US2121567A - Afocal opposed plane cylindrical anamorphosers - Google Patents

Description

v) P 3 350-420 SR r g 9 f??? Search 500m on 2 131.59? V/ June 21, 1938. H. s. NEWCOMER 2,121,557

AFOCAL OPPOSED PLANE CYLINDRICAL ANAMORPHOSERS Filed Dec. 7, 1936 s Sheefs-Sheet 1 i k w W v T 1 RF V Q l A INVENTOR BY HARRY SlDNY NE OMER WA ATTORNEY sea-ran liOOm INVENTOR HARRY SIDNEY NEZCOMER ATTORNEY 3 Sheets-Sheet 2 Filed Dec. 7. 1936 d w/ i 1;

3 FIG. 7 5| I5 l6 FIG. 8 3 l8 FIG. 9 5| H s NEWCOMER AFOCAL OPPOSED PLANE CYLINDRICAL ANAMORPHOSERS FlG IO June 21, 1938 is l m 0 O R h C r a 6 S June 1938. H. s. NEWCOMER AFOCAL OPPOSED PLANE CYLINDRICAL ANAMORPHOSERS Filed Dec. 7, 1936 :s Sheets-Sheet 3' Z wE mw m 29.505342 mI. owQEw m4 INVENTOR.

HARRY SIDNEY NE OMER ATTORNEY.

Patented June 21, 1938 UNITED STATES Search PATENT OFFICE AFOCAL OPPOSED PLANE CYLINDRIOAL ANAMORPHOSERS 10 Claims.

This invention relates to afocal opposed plane cylindrical anamorphosers. It is in part a continuation of my copending application for Letters Patent Serial No. 35,952 filed August 13, 1935 and in part a continuation of my copending application for Letters Patent Serial No. 85,647 filed June 22, 1936. It has for an object to provide an afocal anamorphoser particularly suited to imaging an object lying in one plane on to another plane at a finite and relatively short distance therefrom, whereby the object and image do not difier greatly in size an y-. ir'n a E'fiTHRbjecfl anam osed or given two different magnifications in two different meriians. e magnication in o an s d ermined by the associated spherical system and its conjugate focal distances; the distances to the object and image planes determine the spacial relationships.

Under such circumstances the usual type of afocal cylindrical anamorphoser such as for instance is described in my U. S. Patents'1,945,950 and 1,945,951 both dated Feb. 6, 1934 may be unsuitable because of lack of space, or because the focal lengths of the two cylindrical members, positive and negative, thereof would need to be too short for practical execution in the required openings, or because the one object plane or image plane is so near as to require too great a disproportion in the focal lengths of said members.

When an anamorphoser as described in said patents is placed between a spherical system and a conjugate image plane relatively near by, then in order to get appreciable anamorphosis and have at the same time sufiicient opening of the members of the cylindrical anamorphoser, it is necessary to so shorten their individual focal lengths as to require undue relative openings for the members and this holds even where the magnification due to the spherical system is as much as tenfold or more as in the projection of stock ticker and financial news with image plane distant ten times the principal focal distance of the spherical system or more.

One way to meet this situation is to have such an anamorphoser set for zero convergence effect on parallel pencils and hence be positioned between two spherical systems having their principal foci in the object and image planes. This therefore makes it desirable, in order to minimlze the separation of these two spherical systems, and thus avoid increasing their openings for even moderate angular fields, that the anamorphoser be as short as possible. Since the separation of the two members, the positive and negative cylindrical lenses, of such an anamorphoser is proportional to the focal lengths of the members and greater with increase in magnification or anamorphosis, it follows that decreasing the size of the cylindrical anamorphoser decreases the focal lengths of its two members and hence increases their relative openings and the difliculty of suitably correcting the members.

In this invention the anamorphoser is distinguished by its members having their condugate image planes on opposite sides of the anamorphoser and not on the same side as is the case just above, hence the term opposed plane anamorphoser. It is distinguished from other afocal cylindrical anamorphosers in one very important particular, namely relatively great magnification or anamorphosis is possible, even under such space restrictions, with relatively long focal lengths and close approximation of the two members. Magnification may be had by suitably spacing the members rather than by disproportion in focal lengths as is necessary with other anamorphosers.

The anamorphoser of this invention is also adapted and finds useful application to anamorphosed imaging of an object situated at a relatively great distance from the associated spherical system where conditions such as compactness of the apparatus as a whole make it desirable to place the anamorphoser behind rather than in front of the spherical system, that is between the ordinary photographic lens and the sensitive surface rather than to the object side of the former. Also because of the fact that it is behind the spherical system, that is because it may be placed between the spherical system and the nearer of the conjugate focal planes of the spherical system, it need not be dependent on change of position of the further conjugate focal plane for its magnification or the spacing of its two members. It finds particular application where the angular opening of the field of view is small and where one of the conditions above described obtains.

The above features, particularly the independence of the anamorphoser from the position of the further focal plane position of the associated spherical system, make it particularly applica ble to variable magnification (with respect to the spherical system) projection printing of anamorphosed images. This is possible with other well known cylindrical anamorphosers and prism anamorphosers only by the use therewith of variable focus spherical correction or projection Room lenses to compensate for the front projection distance.

In connection with the variable anamorphosis feature meantioned below, the anamorphoser of this invention can therefore also be used for variable magnification variable anamorphosis photographic or projection composition printing, and for margin justification as in the newspaper and type composition industry.

Another of the particular advantages of the anamorphoser of this invention is its adaptability, as just mentioned, to use as a variable magnification or variable anamorphosis cylindrical anamorphoser having relatively great magnification range.

Besides being suitable for producing relatively great anamorphosis it can be advantageously combined with certain other anamorphosers old in the art so as to still further increase the magnification without thereby further limiting the field or stop conditions.

The anamorphoser of this invention is also useful for increasing light flux in certain narrow gate optical systems as described in my copending application Serial No. 35,952 filed August 13, 1935.

Ceccarini, in U. S. Patent 1,938,808, and Rudolph in British Patent No. 8,512-A. D. 1898 have described anamorphosers comprising a spherical member placed between two cylindrical members, of moderate focal lengths. But in Ceccarinis device, although the astigmatism is less than in Rudolphs, the cylindrical members are relatively close to the two conjugate image planes and hence dust accumulating on them may greatly interfere with proper performance of the device. Also, being close to the image planes, the cylindrical members are comparatively far apart and cannot readily be placed in the same mount, which increases the difficulty of maintaining them with their axes precisely parallel. And in order that a cylindrical anamorphoser function with the highest possible resolution of the image, the axes of the cylinders must be maintained parallel to within a very small fraction of a minute of arc, not more than 1 or 2 seconds of are.

I have discovered that these objections to the use of cylindrical anamorphosers heretofore described can be overcome, and a slight increase in the focal length of the cylindrical members,

significantly greater in the case of the negative member, together with a decrease in their angular openings and consequent decrease in coma can be accomplished, by placing the spherical member to the outside of the cylindrical members and to the negative cylindrical member side of the system. The positive cylindrical member is then on the side of the object to be enlarged in one dimension, and both the positive and negative cylindrical members have the same conjugate focal points, points lying on opposite sides of the system. This new, arrangement therefore offers many advantages for this purpose over cylindrical anamorphosers previously described.

For a better understanding. of the invention, reference should be had to the accompanying drawings in which:

Fig. 1 shows a schematic representation of an optical system comprising an embodiment of the invention, and

Figs. 2 and 3 show component parts of Fig. 4 and detail, step by step the manner in which an afocal opposed plane cylindrical anamorphoser according to the invention and as shown in Figs. 1 and 5, 6, 7, 8, 9, and 10 functions, and

Figs. 5 and 6 show modifications changing the focal length of the associated spherical system, and

Fig. 7 shows in perspective an example of a corrected afocal opposed plane cylindrical anamorphoser according to the invention, and

Fig. 8 shows diagrammatically a modification of the invention to make the anamorphosis variable, and

Fig. 9 shows an anamorphoser and associated spherical system according to the invention in association with another anamorphoser to greatly increase the anamorphosis, and

Fig. 10 shows in perspective an afocal opposed plane cylindrical anamorphoser in an optical system comprising in addition two narrow gates with axes parallel to the axes of the cylinders, whereby light flux through the system may be increased by virtue of the action of the anamorphoser, and

Fig. 11 shows a type of corrected afocal op posed plane cylindrical anamorphoser together with certain diagrammatic relationships distinguishing all anamorphosers of the invention.

Fig. 2 shows an object (or image) plane I, a cylindrical lens 2 and a plane 3 on the opposite side thereof, conjugate to the plane I. A line 4 in the plane I is imaged by the positive cylindrical lens 2 in the line 5 of the plane 3. All lie perpendicular to a common optical axis 6. The arrow 1, at right angles to the line 4 in plane I and the arrow 8 at right angles to the line 5 in plane 3, indicate by their relative length the magnification in the active plane of the lens 2, in this instance drawn as in the ratio to 100. F-2 is a principal focal point of the lens 2.

Fig. 3 shows the next step in the construction of the anamorphoser of the invention. There is added a negative cylindrical lens 9 with axis parallel to that of the positive cylindrical lens 2 and of such focal length as to have the planes 3 and l, situated on the opposite sides thereof, its conjugate focal planes. Without making the focal length of the lens 9 much different from that of the lens 2 it is nevertheless possible to so construct and position it as to secure appreciable additional enlargement of the image in the plane 3, in this instance as 70.5 is to 109.5, so that the virtual line image of 5 formed by the lens 9 at 10 in the plane I is magnified 1.94 as compared with the line 4. This magnification is indicated by the relative lengths of the arrows I and II. For such magnification the focal lengths of the positive cylindrical lens 2 and the negative cylindrical lens 9 might be 44.44 mm. and 42.89 mm. respectively. F9 is a principal focal point of the lens 9.

The virtual anamorphosed image 10, II in the plane I, being in the plane of the object, is free of astigmatism and lies in that plane with respect to all meridians. In Fig. 4 this virtual image I0, I] is shown reimaged as a real image l2, l3 by a spherical lens I4 placed outside of and to the negative lens side of the anamorphoser 2, 9. That is the spherical system is placed to the opposite side of the anamorphoser with respect to the object plane I. The image plane l2, I3 need not be beyond the conjugate plane 3 but could be between it and the lens as at l3 Fig. 1, or it can be elsewhere.

Fig. 1 shows an axial section through an active plane of an afocal opposed plane cylindrical anamorphoser embodying the invention. 1 is the object (or image) which is reimaged at H by the anamorphoser comprising a positive cylindrical member 2 placed between the object and a negative cylindrical member 9, both with axes perpendicular to a common active plane, and both conjugate with respect to the object plane to a common conjugate plane located at 8 to the other side of the anamorphoser from the object plane I. At I4 is shown a positive spherical lens imaging H in l3. l3 may be anywhere along the axis 6 and may be a real image or a virtual image as for instance at l3" in Fig. 5 where the positive spherical lens I4" is of such focal length as to form an image of II at l3" to the left of the system.

As in Fig. 6 the spherical lens il' could also be a negative lens or other image forming system imaging elsewhere in the system as at l3' the anamorphosed image ll formed by the anamorphoser 2, 9.

The invention thus comprises in an optical system including two image planes and a, spherical lens imaging the one plane in the other the combination of an afocal anamorphoser comprising a positive and negative cylindrical member with axes parallel and situated between one image plane and the spherical lens, the negative cylindrical member being positioned nearest the spherical lens and both cylindrical members imaging the image plane situated to the positive cylindrical member side in a common conjugate lane on the opposite side of the negative cylindrical member from the said image plane.

It is of course not necessary that the associated system be a spherical system. It might be any optical system placed to the negative member side of the anamorphoser for which it was desired to create an anamorphosed image in the plane of the object. the object plane being situated to the other side of the anamorphoser from the optical system. Thus in its broadest aspect the invention comprises, in an optical system including an image plane, the combination of an afocal anamorphoser comprising a positive and a nega ive cylindrical member with axes parallel, the positive cylindrical member being positioned nearer the image plane and both members of such focal length and so positioned as to image this plane in a common conjugate plane situated to the opposite side of the negative cylindrical member from said plane.

As thus defined. no reference need be made to the associated optical system, as the specified relationship between the conjugate focal planes of the two members of the anamorphoser prevents the related system being placed so as to interfere with the operation of the anamorphoser. The latter thus operates to anamorphose and image an object in its own plane under conditions which restrict the possible dispositions or positionings of associated systems in part, whether spherical or otherwise. But as already pointed out they do not restrict the magnification or variation in magnification in the two meridians simultaneously obtainable with the spherical system.

I have discovered that it is advantageous for best results and that improved functioning of the opposed plane cylindrical anamorphoser is had when the negative and positive cylindrical members of the anamorphoser are substantially corrected for spherical aberration and color for their common conjugate focal planes (I and 3, Fig. 3),

The axial point of the associated spherical lens, as at P, Fig. 4, or indeed in practice, the axial point of the negative cylindrical member, may be the location of the stop. The negative member will then have a curved tangential image field as shown at 1 Fig. 1. I have discovered that a spherical correction of the positive cylindrical member 2 for a conjugate point in the stop P will substantially correct for coma and create suitable curvature of the tangential field of its image surface at I so that the two image surfaces, of the negative and positive cylindrical members will be substantially coincident in 1'. The virtual image II will then be substantially flat or can be made slightly concave toward the optical system to partially compensate for a likev curvature of the image field of the spherical lens.

Such a corrected afocal cylindrical anamorphoser is illustrated in Fig. '7 at 50 and if when they are drawn to four times the scale of the like dimensioned anamorphoser 2, S of Figure 1. l and 3 are the object (or image) plane and the conjugate plane thereto respectively with respect to both members. The positive cylindrical lens 50 is a cemented doublet substantially free from spherical aberration in both directions and for the conjugate focal point P (Fig. 4). It is also substantially achromatic d to g, in both directions and has all its surfaces concave toward the negative cylindrical lens so as to minimize the curvature of its tangential field and its other aberrations when the stop is at P. Actually, when the form is thus such as to be concave toward the negative lens, there is a slight amount of residual spherical aberration, being somewhat over-corrected for the principal focal point on the convex side and somewhat under-corrected for the principal focal point on the concave side, that is toward the side facing the negative member of the anamorphoser. These two corrections therefore balance out to an approximately perfect correction for the intermediate position of th conjugate focal points under the actual con itions of use. The crown glass faces the negative member and has both surfaces concave toward it. For a lens having a focal length of 44.44 mm. the radii and constants may be as follows:

R1= +1328!) mm.

thickness 0.443 mm. mi=1.60801 Abbe number 46:2 Barium flint R== .792 mm fhlcknegs ljsl mm, n =1fifi454 Abbe number 67.0 Phosphate crown R.1= 59.065

The negative cylindrical lens 5| is likewise substantially corrected for spherical aberration and color in both directions and its field flattened and coma substantially reduced. To accomplish this it may be given the following constants, the focal length being 42.89 mm.

R.= -12='-.337 mm.

thickness 1.400 mm. n4 =l.6080l Abbe number 46.2

Barium flint R 1 0.267 mm.

thickness 1.307 mm. 1u=1.56870 Abbe number 63.0 Phosphate crown R,-,= 4- 25.200 mm.

This negative cylindrical member is composed of such glasses and so formed as to be substantially free of spherical aberration in both directions, actually being somewhat under-corrected for the principal focal point on the least concave side, the side facing the positive member of the anamorphoser, and that of the longest conjugate focal distance, and somewhat less over-corrected to the other side, the side of the shorter conjugate focal distance. The result is an approximately perfect correction for the intermediate position of these two conjugate focal points proportionate, as to distance, to the under and over corrections for the principal focal points. The negative member has its flint glass facing the positive member and both surfaces thereof concave toward it. In both members the spherical correction includes color d to 9.

While I do not restrict myself to the use of the above glasses and curvatures in order to obtain suitable spherical, color and other corrections of the anamorphoser, I have discovered that the glasses and curvatures used in the construction of the above described embodiment of my invention offer certain specific and definite advantages and are for certain uses preferred. Other curvatures (and glasses) may be chosen in order to accomplish to a high degree certain specific corrections, as for instance that of correction of distortion of the pillow case type.

As set forth and described in my copending application Serial No. 35,952, it may be desirable to cross achromatize the two members of the anamorphoser, that is to have chromatism arising in one member corrected by an under-correction of the other member. Either one or both members may be individually under-achromatized but so chosen as to neutralize, the one, the chromatism of the other. Thus both may be simple cylinders of such dispersions that for each color the conjugate plane to the image plane with respect to the positive member is also for the negative member and for this color a conjugate plane with respect to the aforementioned image plane.

Thus in Fig. 6 the images of the arrow 1 for the different colors g and d, formed by the lens 2 might lie in the planes 8g and 8d, which if the lens 2 had a focal length of 44.44 mm. for d (as in the example) and were made of crown glass of index nd=1.5065'l and Abbe number or v=62 and if the conjugate plane 8d were 100 mm. from the lens 2, would then make the conjugate plane 8g 95.70 mm. from the lens 2. If now the lens 9 be of focal length 42.89 mm. for (I, then if its distance from 8d be 70.5 mm. the virtual image of 8d is in the plane of I and the virtual image of 8g can be brought into the plane of I provided the chromatism of the lens 9 is suitable, for instance as might be had by making it a simple lens of glass 114:1.6'727 and v=29.5. There is then however a certain chromatism of magnification introduced by the marked differences in conjugate foci of each member for the two colors. The color magnification difference (1 to g of this example is from 1.94 to 1.979.

For reasons of correction of spherical aberration it might be desirable, for instance, to overachromatize one of the members and correct the resulting chromatism by over-achromatization of the other member.

One of the advantages of the afocal opposed plane cylindrical anamorphoser according to my invention is its adaptability to providing wide variations in anamorphosis. Such variation can be obtained by moving the two cylindrical members, positive and negative, either toward or away from one another. If the two members are of the same strength their conjugate focal distances are equal but opposite and should remain so, the displacements therefore being equal and opposite.

If the two members are of unequal strength, as in the above example then the one of greater strength is moved the further and the other may be moved in either direction or not moved at all, depending on the displacement of the former and therefore the anamorphosis desired. By way of illustration the anamorphosis of 1.94 in the above example might, for instance, be decreased by a displacement of the positive member of 8.88 mm. so as to make the two conjugate foci of the positive lens both 88.88 mm., there being no magnification due to the positive member. In order to have the same conjugate foci, the negative member of the example would need to be displaced about 4 mm. toward the positive member and the total magnification (anamorphosis) would become about 1.46 instead of 1.94.

Displacement of the positive member 20 mm. to make its conjugate foci 100 mm. and mm. would require return of the negative member to its original position by which the total magnificatiOi; (anamorphosis) would be reduced to about 1.2

Displacement of both members still further from the object (or image) plane can be made according to the above principles with still further decrease in the anamorphosis. However the possibility of approaching continuously through small values to unit magnification or zero anamorphosis would depend upon the possibility of bringing the adjacent principal points of the positive and negative cylindrical members in contact, which in turn would depend upon their design.

The negative member of the anamorphoser need not, of course, be equal to or less than the positive member in focal length. It will be obvious from the principles set forth that the negative member might be of longer focal length. Suppose for instance that the focal lengths, and for simplicitys sake, the conjugate focal lengths in the above example be interchanged. Both members are then about 10 mm. nearer to the object (or image) plane and the magnification is the same, namely, 1.94. Displacement of the positive member to said mid position between the two planes, distance from the object (or image) plane 85.78 mm. instead of 70.5 mm., would entail an impossible setting of the negative member because there is then no position for the negative member in which it could have the same conjugate image planes. The negative member can however be moved toward the positive member as was done above for the positive member and with the same magnification change.

In Fig. 8 I show diagrammatically by means of arrows l5, l6 displacements of the positive and negative cylindrical members 50 and 5| respectively to produce decrease in anamorphosis. The double arrow l6 indicates the reversal in motion of the member 5| when the member 50 passes the mid position between the conjugate planes I and 3, said mid position being indicated by the shorter arrow I5. The longer arrow I5 indicates the displacement required to bring the negative member 5| back to its original position. If the plane I is presumed to be fixed then there is naturally some shift in the position of the plane 3 as the member 50 is shifted. The arrows I and I8 indicate the respective displacements (for the example) of the two members when the member 50 moves in the direction of the arrow H. The member 5| then moves about 3.1 mm. in the opposite direction and the magnification becomes 2.63 (conjugate plane other and both simultaneously toward or away from the object plane to compensate for change in the sum of the conjugate focal distances. There is also then an opportunity for a considerable range in magnification or anamorphosis commencing at the lower end very close to unit magnification (no anamorphosis), provided the two members are so constructed that their adjacent principal points can be brought close together.

It should be noted that one of the advantages of this variable magnification anamorphoser is that members spherically and chromatically corrected as described remain essentially corrected in their displaced positions and therefore a suitable correction may be given, as above, which holds with varying magnification. In Fig 8, 50 and 5! might be such corrected members as heretofore described. If there be cross achromatization of the anamorphoser as described above, wherein each member is a simple lens and the negative lens has the largest Abbe number, then achromatization only holds for one position or magnification of the anamorphoser. As the magnification approaches unity (zero anamorphosis), the Abbe numbers of such a cross achromatized anamorphoser should approach equality, and vice versa. Also then the corrections can be simpler and still provide good definition for the combination as a whole.

In Fig. 11 I show a corrected afocal opposed plane cylindrical anamorphoser according to the invention in which correction of the positive member is had by forming it as a double objective of two closely approximated single objectives of the general form of the positive member of my afocal objective as illustrated in my Patent 1,945,951, with the chromatic correction however centered, for best results, on that portion of the spectrum for which the objective is to be used. The outside faces of two such identical positive members are faced toward each other in such an assembly. This arrangement I have discovered offers certain specific advantages because it gives particularly good correction at relatively large openings for imagery of the one conjugate plane into the other and makes possible particularly good definition of a field of fair size.

Where it is desired to use the anamorphoser in variable anamorphosis composition printing on chloride paper using the violet region of the spectrum, then the positive member of the illustrative objective of the above patent, achromati'zed as it is for centering the correction on the h line, and except for a slight residual spherical aberration nevertheless so small as to probably be below the limits of tolerance, makes a suitable member of such a symmetrical double objective. It gives, along with a suitable negative member, such for instance as one made achromatic as above and similar in construction 'to that illustrated at 5!, Fig. '7, an anamorphoser having excellent definition over a relatively large and fiat field. When mounted so as to move the two members toward or away from each other it maintains the definition over a magnification range from about to over 400% when widely separated.

The residual spherical aberration of both the positive and negative double objectives of Fig. 11 could be removed, if it were desired, by decreasing the v difierence between the crown and fiint so as to permit shortening, in each case, of the radius of the cemented surface.

The following constants for the positive double objective corrected as above are taken from the Search Room above mentioned patent, applying a factor of 1.3.

r1=+198.64 mm.

In Fig. 11 the above double member is drawn at 50', 50". The strength of this double member is 15.42 diopters and its principal points H and H are 6.04 mm. inside the exterior surfaces. A similar objective, achromatically and spherically corrected d to g is obtained by changing both 1': and T5 to 32.70 mm. It could be used in association, either with a negative member of suitable focal length (depending upon the magnification required) like that illustrated at 5| Fig. '7, or it could be used in association with a double negative objective like that presently to be described but corrected for the region it to g.

The following are the constants for a spherically corrected negative double member 5|, 5!" achromatic in the violet in the region centering on h and having the same strength, 15.42 diopters, as the positive member. The principal points It and h are 7.94 -mm. inside the outer faces. The glasses and opening are the same as for the positive member.

ds=5.11 mm. Flint Ta 39.26 mm.

da=4.09 mm. Crown 1'9 =+133.73 mm.

interval 2.34 mm. Air 1'io=133.73 mm.

d1=4.09 mm. Crown rn=+ 39.26 mm.

da=5.11 mm. Flint This double negative objective has advantages similar to those set forth for the positive member just described. It is comparatively free of spherical aberration for a relatively large opening and also relatively free of aberrations along pencils at an angle to the axis. Both members so constructed have certain specific advantages for the imaging, as is here necessary, of one plane into another with nearly unit magnification or magnifications of that order. As with the positive member, achromatism d to g of this negative member, together with suitable spherical correction, can be had by changing both To and rm to 32.70 mm. or thereabouts. If desired the strengths of the two members can then be equalized again by slight changes in the spacing of the component doublets in each member.

In both the above double objectives, the two components need not be of the same strength. Where there is appreciable magnification to be accomplished, they might to advantage be of different strengths, the stronger being in each case on the side of the shorter conjugate focal distance for that member.

This anamorphoser of Fig. 11 gives good definition over magnification ranges from about to over 400%, depending upon the spacing.

Another way of visualizing certain essential features of the invention involving the relationships between the two cylindrical members, positive and negative, comprising the afocal opposed plane cylindrical anamorphoser of this invention is illustrated in Fig. 11 and will be understood by reference thereto, in which 50', 50" is the positive cylindrical member, 5|, 50" the negative cylindrical member, both members having all the axes of their elements lying in the same plane containing the axis 6 of the system. The drawing is foreshortened by brealnng it at each end between the anamorphoser and the axial conjugate points and 3'. At I Ishow the axial point of the object (or image) plane and at 3' the axial point of a plane conjugate thereto with respect to the positive member 50', 59". The rays 3| and 31, originating in the point I are deflected by the member 59', 50" to the positions 32 and 38 which if prolonged as 33 and 39 meet in the point 3'. The rays 32 and 38 are deflected by the member 5|, 5|" to the positions 34, 40 and appear to come (as indicated by the arrows) as if they were continuations of the rays 35, 4| originating in the point I". The afocal opposed plane anamorphoser of the invention is thus distinguished by comprising a positive and negative cylindrical member with axes parallel in which the two members are so spaced and so related and of such focal lengths as to each have the same pair of conjugate focal points exterior to the anamorphoser, one of which is on the positive member side and the other on the negative member side of the anamorphoser.

This differs then from the afocal anamorphoser of Rudolph in British Patent 8,512, those described by Chretien in the Patents 1,897,752, 1,829,633, 1,829,634, 1,962,892 and 2,006,233 and that described by Newcomer in his Patents 1,945,950 and 1,945,951, in that all these anamorphosers have the two members, positive and negative, so spaced and of such focal length as to each have the same pair of conJugate focal points exterior to the anamorphoser and both on the negative member side thereof. The present anamorphoser further differs from those of Ceccarini and Rudolph which have, as an essential feature, a spherical member placed between the two cylindrical members.

In this specification, as heretofore, the term afocal means having no convergence effect on pencils originating in a plane for which the anamorphoser is afocal or is adjusted or focused. In this specification, that is for the anamorphoser of this invention, said plane is the object plane, or plane passing through the conjugate focal point to the side of the positive member. This is therefore an object or image plane for a system in which the anamorphoser is used and the anamorphoser is by definition free of axial astigmatism for homocentric pencils originating in said plane.

Another advantage of the afocal opposed plane cylindrical anamorphoser of this invention is that it may be used in combination with other anamorphosers, as for instance in Fig. 9 with a prism anamorphoser 2| placed to the other side of the associated spherical system l9 where in the figure the other numerals have the same significance as heretofore. In Fig. 9, 2| is drawn as a three prism anamorphoser such as is described in my copendlng application 85,647 filed June 22, 1936. I9 and 20 are its associated spherical lenses, as described in said application, with principal foci respectively in the object (or image) plane I and in an image (or object plane) (not shown, but represented by l3, Fig. 1) and in which I is to be imaged, as at l3, Fig. 1, by the spherical lens combination I9, 20. The afocal opposed plane cylindrical anamorphoser 5|], 5| is shown, by way of example, adjusted, as in the previous example, for a high magnification (2.63) and thus the arrow H is 2.63 times as long as the small arrow 1 considered as an object. The arrow 1 is imaged by the positive cylindrical member 50 in the plane 3 to the opposite side of the negative cylindrical member 5|, and with magnification as shown at 8, and from there it is reimaged by the negative member 5| as the virtual image The prism anamorphoser 2| reimages H as a virtual image with magnification 1.94 (as constructed in this example) represented by the arrow 22. Actually, because of the interposition of the spherical lens |9, the image due to the anamorphoser 2| is real or vitual and situated at infinity. The arrow 22 indicates its apparent size when projected on the plane I. The total magnification or anamorphosis is thus 5.1. More could be had by either alterations in the focal lengths and/or in the positions of the cylindrical members 50 and 5|, or by increase in the anamorphosis due to the associated anamorphoser 2|, or by both. Thus for not too large a field this arrangement combining the anamorphoser of this invention with others permits good imagery and suitable stop conditions with relatively enormous anamorphosis, eight or ten times or more. Such values have not heretofore been reached with the image quality here obtainable.

In Fig. 10 there is shown at an object plane, and at 2 a positive cylindrical lens imaging the object plane I in the plane 3. At 9 there is a negative cylindrical lens with axis parallel to that of the positive cylindrical lens and to the axis of a narrow gate or slit 23 placed at the negative lens (shown placed against its exterior face). The negative lens 9 images the plane 3 back in the plane I as a virtual image ll, considerably larger, in a direction transverse to the gate than the original dimensions of The lines indicate the rays from the marginal portions of the object and image through the marginal portions of the positive lens and through the gate.

In a light flux system, in Fig. 10 might be a mirror whose dimensions are restricted, particularly the dimension perpendicular to the axes of the cylindrical lenses lay restricted when compared with what it is desired to be. The mirror is imaged by a cylindrical lens 2, whose axis is parallel to a slit 23, in a plane 3 spacially separated from the slit. At 9 there is placed close to the slit a negative cylindrical element with axis parallel to the slit and to the axis of the positive element 2. It is of such focal length that one conjugate image is in the plane 3 and the other in the plane of the mirror I so that the action of the two elements 2 and 9 together results in forming, at I, a unidimensionally enlarged image of the mirror. As a result of this device, that is this introduction of the second cylindrical element of negative power, the so-called convergence of light pencils passing through the slit is the same in character as if there were no cylindrical elements present. The anamorphoser is therefore in this sense afocal. That is the pencils traversing the slit appear to originate in a mirror occupying the position of the real mirror but having a length appreciably longer than the portion of the real mirror actually used. This apparent avg.-

. I uv increase in length of the mirror results in an increased light flux through the slit. In the azimuth under consideration, in spite of the introduction of the anamorphosing device to increase the light flux in this azimuth, the light source remains on the mirror and is not transferred to the slit as in arrangements of conventional design.

The foregoing descriptions are illustrative but are not intended as an exhaustive treatise on the possibilities of the invention nor in particular of the definitive solutions thereof.

I claim:

1. Means for forming a unidimensionallyenlarged virtual image, free of axial astigmatism, of an object in the plane of the object, comprising a positive and a negative cylindrical lens member spaced from each other and placed in front of the object plane, the cylindrical members having their generatrices all parallel, the positive member being positioned nearer the said ---object plane and at a distance therefrom greater than its back focal length thereby to image the said object plane in a conjugate plane situated to its opposite side, the negative member being positioned back of said conjugate plane and at a distance from the said object plane which is substantially greater than its back focal length and having back and front conjugate focal distances equal to the distances of the said object plane and the said conjugate plane respectively, thus reimaging the said conjugate plane in the said object plane, substantially as described.

2. In an optical system having two image planes and comprising a spherical lens imaging the one plane in the other, the combination of means for forming in one of the image planes a unidimensionally enlarged virtual image, free of axial astigmatism, of an object lying in said image plane, comprising a positive and a negative cylindrical lens member spaced from each other and placed in front of the said image plane and between it and the said spherical lens, the cylindrical members having their generatrices all parallel, the positive cylindrical member being positioned near the said image plane and at a distance therefrom greater than its back focal length thereby to image the said image plane in a conjugate plane situated to its opposite side, the negative cylindrical member being positioned back of said conjugate plane and at a distance from the said image plane which is substantially greater than its back focal length and having back and front conjugate focal distances equal to the distances of the said image plane and the said conjugate plane respectively, thus reimaging the said conjugate plane in the said image plane, substantially as described.

3. In an optical system, means for forming a unidimensionally enlarged virtual image of an object in the plane of the object as in claim 1 in which the positive and negative cylindrical members are each substantially chromatically and spherically corrected for both their principal focal points.

4. In an optical system, means for forming a unidimensionally enlarged virtual image of an object in the plane of the object as in claim 1 in which the positive member is somewhat over corrected for spherical aberration for the principal focal point on the side of the said object plane and somewhat undercorrected for the other principal focal point, thus tending to correct for -spherical aberration for the said object plane and the conjugate plane, the negative member being somewhat undercorrected for spherical aberration for the principal focal on the side facing the positive member and somewhat overcorrected for spherical aberration for the other principal focal point, thus tending to correct for spherical aberration for the said object plane and the conjugate plane, both members being substantially achromatized for said object and conjugate planes.

5. In an optical system, means for forming a unidimensionally enlarged virtual image of an object in the plane of the object as in claim 1 in which the positive cylindrical member is a cemented doublet with all its surfaces convex toward the said object plane and the negative cylindrical member is a cemented doublet with its exterior surfaces concave, that facing the positive cylindrical member being least concave and the cemented surface being concave toward the positive cylindrical member.

6. Means for forming a unidimensionally enlarged virtual image of an object in the plane of the object as in claim 1 in Which the positive member is somewhat overcorrected for spherical aberration for the principal focal point on the side of the said object plane and somewhat undercorrected for the other principal focal point, thus tending to correct for spherical aberration for the said object plane and the conjugate plane, the negative member being somewhat undercorrected for spherical aberration for the principal focal point on the side facing the positive member and somewhat overcorrected for spherical aberration for the other principal focal point, thus tending to correct for spherical aberration for the said object plane and the conjugate plane, both members being substantially achromatized for said object and conjugate planes, and each member being a cemented doublet comprising a flint and a crown glass, the flint glass being positioned nearer the said object plane.

'7. Means for forming a unidimensionally enlarged virtual image of an object in the plane of the object as in claim 1 in which the two members are adjustably positioned with respect to each other and the said object plane, thereby to provide variable enlargement in the one dimension. 5

8. Means for forming a unidimensionally enlarged virtual image of an object in the plane of the object as in claim 1 in which the positive and negative cylindrical members are simple cylinders, the negative member being composed of a glass of appreciably greater Abbe number than that of the positive member, thereby to produce cross achromatization of the two members.

9. Means for forming a unidimensionally enlarged virtual image, free of axial astigmatism, of an object in the plane of the object, comprising a positive and a negative cylindrical lens member spaced from each other and placed in front of the object plane, the two members having their generatrices all parallel, the positive member being positioned nearer the said object plane and with its corresponding principal point at a distance therefrom greater than but not appreciably more than twice as great as its focal length thereby to image the said object plane in a conjugate plane situated to its opposite side and at a distance from the corresponding principal point of the positive member not appreciably less than twice its focal length, the negative member being positioned back of said conjugate plane and at a distance from the said object plane which is substantially greater than its back focal length andhaving back and front focal distances an object in the plane of the object, as in claim 9, equal to the distances of the said object plane in which each member comprises a double objecand the said conjugate plane respectively thus tive composed of two components which are reimaging thesaid conjugate plane in the said doublets of such curvatures, thicknesses, and

5 object plane, substantially as described. glasses as to make each component a spherically 5 10. Means for forming a unidimensionally encorrected achromatic doublet. larged virtual image, free of axial astigmatism, of HARRY SIDNEY NEWCOMER.

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