CN113295387B - A multi-band strip filter optical parameter testing system and its testing method - Google Patents

Abstract

The invention discloses a multi-band strip filter optical parameter testing system and a testing method. The testing system includes a continuously tunable uniform monochromatic illumination light source component, a two-dimensional adjustment frame, an optical imaging system, a detector, and an image acquisition system. The processing system, power supply; 2D kinematic mount and camera components are installed inside the camera obscura. By adjusting the continuously tunable uniform monochromatic illumination light source assembly, the present invention can output a uniform narrow-band surface light source that matches the test channel spectrum. By irradiating a multi-band strip filter, all channels of the target to be measured are imaged by the optical imaging system and the detector. And output; use pre-processing operations such as background deduction and non-uniformity correction to eliminate test errors caused by the low-frequency disturbance of the test system itself; finally calculate the two-dimensional distribution image of the transmittance of the multi-band strip filter to complete the in-channel Calibration and correction of parameters such as uniformity, inter-channel spectral crosstalk, and transmittance can significantly improve test efficiency and test accuracy.

Description

A multi-band strip filter optical parameter testing system and its testing method

Technical field

The invention belongs to the field of optical metrology and measurement, and specifically relates to a multi-band strip filter optical parameter testing system and a testing method thereof.

Background technique

Multispectral imaging remote sensing technology has obvious advantages in the fields of earth observation, atmospheric detection, target recognition and other fields. Currently, there are two main methods to achieve multispectral narrow-band imaging, single-channel time-sharing measurement method and multi-channel simultaneous measurement method. The former obtains spectral images of different wavelengths in time by rotating a filter wheel or an adjustable filter. The disadvantage is that time-sharing imaging easily causes misalignment between the front and rear images; the latter uses multiple lenses or multiple image sensors to obtain spectral images of different wavelengths. It is possible to obtain multispectral images of the same target at the same time. The disadvantage is that the instrument is large and has a complex structure.

The multi-band strip filter is cut into narrow strips, integrated on the same substrate through splicing, and then combined with the detector. This method can simplify the system structure, replace the traditional imaging method, and has a small footprint. It has the advantages of small size, light weight, and no need for complicated spatial calibration. However, this "sandwich" structure will cause the incident light to reflect back and forth between channels, easily causing spectral aliasing between different channels. In addition, inconsistent thickness of the glue layer will also lead to uneven transmittance of the same channel, ultimately leading to erroneous results. Judgment. Therefore, it is necessary to adopt appropriate testing systems and testing methods to calibrate and quantitatively evaluate the processed multi-band strip filters.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a band strip filter optical parameter testing system and its testing method, through which the transmittance of the band strip filter can be corrected and calculated. Promote the development of multispectral imaging technology.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

A multi-band strip filter optical parameter testing system, including a continuously tunable uniform monochromatic illumination light source component, a two-dimensional adjustment stand, a camera component, an image acquisition and processing system, and a power supply; the two-dimensional adjustment stand is used to adjust multiple The position of the band strip filter is such that it is located on the object surface of the camera assembly; the camera assembly includes an optical imaging system and a detector for clearly imaging the multi-band strip filter; the image acquisition and processing system It is used to perform numerical analysis on the image output by the camera component; the power supply is used to power the entire test system; the two-dimensional adjustment frame and the camera component are both installed in the camera obscura. The two-dimensional adjustment frame involved in the above solution can adjust the position in the X-axis and Y-axis directions to realize the position adjustment of the multi-band strip filter in the X-axis and Y-axis directions. It is the most existing one in this field. Proven equipment.

Further, the continuous tunable uniform monochromatic illumination light source assembly includes an ellipsoid mirror, a grating monochromator and an integrating sphere. The outlet and entrance directions of the integrating sphere are 90°; the ellipsoid mirror is installed at the primary focus position. Xenon lamp, the slit entrance of the grating monochromator is set at the secondary focus of the ellipsoid mirror, the outlet of the grating monochromator is connected with the entrance of the integrating sphere, and the entrance of the grating monochromator is provided with an elimination secondary spectrum Filter; a circulating water-cooling cooling device is provided between the ellipsoid mirror and the secondary spectrum elimination filter; the circulating water-cooling cooling device includes a water-cooling filter and a circulating water path formed by a water pipe and the water-cooling filter. Composed of water pump. The multi-band strip filter includes a substrate and five narrowband spectral channel filters fixed on the substrate. The five narrowband spectral channel filters sequentially form channel one, channel two, channel three, channel four and Channel five.

Another object of the present invention is to provide a multi-band strip filter optical parameter testing method, which is based on the above-mentioned optical parameter testing system and includes the following steps:

a) Adjust the continuous tunable uniform monochromatic illumination light source component so that its output channel is one spectrum, and adjust the two-dimensional adjustment frame so that the multi-band strip filter is positioned on the object surface of the optical imaging system and the image is clearly imaged;

b) Set the detector exposure time t1, continuously capture n images in a bright field environment, and average to obtain the image μ _{y·filter·light} (i,j), where i and j represent the rows and columns of the output image respectively;

c) Set the detector exposure time to t1, continuously capture n images in a dark field environment, and average them to obtain the image μ _y·dark·t1 (i,j);

d) Move the multi-band strip filter out of the optical path, and the continuously tunable and uniform monochromatic illumination source directly illuminates the optical imaging system and detector;

e) Set the detector exposure time to t1, take n images continuously in a bright field environment, and average them to obtain the image μ _y·light (i, j);

f) Set the detector exposure time to t2. In a bright field environment, the detector output DN is 5% saturation value. Take n images continuously and average them to obtain the image μ _y·light·t2 (i,j);

g) Set the detector exposure time to t2, take n images continuously in a dark field environment, and average them to obtain the image μ _y·dark·t2 (i,j);

h) Set the detector exposure time to t3. The bright field environment makes the detector output DN a 95% saturation value. Take n images continuously and average them to obtain the image μ _y·light·t3 (i,j);

i) Set the detector exposure time to t3, continuously capture n images in a dark field environment, and average them to obtain the image μ _y·dark·t3 (i,j);

j) Adjust the continuous tunable uniform monochromatic illumination light source assembly to output channel two to channel five spectra respectively, and repeat steps a-i;

k) When the test is completed, turn off the power.

The above-mentioned multi-band strip filter optical parameter testing method also includes the following data processing steps:

a) Background deduction: Subtract the dark field image from the average bright field image to obtain the effective signal, refer to formulas (1)-(4):

U _y·filter (i,j)＝μ _{y·filter·light} (i,j)-μ _y·dark·t1 (i,j) (1)

U _y (i,j)＝μ _y·light (i,j)-μ _y·dark·t1 (i,j) (2)

U _y·Low (i,j)＝μ _y·light·t2 (i,j)-μ _y·dark·t2 (i,j) (3)

U _y·High (i,j)＝μ _y·light·t3 (i,j)-μ _y·dark·t3 (i,j) (4)

b) Non-uniformity correction: To correct the test error caused by the non-uniformity of the optical imaging system and the detector itself, refer to formulas (5)-(8); where, and/> are the mean values of U _y·High (i,j) and U _y·Low (i,j) respectively, G and O are the non-uniformity correction coefficients;

Y _{correction·filter} (i,j)＝G(i,j)×U _y·filter (i,j)+O(i,j) (7)

Y _correction (i,j)＝G(i,j)×U _y (i,j)+O(i,j) (8)

c) Two-dimensional distribution of transmittance: divide the corrected images with and without multi-band filters to obtain the two-dimensional distribution of transmittance T of different spectra. Refer to the following formula (9):

The beneficial effects of the present invention are as follows:

The invention proposes a multi-band strip filter optical parameter testing system that can output a uniform narrow-band surface light source that matches the spectrum of the test channel by adjusting the continuously tunable uniform monochromatic illumination light source assembly. By irradiating the multi-band strip filter The light sheet is imaged and output by the optical imaging system and detector for all channels of the target to be measured; preprocessing operations such as background deduction and non-uniformity correction are used to eliminate test errors caused by the low-frequency disturbance of the test system itself; the multi-band is finally calculated The two-dimensional distribution image of strip filter transmittance completes the calibration and correction of parameters such as intra-channel uniformity, inter-channel spectral crosstalk, and transmittance, significantly improving test efficiency and test accuracy.

Description of the drawings

Figure 1 is a schematic diagram of the multi-band strip filter described in the present invention;

Figure 2 is a schematic diagram of the multi-band strip filter optical parameter testing system described in the present invention;

Figure 3 is a flow chart of the multi-band strip filter optical parameter testing method described in the present invention;

Figure 4 shows the processed transmittance distribution image;

Figure 5 shows the transmittance curve distribution;

Detailed ways

The present invention will be further described below in conjunction with the embodiments and drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

Referring to Figure 1, the multi-band strip filter described in the present invention includes five narrowband spectral channels. The first three channel filter sizes are 18mm×3mm, and the last two channel filter sizes are 18mm×1mm. The blacked out splicing is integrated on the same base plate.

Referring to Figure 2, the multi-band strip filter optical parameter testing system described in the present invention includes a xenon lamp 1, an ellipsoid mirror 2, a circulating water cooling device 3, an elimination secondary spectrum filter 4, and a grating monochromator 5 , power supply 6, integrating sphere 7, multi-band strip filter 8, two-dimensional adjustment frame 9, optical imaging system 10, detector 11, darkroom 12, image acquisition and processing system 13. The xenon lamp 1 is placed at the primary focus of the ellipsoid mirror 2, the slit entrance of the grating monochromator 5 is set at the secondary focus of the ellipsoid mirror, and a circulating water cooling device 3 is set between the grating monochromator 5 and the xenon lamp 1. A secondary spectrum elimination filter 4 is placed in front of the entrance of the grating monochromator 5 to eliminate the secondary spectrum produced by grating dispersion. The exit of the grating monochromator 5 is connected to the entrance of the integrating sphere 7. The exit of the integrating sphere is 90 degrees from the entrance of the integrating sphere. °. The uniform monochromatic illumination light source emitted from the integrating sphere illuminates the multi-band strip filter 8. After transmission, the light passes through the optical imaging system 10, the detector 11, and the image acquisition and processing system 13 in sequence, and is finally converted into an image output. Among them, the two-dimensional adjustment frame 9 is used to adjust the position of the multi-band strip filter 8, the darkroom 12 is used to provide a dark field measurement environment for the test process and avoid the influence of stray light, and the power supply 6 is used to power the entire system. In the following embodiments, the optical imaging system uses an image-side telecentric imaging lens; the detector uses the area array detector E2V-4720; the image acquisition and processing system is a relatively mature system in this field and is used to realize the driving and control of the area array detector. Collect video signals, and store and display the collected image data in real time. The image acquisition and processing system used in this embodiment includes an industrial computer, a programmable logic device, a horizontal and vertical timing drive unit, an analog front-end processing unit, a CCD bias voltage generation unit, an image data transmission unit, an internal communication interface, and an internal telemetry signal generation Unit; the components listed above are only used to further disclose this embodiment and are not intended to limit this solution. For those skilled in the art, they can replace relevant components in parallel according to actual test requirements.

Referring to Figure 3, the invention describes a multi-band strip filter optical parameter testing method, including the following steps:

a) Adjust the continuous tunable uniform monochromatic illumination light source component to output a spectrum with a center wavelength of 490nm. This spectrum is a channel-one spectrum. Adjust the two-dimensional adjustment frame so that the multi-band strip filter is positioned on the object surface of the optical imaging system and is clear. imaging;

b) Set the detector exposure time to 8ms, continuously capture 10 images in a bright field environment, and average to obtain the image μ _{y·filter·light} (i,j), where i and j represent the rows and columns of the output image respectively;

c) Set the detector exposure time to 8ms, continuously capture 10 images in a dark field environment, and average the image μ _y·dark·t1 (i,j);

d) Move the multi-band strip filter out of the optical path, and the continuously tunable and uniform monochromatic illumination source directly illuminates the optical imaging system and detector;

e) Set the detector exposure time to 8ms, continuously capture 10 images in a bright field environment, and average the image μ _y·light (i,j);

f) Set the detector exposure time to 0.5ms. In a bright field environment, the detector output DN is 5% saturation value. Take 10 images continuously and average them to obtain the image μ _y·light·t2 (i,j);

g) Set the detector exposure time to 0.5ms, continuously capture 10 images in a dark field environment, and average the image μ _y·dark·t2 (i,j);

h) Set the detector exposure time to 10ms. The bright field environment makes the detector output DN a 95% saturation value. Take n images continuously and average them to obtain the image μ _y·light·t3 (i,j);

i) Set the detector exposure time to 10ms, continuously capture 10 images in a dark field environment, and average the image μ _y·dark·t3 (i,j);

j) Adjust the continuous tunable uniform monochromatic illumination light source assembly to output channel two-channel five spectra (550nm, 670nm, 870nm, 910nm) respectively, and repeat steps a-i;

k) When the test is completed, turn off the power.

The above-mentioned multi-band strip filter optical parameter testing method also includes the following data processing steps:

a) Background deduction: Subtract the dark field image from the average bright field image to obtain the effective signal, refer to formulas (1)-(4):

U _y·filter (i,j)＝μ _{y·filter·light} (i,j)-μ _y·dark·t1 (i,j) (1)

U _y (i,j)＝μ _y·light (i,j)-μ _y·dark·t1 (i,j) (2)

U _y·Low (i,j)＝μ _y·light·t2 (i,j)-μ _y·dark·t2 (i,j) (3)

U _y·High (i,j)＝μ _y·light·t3 (i,j)-μ _y·dark·t3 (i,j) (4)

b) Non-uniformity correction: To correct the test error caused by the non-uniformity of the optical imaging system and the detector itself, refer to formulas (5)-(8); where, and/> are the mean values of U _y·High (i,j) and U _y·Low (i,j) respectively, G and O are the non-uniformity correction coefficients;

Y _{correction·filter} (i,j)＝G(i,j)×U _y·filter (i,j)+O(i,j) (7)

Y _correction (i,j)＝G(i,j)×U _y (i,j)+O(i,j) (8)

c) Two-dimensional distribution of transmittance: divide the corrected images with and without multi-band filters to obtain the two-dimensional distribution of transmittance T of different spectra. Refer to the following formula (9):

Taking the 670nm spectral channel as an example, Figure 4 shows the processed transmittance distribution image. Take the 200th column of data and obtain the transmittance curve distribution as shown in Figure 5. It can be seen that the transmittance curve is relatively flat in rows 578-676. , the non-uniformity in this interval is about 3.08%.

Claims (3)

1. The multiband strip optical filter optical parameter testing method is characterized by being completed based on a multiband strip optical filter optical parameter testing system, wherein the multiband strip optical filter optical parameter testing system comprises a continuously tunable uniform monochromatic illumination light source assembly, a two-dimensional adjusting frame, a camera assembly, an image acquisition processing system and a power supply; the two-dimensional adjusting frame is used for adjusting the position of the multiband strip-shaped optical filter to enable the multiband strip-shaped optical filter to be located at the object plane position of the camera component; the camera assembly comprises an optical imaging system and a detector, and is used for clearly imaging the multiband strip filter; the image acquisition processing system is used for carrying out numerical analysis on the image output by the camera component; the power supply is used for supplying power to the whole test system; the two-dimensional adjusting frame and the camera component are both arranged in the camera bellows; the multiband strip-shaped optical filter comprises a substrate and five narrowband spectrum channel optical filters fixed on the substrate, wherein the five narrowband spectrum channel optical filters sequentially form a first channel, a second channel, a third channel, a fourth channel and a fifth channel;

a multi-band strip filter optical parameter testing method comprises the following steps:

a) Adjusting the continuous tunable uniform monochromatic illumination light source assembly to enable the continuous tunable uniform monochromatic illumination light source assembly to output a channel spectrum, and adjusting the two-dimensional adjusting frame to enable the multiband strip-shaped optical filter to be located at the object plane position of the optical imaging system and clearly image;

b) Setting the exposure time t1 of the detector, continuously shooting n images in a bright field environment, and averaging to obtain an imageWhere i, j represent the rows and columns of the output image, respectively;

c) Setting the exposure time of the detector as t1, continuously shooting n images in dark field environment, and averaging to obtain an image；

d) Moving the multiband strip filter out of the light path, and continuously and uniformly tuning a monochromatic illumination light source to directly illuminate an optical imaging system and a detector;

e) Setting the exposure time of the detector as t1, continuously shooting n images in a bright field environment, and averaging to obtain an image；

f) Setting the exposure time of the detector to be t2, enabling the detector output DN to be 5% saturation value in a bright field environment, continuously shooting n images, and averaging to obtain an image；

g) Setting the exposure time of the detector to be t2, continuously shooting n images in a dark field environment, and averaging to obtain an image；

h) Setting the exposure time of the detector to be t3, enabling the detector output DN to be 95% saturation value in a bright field environment, continuously shooting n images, and averaging to obtain an image；

i) Setting the exposure time of the detector to be t3, continuously shooting n images in a dark field environment, and averaging to obtain an image；

j) C, adjusting the continuous tunable uniform monochromatic illumination light source assembly, respectively outputting channel two-channel five spectrums, and repeating the steps a-i;

k) The test is completed, and the power supply is turned off;

the method comprises the following data processing steps:

a) Background subtraction: subtracting the dark field image from the averaged bright field image to obtain an effective signal, and referring to formulas (1) - (4):

（1）

（2）

（3）

（4）

b) Non-uniformity correction: correcting test errors caused by non-uniformity of the optical imaging system and the detector, referring to formulas (5) - (8); wherein,and->Respectively->And->G and O are non-uniformity correction coefficients;

（5）

（6）

（7）

（8）

c) Transmittance two-dimensional distribution: dividing the corrected image with or without the multiband filter to obtain transmittance two-dimensional distribution T of different spectrums, and referring to the following formula (9):

（9）。

2. the method for testing optical parameters of a multiband strip filter according to claim 1, wherein: the continuously tunable uniform monochromatic illumination light source component comprises an ellipsoidal mirror, a grating monochromator and an integrating sphere, and the outlet and inlet directions of the integrating sphere are 90 degrees; the method comprises the steps that a xenon lamp is arranged at the position of a primary focus of an ellipsoidal mirror, a slit inlet of a grating monochromator is arranged at the position of a secondary focus of the ellipsoidal mirror, an outlet of the grating monochromator is communicated with an inlet of an integrating sphere, and an anti-secondary spectrum filter is arranged at the position of the inlet of the grating monochromator; a circulating water cooling device is arranged between the ellipsoidal mirror and the secondary spectral filter.

3. The method for testing optical parameters of a multiband strip filter according to claim 2, wherein: the circulating water cooling device comprises a water cooling filter and a circulating water pump which forms a circulating water path through a water pipe and the water cooling filter.