The camera position on the TEM column generally determines the field-of-view (FOV) and "magnification-factor" of a camera with respect to the microscope read-out magnification. Placement options are the Side-Mount, Mid-Mount and Low-Mount. The wide-angle, Side-Mount position is the most popular for its large field-of-view. Unique in the marketplace is AMT's introduction of the Mid-Mount camera position. The Mid-Mount position takes full advantage distortion-free documentation and the now available use of larger format digital sensors. For high magnification and premium resolution, the Low-Mount position is a popular choice among material scientists and bio-nanoscientists.
The Side-Mount systems are positioned perpendicular to the optical axis of the microscope, in the area typically reserved for the 35mm film camera, and well above the fluorescent viewing screen. This configuration provides the widest viewing area and highest apparent sensitivity. The field-of-view (FOV) matches or exceeds plate film. In operation, the electron beam interacts with the phosphor coated scintillator, projecting an image to a mirror, which in turn projects the image to the optical lens/sensor assembly located outside the vacuum. The scintillator mechanics retract to allow full use of the normal viewing screen. These systems are ideal for typical work in Biology and Clinical Pathology, where context is extremely critical at lower magnifications, coupled with middle to high magnifications used for applications such as Virology. The Side-Mount systems are also useful for diffraction work where a large field-of-view is advantageous.
The benefits of the Side-Mount camera include the greatest field-of-view (FOV) at a reduction in the stated microscope magnification. The camera is lens-coupled and optimized for using pneumatics to retract and insert the scintillator/mirror. As a trade-off to the great FOV, the microscope-dependent projector lens fixed aperture can inadvertently reduce the sensor dimension.
Pioneered by AMT, the Mid-Mount configurations are positioned on-axis in direct line with the electron beam. Cameras mounted in this position are at the level or close to that of the traditional film/plate camera, and can be mounted directly beneath the fluorescent viewing screen. Taking advantage of this optimized film position, the Mid-Mount has virtually no TEM related image distortion. This location supports a large field-of-view (FOV), while still allowing the TEM to reach lattice resolution. The Mid-Mount phosphors can be physically larger than the Side-Mounted phosphor, which in turn results in larger phosphor "pixels" and better optical quality.
The greatest benefit of the Mid-Mount camera position is that it optimizes the microscope manufacturer's design for distortion-free documentation. In addition, the stated microscope magnification is similar to the image at the sensor.
Examples of the Mid-Mount cameras are the XR16M-ActiveVu, XR611M-B, XR81M-B, XR401M-B sCMOS, and XR280M-A sCMOS.
Low-Mount cameras are mounted on-axis in direct line with the electron beam, are mounted below the traditional film/plate camera, and have the highest magnification factors at maximum resolution. With magnifications of 10x or more beyond the stated microscope magnification, this position is favorable for work typical of materials research. The XR16L-ActiveVu / XR611L-B / XR81L-B / XR401L-B sCMOS are examples of the Low-Mount camera systems.