The microscope camera DFK MKU130-10x22 is, to our knowledge, the only camera currently on the market that can be mounted on nearly all microscopes and that can capture the complete field of view, as seen by the observer, without additional optical adapters. The motivation to build this camera came from an oft-posed support question: Why does my C-mount camera only capture a small portion of the image I can see when I look through the ocular? The following images illustrate the situation: 
Images from C-mount cameras:  Restricted field of view. These cameras require a lens adapter in order to capture a full field of view:
 Download the original images in this post.
The article originally appeared with the title:
DFK MKU130-10x22, Modular Microscopy Camera from The Imaging Source - a New Way to a 'Universal Adaptation?'
The conclusion of the extensive test was:
[..] the camera exhibits very good qualities and an equally positive price/performance ratio.
At the end of 2014, The Imaging Source (Bremen, Germany) brought a new microscope camera on the market with the intention of offering a detachable eyepiece camera with excellent image quality which could be used with practically every standard microscope on the market:
The camera was tested on large-field microscopes from the manufacturers Leitz, Leica and Carl Zeiss Jena with good results, although it must be said that some loss of edge focus occurs at higher magnifications. This reduction of edge focus is caused by the included eyepiece which can, however, usually be exchanged with the original manufacturer's eyepiece.
Even older optical microscopes (e.g. with a cast iron base, mirrors and basic objective lenses with lower field numbers such as the Studio-Mikroskop and Enuro-Optik) and microscopes with non-standardized eyepieces and objective lenses with an even smaller diameter (e.g. the Bresser Biolux AL that was sold a few years ago through grocery stores) could be successfully used. With all of these microscopes, the camera delivered smooth live image display of the real image, video-clips and color images.
A comparison with the Leica camera, MC 170 HD, can be summarized as follows: For routine applications, such as the documentation of bright-field images, the camera from The Imaging Source need not fear comparison with a leading manufacturer's modular camera solution as it pertains to image quality.
Moreover, the authors describe in great detail how the camera's wide-ranging functionality was achieved. This is made possible by a special 5.3 mm focal length autofocus lens which complements the camera's 13 MP Sony sensor and which is further enhanced by a standard eyepiece and an adjustable camera tube. The adjustable camera tube allows for vignette-free illumination and the setting of the eyepoint. With the correct adjustment of the camera tube, the camera delivers the same image the observer would otherwise see through the microscope's eyepiece. The authors especially emphasize the reliable and precise functioning of the autofocus which enables the operator to select and view areas of the image without the need for additional manual adjustment.
The authors also tested the software applications IC Capture, IC Measure and IC Full Screen Presenter. These software products can be downloaded free-of-charge from the manufacturer's website. IC Capture is designed for camera control, acquisition of single images and image sequences as well as videos. With IC Measure, lines, angles, circles and polygons can be measured on-screen and saved. IC Fullscreen Presenter allows for the full-screen presentation of the microscope's live image with an optional foot pedal available.
With the camera presented here, the manufacturer has made an important contribution to the concept of the 'universal camera.' In comparison to other add-on cameras where upon disassembly an operator could look at the sensor directly, the camera tested here presented a complete and self-contained device - comprised of a lens system, autofocus and small-dimensioned aperture. These components ensure a deep depth of field and efficient correction of any deviations from the ideal focal plane. Which is why, according to our testing, this camera is capable of delivering usable images from diverse microscope designs and manufacturers. The manufacturer-provided eyepiece is made for tubes with an O.D. 30 mm and a fully corrected intermediate image. When the intermediate image is not fully corrected, it is a matter of 'luck' as to how much the residual optical error will cause a visible reduction in quality.
The camera's universal application is further supported by the fact that the camera is not limited to its own eyepiece but can also be used in conjunction with the original eyepieces of various microscope manufacturers. In this way of course, the problem of the uncorrected intermediate image is avoided altogether by combing the camera with the original compensating eyepiece.
The camera sensor has proven itself very efficient; it can indeed 'keep up with' the sensors from much costlier and more complex designs of leading microscope manufacturers.
When the complete field of view needs to be imaged, it is a disadvantage that the edge focus of the included eyepiece is less than ideal. For images with perfect edge focus, only the middle two-thirds of the field of view should be used. Other Plan-corrected large field eyepieces from leading manufacturers can - also in combination with the camera - deliver visibly better edge focus.
A real 'highlight' is the averaged and selective autofocus. This works so quickly and accurately that it delivers reproducible precision in image focus which (depending on the eye) could be seen to rival, or even be superior to, subjective visual focus.
All in all, the camera offers excellent features as well as an excellent price-to-performance ratio.
With regards to the video function, it could be discussed if a video recording via standard camera or video camera might be advantageous since, as a rule, these easily produce real-time images on the monitor even while recording in color at full HD and additionally require less disk space than the AVI format. As a positive side effect it should be noted that the camera as such, outside of its application in microscopy, can also be used for photos and videos which feature excellent depth of field and whose quality (especially in close ups) is more than adequate for simple documentation purposes. According to our tests, the camera could even prove itself useful for some medical applications such as the quick documentation of wounds and other changes in the skin or as a dental camera.
It would be desirable, if the camera came with even higher performance eyepieces with less field curvature than the Meiji eyepiece with which is currently equipped. Additionally, it would be suggested that several camera tubes of various or variable (i.e. adjustable) diameters be made available. This could be accomplished with relatively little effort since these are merely cylindrical tubes with a standardized screw thread. This would enable the customer to acquire a tube whose diameter properly fits their eyepiece head / eyepiece or which is made to adapt with fewer necessary adjustments. Because the software offers extensive options to manually adjust a multitude of parameters, a suggestion would be to integrate a 'reset' function which with one mouse click would return the software to standard default settings.
Since the camera body has its own lens with autofocus and zoom function, it can in principle be used as an imaging device on its own. The lens-free tube was removed here for reasons of expedience since its outer edge cast a round shadow in the field of view. It was found that this 'mini-camera' has a very wide range of settings: from infinity to approximately 4 cm. At the minimum focusing distance an object length of 5.5 cm was recorded (this corresponds to an aspect ratio of 1920 x 1080). Even here, the zoom can be used freely. The sample images shown in Figs 18, 19 and 20 attest to the camera's large depth of field and high image resolution in stand-alone operation. More advanced macro functionality can be realized by equipping the camera with a close-up filter and flash system which can work to augment the camera's own zoom optics. For orientation purposes, an achromatic close-up filter and flash system (20 diopters) from 'Magniflash' was used in such a way that at minimum focusing distance (without activation of the zoom) an object length of 2.5 cm was measured with high resolution, sharp focus and with little influence from field curvature in the way of image distortion. If motion blur is to be avoided, however, a set up like this is no longer manageable without an adjustable tripod. The 'Magniflash' system was examined in depth in an earlier issue of this magazine (Mikroskopie 2014;1: 39-51).
The software downloads which can be found on the manufacturer's website (Driver, Capture, Presenter) were easily downloaded and installed; all of the parameters and functions worked perfectly and gave no cause for complaint. The function 'vignetting' which can be activated from the 'Effects' menu is especially useful as it effectively reduces the brightness drop off at the image periphery.
When black-and-white images are needed, color saturation need only be set to 'zero' (Fig. 4 slider bar 'Saturation' in the toolbar window below left between 'Zoom' and 'White Balance Red').
It should be mentioned, however, that the HDR function used in the software only substantially lightens dark areas of the image moderately well, but nevertheless does not significantly improve overexposed areas of the image. Regarding this, specialized HDR software offers a much wider variety of contrast correction possibilities.
In order to test the video function, the camera was tested on a 'gamer' laptop (Dell XPS M 1730) which in 2008 was considered to have a 'high-end' performance standard and consequently was still a high performance computer but which was no longer considered to be state-of-the-art. This choice of computer should reflect real-world conditions since by far most operators will not continually purchase the newest generation computer; the camera should, therefore, function on a somewhat older system if it should be of interest to a larger group of potential users. In order to ensure compliance with the required USB 3 standard, the laptop was fitted with a USB 3 ExpressCard Adapter. The IC Capture software allows one to choose from 16 different video codices which do not all work on the aforementioned computer.
When one wishes to capture moving objects on video, it is advantageous to be able to follow the microscopic live image in real time on the monitor since such objects must, when necessary, be followed and their movement adapted to by adjusting the slide.
At full HD resolution (1920 x 1080) and maximum frame rate (30 FPS), only the use of a video codec enabled fluid observation of the live image on the above-mentioned laptop during the real-time recording: Y800, a codec for black-and-white videos. At full resolution and frame rate, its data volume amounts to around 34 MP per second. So whoever would like to capture detail-rich black-and-white videos at 30 FPS with full HD resolution while maintaining unrestricted real-time tracking of the live image is well served by this video codec.
An additional video codec for black-and-white (Microsoft RLE) delivered a smooth, trackable live image during live recording after the resolution was reduced to 1600 x 1200 pixels and the frame rate to 15 frames per second. The reduced data load at this setting, however, corresponded to only a 19 MB reduction per film second.
For color videos, on the other hand, there is no codec which would, at maximum frame rate (30 FPS) and full HD resolution (1920 x 1080), enable parallel recording and smooth live-observation via the monitor. At 30 FPS, only the 'unspecified' mode delivered a smooth image in real-time when the resolution was reduced to 1280 x 720 pixels (data volume: 45 MB per second). At a lowered frame rate (15 FPS), the following codices enabled real-time observation via monitor during video recording (information given for resolution and data volumes): 'unspecified' (1280 x 960, 39 MB/s), RGB 24 (1280 x 720, 43 MB/s) and Microsoft Video 1 (1280 x 960, 1.7 MB/s high data compression!). 'Unspecified' and 'RGB 24' largely comparable and usable results. Because of its high data compression and resulting pixilation (or more specifically, the spotty image artifacts appearing in homogenous areas), 'Microsoft Video 1' shouldn't be used if a lot of importance is placed on high image quality. A short video clip (full HD, codec 'unspecified') of the epithelial cell phase contrast specimen from Fig. 10 taken using a student microscope Leitz HM-Lux 3, Periplan-GF-Eyepiece 10x and Phaco L 32/0.4 objective can be found on the internet. This clip illustrates the realization of a video sequence using simple microscope equipment. The phase contrast produced on the student microscope used was created without Köhler illumination but instead with simple annular phase rings which were inserted in a brightfield dry condenser. Using the lens-free tube, the camera body (without the included eyepiece) was, as described earlier, placed directly over one of the Leitz-Periplan eyepieces.
Established in 1990, The Imaging Source is one of the leading manufacturers of industrial cameras, frame grabbers and video converters for production automation, quality assurance, logistics, medicine, science and security.
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