A quantum-dot semiconductor optical amplifier (QD-SOA) has the characteristics of picosecond gain recovery time and ultrafast carrier concentration recovery. The combination of photonic crystal (PC) and QD-SOA has the advantages of strong nonlinear effect, less absorption loss, high power transmission, and low power consumption. The wavelength conversion characteristics of photonic crystal-quantum dot semiconductor optical amplifiers (PC-QDSOAs) are studied, the influences of maximum mode gain, pumping power, detecting power, and active region length on the Q-factor of PC-QDSOA wavelength conversion are analyzed, and the relationships among the injection current, pumping power, detecting power, active region length, and extinction ratio of PC-QDSOA wavelength conversion are analyzed in detail. The simulation results of QD-SOA and PC-QDSOA are compared. The results show that the values of Q-factor and extinction ratio of PC-QDSOA are greater that that of QD-SOA, which indicates that the output signal quality, signal transmission efficiency, and conversion performance of PC-QDSOA are better than that of QD-SOA. The research results have guiding significance for the application of PC-QDSOA.

Based on the power coupling theory, the characteristics of optical signal power and inter-core crosstalk (ICXT) are studied in weakly coupled multicore fiber (MCF) transmission systems with multiple core interference. The corresponding analytical expressions of the optical signal power and ICXT are also derived. Simulation results show that, after long distance longitudinal transmission, the optical signal power in each core will reach a state of dynamic balance, and a calculation formula for the dynamic balance normalized power is proposed. Moreover, in the MCF transmission systems with multiple core interference, the ICXT contributions induced by different incident cores of the MCF are uncorrelated. The ICXT distribution in the coupled fiber core can be regarded as the accumulation of the ICXT of multiple dual-core single-input cores. Based on the cumulative characteristics of the ICXT, a number of generalized crosstalk estimation mathematical models are obtained, which improve the analysis theory of ICXT in the case of multiple core interference and provide a good theoretical analysis tool for this situation.

A fiber optic gyroscope design based on a new phase modulator mid-mounted structure is proposed. The scheme not only can overcome the shortcoming that the modulation frequency of the traditional fiber optic gyroscope is limited to the eigen frequency, but also can suppress the backscatter noise and polarization coupling noise. Theoretical analysis and experimental results show that the proposed structure can control the phase of the backscattered wave to the order of 10 -5, and the polarization coupling noise can be suppressed to 5×10 -8 (°)/Hz 1/2. In addition, this mid-mounted structure can improve the bias stability of the gyroscope, which is increased from 0.11878 (°)/h to 0.09110 (°)/h. This scheme overcomes the technical problem of the fiber optic gyroscope influenced by eigen frequency, and provides a new way to suppress noise and improve accuracy.

Distributed optical fiber sensors have been intensively used to measure the strain, temperature, displacement, and pressure of long-distance, large-span, and super high-rise structures with long term and high precision, due to the unique advantages of high sensitivity, anti-corrosion, immune to electromagnetic interference, absolute measurement, small size and light weight. When the host material is steel structures, optical fiber sensors have often been attached on the surface. For the different properties of silica fiber and steel material, obvious interfacial feature exists. The interfacial debonding often occurs between the surface-attached sensors and the monitored structures during the measurement. To guarantee the effective and accurate measurement, study on the occurrence and propagation of interfacial debonding should be performed. For this reason, strain transfer theory is adopted to discuss the interfacial interaction between the sensor and the structure and the influence of interfacial debonding on measurement. Experiments have been conducted to validate the effectiveness of the theoretical model. The close-form equation of interfacial shear stress with the non-uniform constraint considered has been given, and sensitivity of the correlated physical parameters has been discussed, suggestions are proposed for the design of distributed optical fiber sensors in practical engineering.

First, a composite structure composed of gold grating, medium, and gold film is designed on the end face of optical fiber, and the variation of various resonance modes with the thickness of medium layer and their field distribution characteristics are studied. Then, the waveguide resonant modes limited to the nanometer spacing between the gold grating and the gold film are studied. The different order of nanometer resonance effects are studied by the variation of the reflection spectrum and the electric field distribution characteristics of the resonant mode. In addition, the simulation calculation of gold grating width, thickness, and cycle, intermediate medium layer refractive index and thickness of gold film changes on the spectral characteristics and the effect of nano-resonator based on waveguide mode interference phase difference formula of the qualitative analysis of the change of resonance frequency, and calculate the obtained nano-cavity on the sensitivity of the refractive index and the length of cavity medium. Finally, a micro-displacement platform is built to verify the Fabry-Perot interference formed spectrum with the distance between the optical fiber end face and the gold film, and the realization scheme of the optical fiber end face nano-resonance structure is proposed.

In this paper, a two-core terahertz fiber directional coupler is proposed. Two dielectric cylinders are suspended in the interior of two annular dielectric layers to form two fiber cores. By adjusting the structural parameters, the coupling length of the two polarization modes can be equal, thus realizing polarization independence of the coupling length. The length of the coupler can be one half of the coupling length of the fiber mode, and the transmission loss can be reduced with the short length of the device. The coupler is numerically analyzed by finite element method. The results show that the length of the coupler is 0.535 cm, and the transmission loss of x and y polarization modes is 0.23 dB and 0.19 dB, respectively. Under the premise that the coupling length difference between the two polarization modes is less than 1%, the bandwidth reaches 220 GHz.

Based on the principle of non-imaging optical edge light and the law of geometric optical reflection, the mathematical model of the surface structure of compound parabolic concentrator (CPC) without gap loss is constructed for circular absorber, and the numerical solution of the equal-length reflector is obtained by program calculation. The CPC model without gap loss is verified by a visible laser experimental device, and the results show that the light path calculated by numerical method is consistent with that of laser experiment. Moreover, the CPC without gap loss of a single pair of equal-length reflectors has the largest length of a single equal-length reflector, which is exactly the radius of the absorber. When the number of equal-length reflectors increases from single pair to 6 pairs, the length of a single equal-length reflector decreases from 23.50 mm to 7.65 mm. In the process of practical application, the number of pairs of equal-length reflectors should not be too much.

The amount of photosensitizer in holographic recording media is very small, but it plays a decisive role in the selection of recording wavelength. A series of cyclopentanone photosensitizers are designed and synthesized for 532 nm laser, and their spectral characteristics, reaction kinetics to induce monomer polymerization, and application performance in photopolymer for holographic recording are studied. The results show that the sample containing BTMI (2,5-bis(2-(1,3,3-trimethylindolin-2-ylidene)ethylidene)cyclopentanone) has the best holographic recording performance, and the diffraction efficiency of single grating reaches 90% when the total exposure dosage is 64 mJ/cm 2, the refractive index modulation is 4.14×10 -4, and the full width of half peak of Bragg grating selection angle is 0.90°. Under the exposure of a single laser pulse (wavelength is 532 nm, pulse width is 150--200 ps, energy density is 25 mJ/cm 2), the sample can obtain a holographic grating with diffraction efficiency of 7%, indicating that information can be recorded quickly. By optimizing the formulation, BTMI is expected to be applied to fabricate fast and high density holographic storage media.

A second harmonic de-noising method based on variational mode decomposition and wavelet threshold function is proposed to solve the problem of external noise interference in second harmonic spectra during gas concentration measurement by tunable diode laser absorption spectroscopy (TDLAS). In this paper, we decompose the noisy second harmonic signal to get the useful intrinsic mode functions (IMFs) and reconstruct them. Then, we conduct the de-noising process for the reconstructed signal with the wavelet threshold function. The selection of the optimal balance parameter in the variational mode decomposition is discussed, and the proportional relationship of the optimal balance parameter with the noise in the noisy signal is obtained. Better noise suppression is achieved by changing the threshold function of wavelet transform and thereby altering the high-frequency wavelet coefficients. The de-noising results of actual measurement curves show that the proposed de-noising method can effectively suppress the noise and extract the useful second harmonic signal in the case of a poor signal-to-noise ratio.

In order to solve the problem that the target detection algorithm is difficult to distinguish the mixed pixels and select the threshold value, an adversarial growth (AG) algorithm is proposed according to the similarity of the like pixels. First, the growth tree model is applied to target detection. Then, the AG algorithm is used to improve the growth tree model. Finally, the growth results are obtained under the constraints of the two parameters of omission rate and overlap rate, and the detection results are obtained by further analysis of the growth results. Through the analysis of experimental data, it can be seen that the false alarm rate of AG algorithm is 0.31 percentage points lower than the best result of other four traditional algorithms when the detection probability is 90%. The receiver characteristic curves of the algorithm are all located in the upper left of other algorithms in the four sets of data, which verify the effectiveness of the proposed algorithm, and indicate that the algorithm can better distinguish the mixed pixels, overcome the difficult problem of threshold selection, and improve the efficiency of target detection.

Monitoring the infrared video of the unmanned aerial vehicle (UAV) group is a new hot spot in the security and military fields. Due to the difficulty of acquiring UAV images in complex backgrounds, and the number of images cannot meet the requirements of model training and verification of related algorithms, an image simulation method of infrared UAV based on image derivation is proposed. This method is used to simulate infrared UAVs. This method is used to mix the infrared UAV template image and the infrared background image to generate a large number of UAV target images in different backgrounds. Aiming at the problems of image mixing technology being severely affected by background noise, blurring of drone target edges, and low harmony of synthetic images, an unsupervised generative confrontation network is used to generate a gray-scale constrained image with a high degree of harmony. The target gradient image is used as a joint constraint to solve the Gaussian-Poisson equation, and a mixed image with high consistency with the real image characteristics is obtained. The experimental results show that the mixed image generated by the proposed method has high image harmony and visual authenticity, which shows that the obtained image as an extended sample can effectively improve the performance of the machine learning algorithm.

Computational spectral imaging based on broadband filtering modulation is a new type of computational spectral imaging technology with great application potential in aerospace spectral imaging remote sensing field. At present, this technology is mainly applied to the miniaturization of spectral measurement instruments, but there is a lack of relevant research in the field of spectral imaging remote sensing. Therefore, the feasibility of the application of this technology in the field of spectral imaging remote sensing is studied experimentally. First, the basic principle of broadband filtering modulated spectral imaging is briefly introduced. Then, aiming at the practical demand of space optical remote sensing engineering, the principle prototype system of broadband filtering modulation spectral imaging is built by using color glass filters and industrial camera, and its spectral imaging capability is verified experimentally. Finally, the obtained spectral images are analyzed and evaluated, and the main factors affecting the measurement accuracy of the technology are studied. Experimental results show that the accuracy of spectral reconstruction is about 23%, and the edge of spectral image obtained by this technique is clear, and the noise is about 23 dB.

This paper develops a depth measurement theory related to defect width for the quantitative laser ultrasonic detection of surface defect depth. A depth measurement formula with a width correction item is established, and a concept of defect size ratio is defined. Defects are divided into three types, namely narrow defects, extremely narrow defects, and wide defects. The applicability of the defect depth measurement method in measuring the three types of defects is discussed, and finite element simulation is adopted for verification. Finally, an experimental platform for laser ultrasonic detection is built to conduct depth detection of aluminum alloy samples with surface defects. The results show that quantitative detection of narrow defect depth can be achieved by introducing the width correction item. The average measurement error is less than 5%, which means that accurate measurement of the defect depth has been achieved.

Using ultraviolet stars to finish the on-orbit calibration of far ultraviolet hyperspectral imaging spectrometer is an important step to achieve high precision remote sensing. However, in this way, the on-orbit calibration coefficients can not be directly used in target inversion. Therefore, the conversion of on-orbit calibration coefficients is of great significance to improve the on-orbit calibration accuracy of instrument. In this paper, the conversion process of the calibration coefficients is derived, a new equation of the calibration coefficients is given, the related verification experiments are carried out by using the developed instrument. The results show that the accuracy of target inversion can be improved by 40% by using the modified calibration coefficients.

The linear polarization measurement technology based on spectral modulation can modulate the polarization information of incident light to the spectral dimension through the spectral modulation module. The spectral modulation module is composed of a achromatic quarter-wave plate, a multiple-order wave plate and a polarization beam splitter, which can obtain the linear polarization and spectral information of the target in a single measurement. With the combination of modulation module and grating spectrometer, a dual-channel polarization measurement system is designed. The polarization measurement model of the system is derived, the influence of spectral broadening on the modulation spectrum is analyzed, and the partial periodic least squares curve fitting method is used to demodulate the polarization information. Moreover, a test device is built to verify the performance of the measurement system. First, the complete linear polarization light is used to calibrate the retardation of the multiple-order wave plate and the polarimetric efficiency of the system. Then, the polarization measurement accuracy of the system is verified by using the variable polarization light source. The experimental results show that maximum absolute deviation between the theoretical value and the measured value of degree of linear polarization of the variable polarization light source is 1.11%, and the maximum deviation of angle of linear polarization is 0.7°, which means the proposed system has high polarization measurement accuracy.

In order to study the transmission characteristics of blue-green laser across the the air-sea cross-medium, the downlink transmission model of blue-green laser through the sea surface-bubble layer is developed based on Kirchhoff approximation, Mie theory, and Beer theory for the air-sea cross-medium interface and the the subsurface bubble layer. The factors such as the fluctuation of sea surface height affected by wind speed, the change of bubble concentration in seawater, the mixing of clean bubbles and thin film-covered bubbles in seawater are fully considered. The relationship among the transmittance of blue-green laser passing through the sea surface-bubble layer, wind speed, the transmission depth in seawater, and the angle between receiving plane and transmitting plane is calculated numerically. The results show that the transmittance of the blue-green laser passing through the air-sea interface and the seawater mainly depends on the wind speed and the laser transmission depth in the seawater. With the increase of wind speed, the sea surface roughness and the concentration of bubbles in the upper ocean increase, and the laser transmittance decreases. Compared with seawater, the effect of bubble layer on laser transmittance decreases with the increase of depth. For bubbles with radii greater than 10 μm, the covering of the protein film has little effect on the attenuation of the blue-green laser.

In order to improve the detector array target laser power density measurement range and incident angle tolerance, starting from the protective sampling attenuation structure, based on the theory of total reflection and transmission scattering, we design a protective sampling structure composed by gold-plated copper base panel, fiber optic sampling, and scattering attenuation. At the same time, the designed structure is applied to detector array target system. Through thermal analysis of laser irradiation target, ray tracing simulation, and laser point-by-point scanning experiment, the anti-laser damage ability, angle characteristics, and channel response consistency of the system are analyzed and tested. The results show that the protective sampling attenuation structure can withstand long time irradiation of high power density laser. When the incidence angle ranges from 0° to 30°, the deviation of measured angle characteristic coefficient with respect to normal incidence is less than 4% after cosine correction. The standard deviation of response inconsistency among channel units all less than 2%.

In view of the spatial feature correlation of adjacent station clouds collected by ground three-dimensional laser scanners, and a large number of line-planar features in urban buildings, a point cloud registration method based on line-planar feature constraints described by dual quaternion is proposed. This method not only uses dual quaternion to describe spatial transformation parameters, but also takes into account the scale factor. The objective function of spatial similarity transformation is constructed according to the geometric relationship between line-planar, as well as the intersection point and angle caused by the intersection of line-planar as registration constraints. The adjustment model is constructed by using the least square criterion to calculate the relevant parameters of spatial similarity transformation. In order to avoid the problem of iterative non-convergence caused by inappropriate initial values, the Levenberg-Marquardt method is applied to the solution of the adjustment model. Finally, the correctness and feasibility of the method are analyzed by experiments. The results show that the registration accuracy of the proposed method is higher than that of the point cloud registration method considering only linear of planar feature constraints, and the adjustment model solved by Levenberg-Marquardt method can converge correctly under any given initial value.

The propagation behavior of an electromagnetic wave in a medium depends heavily on the shape of the iso-frequency contour of the medium. The iso-frequency plane of a hyperbolic metamaterial is an open hyperboloid that supports the propagation of any large wave vector. The large wave vector component of an electromagnetic wave manifested as an evanescent wave in a conventional environment can be converted into a propagation field to achieve more novel electromagnetic propagation effects. In this paper, on the basis of a metamaterial with a hyperbolic iso-frequency plane, a novel material that has the properties of both hyperbolic metamaterials and zero-refractive-index materials is prepared by adjusting the shape of the iso-frequency contour. It can not only support the highly directional and unidirectional propagation of the large wave vector, but also refract an any angle incident electromagnetic wave at a zero angle. Therefore, it can be used to achieve subwavelength focusing and super resolution. These effects, namely the highly directional and unidirectional propagation, subwavelength focusing, and super resolution, are verified experimentally in the microwave domain. This research offers more possibilities for the theoretical and application studies of hyperbolic metamaterials.

According to the (3+1)-dimensional Schrödinger equation for the propagation of paraxial beams in strongly nonlocal nonlinear media (SNNM), the analytical solution of spatiotemporal controllable Airy-Ince-Gaussian (CAiIG) beam in elliptic coordinates is obtained. CAiIG beams are obtained by time-domain modulation of spatial Ince-Gaussian beams by Airy pulses with different initial velocities. The propagation process of CAiIG beam in SNNM is discussed by adjusting the ratio of initial incident power to critical power, initial incident velocity and ellipse parameter. The spatiotemporal CAiIG beam keeps non-dispersive characteristics in the process of propagation. According to the ratio of the initial incident power to the critical power, the beam width oscillates periodically in space (the power ratio is not equal to 1) or remains constant (the power ratio is equal to 1). The continuous conversion among spatiotemporal Airy-Ince-Gaussian beam, spatiotemporal Airy-Laguerre-Gaussian beam and spatiotemporal Airy-Hermite-Gaussian beam can be realized by adjusting the ellipse parameter. Moreover, the energy flow distributions on several propagation cross sections of CAiIG beams propagating in breathing state in SNNM are given.

In laser guidance, the optical quality of four-quadrant detector lens determines the accuracy of target positioning. In view of this, a non-contact detection system of the optical quality of the four-quadrant detector lens is designed. The system can detect the optical quality of the four-quadrant detector lens in batches online. First, the laser light source is shaped, expanded, and collimated into a flat-top beam. Then, the image is developed on the frosted glass through the four-quadrant detector lens. Finally, the shape, position, and uniformity of the spot are detected by the non-contact microscopic objective lens with long working distance. The design results show that the system can effectively batch detect the optical quality of the four-quadrant detector lens, thus improving the quality control of the four-quadrant detector lens, and helping to improve the overall quality of the four-quadrant laser guidance detection system.

A mag-optical modulator based on periodic parity-time (PT) symmetry structure is proposed, which consists of hydro-based MnFe2O4 magnetofluid layer in the middle and periodic PT symmetry units on both sides. The high extinction ratio modulation with gain is realized by using the magneto-optic effect of the magnetic fluid. The transfer matrix method is used to simulate and analyze the structure, it turns out that, for the incident light wave whose wavelength is in the low transmission region of the structure gap band(in the wavelength range from 1513 nm to 1587 nm with 1550 nm as the center), the maximum gain of the modulator for incident light is close to 25 dB, the maximum and the minimum extinction ratio are close to 60 dB and 30 dB, respectively. Simultaneously, the average modulation sensitivity of incident light wave transmission and wavelength shift can reach the maximum of 74.51 dB and 108.2 nm, respectively.

Infrared polarization imaging technology has many advantages, such as improving target recognition rate and identifying camouflage targets, but the infrared polarization characteristics of targets are easy to be disturbed in complex environment, resulting in misjudgment and omission. To study the influence of ambient thermal radiation on the infrared polarization characteristics of the targets, the analytical model for the degree of infrared linear polarization of target surface under heat source irradiation is derived based on the polarization bidirectional reflection distribution function. Theoretical simulation and experimental verification show that the ambient thermal radiation will affect the infrared polarization characteristics of the targets. When the intensity of ambient thermal radiation is smaller than that of the target spontaneous thermal radiation, the degree of infrared linear polarization is negatively correlated with the intensity of ambient thermal radiation, which means the greater the intensity of ambient thermal radiation, the smaller the degree of infrared linear polarization. When the intensity of ambient thermal radiation is greater than that of the target spontaneous thermal radiation, the degree of infrared linear polarization is positively correlated with the intensity of ambient thermal radiation, which means the greater the intensity of ambient thermal radiation, the greater the degree of infrared linear polarization. The above results indicate that the degree of infrared linear polarization will change regularly when the targets are affected by external thermal radiation.

The study of polarization characteristics of sea surface scene is of great significance to infrared polarization target detection, and sea surface modeling is the key step of sea surface polarization simulation. The influence of wave spectrum model and spatial sampling points on sea surface modeling is analyzed, and a correction method is established, which superimposes the high frequency component of wave spectrum to the low frequency component in the exponential form. Combining RadTherm software with the polarization degree calculation model, the long-wave infrared polarization characteristics of simulated sea surface generated by the proposed method and the traditional method are compared.The simulation results show that the proposed method can effectively improve the consistency among the height distribution of simulated sea surface, the microfacet slope distribution of simulated sea surface and the measured sea surface data at a low spatial sampling rate.

A wide band high-reflection film with low polarization effect is optimized by using genetic algorithm, and the polarization aberration correction of the reflective telescope in different wave bands is realized. The polarization aberration function is used to analyze the influence of metal film and low polarization film on the polarization aberration of Cassegrain telescope. The simulation results show that the diattenuation aberration of the telescope coated with low polarization film is slightly smaller than that of the telescope coated with aluminum film, while the phase retardance aberration decreases obviously, which decreases by 1.13 °, 1.00 °and 0.68 °at the wavelength of 355, 532 and 1064 nm, respectively. Finally, the influence of the selected film on the depolarization parameter error in different wavebands and fields of view is calculated according to the relationship between the Mueller matrix of the telescope and the atmospheric depolarization parameters. The results show that the measurement accuracy of depolarization parameter after polarization aberration correction of telescope will be improved.

The topological charge variation of a vortex beam passing through a diffraction plate with a Fermat spiral microporous structure and the diffraction and focusing characteristics of the beam intensity distribution are studied theoretically and experimentally. A positive lens is used to focus the diffracted beam, and the variation of the intensity distribution behind the focal plane is observed and studied. The intensity distribution of the innermost ring of the diffracted beam has about five stages before and after the beam waist. This variation trend is applicable to the case of the diffracted plate with different Fermat spirals distributed by the vortex beam through the microhole, whether the rotation direction of the spiral is changed or the number of spiral structures is changed. The change of topological charge is verified by the interference between diffraction beam and spherical wave. The results show that the diffraction can generate a new topological charge, which is related to the phase front of the incident vortex beam and the relative rotation of the helical microhole array.

The jitter caused by onboard motion components is an important factor affecting the quality of ultra-high-resolution and super-maneuverability imaging. Given that it is difficult to conduct accurate operational detection and identification of the jitter signal, this paper proposes a jitter detection method based on rolling shutter CMOS imaging for space cameras and verifies and evaluates the method with digital orthophoto map/digital elevation model (DOM/DEM) data by using high-frequency angular displacement and high-precision reference. A Gaofen satellite launched in 2020 is discussed as an example. The analysis results show that the proposed detection method can effectively identify the jitter characteristics in the imaging process of space cameras, and the jitter frequency is mainly concentrated at about 156 Hz. The relative geometric accuracy of panchromatic images after compensation is improved by about 1.2 pixel.

Weber distribution has better optimization accuracy and global search ability in nonlinear optimization problems. For this reason, a cuckoo search (WCS) algorithm based on Weber distribution is proposed to solve the problem of particle size distribution inversion. The WCS algorithm is used to invert the particle size distribution of unimodal and bimodal particle systems which follow Johnson’s SB distribution, Rosin-Rammler distribution, and normal distribution, and the results are compared with those of other traditional algorithms. The results show that the overall performance of the WCS algorithm is better than that of the artificial fish swarm algorithm and the artificial bee colony algorithm, and the standard deviation of the improved four heavy-tailed distribution CS algorithm is 2-3 orders of magnitude higher than the original CS algorithm. Compared with the other three heavy-tailed distributions, the relative root mean square error of the WCS algorithm can be reduced by at least 1/2 when the scattering light energy of the objective function is added into the noise. The small angle forward scattering measurement system is used to study the unimodal particle system and bimodal mixed particle system. It is found that the relative root mean square error of the WCS algorithm is about 40% lower than that of the original CS algorithm.

The influence of different chromaticity coordinate spaces and different scale factors derived from the tristimulus values L, M, and S of the cone response on the calculation of correlated color temperature (CCT) is studied, and the difference between the calculated CCT and the standard CCT is compared. Tests are carried out on a data set containing 401 spectral power distributions collected by Houser et al. The test results show that the uc-vc space directly derived from the calculated L, M, and S when the scale factors are all 1 is the best, and the absolute differences of the mean CCT, the median CCT and the maximum CCT are 48, 31 and 851 K, respectively. If the L, M, S are converted to the uF-vF space derived from the tristimulus value space XFYFZF defined by the color matching function to calculate the CCT, the mean CCT difference, the median CCT difference and the maximum CCT difference between the calculated CCT and the standard CCT are 42, 21 and 540 K, respectively.