Two objectives were assigned, the first running E.
Abbe succeeded in computing microscope objectives free from error of the axis point and satisfying the sine condition for several colours, which therefore, according to his definition, were " aplanatic for several colours "; such systems he termed " apochromatic."
The subsequent history of the development of the art of manufacturing glass disks for telescopic objectives will be found in the article Glass: § Optical.
Five objectives were laid down, and exploitation was to be carried out beyond the final one to Welsh Ridge (N.
This road system bears plain marks of having been made at different times, and with different objectives, but we have no evidence that any one part was abandoned when any other was built.
Between these extreme examples stands the ordinary photographic objective: the portrait objective is corrected more with regard to aperture; objectives for groups more with regard to the field of view.
(3) Telescope objectives have usually not very large apertures, and small fields of view; they should, however, possess zones as small as possible, and be built in the simplest manner.
This artifice is specially adopted in objectives for astronomical photography ("pure actinic achromatism").
On this account the lines D and G' are united for ordinary photographic objectives; the optical as well as the actinic image is chromatically inferior, but both lie in the same place; and consequently the best correction lies in F (this is known as the " actinic correction " or " freedom from chemical focus ").
This Is Produced In The Same Amount, But In The Opposite Sense, By The Oculars, Which Are Used With These Objectives (" Compensating Oculars "), So That It Is Eliminated In The Image Of The Whole Microscope.
The Best Telescope Objectives, And Photographic Objectives Intended For Three Colour Work, Are Also Apochromatic, Even If They Do Not Possess Quite The Same Quality Of Correction As Microscope Objectives Do.
For strong objectives there is, however, only one optical tube length in which it is possible to obtain a good image by means of wide pencils, any alteration of the tube length involving a considerable spoiling of the image.
A series of objectives with short focal lengths are available, which permit the placing of a liquid between the cover-slip and the front lens of the objective; such lenses are known as " immersion systems "; objectives bounded on both sides by air are called " dry systems."
- Weak and medium microscope objectives work like photographic objectives in episcopic or diascopic projection; in the microscope, however, the projected image is not intercepted on a screen, but p?
Soc., 1882, p. 463) we have the following table for the limits of the magnification numbers, for various microscope objectives, µ = o ooi mm.: A=nsinu.
For this reason the objectives have been called monochromats, as they have only been corrected for light of one wave-length.
Very large apertures occur in strong microscope objectives, and hence the two conditions are not compatible.
By experiment Abbe proved that old, good microscope objectives, which by mere testing had become so corrected that they produced usable images, were not only free from spherical aberrations, but also fulfilled the sine-condition, and were therefore really aplanatic systems.
By using these glasses and employing minerals with special optical properties, it is possible to correct objectives so that three colours can be combined, leaving only a quite slight tertiary spectrum, and removing the spherical aberration for two colours.
And C. Chevalier, at first after the designs of Selligue, produced objectives, consisting of several achromatic systems arranged one above the other.
Selligue had no particular comprehension of the problem, for his achromatic single systems were simply telescope objectives corrected for an infinitely distant point, and were placed so that the same surface was turned towards the object in the microscope objective as in the telescope objective; although contrary to the telescope, the distance of the object in the microscope objective is small in proportion to the distance of the image.
It would have been more correct to have employed these objectives in a reverse position.
This system will always be aplanatic. These objectives permitted a much larger aperture than a simple achromatic system.
Although such systems have been made recently for special purposes, this construction was abandoned, and a more complex one adopted, which also made the production of better objectives possible; this is the principle of the compensation of the aberrations produced in the different parts of the objective.
33),and constructed objectives with an aperture of 135°.
Objectives with definite undercorrection can however only produce really good images with glass covers of a specified thickness.
For this reason Amici constructed objectives of a similar aperture and focus for different thicknesses of glass covers.
Since, however, the difference of chromatic magnification cannot be overcome in powerful objectives, this error is still further increased by the eyepiece.
As powerful achromatic objectives show differences of chromatic magnification in the same way as apochromats, compensation eyepieces can be used in combination with these objectives.
With very powerful objectives these methods are insufficient; and a condenser is fitted below the stage plate.
Hence a condenser, for lighting with very oblique cones, must have about the same aperture as the objective, and therefore be of very wide aperture; they therefore closely resemble microscope objectives in construction.
Especially powerful achromatic condensers are really only magnified microscope objectives, with the difference that they are not corrected for the thickness of the cover slip, but for the thickness of the glass on which the object is placed.
For exceptionally accurate work microscope objectives are sometimes used as condenser systems. When using immersion objectives, an immersion condenser must also be used if rays of extreme obliquity are wanted, for, in consequence of the total reflections, rays can only come from the upper plane surface of the condenser, which have not a larger inclination to the axis than about 41°, varying according to the refractive index of the glass.
Beck, which can be conveniently fitted in and used for objectives with different focal lengths.
To examine objects with objectives of high power and low free object distance, the apparatus for side-illumination is not sufficient, and a so-called vertical illuminator is used.
For slight magnifications rough adjustment is sufficient, but with objectives of a focus below 4 in., a fine adjustment is wanted.
It doesn't fit with their alleged party objectives or any tactics they've ever employed.
- Siemens's Continuous Tank of Dollond's invention of achromatic telescope objectives in 1 757, a demand first arose for optical glass, the industry was unable to furnish suitable material.
The price, however, rapidly increases with the total bulk of perfect glass required in one piece, so that large disks of glass suitable for telescope objectives of wide aperture, or blocks for large prisms, become exceedingly costly.
Was unable to attain all its objectives and the 38th Div.
In line, despite difficulties in assembling its forces, reached its first objectives by 9 A.M., but the 6th Division was held up at Holnon, and was unable to maintain itself in Fresnoy, while the 1st Div.
A series of partial offensives were therefore undertaken on the succeeding days, on both wings of the army, but with little real result; neither corps could succeed in attaining the final objectives of the first day's attack or clear the enemy entirely from the advanced defences of the Hindenburg line.
Up to this line four successive objectives were assigned; from there onwards the second phase of the advance was to carry the assailants to the line of the Scheldt canal and the Sensee.
At the same hour on the 29th the infantry again went forward, the objectives being to complete the capture of the Marcoing line and the seizure of the Scheldt canal bridges W.
Attained their objectives - the line of the canal south of Ramillies and the road between that place and Cuvillers.
On the N., attacking in the afternoon, secured and held its objectives and thus eased the situation on that flank.
Passed through to continue the advance and carried the line to the outskirts of Marcoing, thus attaining all the corps' objectives for the day.
Was in possession of its objectives everywhere.
Corps was to round off its success on the right by clearing the Thorigny area on the near bank of the canal, and occupying the ground on its front as far as the Masnieres - Beaurevoir line; the Australians were to secure the remainder of the first day's objectives in its sector between Bellicourt and Vendhuille, while the III.
Corps on the right had heavy fighting, and after attaining their final objectives about 10:30 A.M.
The Australian Corps also successfully attained its first objectives, though not till later in the evening, so that the exploitation of their success on this day proved out of the question.
With the first instrument of this kind, having objectives of 1 5 inch aperture, he measured the brightness of 4260 stars, including all stars down to the 6th magnitude between the North Pole and - 30° declination.
The platform carries the two slits, the collimator and camera objectives and the prism-train.
In spite of the improvements in the manufacture of optical glass practically the same crown and flint glasses as used by John Dollond in 1758 for achromatic objectives are still used for all the largest of the modern refracting telescopes.
The foreign policy of Venice was likewise mainly dictated by commercial motives, the chief objectives being commercial privilege in the Byzantine empire and in the Frankish states in the East, domination of the Adriatic, 1 H.
Trans., 1830, 3, p. 1) is fulfilled in all systems which are symmetrical with respect to their diaphragm (briefly named " symmetrical or holosymmetrical objectives "), or which consist of two like, but different-sized, components, placed from the diaphragm in the ratio of their size, and presenting the same curvature to it (hemisymmetrical objectives); in these systems tan w'/ tan w= 1.
This combined condition is exactly fulfilled by holosymmetrical objectives reproducing with the scale 1, and by hemisymmetrical, if the scale of reproduction be equal to the ratio of the sizes of the two components.
It is important for telescope objectives, since their apertures are so small as to permit higher orders to be neglected.
(2) The condition for freedom from coma in the third order is also of importance for telescope objectives; it is known as " Fraunhofer's condition."
The Bulgarian scheme of operations, necessarily offensive, suffered from the weakness of having two objectives - the Ovche Polye and Salonika - and being based on two main lines of communication diverging towards the rear - Kyustendil and Seres - Drama.
Weak and strong microscope objectives act differently.
With these microscopes, which are not stereoscopic, objectives of any power can be used.
The examination of the objectives can only be attempted when the different faults of the objective are known.