Digital microscope
Encyclopedia
A digital microscope is a variation of a traditional optical microscope that uses optics
and a charge-coupled device
(CCD) camera to output a digital image to a monitor
, sometimes by means of software running on a computer
. A digital microscope differs from an optical microscope
in that there is no provision to observe the sample directly through an eyepiece
. Since the optical image is projected directly on the CCD camera, the entire system is designed for the monitor image. The optics for the human eye are omitted.
Digital microscope is the term commonly used for low price commercial microscopes designed for use with a computer. Although the term can also be used for advanced systems that do not require a separate computer and can cost 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 webcam
s with a macro lens. For information about optical microscopes with a digital camera in research and development see optical microscope
.
, Japan
in 1986, which is now known as Hirox
Co Ltd. 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 the large amount of digital information coming from the digital camera. But some of their current advanced versions are all-in-one and do not require a computer. Other versions of digital microscopes were later developed by Keyence
Corp and Leica Microsystems
. Invention of the USB port resulted in a multitude of USB microscope
s ranging in quality and magnification. They continue to fall in price, especially compared with conventional optical microscope
s.
. With an optical microscope the magnification is found by multiplying the lens magnification by the eyepiece 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 is found by how many times larger the sample is reproduced on the monitor. Therefore the magnification will depend on the size of the monitor. The average digital microscope system has a 15" monitor, would result in an average difference in magnification between an optical microscope and a digital microscope of about 60%. Thus the magnification number of an optical microscope is usually 60% larger than the magnification number of a digital microscope.
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 an optical microscope. With the optical microscope, the lenses are made for the optics of the eye. Attaching a CCD camera to an optical microscope will result in a 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 for the microscope may dictate which microscope is preferred.
(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 cheaper microscopes which connect via USB have no stand, or a simple stand with clampable joint
s. They are essentially very simple webcam
s 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×.
Devices which connect to a computer require software to operate. 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 system
s—in Windows XP
, images from microscopes which do not require special drivers can be viewed and recorded from "Scanners and Cameras" in Control Panel.
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 may be available. Resolution, image quality, and dynamic range vary with price. True spatial resolution may be increased by pixel shifting
technology. Better units have larger sensors; the sensor may be cooled to reduce optical noise
. Systems with a lower number of megapixels have a higher frame rate (30fps) and faster processing. The faster processing can be seen when using functions like HDR (high dynamic range
). In addition to general-purpose microscopes, instruments specialised for specific applications are produced. These units can have a magnification range up to 0-7000x, are usually all-in-one (don't require a computer), and can be portable. They also differ from the cheaper USB microscopes in not only the quality of the image but the quality of the system's construction giving these types of systems a longer lifetime.
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
and a charge-coupled device
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
(CCD) camera to output a digital image to a monitor
Video monitor
A video monitor also called a broadcast monitor, broadcast reference monitor or just reference monitor, is a display device similar to a television set, used to monitor the output of a video-generating device, such as playout from a video server, IRD, video camera, VCR, or DVD player. It may or...
, sometimes by means of software running on a computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
. A digital microscope differs from an optical microscope
Optical microscope
The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the...
in that there is no provision to observe the sample directly through an eyepiece
Eyepiece
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings...
. Since the optical image is projected directly on the CCD camera, the entire system is designed for the monitor image. The optics for the human eye are omitted.
Digital microscope is the term commonly used for low price commercial microscopes designed for use with a computer. Although the term can also be used for advanced systems that do not require a separate computer and can cost tens of thousands of dollars. The low price commercial microscopes normally omit the optics for illumination (for example Köhler illumination
Köhler illumination
Köhler illumination is a method of specimen illumination used for transmitted and reflected light optical microscopy. Köhler illumination acts to generate an extremely even illumination of the sample and ensures that an image of the illumination source is not visible in the resulting image...
and phase contrast illumination) and are more akin to webcam
Webcam
A webcam is a video camera that feeds its images in real time to a computer or computer network, often via USB, ethernet, or Wi-Fi.Their most popular use is the establishment of video links, permitting computers to act as videophones or videoconference stations. This common use as a video camera...
s with a macro lens. For information about optical microscopes with a digital camera in research and development see optical microscope
Optical microscope
The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the...
.
History
An early digital microscope was made by a lens company in TokyoTokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
in 1986, which is now known as Hirox
Hirox
Hirox is a lens company in Tokyo, Japan that created the first digital microscope in 1986. This company is now known as Hirox Co LTd. Hirox's main industry is digital microscopes, but still makes the lenses for digital microscopes and rangefinders....
Co Ltd. 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 the large amount of digital information coming from the digital camera. But some of their current advanced versions are all-in-one and do not require a computer. Other versions of digital microscopes were later developed by Keyence
Keyence
is a company which produces sensors, barcode readers, vision systems, measuring equipment and digital microscopes.-Global:Keyence Corporation is a global company with a network of 16 international organizations that specializes in factory automation...
Corp and Leica Microsystems
Leica Microsystems
Leica Microsystems GmbH is a leading global manufacturer of optical microscopes, equipment for the preparation of microscopic specimens and related products. There are ten plants in eight countries with distribution partners in over 100 countries...
. Invention of the USB port resulted in a multitude of USB microscope
USB microscope
A USB microscope is a low-powered digital microscope which connects to a computer, normally via a USB port. They are widely available at low cost commercially. In essence USB microscopes are a webcam with a high-powered macro lens and generally do not use transillumination but rely on incident...
s ranging in quality and magnification. They continue to fall in price, especially compared with conventional optical microscope
Optical microscope
The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the...
s.
Optical and digital microscopes
A primary difference between an optical microscope and a digital microscope is the magnificationMagnification
Magnification is the process of enlarging something only in appearance, not in physical size. This enlargement is quantified by a calculated number also called "magnification"...
. With an optical microscope the magnification is found by multiplying the lens magnification by the eyepiece 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 is found by how many times larger the sample is reproduced on the monitor. Therefore the magnification will depend on the size of the monitor. The average digital microscope system has a 15" monitor, would result in an average difference in magnification between an optical microscope and a digital microscope of about 60%. Thus the magnification number of an optical microscope is usually 60% larger than the magnification number of a digital microscope.
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 an optical microscope. With the optical microscope, the lenses are made for the optics of the eye. Attaching a CCD camera to an optical microscope will result in a 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 for the microscope may dictate which microscope is preferred.
Resolution
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 viewField of view
The field of view is the extent of the observable world that is seen at any given moment....
(FOV) by 1600.
Increased resolution can be accomplished by creating a sub-pixel image. The Pixel Shift Method uses an actuator
Actuator
An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which...
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.
2D Measurement
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
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 theses 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
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.Types
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.Most of the cheaper microscopes which connect via USB have no stand, or a simple stand with clampable joint
Joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...
s. They are essentially very simple webcam
Webcam
A webcam is a video camera that feeds its images in real time to a computer or computer network, often via USB, ethernet, or Wi-Fi.Their most popular use is the establishment of video links, permitting computers to act as videophones or videoconference stations. This common use as a video camera...
s 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×.
Devices which connect to a computer require software to operate. 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 system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s—in Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
, images from microscopes which do not require special drivers can be viewed and recorded from "Scanners and Cameras" in Control Panel.
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 may be available. Resolution, image quality, and dynamic range vary with price. True spatial resolution may be increased by pixel shifting
Pixel shifting
Pixel shifting is a method implemented by plasma TV Manufacturers that prevents static images from causing image retention and burn-ins. The entire video frame is moved periodically so there are effectively no static images...
technology. Better units have larger sensors; the sensor may be cooled to reduce optical noise
Noise (video)
Noise, in analog video and television, is a random dot pattern of static displayed when no transmission signal is obtained by the antenna receiver of television set and other display devices...
. Systems with a lower number of megapixels have a higher frame rate (30fps) and faster processing. The faster processing can be seen when using functions like HDR (high dynamic range
High dynamic range
High dynamic range is a term generally used for media applications such as digital imaging and digital audio production...
). In addition to general-purpose microscopes, instruments specialised for specific applications are produced. These units can have a magnification range up to 0-7000x, are usually all-in-one (don't require a computer), and can be portable. They also differ from the cheaper USB microscopes in not only the quality of the image but the quality of the system's construction giving these types of systems a longer lifetime.