Qingdao Senquan Optoelectronics Co., Ltd
panyue@sourcescn.com
13475860763
501, Building 57, Optics Valley Software Park, 396 Emeishan Road, Huangdao District, Qingdao City, Shandong Province
Comparison between Liquid Crystal Tunable Filter (LCTF) and Push Sweep Hyperspectral Camera
thispushWen CongSpeed, sensitivity, optical extension, and applicability to static and dynamic targetsIn terms of aspect, a comprehensive comparison was made between hyperspectral cameras based on liquid crystal tunable filters (LCTF) and push scan hyperspectral cameras.
Ø Speed comparison
LCD Tunable Filter Camera
l 速度限制：Due to the tuning speed limitation of liquid crystal filters, the tuning time for each wavelength is usually withinWithin the range of milliseconds to seconds.
l Full spectrum acquisition：Sequential scanning is required for each wavelength, which increases the acquisition time.
l frame rate：Lower (about 10-100 Hz)
l Application scenarios：Suitable for static targets.
Push broom camera
l Speed advantage：Can simultaneously collect all spectral information of a whole row
l Full spectrum acquisition：Due to simultaneous spectral detection, the collection speed is fast.
l frame rate：Can exceedHundreds to thousands of hoursz.
l Application scenarios：perfectly suitedHigh speed dynamic target.
l Speed winner：Push broom camera
Ø Sensitivity comparison
LCD Tunable Filter Camera
l Optical flux：Due to the use of sequential filtering methods, the optical flux is limited.
l luminous efficiency：Except for the selected wavelength, most of the incident light is blocked.
l quantum efficiency：Due to the losses of liquid crystal optical devices, the quantum efficiency is relatively low.
l performance：needHigh intensity light source.
Push broom camera
l Optical flux：Better, dispersive elements can maximize optical collection efficiency.
l luminous efficiency：Efficiently utilize the entire incident spectrum.
l quantum efficiency：Higher, especially when paired with Xian input sensors such as sCMOS and InGaAs sensors.
l performance：It performs well under low light conditions.
l Sensitivity winner：Push broom camera
Ø Performance comparison between static and dynamic targets
feature |
LCD Tunable Filter Camera |
Push broom camera |
The winner |
Static target |
ZuiHeshi |
Need to scan motion |
LCTF |
Dynamic target |
Due to the challenging nature of sequential scanning |
ZuiHeshi |
Pushbroom |
l Dynamic target winner：Push broom camera
l Static target winner：LCTF camera
Ø Comparison of Light Expansion Quantity
LCD Tunable Filter Camera
l Pixel related angle acceptance：The wavelength transmittance depends on the incident angle and requires strict collimation.
l Sequential wavelength scanning：Measure only one wavelength at a time and discard most of the incident light.
l Limited Field of View (FOV)：The narrow angle acceptance reduces the é tendue.
Push broom camera
l Full spectrum capture：All photons are efficiently utilized, maximizing the luminous flux.
l Greater acceptance angle：Acceptable a wider range of light angles to increase efficiency.
l Line lighting：Capturing an entire row significantly improves photon collection efficiency.
l Winner of Light Expansion Quantity：Push broom camera
Ø Comparison Table of Direct Optical Expansion
factor |
Liquid Crystal Tunable Filter (LCTF)camera |
Push broom camera |
The winner |
Light expansion amount (G=A ·Ω) |
Lower due to collimation constraints |
Higher due to full spectrum capture |
Pushbroom |
luminous flux |
Low blocking most of the incident light |
High utilization of all light sources |
Pushbroom |
Angle acceptance |
Low - requires collimation |
Higher and wider angle acceptance |
Pushbroom |
Photon utilization efficiency |
Difference - one wavelength at a time |
High - Measure the full spectrum of each line |
Pushbroom |
sensitivity |
lower |
higher |
Pushbroom |
l Overall winner：Push broom camera
Ø Under what circumstances are liquid crystal tunable filters still applicable?
Although push broom cameras typically outperform LCTFs in terms of light expansion, sensitivity, and speed, LCTFs still have advantages in the following scenarios：
l Applications requiring only a few key wavelengths(such as medical imaging, fluorescence detection).
l Unrestricted scanning timeControllable static environment.
l toCost sensitiveThe application of LCTF is usually slightly cheaper than push sweep systems.
However, forPush scan cameras are a better choice for real-time, high-speed, or high-sensitivity applications.
Ø System design suggestions
High speed dynamic application：
l Using equipmentPush scan cameras with high-speed CMOS or InGaAs sensors.
l Adopting optimized lighting sources to maximizeMaximize signal-to-noise ratio.
l Ensure motion synchronization between the target and the imaging system,Avoid spectral misalignment.
Static or laboratory applications：
l When neededWhen choosing variable multispectral rather than pursuing speedUsing LCTF camera
l Integrated high-intensity light sourceTo compensate for light loss
l if neededObtain spatially resolved hyperspectral images, can use a mechanical translation platform
Economically efficient deployment：
If speed is not the key factor, LCTF based solutions may reduce overall system costs, but this is not necessarily the case
Maximize the amount of light expansion and sensitivity：
l Equip the push scan camera with high light expansion optical components（Larger aperture, efficient collimator)
l For both LCTF and push sweep systems, high-efficiency optical coatings are chosen to reduce losses
In summary, push scan hyperspectral cameras outperform LCTF cameras in the following aspects：
n Speed (faster acquisition through simultaneous capture of spectra)
n Sensitivity (higher quantum efficiency and better luminous flux)
n Light expansion capacity (larger acceptance angle and higher light efficiency)
n Dynamic target performance (very suitable for sports scenes)
However, LCTF cameras are still practical in economically efficient solutions where static applications and capture speed are not the primary considerations.
For the pursuitSpectral imaging performanceIn most high-speed and high-sensitivity applications,Push scan camera is the best choice.