Optical imaging arrangement and electronic apparatus comprising said optical imaging arrangement

Abstract

An optical imaging arrangement (1) for a portable electronic apparatus (2) comprising a catadioptric optical system (3) defining an optical axis (O) and being configured such that incoming rays of light enter said catadioptric optical system (3) at an entry area (A1) arranged along said optical axis (O) and exit said catadioptric optical system (3) at an exit area (A2) arranged along said optical axis (O). The catadioptric optical system (3) comprises a plurality of reflective surfaces (4), said plurality of reflective surfaces (4) being configured to fold incoming rays of light before exiting said catadioptric optical system (3) through said exit area (A2). The optical imaging arrangement (1) also comprises a non-planar image sensor (5) configured to receive rays of light exiting said catadioptric optical system (3). The catadioptric optical system may be of a Cassegrain supertele lens type and may be a pop-up type system. (Fig. 2)

Description

[0001] OPTICAL IMAGING ARRANGEMENT AND ELECTRONIC APPARATUS COMPRISING SAID OPTICAL IMAGING ARRANGEMENT

[0002] TECHNICAL FIELD

[0003] The disclosure relates to an optical imaging arrangement for a portable electronic apparatus, as well as a portable electronic apparatus comprising an optical imaging arrangement.

[0004] BACKGROUND

[0005] There are several difficulties relating to optical and imaging systems for portable electronic apparatuses. Electronic apparatuses such as smartphones preferably have as small outer dimensions as possible, while optical systems require certain dimensions in order to provide sufficiently good image sharpness, spatial frequency, sensitivity etc.

[0006] In particular, the z-height (as the industry generally refers to the thickness of a smartphone) should be kept as small as possible. One solution to reducing the z-height while increasing image quality is to integrate additional telephoto sub-camera module(s) in the apparatus, however, the maximum multiple camera zoom factor is limited to around 3x as larger zoom factors are hard, if not impossible, to reach due to the limiting dimensions of the apparatus.

[0007] Attempts have been made to solve the problem using a folded light ray path, for example by using Cassegrain double reflection-based systems as telephoto camera objectives. Such a Cassegrain system comprises a parabolic primary mirror and a hyperbolic secondary mirror that reflects the light back down through a hole in the primary. By folding the light ray path, the design is made more compact.

[0008] However, these systems comprising multiple mirrors and lenses are mechanically complex, with low production and assembly tolerance, and are thus expensive and difficult to implement in small-size apparatuses. Furthermore, due to the sensitive mechanical parts they are prone to fail after extended use.

[0009] Hence, there is a need for an improved optical imaging arrangement suitable for portable electronic apparatuses. SUMMARY

[0010] It is an object to provide an improved optical imaging arrangement for a portable electronic apparatus. The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description, and the figures.

[0011] According to a first aspect, there is provided an optical imaging arrangement for a portable electronic apparatus, the optical imaging arrangement comprising: a catadioptric optical system defining an optical axis and being configured such that incoming rays of light enter the catadioptric optical system at an entry area arranged along the optical axis and exit the catadioptric optical system at an exit area arranged along the optical axis, the catadioptric optical system comprising a plurality of reflective surfaces, the plurality of reflective surfaces being configured to fold incoming rays of light before exiting the catadioptric optical system through the exit area; and a non-planar image sensor configured to receive rays of light exiting the catadioptric optical system.

[0012] This arrangement enables enhanced image quality and eases the tolerance sensitivity by adding optimizable surface shapes to the system. Furthermore, the non-planar surface of the image sensor can be utilized as an additional degree of freedom in performance optimization. The non- planar image sensor allows better and more consistent MTF (modulation transfer function) performance.

[0013] In a possible implementation form of the first aspect, the plurality of reflective surfaces comprises a primary reflective surface arranged adjacent the exit area and a secondary reflective surface is arranged adjacent the entry area, facilitating a simple and compact structure that may be designed in accordance with specific reflection requirements.

[0014] In a further possible implementation form of the first aspect, the primary reflective surface is configured such that it has positive optical power and the secondary reflective surface is configured such that it has negative optical power, facilitating a simplified design while maintaining the advantages of the resulting arrangement. In a further possible implementation form of the first aspect, the primary reflective surface and / or the secondary reflective surface has an aspherical shape, allowing for more optimized correction of the spherical aberration of the reflective surfaces. The aspheric shape optimizes performance, size, cost, yield, and feasibility.

[0015] In a further possible implementation form of the first aspect, the non-planar image sensor has a non-planar spherical or aspherical shape, facilitating enhanced image quality and easing the tolerance sensitivity by adding optimizable surface forms to the arrangement. The aspheric shape optimizes performance, size, cost, yield, and feasibility.

[0016] In a further possible implementation form of the first aspect, the curvature of the image sensor is 1.3-10 x a diagonal dimension of the image sensor, facilitating the best possible performance while minimizing the form factor.

[0017] In a further possible implementation form of the first aspect, the catadioptric optical system further comprises a solid body of optical material, the solid body comprising an annular entry surface forming the entry area; an annular first intermediary surface located opposite to the entry surface; a second intermediary surface being substantially continuous with an inner ring of the annular entry surface; and an exit surface forming the exit area located opposite to the second intermediary surface; wherein the exit surface is connected to the first intermediary surface by an inner wall extending towards the second intermediary surface, thereby defining a void inside the solid body. Such a folding structure, i.e., a structure in which the light ray path is reflected, allows a focal length that is longer than the actual outer dimensions of the body. An electronic device comprising such an imaging system can have a thin form factor while still having a long focal length.

[0018] In a further possible implementation form of the first aspect, a distance between one of the reflective surfaces and the image sensor, along a direction parallel with the optical axis, is variable. The use of, e.g., a pop-up structure facilitating such variation has a significant effect on tolerance sensitivity.

[0019] According to a second aspect, there is provided a portable electronic apparatus comprising the optical imaging arrangement according to the above. Such an electronic apparatus allows for a thin form factor while still having a long focal length. The configuration of the optical imaging arrangement within the housing can enable additional degrees of freedom, e.g. for adjusting the focus length.

[0020] In a possible implementation form of the second aspect, a thickness of the solid body of the optical imaging arrangement, defined as the maximum length of the solid body measured along the optical axis of the catadioptric optical system, is between 75 % and 200 % of the diagonal dimension of the image sensor, which provides a particularly advantageous design for optimized image quality.

[0021] In a further possible implementation form of the second aspect, a dimension of the catadioptric optical system of the optical imaging arrangement, along a direction parallel with the optical axis of the catadioptric optical system, is variable between 0.9-2.1 x a dimension of a housing of the electronic apparatus along the optical axis, which provides a particularly advantageous design for optimized image quality.

[0022] These and other aspects will be apparent from the embodiments described below.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the following detailed portion of the present disclosure, the aspects, embodiments, and implementations will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

[0025] Fig. 1 shows an illustration of a catadioptric optical system comprised within an optical imaging arrangement in accordance with an example of the embodiments of the disclosure;

[0026] Fig. 2 shows an illustration of a portable electronic apparatus comprising an optical imaging arrangement in accordance with an example of the embodiments of the disclosure.

[0027] DETAILED DESCRIPTION

[0028] The present invention relates to an optical imaging arrangement 1 for a portable electronic apparatus 2, the optical imaging arrangement 1 comprising a catadioptric optical system 3 defining an optical axis 0 and being configured such that incoming rays of light enter the catadioptric optical system 3 at an entry area Al arranged along the optical axis O and exit the catadioptric optical system 3 at an exit area A2 arranged along the optical axis O, the catadioptric optical system 3 comprising a plurality of reflective surfaces 4, the plurality of reflective surfaces 4 being configured to fold incoming rays of light before exiting the catadioptric optical system 3 through the exit area A2; and a non-planar image sensor 5 configured to receive rays of light exiting the catadioptric optical system 3.

[0029] The optical imaging arrangement 1 comprises a catadioptric optical system 3 and a non-planar image sensor 5.

[0030] As illustrated in Fig. 1, the catadioptric optical system 3 defines an optical axis O and is configured such that incoming rays of light enter the catadioptric optical system 3 at an entry area Al arranged along the optical axis O and exit the catadioptric optical system 3 at an exit area A2 arranged along the optical axis O.

[0031] The catadioptric optical system 3 comprises a plurality of reflective surfaces 4. The plurality of reflective surfaces 4 is configured to fold incoming rays of light before exiting the catadioptric optical system 3 through the exit area A2, as illustrated in Fig. 2.

[0032] The plurality of reflective surfaces 4 may comprise a primary reflective surface 4a arranged adjacent the exit area A2 and a secondary reflective surface 4b arranged adjacent the entry area Al.

[0033] The catadioptric optical system 3 may be a Cassegrain-type two-mirror-system, in other words, the primary reflective surface 4a and the secondary reflective surface 4b may form a Cassegrain reflector. However, the invention is not limited to a Cassegrain optical system, any suitable type of system may be utilized. The catadioptric optical system 3 may be a supertele lens system.

[0034] The primary reflective surface 4a may be configured such that it has positive optical power and the secondary reflective surface 4b is configured such that it has negative optical power.

[0035] One or more of the reflective surfaces 4, e.g. primary reflective surface 4a and / or secondary reflective surface 4b, may have an aspherical shape. The reflective surfaces may have ellipsoid, parabolic, or hyperbolic shapes. The non-planar image sensor 5 is configured to receive rays of light exiting the catadioptric optical system 3.

[0036] The distance D2 between one of the reflective surfaces 4, 4a, 4b and the image sensor 5, along a direction parallel with the optical axis O, may be variable. By varying the distance D2 by applying a pop-up structure to the catadioptric optical system 3, the dimension D2 may be significantly extended when necessary.

[0037] The curvature of the image sensor 5 may be 1.3-10 x the diagonal dimension D of the image sensor, i.e. up to 10 times the diagonal dimension D. The diagonal dimension D is illustrated in Fig. 2. The diagonal dimension D of the image sensor 5 is illustrated as the length of a diagonal line between two opposing corners of the image sensor 5.

[0038] The non-planar image sensor 5 may have a non-planar spherical or aspherical shape. The non- planar image sensor 5 may have a parabolic and / or concave shape.

[0039] The aspherical shape of the reflective surface(s) 4, 4a, 5b and / or the image sensor 5 may be a freeform shape described by even-order terms or odd-order terms and may be approximated using NURB (Nonuniform Rational Basis Spline) interpolation. The freeform shape may be described by higher order terms, preferably at least 2ndorder terms, even more preferably more than 6thorder terms.

[0040] The catadioptric optical system 3 may further comprise a solid body 6 of optical material. The solid body 6 comprises an annular entry surface 7 forming the entry area Al, an annular first intermediary surface 8 is located opposite to the entry surface 7, a second intermediary surface 9 is substantially continuous with an inner ring of the annular entry surface 7, and an exit surface 10 forming the exit area A2 located opposite to the second intermediary surface 9. The exit surface 10 may be connected to the first intermediary surface 8 by an inner wall 11 extending towards the second intermediary surface 9, thereby defining a void 12 inside the solid body 6.

[0041] The optical material used for the solid body 1 may be optical Polymethyl methacrylate (PMMA, also known as acrylic, acrylic glass, or plexiglass), and the body 1 may be implemented by diamond turning. The solid body may also comprise diffuse surface coating (matte black paint) to reduce incident light and unwanted reflections in the system 3.

[0042] The present invention also relates to a portable electronic apparatus 2 comprising the optical imaging arrangement 1 as illustrated in Fig. 2. The portable electronic apparatus 2 may be a device such as a smartphone, tablet, or laptop.

[0043] The thickness T of the solid body 6 of the optical imaging arrangement 1, defined as the maximum length of the solid body 6 measured along the optical axis O of the catadioptric optical system 3, may be between 75 % and 200 % of the diagonal dimension D of the image sensor 5. For example, the thickness T may be 6,5-7 mm, which corresponds to 90-97 % of diagonal dimension D.

[0044] The dimension D3 of the catadioptric optical system 3 of the optical imaging arrangement 1, along a direction parallel with the optical axis O of the catadioptric optical system 3, is variable between 0.9-2.1 x a dimension D4 of a housing 13 of the electronic apparatus 2 along the optical axis O, i.e. up to 2.1 times as long as the dimension D4 (or thickness) of the housing 13. By applying a pop-up structure to the catadioptric optical system 3, the dimension D3 may be significantly extended when necessary. For example, when using an image sensor having a diagonal dimension D of 7.2 mm, the dimension D3 may be extended to 15 mm by means of a pop-up structure. The housing 13 comprises an aperture arranged within its wall so as to allow light rays from an object to enter the catadioptric optical system 3.

[0045] The various aspects and implementations have been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

[0046] The reference signs used in the claims shall not be construed as limiting the scope. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this disclosure. As used in the description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader.

[0047] Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate.

Claims

CLAIMS1. An optical imaging arrangement (1) for a portable electronic apparatus (2), said optical imaging arrangement (1) comprising:-a catadioptric optical system (3) defining an optical axis (O) and being configured such that incoming rays of light enter said catadioptric optical system (3) at an entry area (Al) arranged along said optical axis (O) and exit said catadioptric optical system (3) at an exit area (A2) arranged along said optical axis (O), said catadioptric optical system (3) comprising a plurality of reflective surfaces (4), said plurality of reflective surfaces (4) being configured to fold incoming rays of light before exiting said catadioptric optical system (3) through said exit area (A2); and-a non-planar image sensor (5) configured to receive rays of light exiting said catadioptric optical system (3).

2. The optical imaging arrangement (1) according to claim 1, wherein said plurality of reflective surfaces (4) comprises a primary reflective surface (4a) arranged adjacent said exit area (A2) and a secondary reflective surface (4b) is arranged adjacent said entry area (Al).

3. The optical imaging arrangement (1) according to claim 1 or 2, wherein said primary reflective surface (4a) is configured such that it has positive optical power and said secondary reflective surface (4b) is configured such that it has negative optical power.

4. The optical imaging arrangement (1) according to any one of the previous claims, wherein said primary reflective surface (4a) and / or said secondary reflective surface (4b) has an aspherical shape.

5. The optical imaging arrangement (1) according to any one of the previous claims, wherein said non-planar image sensor (5) has a non-planar spherical or aspherical shape.

6. The optical imaging arrangement (1) according to claim 5 or 6, wherein the curvature of said image sensor (5) is 1.3-10 x a diagonal dimension (D) of said image sensor (5).

7. The optical imaging arrangement according to any one of the previous claims, wherein said catadioptric optical system (3) further comprises a solid body (6) of optical material, said solid body (6) comprising an annular entry surface (7) forming said entry area (Al); an annular first intermediary surface (8) located opposite to said entry surface (7); a second intermediary surface (9) being substantially continuous with an inner ring of said annular entry surface (7); and an exit surface (10) forming said exit area (A2) located opposite to said second intermediary surface (9); wherein said exit surface (10) is connected to said first intermediary surface (8) by an inner wall (11) extending towards said second intermediary surface (9), thereby defining a void (12) inside said solid body (6).

8. The optical imaging arrangement (1) according to any one of the previous claims, wherein a distance (D2) between one of said reflective surfaces (4, 4a, 4b) and said image sensor (5), along a direction parallel with said optical axis (O), is variable.

9. A portable electronic apparatus (2) comprising the optical imaging arrangement (1) according to any one of claims 1 to 8.

10. The portable electronic apparatus (2) according to claim 9, wherein a thickness (T) of the solid body (6) of said optical imaging arrangement (1), defined as the maximum length of the solid body (6) measured along the optical axis (O) of the catadioptric optical system (3), is between 75 % and 200 % of the diagonal dimension (D) of said image sensor (5).

11. The portable electronic apparatus (2) according to claim 10, wherein a dimension (D3) of the catadioptric optical system (3) of said optical imaging arrangement (1), along a direction parallel with the optical axis (O) of said catadioptric optical system (3), is variable between 0.9- 2.1 x a dimension (D4) of a housing (13) of said electronic apparatus (2) along said optical axis (O).

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