CN217358748U - Device for improving accuracy of spectral imager and spectral imaging system - Google Patents
Device for improving accuracy of spectral imager and spectral imaging system Download PDFInfo
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Abstract
The utility model discloses an improve device and spectral imaging system of spectral imaging appearance accuracy relates to the optics field. The device includes: the device comprises an external computer, a spectrum imager, a spectrum radiance meter, a reference light source and a target light source. The device is characterized in that an external computer is connected with a spectral imager and a spectral radiance meter and used for calibrating the response characteristic of the spectral imager according to the response value, gain and integration time of the spectral imager and the spectral radiance detected by the spectral radiance meter when a reference light source enters the spectral imager and transmitting the response characteristic of the spectral imager to the spectral imager, and a computing unit in the spectral imager is used for acquiring the spectral radiance of a target light source according to the response characteristic of the spectral imager when the target light source enters the spectral imager. The device can calculate the spectral radiance of the target light source, completes restoration of radiation information of the target light source, and improves accuracy of the spectral imager.
Description
Technical Field
The utility model relates to an optics field especially relates to a device and spectral imaging system that improves spectral imager accuracy.
Background
The spectral imaging technology can simultaneously acquire the spectral and spatial information of a target, and is widely applied to scenes such as agriculture, forestry, ecology, industry and the like. Along with the improvement of the demand and the technical progress, on the premise of ensuring the accuracy of information acquisition, the development trend of a spectral imaging instrument is miniaturization, light weight and low cost.
The existing spectral imager is a novel low-cost light small spectral imager, which adopts the combination of a single lens, a multi-band-pass narrow-band light filter and a color sensor, and realizes the synchronous acquisition of different spectral channel information by utilizing the characteristics that different sub-pixels of the color sensor have broadband response and the response bands are crossed. Taking a typical RGB sensor as an example, fig. 1 is a graph illustrating transmittance of a multi-band pass filter and quantum efficiency curve of the RGB sensor. As shown in fig. 1, the abscissa represents wavelength and the ordinate represents sensor quantum efficiency and filter transmittance, and this combination can realize the detection of spectral radiance information of 550nm, 720nm and 840nm channels. The spectral transmittance curve of the multi-band-pass narrow-band filter is changed according to the detection requirement, so that the target information of other spectral channels can be obtained, and the method has high use flexibility. However, with this type of spectral imager, the signal directly captured by the sensor is not the spectral radiation information of the target light, resulting in a decrease in the accuracy of the spectral imager.
Therefore, how to improve the accuracy of the spectral imager is an urgent problem to be solved by those skilled in the art.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing an improve device and spectral imaging system of spectral imaging appearance accuracy for improve spectral imaging appearance's accuracy.
In order to solve the technical problem, the utility model provides an improve device of spectral imaging appearance accuracy, the device includes: the system comprises an external computer 1, a spectral imager 2, a spectral radiance meter 3, a reference light source 4 and a target light source 5;
the reference light source 4 includes: a first reference light source and a second reference light source;
the reference light source 4 and the target light source 5 are respectively positioned in front of the lens of the spectral imager 2;
the light receiving hole of the spectral radiance meter 3 is parallel to the entrance pupil of the spectral imager 2 and is used for measuring the spectral radiance of each spectrum at the entrance pupil of the spectral imager 2 when the reference light source 4 is respectively incident on the spectral imager 2;
the external computer 1 is connected to the spectral imager 2 and the spectral radiance meter 3, and configured to set a gain and an integration time for the spectral imager 2, record a response value, a gain, and an integration time of the spectral imager 2, record the spectral radiance detected by the spectral radiance meter 3, calibrate a response characteristic of the spectral imager 2 according to the response value, the gain, the integration time, and the spectral radiance, and transmit the response characteristic of the spectral imager 2 to the spectral imager 2, when the first reference light source and the second reference light source respectively enter the spectral imager 2;
the calculating unit in the spectral imager 2 is configured to record a response value, a gain, and an integration time of the spectral imager 2 when the target light source 5 is incident on the spectral imager 2, and obtain spectral radiance of the target light source 5 according to a response characteristic of the spectral imager 2.
Preferably, the first reference light source is a stable monochromatic reference light source, and the second reference light source is a uniform polychromatic reference light source.
Preferably, the spectral range of the second reference light source covers all the response bands of the spectral imager 2.
Preferably, the first reference light source includes a halogen lamp 7, a stabilized voltage power supply 8, a monochromator 9, and a collimator 10.
Preferably, the second reference light source is a polychromatic reference light source generated by integrating sphere 12.
Preferably, the reference light source 4 and the target light source 5 are respectively located within a first preset distance in front of the lens of the spectral imager 2.
Preferably, the spectral radiance meter 3 and the spectral imager 2 are both located on the same plane perpendicular to the transmission direction of the light beam emitted by the light source.
In order to solve the technical problem, the utility model also provides a spectral imaging system, including the device of foretell improvement spectral imaging appearance accuracy.
The utility model provides an improve device of spectral imaging appearance accuracy, include: the device comprises an external computer, a spectrum imager, a spectrum radiance meter, a reference light source and a target light source. The device is characterized in that an external computer is connected with a spectral imager and a spectral radiance meter and used for calibrating the response characteristic of the spectral imager according to the response value, gain and integration time of the spectral imager and the spectral radiance detected by the spectral radiance meter and transmitting the response characteristic of the spectral imager to the spectral imager when a reference light source enters the spectral imager, and a computing unit in the spectral imager is used for obtaining the spectral radiance of a target light source according to the response characteristic of the spectral imager when the target light source enters the spectral imager. The device can calculate the spectral radiance of the target light source, completes restoration of radiation information of the target light source, and improves accuracy of the spectral imager.
Furthermore, the utility model provides a spectral imaging system includes the device of the improvement spectral imaging appearance accuracy that the aforesaid mentioned, and the effect is the same as above.
Drawings
In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious to those skilled in the art that other drawings can be obtained based on these drawings without inventive work.
FIG. 1 is a graph illustrating the transmittance of a multi-band-pass filter and the quantum efficiency curve of an RGB sensor;
fig. 2 is a structural diagram of an apparatus for improving accuracy of a spectral imager according to the present invention;
FIG. 3 is a block diagram of a three channel spectral imager;
FIG. 4 is a flow chart of obtaining spectral radiance of a target light source via the apparatus of the present application for improving spectral imager accuracy;
FIG. 5 is a flow chart of a three-band pass narrowband filter combined with a typical RGB sensor to achieve target spectral radiance information detection of three spectral channels;
FIG. 6 is a diagram illustrating spectral transmittance of a three-band pass narrowband filter and a quantum efficiency curve of an RGB sensor;
FIG. 7 is a graph showing the spectral transmittance of a four-band pass narrowband filter and the quantum efficiency curve of an RGB-IR sensor;
FIG. 8 is a diagram of the apparatus structure of a monochromatic light incident spectral imager;
fig. 9 is a device configuration diagram of a polychromatic light incidence spectral imager.
The reference numbers are as follows: the system comprises an external computer 1, a spectrum imager 2, a spectrum radiance meter 3, a reference light source 4, a target light source 5, a three-channel spectrum imager 6, a halogen lamp 7, a stabilized voltage power supply 8, a monochromator 9, a collimator 10, a high-precision turntable 11 and an integrating sphere 12.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, the ordinary skilled in the art can obtain all other embodiments without creative work, which all belong to the protection scope of the present invention.
The core of the utility model is to provide a device and spectral imaging system that improve spectral imaging appearance accuracy for improve spectral imaging appearance's accuracy.
In order to make the technical field better understand the solution of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings and the detailed description. Fig. 2 is a structural diagram of an apparatus for improving accuracy of a spectral imager provided by the present invention. As shown in fig. 2, the apparatus includes: the system comprises an external computer 1, a spectral imager 2, a spectral radiance meter 3, a reference light source 4 and a target light source 5;
the reference light source 4 includes: a first reference light source and a second reference light source;
the reference light source 4 and the target light source 5 are respectively positioned in front of the lens of the spectral imager 2;
the light receiving hole of the spectral radiance meter 3 is parallel to the entrance pupil of the spectral imager 2 and is used for measuring the spectral radiance of each spectrum at the entrance pupil of the spectral imager 2 when the reference light source 4 respectively enters the spectral imager 2;
the external computer 1 is connected with the spectral imager 2 and the spectral radiance meter 3, and is used for setting gain and integration time for the spectral imager 2 respectively, recording the response value, the gain and the integration time of the spectral imager 2 and the spectral radiance detected by the spectral radiance meter 3 when the first reference light source and the second reference light source respectively enter the spectral imager 2, calibrating the response characteristic of the spectral imager 2 through the response value, the gain, the integration time and the spectral radiance and transmitting the response characteristic of the spectral imager 2 to the spectral imager 2;
the calculating unit in the spectral imager 2 is configured to record the response value, the gain, and the integration time of the spectral imager 2 when the target light source 5 is incident on the spectral imager 2, and obtain the spectral radiance of the target light source 5 according to the response characteristic of the spectral imager 2.
The spectral imager 2 mainly includes: optical filter, optical lens and sensor. The optical filter is an optical device for selecting a desired radiation band, and as for the optical filter, the optical filter in the spectral imager 2 used in the present application is a multi-band pass narrowband optical filter. A multi-band pass narrowband filter refers to a filter that is highly transmissive in a plurality of discrete wavelength bands and allows optical signals in a particular wavelength band to pass through, while blocking optical signals for both sides outside this wavelength band. For example, a three-band-pass narrowband filter refers to a filter that is highly transmissive in three discrete wavelength bands and allows optical signals in a particular wavelength band to pass through, while blocking optical signals on both sides outside this wavelength band. The optical lens is a key device of the spectral imager 2, and directly affects the imaging quality of the spectral imager 2, so that an appropriate optical lens is selected. The selection of the optical lens can be selected according to the imaging size of the lens, the resolution of the lens, the focal length and the view angle of the lens, the aperture or the light transmission amount, and the like. For the sensor, an RGB sensor is used in the three-channel spectral imager, and an RGB-IR sensor is used in the four-channel spectral imager, wherein the RGB-IR sensor is used for increasing the detection of near infrared band information on the basis of the RGB sensor. A three-channel spectral imager is taken as an example for explanation, and fig. 3 is a structural diagram of the three-channel spectral imager. As can be seen from fig. 3, the three-channel spectral imager 6 mainly includes a three-band-pass narrowband filter, an optical lens, and an RGB sensor. It should be noted that the three positions may be that the three-band pass narrowband filter shown in fig. 3 is placed in front of the optical lens, or the three-band pass narrowband filter is placed between the optical lens and the RGB sensor. When the three-band-pass narrow-band filter is placed in front of the optical lens, the incident beam firstly enters the three-channel narrow-band filter and then enters the RGB sensor after passing through the optical lens; when the three-band-pass narrow-band filter is positioned between the optical lens and the RGB sensor, the incident light beam firstly enters the optical lens, then passes through the three-band-pass narrow-band filter and then enters the RGB sensor. In the implementation, the installation position of the three-band pass narrowband filter is not limited, and may be one installation position. The reference light source 4 and the target light source 5 are respectively positioned in front of the spectral imager 2, and when the light source 4 is incident on the spectral imager 2, an aperture in the spectral imager 2 for limiting the incidence of the light beam is called an entrance pupil of the spectral imager 2. Signals of red, blue and green bands can be detected simultaneously by the spectral imager 2. And determining the basic information such as the nominal central wavelength, the full width at half maximum and the like of the spectral channel of the spectral imager 2 through spectral radiation response rule analysis.
The spectral radiance meter 3 is used to measure the spectral radiance of the reference light source 4. In this application, the spectral radiance meter 3 that adopts is a standard radiance meter, compares in ordinary spectral radiance meter 3 more can the accurate spectral radiance who measures reference light source 4. The light receiving hole of the standard spectral radiance meter is parallel to the entrance pupil of the spectral imager 2, when the incident light beam of the reference light source 4 enters the entrance pupil of the spectral imager 2, the spectral radiance of the reference light source 4 at the entrance pupil of the spectral imager 2 is detected, and the spectral radiance is uploaded to the external computer 1. The reference light source 4 includes a first reference light source and a second reference light source. The first reference light source is a monochromatic light source, and in practice, a quasi-monochromatic light source is selected, that is, the monochromatic light is guaranteed to be one wavelength. The second reference light source adopts polychromatic light as a reference light source.
The external computer 1 is connected with the spectral imager 2 and the spectral radiance meter 3, when the first reference light source and the second reference light source respectively enter the spectral imager 2, the gain and the integration time are respectively set for the spectral imager 2, the response value, the gain and the integration time of the spectral imager 2 are recorded, the spectral radiance detected by the spectral radiance meter 3 is recorded, the response characteristic of the spectral imager 2 is calibrated through the response value, the gain, the integration time and the spectral radiance, and the response characteristic of the spectral imager 2 is transmitted to the spectral imager 2.
The spectral imager 2 includes a calculation unit that records a response value, a gain, and an integration time of the spectral imager 2 when the target light source 5 is incident on the spectral imager 2, and acquires spectral radiance of the target light source 5 according to a response characteristic of the spectral imager 2.
Fig. 4 is a flowchart of acquiring spectral radiance of a target light source by the apparatus for improving accuracy of a spectral imager of the present application. The specific process of acquiring the spectral radiance of the target light source by the device for improving the accuracy of the spectral imager is as follows:
s10: when the first reference light source and the second reference light source respectively enter the spectral imager, respectively setting gain and integration time for the spectral imager; recording the response value, the gain and the integration time of the spectral imager and recording the spectral radiance detected by the spectral radiance meter;
the spectral imager is controlled by an external computer to image the reference light source with a specific integration time and gain. The reference light source comprises a first reference light source and a second reference light source, the response DN value of the spectral imager when the first reference light source and the second reference light source are incident to the spectral imager and the corresponding parameters such as the sensor integration time and the gain are recorded respectively, and the spectral radiance of the first reference light source and the second reference light source at the entrance pupil of the spectral imager is synchronously detected through a standard spectral radiance meter.
S11: calibrating the response characteristic of the spectral imager through the response value, the gain, the integration time and the spectral radiance and transmitting the response characteristic of the spectral imager to the spectral imager, so that when the target light source enters the spectral imager, a computing unit in the spectral imager records the response value, the gain and the integration time of the spectral imager and obtains the spectral radiance of the target light source according to the response characteristic of the spectral imager.
It should be noted that before the first reference light source and the second reference light source respectively enter the spectral imager, the spectral response rules of key components of the spectral imager need to be analyzed, specifically including the analysis of the transmission rate, the sensor quantum efficiency, the system transmission rate and other rules. According to the spectral transmittance curve of the multi-band-pass narrow-band filter and the quantum efficiency curve of each wave band of the sensor, a spectral radiation response model of the spectral imager is constructed as shown in a formula (1):
in the formula (1), i and j are pixel numbers of the sensor, k is a sub-pixel number of each group of pixels, and the sub-pixels respectively correspond to different wave bands according toIn a typical configuration of the present sensor, the specific bands corresponding to the sub-pixels include, but are not limited to, a red band, a green band, a blue band, and a near-infrared band, bandi is a number of spectral channels of the spectral imager, N is a number of spectral channels,
characterizing the radiation response function for the response value of sub-pixel k in pixel (i, j), f bandi Is the entrance pupil radiance of spectral imager spectral channel bandi.
When the first reference light source is incident to the spectral imager, stable quasi-monochromatic light with different wavelengths is incident to the spectral imager, and scanning imaging is carried out on spectral dimensions to obtain normalized spectral response coefficients of different sub-pixels of the spectral imager at each wavelength
λ l The center wavelength of the first incident quasi-monochromatic light.
Further, calculating equivalent normalized spectral response coefficients of all channels of the spectral imager
The calculation formula is shown in formula (2):
in the above formula (2), λ min,bandi And λ max,bandi Respectively is the lower limit and the upper limit of the spectral response wavelength of the spectral channel bandi, and delta lambda is the scanning step length of the spectral dimension when the spectral response function is calibrated. And respectively calculating the equivalent normalized spectral response coefficient of each channel for each sub-pixel.
For convenience of description, it is assumed in this application that the value of the response DN of the detector is linear with the intensity L of the incident light signal. In order to calibrate the absolute radiation response coefficient of the spectral imager, wide-spectrum reference light which is uniform, stable and has known spectral radiance is incident to the spectral imager to serve as a second reference light source, the spectral range of the second reference light source needs to cover all response wave bands of the spectral imager, and the spectral radiance at the entrance pupil of the spectral imager is synchronously monitored by using a standard spectral radiance meter. Then equation (1) can be rewritten as equation (3):
in the above-mentioned formula (3),
is the absolute radiation response coefficient of a neutron pixel k of a sensor pixel (i, j) of the spectral imager at the equivalent wavelength of a spectral channel bandi,
is the radiation response offset of a sub-pixel k in a sensor pixel (i, j) of a spectral imager, which can be directly measured by blocking the entrance pupil of the spectral imager,
for the entrance pupil equivalent radiance of the sub-pixel k of the spectral imager in the spectral channel bandi, data measured by a standard spectral radiance meter is needed to be calculated, and the equivalent normalized spectral response coefficient obtained by calculating the formula (2) is needed in the calculation process
And obtaining the entrance pupil equivalent radiance of the corresponding spectral channel through weighting calculation.
Further, the inter-channel relative radiation response proportionality coefficient of each band sub-pixel is defined as shown in formula (4):
the formula (4) is substituted for the formula (3) to establish a multivariate linear equation set, and the absolute radiation response coefficient is obtained by solving the equation set
To this end, the response characteristics of the spectral imager are calibrated by the external computer. And then the response characteristic of the spectral imager is transmitted to the spectral imager by an external computer, and when the target light source enters the spectral imager, parameters such as a response DN value, an integration time and a gain of the sensor are recorded by a computing unit in the spectral imager. Absolute radiation response coefficient calculated from the above formula according to gain and integration time of target light source when it is incident
And selecting corresponding absolute radiation response coefficients. The method specifically comprises the following steps:
when any target light is incident on the entrance pupil of the spectral imager, the spectral radiation response matrix of the spectral imager pixel (i, j) is shown in formula (5):
in the above formula (5), Q is the number of sub-pixels in each group of pixels, L target,bandi Is the incident radiance, M, of the target light at spectral channel bandi i,j The spectral radiation response matrix of the spectral imager is expressed as formula (6):
according to the formula (5) and the formula (6), the calculation formula of the target light spectrum radiance is derived to be the formula (7):
INV in the above formula (7) represents the inversion operation on the matrix.
And substituting the obtained spectral response coefficient and absolute radiation response coefficient calibration result into the formula (7), so that the spectral radiance of the target light can be calculated, and the restoration of the spectral radiance information of the target light is completed. It should be emphasized that, for the device for improving the accuracy of the spectral imager of the present application, the matrix method is used to recover the spectral radiance information of the target light, and other methods for solving the multiple linear equations and the multiple nonlinear equations are also within the scope of the present application.
In order to make those skilled in the art better understand that the present application obtains the spectral radiance of the target light source by the above-mentioned device for improving the accuracy of the spectral imager, the present application is further described in detail below with reference to fig. 5, and the present embodiment uses a three-band pass narrow-band filter in combination with a typical RGB sensor to implement the target spectral radiance information detection of three spectral channels. Fig. 5 is a flow chart of a three-band-pass narrowband filter combined with a typical RGB sensor to achieve target spectral radiance information detection of three spectral channels. The process comprises the following steps:
s100: the three-channel spectral imager is used for analyzing the spectral radiation response rule.
The spectral transmittance of the narrowband filter of the three-channel spectral imager and the quantum efficiency curve of the sensor are mainly analyzed, and fig. 6 is a schematic diagram of the spectral transmittance of the narrowband filter of the three-band-pass and the quantum efficiency curve of the RGB sensor. As shown in fig. 6, the filter in this embodiment uses a three-band narrow-band filter, and the sensor uses a typical RGB sensor, and can detect signals of red, blue, and green bands simultaneously. And determining basic information such as nominal central wavelength, half-width and the like of the spectral channels band1, band2 and band3 of the spectral imager through spectral radiation response law analysis.
S200: and (3) constructing a spectral radiation response model of the spectral imager.
And constructing a radiation response model of sub-pixels of a red waveband, a green waveband and a blue waveband of the spectral imager according to the spectral transmittance of the three-band-pass narrow-band filter and the quantum efficiency curve of the sensor. Let k be 1, 2, and3 in the formula (1) in the above embodiment, which are numbers of sub-pixels in red, green, and blue bands, respectively, and for convenience of description, variables are denoted by "R", "G", and "B", respectively.
Wherein, S200 specifically includes:
s201: and constructing a red-band sub-pixel radiation response model.
The constructed red-band sub-pixel radiation response model is shown as a formula (8):
s202, constructing a green wave band sub-pixel radiation response model.
The constructed green band sub-pixel radiation response model is shown as a formula (9):
s203, constructing a blue wave band sub-pixel radiation response model.
The constructed green band sub-pixel radiation response model is shown as a formula (10):
s300: the spectral response function is calibrated channel by channel.
S300 specifically comprises the following steps:
s301: quasi-monochromatic light is incident, spectral dimension is scanned, and the wavelength of the quasi-monochromatic light and the corresponding DN value of the spectral imager are synchronously recorded.
In the implementation, a halogen lamp, a stable power supply, a monochromator and a collimator tube can be used for generating quasi-monochromatic light as a reference light source, and a high-precision turntable is used for controlling the reference light source to be incident to different view fields of the spectral imager to be calibrated, namely, different pixels are illuminated. Controlling a spectral imager to image reference light by specific integration time and gain through an external computer, and recording a response DN value of the spectral imager and corresponding parameters such as sensor integration time and gain; synchronously detecting and recording the spectral radiance of the reference light at the entrance pupil of the spectral imager through a standard spectral radiance meter; according to the basic information analysis results of the spectral channels band1, band2 and band3 in S100, the emergent wavelength of the monochromator is continuously changed by the step size delta lambda, and the response DN value of the spectral imager under the incident light with different wavelengths is obtained through spectral dimension scanning.
S302: and respectively calculating the normalized spectral response functions of the pixels corresponding to the red wave band, the green wave band and the blue wave band.
Calculating equivalent radiance of different sub-pixels at each channel by using reference light spectrum radiance at scanning wavelength recorded by standard spectrum radiance meter
Then, the following equations (11), (12) and (13) are used for normalization processing to eliminate the influence of the reference light source spectrum on the calibration of the spectral response function:
UNI in the above equations (11), (12) and (13) represents normalization operation, λ ref1,l The spectral response function is expressed to calibrate the central wavelength of the I < th > quasi-monochromatic light in the reference light.
S303: equivalent normalized spectral response coefficients for spectral channels band1, band2, and band3 were calculated, respectively.
Substituting the above equations (11) - (13) into equation (2) can calculate the equivalent normalized spectral response coefficients of the spectral channels band1, band2 and band3
S400: and calibrating the absolute radiation response coefficient pixel by pixel.
S400 specifically comprises the following steps:
s401: and (3) stabilizing light source incidence in a wide spectrum band, and synchronously recording parameters such as entrance pupil spectral radiance, a spectral imager response DN value, sensor integration time, gain and the like.
In implementation, an integrating sphere can be used to generate stable and uniform broadband polychromatic light as a reference light source, fill the full field of view of the spectral imager, and a standard spectral radiance meter is used to synchronously measure the spectral radiance at the entrance pupil. And controlling the spectral imager to image emergent light of the integrating sphere with different radiances at different gains and integration times by using an external computer, and respectively recording a response DN value of the spectral imager and corresponding parameters such as the gains and the integration times.
S402: and calculating the entrance pupil equivalent radiances of the sub-pixels of the spectral channels band1, band2 and band3 corresponding to the red wave band, the green wave band and the blue wave band respectively.
Using the equivalent normalized spectral response coefficient obtained in the above step
And calculating the equivalent center wavelength of each channel, and interpolating the spectral radiance measured by the standard spectral radiance meter in the step S401 to obtain the entrance pupil equivalent radiance of all the sub-pixels of the spectral channels band1, band2 and band 3.
S403: and respectively calculating the absolute radiation response coefficients of the sub-pixels of the spectral channels band1, band2 and band3 corresponding to the red wave band, the green wave band and the blue wave band.
Substituting the DN value measured in S401 and the entrance pupil equivalent radiance at all the pixels of each spectral channel calculated in S402 into the formulas (8) to (10) to construct a linear equation system about the reference light, wherein the parameters
And
the pixel response DN value can be directly measured through the entrance pupil of the shielding spectrum imager. Calculating the relative radiation response proportionality coefficient among different spectral channels corresponding to the red-band, green-band and blue-band sub-pixels according to the formula (4), and solving the equation set to obtain the absolute radiation response coefficient
And
it should be noted that the absolute radiation response coefficient is related to the gain and the integration time of the sensor, and the calibration result of the absolute radiation response coefficient should be stored and used synchronously with the corresponding gain and integration time of the sensor.
S500: a spectral radiation response equation is established for the target light.
S500 specifically includes:
s501: target light is incident to the spectral imager, and parameters such as sensor DN value response, integration time and gain are recorded.
When the target light is incident to the spectral imager, the pixel response value is recorded
And
and the gain and the integration time of the sensor, and the corresponding absolute radiation response coefficient obtained by S400 calibration is selected according to the gain and the integration time.
S502: and establishing a spectral radiation response equation of the spectral imager, wherein the spectral imager comprises sub-pixel radiation responses in a red wave band, a green wave band and a blue wave band.
According to the absolute radiation response coefficient determined in S501 and the obtained pixel response DN value, a radiation response equation for the target light is established as shown in equation (14):
in the above formula M i，j Is expressed by equation (15):
s600: and resolving spectral radiation information of the target light.
Substituting the results obtained in S400 and S500 into the formula (7), and calculating the spectral radiances of the target light at the spectral channels band1, band2 and band3 to finish the restoration of the spectral radiance information of the target light. The solution formula is shown in formula (16):
in the embodiment, for a given sensor, the band-pass range of the multi-band-pass filter can be selected at will, and as long as the radiation response equations of different sub-pixels do not have linear correlation, restoration of target spectral radiation information can be completed by constructing a spectral radiation response model, calibrating spectral radiation response characteristics and resolving target spectral radiance. Therefore, different spectral channels can be selected according to different requirements.
In order to enable those skilled in the art to better understand that the device for improving the accuracy of the spectral imager acquires the spectral radiance of the target light source, in this embodiment, a four-band-pass narrowband filter and a typical RGB-IR sensor are used to achieve target spectral radiance information detection of four spectral channels, each group of pixels is added with a near-infrared band sub-pixel on the basis of a red band sub-pixel, a green band sub-pixel and a blue band sub-pixel, and fig. 7 is a schematic diagram of a spectral transmittance of the four-band-pass narrowband filter and a quantum efficiency curve of the RGB-IR sensor. The structure of the four-channel spectral imager is the same as that of the three-channel spectral imager shown in fig. 3, except that the three-band pass narrow-band filter is replaced by a four-band pass narrow-band filter, the RGB sensor is replaced by an RGB-IR sensor, and the rest are kept the same.
The target spectral radiation information of the four spectral channels is acquired by the device for improving the accuracy of the spectral imager, the only difference is that the target radiation information of the spectral channel band4 is added for resolving, the corresponding sensor is added with the detection of the near infrared band, the sub-pixels of the near infrared band are marked by the 'IR', and the specific scheme and the flow are not repeated herein.
The device for improving the accuracy of the spectral imager provided by the embodiment comprises: the device comprises an external computer, a spectrum imager, a spectrum radiance meter, a reference light source and a target light source. The device is characterized in that an external computer is connected with a spectral imager and a spectral radiance meter and used for calibrating the response characteristic of the spectral imager according to the response value, gain and integration time of the spectral imager and the spectral radiance detected by the spectral radiance meter and transmitting the response characteristic of the spectral imager to the spectral imager when a reference light source enters the spectral imager, and a computing unit in the spectral imager is used for obtaining the spectral radiance of a target light source according to the response characteristic of the spectral imager when the target light source enters the spectral imager. The device can calculate the spectral radiance of the target light source, completes restoration of radiation information of the target light source, and improves accuracy of the spectral imager.
Since the light intensity, spectrum, etc. of the incident light may drift over time, a large error may occur in the calculation of the radiation information of the target light source. Thus, in practice, the first reference light source is selected to be a stable monochromatic reference light source and the second reference light source is a uniform polychromatic reference light source.
For the first reference light source, a stable monochromatic reference light source is selected, thereby ensuring that the light intensity, spectrum, etc. of the light source does not drift over time. For the second reference light source, a uniform and stable complex color reference light source is selected, the stability refers to that the light intensity, the spectrum and the like of the light source cannot deviate along with the change of time, and the uniformity refers to that the light imager 2 receives the light on the same plane, and the light intensity distribution on the plane is uniform.
The first reference light source is selected as the stable monochromatic reference light source, and the second reference light source is the uniform polychromatic reference light source, so that the change of light intensity, spectrum and the like caused by the change of the light source along with time can be prevented, and the accuracy of the finally obtained spectrum radiance of the target light source is improved.
The second reference light source selected in the above embodiment is a uniform and stable light source, and in order to obtain the spectral radiance of the target light source 5, the spectral range as the second reference light source covers all the response bands of the spectral imager 2 in implementation.
The spectral range of the second reference light source provided by this embodiment covers all response bands of the spectral imager, and when target light of any spectral band enters the spectral imager, it can be ensured that spectral radiation information of the target light source is calculated.
In the above embodiments, the first reference light source is a stable monochromatic reference light source, that is, the light intensity, spectrum, etc. of the first reference light source do not shift with time, and in order to generate stable monochromatic light, the first reference light source includes a halogen lamp, a power supply, a monochromator, and a collimator as a preferred embodiment.
Fig. 8 is a device configuration diagram of a monochromatic light incident spectral imager. As shown in fig. 8, the power supply used in the apparatus is a regulated power supply 8, and the regulated power supply 8 is connected to the halogen lamp 7 to supply a regulated voltage to the halogen lamp 7. The light beam generated by the halogen lamp 7 passes through a monochromator 9, the monochromator 9 is a light splitting instrument, the polychromatic light is decomposed into quasi-monochromatic light through a dispersion element, and a series of independent monochromatic light with a narrow enough spectral interval is output. The monochromator 9 uses dispersive elements that are classified into prism monochromators and grating monochromators, and has a wide spectrum range from ultraviolet, visible, near-infrared to far-infrared. The monochromator 9 is positioned on the high-precision rotary table 11, and the high-precision rotary table 11 is used for controlling the reference light source to be incident to different view fields of the spectral imager 2, namely, different pixels are illuminated. The light beam passes through the monochromator 9 and then passes through the collimator 10 to generate a parallel light beam which enters the spectral imager 2.
In the device, monochromatic light generated by a stabilized voltage power supply 8, a halogen lamp 7, a monochromator 9 and a collimator 10 is used as a reference light source, wherein the stabilized voltage power supply 8 is connected with the halogen lamp 7, and light beams emitted by the halogen lamp 7 enter the collimator 10 to generate the monochromatic light as the reference light source after passing through the monochromator 9 on a high-precision turntable 11. The monochromatic light enters the spectral imager 2, the spectral radiance of the spectral imager 2 is measured by a standard spectral radiance meter, the external computer 1 is connected with the spectral imager 2, the spectral imager 2 is further controlled to image the monochromatic light by specific integration time and gain, and the response DN value of the spectral imager 2 and corresponding parameters such as sensor integration time and gain are recorded. In the present embodiment, the halogen lamp 7, the stable power supply 8, the monochromator 9, and the collimator 10 are used to generate quasi-monochromatic light as the reference light source, and other devices such as a tunable laser that generate stable, collimated, and quasi-monochromatic light may also be used as the reference light source.
The first reference light source provided by the embodiment comprises a halogen lamp, a power supply, a monochromator and a collimator tube, generates stable quasi-monochromatic light as the reference light source, and can ensure that the light intensity, the spectrum and the like of the light source cannot deviate along with time, so that the finally obtained spectral radiation information of the target light is relatively accurate.
The second reference light source in the above embodiments is a uniform, stable light source. In order to generate a uniform light source, as a preferred embodiment, the second reference light source is a polychromatic reference light source generated by an integrating sphere.
The integrating sphere is a hollow sphere with the inner wall coated with white diffuse reflection material, and is also called photometric sphere, light flux sphere and the like. One or more apertures are formed in the wall of the ball to serve as light entry apertures and light receiving apertures for the placement of light receiving devices. The inner wall of the integrating sphere should be a good sphere, and it is generally required that it should deviate from the ideal sphere by no more than 0.2% of the inner diameter. The inner wall of the ball is coated with a desired diffuse reflective material, i.e., a material having a diffuse reflection coefficient close to 1. The common material is magnesium oxide or barium sulfate, which is mixed with colloid adhesive and sprayed onto the inner wall. The spectral reflectance of the magnesium oxide coating in the visible spectrum range is over 99 percent, so that light entering the integrating sphere is reflected for multiple times by the inner wall coating to form uniform illumination on the inner wall. Fig. 9 is a device configuration diagram of a polychromatic light incidence spectral imager. As shown in fig. 9, an integrating sphere 12 is used to generate stable and uniform broadband polychromatic light as a reference light source 4, which fills the full field of view of the spectral imager 2, a standard spectral radiance meter measures the spectral radiance at the entrance pupil of the spectral imager 2, an external computer 1 is connected to the spectral imager 2, and then the spectral imager 2 is controlled to image the monochromatic light with specific integration time and gain, and the response DN value of the spectral imager 2 and corresponding parameters such as sensor integration time and gain are recorded. It should be noted that, in the present embodiment, the integrating sphere 12 is used as the reference light source, and other stable and uniform wide-band light sources meeting the requirement may also be used as the reference light source.
In the embodiment, the multi-color reference light source generated by the integrating sphere is used as the second reference light source, and light entering the integrating sphere is reflected for multiple times in the integrating sphere to form light with uniform illumination. The light beam with uniform illumination enters the spectral imager as a reference light source, and the finally obtained spectral radiation information of the target light is more accurate.
In order to ensure that light incident from the light source 4 can enter the spectral imager 2 and to reduce interference of the light beam during entry into the spectral imager 2. In a preferred embodiment, the reference light source 4 and the target light source 5 are respectively located within a first preset distance in front of the lens of the spectral imager 2.
In implementation, the light source is located in front of the lens of the spectral imager 2 to ensure that the light beam emitted by the light source can enter the spectral imager 2, i.e. the reference light source 4 and the target light source 5 are located in front of the lens of the spectral imager 2, but when the light source is located at a longer distance in front of the spectral imager 2, the light source is located within a preset distance in front of the spectral imager 2 because the light intensity is reduced due to the atmospheric molecules and the suspended particles absorbing or scattering the light beam in the atmosphere. In an implementation, the reference light source 4 and the target light source 5 are respectively located in front of the lens of the spectral imager 2 by a first preset distance, the reference light source 4 includes a first reference light source and a second reference light source, when the first reference light source enters the spectral imager 2, the first reference light source is located in front of the lens of the spectral imager 2 by the first preset distance, and as in the above embodiment, the halogen lamp 7, the stabilized voltage power supply 8, the monochromator 9 and the collimator 10 generate monochromatic light as the first reference light source, that is, the halogen lamp 7, the stabilized voltage power supply 8, the monochromator 9 and the collimator 10 are located in front of the lens of the spectral imager 2 by the first preset distance; the polychromatic light generated by the integrating sphere 12 is used as a second reference light source, that is, the integrating sphere 12 is located in a preset distance in front of the lens of the spectral imager 2; similarly, when the target light source 5 is incident on the spectral imager 2, the target light source 5 is also located within a preset distance in front of the spectral imager 2. The selection of the preset distance is not limited as long as the influence on the transmission of the light beam to the spectral imager 2 is reduced as much as possible.
The reference light source and the target light source provided by the embodiment are respectively located in the first preset distance in front of the lens of the spectral imager, so that the influence on the light beam transmitted to the spectral imager can be reduced, the reference light source is a stable light source as far as possible, and the finally obtained spectral radiation information of the target light is accurate.
In the above-described embodiment, the light receiving hole of the spectral radiance meter 3 is parallel to the entrance pupil of the spectral imager 2 for measuring the respective spectral radiances at the entrance pupil of the spectral imager 2 when the reference light sources 4 are respectively incident on the spectral imager 2. It is preferable for the spectral radiance meter 3 and the spectral imager 2 to be located such that the spectral radiance meter 3 and the spectral imager 2 are both located on the same plane perpendicular to the transmission direction of the light beam emitted from the light source.
When the incident light beam of the reference light source 4 enters the entrance pupil of the spectral imager 2, the spectral radiance meter 3 detects the spectral radiance of the reference light source 4 at the entrance pupil of the spectral imager 2. Firstly, the spectral radiance meter 3 and the spectral imager 2 are positioned on the same plane, so that the spectral radiance meter 3 can measure the spectral radiance at the entrance pupil of the spectral imager 2; secondly, when the spectral radiance meter 3 and the spectral imager 2 are both perpendicular to the light beam transmission direction, most of the light beams or even all the light beams emitted by the reference light source 4 can enter the spectral radiance meter 3 and the spectral imager 2.
The spectral radiance meter and the spectral imager that this embodiment provided all are located the coplanar perpendicular with the light beam transmission direction that the light source sent for during the light beam that reference light source produced gets into spectral radiance meter and spectral imager, make spectral radiance meter can carry out more accurate measurement to the spectral radiance of spectral imager entrance pupil department simultaneously, thereby make the spectral radiance information of the target light that reachs comparatively accurate.
Finally, the embodiment of the application also provides a spectral imaging system, which comprises a computer, a spectral imager, a spectral radiance meter, a reference light source and a target light source; the system comprises an external computer, a spectral imager and a spectral radiance meter, wherein the external computer is connected with the spectral imager and the spectral radiance meter and is used for calibrating the response characteristic of the spectral imager according to the response value, the gain and the integration time of the spectral imager and the spectral radiance detected by the spectral radiance meter and transmitting the response characteristic of the spectral imager to the spectral imager when a reference light source enters the spectral imager, and a computing unit in the spectral imager is used for obtaining the spectral radiance of a target light source according to the response characteristic of the spectral imager when the target light source enters the spectral imager. In addition, the first reference light source can be generated by a halogen lamp, a stabilized voltage power supply, a monochromator and a collimator, and the second reference light source can be generated by an integrating sphere. Since the above detailed description is made for each component, the detailed description is omitted here.
The spectral imaging system provided by the embodiment has the same beneficial effects as the device for improving the accuracy of the spectral imager mentioned above.
It is right above the utility model provides an improve device and spectral imaging system of spectral imager accuracy introduces in detail. The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, the present invention can be further modified and modified, and such modifications and modifications also fall within the protection scope of the appended claims.
It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Claims (8)
1. An apparatus for improving accuracy of a spectral imager, comprising: the system comprises an external computer (1), a spectral imager (2), a spectral radiance meter (3), a reference light source (4) and a target light source (5);
the reference light source (4) comprises: a first reference light source and a second reference light source;
the reference light source (4) and the target light source (5) are respectively positioned in front of a lens of the spectral imager (2);
the light receiving hole of the spectral radiance meter (3) is parallel to the entrance pupil of the spectral imager (2) and is used for measuring the spectral radiance of each spectrum at the entrance pupil of the spectral imager (2) when the reference light source (4) is respectively incident on the spectral imager (2);
the external computer (1) is connected with the spectral imager (2) and the spectral radiance meter (3) and is used for acquiring the response characteristic of the spectral imager (2) according to the response value, the gain and the integration time of the spectral imager (2) and the spectral radiance detected by the spectral radiance meter (3) when the reference light source (4) is incident to the spectral imager (2);
the spectral imager (2) comprises a computing unit; the calculating unit is used for acquiring the spectral radiance of the target light source (5) according to the response value, the gain, the integration time and the response characteristic of the spectral imager (2) when the target light source (5) is incident to the spectral imager (2).
2. The apparatus of claim 1, wherein the first reference light source is a stable monochromatic reference light source and the second reference light source is a uniform polychromatic reference light source.
3. The apparatus of claim 1, wherein the spectral range of the second reference light source covers all response bands of the spectral imager (2).
4. The apparatus of claim 2, wherein the first reference light source comprises a halogen lamp (7), a regulated power supply (8), a monochromator (9), and a collimator (10).
5. The apparatus of claim 2, wherein the second reference light source is a polychromatic reference light source generated by an integrating sphere (12).
6. The apparatus for improving the accuracy of a spectral imager according to claim 1, characterized in that the reference light source (4) and the target light source (5) are respectively located within a first preset distance in front of the lens of the spectral imager (2).
7. The apparatus of claim 1, wherein the spectral radiance meter (3) and the spectral imager (2) are both located on the same plane perpendicular to the direction of transmission of the light beam from the light source.
8. A spectral imaging system comprising the apparatus for improving the accuracy of a spectral imager of any one of claims 1 to 7.
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