تطور صناعة عدسات التصوير .. كتاب آلة التصوير

The evolution of the photographic lens industry:

In order to get rid of the optical defects that simple lenses suffer from, improvements have been made in their manufacture. These improvements have evolved according to what we show below:

(A) The first lenses used in cameras were the simple uncorrected lens (No. 1, Figure 54), which is a combined lens consisting of a single piece of glass that is often crescent-shaped or convex on both sides. It suffers from all the aforementioned defects. In view of the defects that result when the rays pass near the circumference of the lens (such as spherical aberration, for example), and to correct the chromatic aberration, it was necessary to add another separate lens made of glass that differs in its properties slightly from the glass from which the first lens was made, in order to. Rays passing near the center with those passing near the periphery, and it is noted that the amount of dispersal of the rays by the second lens is sufficient for the required repair. Only the strength of these two lenses remains positive, so the rays passing through the two lenses gather together at one point. It also follows from the placement of this disparate lens that the two lenses overcome the defect of chromatic aberration. Thus, the first development ended, and the second lens was formed, which was called the single chromatic lens (No. 2, Figure 54), which largely got rid of the defects of spherical and chromatic aberrations.

(B) Since the single achromatic lens could not resist the two defects of the barrel and cushion distortion that result from placing the Diafragum in front or behind the lens, two identical groups of single achromatic lenses were prepared, and the Diafragm was placed between them to become. One set of lenses and in front of the other. Thus, it was possible to overcome the curvilinear distortion of straight lines, and so came the lens called Rapid Rectilinear, which overcame the curvature of those lines (No. 3, Figure 54).

(C) Then came the Anastigmat Lens (No. 4, Figure 54), which overcame the largest number of lens defects, including astigmatism. And we say that it overcame the largest number of defects of all defects, as it has not been made to date what we can call a complete lens completely free of optical defects. The Anastast lens consists of a group of lenses between grouped and separated made according to an accurate mathematical estimate and placed at different dimensions from each other, and the number of these lenses ranges between five and six pieces of glass, and they differ in their arrangement according to the purposes for which they were made to achieve them.

At the present time, factories tend to produce this last type of lens in micro-photocopiers. Since these lenses are equipped with a fast shutter, it was possible through them to obtain images that need to be recorded at a high speed with the use of a large aperture without fear of the defects that result from the use of the wide aperture of the diphragm. There is no doubt that the Anastast lens is the only lens that is suitable for any photography that requires accuracy.

Selection power

Resolving Power or Resolution is defined as the ability to move close points or fine lines so that they appear completely defined in the image and completely separated from each other.

The determination strength is measured by the number of lines (in millimeter) that are recorded on the layer by a test board (Fig. If we denote the thickness of the line with the symbol (x), then it is possible to estimate the limiting force (s.t) according to the following equation:
s. v = 1 / 2 h

As an explanation for this, we suppose photographing a test board with adjacent black lines (its shape), the thickness of each of which is equal to the distance between each line and the next. In order to estimate the power of determination numerically in this image, we measure the number of lines per millimeter in the negative image, so if we assume that the thickness of each line is equal to 1/100 of a millimeter,