Abstract
An optical device having an optical axis. The device includes at least one surface with at least two meridians, at least one portion of which forms, seen face-on, at least one spiral segment the central point of which is on the optical axis. Each spiral segment defining meridians of different optical powers. The focus obtained extends over a tubular region.
Claims
1. An optical device having an optical axis, comprising at least one surface with at least two meridians, at least one portion of which forms, seen face-on, at least one spiral segment the central point of which is on the optical axis, each spiral segment defining meridians of different optical powers, in order that the focus obtained extend over a tubular region.
2. The optical device as claimed in claim 1, the one or more spiral segments being generated from a toric surface having a first meridian curved with a first non-zero curvature and a second meridian curved with a second curvature strictly greater than the first curvature, the second meridian being perpendicular to the first meridian.
3. The optical device as claimed in claim 2, the one or more spiral segments being generated from first and second toric surfaces, the first toric surface having a first meridian curved with a first non-zero curvature about an axis of revolution of a first torus and a second meridian curved with a second curvature strictly greater than the first curvature, the second meridian being perpendicular to the first meridian, the second toric surface having a first meridian curved with a first non-zero curvature about an axis of revolution of a second torus and a second meridian curved with a second curvature strictly greater than the first curvature and perpendicular to the first meridian of the second toric surface, the first and second toric surfaces each comprising a plurality of azimuthal angular sectors arranged about the optical axis, the first meridian of the first toric surface and the first meridian of the second toric surface have azimuthal orientations separated by a non-zero angle about the optical axis, the spiral segments defining first and second optical-power meridians resulting from the first meridian of the first toric surface and from the first meridian of the second toric surface.
4. The optical device as claimed in claim 3, an azimuthal angular sector of the first toric surface and an azimuthal angular sector of the second toric surface being adjacent via a spiral-segment border.
5. The optical device as claimed in claim 3, the first toric surface and second toric surface each comprising two diametrically opposed azimuthal angular sectors.
6. The optical device as claimed in claim 5, each angular sector of the first toric surface being adjacent to the two angular sectors of the second toric surface.
7. The optical device as claimed in claim 3, the angle between the azimuthal orientations of the first meridian of the first toric surface, and the first meridian of the second toric surface is comprised between 60° and 90°.
8. The optical device as claimed in claim 3, wherein the first curvature of the first toric surface is equal to the first curvature of the second toric surface.
9. The optical device as claimed in claim 3, wherein the second curvature of the first toric surface is equal to the second curvature of the second toric surface.
10. The optical device as claimed in claim 1, the radius of a spiral segment being related, in polar coordinates, to the angle of the spiral by a linear law, a quadratic law or a logarithmic law.
11. The optical device as claimed in claim 1, furthermore comprising a spherical surface centered on the optical axis.
12. The optical device as claimed in claim 1, forming an optical lens the front face of which is the surface with at least one spiral segment.
13. The use of an optical device as claimed in claim 1, to correct vision and/or to concentrate luminous power and/or to form an image.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] Other advantages and features of the invention will become more clearly apparent on reading the detailed but non-limiting description of examples of implementation of the invention, which is given by way of illustration with reference to the following figures, in which:
[0055] FIG. 1 is a schematic representation of the distribution of a parallel light beam having passed through an optical lens of toric surface;
[0056] FIG. 2 is a schematic face-on view of a first embodiment of the optical lens of tubular focus;
[0057] FIG. 3 is a schematic face-on view of a multifocal optical lens with two toric surfaces in axial opposition;
[0058] FIG. 4 is a schematic perspective view of the multifocal optical lens of FIG. 3;
[0059] FIG. 5 is a schematic view of the distribution of a parallel light beam having passed through the optical lens of FIGS. 3 and 4;
[0060] FIG. 6 is a schematic face-on view of an embodiment of a multifocal optical lens with two toric surfaces in axial opposition;
[0061] FIG. 7 is a schematic face-on view of an embodiment of the lens of tubular focus according to the invention generated from the geometry of the lens of FIG. 6;
[0062] FIG. 8 is a schematic face-on view of another embodiment of a multifocal optical lens with two toric surfaces in axial opposition;
[0063] FIG. 9 is a schematic face-on view of another embodiment of the lens of tubular focus according to the invention generated from the geometry of the lens of FIG. 8;
[0064] FIG. 10 is a schematic profile view of the distribution of a parallel light beam having passed through an optical lens according to the invention and by comparison a spherical optical lens according to the prior art;
[0065] FIG. 11 is a schematic perspective view of a beam of parallel light rays having passed through an optical lens according to the invention with logarithmic spirals, FIG. 11 showing the tubular region of focus of the light ray;
[0066] FIG. 12 is an enlarged view of the tube of focus of the beam of light rays of FIG. 11 and by comparison the focal region of a lens with toric surfaces in axial opposition as illustrated in FIG. 6;
[0067] FIG. 13 is a face-on view of a variant embodiment of a lens of tubular focus according to the invention comprising a spherical central portion and a spiral peripheral portion;
[0068] FIG. 14 is a face-on view of another variant embodiment of a lens of tubular focus according to the invention comprising two toric surfaces and a junction portion therebetween that is spiraled.
DETAILED DESCRIPTION
[0069] FIG. 1, which relates to the prior art, has already been commented on in the preamble. It is therefore not described in further detail below.
[0070] The following figures show a number of examples of optical lenses according to the invention, comprising surfaces with more than two meridians with at least one spiral segment generating a focus that extends over a tubular region.
[0071] As may be seen from the various figures, a spiralization segment may be produced in various ways, for example according to a linear law, a quadratic law or a substantially logarithmic law. These various laws may also be combined in the same lens, for example with a logarithmic law in a first annular segment of the lens and a quadratic or linear law in a second annular segment of the lens surrounding the first annular segment.
[0072] A given optical device may comprise a plurality of spiral segments.
[0073] FIG. 2 shows an optical lens 800 of tubular focus according to a first embodiment of the invention. The representation used indicates with contrast the separation perpendicular to the plane of the figure: darker means further from the reader and lighter means closer to the reader. The optical lens 800 is generated by spiralization of a toric surface of the lens as illustrated in FIG. 1. The central point is 806. Thus, the geometry of the surface 801 has a spiral the central point 806 of which is on the optical axis. In polar coordinates, the angle of the spiral increases with radial distance from the optical axis. In particular, the first meridian 802 having the first curvature in addition has a shape spiraled about the optical axis. In addition, lines 803 that have the second curvature and that would be parallel to the second meridian in the toric lens of FIG. 1 here have different azimuthal orientations, the orientation of the lines changing with distance from the optical axis because of the spiralization.
[0074] In fact, in order to achieve the invention, after having analyzed the shortcomings of prior-art multifocal lenses, the inventor sought to stretch the focal region out along the optical axis.
[0075] Starting with multifocal lenses with two concentric toric surfaces, he then thought of putting them in axial opposition.
[0076] FIGS. 3 and 4 show a face-on and perspective view of such a multifocal optical lens 100. The multifocal optical lens 100 comprises a first toric surface 102 and a second toric surface 104 that encircles the first surface 102 concentrically.
[0077] Thus, if the lens 100 is viewed axially along the optical axis A-A, the first surface 102 corresponds to a first optical region and the second surface 104 corresponds to a second optical region that is concentric with the first surface 102.
[0078] The first toric surface 102 has a first meridian 102.sub.1 curved with a first curvature and a second meridian 102.sub.2 curved with a second curvature and perpendicular to the first meridian 102.sub.1. Likewise, the second surface 104 has a first meridian 104.sub.1 curved with a first curvature and a second meridian 104.sub.2 curved with a second curvature and perpendicular to the first meridian 104.sub.1. In particular, on each of the first and second surfaces 102, 104, the second curvature is greater than the first curvature.
[0079] The periphery of each of the first and second surfaces 102, 104 is a circular section.
[0080] The first meridian 102.sub.1 of the first surface 102 is perpendicular to the first meridian 104.sub.1 of the first surface 104.
[0081] The first curvature of the first surface 102 may be different from or equal to the first curvature of the second surface 104. Likewise, the second curvature of the first surface 102 may be different from or equal to the second curvature of the second surface 104.
[0082] Thus, the lens 100 comprises two concentric tori having different meridian axes, which are especially in opposition or in a counter-axial format, i.e. such that there is an angle of 90° between the two tori.
[0083] FIG. 5 illustrates the distribution of light having passed through the multifocal optical lens 100 under a parallel illumination in an example in which the first curvature of the first surface is equal to the first curvature of the second surface and in which the second curvature of the first surface is equal to the second curvature of the second surface. Light that passes through the first meridian 102.sub.1 of the first surface 102 converges at a first focal distance 106, thereby forming a first section 1081 parallel to the first meridian 1021, and light that passes through the second meridian 1022 of the first surface 102 converges at a second focal distance 110, forming a second section 1082 parallel to the second meridian 1022.
[0084] In addition, light that passes through the first meridian 104.sub.1 of the second surface 104 converges at the first focal distance 106, thereby forming a first section 112.sub.1 parallel to the first meridian 104.sub.1 and light that passes through the second meridian 104.sub.2 of the second surface 104 converges at the second focal distance 110, thereby forming a second section 1122 parallel to the second meridian 104.sub.2.
[0085] Thus, with such a lens 100, the focal region obtained is longer than the focal regions of prior-art multifocal lenses. This elongated focal region is dependent on the toricity of the surfaces 102, 104.
[0086] Observing that this focal region was not sufficiently concentrated, the inventor then thought of carrying out the spiralization of the surfaces, in order to obtain a focus concentrated in a tubular region and thereby to make it possible to obtain a focus over a longer distance along the optical axis.
[0087] FIGS. 6 and 7 illustrate an embodiment of an optical lens 200 of tubular focus and with a double toric surface, in axial opposition and in spiraled axial opposition, respectively.
[0088] The optical lens 200 of FIG. 6 comprises a first toric surface 202 having a first meridian 202.sub.1 that is curved with a first curvature about an axis of revolution of a first torus, and a second meridian (represented by an arc 202.sub.2 parallel to the second meridian) that is curved with a second curvature greater than the first curvature and perpendicular to the first meridian 202.sub.1. The optical lens 200 also comprises a second toric surface 204 that is juxtaposed with the first toric surface 202 and that has a first meridian 204.sub.1 that is curved with a first curvature about an axis of revolution of a second torus, and a second meridian (represented by an arc 204.sub.2 parallel to the second meridian) that is curved with a second curvature and perpendicular to the first meridian 2041. Seen face-on, i.e. in projection onto a plane of projection perpendicular to an optical axis of the lens 200 passing through its center 206, the first toric surface 202 corresponds to two azimuthal angular sectors 208.sub.2 and 208.sub.4 that are diametrically opposed and that meet at their apexes, which are turned toward the center 206 of the optical lens 200. In the same way, the second toric surface 204 corresponds to two azimuthal angular sectors 208.sub.1 and 208.sub.3 that are diametrically opposed and that meet at their apexes, which are turned toward the center 206. Each azimuthal angular sector 208.sub.2 and 208.sub.4 of the first toric surface 202 is adjacent to the two azimuthal angular sectors 208.sub.1 and 208.sub.3 of the second toric surface 204. The angular sectors 208 are bounded by the intersections of the first toric surface 202 and of the second toric surface 204, which are lines of intersection in space between two cylindrical-section rings the axes of revolution of which are perpendicular. These intersection lines have been represented by the borders 210.sub.1, 210.sub.2, 210.sub.3 and 210.sub.4 between the azimuthal angular sectors 208.sub.1, 208.sub.2, 208.sub.3 and 208.sub.4. In space, each of the borders 210.sub.1, 210.sub.2, 210.sub.3 and 210.sub.4 is arranged set back in the direction of the optical axis with respect to the first meridians 2021 and 2041.
[0089] FIG. 7 shows an optical lens 200 generated by a spiralization of the toric lens surfaces in FIG. 6. Thus, the first meridian 202.sub.1 of the first toric surface 202 and the first meridian 204.sub.1 of the second toric surface 204 is a spiral segment the central point 206 of which is on the optical axis of the optical lens 200. Likewise, each of the borders 210.sub.1, 210.sub.2, 210.sub.3 and 210.sub.4 is a spiral segment the central point 206 of which is on the optical axis of the optical lens 200.
[0090] The spiralization may be produced in various ways, for example according to a linear law, a quadratic law or a substantially logarithmic law. For the application of a logarithmic law, a simplification must be made in proximity to the center 206 of the lens, where the spiral angle would be mathematically divergent.
[0091] In the example shown in FIG. 7, the increasing angle reaches 45° at the periphery 25 of the optical lens 200. This angle could have another value, for example comprised between 30° and 720°, and in particular equal to 60°. The periphery 25 of the optical lens 200 here has a circular shape. This shape may be other than circular.
[0092] FIGS. 8 and 9 illustrate an embodiment of an optical lens 400 of tubular focus and with a double toric surface, in axial opposition and in spiraled axial opposition, respectively.
[0093] The optical lens 400 of tubular focus of FIG. 8 is designed similarly to the optical lens 200 of FIG. 6, but with three separate azimuthal sectors 401, 402, and 403 instead of four azimuthal sectors. Each azimuthal sector 401, 402, 403 has a toric surface segment, with respective first meridians 401.sub.1, 402.sub.1, 403.sub.1 that are oriented in various azimuthal directions, at 120° to each other in the symmetrical case such as shown. The second meridians are not shown here but are in each and every case perpendicular to the respective first meridians. The azimuthal sectors 401, 402, 403 are bounded by borders 405.
[0094] FIG. 9 illustrates a lens 400 of tubular focus generated from the lens surface in FIG. 8. Here, the spiral segments respect a quadratic spiralization law: the spiral angle is proportional to the square of the radial distance from the center 406 on the optical axis. Each of the borders 405 and each of the prime meridians 401.sub.1, 402.sub.1, 403.sub.1 has the same spiral geometry. In the example shown, the spiral angle reaches 360° at the periphery of the optical lens 400, i.e. one complete revolution. A second complete revolution could be made for a lens of larger size, i.e. an angle of 720° or more.
[0095] By way of numerical example, an optical lens 400 of tubular focus of FIG. 9 has been implemented with a front face with four identical toric branches, the parameters of which are as follows: [0096] first curvature of the toric surface: focal distance equal to 17.4 cm [0097] second curvature of the toric surface: focal distance equal to 14 cm [0098] the foci are spaced apart by 1.4 diopters [0099] shape of the spiral: logarithmic to the golden ratio [0100] angle of the spiral: 720° [0101] lens diameter: 10 mm [0102] other geometric parameters: the rear face is spherical with a radius of curvature of 7.8 mm. The thickness at the center of the lens 400 is equal to 0.5 mm.
[0103] Generally, an optical lens of tubular focus according to the invention may be designed similarly to one of the illustrated optical lenses 200, 400, 800 using any number of toric surfaces each occupying one azimuthal angular sector. Thus, the number of toric branches distributed about the optical axis in the spiral surface may be even (for example 2 branches in the optical lens 800, 4 branches in the optical lens 200) or uneven (for example 3 branches in the optical lens 400). Other numbers of branches are possible, for example 5, 6, 7 or more.
[0104] Moreover, the borders between the adjacent toric surfaces may be abrupt borders or graded borders. For example, the local curvature may be interpolated in the vicinity of the borders to provide gentle regions of transition between adjacent toric surfaces and thus limit extreme slopes.
[0105] The tubular focus obtained according to the invention is shown in FIG. 10 by comparison between a spherical optical lens 1301 according to the prior art and an optical lens of tubular focus according to the invention 1302, each of these two lenses 1301, 1302 being designed for a correction of vision. In FIG. 10, a parallel illumination is incident on the lenses 1301 and 1302, Z designating a region of sharpness perceived by the human eye that lies on either side of the object focal point of the lenses. As may be very clearly seen from FIG. 10, the lens 1302 with the spirals allows an elongation of the region of sharpness Z bounded by an imaginary right cylinder to be obtained. Thus, the spiralization of the various optical powers allows a tubular focus of the light rays to be obtained. In other words, if in a prior-art spherical lens 1301 one of the two dioptric interfaces is replaced by the spiraled toric surface 1302 according to the present invention, this has the effect of lengthening the focal region. The stigmatism region is then no longer a point, but a focus tube.
[0106] The inventor has performed an optical ray-tracing computation for a parallel illumination. FIG. 11 shows a lens 400 like that of FIG. 9, on the side of the object focal point. The focus region XV has been shown enlarged in the upper portion of FIG. 12.
[0107] FIG. 12 also shows the focal distances D1 and D2 corresponding to the first curvature and to the second curvature of the initial toric surface, respectively. On the right of FIG. 12, the line 1501 shows the size of the focal spot at D1 and the line 1502 shows the size of the focal spot at D2.
[0108] By comparison, the lower portion of FIG. 12 shows the same elements for an astigmatic lens in axial opposition as in FIG. 6, having the same curvatures as the initial ones of FIG. 11: the line 1511 shows the size of the focal spot at D1 and the line 1512 shows the size of the focal spot at D2.
[0109] It may clearly be seen from FIG. 12, that the spiralization of a lens according to the invention has the effect of compressing the focal spot between D1 and D2 substantially into the form of an imaginary right cylinder.
[0110] Other variants and advantages of the invention may be realized without however departing from the scope of the invention.
[0111] If in the examples illustrated, the spiral segments were produced so as to extend right across the optical surface of the lens, it is possible to envisage carrying out the spiralization only over one portion.
[0112] FIG. 13 thus illustrates a variant according to which the optical lens 300 comprises a spherical surface 302 arranged at the center of the optical surface of the lens 300, the spiral segments being produced only on the periphery of the optical surface.
[0113] FIG. 14 illustrates a variant according to which an optical lens 100 with two concentric toric surfaces 102, 104 has a junction portion 114 that is spiraled according to the invention.
[0114] The invention is not limited to the examples that have just been described; it is in particular possible to combine features of the examples illustrated within variants that are not illustrated.
