Sometimes, words are not enough. Observations made with microscopes can be very difficult to describe to others, particularly observations that have not been seen before. Scientists are often left to describe their findings in terms that, hopefully, present true representations of a sample that are fully understandable by other scientists. Thus, many have turned to imaging to document their work.
Optical Lens Options
With the availability of more optical lens options and the ability to send the images to a computer, using a camera with microscopy work is an area of increasing interest. The combination of high resolution cameras and advanced microscopes has opened the door to better options for improving resolution and for sharing of the images, an increasing demand in investigative science. Cameras are not used with all microscopes now, but one can envision a time when all microscopes, even those requiring less magnification, will have a camera to capture results for sharing and reporting. Here, considerations for capturing images from a microscope are discussed.
Images from Microscopes: Difficult to Describe
Reporting of findings uncovered with microscopes can be difficult for many scientists. Even if a unique finding can be described, a reader is challenged to accurately reproduce an image using just the written word. This is a situation where the expression ‘a picture is worth a thousand words” is so true.
With most microscopes, current camera technology can be used to capture an image with some effort. Even cell phone cameras and family-use cameras could be used when high resolution is not needed. This approach has limited application and may not even suffice for some high school science work. In more typical advanced scientific investigative work, documenting true-to-life samples with an advanced camera is needed from microscopy.
Some microscopes now have a camera built in as a single device with its own eyepiece. There are also methods that will attach a camera to a microscope eyepiece for capture. However, selecting a camera for microscopy is not simple as there are many variables to consider.
The Right Camera Fills the Need
As with most scientific equipment, there are a number of different variables to consider in selecting a product. Besides the desired microscope specifications, the best camera choice will depend on the characteristics of the image to be captured, the capture environment (i.e., lighting level), and what is to be done with captured images. In many situations, it will be desirable to connect to a computer. This allows more options for viewing, storage, sharing, and image manipulation for reporting and display.
In camera consideration, an early decision must be made to whether a still image or a video is most appropriate. While it may be tempting to have both capabilities, there is a trade-off with the much higher cost to have both. In addition, some combination devices operate at fewer video frames per minute.
In looking for still images, more category-level decisions need to be made. Most significant is whether monochrome images will be adequate. Generally less expensive and easier to work with, some work is better documented in black-and-white.
A Proven Option
Next, one must consider the trade-offs regarding price and sensitivity level of a CCD (charge coupled device) or a CMOS (Complementary metal–oxide–semiconductor) sensor technology. Simplifying things, CMOS chips may be the better cost option, but usually there are some performance losses, such as with sensitivity. Pixel size, shutter type and many other variables, along with cost, can influence the proper choice in sensor.
These trade-offs are obvious if you look at a few very popular sensors for Microscopy applications.
The Aptina MT9P031 (5Mp, 2.2 micron pixel) CMOS image sensor is very popular with low-cost microscopy cameras. Relative to resolution and pixel size it has excellent image quality for its relative low cost. However, its sensitivity is compromised in many applications due to its pixel size.
The OnSemi Truesense CCD’s have larger pixels (7.4 & 5.5 micron) and a very low noise floor due to the CCD benefits. They come in a variety of resolutions and offer the best image quality in the industry. Of course, the downside is the trade-off in cost. These sensors are much higher cost than the Aptina (& similar vendors) small pixel size CMOS image sensors.
A new vendor of large pixel size CMOS image sensors is CMOSIS. The new 5.5 micron pixel and advanced architecture provides excellent image quality, fast frame rates at a lower cost than CCD’s but still a higher cost than the small pixel sized sensors. They have a variety of resolutions available that have excellent sensitivity. Some Microscopy customers prefer these sensors since they make a very good compelling value relative to these trade-offs.
Camera vendor, the Imaging Solutions Group, (ISG, Fairport, NY, USA) offer cameras with each of these types of sensors. ISG has solutions that enable microscopy customers to make these trade-offs. They offer cameras in a variety of interfaces, architectures and the ability to customize each camera for any individual application.
For most advanced investigative work, it is necessary to have high quality images, so the image resolution is perhaps the most critical operating variable, as with most cameras. Cameras that capture 1.3 to 10 megapixels seem to be appropriate for most microscopy situations.
The images below show a simple color image and the corresponding processed image. This is a common way to automate the results of diagnostic imaging. In this case, a cell will fluoresce if infected and the resulting dots can be counted to determine the percentage of infected cells per unit area.
Another decision factor is whether the images are for use on a television or a computer. A television may be required for display to a certain audience, but resolution is sacrificed. There are many low cost NTSC/PAL (TV) monitors on the market that will work. A computer display is excellent for viewing still images and video with higher resolution. Manipulation and display methods are much more appropriate with a computer. In some cases, an LCD on the camera will provide an adequate image for preview and for making a decision to capture the image.
Other variables will depend on the capture situation and could include: the frame rate for video, color fidelity and reproducibility, lighting, fluorescence requirements, the dynamic range needed, and other situational factors like the need for image polarization, 3D display, and stereo imaging needs. In some cases, the image storage requirements may be a factor in the approach selected.
Another consideration that cannot be overlooked is the method used to connect the camera to the computer. One of the more common methods is with a USB connection. Historically, microscopy applications favored USB2 but the newer USB3 interface provides much higher bandwidth to move high resolutions images more efficiently. Other interfaces such as FireWire™, Ethernet (including GigE) can be used successfully. There are other connect options which may be appropriate to consider. These trade-offs have price impact. The more features and more advanced quality image desired, the higher the price.
For Best Results, Check Around
Selecting the right camera is not easy and is important for properly capturing scientific work, particularly when results can be difficult to describe and reproduce. The options discussed in this article simplify the situation. It would be best to contact a trusted camera expert, such as the imaging experts at Imaging Solutions Group (ISG), to identify the best option for your needs. ISG has a number of cameras that can meet the wide range of needs for microscope capture.
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