Photomicrography

Photomicrographic accessories can be connected to all modern microscopes and provide a more realistic insight into anatomical structures than drawings. The main advantages of photomicrography are the observation of the tissue exactly as it appears and the rendering of it in color. Photomicrographs of thin sections provide an essential part of any microscopic description and, with additional tools such as digital processing, legends, markers, and arrows, can be very valuable teaching tools. However, photomicrography is of marginal usefulness for identification of powders because a photograph of a powder will show many uninformative fragments among which the diagnostic structures will be obscured. In addition, the

f&m

FIGURE 5.12 Viewing samples with different methods of illumination. (a) Transillumination; (b) polarized light; (c) compensator first-order polarization. The crystals embedded in the leaf tissue only show when viewed using polarized light. The use of compensator first-order polarization enables both the crystals and the tissue in which they are embedded to be viewed. (Images courtesy of Prof. Dr. Reinhard Länger, AGES PharmMed, Vienna, Austria.)

FIGURE 5.12 Viewing samples with different methods of illumination. (a) Transillumination; (b) polarized light; (c) compensator first-order polarization. The crystals embedded in the leaf tissue only show when viewed using polarized light. The use of compensator first-order polarization enables both the crystals and the tissue in which they are embedded to be viewed. (Images courtesy of Prof. Dr. Reinhard Länger, AGES PharmMed, Vienna, Austria.)

Focus ring clamp screw

Eyepiece tube clamp screw Visible from the zoom knob side (partially hidden).

Zoom knob

Zoom scale

Eyepiece tube clamp screw Visible from the zoom knob side (partially hidden).

Focus ring

Projection mirror section mounting screw (x4)

Filter turret selection ring

Projection mirror section

Drawing surface

Drawing surface

FIGURE 5.13 Compound microscope with a drawing tube (projecting right). (Image courtesy of Prof. Dr. Reinhard Länger, AGES PharmMed, Vienna, Austria.)

microscope has limitations in terms of depth of focus and cannot clearly portray the diagnostic details of large fragments. The characteristic features of powdered samples are best represented in drawings.

Modern photomicrography systems usually attach directly to a box on the trinocular tube. A system of lenses projects a real image onto the film or the sensitive chip (digital). If a traditional film camera is used, dark boxes for the film and tools for the automatic regulation of the exposure time are available from microscope suppliers. The addition of a daylight filter allows for the use of common daylight films. The photographic quality obtainable with film still surpasses that of digital equipment, although digital cameras are becoming the norm due to their ease of processing and ability to interface with computers. Special digital cameras can be connected directly to the microscope, which is necessary for all images with long exposure time (e.g., polarized light, fluorescence). More expensive systems have the ability to apply a micron scale to the image.

However, the microscope-digital camera interface is very expensive—often more expensive than the camera itself. More cost effective and sufficient for most photomicrography is a low-priced digital camera that can simply be held directly over the oculars to take images. The image in the microscope is optically constructed approximately 25 cm from the eyepiece, so focusing the image with the fine focus knob and setting the camera focus to 30 cm usually produces a clear image. Automatic focus is convenient but may give poor results. In addition to the ability to attach cameras to microscopes, the use of attached monitors is also very helpful in enlarging images of interest, as well as for teaching (Figure 5.15).

Chinese Herbs

Chinese Herbs

Worried For Your Health More Than Ever? Want To PREVENT Rather Than CURE Your Illness? Then WE are the only ones who can answer YOUR concern of time by presenting the exclusive work piece, the explicit and special eBook on CHINESE HERBS- the call of time.

Get My Free Ebook


Post a comment