Frequency-Modulated Microscopic Imaging for Background Noise Removal
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Solution Overview
Problem
Conventional far-field optical microscopy is limited by the diffraction limit, and STED microscopy suffers from background noise and photobleaching, which reduces sample observability and imaging resolution.
Innovation Solution
A device utilizing frequency-domain modulation with a laser system, including a glan prism, electro-optic modulator, vortex phase plate, and lock-in amplifier to process signals, effectively removing background noise and improving imaging speed and resolution by modulating laser beams with different frequencies and polarizations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If depletion beam power is increased to improve resolution in STED microscopy, then imaging resolution is improved, but photobleaching and photodamage effects increase substantially
Solution Approach 1:
The patent applies periodic modulation to the depletion beam using an electro-optic modulator, switching the beam on and off at specific frequencies. This periodic action allows the system to achieve high resolution during the 'on' periods while reducing cumulative photodamage during 'off' periods, thus resolving the contradiction between improving resolution and reducing harmful effects.
Solution Approach 2:
The patent dynamically adjusts the depletion beam characteristics by modulating its intensity and timing rather than using a static high-power beam. The electro-optic modulator enables real-time dynamic control of the beam properties, allowing the system to optimize resolution while minimizing photodamage through controlled temporal variations in beam intensity.
2Measurement precision
If depletion beam power is increased to improve resolution, then imaging resolution is improved, but background noise from secondary excitation increases
Solution Approach 1:
By modulating the depletion beam at specific frequencies and using lock-in detection at matching frequencies, the system can distinguish between signal and background noise. The periodic modulation creates frequency-specific signal components that can be separated from continuous background noise through frequency-domain analysis, resolving the contradiction between high resolution and low background noise.
Solution Approach 2:
The patent changes the temporal parameters of the depletion beam by introducing frequency modulation. This parameter change transforms the static high-power beam into a dynamically modulated beam, enabling the system to achieve high resolution while reducing background noise through frequency-selective detection methods.
3Device complexity
If conventional far-field optical microscopy is used, then device complexity is low, but imaging resolution is limited by diffraction to about half a wavelength
Solution Approach 1:
The patent introduces an electro-optic modulator as an intermediary component between the laser source and the sample. This intermediary enables frequency-domain modulation of the depletion beam, allowing the system to overcome diffraction limits without requiring fundamentally different optical hardware, thus resolving the contradiction between device simplicity and high resolution.
Solution Approach 2:
The patent replaces complex mechanical scanning and focusing mechanisms with electro-optic modulation and frequency-domain processing. Instead of using mechanical means to achieve super-resolution, the system uses electrical modulation of light properties, simplifying the mechanical complexity while achieving enhanced resolution through signal processing in the frequency domain.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method and device achieve fast imaging with reduced background noise and high resolution by quantitatively removing secondary excitation fluorescence and incomplete depletion signals, enhancing imaging quality.
Implementation Method 1
a glan prism configured to change polarization states of a laser beam emitted by the laser device to obtain line-polarized light
Implementation Method 2
an electro-optic modulator configured to modulate intensities of two beams of the line-polarized light corresponding to the high-power laser and the low-power laser
Implementation Method 3
a 0 ̃2π vortex phase plate configured to perform phase modulation of the high-power laser; a microscope objective configured to project a light beam emitted from the field lens onto the sample to be measured to make that the high-power laser with phase modulation converges into a hollow spot on the sample
Implementation Method 4
a quarter-wave plate configured to change polarization states of the two beams of the line-polarized light to obtain two beams of right-handed circularly polarized light
Implementation Method 5
a lock-in amplifier configured to demodulate received signal light at a specific frequency to obtain an image at a corresponding scanning position
Data Source
AI summary
The present disclosure relates to a method and device for removing background noise in microscopic imaging based on frequency-domain modulation. The method includes irradiating a surface of a sample to be measured by simultaneously irradiating the surface of the sample by utilizing two beams from two laser devices. One of the two beams passes through a 0˜2π vortex phase plate and then focuses on the sample to be measured to form a high-energy hollow spot, and the other of the two beams focuses on the sample to be measured to form a low-energy solid spot. The method further includes modulating the two beams in time-domain simultaneously using an electro-optic modulator and demodulating signal light at different frequencies using a lock-in amplifier, then removing the background noise by a differential process to realize a high signal-to-noise ratio super-resolution image.