CN111896108A - Method and device for assembling and adjusting imaging spectrometer - Google Patents

Abstract

The invention discloses a method for assembling and adjusting an imaging spectrometer. First, a pre-drawn gradient line width stripe target is placed next to the measured target; a polychromatic light source is used to illuminate the gradient line width stripe target, so that the gradient line width is The streak target is imaged on the detector of the to-be-installed imaging spectrometer; the imaging spectrometer adopts a single-frame display mode, and by adjusting the distance between the front mirror of the imaging spectrometer and the slit, the polychromatic image of the streak plate is sharpened , and display the single-wavelength gray value of the polychromatic image of the gradient line-width striped target in real time; when the difference between the peak-to-peak value and the peak-to-valley value of the displayed single-wavelength image is the largest, the front mirror and slit of the imaging spectrometer are fixed. The distance between them realizes the adjustment of the imaging spectrometer. The method does not need to replace the components of the existing imaging spectrometer, and only needs to adjust the distance between the front mirror and the slit to realize the hyperspectral imaging detection of the measured target at a limited distance, and can avoid the subjectivity of human judgment by the naked eye, and improve the installation and adjustment. precision.

Description

Method and device for assembling and adjusting imaging spectrometer

technical field

The invention relates to the technical field of imaging spectrometers, in particular to a method and device for assembling and adjusting an imaging spectrometer.

Background technique

At present, imaging spectrometers can obtain two-dimensional geometric information and spectral information of detection targets, and are widely used in remote sensing and scientific research fields. The front objective of the imaging spectrometer often uses an infinity telescopic objective. The installation and detection of the imaging spectrometer is usually achieved by simulating the infinity target in the laboratory through a collimator. The image is then imaged on the detector; then the simulated infinity target is used for data analysis, and the relative position of the slit and the infinity telescopic objective and the relative position between the slit and the detector are adjusted, so that the imaging quality can meet the requirements.

Nowadays, many imaging spectrometers use short focal length lenses, finite-distance lenses, microscope objectives or by adjusting the distance between the infinity telescopic objective and the slit to achieve imaging of close-range objects, and obtain specific distance detection in the laboratory or outdoors. 2D geometric information and spectral information of the target. Therefore, in the installation and detection of imaging spectrometers in the prior art, collimator tubes are used in the laboratory to simulate infinity targets to assemble and adjust the imaging spectrometer, and this method is no longer suitable for short-range hyperspectral imaging.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method and device for assembling and adjusting an imaging spectrometer. The method does not need to replace the components of the existing imaging spectrometer, and only needs to adjust the distance between the front mirror and the slit to achieve high accuracy to the limited-distance measured target. Spectral imaging detection, and can avoid the subjectivity of human judgment, and improve the adjustment accuracy.

The purpose of this invention is to realize through the following technical solutions:

A method for assembling and adjusting an imaging spectrometer, the method comprising:

Step 1. Place the pre-drawn gradient line width stripe target next to the measured target;

Step 2, using a polychromatic light source to illuminate the gradient line width stripe target, so that the gradient line width stripe target is imaged on the detector of the to-be-installed imaging spectrometer;

Step 3. Make the imaging spectrometer use a single-frame display mode, and adjust the distance between the front mirror and the slit of the imaging spectrometer to make the polychromatic image of the streak plate sharp, and display the gradient line width streak target in real time. The single-wavelength gray value of the polychromatic image;

Step 4. When the difference between the peak-to-peak value and the peak-to-valley value of the displayed single-wavelength image is the largest, the distance between the front mirror of the imaging spectrometer and the slit is fixed to realize the adjustment of the imaging spectrometer.

It can be seen from the technical solution provided by the present invention that the above method does not need to replace the components of the existing imaging spectrometer, and only needs to adjust the distance between the front mirror and the slit to realize the hyperspectral imaging detection of the limited-distance measured target, and It can avoid the subjectivity of human judgment and improve the accuracy of installation and adjustment.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

1 is a schematic flowchart of a method for assembling and adjusting an imaging spectrometer provided by an embodiment of the present invention;

2 is a schematic diagram of the optical path of the imaging spectrometer assembly and adjustment process according to the embodiment of the present invention;

3 is a schematic diagram of a gradient line width striped target according to an embodiment of the present invention;

4 is a schematic diagram of a target when evaluating the imaging quality of an imaging spectrometer according to an embodiment of the present invention;

5 is a schematic structural diagram of a device for adjusting the imaging spectrometer provided by an embodiment of the present invention;

6 is a schematic diagram of the dynamic transfer function MTF of the push-broom image push-broom dimension of the imaging spectrometer wavelength 700nm of this example;

7 is a schematic diagram of the dynamic transfer function of the push-broom image space dimension of the imaging spectrometer wavelength 700nm of this example;

FIG. 8 is a schematic diagram of the point spread function of the push-broom image of the imaging spectrometer of this example with a wavelength of 700 nm.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. FIG. 1 is a schematic flowchart of a method for assembling and adjusting an imaging spectrometer provided by an embodiment of the present invention, and the method includes:

Step 1. Place the pre-drawn gradient line width stripe target next to the measured target;

In this step, FIG. 2 is a schematic diagram of the optical path of the imaging spectrometer installation and adjustment process according to the embodiment of the present invention. Referring to FIG. 2 , the pre-drawn gradient line width stripe target is obtained in the following way:

First, use a meter ruler to measure the distance between the measured target and the imaging spectrometer 4 to be installed, and calculate the line width of the gradient line width stripe target 2 according to the detection target object distance, the focal length of the front mirror 5 and the width of the slit 6, as shown in the figure 3 is a schematic diagram of the gradient line width striped target according to the embodiment of the present invention;

Then use the drawing software to draw the gradient line width stripe target 2, and print it out with a printer and fix it on a cardboard or realize it by etching, scribing and painting on an aluminum plate, which is convenient for long-term use.

In addition, when the gradient line width stripe target is placed, the gradient line width stripe target 2 is perpendicular to the optical axis of the imaging spectrometer 4 and aligned with the optical axis, and the stripe direction of the gradient line width stripe target 2 is the same as that of the optical axis. The slit 6 of the imaging spectrometer 4 is vertical.

Step 2, using a polychromatic light source to illuminate the gradient line width stripe target, so that the gradient line width stripe target is imaged on the detector of the to-be-installed imaging spectrometer;

In this step, as shown in Figure 2, in the laboratory, the polychromatic light source 1 needs to be turned on to illuminate the gradient line width stripe target 2. In the outdoor polychromatic light source 1, sunlight can be directly used, and the imaging spectrometer 4 acquisition software is opened, and a single Frame display, on the display screen of the computer 9, a polychromatic image 10 formed on the detector 8 by the target 2 with gradient line width stripes through the spectrometer 7 dispersion through the slit 6 will appear on the display screen of the computer 9, and the gray value of a certain line of the detector 8 will be displayed. That is, the single-wavelength gray value 11 of the polychromatic image 10 of the gradient line-width striped target 2 is displayed in real time on the computer display screen, and the wavelength channel is optional.

Step 3. Make the imaging spectrometer use a single-frame display mode, and adjust the distance between the front mirror and the slit of the imaging spectrometer to make the polychromatic image of the streak plate sharp, and display the gradient line width streak target in real time. The single-wavelength gray value of the polychromatic image;

In this step, specifically by adjusting the distance between the front mirror 5 of the imaging spectrometer 4 and the slit 6, the complex color image of the streak plate is sharp and the detector 8 single-wavelength gradient line width stripe target 2 complex color Image 10 has the highest contrast, and displays the single-wavelength gray value 11 of the polychromatic image 10 of the gradient line width striped target 2 in real time.

Step 4. When the difference between the peak-to-peak value and the peak-to-valley value of the displayed single-wavelength image is the largest, the distance between the front mirror of the imaging spectrometer and the slit is fixed to realize the adjustment of the imaging spectrometer.

In the installation and adjustment process of step 4, the imaging quality of the imaging spectrometer 4 can be further evaluated, and the specific process is as follows:

As shown in FIG. 2 , when the difference between the peak-to-peak value 12 and the peak-to-valley value 13 of the displayed single-wavelength image is the largest, fix the positions of the front mirror 5 and the slit 6 of the imaging spectrometer 4, and calculate the imaging The static transfer function MTF of spectrometer 4;

Further replace the pattern of the gradient line width striped target 2, as shown in FIG. 4 is a schematic diagram of the target when the imaging quality of the imaging spectrometer is evaluated according to the embodiment of the present invention, replace the target shown in FIG. 4, and then adjust the detector 8 exposure time, so that the frame frequency of the detector 8 matches the rotation speed of the one-dimensional turntable 3, adjust the software of the upper computer, make the imaging spectrometer 4 in the push-broom mode, and push the replaced gradient line width stripe target 2. scan imaging;

Then, perform data analysis on the hyperspectral image of the replaced target 2 with gradient line width stripes, and measure the dynamic transfer function MTF of the imaging spectrometer 4 from the longitudinal stripes 14, 21 and the longitudinal edge 20 of the gradient line width; The gradient transverse stripes 16, 19 and the transverse edge 17 measure the dynamic transfer function MTF of the spatial dimension; the point spread functions of each field of view and each band of the imaging spectrometer 4 are measured by the white dots 15 and 18 of different diameters, The evaluation of the imaging quality of the imaging spectrometer 4 is realized.

In addition, the gradient line width stripe target 2 can also be retracted, so that the imaging spectrometer 4 is in the push-broom mode, and the computer 9 controls the rotation speed of the one-dimensional turntable 3 and the frame frequency of the detector 8 at the same time, so as to achieve high accuracy of the measured target. Spectral Imaging.

Based on the above-mentioned adjustment method, an embodiment of the present invention further provides a device for adjusting the imaging spectrometer. FIG. 5 is a schematic structural diagram of the device for adjusting the imaging spectrometer provided by the embodiment of the present invention. The device includes a complex Color light sources, pre-drawn gradient linewidth stripe targets, imaging spectrometers, and terminal processing equipment, including:

The imaging spectrometer is fixed on a one-dimensional rotating stage, and the pre-drawn gradient line width stripe target is placed next to the measured target;

The gradient linewidth stripe target is illuminated by the polychromatic light source, so that the gradient linewidth stripe target is imaged on the detector of the imaging spectrometer;

The detector of the imaging spectrometer is connected to the terminal processing device;

The imaging spectrometer adopts a single-frame display mode. By adjusting the distance between the front mirror of the imaging spectrometer and the slit, the polychromatic image of the fringe plate is sharpened, and the gradient line is displayed on the terminal processing device in real time. The single-wavelength gray value of the polychromatic image of the wide stripe target;

Wherein, when the difference between the peak-to-peak value and the peak-to-valley value of the single-wavelength image displayed on the terminal processing device is the largest, the distance between the front mirror of the imaging spectrometer and the slit is fixed to realize the adjustment of the imaging spectrometer.

In the specific implementation process, the polychromatic light source adopts a halogen lamp with a continuous spectrum, or an LED lamp with a characteristic wavelength;

When used in the field, the polychromatic light source directly adopts the solar spectrum, which facilitates the installation and adjustment of the imaging spectrometer in the field.

The line width of the above-mentioned gradient line width stripe target is calculated according to the object distance of the measured target, the focal length of the front mirror of the imaging spectrometer and the width of the slit, and the line width is 1/2 times the quist frequency, 1 times, 2 times, 4 times. The specific acquisition method is as described in the foregoing method embodiment.

The implementation process of the above method and device will be described in detail below with a specific example. In this example, a visible and near-infrared imaging spectrometer needs to be installed and adjusted. 11um, obtain the hyperspectral imaging data of the Fengyun satellite model in the laboratory, and its technical indicators are as described in Table 1:

Table 1 System index requirements

System metrics Indicator requirements System F number 2.4 Spectral range 0.4～1.0μm Front lens focal length 100mm Spectrometer magnification -1 slit length 14mm slit width 30um dispersion width 11.264mm

According to the above indicators of the imaging spectrometer to be installed and adjusted, according to the installation and adjustment method provided by the present invention, the installation and adjustment steps are as follows:

1) Use a meter ruler to measure the length of the Fengyun satellite model to be 50cm, comprehensively consider the focal length of the front mirror, the slit length and the positional relationship of the laboratory, determine the distance between the measured target Fengyun satellite model and the imaging spectrometer is 5m, and according to the front The focal length of the mirror is 100mm and the slit width is 30um. The gradient line width of the calculated target is 0.75mm, 1.5mm, 3mm and 6mm.

2) Use computer graphics software to draw the target, print it out with a printer, and fix it on a cardboard.

3) Place the Fengyun satellite model on the laboratory optical platform, measure the distance of 4.5m with a meter ruler, fix the imaging spectrometer on a one-dimensional rotating table, and place the target next to the Fengyun satellite model. Make the target perpendicular to the optical axis of the imaging spectrometer and align with the optical axis, and the stripe direction of the target is perpendicular to the slit of the imaging spectrometer.

4) Turn on the halogen tungsten lamp of the polychromatic light source to illuminate the target, open the imaging spectrometer acquisition software, and use a single frame display, the polychromatic image formed on the detector by the target through the slit through the spectrometer dispersion will appear on the computer display screen, And the gray value of a certain row of the detector, that is, the single wavelength gray value of the target polychromatic image, is displayed on the computer display screen in real time, and the wavelength channel is optional.

5) Adjust the distance between the front mirror of the imaging spectrometer and the slit, so that the polychromatic image of the streak plate is sharp and the contrast of the single-wavelength target polychromatic image of the detector is the highest, and the single-wavelength gray value of the target polychromatic image is displayed in real time. , when the difference between the peak-to-peak value and the peak-to-valley value of the single-wavelength image is the largest, the position of the front mirror of the imaging spectrometer is fixed to realize the adjustment of the imaging spectrometer; at the same time, the static transfer function MTF of the imaging spectrometer is calculated. The MTF value at the frequency is 0.45.

6) Further replace the pattern of the target, adjust the exposure time of the imaging spectrometer detector, make the frame frequency of the detector match the rotation speed of the one-dimensional turntable, and adjust the software of the upper computer to make the imaging spectrometer in push-broom mode, so that the imaging spectrometer can be replaced. target for push-broom imaging.

7) Perform data analysis on the hyperspectral image of the replacement target. The dynamic transfer function MTF of the imaging spectrometer's push-sweep dimension can be measured from the longitudinal stripes with gradual line width and the longitudinal edge. As shown in Figure 6, the wavelength of the imaging spectrometer in this example is 700 nm Schematic diagram of the dynamic transfer function MTF of the push-broom image push-broom dimension.

The dynamic transfer function MTF of the spatial dimension can be measured from the transverse stripes with the line width gradient and the transverse edge. The MTF value at the Nyquist frequency is 0.4. As shown in Figure 7, the imaging spectrometer of this example is push-broom at a wavelength of 700 nm. Schematic diagram of the dynamic transfer function of the image space dimension, with an MTF value of 0.43 at the Nyquist frequency.

The point spread function of each field of view and each wavelength band of the imaging spectrometer can be measured from white dots of different diameters. Figure 8 shows the schematic diagram of the point spread function of the push-broom image of the imaging spectrometer wavelength of 700 nm in this example, so as to realize the imaging spectrometer. Evaluation of imaging quality.

8) Further, the target can be retracted so that the imaging spectrometer is in push-broom mode, and the computer controls the rotation speed of the one-dimensional turntable and the frame frequency of the detector at the same time, so as to realize the hyperspectral imaging of the Fengyun satellite model.

It should be noted that the content not described in detail in the embodiments of the present invention belongs to the prior art known to those skilled in the art. For example, the use of target patterns in other imaging systems, changing the method of making targets, etc.

To sum up, the method and device according to the embodiments of the present invention do not need to replace the components of the existing imaging spectrometer, and only need to adjust the distance between the front mirror and the slit to realize the hyperspectral imaging detection of the limited-distance measured target. The difference between the peak-to-peak value and the peak-to-valley value of the polychromatic image of the single-wavelength gradient line width stripe target is used to judge the clarity of the striped plate polychromatic image, which avoids the subjectivity of human judgment and makes the adjustment accuracy higher.

At the same time, by replacing the target image, it can also be used for the analysis and evaluation of the imaging quality of the imaging spectrometer. This adjustment method does not require much laboratory testing equipment, and the device has a simple structure, which is also conducive to the installation and adjustment of the imaging spectrometer in the field and imaging quality. The detection is fast, the precision is high, and the target making method is simple and the cost is low.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (8)

1. A method of tuning an imaging spectrometer, the method comprising:

step 1, placing a pre-drawn gradient line width stripe target beside a target to be detected;

step 2, illuminating the gradient line width stripe target by adopting a polychromatic light source, and imaging the gradient line width stripe target on a detector of an imaging spectrometer to be assembled and adjusted;

step 3, enabling the imaging spectrometer to adopt a single-frame display mode, enabling a complex color image of the fringe plate to be sharp by adjusting the distance between a front mirror and a slit of the imaging spectrometer, and displaying the single-wavelength gray value of the target complex color image of the fringe with the gradually-changed line width in real time;

and 4, when the difference value between the peak value and the peak valley value of the displayed single-wavelength image is maximum, fixing the distance between the front mirror of the imaging spectrometer and the slit, and realizing the adjustment of the imaging spectrometer.

2. The method for tuning an imaging spectrometer of claim 1, wherein in step 1, the pre-drawn gradient linewidth fringe target is obtained by:

measuring the distance between a target to be measured and the imaging spectrometer to be adjusted by using a meter ruler, and calculating the line width of the stripe target with the gradually changed line width according to the object distance of the target to be detected, the focal length of a front lens and the width of a slit;

and drawing the stripe target with the gradually changed line width by using drawing software, and printing the stripe target by using a printer and fixing the stripe target on a hardboard or etching, scribing and spraying paint on the aluminium plate, so that the stripe target is convenient to use for a long time.

3. The method for assembling an imaging spectrometer of claim 1, wherein in step 1, when the gradient linewidth stripe target is placed, the gradient linewidth stripe target is perpendicular to an optical axis of the imaging spectrometer and aligned with the optical axis, and a stripe direction of the gradient linewidth stripe target is perpendicular to a slit of the imaging spectrometer.

4. The method for adjusting an imaging spectrometer of claim 1, wherein in step 3, the distance between the front mirror and the slit of the imaging spectrometer is adjusted to make the complex color image of the fringe plate sharp and the contrast of the detector complex color image of the single-wavelength gradient line-width fringe target highest, and the gray scale value of the single wavelength of the complex color image of the gradient line-width fringe target is displayed in real time.

5. The assembly method of the imaging spectrometer of claim 1, wherein in the assembly process of the step 4, the imaging quality of the imaging spectrometer is further evaluated, and the specific process is as follows:

when the difference value between the peak value and the peak valley value of the displayed single-wavelength image is maximum, fixing the positions of a front mirror and a slit of the imaging spectrometer, and calculating the static transfer function MTF of the imaging spectrometer;

further replacing the pattern of the stripe target with the gradually changed line width, adjusting the exposure time of the detector to enable the frame frequency of the detector to be matched with the rotating speed of the one-dimensional turntable, adjusting the software of an upper computer to enable the imaging spectrometer to be in a push-broom mode, and performing push-broom imaging on the replaced stripe target with the gradually changed line width;

then, performing data analysis on a hyperspectral image of the replaced stripe target with the gradually changed line width, and measuring a dynamic transfer function MTF of the push-broom dimension of the imaging spectrometer by using the longitudinal stripe with the gradually changed line width and the longitudinal edge; measuring a dynamic transfer function MTF of a space dimension by a transverse stripe with a gradually changed line width and a transverse edge; and measuring the point spread function of each wave band of each field of view of the imaging spectrometer by using white dots with different diameters, thereby realizing the evaluation of the imaging quality of the imaging spectrometer.

6. The utility model provides an installation and debugging device of imaging spectrometer which characterized in that, the device includes polychrome light source, the gradual change linewidth stripe target of drawing in advance, imaging spectrometer and terminal processing equipment, wherein:

the imaging spectrometer is fixed on the one-dimensional rotating platform, and a pre-drawn stripe target with a gradually-changed line width is placed beside a target to be measured;

illuminating the gradient line width stripe target by the polychromatic light source to enable the gradient line width stripe target to be imaged on a detector of the imaging spectrometer;

the detector of the imaging spectrometer is connected with the terminal processing equipment;

the imaging spectrometer adopts a single-frame display mode, the distance between a front lens and a slit of the imaging spectrometer is adjusted, so that the complex color image of the fringe plate is sharp, and the single-wavelength gray value of the target complex color image of the gradient line width fringe is displayed on the terminal processing equipment in real time;

when the difference value between the peak value and the peak valley value of the single-wavelength image displayed on the terminal processing equipment is the maximum, the distance between the front mirror and the slit of the imaging spectrometer is fixed, and the adjustment of the imaging spectrometer is realized.

7. The assembly apparatus of the imaging spectrometer of claim 6,

the compound color light source adopts a halogen lamp with continuous spectrum or an LED lamp with characteristic wavelength;

when the light source is used in the field, the light source with the composite color directly adopts the solar spectrum.

8. The assembly apparatus of the imaging spectrometer of claim 6,

the line width of the stripe target with the gradually changed line width is obtained by calculation according to the object distance of a measured target, the focal length of a front lens of the imaging spectrometer and the width of a slit;

the line widths are 1/2 times, 1 time, 2 times and 4 times of Nyquist frequency respectively.

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