Focal-plane Sentence Examples

What is seen through the eye-piece in any case is the same as would be depicted upon a screen in the focal plane.

By the principle of energy the illumination over the entire focal plane must be equal to that over the diffracting area; and thus, in accordance with the suppositions by which (3) was obtained, its value when integrated from E= co to = -1-x, and from n = - oo to n = -1-oo should be equal to ab.

If the aperture be increased, not only is the total brightness over the focal plane increased with it, but there is also a concentration of the diffraction pattern.

In these expressions we are to replace p by ks/f, or rather, since the diffraction pattern is symmetrical, by kr/f, where r is the distance of any point in the focal plane from the centre of the system.

The limitation of power is introduced as in all optical instruments, by the finiteness of the length of a wave of light which causes the image of an indefinitely narrow slit to spread out over a finite width in the focal plane of the observing telescope.

In its simplest form it consists of a direct-vision spectroscope, having an adjustable slit (called "camera slit"), instead of an eyepiece, in the focal plane of the observing telescope.

This forms an image of the solar spectrum in its focal plane on the camera slit (1).

A cross-hair, in the focal plane of an eyepiece, is then moved horizontally until it coincides with the line in question.

For example, it is possible, with one thick lens in air, to achromatize the position of a focal plane of the magnitude of the focal length.

These rays come to a focus at a point F lying in the focal plane of the telescope.

All the rays through a given point in the first principal focal plane of the anterior system of lenses traverse the plate as a parallel beam and reunite at the corresponding point of the second focal plane of the posterior system, each in its passage being divided into two by the plate having a given relative retardation.

A web in the focal plane of telescope marks the point in the field at which the bands are to be made to disappear; this is effected by turning the polarizer by means of a rack and pinion worked by an arm from the observer's end of the instrument.

This is the case if the image O'OI' lies in the front focal plane of the eyepiece.

The size of the imago on the focal plane is always equal to its actual size, and is independent of the distance of the object from the plane focused for.

To ensure the telecentric transmission, the diaphragm in the back focus of the objective may be replaced by a diaphragm in the front focal plane of the condenser, supposing that uniformly illuminated objects are being dealt with; for in this case all the principal rays in the object-space are transmitted parallel to the axis.

The plane in the object conjugate to the focal plane of the eye-piece is the plane FIG.

As the pencils used in the representations are of wide aperture on the object-side, only such points as are proportionately very near the focal plane can produce such small dispersion circles on the plane focused for, that they, so far as the objectiveand eyepiece-magnification permit, appear as points to the eye.

If the obliquity of illumination be so great that the principal maximum passes through the outermost edge of the objective, while a spectrum of 1st order passes the opposite edge, so that in the back focal plane the diffraction phenomenon shown in fig.

If this object be viewed by the objective, so that at least the diffraction spectra of 1st order pass the finer divisions, then the corresponding diffraction phenomenon in the back focal plane of the objective has the appearance shown in fig.

If one cuts out by a diaphragm in the back focal plane of the objective all diffraction spectra except the principal maximum, one sees in the image a field divided into two halves, which show with different clearness, but no banding.

The cutting off of the chief maximum can be effected by a suitable diaphragm in the back focal plane of the objective.

With the .orthogonal arrangement for illuminating and observing the beam of light traverses an extremely fine slit through a well-corrected system, whose optic axis is perpendicular to the axis of the microscope; the system reduces the dimensions of the beam to about 2 to 4 in the focal plane of the objective.

In the lower focal plane of the eyepiece, at the spot where the real image which the objective forms of the object arises, a glass plate is introduced on which are two fine cross lines or even two very thin threads.

Strong systems produce in the proximity of their back focal plane an image of the scale, which can be inspected with a weak auxiliary microscope, and the length of the visible part of the graduation determined.

If one focuses an auxiliary microscope, carried in the inner tube, on the image situated in the back focal plane of the objective of a distant object, and then on the dust particles lying on a slide pressed against the end of the outer tube, the displacement of the auxiliary microscope gives the distance of the back focal plane of the objective from the end of the outer tube.

To determine the position of the anterior focal plane of the eyepiece, the eyepiece is placed on the stage with the eye-lens downwards.

This gives the distance of the anterior focal plane of the eyepiece from the bottom edge of the setting of the eyepiece and consequently also of the edge of the eyepiece carried by the upper end of the tube.

The objective to be examined is placed on the stage, and in the manner just shown, the distance of the focal plane from the edge of the fittings or to the surface plane of the front lens is determined.

If the size of the image of a known interval of the objective micrometer is determined by an ordinary scale, and the distance of the image from the focal plane of the objective belonging to it is measured, then the focal length can be calculated from the ratio y/y'=fl', in which y is the size of the object, y' that of the image, and xi' the distance of the image from the focal plane belonging to it.

A cross can be seen in the back focal plane.

The shutter release is a metal focal plane shutter with vertical operation.

Because these cameras have a built-in focal-plane shutter, there is no need for a shutter in the lens.