imaging module can receive a reflecting light source to the maximum extent.

When correcting, see fig. 4, be fixed in near unmanned aerial vehicle operation open ground with radiation correcting unit, and make the device face the sun, avoid the sheltering from of surrounding environment to the device. And when receiving an acquisition instruction, the controller controls the imaging module to acquire a reflection image, wherein the reflection image has time information and represents the acquisition moment of the image. The control signal of the controller adopts pulse trigger signals such as PPS (pulse per second), PWM (pulse width modulation) and the like, and the effective edge of the pulse signal is utilized to control the imaging module to complete data acquisition. The controller is also used for correcting the environmental image acquired by the unmanned aerial vehicle at the same moment according to the reflection image acquired by the imaging module.

Specifically, the controller includes: a receiving unit 61, a radiometric calibration unit 62, a calculation unit 63, a storage unit 64, and an image processing unit 65.

The receiving unit 61 is used for receiving the environment image acquired by the imaging module of the unmanned aerial vehicle, and the environment image has time information in a unified manner and represents the acquisition time of the image. The receiving unit is further configured to select an environmental image with the same wavelength band as the acquisition time of the reflected image from the acquired environmental images according to the uniform time reference and the timestamp of the acquisition time of the image, and send the environmental image to the calculating unit 63.

The storage unit 64 is used for storing the reflection image acquired by the imaging module of the radiation correction device.

Radiometric calibration unit 62 is used to radiometric scale the imaging modules of the radiometric calibration device to determine quantum efficiency models of the radiometric calibration device and the imaging modules employed by the drone, for example:

L＝a×DN+b；

wherein, L represents the radiance, DN represents the gray value, and a and b represent the coefficients of the quantum efficiency model. The calibration method can be a conventional method, and is not described herein.

The calculating unit 63 is configured to calculate the radiance of the reflected image according to the quantum efficiency model and the gray value of a reflected image acquired from the storage unit 64, and correct an environmental image according to the radiance, where the environmental image is an image acquired by an imaging module of the unmanned aerial vehicle at the same time as the reflected image. The formula for radiation correction is as follows:

wherein,representing the radiance of the reflected image;representing the radiance of the environment image; r_sThe reflectance (determined by the material of the diffuse reflection plate) of the diffuse reflection plate, R_GRepresenting the surface feature and surface feature reflectivity; and L' represents the radiance of the corrected environment image.

In this embodiment, before calculating the radiance, the calculating unit 63 further calls the image processing unit 65 to remove an abnormal value caused by the influence of the installation environment and an image inconsistent with the brightness change rule of the environmental image from the reflected image. The histogram can be used to describe the brightness change rule of the reflected image. The luminance histogram represents the occupancy of each luminance level in the image; image contrast is measured by a range of brightness levels. The histogram shows the number of pixels at a particular brightness level. For an 8-bit pixel, the luminance level ranges from 0 (black) to 255 (white). Because the radiation correction device shoots the image of the standard reflector plate, under the same ambient light, the image brightness shows a rule that the brightness of a central pixel is high and is smoothly reduced from the center to the edge, and if the image does not accord with the rule, the image is rejected. In the subsequent processing, mainly the central region of the image participates in the calculation. When the number of pixels occupied by the high-brightness level is lower than 70% in the total number of pixels in the selected area (the number can be set according to the actual requirement), the image is treated as an abnormal image and is to be rejected.

It should be noted that, if the area array imaging array is used to realize image acquisition, the image processing unit further needs to perform image segmentation on the reflected image, divide the image into specific areas with unique properties, and identify and extract an effective area according to the radiation correction requirement. Specifically, the method comprises the following steps: making a histogram of the reflected image, if the gray level histogram has an obvious double peak shape, selecting a gray value corresponding to a valley bottom between the two peaks as a threshold value, and then segmenting the image according to the threshold value; and extracting the effective region of the image by a grid vectorization method. And carrying out binarization on the image according to the specified invalid value to obtain a mask image, then generating a vector file as valid data of the reflection image through a grid vectorization function, and sending the vector file to a computing unit for radiation correction.

In this embodiment, the imaging device of the multispectral camera can synchronously acquire the reflected image of the corresponding waveband in the environment where the airborne narrow-bandwidth multispectral camera is located while performing operation exposure, so as to acquire the radiance value data of the reflected image, and correct the radiation characteristic of the environment image acquired by the multispectral camera according to the radiance value data, thereby realizing accurate radiation correction of the image data.

Example 2

This embodiment provides a radiation correction system that is applicable to the imaging module of the multispectral camera of airborne narrow bandwidth on the unmanned aerial vehicle, can realize accomplishing the radiation correction of unmanned aerial vehicle's imaging module under same light source. As shown in fig. 5, the radiation correction system includes a server (ground station) and the radiation correction device shown in embodiment 1, the server is in communication connection with the radiation correction device and a drone to be corrected, and the drone to be corrected includes an imaging module.

When the correction is carried out, the radiation correction device is installed, and the parameter setting is carried out, so that the performance parameters (size, pixel number, signal-to-noise ratio and the like) of the imaging module and the photosensitive elements of the imaging module are ensured to be consistent with the imaging parameters (photosensitive speed, exposure compensation, shutter, white balance and the like). When unmanned aerial vehicle is operated in the air route, the server judges the position of unmanned aerial vehicle in the air route according to the real-time log of data transmission, and when the distance between radiation correction device and the unmanned aerial vehicle was in presetting the within range, the server sent the collection instruction to radiation correction device's controller to when realizing that unmanned aerial vehicle was gathering the environment image, radiation correction device accomplished the collection of once reflection image to every wave band.

When the controller of the radiation correction device receives the acquisition instruction, the imaging module is controlled to acquire the reflected image, and the image is synchronously acquired with the imaging module of the unmanned aerial vehicle. When needs, the radiation correcting unit corrects the environment image that unmanned aerial vehicle acquireed at the same moment according to the reflection image. For the environment image that needs to be corrected, unmanned aerial vehicle can directly send the environment image to the radiation correction device, also can send the environment image to the radiation correction device through the server.

It should be noted that, when the radiation correction needs to be performed on a plurality of environmental images, the server may send a plurality of acquisition commands to the radiation correction device; and writing an acquisition interval in the acquisition instruction, so that the radiation correction device acquires the reflection image according to the acquisition interval.

In order to realize the unification of the system time reference, the controller can realize the time service of the imaging module. The imaging module can receive the trigger pulse and the clock signal at the same time, and when the photosensitive sensor images, the image is stored in the storage unit and the event file is updated in real time, so that the image has accurate time information.

One possible implementation of the set-up time base is provided below: the time service unit of the controller consists of an asynchronous serial communication interface chip, a GPS receiver, a GPS second pulse level conversion chip and a crystal oscillator. The asynchronous serial communication interface chip transmits a high-precision time scale; the GPS receiver receives a GPS signal and sends a GPS second pulse signal to the GPS second pulse level conversion chip; the GPS second pulse level conversion chip converts the GPS second pulse from a differential level to a TTL level; the crystal oscillator is used for generating stable clock signals.

Although specific embodiments of the present invention have been described above, it will be understood by those skilled in the art that this is by way of example only and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and the principles of the present invention, and these changes and modifications are all within the scope of the present invention.

Claims (8)

1. A radiation correction device, characterized in that it comprises: a controller, an imaging module;

the controller is electrically connected with the imaging module;

the controller is used for sending a collection instruction to the imaging module;

the imaging module is used for acquiring a reflection image and sending the reflection image to the controller when receiving the acquisition instruction.

2. The radiation correction apparatus of claim 1, further comprising:

a reflector body provided with a diffuse reflection plate;

the incident body and the reflecting body form an included angle;

the imaging module is arranged on the incident body and is positioned on one side close to the diffuse reflection plate;

the diffuse reflection plate is used for reflecting the light source to the imaging module.

3. The radiation correction apparatus of claim 2, further comprising a connection device;

two ends of the connecting device are respectively connected with the reflecting body and the incident body;

the connecting device is used for adjusting an included angle between the reflecting body and the incident body.

4. A radiation correction device according to claim 3, characterized in that the included angle has a value in the range of 30 ° to 45 °.

5. The radiation correction apparatus of claim 2, wherein the imaging module comprises a photosensor and a plurality of imaging subunits;

each imaging subunit includes: a filter, an imaging fiber and a microlens;

and the light source reflected by the diffuse reflection plate passes through the filter, the imaging optical fiber and the micro lens to reach the photosensitive sensor.

6. The radiation correction apparatus of claim 2, wherein the imaging module comprises a main imaging unit and a plurality of single channel imaging units;

the plurality of single-channel imaging units are dispersedly arranged around the main imaging unit;

the main imaging unit comprises an imaging objective lens, an anti-aliasing filter, an infrared filter, a micro lens, a Bayer filter and a photodiode, and a light source reflected by the diffuse reflection plate passes through the imaging objective lens, the anti-aliasing filter, the infrared filter, the micro lens and the Bayer filter to reach the photodiode;

the single-channel imaging unit comprises a filter, an imaging objective lens, a parallel light mirror and a photodiode, and a light source reflected by the diffuse reflection plate passes through the filter, the imaging objective lens and the parallel light mirror to the photodiode.

7. The radiation correction device of claim 2, wherein the reflector body has a slot, and the diffuse reflector plate slides into and is secured to the reflector body through the slot.

8. A radiation correction system, characterized in that the radiation correction system comprises: a server and a radiation correction device as claimed in any one of claims 1 to 7;

the server is in communication connection with the radiation correction device and the unmanned aerial vehicle to be corrected;

the server is used for sending the acquisition instruction to the radiation correction device when the distance between the radiation correction device and the unmanned aerial vehicle is within a preset range.