Filters USED IN SCANNING ELECTRON MICROSCOPEpptx

SEM'S FILTERS

1. Filters Optical microscope

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3. Content Layout What are the filters? How filters are made? Optical microscope filters: use and work How they are use to transmit light? Types of filter Why filters are needed in optical microscopy? Applications of optical filters. Advantages Disadvantages Conclusion

4. What are Filters? An optical filter selectively transmits one portion of the optical spectrum, while rejecting other portions . Filters , in optical microscope, are used to selectively transmit or block certain wavelengths of light. They are commonly used to enhance the contrast , improve visibility , or select specific wavelengths for observation..........

5. What are Filters? They are designed to manipulate light in various ways , allowing us to control the intensity, color , and polarization . The light source will emit light of all seven colors- violet, indigo, blue, green, yellow, orange and red. Every color will produce an image of different temperature, contrast, & brightness . Optical filters are frequently used to isolate specific wavelengths of light for data collection and analysis, for example in fluorescence microscopy.

6. Optical Microscopic Filters Optical microscopic filters  are made for use in microscopes manufactured by Optolong and it is an excellent optical element. These filters are specially and carefully designed to operate how light links with specimens under observation, increasing the quality and contrast of microscopic images. It offers a broad range of microscope filters with specific functions.

7. Goals of Microscopic Filters Wavelength Selection Contrast Enhancement Image Clarity Light Source Control Fluorescence Imaging

8. How filters transmit light in Optical Microscopes? Optical filters in microscopes transmit light by selectively passing certain wavelengths of light, while absorbing or reflecting the rest.  The filters are made of a substrate with a specialized optical coating that modifies the substrate's refractive index .  The coating's thickness & material are carefully controlled to allow the desired wavelengths to pass through, while blocking the rest.

9. How to make Optical Filters? Here are some methods for the formation of optical filters : Thin Film Deposition method : In this technique multiple layers of different material are deposited on the substrate by using techniques like physical vapor deposition (PVD) or chemical vapor deposition (CVD).This is done to transmit or reflect specific wavelength of light by controlling thickness and composition of material. This method is often used to create band pass-, long pass-, short pass-, & notch- filters. Photolithography : This technique involves using photoresist materials and light patterning to create intricate patterns on a substrate. By selectively etching or depositing materials onto the substrate following the pattern, optical filters with precise geometries and properties can be fabricated. This technique is mostly used in semiconductor industries. Dichroic Coating : This technique involves coating of thin layers of materials with different refractive indices on substrate. These layers selectively transmit or reflect light based on its polarization or wavelength. The filters obtain from this technique are used in applications such as microscopy, photography, and stage lighting………….

10. How to make Optical Filters? Doped Glass or Crystal : Some optical filters are made by doping glass or crystal materials with specific impurities or dopants. These impurities alter the optical properties of the material, allowing it to selectively absorb or transmit certain wavelengths of light. Examples, include color filters used in photography and fluorescence filters used in spectroscopy. Grating System : Gratings consist of periodic structures with alternating transparent and opaque regions. Depending on the spacing and geometry of these structures, gratings can selectively diffract or reflect certain wavelengths of light. Grating-based filters are often used in spectrometers and optical communication systems………..

11. How to make Optical Filters? Thin film Deposition mechanism Colored filters obtain by Doping process Grating system for Optical filters Mechanism of Dichroic /Interference filters

12. How are optical filters used? Microscope filters are used for both observation and photo microscopy. Each microscope filter is used for a different purpose and all are typically placed in the light path, either over the illuminator or in a filter slot that lies in the light path. Microscopy filters act to modify the light within an optical imaging system . This can be for observation purposes or for capturing high-quality images using a detector.

13. How do Optical filter work? (Main types of Optical filters)

14. How do optical filters work or use? Absorptive filters absorb certain wavelengths of light and transmit others. They are made from coloured glass or synthetic coloured gels that absorb the undesired wavelengths of light. Optical interference filters employ the interference of light waves to selectively transmit or reflect certain wavelengths of light. The filter is coated with dozens to hundreds of thin layers of material with different refractive indices. The thicknesses of the layers are carefully controlled so that the desired wavelengths of light interfere constructively and are transmitted, while undesired wavelengths interfere destructively and are reflected, or blocked. Sem -rock specializes in innovating, designing, and producing high-performance thin film optical interference filters. Use of a specific type of optical filter depends on the application. For example, a band pass filter might be used to measure only the intensity of a specific colour in an image of a living cell, while a notch filter might be used to remove unwanted noise from a medical image.

15. Types of Filters Interference-based filters : Excitation filter Barrier/ Emission filter Dichroic mirrors Wavelength-based Filters : Long pass filter Short pass filter Band pass filter

16. Interference-based Filters The 3 most common types of filters used for color selection in fluorescence microscopy are excitation filters, barrier filters and dichroic beam splitters. In modern microscopes , these are typically interference-based filters . Excitation filters permit the passage of specific wavelengths of light (excitation wavelengths) on the way towards the specimen.  Excitation filters include blue glass (BG) or ultraviolet glass (UG). Barrier/emission filters  attenuate the excitation wavelengths and permit only the selected emission wavelengths to pass towards the eye or the detector. Emission/barrier filters include yellow glass (Y or GG) or red glass (R or RG). Dichroic mirrors   are specialized filters that consist of a thin piece of coated material (often UV-grade fused silica) set at a 45° angle. This coated material is designed to efficiently reflect the excitation wavelengths and transmit the emission wavelengths with efficiencies of up to 95%.

17. Wavelength-based filters Filters can also normally only pass either short wavelengths, long wavelengths, or a band between long and short wavelengths and these are termed and defined as follows: Long pass (LP) filters   transmit wavelengths greater than a certain wavelength, described by wavelength at 50% of peak transmission. Short pass (SP) filters   transmit wavelengths below a certain wavelength. Band pass (BP) filters   transmit wavelengths of light between two different wavelengths, giving a band of transmitted wavelengths .

18. Other types of filters…… Neutral-density (ND) filters : It is used to reduce the intensity of illumination light across a broad spectrum, without modifying the range of wavelengths available. They have constant attenuation across a range of visible wavelengths, and thus specifically reduce light intensity through reflecting or absorption. ND filters are available in multiple densities and materials and can be stacked to increase optical density and increasingly attenuate light intensity. Wedge filters : T he thickness changes continuously, or in steps through the filter in the shape of a wedge. These are also known as linearly variable filters (LVF). It is used for applications such as hyper spectral sensors. Polarizing filters : These filters polarize light either linearly or circularly. This can be used for polarized light microscopy, which a label-free method to examine  bire-fringent  (double refracting) anisotropic materials. Infrared (IR or heat) filters : The filters either selectively block or transmit IR light. Many IR filters are used to prevent unwanted heating due to IR light. Illuminator lamp houses often incorporate an infrared light suppression filter. Near-infrared (NIR) imaging is powerful because tissue transmission is higher at longer wavelengths, ideal for applications such as small animal imaging. NIR filter sets are available for this type of imaging……

19. Other Types of filters Ultraviolet (UV) filters : The filters either selectively block or transmit UV light. Making filters for the UV region of the electromagnetic spectrum is difficult, but new coatings using ion beam sputter technology using newly developed coatings now offer filters for the 250–320 nm range. Didymium filters : These filters are made of didymium glass to increase the intensity and saturation of red objects. This helps to prevent the washed-out problem that some colored stains give. They are often used with histopathological staining to enhance dyes such as eosin,  fuchsin , and methylene blue. Yellow filters : These filters fine-tune the color balance of tungsten and halogen microscope light sources for color photomicrography. The yellow filter can also be helpful for metallurgical microscopy applications to identify failings in metal structures. Ground glass filters : These filters are placed over an illuminator to give a more even and diffused light. These are often used with tungsten light sources.

20. Need of filters in optical microscopy…… Microscopy filters act to modify the light within an optical imaging system. This can be for observation purposes or for capturing high-quality images using a detector.

21. Each microscopy filter can serve a different purpose and filters can be used for various improvements such as following : Increasing contrast Blocking ambient light Removing harmful UV or IR rays Selectively omitting or transmitting specific wavelengths of light (such as excitation light) Correcting light path issues Reducing the intensity of the light. Need of filters in optical microscopy

22. Applications of optical filters Optical filters are used in a wide variety of applications, including; Fluorescence microscopy :  Fluorescence allows us to distinguish different types of tissues with colors, and microscopy allows you to magnify the image so that you can see the detail that you need. Medical testing and imaging :  A wide range of optical devices are used for PCR testing (e.g. COVID-19 tests), cancer screening, DNA sequencing, wearable medical sensors, and many other purposes. Optical filters are key components that enable the correct functioning of these devices. Optical spectroscopy :  Scientists can identify the chemical composition of materials using optical spectrometers, in which optical filters isolate specific wavelengths of light for analysis. Industrial applications :  Optical filters are used in industrial applications, such as machine vision and quality control, to detect defects in products or to identify object Laser Spectrometer Laser-line Band pass filter Object Raman Long pass edge filter

23. Disadvantages Disadvantages of the two most common types of optical filters are: 1) Absorptive Filters : Poor Long-Term Temperature Resistance: Absorptive filters may not maintain their performance over extended periods under varying temperatures. Inadequate Precision: They are less precise compared to other filter types, making them less suitable for precision applications. 2)Dichroic (Interference) Filters: Higher Cost : Dichroic filters are more delicate and expensive due to their precise construction using thin film technology.

24. Conclusion Optical filters, in summary, are essential for improving the power of optical microscopy and allowing experts to precisely and precisely control light wavelengths. Filters provide a multitude of applications such as fluorescence imaging, spectrum analysis, and contrast enhancement by selectively transmitting or blocking particular light wavelengths. Several techniques, including photolithography, dichroic coating, and thin film deposition, are used to create optical filters; each has unique benefits and uses. The variety of filter types- such as polarizing and infrared filters, interference filters, and absorptive filters- emphasizes how adaptable they are to meeting various microscopy needs and difficulties. Dichroic filters may be more expensive because of their complex construction, whilst absorptive filters might have limits with regard to precision and long-term temperature resistance. However, both kinds provide substantial contributions to the advancement of scientific inquiry, healthcare diagnosis, industrial quality assurance, and other domains that depend on optical imaging technology. Further advancements in microscopy performance are anticipated as technology develops, thanks to the creativity and enhancement of optical filters, which will allow for increased accuracy, effectiveness, and adaptability in a variety of applications. Researchers and practitioners can fully utilize optical filters to unlock new insights and discoveries in a variety of scientific and industrial sectors by knowing their principles and capabilities.