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A digital 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 Köhler 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.
A primary difference between a stereo microscope and a digital microscope is the magnification. With a stereo microscope, the magnification is determined by multiplying the eyepiece magnification times the objective magnification. Since the digital microscope does not have an eyepiece, the magnification cannot be found using this method. Instead the magnification for a digital microscope was originally determined by how many times larger the sample was reproduced on a 15” monitor. While monitor sizes have changed, the physical size of the camera chip used has not. As a result, magnification numbers and field of view are still the same as that original definition, regardless of the size of the monitor used. The average difference in magnification between an optical microscope and a digital microscope is about 40%. Thus the magnification number of a stereomicroscope is usually 40% less than the magnification number of a digital microscope.[ citation needed ]
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 1600×1200 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 ]
Some of the cheaper microscopes which connect via USB have no stand, or a simple stand with clampable joints. They are essentially very simple webcams with small lenses and sensors—and can be used to view subjects which are not very close to the lens— mechanically arranged to allow focus at very close distances. Magnification is typically claimed to be user-adjustable from 10× to 200-400×.[ citation needed ]
Devices which connect to a computer require software to operate. The basic operation includes viewing the microscope image and recording "snapshots". More advanced functionality, possible even with simpler devices, includes recording moving images, time-lapse photography, measurement, image enhancement, annotation, etc. Many of the simpler units which connect to a computer use standard operating system facilities, and do not require device-specific drivers. A consequence of this is that many different microscope software packages can be used interchangeably with different microscopes, although such software may not support features unique to the more advanced devices. Basic operation may be possible with software included as part of computer operating systems —in Windows XP, images from microscopes which do not require special drivers can be viewed and recorded from "Scanners and Cameras" in Control Panel.[ citation needed ]
The more advanced digital microscope units have stands that hold the microscope and allow it to be racked up and down, similarly to standard optical microscopes. Calibrated movement in all three dimensions are available through the use of a step motor and automated stage. The resolution, image quality, and dynamic range vary with price. Systems with a lower number of pixels have a higher frame rate (30fps to 100fps) and faster processing. The faster processing can be seen when using functions like HDR (high dynamic range). In addition to general-purpose microscopes, instruments specialized for specific applications are produced. These units can have a magnification range up to 0–10,000x, are either all-in-one systems (computer built-in) or connect to a desktop computer. They also differ from the cheaper USB microscopes in not only the quality of the image, but also in capability, and the quality of the system's construction giving these types of systems a longer lifetime.[ citation needed ]
Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye. There are three well-known branches of microscopy: optical, electron, and scanning probe microscopy, along with the emerging field of X-ray microscopy.
A microscope is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisible to the eye unless aided by a microscope.
A digital camera, also called a digicam, is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile devices like smartphones with the same or more capabilities and features of dedicated cameras. High-end, high-definition dedicated cameras are still commonly used by professionals and those who desire to take higher-quality photographs.
In optics, chromatic aberration (CA), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point. It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light. The refractive index of most transparent materials decreases with increasing wavelength. Since the focal length of a lens depends on the refractive index, this variation in refractive index affects focusing. Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image.
The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects. Optical microscopes are the oldest design of microscope and were possibly invented in their present compound form in the 17th century. Basic optical microscopes can be very simple, although many complex designs aim to improve resolution and sample contrast.
An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electronic image sensors.
Microscope image processing is a broad term that covers the use of digital image processing techniques to process, analyze and present images obtained from a microscope. Such processing is now commonplace in a number of diverse fields such as medicine, biological research, cancer research, drug testing, metallurgy, etc. A number of manufacturers of microscopes now specifically design in features that allow the microscopes to interface to an image processing system.
An image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting or an object and converts it to a digital image. Commonly used in offices are variations of the desktop flatbed scanner where the document is placed on a glass window for scanning. Hand-held scanners, where the device is moved by hand, have evolved from text scanning "wands" to 3D scanners used for industrial design, reverse engineering, test and measurement, orthotics, gaming and other applications. Mechanically driven scanners that move the document are typically used for large-format documents, where a flatbed design would be impractical.
Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a size ratio called optical magnification. When this number is less than one, it refers to a reduction in size, sometimes called de-magnification.
A light field camera, also known as a plenoptic camera, is a camera that captures information about the light field emanating from a scene; that is, the intensity of light in a scene, and also the precise direction that the light rays are traveling in space. This contrasts with conventional cameras, which record only light intensity at various wavelengths.
Digital photography uses cameras containing arrays of electronic photodetectors interfaced to an analog-to-digital converter (ADC) to produce images focused by a lens, as opposed to an exposure on photographic film. The digitized image is stored as a computer file ready for further digital processing, viewing, electronic publishing, or digital printing. It is a form of digital imaging based on gathering visible light.
The optical transfer function (OTF) of an optical system such as a camera, microscope, human eye, or projector specifies how different spatial frequencies are captured or transmitted. It is used by optical engineers to describe how the optics project light from the object or scene onto a photographic film, detector array, retina, screen, or simply the next item in the optical transmission chain. A variant, the modulation transfer function (MTF), neglects phase effects, but is equivalent to the OTF in many situations.
The following are common definitions related to the machine vision field.
A structured-light 3D scanner is a 3D scanning device for measuring the three-dimensional shape of an object using projected light patterns and a camera system.
The stereo, stereoscopic or dissecting microscope is an optical microscope variant designed for low magnification observation of a sample, typically using light reflected from the surface of an object rather than transmitted through it. The instrument uses two separate optical paths with two objectives and eyepieces to provide slightly different viewing angles to the left and right eyes. This arrangement produces a three-dimensional visualization of the sample being examined. Stereomicroscopy overlaps macrophotography for recording and examining solid samples with complex surface topography, where a three-dimensional view is needed for analyzing the detail.
A time-of-flight camera, also known as time-of-flight sensor, is a range imaging camera system for measuring distances between the camera and the subject for each point of the image based on time-of-flight, the round trip time of an artificial light signal, as provided by a laser or an LED. Laser-based time-of-flight cameras are part of a broader class of scannerless LIDAR, in which the entire scene is captured with each laser pulse, as opposed to point-by-point with a laser beam such as in scanning LIDAR systems. Time-of-flight camera products for civil applications began to emerge around 2000, as the semiconductor processes allowed the production of components fast enough for such devices. The systems cover ranges of a few centimeters up to several kilometers.
Hirox (ハイロックス) is a lens company in Tokyo, Japan that created the first digital microscope in 1985. This company is now known as Hirox Co Ltd. Hirox's main industry is digital microscopes, but still makes the lenses for a variety of items including rangefinders.
A USB microscope is a low-powered digital microscope which connects to a computer's USB port. Microscopes essentially the same as USB models are also available with other interfaces either in addition to or instead of USB, such as via WiFi. They are widely available at low cost for use at home or in commerce. Their cost varies in the range of tens to thousands of dollars. In essence, a USB microscope is a webcam with a high-powered macro lens, and generally uses reflected rather than transmitted light, using built-in LED light sources surrounding the lens. The camera is usually sensitive enough not to need additional illumination beyond normal ambient lighting. The camera attaches directly to the USB port of a computer without the need for an eyepiece, and the images are shown directly on the computer's display.
Digital holographic microscopy (DHM) is digital holography applied to microscopy. Digital holographic microscopy distinguishes itself from other microscopy methods by not recording the projected image of the object. Instead, the light wave front information originating from the object is digitally recorded as a hologram, from which a computer calculates the object image by using a numerical reconstruction algorithm. The image forming lens in traditional microscopy is thus replaced by a computer algorithm. Other closely related microscopy methods to digital holographic microscopy are interferometric microscopy, optical coherence tomography and diffraction phase microscopy. Common to all methods is the use of a reference wave front to obtain amplitude (intensity) and phase information. The information is recorded on a digital image sensor or by a photodetector from which an image of the object is created (reconstructed) by a computer. In traditional microscopy, which do not use a reference wave front, only intensity information is recorded and essential information about the object is lost.
As described here, white light interferometry is a non-contact optical method for surface height measurement on 3D structures with surface profiles varying between tens of nanometers and a few centimeters. It is often used as an alternative name for coherence scanning interferometry in the context of areal surface topography instrumentation that relies on spectrally-broadband, visible-wavelength light.