Anamorphic Lens Assembly

Abstract

A lens assembly according to the present disclosure includes an anamorphic lens component and a main lens component. The anamorphic lens component includes a first cylindrical lens element, a second cylindrical lens element, and a first spherical lens element disposed between the first and second cylindrical lens elements and translatable along an optical axis of the anamorphic lens assembly relative to the first and second cylindrical lens elements. Optical properties of the anamorphic lens component are adjustable as the first spherical lens element translates along the optical axis such that as an object moves from an infinity focus toward the lens assembly, the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element combine to produce a first astigmatism opposite to a second astigmatism produced in the image plane by the main lens component.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 396,566, filed August 9, 2022. The entire contents of the priority application are incorporated herein by reference as if fully set forth. [Background technology]

[0002] Anamorphic format is a cinematography technique that shoots widescreen images onto standard 35mm film or other visual recording media with a non-widescreen native aspect ratio. It also refers to a projection format in which a distorted image is stretched by an anamorphic projection lens to recreate the original aspect ratio on a viewing screen. Anamorphic lenses typically include a spherical primary lens and an anamorphic attachment (or integrated lens element) that performs the anamorphization. Because the anamorphic element operates at an infinite focal length, it has little or no effect on the focus of the primary lens to which it is attached, yet it still anamorphizes (distorts) the optical field. The distortion introduced by the camera must be corrected when the film is projected; therefore, a separate lens is used in the projection booth to return the image to its correct ratio and restore normal geometry. The image is not manipulated in any way in the dimension perpendicular to the anamorphized dimension.

[0003] Typically, anamorphic lenses capture (or project) a wider horizontal field of view than would normally be possible with a spherical lens to create a widescreen display. Anamorphic lenses do this by optically distorting the image horizontally during capture, which is then reversed during presentation. This method of widescreen image capture allows up to twice the width of the imager to be captured by distorting the image before recording and then later undistorting that compressed image, either during post-production or exhibition.

[0004] Conventional anamorphic lenses optically compress a wider angle of view for standard imager sizes by distorting the image proportions and compressing the image horizontally. An alternative approach that achieves much the same result is to stretch the image vertically. In either case, this horizontally squeezed (or vertically stretched) image is then undistorted to the widescreen aspect ratio through a corresponding anamorphic lens on the projector or through digital correction of the distorted image.

[0005] Anamorphic lens assemblies typically include a spherical primary lens plus an anamorphic attachment (often an integrated multiple cylindrical lens assembly) called an anamorphic (squeezing) attachment. The optical power of this attachment is typically zero on the vertical axis, acting like a flat piece of glass, and 0.5x on the horizontal axis, reducing the effective focal length of the spherical lens by half horizontally. Most anamorphic systems operate at this 0.5x compressive (squeezing) optical power to capture the image, resulting in a 2x magnification when presenting the unsqueezed image, but other compression ratios are available, as well as the vertical magnification techniques mentioned above. All of this generally means that a 50mm anamorphic lens has the vertical field of view of a 50mm spherical lens, but the equivalent horizontal field of view of a 25mm spherical lens. [Brief explanation of the drawings]

[0006] Various embodiments according to the present disclosure are described with reference to the drawings. [Figure 1A] FIG. 1 is a schematic diagram illustrating an anamorphic lens assembly according to some embodiments. [Figure 1B] FIG. 1 is a schematic diagram illustrating an anamorphic lens assembly according to some embodiments. [Figure 2A] 1C are schematic diagrams illustrating the convergence of light rays through the anamorphic lens assemblies of FIGS. 1A and 1B, respectively. [Figure 2B] 1C are schematic diagrams illustrating the convergence of light rays through the anamorphic lens assemblies of FIGS. 1A and 1B, respectively. [Figure 3] 10 is a graph illustrating two exemplary polynomial relationships between the rotation angle of a focus ring and the position of a first spherical lens element in an anamorphic lens assembly according to some embodiments. [Figure 4A] 1C is a schematic diagram along the y-axis showing the general operation of the anamorphic lens assembly of FIGS. 1A and 1B using paraxial optics. FIG. [Figure 4B] 1C is a schematic diagram along the y-axis showing the general operation of the anamorphic lens assembly of FIGS. 1A and 1B using paraxial optics. FIG. [Figure 4C] FIG. 1C is a schematic diagram showing the general operation of the anamorphic lens assembly of FIGS. 1A and 1B, viewed along the x-axis using paraxial optics and such that the cylindrical lens has no refractive power. [Figure 4D] FIG. 1C is a schematic diagram showing the general operation of the anamorphic lens assembly of FIGS. 1A and 1B, viewed along the x-axis using paraxial optics and such that the cylindrical lens has no refractive power. [Figure 5A] FIG. 1 is a schematic diagram illustrating another anamorphic lens assembly according to some embodiments. [Figure 5B] FIG. 1 is a schematic diagram illustrating another anamorphic lens assembly according to some embodiments. [Figure 6A] FIG. 1 is a schematic diagram illustrating another anamorphic lens assembly according to some embodiments. [Figure 6B] FIG. 1 is a schematic diagram illustrating another anamorphic lens assembly according to some embodiments. [Figure 7A] FIG. 1 is a schematic diagram illustrating another anamorphic lens assembly according to some embodiments. [Figure 7B] FIG. 1 is a schematic diagram illustrating another anamorphic lens assembly according to some embodiments. [Figure 8A]FIG. 1 is a schematic diagram illustrating another anamorphic lens assembly according to some embodiments. [Figure 8B] FIG. 1 is a schematic diagram illustrating another anamorphic lens assembly according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present disclosure relates to an anamorphic lens assembly. Traditionally, anamorphic lenses have different focal lengths along the horizontal and vertical axes due to the cylindrical lens that performs the anamorphization. These different focal lengths in the vertical direction result in astigmatism. An astigmatic lens is one in which light rays propagating through the lens have different foci (points where the light rays converge) in two perpendicular planes. For example, if an astigmatic lens is used to form an image of a cross, the vertical and horizontal lines of the cross will be sharply focused at two different distances.

[0008] Previous solutions to the problem of astigmatism in anamorphic lenses have several drawbacks. For example, previous solutions focused on adding cylindrical lenses to correct astigmatism, resulting in bulky, complex, and expensive lens assemblies. These solutions also produced undesirable artifacts, such as the anamorphic mumps effect at close focus (e.g., less than 10 feet from the object). Due to practical optics, in traditional anamorphic systems (whether cylindrical, prismatic, or mirror-based), the anamorphic squeeze is not uniform across the image field. This variation results in some areas of the film image appearing more stretched than others. In the case of an actor's face, when centered on the screen, the face appears as if the actor has the mumps, hence the name of the phenomenon.

[0009] Some of the present embodiments solve the above-mentioned problems by providing an anamorphic lens assembly having a first cylindrical lens element, a second cylindrical lens element, and a spherical lens element translatable along the optical axis of the anamorphic lens assembly between the first and second cylindrical lens elements. These embodiments use the movable spherical lens element to correct the above-mentioned astigmatism problem. These embodiments have a less complex structure than previous anamorphic lens assemblies, which advantageously reduces the cost of producing an anamorphic lens assembly according to the present embodiments as well as its bulk. And, while previous solutions have attempted to keep the anamorphic ratio constant as the distance between the camera and the object changes, some of the present embodiments allow the anamorphic ratio to vary within a small range, such as less than 2% in some instances. This change of such a small magnitude is imperceptible to the human eye, and as a result, embodiments in which the change in anamorphic ratio is below the 2% threshold still advantageously do not produce a noticeable change in the anamorphic ratio as the distance between the camera and the object changes. In alternative embodiments, the anamorphic ratio may vary within a somewhat larger range, such as, in some instances, less than 5%, or less than 4%, or less than 3%. In some embodiments, the anamorphic ratio variation with focus can be tailored to match the characteristics of a given anamorphic lens, as desired.

[0010] 1A and 1B show an anamorphic lens assembly 100 according to some embodiments. The anamorphic lens assembly 100 includes an anamorphic lens component 102 and a main lens component 104. In some embodiments, the anamorphic lens component 102 and the main lens component 104 may be configured as modules that are attachable to and detachable from other components of a camera system, including an image plane 106. In other embodiments, the anamorphic lens component 102 and the main lens component 104 may be configured as separate modules that are attachable to and detachable from each other and from other components of a camera system.

[0011] 1A , the anamorphic lens component 102 may include a first housing 108 that forms an exterior of the anamorphic lens component 102. Similarly, the main lens component 104 may include a second housing 110 that forms an exterior of the main lens component 104. In some embodiments, the first housing 108 and the second housing 110 may be sections of an overall housing for the anamorphic lens assembly 100. In the illustrated embodiment, only a portion of the first housing 108 is shown, and it should be understood that the first housing 108 at least partially surrounds and holds all of the lens elements of the anamorphic lens component 102.

[0012] In Figure 1A, the anamorphic lens assembly 100 is shown in an infinity focus configuration, and in Figure 1B, the anamorphic lens assembly 100 is shown in a near focus configuration. Referring to Figure 1A, the anamorphic lens component 102 includes a first cylindrical lens element 112, a second cylindrical lens element 114, and a first spherical lens element 116 disposed between the first cylindrical lens element 112 and the second cylindrical lens element 114. The relative positions of the first and second cylindrical lens elements 112, 114 are fixed along an optical axis 118 of the anamorphic lens assembly 100, and the first spherical lens element 116 is translatable along the optical axis 118 relative to the first and second cylindrical lens elements 112, 114. In some embodiments, the fixed distance between the first cylindrical lens element 112 and the second cylindrical lens element 114, combined with the ability of the first spherical lens element 116 to translate along the optical axis 118 between the first cylindrical lens element 112 and the second cylindrical lens element 114, can advantageously allow the spacing between the first spherical lens element 116 and the first cylindrical lens element 112 and the second cylindrical lens element 114, respectively, to be adjustable. This feature contributes to several advantageous optical properties of the present embodiment, as described further below.

[0013] In some embodiments, the first cylindrical lens element 112 has a first radius of curvature along a first axis, and the second cylindrical lens element 114 has a second radius of curvature along the first axis, the first axis being perpendicular to the optical axis 118. For example, in some embodiments, the first and second cylindrical lens elements 112, 114 have an arcuate shape with a concave or convex portion on at least one side such that, in the horizontal direction (e.g., along the x-axis 120), one or both of the first and second cylindrical lens elements 112, 114 increase or decrease the beam diameter due to the refractive power provided by the concave or convex arcuate shape, while in the vertical direction (e.g., along the y-axis), neither the first nor the second cylindrical lens element 112, 114 has any refractive power, or has negligible refractive power, or the first and second cylindrical lens elements 112, 114 have equal and opposite refractive powers such that their combined refractive power is zero. In the illustrated embodiment, the first cylindrical lens element 112 has negative refractive power in the horizontal direction, and the second cylindrical lens element 114 has positive refractive power in the horizontal direction. However, in alternative embodiments, the first and second cylindrical lens elements 112, 114 may have any combination of refractive powers, including negative, positive, and / or zero.

[0014] In some embodiments, the combined optical power of the first spherical lens element 116 and the first and second cylindrical lens elements 112, 114 (the lenses of the anamorphic lens component 102) is zero in the vertical direction and 0.5x in the horizontal direction. However, in other embodiments, the optical power of the anamorphic lens component 102 in the horizontal direction may be any other value, such as 0.75x, or 0.56x, or 0.33x, or 0.25x, or any other value. In yet another embodiment, the optical power of the anamorphic lens component 102 is zero in the horizontal direction and 2x (or 1.5x, or 1.8x, or 3x, or 4x, or any other value) in the vertical direction. The optical power of the anamorphic lens component 102 provides the desired amount of squeezing or stretching (anamorphization) along the desired axis to achieve a specified anamorphic format.

[0015] 1A and 1B, the first spherical lens element 116, the first cylindrical lens element 112, and the second cylindrical lens element 114 are each represented as a singlet. However, this embodiment is merely an example. In alternative embodiments, any of the lens elements 112, 114, 116 may comprise multiple lenses (e.g., a lens group), such as a lens pair (doublet). For example, in some embodiments, the first spherical lens element 116 may comprise a singlet, and the first and second cylindrical lens elements 112, 114 may comprise doublets. As another example, in some embodiments, the first spherical lens element 116 may comprise a doublet, and the first and second cylindrical lens elements 112, 114 may comprise singlets.

[0016] 1A , the primary lens component 104 is disposed on a side of the second cylindrical lens element 114 opposite the first spherical lens element 116 and includes one or more second spherical lens elements 122. The second spherical lens elements 122 may be configured to provide primary imaging, for example, by changing the focus of an image formed by the primary lens component 104. Accordingly, the one or more second spherical lens elements 122 may be translatable along the optical axis 118 relative to the first and second cylindrical lens elements 112, 114, as described further below. In some embodiments, the second spherical lens elements 122 may be configured to change other optical properties of the image, such as image softness, image size, or to correct for image blur or aberrations, or to change other optical properties as desired. Although the second spherical lens elements 122 are described herein as being spherical, in some embodiments, one or more of the second spherical lens elements 122 may be aspherical, as desired.

[0017] 1A , as described above, the relative positions of the first and second cylindrical lens elements 112, 114 are fixed along the optical axis 118 of the anamorphic lens component 102. However, the first spherical lens element 116 is translatable along the optical axis 118 relative to the first and second cylindrical lens elements 112, 114. For example, FIG. 1A shows the anamorphic lens assembly 100 in an infinity focus configuration where the first spherical lens element 116 is positioned at the limit of its movement toward the first cylindrical lens element 112, and FIG. 1B shows the anamorphic lens assembly 100 in a near focus configuration where the first spherical lens element 116 is positioned at the limit of its movement toward the second cylindrical lens element 114.

[0018] In some embodiments, movement of the first spherical lens element 116 may be controlled by a focus adjustment member 124 (e.g., a focus ring) disposed about the main lens component 104. In embodiments in which the focus adjustment member 124 is a focus ring, the focus ring 124 may be rotatable about the main lens component 104. The focus ring 124 may be mechanically coupled to one or more additional focus adjustment members (not shown), which may be mechanically coupled to the first spherical lens element 116, such that rotation of the focus ring 124 adjusts the focus of the main lens component 104 and simultaneously induces translation of the first spherical lens element 116 along the optical axis 118 between the first cylindrical lens element 112 and the second cylindrical lens element 114. The focus adjustment member 124 and the one or more additional focus adjustment members mechanically coupling the focus adjustment member 124 to the first spherical lens element 116 may together comprise a translation mechanism for the first spherical lens element 116. Thus, for example, when the focus ring 124 is rotated in a first rotational direction about the primary lens component 104, the primary lens component 104 may be adjusted away from the infinity focus configuration ( FIG. 1A ) and toward the near focus configuration ( FIG. 1B ), while the first spherical lens element 116 moves away from the first cylindrical lens element 112 and toward the second cylindrical lens element 114. Conversely, when the focus ring 124 is rotated in a second rotational direction about the primary lens component 104, the primary lens component 104 may be adjusted away from the near focus configuration ( FIG. 1B ) and toward the infinity focus configuration ( FIG. 1A ), while the first spherical lens element 116 moves away from the second cylindrical lens element 114 and toward the first cylindrical lens element 112. In some embodiments, the focus of the primary lens component 104 may be controlled by a threaded focus adjustment mechanism or may be controlled by a cam mechanism. For example, as described below, in some embodiments, the relative movement between first spherical lens element 116 and main lens component 104 may be non-linear. In such embodiments, one of first spherical lens element 116 or main lens component 104 may move linearly with a screw thread, and the other may move via a cam mechanism.

[0019] 1A , an anamorphic lens assembly 100 according to some embodiments is configured to generate a focused image of an object 126 (on the object side 128 of the anamorphic lens assembly 100) at an image plane 106 of a camera (on the image side 130 of the anamorphic lens assembly 100). In some embodiments, the camera may be a digital camera, and the image plane 106 may comprise an image sensor having an imaging area for receiving an image from the anamorphic lens assembly 100. In other embodiments, the camera may be a film camera, and the image plane 106 may comprise a film having an imaging area for receiving an image from the anamorphic lens assembly 100 on the film. In some embodiments, the anamorphic lens assembly 100 may be configured as a module that is attachable to and detachable from the camera, while in other embodiments, the anamorphic lens assembly 100 may be integrated within the camera. In some embodiments, the camera may be a cinema camera configured to generate images for presentation by a cinema projector. In some embodiments, the main lens component 104 may have an internal focus mechanism (not shown) that allows one or more lenses within the main lens component 104 to move to achieve focus.

[0020] In some embodiments, as the first spherical lens element 116 moves along the optical axis 118 relative to the first and second cylindrical lens elements 112, 114, the spacing between the second cylindrical lens element 114 and the main lens component 104 changes. For example, with reference to both Figures 1A and 1B, as the first spherical lens element 116 moves away from the infinity focus configuration of Figure 1A (away from the first cylindrical lens element 112) and toward the near focus configuration of Figure 1B (toward the second cylindrical lens element 114), the spacing between the second cylindrical lens element 114 and the main lens component 104 decreases. This relative movement between the first spherical lens element 116 and the main lens component 104 maintains image focus at the image plane 106, and in some embodiments, the image plane 106 may move relative to the main lens component 104 as the anamorphic lens assembly 100 transitions between the infinity focus configuration and the near focus configuration. In an alternative embodiment, in which the first spherical lens element 116 has positive refractive power, the direction of relative movement between the second cylindrical lens element 114 and the main lens component 104 may be reversed such that the spacing between the second cylindrical lens element 114 and the main lens component 104 increases as the first spherical lens element 116 moves away from the infinity focus configuration toward the near focus configuration.

[0021] In some embodiments, the relative movement between first spherical lens element 116 and focus ring 124, and the relative movement between main lens component 104 and focus ring 124, may be defined by a polynomial relationship. For example, referring to Figure 3, two exemplary polynomial relationships are plotted, with the x-axis representing the rotation angle of focus ring 124 and the y-axis representing the position of first spherical lens element 116 and main lens component 104 along optical axis 118. In some embodiments, the position of first spherical lens element 116 and main lens component 104 along optical axis 118 may be measured relative to their respective origins at their respective limits of movement, which corresponds to the infinity focus configuration of Figure 1A. Thus, as focus ring 124 is rotated about primary lens component 104 in a first rotational direction, the rotation angle of focus ring 124 increases (positive movement along the x-axis), while first spherical lens element 116 and primary lens component 104 both move along optical axis 118 away from the infinity focus configuration ( FIG. 1A , origin) toward the near focus configuration ( FIG. 1B , end point). A first of the exemplary polynomial relationships 302 is: y=-0.0001x 2 +0.1227x-0.0879, which represents the relative movement between focus ring 124 and first spherical lens element 116, while the second of the exemplary polynomial relationships 304 is: y=-0.0000001x 2 +0.0155x-0.0026, which represents the relative movement of the focus ring 124 and the main lens component 104. However, it will be understood that these equations are merely examples and are in no way limiting. In some embodiments, the movements of the first spherical lens element 116 and the main lens component 104 are related so that all combinations of optical elements maintain a constant (or nearly constant) anamorphic ratio and focus along the x and y axes.

[0022] 1A and 1B , as the object 126 moves from a first position ( FIG. 1A ) toward the anamorphic lens assembly 100, astigmatism is produced by the main lens component 104 due to different focal lengths along the horizontal and vertical axes. Therefore, refocusing only the main lens component 104 would not achieve good focus at the image plane 106. In some embodiments, the ability of the first spherical lens element 116 to translate along the optical axis 118 relative to the cylindrical lens elements 112, 114 and the main lens component 104 produces astigmatism opposite to that produced by the movement of the object 126 relative to the main lens component 104, allowing the anamorphic lens assembly 100 to achieve good focus at the image plane 106 regardless of the distance of the object 126 to the lens assembly 100.

[0023] In some embodiments, the optical properties of the combination of the first cylindrical lens element 112, the first spherical lens element 116, and the second cylindrical lens element 114 produce zero astigmatism at the image plane 106 for an object 126 at infinity focus. For example, as shown in FIG. 2A , when the object 126 is at infinity focus and the anamorphic lens assembly 100 is in an infinity focus configuration, on-axis rays 202 converge to the image plane 106, and off-axis rays 204 similarly converge to the image plane 106. In some embodiments, the optical properties of the combination of the first cylindrical lens element 112, the first spherical lens element 116, and the second cylindrical lens element 114 are adjustable as the first spherical lens element 116 translates along the optical axis 118 relative to the first cylindrical lens element and the second cylindrical lens elements 112, 114, such that the first cylindrical lens element 112, the first spherical lens element 116, and the second cylindrical lens element 114 combine to produce a first astigmatism that is opposite to a second astigmatism produced in the image plane 106 by the one or more second spherical lens elements 122 as the object 126 moves from a first position at infinity focus towards the anamorphic lens assembly 100. For example, as shown in FIG. 2B, when object 126 is at a close distance and anamorphic lens assembly 100 is in a near focus configuration, on-axis rays 202 converge to image plane 106, and off-axis rays 204 similarly converge to image plane 106.

[0024] In some embodiments, the spherical aberration of the first spherical lens element 116 is corrected to match the optical properties of the entire anamorphic lens assembly 100. In some embodiments, because the first spherical lens element 116 is movable relative to the first and second cylindrical lens elements 112, 114 and the main lens component 104, its spherical aberration cannot be perfectly corrected for all positions of the first spherical lens element 116 along the optical axis 118. Therefore, the first spherical lens element 116 may not have an ideal shape. Rather, its shape is selected to balance other aberrations from the first and second cylindrical lens elements 112, 114 and the main lens component 104 based on the optical properties of those lenses.

[0025] 1A and 1B, as anamorphic lens assembly 100 transitions between the infinity focus configuration (FIG. 1A) and the near focus configuration (FIG. 1B), the horizontal and vertical focal lengths of the combination of first cylindrical lens element 112, first spherical lens element 116, and second cylindrical lens element 114 change due to the change in spacing between these lens elements. The changing focal lengths also slightly change the anamorphic ratio of anamorphic lens component 102. In some embodiments, the difference in anamorphic ratio is less than 2% (or less than 5%, or less than 4%, or less than 3%) between the infinity focus configuration and the near focus configuration.

[0026] In the illustrated embodiment, the first spherical lens element 116 has negative refractive power, and the first spherical lens element 116 moves away from the first cylindrical lens element 112 and toward the second cylindrical lens element 114 as the anamorphic lens assembly 100 transitions away from the infinity focus configuration toward the near focus configuration. In an alternative embodiment, the first spherical lens element 116 may have positive refractive power, and in such an embodiment, the first spherical lens element 116 moves away from the second cylindrical lens element 114 and toward the second cylindrical lens element 112 as the anamorphic lens assembly 100 transitions away from the infinity focus configuration toward the near focus configuration.

[0027] 4A-4D show the general arrangement of the anamorphic lens assembly 100 of FIGS. 1A and 1B using paraxial optics. In FIGS. 4A and 4B, the viewpoint is along the y-axis 121, and in FIGS. 4C and 4D, the viewpoint is along the x-axis 120. Each of the lens elements / components 104, 112, 114, 116 has a focal length f x The distance between the lens elements / components 104, 112, 114, 116 is d x where d1 is the distance between the first cylindrical lens element 112 and the first spherical lens element 116, d2 is the distance between the first spherical lens element 116 and the second cylindrical lens element 114, and d3 is the distance between the second cylindrical lens element 114 and the main lens component 104. The back focal length (BFL) of the anamorphic lens assembly 100 is the distance between the main lens component 104 and the image plane 106.

[0028] In the illustrated embodiment, first cylindrical lens element 112 has a negative focal length f along the x-axis 120, first spherical lens element 116 has a negative focal length f, second cylindrical lens element 114 has a positive focal length f along the x-axis 120, and main lens component 104 has a positive focal length f. In some embodiments, the focal lengths of lens elements / components 104, 112, 114, 116 are selected so that the effective focal length of anamorphic lens assembly 100 along the x-axis 120 (horizontal) is shorter than the effective focal length along the y-axis (vertical) by a desired anamorphic ratio. In some embodiments, the BFL of anamorphic lens assembly 100 is the same along both the x-axis 120 and the y-axis (zero astigmatism).

[0029] The EFL (effective focal length) of the anamorphic lens assembly 100 along the y-axis can be calculated from the focal lengths of the first spherical lens element 116 (f2) and the main lens component 104 (f4) and the distance d2+d3 between them. In the case of the y-axis, the first and second cylindrical lens elements 112, 114 can be ignored since they have zero refractive power along the y-axis (at least in this exemplary embodiment). The equation for the EFL of the first spherical lens element 116 and the main lens component 104 along the y-axis (when expressed as two thin lenses) is:

[0030]

number

[0031] Calculating the EFL of the anamorphic lens assembly 100 along the x-axis 120 (including the cylindrical powers of the first and second cylindrical lens elements 112, 114) is more complex but can be expressed using ABCD matrix techniques. For an anamorphic lens assembly 100 including four lens elements / components 104, 112, 114, 116, the Gaussian transfer matrix is represented by the product:

[0032]

number

[0033] The resulting ABCD transfer matrix can be used to determine the EFL of the anamorphic lens assembly 100 along the x-axis 120, which is represented by the C term of the matrix (bottom left). The equation for the EFL of the anamorphic lens assembly 100 along the x-axis 120 is:

[0034]

number

[0035] A solution to the above paraxial problem can also be found using damped least-squares optimization with the constraints that the horizontal and vertical EFL differ by the anamorphic ratio and the BFL be the same in both axes over the range of focus positions.

[0036] An example solution to the paraxial problem is given below: Referring to the infinity focus arrangement of Figures 4A and 4C, the following values are assigned: f1=-100mm cylindrical (x-axis) f2=-240mm spherical f2=-240mm cylindrical (x-axis) f4=50mm spherical d1=18mm d2=37mm d3=12.7mm

[0037] The paraxial coupling described above results in an EFL of 50 mm along the y-axis and an EFL of 33.4 mm along the x-axis 120, with a paraxial BFL of 60.4 mm. In this example, the anamorphic ratio at the infinity focus configuration is 1.5x. When the object 126 is moved closer to the anamorphic lens assembly 100 (e.g., to a distance of 500 mm in FIGS. 4A and 4D , the distance between the object 126 and the anamorphic lens assembly 100 is not drawn to scale), the relative positions of the four lens elements / components 104, 112, 114, and 116 are adjusted (e.g., by rotating the focus ring 124) to form a focused image at the image plane 106. This configuration refers to the near focus configuration of FIGS. 4B and 4D . d1=43.51mm d2=11.49mm d3=4.55mm

[0038] Note that because the distance between the first cylindrical lens element 112 and the second cylindrical lens element 114 is fixed, the sum of d1 and d2 remains constant when the anamorphic lens assembly 100 is focused. In this paraxial representation, the anamorphic ratio changes slightly (e.g., to 1.468x), and the EFL along the y- and x-axes change to 58.2 mm and 39.7 mm, respectively, while the paraxial BFL increases to 67.48 mm in the near-focus configurations of Figures 4B and 4D. Because astigmatism is corrected by the combination of the three lens elements 112, 114, and 116, refocusing by adjusting the main lens component 104 (moving f4 relative to f3) or by moving the image plane 106 does not affect image quality.

[0039] Note that not all solutions for the above paraxial system are practical, since it is possible to have solutions where one or more of the distances d1, d2, or d3 are negative. A practical solution may also require a small change in anamorphic ratio between the infinity focus and close focus configurations, although in practice it is possible to limit this change in anamorphic ratio to less than a few percent.

[0040] Table 1 below provides the optical prescription for one exemplary embodiment of the anamorphic lens assembly 100 shown in FIGS. 1A and 1B.

[0041] [Table 1]

[0042] In some embodiments, the following paraxial solution process may be used to narrow the range of possible configurations of the anamorphic lens assembly: The paraxial solution process defines the following ten variables: Lens focal length: f1, f2, f3, f4; Distance between lenses at infinity focal position: d 1inf ,d 2inf ,d 3inf and Distance between lenses in near focus configuration: d 1close ,d 2close ,d 3close .

[0043] Using these ten variables, and based on the known and / or desired characteristics of the resulting anamorphic lens assembly, the paraxial solution process defines the following six equations: (1)d 1inf +d 2inf =d 1close +d 2close (due to the fixed spacing of the cylindrical lens elements f1 and f3) (2)

[0044]

number

[0045]

number

[0046] With six equations in ten variables, there is an infinite set of solutions. However, setting two or three of the variables as constants reduces the range of the solution set sufficiently to allow a solution to be found, for example, using iterative techniques.

[0047] In some embodiments, the anamorphic ratio is the same at both the infinity and near focus positions, so that equations (2) and (3) above are equal. However, as discussed above, in some embodiments of the present anamorphic lens assembly, the anamorphic ratio may vary slightly between the infinity and near focus positions. For example, the anamorphic ratio may vary by less than 2% between the infinity and near focus positions. In embodiments in which the anamorphic ratio at the infinity focus position is not equal to the anamorphic ratio at the near focus position, equations (2) and (3) above are not equal. In such embodiments, the lens design process may advantageously attempt to match the anamorphic ratio variation of legacy, or classic, anamorphic lenses. In traditional anamorphic lenses, the anamorphic ratio is typically smaller at the near focus position than at the infinity focus position. While a paraxial solution exists in which the anamorphic ratio does not change between the near focus position and the infinity focus position, in practice, this condition may not be achievable due to interactions between the principal planes of the various lens groups.

[0048] As discussed above, in some embodiments, one or more of the lens elements may comprise multiple lenses, such as a doublet. Figures 5A and 5B show one such exemplary embodiment. The anamorphic lens assembly 500 of Figures 5A and 5B includes a first cylindrical lens element 502 and a second cylindrical lens element 504, each comprising a doublet. The doublet of the first cylindrical lens element 502 includes two negative cylinders, and the doublet of the second cylindrical lens element 504 includes two cylinders, both of which have positive refractive power and reduce chromatic aberration. In some embodiments, the doublet of the second cylindrical lens element 504 may include two positive cylinders. The first spherical lens element 506 has a negative refractive power such that the first spherical lens element 506 moves toward the primary lens component 508 as the anamorphic lens assembly 500 transitions away from the infinity focus configuration of Figure 5A toward the near focus configuration of Figure 5B. In the illustrated embodiment, the anamorphic ratio of the anamorphic lens assembly 500 may include, for example, a 1.8x squeeze (or any other squeeze).

[0049] As discussed above, in some embodiments, the first spherical lens element can have positive refractive power. Figures 6A and 6B show one such exemplary embodiment. The anamorphic lens assembly 600 of Figures 6A and 6B includes a first spherical lens element 602 that includes a doublet with positive refractive power. The first spherical lens element 602 moves toward the primary lens component 604 as the anamorphic lens assembly 600 transitions away from the infinity focus configuration of Figure 6A toward the near focus configuration of Figure 6B.

[0050] In the paraxial representation of some embodiments, distance d3 may not change as the focus of the anamorphic lens assembly is adjusted. Instead, the BFL (the distance between f4 and the image plane 106) may change. FIGS. 7A and 7B show an exemplary embodiment of one such anamorphic lens assembly 700. FIG. 7A shows the anamorphic lens assembly 700 in an infinity focus configuration, and FIG. 7B shows the anamorphic lens assembly 700 in a near focus configuration. As the anamorphic lens assembly 700 transitions from the infinity focus configuration ( FIG. 7A ) to the near focus configuration ( FIG. 7B ), d1 increases while d2 decreases, so that the sum of d1 and d2 remains constant. d3 remains constant while the BFL of the anamorphic lens assembly 700 increases. In alternative embodiments, the relative changes in d1, d2, d3, and BFL may vary, particularly as the focal lengths of the various lenses change. 7A and 7B , in an alternative embodiment in which the first spherical lens element 116 has a negative focal length f2, as the anamorphic lens assembly transitions from an infinity focus configuration to a near focus configuration, d1 may decrease while d2 increases, d3 remains constant, and the BFL of the anamorphic lens assembly decreases. Furthermore, a paraxial solution exists for embodiments in which d3 changes and the BFL remains constant, and the focusing mechanism of the primary lens component 104 does not necessarily require the primary lens component 104 to move away from the image plane 106. For example, these conditions may be met in embodiments in which the primary lens component 104 includes an internal focusing mechanism in which the internal lens elements of the primary lens component 104 are movable, but the primary lens component 104 as a whole does not move relative to the anamorphic lens component 102.

[0051] 8A and 8B show another anamorphic lens assembly 800 according to some embodiments. Similar to the embodiment of FIGS. 1A and 1B, the anamorphic lens assembly 800 includes an anamorphic lens component 802, a primary lens component 804, a first cylindrical lens element 812, a second cylindrical lens element 814, and a first spherical lens element 816 disposed between the first cylindrical lens element 812 and the second cylindrical lens element 814. The relative positions of the first and second cylindrical lens elements 812, 814 are fixed along an optical axis 818 of the anamorphic lens assembly 800, and the first spherical lens element 816 is translatable along the optical axis 818 relative to the first and second cylindrical lens elements 812, 814. Table 2 below provides the optical prescription for the exemplary embodiment of anamorphic lens assembly 800 shown in Figures 8A and 8B.

[0052] [Table 2]

[0053] In the foregoing description, various embodiments have been described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Additionally, well-known features may be omitted or simplified so as not to obscure the embodiments being described.

[0054] References to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments necessarily include that particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, it is within the knowledge of one skilled in the art that when a particular feature, structure, or characteristic is described in connection with one embodiment, it also affects such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0055] Additionally, in the various embodiments described above, unless otherwise specified, disjunctive language such as the phrase "at least one of A, B, or C" shall be understood to mean either A, B, or C, or any combination thereof (e.g., A, B, and / or C). Similarly, language such as "at least one or more of A, B, and C" (or "one or more of A, B, and C") shall be understood to mean either A, B, or C, or any combination thereof (e.g., A, B, and / or C). Thus, disjunctive language is not intended to, and should not be understood to, imply that a given embodiment requires the presence of at least one of A, at least one of B, and at least one of C, respectively.

[0056] As used herein, the term "based on" (or similar terms) is an open-ended term used to describe one or more factors that influence a decision or other action. The term does not exclude additional factors that may influence the decision or action. For example, a decision may be based only on the listed factors, or it may be based on the factors and one or more additional factors. Thus, if action A is "based on" B, B is one factor that influences action A, but this does not exclude action A from also being based on one or more other factors, such as factor C. However, in some instances, action A may be based entirely on B.

[0057] Unless expressly stated otherwise, articles such as "a" or "an" should generally be construed to include one or more listed items. Thus, phrases such as "a device configured to" or "a computing device" are intended to include one or more listed devices. Such one or more listed devices may be collectively configured to perform the stated operations. For example, "a processor configured to perform operations A, B, and C" may include a first processor configured to perform operation A working in conjunction with a second processor configured to perform operations B and C.

[0058] Additionally, the words "may" and "can" are used in a permissive sense (meaning having the possibility) rather than an obligatory sense (meaning a must). The words "include," "including," and "includes" are used to indicate an open-ended relationship and thus mean including, but not limited to. Similarly, the words "have," "having," and "has" also indicate an open-ended relationship and thus mean having, but not limited to. As used herein, terms such as "first," "second," and "third" are used as labels for the nouns they precede and no type of ordering (e.g., spatial, temporal, logical, etc.) is intended to imply unless such ordering is expressly indicated otherwise.

[0059] Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. It will, however, be apparent that various modifications and changes can be made thereto without departing from the broader scope of the present disclosure as set forth in the claims.

Claims

1. 1. An anamorphic lens assembly for a camera, the anamorphic lens assembly comprising: an anamorphic lens component; a main lens component; The anamorphic lens component comprises: a first cylindrical lens element of negative refractive power having a first radius of curvature along a first axis; a second cylindrical lens element of positive refractive power having a second radius of curvature along the first axis, the relative positions of the first and second cylindrical lens elements being fixed along an optical axis of the anamorphic lens assembly; and a first spherical lens element disposed between the first cylindrical lens element and the second cylindrical lens element, the first spherical lens element being translatable along the optical axis relative to the first and second cylindrical lens elements; The main lens component is one or more second spherical lens elements disposed on an opposite side of the second cylindrical lens element from the first spherical lens element; an order of the lens elements comprising, from the object side to the image side, the first cylindrical lens element, the first spherical lens element, the second cylindrical lens element, and the one or more second spherical lens elements; optical properties of the combination of the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element that produce zero astigmatism in an image plane for an object at infinity focus; an optical characteristic of the combination of the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element is adjustable by translating the first spherical lens element along the optical axis relative to the first and second cylindrical lens elements, such that as the object moves from the infinity focus toward the anamorphic lens assembly, the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element combine to produce a first astigmatism opposite to a second astigmatism produced in the image plane by the one or more second spherical lens elements.

2. 2. The anamorphic lens assembly for a camera of claim 1, wherein the first spherical lens element is movable relative to the main lens component along the optical axis.

3. 3. The anamorphic lens assembly for a camera of claim 2, wherein the main lens component further comprises a focus ring, and the relative movement between the focus ring and the first spherical lens element is defined by a polynomial relationship.

4. 1. An anamorphic lens assembly, comprising: a first cylindrical lens element; a second cylindrical lens element; and a first spherical lens element disposed between the first cylindrical lens element and the second cylindrical lens element and movable relative to the first and second cylindrical lens elements; an anamorphic lens assembly, wherein optical properties of the combination of the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element are adjustable as the first spherical lens element moves relative to the first and second cylindrical lens elements, such that as an object moves from an infinity focus toward the anamorphic lens assembly, the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element combine to produce a first astigmatism opposite to a second astigmatism produced in an image plane by one or more second spherical lens elements.

5. 5. The anamorphic lens assembly of claim 4, wherein the one or more second spherical lens elements comprise a main lens component, the main lens component comprising a focusing member disposed about the main lens component.

6. The focusing member, the main lens component, and the first spherical lens element are mechanically coupled such that as the focusing member rotates about the main lens component in a first rotational direction, the main lens component is adjusted away from an infinity focus configuration and toward a near focus configuration, while the first spherical lens element: a first direction toward the second cylindrical lens element and away from the first cylindrical lens element; or The anamorphic lens assembly of claim 5 , wherein the lens element moves in one of a second direction away from the second cylindrical lens element and toward the first cylindrical lens element.

7. The anamorphic lens assembly of claim 5 , wherein the first spherical lens element is movable relative to the main lens component along the optical axis.

8. 8. The anamorphic lens assembly of claim 7, wherein the main lens component further comprises a focusing member, and wherein the relative movement of the focusing member and the first spherical lens element is defined by a polynomial relationship.

9. 8. The anamorphic lens assembly of claim 7, wherein as the first spherical lens element moves along the optical axis relative to the first and second cylindrical lens elements, a spacing between the second cylindrical lens element and the main lens component changes.

10. 5. The anamorphic lens assembly of claim 4, wherein the optical properties of the combination of the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element produce zero astigmatism at the image plane for the object at an infinity focus.

11. 5. The anamorphic lens assembly of claim 4, wherein as the anamorphic lens assembly transitions between an infinity focus configuration and a near focus configuration, horizontal and vertical focal lengths of the combination of the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element change due to changes in a first spacing between the first cylindrical lens element and the first spherical lens element and a second spacing between the second cylindrical lens element and the first spherical lens element.

12. The anamorphic lens assembly of claim 11 , wherein the change in focal length also changes the anamorphic ratio of the anamorphic lens assembly.

13. The anamorphic lens assembly of claim 12 , wherein the difference in the anamorphic ratio between the infinity focus configuration and the close focus configuration is less than 2%.

14. 1. A camera system comprising: an image plane; an anamorphic lens component; a main lens component; The anamorphic lens component comprises: a first cylindrical lens element; a second cylindrical lens element; and a first spherical lens element disposed between the first cylindrical lens element and the second cylindrical lens element and movable relative to the first cylindrical lens element and the second cylindrical lens element; The main lens component is one or more second spherical lens elements disposed on an opposite side of the second cylindrical lens element from the first spherical lens element; optical properties of the combination of the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element are adjustable as the first spherical lens element moves relative to the first and second cylindrical lens elements such that as an object moves from an infinity focus toward the camera system, the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element combine to produce a first astigmatism opposite to a second astigmatism produced in the image plane by the one or more second spherical lens elements.

15. The camera system of claim 14 , further comprising a focus adjustment member disposed about the main lens component.

16. The focusing member, the main lens component, and the first spherical lens element are mechanically coupled such that as the focusing member rotates about the main lens component in a first rotational direction, the main lens component is adjusted away from an infinity focus configuration and toward a near focus configuration, while the first spherical lens element: a first direction toward the second cylindrical lens element and away from the first cylindrical lens element; or 16. The camera system of claim 15, wherein the lens element moves in one of a second direction away from the second cylindrical lens element and toward the first cylindrical lens element.

17. 15. The camera system of claim 14, wherein the first spherical lens element is movable relative to the main lens component along the optical axis.

18. 20. The camera system of claim 17, wherein the main lens component further comprises a focusing member, and wherein the relative movement of the focusing member and the first spherical lens element is defined by a polynomial relationship.

19. 18. The camera system of claim 17, wherein a spacing between the second cylindrical lens element and the main lens component changes as the first spherical lens element moves along the optical axis relative to the first and second cylindrical lens elements.

20. 15. The camera system of claim 14, wherein the optical properties of the combination of the first cylindrical lens element, the first spherical lens element, and the second cylindrical lens element produce zero astigmatism at the image plane for the object at infinity focus.

Images