Infrared microscope
Fourier transform micro-infrared (FT-MIR) spectroscopy has evolved very rapidly, and infrared microscopes have been updated several times in the space of a few years. Now the use of infrared microscope users more and more, micro-infrared spectroscopy technology is increasingly welcomed by the majority of users.
Fourier transform micro-infrared (FT-MIR) spectroscopy has evolved very rapidly, and infrared microscopes have been updated several times in the space of a few years. Now the use of infrared microscope users more and more, micro-infrared spectroscopy technology is increasingly welcomed by the majority of users.
Any solid sample can be tested by the micro-infrared method, and liquid samples are also very convenient to be tested by the micro-infrared method. There is no need to add any diluent when testing samples using the micro-infrared method, so there is no diluent effect. That is to say, the spectrum measured by the micro-infrared method can fully reflect the nature of the sample spectrum, which is not subject to the image of the diluent like the solution spectrum or the spectrum measured by the halide pressure film method.
Infrared microscopy tests are highly sensitive. The effective spot diameter of the main optical bench transmitting infrared is about 10 mm. After the infrared beam of the infrared microscope is focused by the infrared objective lens, the effective infrared spot diameter of the irradiation on the sample is 100~200μm, and the energy of the infrared light in the middle of the infrared spot is the highest. In the tiny interval, the luminous flux is large, so the spectrum of trace samples can be tested. The amount of sample can be as small as nanograms, and high-quality spectra can be obtained for a few nanograms of sample with micro-infrared testing. Therefore, micro-infrared has been widely used in the fields of chemistry, biology, medicine, material science, mineralogy, court science, and so on.
Types, principles, and structures of infrared microscopes
Infrared microscopes are being updated rapidly, and many manufacturers of infrared instruments around the world now offer different grades of infrared microscopes. The infrared microscope has developed from a non-coaxial optical system microscope to a coaxial optical microscope, that is, the infrared light path and visible light path coaxial. Some infrared instrument companies utilize the dichroic TruView technology, which allows the observation of the measured interval during data collection, and there is no need to switch between observation and data collection. Currently, in addition to the ordinary infrared microscope, the emergence of a Mapping microscope, that is, an automatic point-by-point scanning imaging microscope. In addition, there is also a more advanced Imaging microscope, that is, automatic surface scanning or line scanning imaging microscope.
Surface scanning imaging microscope linked to the Fourier transform infrared spectrometer requires a step scanning function, while the line scanning imaging microscope does not require an infrared spectrometer with this function, scanning the same area of the sample imaging infrared spectroscopy, line scanning imaging microscope as the surface scanning imaging microscope to use some of a long time, but then the point-by-point scanning imaging microscope used to greatly reduce the time.
An ordinary infrared microscope can only test one spectrum at a time. Mapping microscopes can be formed by installing hardware for automatic point-by-point scanning imaging and software for controlling the hardware on top of a high-grade microscope.
Conventional IR microscopes are mounted on the left or right side of the main IR optical bench as an accessory to the main IR optical bench. The infrared light path is redirected from the optical bench to the left or right side of the infrared microscope by a mirror shuttle in the optical bench.
The construction and optical path systems of infrared microscopes sold by different infrared instrument companies are different, and the construction and optical path systems of different models of infrared microscopes from the same infrared instrument company are also different. However, no matter which model of the infrared microscope, its basic structure is largely the same. Mainly consists of an incandescent light source, optical filters, diaphragm, infrared objective lens, concentrator, glass eyepiece and camera system, sample stage, optical path compensator and detector, and other components.
1.1.1 Incandescent light source
Infrared microscopes usually have two incandescent light sources. The incandescent light sources provide visible illumination, allowing the sample to be examined on the sample stage to be seen clearly through an eyepiece or camera system. The upper incandescent lamp is used when testing transmission and reflection micro-infrared spectroscopy, and the lower incandescent lamp is used when testing transmission micro-infrared spectroscopy.
1.1.2 Optical filters
Two filters of different colors are usually mounted on an infrared microscope. Their function is to turn the white light emitted from an incandescent lamp into a different color of light after passing through the optical filters. The upper and lower two optical filters are not the same color, shining on the sample has a different color, to distinguish between the upper and lower light source, conducive to the focusing of the sample to be measured.
1.1.3 Diaphragm
The function of the diaphragm is to produce an infrared spot. The size of the infrared spot illuminating the sample to be measured is controlled by the diaphragm. When the aperture of the diaphragm is certain, samples falling within the IR spot contribute to the IR spectrum, and samples outside the IR spot do not affect the spectrum.
1.1.4 Infrared Objective Lenses and Concentrators
The infrared objective lens is mounted on the mirror changer carousel, which is between the diaphragm and the sample stage, and the condenser is mounted between the sample stage and the lower diaphragm.
The magnification of the infrared objective lens is usually divided into three types: 10×, 15×, and 32×. The infrared objective lens both focuses the beam passing through the diaphragm on the sample to be measured and magnifies the image of the sample through the infrared objective and eyepiece. Another function of the infrared objective is that when testing micro-infrared reflectance spectroscopy in reflectance mode, the infrared objective collects the reflected and partially scattered light gathers the collected light, and directs it toward the detector. The function of the concentrator is to bring together the divergent beams of light after passing through the sample and direct them toward the detector. The concentrator is only used when testing transmission spectra and is not used when testing reflectance spectra.
1.1.5 Glass eyepieces and camera systems
Images of the samples on the sample stage can be viewed by eye through an eyepiece or through a camera system that transmits images of the samples to a computer and monitors. Some infrared microscopes do not have an eyepiece, only a camera system.
Monocular eyepieces are used for videotaping and cannot be viewed with the eye, only the image of the sample can be viewed through the monitor. Now although there are high-performance, high-resolution color CCD camera systems, the monitor is always less clear than with the naked eye observation, because the resolution of the monitor is not as high as the resolution of the retina of the eye, the monitor is not as clear as the eyes to distinguish the color. However, images of the samples taken by the camera can be stored in a computer, drawn, copied, or pasted into a document, providing clear photographs for printing test reports.
1.1.6 Sample table and window sheet materials
The sample stage of an infrared microscope is also known as the carrier stage. The sample to be tested is placed on the sample stage of the infrared microscope and the position of the sample can be adjusted in X, Y, and Z directions. An ordinary infrared microscope requires manual adjustment of the knob to change the position of the sample to focus the sample. In some infrared microscopes, the change of sample position can be realized by the computer-controlled electric motor driving the sample stage to achieve the purpose of automatic focusing.
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