Imaging system and electronic apparatus comprising said imaging system

Abstract

An imaging system (1) comprising a first lens arrangement (2), a second lens arrangement (3), and a refracting arrangement (4) arranged between said first lens arrangement (2) and said second lens arrangement (3) along an optical axis (O) of said imaging system (1). The refracting arrangement (4) comprises a first refracting surface (5) and a second refracting surface (6), said first refracting surface (5) and said second refracting surface (6) being separated by a gap (8). The first refracting surface (5) is configured to fold a light ray path (R) by a first folding angle (α), said second refracting surface (6) is configured to fold said folded light ray path (R) by a second folding angle (β), and said second folding angle (β) is a negative of said first folding angle (α) relative said optical axis (O).

Description

[0001] IMAGING SYSTEM AND ELECTRONIC APPARATUS COMPRISING SAID IMAGING SYSTEM

[0002] TECHNICAL FIELD

[0003] The disclosure relates to an imaging system comprising a first lens arrangement, a second lens arrangement, and a refracting arrangement.

[0004] BACKGROUND

[0005] There are several difficulties relating to imaging systems for smaller devices such as portable electronic apparatuses. Electronic apparatuses such as smartphones preferably have as small outer dimensions as possible, while imaging 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. Attempts have been made to solve the problem using a folded light ray path, for example by using Cassegrain double reflectionbased 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.

[0007] 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.

[0008] A further option is to use optically folded “periscope type” structures having long focal lengths. These require more effective focusing capability from the optics and actuation system in terms of lens movements. Instead of moving the lens elements several millimeters, in order to focus or zoom, a tunable lens (also known as “solid-state” or “deformable” lens) can be introduced into the imaging system, which eliminates long movement by instead changing its shape within its original volume and by creating a variable refraction effect itself. Tunable lenses can also eliminate certain lenses from the conventional system. These lenses are very effective as they have strong optical power of several tens of diopters due to changing / deforming optical surface curvature.

[0009] However, two critical performance factors for far-distance telecentric or optical zoom systems are the module size (especially the system thickness which impacts the thickness of the electronic apparatus) and the optical aperture size (for maximizing the amount of incoming light from distant objects and in low light conditions). Usually, the height / length of the imaging system needs to be small while the size of the optical aperture needs to be as large as possible, but these factors are mutually contradictory.

[0010] Known solutions place the tunable lens either along the horizontal section of the optical path or above a folding (prism / mirror) element. The latter integration option increases the module height greatly and may be unacceptable. The former integration option keeps the module height low but requires the tunable lens, due to its typical structure, to have reduced clear aperture so that the outline body shape of the lens still fits into the limited height. Thus, this element becomes the bottleneck in the optical system for the incoming light. Integration of tunable, such as liquid-based, lenses also involves a size aspect, as the physical size / area of the lens cannot be used fully for light transmission due to, e.g., the liquid container mechanical frame structure, sealing and gluing margins on the surrounding frame area, optical quality requirements (the deforming membrane has low optical performance near the outer contact edge and extra margin is needed), manufacturing and assembly requirements. In order to address all of these factors, the thickness / height of the periscope camera architecture needs to be increased.

[0011] Hence, there is a need for an improved imaging system suitable for electronic apparatuses.

[0012] SUMMARY

[0013] It is an object to provide an improved imaging system in particular for portable electronic apparatuses. 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.

[0014] According to a first aspect, there is provided an imaging system comprising a first lens arrangement, a second lens arrangement, and a refracting arrangement arranged between the first lens arrangement and the second lens arrangement along an optical axis of the imaging system, the refracting arrangement comprising a first refracting surface and a second refracting surface, the first refracting surface and the second refracting surface being separated by a gap, the first refracting surface being configured to fold a light ray path by a first folding angle, the second refracting surface being configured to fold the folded light ray path by a second folding angle, the second folding angle being a negative of the first folding angle relative the optical axis.

[0015] 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. The refracting arrangement generates a double-folding angle to the optical axis which helps to raise the location of the first lens arrangement or the second lens arrangement relative the optical axis. This allows to vertically accommodate a larger (taller) lens more efficiently and to leave space for any necessary side attachment or clear aperture margins, and also to increase the aperture size.

[0016] In a possible implementation form of the first aspect, the optical axis extends in a first plane, the light ray path extending in a second plane parallel with the first plane after having been folded by the first folding angle and the second folding angle. This allows the first lens arrangement or the second lens arrangement to be offset relative the optical axis, in turn accommodating a larger (taller) lens more efficiently and leaving space for any necessary side attachment or clear aperture margins, and also increasing aperture size.

[0017] In a further possible implementation form of the first aspect, the first refracting surface and the second refracting surface extend in parallel and at a third angle relative the optical axis, ensuring the light ray path is folded identically regardless of where it first intersects the refracting arrangement.

[0018] In a further possible implementation form of the first aspect, the first refracting surface and the second refracting surface are arranged in a single-piece refraction element, simplifying assembly.

[0019] In a further possible implementation form of the first aspect, the first refracting surface is arranged in a first refraction element and the second refracting surface is arranged in a second refraction element, the first refracting surface and the second refracting surface forming diagonals of the wedges, providing maximum flexibility to the imaging system.

[0020] In a further possible implementation form of the first aspect, the gap comprises air. This increases flexibility and reduces material costs. In a further possible implementation form of the first aspect, the first refraction element and the second refraction element are both shaped as right-angle wedges, the first refracting surface and the second refracting surface forming diagonals of the wedges, simplifying manufacture.

[0021] In a further possible implementation form of the first aspect, the first refraction element and the second refraction element are configured such that they form a rectangular parallelepiped when the full area of the first refracting surface and the full area of the second refracting surface abut, simplifying manufacture.

[0022] In a further possible implementation form of the first aspect, the first refraction element and the second refraction element are identical elements arranged at 180° angle relative each other, simplifying manufacture.

[0023] In a further possible implementation form of the first aspect, the first lens arrangement and the second lens arrangement each comprise at least one lens. This allows the imaging system to be adapted to any desired optics configuration.

[0024] In a further possible implementation form of the first aspect, the first lens arrangement and / or the second lens arrangement comprise at least one tunable lens. This eliminates the need for long lens movement and may also eliminate the need for certain additional lenses.

[0025] In a further possible implementation form of the first aspect, the first refraction element is part of the tunable lens. This may simplify the imaging system and its assembly.

[0026] In a further possible implementation form of the first aspect, the imaging system further comprises a prism configured to fold the light ray path before reaching the first lens arrangement, further improving the focal length of the imaging system.

[0027] According to a second aspect, there is provided an electronic apparatus comprising the imaging system according to the above, wherein a housing of the electronic apparatus comprises a raised area accommodating only the first lens arrangement and the refracting arrangement of the imaging system, or only the second lens arrangement and the refracting arrangement of the imaging system. Such an electronic apparatus allows for a generally thin form factor while still being able to provide a long focal length.

[0028] These and other aspects will be apparent from the embodiments described below.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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:

[0031] Fig. 1 shows an illustration of an imaging system in accordance with an example of the embodiments of the disclosure;

[0032] Fig. 2 shows an illustration of an imaging system in accordance with a further example of the embodiments of the disclosure;

[0033] Fig. 3 illustrates a side view of a part of an imaging system in accordance with a further example of the embodiments of the disclosure;

[0034] Fig. 4a shows a perspective view of an electronic apparatus comprising an imaging system in accordance with a further example of the embodiments of the disclosure; Fig. 4b shows a cross-sectional side view of the electronic apparatus of Fig. 4a, illustrating the placement of the imaging system and the resulting so-called camera bump.

[0035] DETAILED DESCRIPTION

[0036] The present invention relates to an imaging system 1 comprising a first lens arrangement 2, a second lens arrangement 3, and a refracting arrangement 4 arranged between the first lens arrangement 2 and the second lens arrangement 3 along an optical axis O of the imaging system 1, the refracting arrangement 4 comprising a first refracting surface 5 and a second refracting surface 6, the first refracting surface 5 and the second refracting surface 6 being separated by a gap 8, the first refracting surface 5 being configured to fold a light ray path R by a first folding angle a, the second refracting surface 6 being configured to fold the folded light ray path R by a second folding angle [>. the second folding angle [> being a negative of the first folding angle a relative the optical axis O.

[0037] As shown in Figs. 1 and 2, the imaging system 1 comprises a first lens arrangement 2, a second lens arrangement 3, and a refracting arrangement 4 arranged between the first lens arrangement 2 and the second lens arrangement 3 along an optical axis O of the imaging system 1.

[0038] The refracting arrangement 4 comprises a first refracting surface 5 and a second refracting surface 6, the first refracting surface

[0039] 5 and the second refracting surface 6 being separated by a gap 8. The first refracting surface 5 and the second refracting surface

[0040] 6 may extend in parallel and at a third angle y relative the optical axis O.

[0041] The first refracting surface 5 is configured to fold a light ray path R by a first folding angle a, and the second refracting surface 6 is configured to fold the folded light ray path R by a second folding angle [>. the second folding angle [> being a negative of the first folding angle a relative the optical axis O.

[0042] The optical axis O may extend in a first plane Pl, and the light ray path R may extend in a second plane P2 parallel with the first plane Pl after having been folded by the first folding angle a and the second folding angle [>. This is illustrated with a dashed line in Figs. 1, 2, 3, and 4b.

[0043] As shown in Fig. 2, the first refracting surface 5 and the second refracting surface 6 may be arranged in a single-piece refraction element 7, i.e., the first refracting surface 5 and the second refracting surface 6 form the two main surfaces of the single-piece refraction element 7. The single-piece refraction element may be an irregular quadrilateral. In such embodiments, gap 8 may comprise glass or any other suitable material typically used in prisms or for refraction elements.

[0044] As shown in Figs. 1, 3, and 4b, the first refracting surface 5 may be arranged in a first refraction element 7a and the second refracting surface 6 may be arranged in a second refraction element 7b. In such embodiments, gap 8 may comprise air.

[0045] The first refraction element 7a and the second refraction element 7b may both be shaped as right-angle wedges, the first refracting surface 5 and the second refracting surface 6 forming diagonals of the wedges.

[0046] The first refraction element 7a and the second refraction element 7b may be configured such that they form a rectangular parallelepiped when the full area of the first refracting surface 5 and the full area of the second refracting surface 6 abut. The first refracting surface 5 of the first refraction element 7a may be a flat surface extending substantially perpendicular to the optical axis O, and the second refracting surface 6 of the second refraction element 7b may be a flat surface extending substantially perpendicular to the optical axis O. The first refraction element 7a and the second refraction element 7b may be identical elements arranged at 180° angle relative each other.

[0047] The first lens arrangement 2 and the second lens arrangement 3 may each comprise at least one lens 9. The first lens arrangement 2 and / or the second lens arrangement 3 may comprise at least one tunable lens 10. A tunable optical element, such as e.g. liquid liquid-filled tunable lens, is able to change the curvature of a transparent optical membrane enclosing the liquid container and thus adjust the refraction factor for the incoming and passing light through the element. Curvature change is typically adjusted by changing the internal pressure of the optical liquid with the help of an actuator and the use of mechanical force.

[0048] As shown in Fig. 3, the first refraction element 7a may be part of the tunable lens 10. For example, the first refraction element 7a may be directly integrated with the tunable lens 10 by replacing the usual flat sealing plate (typically glass) with the first refraction element 7a on one side of the liquid container of the tunable lens 10.

[0049] The imaging system 1 may further comprise a prism 11 configured to fold the light ray path R before reaching the first lens arrangement 2.

[0050] The present invention also relates to an electronic apparatus 12 comprising the imaging system 1 described above, e.g. a smartphone or tablet. As shown in Figs. 4a and 4b, a housing 13 of the electronic apparatus 12 comprises a raised area 14, as so-called camera bump, accommodating only the first lens arrangement 2 and the refracting arrangement 4 of the imaging system 1, or only the second lens arrangement 3 and the refracting arrangement 4 of the imaging system 1. This allows the thickness of the apparatus to be increased in an as small area as possible, i.e. keeping the area of the camera bump as small as possible.

[0051] 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 measures cannot be used to advantage.

[0052] 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. 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 imaging system (1) comprising a first lens arrangement (2), a second lens arrangement (3), and a refracting arrangement (4) arranged between said first lens arrangement (2) and said second lens arrangement (3) along an optical axis (O) of said imaging system (1), said refracting arrangement (4) comprising a first refracting surface (5) and a second refracting surface (6), said first refracting surface (5) and said second refracting surface (6) being separated by a gap (8), said first refracting surface (5) being configured to fold a light ray path (R) by a first folding angle (a), said second refracting surface (6) being configured to fold said folded light ray path (R) by a second folding angle ([>). said second folding angle ([>) being a negative of said first folding angle (a) relative said optical axis (O).

2. The imaging system (1) according to claim 1, wherein said optical axis (O) extends in a first plane (Pl), said light ray path (R) extending in a second plane (P2) parallel with said first plane (Pl) after having been folded by said first folding angle (a) and said second folding angle ([>).

3. The imaging system (1) according to claim 1 or 2, wherein said first refracting surface (5) and said second refracting surface (6) extend in parallel and at a third angle (y) relative said optical axis (O).

4. The imaging system (1) according to any one of the previous claims, wherein said first refracting surface (5) and said second refracting surface (6) are arranged in a single-piece refraction element (7).

5. The imaging system (1) according to any one of claims 1 to 3, wherein said first refracting surface (5) is arranged in a first refraction element (7a) and said second refracting surface (6) is arranged in a second refraction element (7b).

6. The imaging system (1) according to claim 5, wherein said gap (8) comprises air.

7. The imaging system (1) according to claim 5 or 6, wherein said first refraction element (7a) and said second refraction element (7b) are both shaped as right-angle wedges, said first refracting surface (5) and said second refracting surface (6) forming diagonals of said wedges.

8. The imaging system (1) according to any one of claims 5 to 7, wherein said first refraction element (7a) and said second refraction element (7b) are configured such that they form a rectangular parallelepiped when the full area of said first refracting surface (5) and the full area of said second refracting surface (6) abut.

9. The imaging system (1) according to any one of claims 5 to 8, wherein said first refraction element (7a) and said second refraction element (7b) are identical elements arranged at 180° angle relative each other.

10. The imaging system (1) according to any one of the previous claims, wherein said first lens arrangement (2) and said second lens arrangement (3) each comprise at least one lens (9).

11. The imaging system (1) according to claim 10, wherein said first lens arrangement (2) and / or said second lens arrangement (3) comprises at least one tunable lens (10).

12. The imaging system (1) according to claim 11, wherein said first refraction element (7a) is part of said tunable lens (10).

13. The imaging system (1) according to any one of the previous claims, further comprising a prism (11) configured to fold said light ray path (R) before reaching said first lens arrangement (2).

14. An electronic apparatus (12) comprising the imaging system (1) according to any one of claims 1 to 13, wherein a housing (13) of said electronic apparatus (12) comprises a raised area (14) accommodating only the first lens arrangement (2) and the refracting arrangement (4) of said imaging system (1), or only the second lens arrangement (3) and the refracting arrangement (4) of said imaging system (1).

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