Who invented stereo microscope

This is a preview of subscription content, access via your institution. Rent this article via DeepDyve. Beck R 75 Jahre Leitz-Binokularmikroskope. Leitz Mitt Wiss u. Technik — Google Scholar. Jena Z Naturwiss 29 NF 22 : — Czapski S Das stereoskopische Mikroskop nach Greenough.

Z Wiss Mikrosk — Ford B Single lens — the story of the simple microscope. Gardner AT Yankee stonecutters — the first American school of sculpture. Gause H Siegfried Czapski — Greenough HS Observations sur les larves d'oursin. Bull Soc Zool Fr Many people assume that because DNA is so small, we can't see it without powerful microscopes. But in fact, DNA can be easily seen with the naked eye when collected from thousands of cells. The light microscope remains a basic tool of cell biologists, with technical improvements allowing the visualization of ever-increasing details of cell structure.

Contemporary light microscopes are able to magnify objects up to about a thousand times. A dissecting microscope is used to view three-dimensional objects and larger specimens , with a maximum magnification of x. This type of microscope might be used to study external features on an object or to examine structures not easily mounted onto flat slides. Both microscopes have similar features.

A dissection microscope is light illuminated. The image that appears is three dimensional. It is used for dissection to get a better look at the larger specimen.

The objectives are perhaps the most important component of a dissecting microscope as they are the main lenses that magnify the object and gather the light and produce the image seen on the ocular lenses.

Initially discovered by Robert Hooke in , the cell has a rich and interesting history that has ultimately given way to many of today's scientific advancements. Two men are credited today with the discovery of microorganisms using primitive microscopes: Robert Hooke who described the fruiting structures of molds in and Antoni van Leeuwenhoek who is credited with the discovery of bacteria in It turns out that cells are the smallest structural unit of living organisms.

This finding eventually led to the development of the theory that all living things are made of cells. Without microscopes, this discovery would not have been possible, and the cell theory would not have been developed. When was the stereo microscope invented? Today's stereomicroscope designs feature high numerical aperture objectives that produce high contrast images, which have a minimum amount of flare and geometrical distortion.

The observation tubes will accommodate high-eyepoint eyepieces having a field of view up to 26 millimeters, with a diopter adjustment that allows the image and reticle to be merged into focus simultaneously. In addition, many models sport high zoom ratios up to 12xx that provide a wide magnification range between 2x and x and reduce the necessity to change objectives. Ergonomic features incorporated into the microscope designs help to reduce fatigue during long hours of operation, and new accessories enable modern stereomicroscopes to image specimens that were impractical just a few years ago.

The human eyes and brain function together to produce what is referred to as stereoscopic vision, which provides spatial, three-dimensional images of the objects surrounding us. This is because of the brain's interpretation of the two slightly different images received from each of the retinas. The average human eyes are separated by a distance of approximately millimeters, and each eye perceives an object from a somewhat different viewpoint that differs by a few degrees from the other.

When transmitted to the brain, the images are fused together, but still retain a high degree of depth perception, which is truly remarkable. The stereomicroscope takes advantage of this ability to perceive depth by transmitting twin images that are inclined by a small angle usually between 10 and 12 degrees to yield a true stereoscopic effect. In some stereomicroscope systems, specimens are imaged utilizing two separate compound microscope optical trains, each consisting of an eyepiece, an objective, and intermediate lens elements.

Other designs employ a common objective shared between two individual optical channels. Two distinct images, originating from slightly different viewing angles, are projected onto the microscopist's retinas, where they stimulate nerve endings to transfer the information to the brain for processing. The result is a single three-dimensional image of the specimen whose resolution is limited by the microscope optical system parameters and the frequency of nerve endings in the retina, much like the limiting grain size in photographic film or the pixel density in a charged coupled device CCD digital camera.

Stereomicroscopes can be roughly divided into two basic families, each of which has both positive and negative characteristics. The oldest stereomicroscopic system, named after the inventor Greenough, utilizes twin body tubes that are inclined to produce the stereo effect. A newer system, termed the common main objective introduced above , utilizes a single large objective that is shared between a pair of eyepiece tubes and lens systems.

Either type of microscope can be equipped with step-type individual lenses to change magnification, or a continuously variable zoom-type magnification system. The following discussion addresses the advantages and disadvantages of both the Greenough and common main objective stereomicroscope designs. The Greenough design, introduced by Zeiss at the turn of the twentieth century, consists of two identical and symmetrical optical systems each containing a separate eyepiece and objective arranged in accurate alignment within a single housing Figure 4.

A major advantage of this design is the high numerical apertures that can be obtained because the objectives are very similar in design to those utilized in classical compound microscopes. In general, the lower portions of the body tubes, containing the slender objectives, are tapered and converge at the best focus of the object plane.

The upper end of the body tubes project a pair of images into the observer's eyes, normally with a pair of standard eyepieces. The size, focus, rotation, and centering of the two images must be held constant within very tight tolerances, so that the eyes view essentially the same scene. The one departure from sameness is the slightly different viewing angle at which each image is projected onto the retina.

Because of the convergence angle, typically ranging from 10 to 12 degrees in modern designs, the left eye views the object from the left side while the right eye views the same object from a slightly different perspective on the right side. A pair of erecting prisms or mirror system is utilized to de-rotate and invert the magnified image received from the objectives and present it to the observer as it would appear without a microscope.

The body tubes are built to provide a straight line-of-sight in some designs, while others enlist the aid of additional prisms to allow inclination of the tubes and a more natural viewing position for the microscopist.

Because the image-forming light rays pass through the complex lens system on center, the quality of the image is symmetrical about its center, as is the case with most compound microscopes. In addition, correction for optical aberrations in Greenough-type microscopes is less difficult than with common main objective designs, because the lenses are smaller, axially symmetrical, and do not rely heavily on light rays passing through the objective periphery.

A distortion artifact arises in the Greenough microscope design due to the oblique separation of each body tube from a common axis.

Termed the Keystone effect, this distortion causes the area on the left side of the right eye to appear slightly smaller than that on the right-hand side of the same image, and of course the reverse is true for the left eye's image see Figure 5.

Keystone distortion arises from the fact that the intermediate images produced by each body tube are inclined with respect to the specimen plane, and tilted relative to each other, so that only the central regions are in simultaneous focus at identical magnifications.

The result is that peripheral portions of the viewing field are focused either slightly above or below the actual specimen plane and have very small differences in magnification, although the eyes usually compensate for this effect and it is often not noticeable to the microscopist. During prolonged observation periods, however, fatigue and eyestrain can be accelerated by the Keystone effect. The small change in magnification and focus across the field of view in Greenough stereomicroscopes might be noticed in a photograph or video image produced through one side of the instrument, especially if the object is primarily flat and rectilinear.

In photomicrography, focus discontinuities brought on by the inclination angle are easily compensated by tilting either the specimen or one of the beam paths so that the microscope optical axis is perpendicular to the lateral specimen plane.

When undertaking measurements with a reticle, the linear eyepiece grid should be positioned in a vertical direction to minimize the Keystone effect.

Another solution is to tip the specimen or the microscope five or six degrees and negate the convergence. Explore axial and lateral chromatic aberrations seen in an optical microscope with this interactive tutorial.

Common main objective stereomicroscope designs center on the refracting action of a single, large diameter objective lens, through which both the left and right channels view the object. Each channel operates as an independent optical train parallel to the other this is the reason they are also known as parallel microscopes; Figure 4 , and there is collimated light between the individual channels and the objective the image is projected to infinity.

This arrangement guarantees that convergence of the left and right optical axes coincide with the focal point in the specimen plane. Because this parallel axis arrangement is usually extended to include the eyepieces, the left and right images are viewed by the microscopist's eyes with little or no convergence.

A major advantage of the common main objective system is that the optical axis of the objective is normal to the specimen plane, and there is no inherent tilt of the image at the eyepiece focal plane.

Although in most situations there are the usual 10 to 12 degrees of convergence at the specimen, the brain is not used to interpreting three-dimensional images without convergence, leading to a unique anomaly that is specific to CMO stereomicroscopes. When viewing specimens through this type of microscope, the center portions of the specimen appear to be slightly elevated, so that a flat specimen now appears to have a convex shape.

For example, a coin will have the appearance of being thicker in the center, so it would rock from side to side when inverted on a flat surface. This artifact is referred to as a perspective distortion , but should not cause concern unless the microscope is utilized to judge flatness or height see Figure 5. Specimens with complex or rounded shapes, while displaying a certain amount of perspective distortion, often do not appear to be distorted when viewed through the stereomicroscope. Perspective distortion is sometimes referred to as doming or the globular effect , and results from a combination of keystone and pincushion distortion.

As an example, presented in Figure 5 is a slightly exaggerated illustration of how a United States Lincoln penny, a disc-shaped flat coin, would appear in a stereomicroscope with severe perspective distortion. The original penny is shown at the top of the illustration to have a flat surface. Just beneath are the images projected simultaneously by the microscope to both the left and right eyes, which demonstrate an asymmetrical pincushion distortion directed toward the central axis of the microscope.

The final result is perception of a dome- or globe-shaped object when the images from both eyepieces are projected onto the retinas and fused together in the brain. Most high-end research grade common main objective stereomicroscopes produced by the major manufacturers have virtually eliminated this artifact, but it still occurs in some less expensive microscopes. Another artifact often encountered with common main objective stereomicroscopes is that small amounts of off-axis aberrations such as astigmatism, coma, and lateral chromatic aberration appear in the center of each image.

This occurs because each optical channel is receiving light rays from an off-center region of the large objective instead of directly from the center, where aberrations especially those occurring off-axis are at a minimum or practically non-existent in lenses with the best optical corrections. The effect is generally not noticed when both eyes are employed to view the specimen, but a photomicrograph or digital image may have asymmetric geometry across the field.

In general, the chromatic aberrations are difficult and expensive to correct, especially considering the large size and volumes of glass used in manufacture of the objectives. Some CMO stereomicroscope designs have made this a non-issue by providing the facility to offset the large central objective, positioning it on the axis of either the left or right side channel.

Other microscope designs even provide a means for replacing the large objective with a conventional infinity-corrected objective that can be utilized to view and photograph specimens at high magnifications and numerical apertures. The greatest design feature and practical advantage of a common main objective stereomicroscope, as with most modern microscopes, is the infinity optical system.

This allows the effortless introduction of accessories, such as beamsplitters, coaxial episcopic illuminators, photo or digital video intermediate tubes, drawing tubes, eyelevel risers, and image transfer tubes into the space between the microscope body and head. It is also possible to place these accessories in the space between the objective and zoom body, although this is rarely done in practice. Because the optical system produces a parallel bundle of light rays between the body and microscope head, the added accessories do not introduce significant aberrations or shift the position of images observed in the microscope.

Such versatility is not available in stereomicroscopes designed around the Greenough principles. It is a difficult task to determine which of the two designs CMO or Greenough is superior, because there are no universally accepted criteria for comparing performance between the stereomicroscope systems.

Common main objective microscopes, in general, have a greater light-gathering power than the Greenough-design and are often more highly corrected for optical aberration. Some observations and photomicrography might best be conducted utilizing a CMO microscope, while other situations may call for features exclusive to the Greenough design. As a consequence, each microscopist must make the determination whether one design will be more appropriate for the task at hand and use this information to develop a strategy for stereomicroscopy investigations.

In most circumstances, the choice between Greenough or common main objective stereomicroscopes is usually based on the application, and not whether one design is superior to the other. Greenough microscopes are typically employed for "workhorse" applications, such as soldering miniature electronic components, dissecting biological specimens, and similar routine tasks.

Recently, a wide range of plastics have also been used. In a genuine stereo microscope, each eye must be able to observe the object through a dedicated microscope.

Parallel to the development of telescopes and microscopes, work was already being done to design instruments for both eyes in the 17 th century. His goal was not a three-dimensional image as such; he believed that image quality could be improved by viewing objects with both eyes at the same time. The principle of stereoscopic vision was not known at that time — it was first described by the English physicist Charles Wheatstone in the year It consists of two complete microscopes —one for each eye.

In , John Leonhard Riddel, a chemistry professor and postmaster in New Orleans, presented a binocular microscope with a single objective and a prism system. The prisms were arranged so that the right eye only received light from the right half of the objective and vice versa.

The image was three-dimensional, but confusing because the relief appeared reversed pseudoscopic. Binocular microscopes of the day featured a simple lens system and the same design as traditional compound microscopes.

They only attained low magnifications and did not permit significant working distances. These dissecting microscopes, as they were then known, were used primarily in biology for dissection purposes; there were no technical applications for them at the time.