Microscope Camera Adapters

Photo Eyepieces for Large Cameras

microscope camera adapters — Thu, 17 May 2007 10:44:28 +0000

Eyepieces work in combination with microscope objectives to further magnify the intermediate image so that specimen details can be observed. Oculars is an alternative name for eyepieces that has been widely used in the literature, but to maintain consistency during this discussion we will refer to all oculars as eyepieces. Best results in microscopy require that objectives be used in combination with eyepieces that are appropriate to the correction and type of objective. Inscriptions on the side of the eyepiece describe its particular characteristics and function. Often eyepieces will also have an H designation, depending upon the manufacturer, to indicate a high-eyepoint focal point that allows microscopists to wear glasses while viewing samples. Other inscriptions often found on eyepieces include WF for Wide-Field; UWF for Ultra Wide-Field; SW and SWF for Super Wide-Field; HE for High Eyepoint; and CF for eyepieces intended for use with CF corrected objectives. (more…)

Understanding Standard Filter Threads and Adapters

microscope camera adapters — Thu, 17 May 2007 10:43:19 +0000

Filter thread sizes are important to microscope adapters, because it is often much cheaper to make a custom adapter with a larger thread size than the camera provides. This is due to the difficulty of machining precision threads up to a shoulder, versus machining threads on the outside of a cylinder without a shoulder. The larger cylindrical adapter can then be adapted in turn to the camera’s smaller thread size by using an inexpensive, off-the-shelf step-up ring. Filter threads are not standardized other than holding to a metric form of arbitrary nominal size, but over the years camera manufacturers have come to mostly use a limited set of whole-millimeter sizes. (more…)

Understanding C-Mount and CS-Mount Standard Mechanics, Optics, and Cameras

microscope camera adapters — Thu, 17 May 2007 10:42:08 +0000

The C-mount standard is a widely-used method of connecting small cameras to lenses, such as mounting a lens on an industrial camera, or for connecting trinocular phototubes on microscopes to cameras. The “C” is said to stand for “cine”, the original application being movie camera lenses, such as were made by Arri, Bolex, Angenieux, Bell & Howell, and Eclair. This standard is both an optical and mechanical specification for the optical source and receiver. The optical source side consists of a tube concentric with the optical axis, ending in a 1″-32 male thread, projecting from a larger flange perpendicular to the axis. The inside diameter of this tube can vary, but practically speaking, an ID of about 0.9 inches is an upper limit to provide enough metal beneath the threads for mechanical strength in the tube. The projection of the male threaded portion from the flange is 4mm (0.157″), and the depth of female threading is 4.5mm (0.177″).

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Understanding and Avoiding Vignetting

microscope camera adapters — Thu, 17 May 2007 10:40:40 +0000

The Ramsden disc also called Ramsden circle produced by the microscope eyepiece is the circular field image formed some distance the vertex or eye-relief distance above the top of the eyepiece. A good eyepiece forms a Ramsden disc equal to or larger than the size of the pupil of the human observer’s eye. The human pupil varies in size with lighting and the observer’s age, so the Ramsden disc should be designed somewhat larger than the largest eye pupil, which means that the eye and the eye’s pupil can move about without cutting off some of the eyepiece image. The size and axial location of the Ramsden disc is also called the exit pupil of the eyepiece. The exit pupil is a critical characteristic for analyzing any optical system, and especially important when coupling two optical systems to each other, such as the eye to the microscope, or a camera to the microscope. To avoid vignetting, the corresponding entrance pupil of the camera must be equal to or smaller than the eyepiece exit pupil, and the camera entrance pupil must be positionable within the eye-relief distance. You can think of the eyepiece exit pupil as a projected map not really an image of the microscope field of view, and the camera’s entrance pupil as a map of the camera’s digital image sensor or film frame in the old days. (more…)

Selecting a Camera for Digital Photomicrography

microscope camera adapters — Thu, 17 May 2007 10:38:25 +0000

We’ve had inquiries about what consumer or presume digital cameras are good for adapting to photomicrography. Some criteria of desirability are accessory threads that permit flush mounting of an adapter - Most current digital cameras such as the compact consumer types don’t have them. Some cameras with turret type lenses have threads or a bayonet fitting on the camera body which accepts a special adapter which surrounds the turret with a tube that terminates in standard filter threads; this is an acceptable compromise. Optical dimensions close to the human eye - This permits a direct optical path for through-the-eyepiece coupling, and avoids vignetting. See the section on Understanding and Avoiding Vignetting below. (more…)

Making Microscope Camera Adapters

microscope camera adapters — Thu, 17 May 2007 10:36:00 +0000

This page describes the custom adapters made to fit a variety of cameras, microscopes, and medical instruments, for most of these adapters, they are $85 to $175, depending on the complexity. Old and new optical instruments are thereby fitted into the modern age of digital imaging. Besides the mechanical attachment, these adapters apply one of several optical principles to couple the camera to the microscope, including Afocal, through the normal eyepiece to inexpensive small-format digital cameras; Focal, from a photoport to lensless digital SLR cameras and Afocal, through a custom photo-eyepiece for large-lensed digital cameras. The first dimensional step is to turn down the cylinder, leaving a raised ridge of 37 mm diameter, ready to take on the outside threads. We chose to thread a length of 5 mm, which was about twice the length of the inside threads on the camera turret. Using the threading bit to turn the smooth diameter makes it easy to leave 60 degree bevels on all the stepped edges. (more…)