Digital Microscope Wikipedia

[Roselee Kruppa]

Adigital microscope is a variation of a traditional optical microscope that uses optics and a digital camera to output an image to a monitor, sometimes by means of software running on a computer. A digital microscope often has its own in-built LED light source, and differs from an optical microscope in that there is no provision to observe the sample directly through an eyepiece. Since the image is focused on the digital circuit, the entire system is designed for the monitor image. The optics for the human eye are omitted.

Digital microscopes range from, usually inexpensive, USB digital microscopes to advanced industrial digital microscopes costing tens of thousands of dollars. The low price commercial microscopes normally omit the optics for illumination (for example Khler illumination and phase contrast illumination) and are more akin to webcams with a macro lens. An optical microscope can also be fitted with a digital camera.

An early digital microscope was made by a company in Tokyo, Japan in 1986, which is now known as Hirox Co. LTD.[1] It included a control box and a lens connected to a computer. The original connection to the computer was analog through an S-video connection. Over time that connection was changed to FireWire 800 to handle a large amount of digital information coming from the digital camera. Around 2005 they introduced advanced all-in-one units that did not require a computer, but had the monitor and computer built-in. Then in late 2015 they released a system that once again had the computer separate, but connected to the computer by USB 3.0, taking advantage of the speed and longevity of the USB connection. This system also was much more compacted than previous models with a reduction in the number of cables and physical size of the unit itself.

The invention of the USB port resulted in a multitude of USB microscopes ranging in quality and magnification. They continue to fall in price, especially compared with traditional optical microscopes. They offer high-resolution images which are normally recorded directly to a computer, and which also use the computer power for their built-in LED light source. The resolution is directly related to the number of megapixels available on a specific model, from 1.3 MP, 2 MP, 5 MP and upwards.

Since the digital microscope has the image projected directly on to the CCD camera, it is possible to have higher quality recorded images than with a stereo microscope. With the stereo microscope, the lenses are made for the optics of the eye. Attaching a CCD camera to a stereo microscope will result in an image that has compromises made for the eyepiece. Although the monitor image and recorded image may be of higher quality with the digital microscope, the application of the microscope may dictate which microscope is preferred.[citation needed]

Digital eyepiece for microscopes Software contain wide ranges of optional accessories provides multipurpose such as phase contrast observation, Bright and dark field observation, microphotography, image processing, particle size determination in μm, pathological report and patient manager, microphotograph, recording mobility video, drawing and labeling etc.

With a typical 2 megapixel CCD, a 16001200 pixels image is generated. The resolution of the image depends on the field of view of the lens used with the camera. The approximate pixel resolution can be determined by dividing the horizontal field of view (FOV) by 1600.

Increased resolution can be accomplished by creating a sub-pixel image. The Pixel Shift Method uses an actuator to physically move the CCD in order to take multiple overlapping images. By combining the images within the microscope, sub-pixel resolution can be generated. This method provides sub-pixel information, averaging a standard image is also a proven method to provide sub-pixel information.

Most of the high-end digital microscope systems have the ability to measure samples in 2D. The measurements are done onscreen by measuring the distance from pixel to pixel. This allows for length, width, diagonal, and circle measurements as well as much more. Some systems are even capable of counting particles.

3D measurement is achieved with a digital microscope by image stacking. Using a step motor, the system takes images from the lowest focal plane in the field of view to the highest focal plane. Then it reconstructs these images into a 3D model based on contrast to give a 3D color image of the sample. From these 3D model measurements can be made, but their accuracy is based on the step motor and depth of field of the lens.

2D and 3D tiling, also known as stitching or creating a panoramic, can now be done with the more advanced digital microscope systems. In 2D tiling the image is automatically tiled together seamlessly in real-time by moving the XY stage. 3D tiling combines the XY stage movement of 2D tiling with the Z-axis movement of 3D measurement to create a 3D panoramic.

Digital microscopes range from inexpensive units costing from perhaps US$20, which connect to a computer via USB connector, to units costing tens of thousands of dollars. These advanced digital microscope systems usually are self-contained and do not require a computer. [citation needed]

An electron microscope is a microscope that uses a beam of electrons as a source of illumination. They use electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing them to produce magnified images or electron diffraction patterns. As the wavelength of an electron can be up to 100,000 times smaller than that of visible light, electron microscopes have a much higher resolution of about 0.1 nm, which compares to about 200 nm for light microscopes.[1] Electron microscope may refer to:

Many developments laid the groundwork of the electron optics used in microscopes.[2] One significant step was the work of Hertz in 1883[3] who made a cathode-ray tube with electrostatic and magnetic deflection, demonstrating manipulation of the direction of an electron beam. Others were focusing of the electrons by an axial magnetic field by Emil Wiechert in 1899,[4] improved oxide-coated cathodes which produced more electrons by Arthur Wehnelt in 1905[5] and the development of the electromagnetic lens in 1926 by Hans Busch.[6] According to Dennis Gabor, the physicist Le Szilrd tried in 1928 to convince him to build an electron microscope, for which Szilrd had filed a patent.[7]

To this day the issue of who invented the transmission electron microscope is controversial.[8][9][10][11] In 1928, at the Technical University of Berlin, Adolf Matthias (Professor of High Voltage Technology and Electrical Installations) appointed Max Knoll to lead a team of researchers to advance research on electron beams and cathode-ray oscilloscopes. The team consisted of several PhD students including Ernst Ruska. In 1931, Max Knoll and Ernst Ruska[12][13] successfully generated magnified images of mesh grids placed over an anode aperture. The device, a replicate of which is shown in the figure, used two magnetic lenses to achieve higher magnifications, the first electron microscope. (Max Knoll died in 1969, so did not receive a share of the 1986 Nobel prize for the invention of electron microscopes.)

Apparently independent of this effort was work at Siemens-Schuckert by Reinhold Rdenberg. According to patent law (U.S. Patent No. 2058914[14] and 2070318,[15] both filed in 1932), he is the inventor of the electron microscope, but it is not clear when he had a working instrument. He stated in a very brief article in 1932[16] that Siemens had been working on this for some years before the patents were filed in 1932, claiming that his effort was parallel to the university development. He died in 1961, so similar to Max Knoll, was not eligible for a share of the 1986 Nobel prize.[17]

In the following year, 1933, Ruska and Knoll built the first electron microscope that exceeded the resolution of an optical (light) microscope.[18] Four years later, in 1937, Siemens financed the work of Ernst Ruska and Bodo von Borries, and employed Helmut Ruska, Ernst's brother, to develop applications for the microscope, especially with biological specimens.[18][19] Also in 1937, Manfred von Ardenne pioneered the scanning electron microscope.[20] Siemens produced the first commercial electron microscope in 1938.[21] The first North American electron microscopes were constructed in the 1930s, at the Washington State University by Anderson and Fitzsimmons [22] and at the University of Toronto by Eli Franklin Burton and students Cecil Hall, James Hillier, and Albert Prebus. Siemens produced a transmission electron microscope (TEM) in 1939.[23] Although current transmission electron microscopes are capable of two million times magnification, as scientific instruments they remain similar but with improved optics.

In the 1940s, high-resolution electron microscopes were developed, enabling greater magnification and resolution.[24] By 1965, Albert Crewe at the University of Chicago introduced the scanning transmission electron microscope using a field emission source,[25] enabling scanning microscopes at high resolution.[26] By the early 1980s improvements in mechanical stability as well as the use of higher accelerating voltages enabled imaging of materials at the atomic scale.[27][28] In the 1980s, the field emission gun became common for electron microscopes, improving the image quality due to the additional coherence and lower chromatic aberrations. The 2000s were marked by advancements in aberration-corrected electron microscopy, allowing for significant improvements in resolution and clarity of images.[29][30]

The original form of the electron microscope, the transmission electron microscope (TEM), uses a high voltage electron beam to illuminate the specimen and create an image. An electron beam is produced by an electron gun, with the electrons typically having energies in the range 20 to 400 keV, focused by electromagnetic lenses, and transmitted through the specimen. When it emerges from the specimen, the electron beam carries information about the structure of the specimen that is magnified by lenses of the microscope. The spatial variation in this information (the "image") may be viewed by projecting the magnified electron image onto a detector. For example, the image may be viewed directly by an operator using a fluorescent viewing screen coated with a phosphor or scintillator material such as zinc sulfide. A high-resolution phosphor may also be coupled by means of a lens optical system or a fibre optic light-guide to the sensor of a digital camera. Direct electron detectors have no scintillator and are directly exposed to the electron beam, which addresses some of the limitations of scintillator-coupled cameras.[31]

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