FR2726372A1 - OBJECTIVE FOR THE FINAL REPRESENTATION OF AN OBJECT - Google Patents

Abstract

An objective for the representation of an object on a receiver with - a first group of lenses of negative refractive force, arranged on the side of the large conjugation, - a second group of lenses of positive refractive force, arranged on the side of the small conjugation, and - a diaphragm between the two groups of lenses, characterized in that to adjust the scale of representation, the objective is movable in the direction of its optical axis, in that the second group of lenses is constituted by two partial groups of positive refractive force, the partial group on the side of the small conjugation being movable for focusing together with the receiver in the direction of the optical axis, in that the first group of lenses is formed by at least two lenses, and in that the central point of the rays of the face situated in relation to the diaphragm, of the first group of lenses and the central point of the rays of the last fac e on the side of the small conjugation of the lens lie on the side of the small conjugation.

Description

OBJECTIVE FOR THE FINAL REPRESENTATION OF AN OBJECT

  The invention relates to an objective for the final representation of an object on a receiver with - a first group of refractive force lenses

  negative, placed on the side of the great conjugal

guée,

  a second group of refractive force lenses

  positive side, arranged on the side of the small conjugate bond, and

  - a diaphragm between the two groups of lenses.

  This type of objective is for example used in the medical technique for the analysis or representation of

  X-ray pictures. To maintain the irradiation dose

  Within an as small as possible range, an electron multiplier is placed downstream of the fluorescent screen or X-ray fluoroscopic screen. This produces a very clear image, although

  on the fluorescent screen. The image produced by multiplication

  electron is transmitted by a transmission objective.

  to the respective receiver which, depending on the use case, may be a photographic film, an electronic tube or

  a CCD chip or charge coupled chip.

  The explanations above show that the transmission lens must not only have a large aperture to transmit as much light as possible

  but it must also be free from artificial vignetting

  sky. In addition, the transmission objective must be characterized by high resolution, strong

  contrast and very low image distortion.

  So far, as transmission objectives, essentially so-called "tandem" systems are used. The first objective forms the object, that is to say for example the image produced by the multiplier of electrons "towards infinity", the second objective then forms the image "from infinity" on the receiver. Based on this mode

  of construction, it can be achieved by combining objec-

  variable focal distance, scales of representation,

different.

  This conception of the transmission objective, however, has the disadvantage of requiring a specific objective for each scale of representation. Moreover, the

  transmission objectives have an important overall length

  aunt who can only be partially compensated by a

complex construction mode.

  The object of the invention is to propose a transmission objective whose scale of representation can at least vary within the zone where this is usual or necessary in the field of radiography. In addition, the objective must, for a small overall length, have a large opening and a very good quality of representation. In particular, the transmission objective must be free from artificial vignetting and have a practically constant irradiation intensity in the field

  of the image and very low distortion.

  This object is achieved according to the invention in that for

  adjust the scale of representation, the objective is shifted

  in the direction of its optical axis, in that the second lens group is constituted by two partial groups of positive refractive force, the partial group on the side of the small conjugation being movable for focusing together with the receiver in the direction of the optical axis, in that the first group of lenses is constituted by at least two lenses, and in that the central point of the radii of the face located with respect to the diaphragm, of the first group of lenses and the central point rays of the last side on the side of the small conjugation of the lens are on the side

  of the small conjugation. As the sub-paragraphs

  claims, additional embodiments have

  have been envisaged: the dispersion of the lenses of the first group of lenses is alternately "high, low"; the partial group located on the side of the small conjugation has a mastic element and at least one positive refractive force lens; - the dispersion of the lenses of this partial group is "low, low ... high, low"; the partial group situated on the side of the small conjugation is constituted by at least one positive refractive force lens; - the distance between the two partial groups of

  group of lenses arranged on the side of the small conju-

  Gaison is shortened when the representation scale decreases;

  - the object placed on the side of the great conjugal

  sound is a screen; the screen is part of an X-ray image amplifier assembly; the receiver arranged on the side of the small conjugation is a magnetic recorder; - the receiver arranged on the side of the small

conjugation is a movie.

  According to the invention, it has been recognized that the problem posed can be solved by starting from a lens having a first group of lenses with negative retractive force, which is arranged on the side of the large conjugation, a second group of lenses of positive retractive force, which is

  arranged on the side of the small conjugation, and a diaph-

  rage between the two groups of lenses. (the term conjugate bond is used here as the equivalent of

focal distance).

  For the adjustment of the representation scale, the lens is movable in the direction of its optical axis. The second group of lenses consists of two partial groups, of positive refractive force, with the partial group located on the side of the small conjugation

  movable for focusing together with the receiver

  in the direction of the optical axis. It is preferable here that the distance between the two partial groups of

  group of lenses arranged on the side of the small conju-

  Gaison is shortened with the reduction of the representation scale. In particular, the distance between the two partial groups of the lens group disposed on the side of the small conjugation can be shortened during a greater decrease from large to small conjugation

(claim 6)

  In addition, according to the invention, the first group of lenses consists of at least two lenses. Moreover, the center point of the face located with respect to the diaphragm of the first lens group and the central point of the rays of the last face on the side of the small conjugation of the lens are on the side of the lens.

the small conjugation.

  By the features set out in the

  1, we obtain a goal to equip most modern X-ray amplifiers but also most existing X-ray amplifiers.

  The objective according to the invention may, however, also

  suitable for many other applications, such as inspection of specimens or samples, monitor scanning, etc. Applications are indicated

in claims 7 to 10.

  Other embodiments of the invention make

the subject matter of claim 2.

  According to claim 2, the dispersion of the lenses

  the first group of lenses is alternately high, low. "With this arrangement, an excellent chromatic correction is obtained which is further improved by the features of claim 3, wherein the partial group on the side of the large conjugation comprises a mastic element and at least one positive refractive force lens This is further improved when the dispersion of the lenses of this partial group is "low,

  bass ... high, low "(claim 4).

  The objective according to the invention can therefore be of relatively simple manufacture. In particular, according to the claim, the partial group located on the side of the small conjugation is constituted by at least one

  positive refractive force lens.

  The invention will be described below by way of example without limitation of the general inventive idea with reference to the exemplary embodiments and to the drawing, examples which are expressly referred to with regard to all the details of the invention. invention that have not been explained anymore in

detail in the description.

  The single figure in the drawing shows a section of

  lens of an objective according to the invention.

  In the table, numerical data, that is,

  say the rays Ri of faces i, the lens thicknesses or the distances di between the face i and the face (I + 1) as well as the refractive indices ni and the abbreviations VI VI for the glass materials used for the line e have been rounded each time. With the distances that are changed when moving the objective o for the partial group located on the side of the small conjugation for focusing together with the receiver, the space values are each times indicated for the largest and the most Small scale.

Board

Ex. 1 2 3 4 5 R1

D1 14.0 3.6 10.0 0.1 0.1

  nl 1.51 1.51 1.51 1.51 1.51 vl 61 61 61 61 61 R2 d2 1.2 / 58.9 0.2 / 50.9 5.4 / 20.6 8.1 / 21 , 2.4 / 52.1

R3 12.03 21.89 11.94 15.19 99.51

  d3 3.5 10.0 3.5 3.78 1.4 n3 1.86 1.81 1.81 1.81 1.52 v3 24 25 25 25 64

  R4 -77.47 -10.06 -29.46 -18.07 37.29

  d4 1.5 1.0 1.24 2.0 4.2 n4 1.63 1.69 1.57 1.57

V4 47 54 43 43

R5 2.78 4.66 3.99 4.04 13.74

  d5 6.4 10.85 5.4 5.4 5.9 n5 1.81 v5 25 R6 diaphragm diaphragm diaphragm diaphragm -29.96 d6 1.5 1.5 2.5 2.5 2.6 n6 1 57 v6 43

R7 -17.36 -23.66 -16.11 -20.60 3.99

  d7 1,5 1,2 3,5 6,1 5,4 n7 1,86 1,86 1,86 1,86 v7 24 24 24 24 R8 10,93 16,24 17,97 21,53 diaphragm d8 4 , 5 3,6 4,5 4,5 2,5 n8 1,61 1,62 1,60 1,60 v8 65 60 65 65

  R9 -8.59 -10.83 -10.02 -10.67 -17.38

  d9 0.5 0.1 0.5 0.5 3.7 n9 1.86 v9 24

R10 25.14 26.58 35.31 28.80 20.52

  dlO 4.5 4.8 4.5 4.5 4.5 nlO 1.69 1.69 1.53 1.53 1.60 vlO 54 54 77 77 65 R11 -18.03 -21.64 -15, 60 -21.12 -10, 43 dll 6.9 / 2.0 15.8 / 8.8 0.5 1.5 0.5

R12 15.70 10.01 27.15 19.86 46.51

  d12 4.0 3.5 3.5 3.5 4.5 n12 1.52 1.79 1.54 1.53 1.53 v12 64 47 47 77 77

R13 84.30 23.74 157.0 61.42 -15.94

d13 7.5 5.0 6.6 / 4.2 6.1 / 4.0 1.0

R14 10.58 10.47 32.28

  d14 0.8 0.8 4.8 3.3 3.5 n14 1.52 1.52 1.52 1.52 1.53 v14 64 64 57 57 77

R15 14.54 18.62 -875.55

d15 1.0 1.0 5.2 5.5 6.9 / 1.6

R16 11.91

  dl16 0.8 0.8 4.9 n16 1.52 1.52 1.52 v16 64 64 57

R17 35.53

  d17 1.0 1.0 6.3 R18 d18 0.8 n18 1.52 v18 64 R19 d19 1.0 R20

Claims (10)

  1. Objective intended for the definitive representation of an object on a receiver, with - a first group of lenses of negative refractive force, arranged on the side of the large conjugation,   a second group of refractive force lenses   positive side, arranged on the side of the small conjugation, and - a diaphragm between the two groups of lenses,   characterized in that to adjust the scale of representation   the lens is displaceable in the direction of its optical axis, in that the second lens group is constituted by two partial groups of positive refractive force, the partial group located on the side of the small   conjugation being movable for the joint focus   with the receiver in the direction of the optical axis,   in that the first group of lenses is con-   staggered by at least two lenses, and in that the center point of the radii of the diaphragm-facing face of the first lens group and the center point of the rays of the last face on the side of the small conjugation of the objective   lie on the side of the small conjugation.   2. Objective according to claim 1, characterized in that the dispersion of the lenses of the first   lens group is alternatively "high, low".   3. Objective according to claim 1 or 2, characterized in that the partial group located on the side of the small conjugation has a putty element and the   less a positive refractive force lens.   4. Objective according to claim 3, characterized in that the dispersion of the lenses of this   Partial group is "low, low ... high, low".   5. Objective according to one of claims 1 to 4,   characterized in that the partial group on the side of the small conjugation is at least one   positive refractive force lens.   6. Objective according to one of claims 1 to 5,   characterized in that the distance between the two partial groups of the lens group arranged on the side of the small conjugation is shortened during a decrease of the scale of representation.   7. Objective according to one of claims 1 to 6,   characterized in that the object disposed on the side of the big conjugation is a screen.   8. Objective according to claim 7, characterized in that the screen is part of a set   X-ray image amplifier.   9. Objective according to one of claims 1 to 8,   characterized in that the receiver arranged on the side of the   small conjugation is a magnetic recorder.   10. Objective according to one of claims 1 to 8,   characterized in that the receiver arranged on the side of the little conjugation is a movie.