Optical Zoom System and Camera for a Mobile Device

Abstract

An optical zoom camera and an optical zoom system for the optical zoom camera. The optical zoom system comprises at least three spatially separated lens groups, which are arranged on an optical axis. The optical zoom system does not include any further lens groups on the optical axis. A third lens group is immovable along the optical axis, a second lens group is movable along the optical axis to set a magnification of the optical zoom system, and a first lens group is movable along the optical axis to focus the optical zoom system.

Claims

1. An optical zoom system for a mobile device, wherein the optical zoom system comprises: an optical image stabilization (OIS) system; a first lens group arranged on an optical axis and configured to move along the optical axis to focus the optical zoom system using the OIS system: a second group arranged on the optical axis and configured to move along the optical axis to set a magnification of the optical zoom system using the OIS system; and a third lens group arranged on the optical axis and immovable along the optical axis, wherein the first lens group, the second lens group, and the third lens group are spatially separated from each other.

2. The optical zoom system of claim 1, further comprising a fourth lens group that is immovable.

3. The optical zoom system of claim 1, wherein the first lens group and the second lens group are continuously movable along the optical axis.

4. The optical zoom system of claim 1, wherein each of the first lens group, the second lens group, and the third lens group has an assigned separate space in the optical zoom system.

5. The optical zoom system of claim 1, wherein the second lens group and the first lens group are either separately movable or independently movable.

6. The optical zoom system of claim 1, wherein the second lens group is movable between the third lens group and the first lens group.

7. The optical zoom system of claim 1, further comprising: a first actuator configured to move the first lens group; and a second actuator configured to move the second lens group.

8. The optical zoom system of claim 7, wherein the first actuator comprises a voice coil actuator, or wherein the second actuator comprises a screw actuator.

9. The optical zoom system of claim 1, wherein each first lens group, the second lens group, and the third lens group comprises one or more lenses having an elliptical cross section or an i-cut cross section.

10. The optical zoom system of claim 1, wherein the OIS system comprises a tiltable mirror.

11. The optical zoom system of claim 1, wherein the first lens group is arranged before the second lens group and the second lens group is arranged before the third lens group, with respect to a light collecting direction of the optical zoom system.

12. The optical zoom system of claim 1, wherein the second lens group has a negative optical power, and wherein the first lens group has a positive optical power.

13. The optical zoom system of claim 1, wherein the third lens group comprises: a first subgroup arranged on the optical axis and configured to collect a light from the second lens group; and a second subgroup arranged on the optical axis and configured to form a real image from the light, wherein each of the first subgroup and the second subgroup has a positive optical power, and wherein light rays associated with one image point of the real image are parallel between the first subgroup and the second subgroup.

14. A zoom camera for a mobile device, wherein the zoom camera comprises: an optical zoom system configured to collect a light and comprising: an optical image stabilization (OIS) system; a first lens group arranged on an optical axis and configured to move along the optical axis to focus the optical zoom system using the OIS system; a second lens group arranged on the optical axis and configured to move along the optical axis to set a magnification of the optical zoom system using the OIS system; and a third lens group arranged on the optical axis and immovable along the optical axis, wherein the first lens group, the second lens group, and the third group are spatially separated from each other; and one or more image sensors coupled to the optical zoom system, wherein each of the one or more image sensors comprises a sensor surface for capturing a first image based on the light.

15. The zoom camera of claim 14, further comprising a spectral separator configured to separate the light into a plurality of spectral bands, wherein each of the one or more image sensors is configured to capture a second image in one of the spectral bands.

16. The zoom camera of claim 14, wherein the zoom camera is configured to move the first lens group in an autofocus mode.

17. The zoom camera of claim 14, wherein the OIS system comprises a tiltable mirror.

18. The optical zoom system of claim 1, wherein the first lens group is continuously movable along the optical axis.

19. The optical zoom system of claim 1, wherein the second lens group is continuously movable along the optical axis.

20. The optical zoom system of claim 7, wherein the first actuator comprises a piezoelectric actuator, or wherein the second actuator comprises a screw actuator.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0045] The above described aspects and implementation forms of the present disclosure will be explained in the following description of example embodiments in relation to the enclosed drawings.

[0046] FIG. 1 shows an optical zoom system according to an embodiment of the disclosure.

[0047] FIG. 2 shows an optical zoom system according to an embodiment of the disclosure.

[0048] FIG. 3 shows an optical zoom system according to an embodiment of the disclosure.

[0049] FIG. 4 shows an optical zoom system according to an embodiment of the disclosure.

[0050] FIG. 5 shows a spectral separator for a zoom camera according to an embodiment of the disclosure.

[0051] FIG. 6 shows a zoom camera according to an embodiment of the disclosure in a mobile device.

DETAILED DESCRIPTION OF EMBODIMENTS

[0052] FIG. 1 shows an optical zoom system 100 according to an example of an embodiment of the disclosure. The optical zoom system 100 is suitable for an optical zoom camera, as e.g. the zoom camera 600 shown in FIG. 6, and is in particular suitable for being used in a mobile device 601, which may be equipped with the zoom camera 600. The optical zoom system 100 beneficially allows building the zoom camera 600 more compact than with previous concepts, and thus also allows designing mobile device 601 thinner in the future. The optical zoom system 100 also enables a higher magnification, i.e. into the longer tele-phot range, than with previous concepts.

[0053] The optical zoom system 100 to this end comprises at least three spatially separated lens groups 101, which are arranged on an optical axis 102 (indicated by the dashed line). Notably, the optical zoom system 100 does not include any further lens groups, than the at least three lens groups 101, on the optical axis 102. The optical zoom system 100 may, for example, include exactly three lens groups 101 on the optical axis 102, as exemplarily illustrated in FIG. 1.

[0054] Of the at least three lens groups 101 of the optical zoom system 100, at least a third lens group 101c is immovable along the optical axis 102. The optical system 100 may, however, comprise further immovable lens groups 101 on the optical axis 102.

[0055] Furthermore, a second lens group 101b and a first lens group 101a of the optical system 100 are movable along the optical axis 102. The first lens group 101a and the second lens group 101b are, in particular, the only lens groups 101 of the at least three lens groups 101 on the optical axis 102, which are movable. In other words, each lens group 101, except the first lens group 101a and the second lens group 101b, is immovable along the optical axis 102. Thereby, the second lens group 101b is movable along the optical axis 102, in order to set a magnification of the optical zoom system 100, and the first lens group 101a is movable along the optical axis 102, in order to focus the optical zoom system. The first lens group 101a and/or the second lens group 101b may be continuously movable along the optical axis 102 over their respective ranges of movement. The movement ranges of the first lens group 101a and the second lens group 101b may be different, in particular the second lens group 101b may have a larger movement range. Additionally or alternatively, the first lens group 101a and the second lens group 101b may be separately and/or independently movable. That is, each of the two lens groups 101a, 101b can be moved while the other is not moved, and can be moved irrespective of the amount of movement of the other one.

[0056] In the optical zoom system 100, each of the at least three lens groups 101 may be assigned a separate/dedicated space, which is not used and/or is not usable by any other lens group 101. That is, for example, no lens of one lens group 101 may be arranged within/between lenses of another lens group 101. Moreover, the first lens group 101a and the second lens group 101b, respectively, may not be movable to move into the space occupied by/dedicated to another lens group 101. For instance, the second lens group 101b may be movable between the third lens group 101c and the first lens group 101a, however, it cannot be moved into the spaces assigned to the third lens group 101c and the first lens group 101a, respectively.

[0057] FIG. 2 shows the optical system 100 of FIG. 1 with further optional features. In particular FIG. 2 shows an optical zoom system 100 for a tele-photo miniature zoom camera 600, e.g. as shown in FIG. 6, according to an embodiment of the disclosure. FIG. 2 shows a number of elements of the optical zoom system 100, which may each comprises one or more parts, and may also comprise parts that are not drawn (in order to give a better overview of the optical system 100).

[0058] In particular, the optical zoom system 100 shown in FIG. 2 has a light entrance 202, e.g. an aperture, which is followed by a mirror 201, in particular a folding mirror 201. Behind the mirror 201, the first lens group 101a and the second lens group 101b are arranged on the optical axis. Thereby, the first lens group 101a may be arranged before the second lens group 101b (as shown), but also in reverse order. The lens groups 101a and 101b may be followed by the third lens group 101c (as shown), but the order of the three lens groups 101 on the optical axis 102 may also be different.

[0059] The at least three lens groups 101 are followed by a detector assembly 200 configured to detect light collected by the optical zoom system 100, and configured to capture one or more images based on the detected light. The detector assembly 200 may include a spectral separator 500, e.g. an x-cube separator 500 (see FIG. 5), and may further comprise a sensor array comprising a plurality of image sensors 501 (see FIG. 5) after the separator 500. For instance, the detector assembly 200 may comprise three image sensors 501. The spectral separator 500 may in this case transfer three defined wavelength regions onto the three image sensors 501, in a way that it splits the incoming electromagnetic field (light, but can also be/include electromagnetic radiation invisible to the human eye, e.g. IR) at certain spectral bands (which may be confined to an implemented glass or plastic lens materials of the optical zoom system 100 and its lateral color aberration). In other words, the spectral separator 500 is configured to separate the light into a plurality of spectral bands. Then, each image sensor 501 may capture an image in one of these spectral bands.

[0060] After the color separation by the separator 500 (e.g. into red (R), green (G), and blue (B)), each image sensor 501 may detect a spectral band of the incoming/collected light. Special attention should be made to the coating of the spectral separator if realized as x-cube separator 500, in order to meet the spectral bands, and in order to achieve an un-polarized performance (meaning not polarization dependent).

[0061] The moving (first and second) lens groups 101a and 101b may have different zooming functions. The second lens group 101b may be moveable by a greater amount, and may primarily drive the optical zoom system magnification. The first lens group 101a may be moveable by a smaller amount, and may be used to compensate the optical zoom system 100, in order to achieve a stable focusing/imaging onto the image sensor(s) 501.

[0062] The third lens group 101c may comprise at least two subgroups, e.g. a first subgroup 203 and a second subgroup 204. Optionally, it may also comprise a third subgroup 205. The first subgroup 203 and the second subgroup 204 may each have a positive optical power. The third subgroup 204 may have negative optical power. The first subgroup 203 may be arranged and configured such that it collects light from the second lens group 10 lb. It may further be configured to provide the collected light, in particular parallel light rays, to the second subgroup 204. The second subgroup 204 may be configured to form a real image from the collected light, in particular for being captured by the detector assembly 200. Thereby, light rays associated with a given image point of the real image are substantially parallel between the first subgroup 203 and the second subgroup, i.e. within ±4°, or even ±2° from a mean direction of the light rays, e.g. along the optical axis 102.

[0063] FIG. 3 shows an optical zoom system 100 as in FIG. 2, but illustrates a movement of the first lens group 101a and the second lens group 101b, respectively. As can be seen, the movement of the two lens groups 101a and 101b may be quite different. The movement curve of the second lens group 101b (solid line) may be rather big, i.e. it may have a large movement range, while the movement curve of the first lens group 101a (dotted line) may be small, i.e. it may move only very little over a small movement range.

[0064] In this optical zoom system 100 of FIG. 3, the second lens group 101b has a negative optical power, while the first lens group 101a has a positive optical power. It can be further seen from FIG. 3, that the movement of the second lens group 101b may go completely from the first lens group 101a to the third lens group 101c. The first lens group 101a, to the contrary, moves only very little.

[0065] With respect to the mechanical possibilities for moving the different lens groups 101a and 101b, respectively their different movement ranges allow different actuator setups. In particular, a second, e.g. screw, actuator may be provided to move the second lens group 101b. Further, a more precise and/or faster first actuator may move the first lens group 101a, which first actuator could be either a voice coil motor (VCM), or piezo actuator (PA) setup, or a wiggle actuator. The combination of such actuators may ensure the necessary precision and response time to achieve image capturing of the optical zoom camera 600 including the optical zoom system 100, particularly in a modern mobile device.

[0066] Due to the special layout of the optical zoom system 100, as shown in FIGS. 1-3, the first lens group 101a may not only have the task to establish a focal imaging onto the image sensor(s) 501, but may also achieves an optimum near-imaging through its motion. Further, due to the fact that it can be fitted with a fast and/or precise actuator, it is also possible to give the first lens group 101a an auto-focus function, for example, within an optical zoom camera 600.

[0067] FIG. 4 shows an even more detailed picture of the optical zoom system 100, in particular, from the side and the top. It can be seen, that the lens groups 101 (movable first lens group 101a/movable second lens group 101b/fixed third lens group 101c) may each include two or more lens elements to for the lens group 101. These lens elements may have an elliptical optical cross section, which enables more light to enter the optical zoom system 100, and therefore decreases the effective F-Number. Alternatively or in combination, the lens elements may have an i-cut cross section, which provides another possibility to decrease the F-Number. Generally, each lens group 101 may comprises one or more lenses having an elliptical cross section or an i-cut cross section.

[0068] Due to the desired high magnification, the optical zoom system 100 is more sensitive to an angular tilt of the incoming light or ray field. Therefore, OIS may be done upfront, e.g. using the mirror 201 shown in FIG. 2 as an OIS device. In this case, the mirror 201 may be configured to tilt about two axes. By tilting the mirror 201 in two directions, the incoming light/ray field can be stabilized, and can further be properly redirected (e.g. folded) for propagation through the at least three lens groups 101, and further onto the image sensor(s) 501.

[0069] By using, as shown in FIG. 5, a 3-sensor array, i.e. three optical image sensors 501, the zoom camera 600 may be provided with an additional degree of freedom, because the three sensors 501 do not necessarily have to have the same distance from the spectral separator 500 (e.g. x-cube separator). Thus, each image sensor 501, and therefore each spectral band, may have its own optimized working distance behind the spectral separator 500, and therefore behind the fixed third lens group 101c.

[0070] FIG. 6 shows a mobile device 601, which includes a zoom camera 600 according to an embodiment of the disclosure. The mobile device 601 may be a mobile phone, particularly a smartphone, but may also be a tablet, laptop, smartwatch or similar device. The zoom camera 600 comprises the optical zoom system 100 described above with respect to FIGS. 1-5, and comprises one or more image sensors 501. Each image sensor 501 may have a sensor surface configured to capture an image based on light collected by the optical zoom system 100. In particular, as shown in FIG. 5, the zoom camera may further comprise the spectral separator 500 wherein the spectral separator 500 and the image sensor(s) 501 form a detector assembly 200 and the spectral separator 500 may be configured to separate light collected by the optical zoom system 100 into a plurality of spectral bands, e.g. into three bands like R, G, and B. Each image sensor 501 may be configured to capture an image in one of the spectral bands.

[0071] The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed disclosure, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.