Microscope Glossary
Learn more about digital microscope technology using the detailed feature pages below.
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3D Display Function
A major advantage of digital microscopes over optical microscopes is their ability to easily create 3D images. The 3 dimensional profiles of observation targets are often unclear when using only 2 dimensional images. The ability to create 3 dimensional images from a "stack" of 2 dimensional images in the Z-axis is one of the most important functions of digital microscopes.
Atomic Force Microscopes (AFM)
A type of scanning probe microscope that measures and images a target by moving a mechanical probe across the surface. These systems are capable of providing high-resolution data at the sub-nanometer level.
CCD and Actuator
Digital Microscopes and Video Microscopes are equipped with either a CCD or CMOS sensor as their imaging element. Some high-end systems boast resolutions as high as 54 megapixels and can even operate in handheld mode. The newly-introduced, ultra-high definition handheld camera from KEYENCE incorporates built-in actuators attached to the CCD and features a 3CCD and pixel-shift imaging mode.
Compound Microscopes
Microscopes that make use of multiple lenses for collecting reflected/transmitted light from a sample and then focusing that light onto a receiving element (generally ones' eyes or a camera) are known as compound microscopes. These systems can be configured to be upright, with the objective lens pointing downward, or inverted, with the objective lens pointing upward. The advantages of such configurations are generally dependent on the type of applications for which the microscopes are intended to be used. Compared to a simple microscope (containing only a single lens element), compound microscopes tend to be larger, more costly and more complicated in their operation. The inclusion of multiple lens structures in a compound microscope helps to reduce the amount of chromatic aberration (color shifting) and improve the resolution of the image.
Though widely used, conventional compound light microscopes generally suffer from several limitations - short working distance, shallow depth-of-field, inability to view large objects, etc. - making them less versatile and portable than digital microscopes (or video microscopes).
Data Storage/Recording
Most microscope systems require a separate PC for storing image files. The VHX-1000 is equipped with a built-in hard drive, CD-R/RW drive, ethernet port, and multiple USB ports, providing several ways for a user to catalog images and data.
Depth of field
A microscope produces the clearest image when the observed object is placed at the focal position of the lens. The acceptable range of a focused image when the object moves near to or away from the focal position is called the depth of field. Even for an uneven target, a lens with a large depth of field allows an observer to view the entire object in focus.
DFD (Depth from Defocus)
The D.F.D. method is the process by which the VHX can (1) Compile a completely in-focus image, or (2) Generate data to compile a 3D model. The D.F.D. method analyzes the level of contrast, or focus at each level of the target. By using the degree of blurring, the D.F.D. method can calculate height information for each pixel, thereby enabling the compilation of a 3D model or a completely in-focus image. This method works best when the target is unable to be completely focused throughout the entire topography.
Differential Interference Contrast (DIC)
Differential interference contrast is an illumination technique in which minute differences in the height of a sample are made discernible through the inteference of light waves. This method allows for even the most transparent of samples to be observed in great detail. It is suited for observing small flaws and steps on the surface of the sample.
Digital Microscopes
All-in-one microscope systems that integrate an LCD monitor, PC, camera, optics, light source, and software into a portable, standalone observation device. There are generally two types of digital microscopes: low-cost, USB systems and all-in-one, research grade systems. USB-style microscopes are generally only used for low magnification observation and image capture, while all-in-one, research digital microscopes are capable of performing all aspects of the inspection and analysis process (image, measure, document, capture). Research-grade digital microscopes also provide much higher magnification and resolution and are capable of providing a wider range of imaging capabilities.
Field of View
The field of view is the observable range of a target that can be seen through an eye-piece or on a monitor. Field of view can be specified angularly (70 degree field of view) or linearly (1 inch field of view). As the magnification increases, the field of view decreases.
Flourescence
In optical microscopy, the emission of visible light from an object after being stimulated by incident radiation. The object will generally continue to fluoresce as long as the stimulant is applied. While some objects or specimens can fluoresce naturally (autofluorescence), most will need to be dyed with a fluorophore.
Flourescent Confocal Microscopes
Usually laser-based, these microscopes are designed to provide high-resolution images without interference from out-of-focus portions of the sample. They can also view deeper into a specimen when compared to conventional epiflourescence microscopes. However, this equipment is generally quite costly and difficult to operate, requiring lots of training and use to become proficient.
Fluorescence Microscopes
Also known as wide-field fluorescence or epifluorescence microscopes, these systems are designed for imaging targets that react to certain wavelengths of light. This microscope generally use a high-pressure mercury or xenon lamp as the light source , an excitation and absorption filter, and dichroic mirror for providing the appropriate wavelength of light to be emitted and received. The incident radiation used to induce fluorescence is always at a higher wavelength than the emission wavelength of the object/specimen.
Halation
Halation, commonly referred to as glare, is the result of light reflecting off of a highly reflective surface (such as metal or glass). These glare spots may interfere with sample observation. The VHX Series employs several methods to reduce glare; from lighting adapters to glare removing algorithms.
HDR (High Dynamic Range)
HDR is a common photography function by which multiple images are captured at different brightness levels (achieved by fluctuating the shutter speed). The data from these images can then compiled to increase the levels of color/grey-scale gradation from the traditional 8 bit 256 levels to a 16 bit color resolution representing 65,536 levels of gradation. With increased levels of color gradation, more subtle contrast and color changes in a sample can be observed, while eliminating over/under exposed areas.
High-Speed Recording
When attempting to monitor processes that occur faster than the human eye can detect or a conventional camera can record, high-speed imaging is a must. High-speed cameras can record at very high frame rates, allowing users to view the video in slow motion. These systems usually require a camera, external lighting units and a PC, and are usually designed for macro observation. The VW-9000 High-speed Camera from KEYENCE integrates all of the necessary pieces of equipment into a single device and can record at up to 230,000 frames per second.
High-speed Video Microscopes
These fully-integrated microscopes combine a high-speed camera, LCD monitor, light source, optical lens and software. The integration of these components allows for a much easier and shorter setup time and require little training to operate. Users can record high-speed video of processes at both the macro and micro levels and capture images like that of a digital microscope. Software for analyzing movements, such as distance, velocity and acceleration, also accompany these devices.
Hi-magnification System
Separate stand and stage assembly for use with high-magnification lenses. These are designed to withstand a higher degree of vibration and include a mechanism for holding the camera cable in place. The lens holder can be removed from the stand to allow for custom mounting of the lens, so that any sample can be accommodated.
Laser Scanning Microscopes
Incorporates the functionality of three separate pieces of equipment - optical microscope, SEM, surface roughness gauge - with the ease-of-use of a conventional optical microscope. These systems operate by generating an optical image with color data, and then combining that with an image generated from a laser that has scanned across a sample surface in XYZ dimensions. The result is a high-resolution, large depth-of-field, color image with nanometer height resolution for accurate profiles and roughness measurements.
Lens/Fiberscopes
Some of the most important parts of any digital microscope system are the lenses that are used with the microscope. KEYENCE offers some of the best lenses, that when used with the KEYENCE VHX-1000, produce the best images obtainable with digital microscopes.
Metallurgical Microscope
A specialized microscope designed for looking at cross-sections of metal targets (metallurgical mounts). Typically inverted, these microscopes employ high-resolution objective lenses with very short working distances. While these systems work well for this type of analysis, they are very limited in their range of applications.
Moving Target Analysis
The VW-9000 automatically tracks moving objects in recorded footage to quantify speed, distance, angle, and other measurements. This lets you analyze not only how a target is moving, but how far a target is moving.
Networking
Fully-integrated digital microscopes that employ built-in PC components are able to transfer images, video and data to other computers via an ethernet port. Systems can typically be connected to a LAN or an FTP server for saving or retrieving files. This is in addition to saving or transferring files to a hard disk drive, USB or CD. The VHX-1000 features a 160 gigabyte hard drive (users can save up to approximately 500,000 JPEG files), eight USB ports, CD burner and 100-baseTX LAN port.
Numerical Aperture
The numerical aperture is the most important element that determines the performance of the objective lens. The numerical aperture is called N.A. and it is usually marked on the side of the objective lens such as “NA 0.6.” The dry objective lens has an N.A. between 0.05 and 0.95, while an oil immersion objective lens generally has an N.A. between 0.65 and 1.4. As this value increases, the resolution of the observed image becomes higher.
N.A. = n x sinθ
n : The refractive index of the medium between the target and the objective lens.
(Air : n = 1, Oil : n = 1.515)
On-screen Measurement
Digital microscopes use a vast array of easy-to-use measurement functions to produce highly-accurate image inspections. All measurements can be quickly calculated simply with a click of the mouse, and then saved directly on the image or as a CSV file.
Parfocal
When operating a VHX Zoom lens, once the image is in focus at the highest magnification, the image will remain in complete focus at each subsequent lower magnification. This maintenance of focus throughout the entire range of magnification is known as parfocality.
Pixel Shifting Camera
Pixel shift is the mechanism by which a CCD is physically shifted, creating sub pixels or increased pixel resolution. The VHX CCD contains 2.11 million pixels, alone. Attached to the VHX CCD are piezo crystal actuators that when supplied with a voltage will expand and physically shift the CCD. When the CCD is shifted in a 3x3 array, 9 sub pixels are generated, increasing the pixel resolution of the image. The new pixel resolution has been increased from 2.11 MP to 18 MP.
Profile Measurement
The VHX-1000 can create a 3D image by capturing photos taken at different height intervals. Users can measure height and width by dragging a profile line across the 3D model and analying the resultant profile graph. Since, the profile graph is related to the position of the cursor on the image, it is easy to determine the current point being measured.
Quick Depth Composition
Another advantage of digital microscopes is their ability to capture images that are entirely in-focus. With the KEYENCE VHX-1000, a series of images from different focal depths can be combined, in real-time, to form a single image with overall focus. Used in conjunction with a motorized lens arm, the Depth Composition function can be operated without any physical adjustments from the user.
SEM
A type of electron microscope that scans the surface of a sample using a beam of electrons. These systems are characterized with producing high-resolution images with a large depth-of-field and capable of reaching extremely high magnifications. SEMs can be outfitted with an optional elemental analyzer for determining the chemical makeup of a target.
Split Screen Image Comparison
A standard feature on most high end digital microscopes is the ability to display independently captured images on a monitor screen split horizontally, vertically or into four parts. This function enables easy comparative inspection between acceptable and unacceptable products or comparative observation of overall and magnified images.
Stereoscopic Microscope
Probably the most general form of an optical microscope. These systems generally provide a user with a lower magnification range than compound microscopes and have longer working distances for imaging larger, three-dimensional targets. Stereomicroscopes have two eyepieces to allow for 3D observation and are useful when performing assembly or re-work.
Telecentric
Telecentricity is a characteristic of certain multi-element lenses and is defined by its ability to keep the chief rays parallel to the optical axis in either object and/or image space. KEYENCE's RZ (Real Zoom) Lenses are designed to be highly telecentric throughout most of their magnification ranges, making measurements much more accurate, even when the sample being measured is around the periphery. Telecentric lenses are also useful when constructing 3D images and when stacking multiple out-of-focus areas into a single, in-focus image.
Variable-angle Observation System
Stand and stage system that allows a user to tilt the camera and lens around a sample (up to 90 degrees) while also rotating 360 degrees about the object. More capable units provide for an on-axis tilt, keeping the object in the center of the field-of-view while tilting about it. Adjustable lens and stage height accommodates larger samples not suitable for conventional microscopes.
Working distance
The distance between the lowest portion of the lens and the focal position on a sample. A larger working distance allows for easier inspection and manipulation of the object being observed.
Zoom Lens
A zoom lens is a lens that allows for a range of selectable magnifications within one lens. VHX lenses typically contain about 6 different magnification options per lens. The ranges might represent 20-200X magnification, or 100-1000X magnification (as in the VH-Z20R and VH-Z100R lenses, respectively). The VHX zoom lenses have detents for each individual magnification, ensuring the correct selection of the desired magnification.
