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CAMERA LUCIDAS AND PROJECTION EYEPIECES

INTRODUCTION & HISTORY EXAMPLES OF MICROSCOPE
CAMERA LUCIDAS

camera lucidas

INTRODUCTION AND HISTORY:

camera lucida drawingcamera lucidacamera lucida The camera lucida is an optical device which allows one to see both an object, and a drawing surface located on the table in front of the observer, superimposed in one field of view. Although originally described by Kepler in 1611, it was apparently not actually constructed until the beginning of the nineteenth century. William Hyde Wollaston developed the first widely available version which he patented in 1807. It makes use of a quadrangular prism as shown in the illustration second to the left. The initial invention was mainly used as a drawing aid for sketching subjects in front of the artist. An early example of the drawing instrument is shown to the right, and, for those interested, additional illustrations of this uncommon early example are shown on its own page. These camera lucidas were often suspended from a telescopic rod with a C-clamp to hold it to a table. Soon however, Wollaston's device was adapted to the microscope; its use made drawing what was seen through the microscope much easier and of appropriate proportions.


wollaston camera lucidawollaston camera lucida As noted above, Wollaston's original design makes use of a quadrangular prism, and with double reflecting surfaces, allows the image seen in the microscope and the image on the paper to be oriented in the same direction. Early on it was found that the prism did not need to be very wide and so narrower prisms were used inside metal housings. There are several examples of Wollaston type camera lucidas for the microscope in this collection, including the example supplied with James Smith's microscope number 22 of 1841. Used as it is for drawing a subject in front of it, the Wollaston type requires the object in the microscope to also lay in front of the observer; this then requires the microscope to be horizontal, and the observer hunching over the device and looking down. This is an uncomfortable position to sustain for any length of time. It is also difficult to view liquid specimens or those in a livebox with the microscope in any position other than vertical, so this horizontal position is both inconvenient and uncomfortable. Lastly, one has to have the pupil of their eye half centered over the prism and half centered over the drawing field, and this is again a difficult position to hold steady.


Beale camera lucida Because of the expense of making the prism, and the other disadvantages noted above, many alternative designs were also made. The simplest form, and one of the most popular, was the Beale type(named after the famed English Microscopist Lionel Beale), which uses a simple piece of tinted glass at a 45 degree angle to reflect the image. This type was commonly supplied not only with English microscopes, but also with American microscopes as well. The Beale model allows a simple superimposed view, rather than the need to 'split the pupil's view.'   The Beale model, though simpler to make and a bit easier to view, nevertheless still requires the use of the microscope in the horizontal position. A further disadvantage of the Beale design is that the image is reversed right to left.

In both the Wollaston and Beale devices, because the image is projected so close to the optical axis of the microscope, the projected superimposed image at the drawing paper may be so positioned that it partially overflows the paper onto the foot of the microscope. Also as I noted above, another disadvantage of the Beale type is that the image is reversed, right to left. Both these problems can be solved by adding a second reflecting surface further away from the optical axis, such as a mirror, or by using different kinds of prism arrangements. Many different variations of the camera lucida were devised.


camera lucida drawing As time went on, devices were developed which allowed the microscope to remain upright, and also to move the reflected image away from the axis of the microscope, avoiding the projection onto the foot, while at the same time avoiding reversal of the image. This was accomplished in the Abbe type of camera lucida(left), invented by Ernst Abbe in the 1880's. As shown in the figure to the left, in this apparatus, one component is an external mirror which is further away from the optical axis and reflects the drawing paper image into the Camera's optical parts. The other key component is a cube, split diagonally into two triangular parts which meet at 45 degrees with a partially transparent silvered surface joining them. This arrangement allows the observer to see the image in the microscope straight through the cube, while at the same time seeing the image of the drawing surface. This is accomplished as the drawing image is first reflected from the mirror, and into the cube, and then reflected again, up from the angled and partially silvered joint.

camera lucida drawingOne of the disadvantages of the Abbe device was that if the mirror needed to be tilted to any angle except 45 degrees (e.g. to get the image off the foot), the image would be elongated and therfore distorted. To eliminate this problem another accessory, the tilting drawing table was devised (right). This device was tilted at such an angle so as to make it parallel to the stage or to compensate for a change in the angle of the camera mirror. Thus the Abbe type could also be used with the microscope inclined to a comfortable 45 degrees, with the drawing table also angled to 45 degrees off the horizontal.


A still later innovation was a drawing eyepiece specifically designed to be used with the microscope either in the vertical position(one model), or inclined to 45 degrees(another model), as in the Leitz example in this collection. This obviated the need for an accesory drawing table, as the optics were designed to compensate for the angle.

I have not attempted to cover all the variations of these devices, but rather the main types. There were dozens of variations. Although there were many variations, they were all slight modifications of what I have illustrated here, these variations attempting to obviate the disadvantages. Among the camera lucidas seen on this site, details of those available to me or in the collection are described under the individual examples. Although one might think that the availability of photographic cameras immediately eliminated these devices, this is not true. Exposures on film were very complicated and tedious affairs even in the early twentieth century. It was not until automated photography equipment, and then electronic imaging became available, that the microscope camera lucida was finally (mostly) abandoned as a tool for the microscopist. This is not true for the original form used for drawing things in front of the artist. Such devices are still used and sold commercially today, though further improvements have been made.


EXAMPLES OF CAMERA LUCIDAS FOR THE MICROSCOPE:

EARLY SIMPLE WOLLASTON TYPE:

c lThis is the earliest form of camera lucida for the microscope, and was first popularized by Wollaston. This camera lucida, supplied by James Smith with a 1840 microscope, has only one adjustment for centering the prism over the optical axis. It is applied to the top of a standard eyepiece in place of the standard eyecup.

CLIP-ON WOLLASTON TYPE BY NACHET:

nachet clip-on camera lucidaThe Nachet clip-on Wollaston type of camera can work with many eyepieces and is not dependent on removing the eyepiece cap. It also has a shade with a hole to guide the user in centering his pupil halfway over the prism and halfway over the drawing surface. It also allows the angle of the prism to be varied at will, though as previously noted, this will result in distortion if at any angle except 45 degrees, unless a compensating table that can be angled above the horizontal is used with it.

WOLLASTON TYPE WITH 'FRAME':

c l This device is similar to the basic form but with the addition of a frame for a neutral density filter. This was useful because to use the Camera lucida effectively requires regulating the brightness of the drawing surface and the image in the microscope so that they are at about the same intensity. Later, more than one frame was added or, in the case of some other models, like Bausch & Lomb's most complex Abbe type, an easily selected group of filters could be used to regulate the light from the drawing while another separate group could be used to regulate the brightness of the image seen in the microscope eyepiece.

BEALE TYPE BY BAUSCH & LOMB:

c l c l This type of camera lucida was invented by Lionel Beale, a famous microscopist sometime in the 19th century, before 1854. This example produced by Bausch & Lomb of Rochester, New York, was encased in hard rubber. It was the simplest and least expensive of the several types of camera lucida that Bausch & Lomb eventually made. Like all other Beale type cameras, it uses tinted class. It was noticed in the JRMS in 1883.

SIMPLE BEALE TYPE CAMERA LUCIDA:

c lThis camera lucida replaces the eyecap on the 'top hat' type eyepiece of a standard nineteenth century eyepiece. This is one of the cheapest types of camera lucida to produce. (collection of Dr. Jurriaan de Groot)

BEALE TYPE CAMERA LUCIDA ON A 'TOP HAT' CAP FOR AN EYEPIECE OF THE 19TH CENTURY:

c lThis camera lucida is similar to the forgoing, but built on a traditional lacquered brass 'top hat' eyecap. (collection of Dr. Jurriaan de Groot)

SWIVELING BEALE TYPE CAMERA LUCIDA ON A ROUND-THE-EYEPIECE RING:

c lStill another variation of the Beale type camera lucida is attached to a ring which can be slid on to the outside of an eyepiecea and swiveled in or out of the optical axis at will. It also allows the reflecting glass to be easily changed for different degrees of tint, or in case of breakage.

A PROJECTION PRISM EYECAP ON A 'TOP HAT' CAP FOR AN EYEPIECE OF THE 19TH CENTURY:

c lThis is an early form of projection device, meant to project the image on the drawing surface or a screen. This device requires an extremely bright light source of be effective.

A NACHET TYPE CLIP-ON CAMERA LUCIDA c. 1882:

c lThis is Nachet's version of an improved prism camera lucida, as originally described in the JRMS of 1882.

ABBE TYPE CAMERA LUCIDA BY BAUSCH & LOMB:

c lThis camera lucida, invented by Ernst Abbe in the 1880's, became a popular type. It clamped around the eyepiece. It allowed one to have great flexibility in tilting the mirror to whatever angle was desired and also with variable distance from the eyepiece. At any angle other than 45 degrees, it did require the use of a tilting drawing table to avoid distortion. The prism assembly could also be swiveled out of the optical axis.

A 'DRAWING EYEPIECE' BY LEITZ:

c lThis camera lucida, first noticed in the JRMS in 1896, has an arrangement of prisms to allow the microscope to be used at a 45 degree inclination without the need for a special tilting drawing table. Originally invented in Germany and sold by Leitz, it was quickly copied and sold by Watson also.