JP7801875B2 - Optical Reflective Elements - Google Patents

Description

The present invention relates to optical reflection elements, particularly micromirror devices, and microprojection devices using optical reflection elements.

Japanese Patent Publication No. 5045470 describes an optical reflecting element in which a mirror element is supported by two second support members. One of the two second support members is supported by a first tuning fork vibrator, and the other second support member is supported by a second tuning fork vibrator. The two second support members extend on the rotation axis of the optical reflecting element.

Patent No. 5045470

The present invention is based on the problem of developing an optical reflecting element that optimally utilizes the available space between the drive unit and the mirror of the optical reflecting element.

To achieve this object, an optical reflecting element, particularly a micromirror device, is proposed as described in claim 1. Additionally, a microprojection device is proposed as described in claim 15. This optical reflecting element is particularly configured as a micromirror device, and has a support including a first support member. A first end of the first support member is supported by a support configured, particularly as a frame element of the optical reflecting element. Furthermore, the optical reflecting element has a first tuning fork-type oscillator having a first arm and a second arm. The first and second arms of the first tuning fork-type oscillator are supported by the second end of the first support member. The first tuning fork-type oscillator with the first support member is configured to torsionally vibrate about a rotation axis. In particular, the first support member extends on the rotation axis. The optical reflecting element further has at least a second support member, a third support member, and a mirror element. Here, the mirror element is supported by the second end of the second support member and the second end of the third support member so that the mirror element repeatedly rotates and oscillates around a rotation axis. The rotation axis is particularly a rotation axis common to the tuning fork vibrator and the first support member. The first end of the second support member is supported by the first tuning fork vibrator. In addition, the first end of the third support member is supported by the first tuning fork vibrator. By suspending the mirror element between the second support member and the third support member, nonlinear effects due to plate bending can be avoided.

Preferably, the optical reflecting element further includes a fourth support member of the support. A first end of the fourth support member is supported by the support. The optical reflecting element also includes a second tuning fork-type vibrator having a third arm and a fourth arm. The third and fourth arms of the second tuning fork-type vibrator are supported by the second end of the fourth support member. The second tuning fork-type vibrator including the fourth support member is configured to torsionally vibrate around a rotation axis. In particular, the fourth support member extends on the rotation axis. The optical reflecting element further includes a fifth support member and a sixth support member. Here, the mirror element is supported by the second end of the fifth support member and the second end of the sixth support member so that the mirror element repeatedly rotationally vibrates, in particular around a common rotation axis. The first end of the fifth support member is supported by the second tuning fork-type vibrator. In addition, the first end of the sixth support member is supported by the second tuning fork vibrator. Thus, an optical reflecting element is created whose two sides are supported by two support members.

Preferably, the second support member is connected to the first arm of the first tuning fork vibrator, and the third support member is connected to the second arm of the first tuning fork vibrator. Alternatively or additionally, the fifth support member is preferably connected to the third arm of the second tuning fork vibrator, and the sixth support member is connected to the fourth arm of the second tuning fork vibrator.

Preferably, the second and third support members extend substantially parallel to the axis of rotation, particularly in the longitudinal direction of the second and third support members. Alternatively or additionally, the fifth and sixth support members preferably extend substantially parallel to the axis of rotation, particularly in the longitudinal direction of the fifth and sixth support members. Here, the second and third support members are particularly configured as linear torsion bars. Alternatively or additionally, the fifth and sixth support members are particularly configured as linear torsion bars. Using such torsion bars as supports embodies the simplest structure for suspending the mirror element.

Preferably, the second and third support members extend substantially obliquely to the axis of rotation, particularly in the longitudinal direction of the second and third support members. Alternatively or additionally, the fifth and sixth support members extend substantially obliquely to the axis of rotation, particularly in the longitudinal direction of the fifth and sixth support members. Here, the second and third support members are configured as particularly curved spring elements. Alternatively or additionally, the fifth and sixth support members are configured as particularly curved spring elements. The meandering of the curved springs offers various possibilities for optimizing the stress distribution in the springs. In addition, the dynamic deformation of the mirror can be optimized by freely selecting the position of the spring ends on the mirror element. Preferably, the particularly curved spring elements are connected to the mirror element at an oblique angle to the axis of rotation, particularly in the range of 20° to 90°. Due to the large spring length, a lower mechanical tension can be obtained at the same frequency by appropriately selecting the spring width. Particularly preferably, the spring element is connected to the mirror element at an oblique angle of approximately 45° or approximately 90° relative to the axis of rotation, which can further reduce dynamic deformation.

Preferably, the second and third support members extend on opposite sides of the rotation axis, particularly in plan view. Alternatively or additionally, the fifth and sixth support members extend on opposite sides of the rotation axis, particularly in plan view.

Preferably, the second support member is connected to a first partial surface of the mirror element, in particular a first edge surface of the mirror element. Here, the third support member is connected to a second partial surface of the mirror element different from the first partial surface, in particular a second edge surface of the mirror element. Alternatively or additionally, the fifth support member is connected to a third partial surface of the mirror element, in particular a third edge surface of the mirror element. Here, the sixth support member is connected to a fourth partial surface of the mirror element different from the third partial surface, in particular a fourth edge surface of the mirror element.

Preferably, the second, third, fifth, and sixth stabilizing members extend at least partially below the mirror element to stabilize the mirror element. Therefore, the reflecting surface of the mirror element is not reduced. Preferably, the second, third, fifth, and sixth stabilizing members are positively connected to the mirror element. Preferably, the second, third, fifth, and sixth stabilizing members are configured as particularly rigid beams. Preferably, the second, third, fifth, and sixth stabilizing portions meet at a common point, which is particularly configured as the center point of the mirror element. Preferably, the second support member and the second stabilizing portion are configured integrally. Similarly, preferably, the third support member and the third stabilizing portion are configured integrally. Preferably, the fifth support member and the fifth stabilizing member are similarly configured integrally. Similarly, preferably, the sixth support member and the sixth stabilizing member are configured integrally.

Preferably, the second and third support members have a symmetrical arrangement with respect to the axis of rotation. Alternatively or additionally, the fifth and sixth support members have a symmetrical arrangement with respect to the axis of rotation.

Preferably, the optical reflecting element further comprises first and second actuators, particularly first and second piezoelectric actuators. Here, the first actuator is arranged on the upper and/or lower surface of the first arm of the first tuning fork vibrator. The second actuator is arranged on the upper and/or lower surface of the second arm of the first tuning fork vibrator. Alternatively or additionally, the optical reflecting element further comprises third and fourth actuators, particularly third and fourth piezoelectric actuators. The third actuator is arranged on the upper and/or lower surface of the third arm of the second tuning fork vibrator. The fourth actuator is arranged on the upper and/or lower surface of the fourth arm of the second tuning fork vibrator. The actuators, particularly piezoelectric actuators, function as driving elements for the optical reflecting element. A piezoelectric layer on the arm of the tuning fork vibrates the arm, and the vibration is transmitted to the mirror via the second, third, fifth, and/or sixth support members. At this time, the mirror vibrates in the same phase as the arm, which may correspond to a relatively low resonant frequency, or the arm may vibrate in antiphase, or may correspond to a relatively high resonant frequency.

Preferably, the second and third support members are configured differently from the fifth and sixth support members.

A further subject of the present invention is a microprojection device comprising the above-mentioned optical reflection element. The microprojection device is used to project an image generated by means of an optical unit, in particular a laser unit, onto a projection unit, in particular a screen, and is configured in particular as a microprojector.

1 is an optical reflecting element according to a first embodiment. 10 is an optical reflecting element according to a second embodiment. Micro projection device.

Figure 1 is a schematic diagram of an optical reflecting element 1a according to the first embodiment, viewed from below. Here, the optical reflecting element 1a, configured as a micromirror device, has supports 2a and 2b, which in this embodiment are configured as frame elements for the optical reflecting element 1a, and only a portion of them is shown here for simplicity. The support 2a has a first support member 3a, the first end 19a of which is supported by the support 2a. Furthermore, the optical reflecting element 1a has a first tuning-fork vibrator 5a having a first arm 4a and a second arm 4b. The first arm 4a and the second arm 4b are supported by the second end 19b of the first support member 3a. The first tuning-fork vibrator 5a is configured to torsionally vibrate with the first support member 3a around a rotation axis 22. Furthermore, the reflecting element 1a has a second support member 7a and a third support member 7b. The optical reflecting element also has a mirror element 10. In this embodiment, the mirror element 10 is made of silicon. The mirror element 10 is supported by the second end 14a of the second support member 7a and the second end 14b of the third support member 7b so that the mirror element 10 repeatedly rotates and vibrates around the rotation axis 22. The first end 8a of the second support member 7a and the first end 8b of the third support member 7b are supported by the first tuning-fork vibrator 5a.

The optical reflecting element 1a has a fourth support member 3b of the support body 2b, and its first end 20a is supported by the support body 2b. The optical reflecting element 1a also has a second tuning-fork vibrator 6a with a third arm 4c and a fourth arm 4d. The third arm 4c and the fourth arm 4d of the second tuning-fork vibrator 6a are supported by the second end 20b of the fourth support member 3b. The second tuning-fork vibrator 6a with the fourth support member 3b is configured to torsionally vibrate around the rotation axis 22. The optical reflecting element 1a also has a fifth support member 11b and a sixth support member 11a. The mirror element 10 is similarly supported by the second end 15b of the fifth support member 11b and the second end 15a of the sixth support member 11a so that the mirror element 10 repeatedly rotationally vibrates around the rotation axis 22. The first end 12b of the fifth support member 11b and the first end 12a of the sixth support member 11a are supported by the second tuning fork vibrator 6a.

The second support member 7a is connected to the first arm 4a of the first tuning fork vibrator 5a, and the third support member 7b is connected to the second arm 4b of the first tuning fork vibrator 5a. Similarly, the fifth support member 11b is connected to the third arm 4c of the second tuning fork vibrator 6a, and the sixth support member 11a is connected to the fourth arm 4d of the second tuning fork vibrator 6a.

In this first embodiment, the second support member 7a, the third support member 7b, the fifth support member 11b, and the sixth support member 11a are configured as linear torsion bars, with longitudinal axes 24a, 24b, 25a, and 25b of the torsion bars extending substantially parallel to the rotation axis 22. The second stabilizing member 26a, the third stabilizing member 26b, the fifth stabilizing member 27b, and the sixth stabilizing member 27a extend below the mirror 10 to stabilize the mirror 10 and converge at the center of the mirror 10. The stabilizing members 26a, 26b, 27a, and 27b are form-connected to the underside of the mirror element 10. In this embodiment, the second support member 7a and the second stabilizing member 26a are configured integrally. Similarly, the third support member 7b and the third stabilizing member 26b are configured integrally. Similarly, the fifth support portion 11b and the fifth stabilizing portion 27b are integrally configured. Similarly, the sixth support portion 11a and the sixth stabilizing portion 27a are integrally configured.

The second support member 7a, the third support member 7b, and the fifth support member 11b and the sixth support member 11a extend on opposing surfaces of the rotation shaft 22.

The second end 14a of the second support member 7a and the first partial surface 9a of the mirror element 10 are connected to each other. Here, the first partial surface 9a is configured as the first edge surface of the mirror element 10. Similarly, the second end 14b of the third support member 7b and the second partial surface 9b of the mirror element 10 are connected to each other. Here, the first partial surface 9a is configured differently from the second partial surface 9b. The first partial surface 9a and the second partial surface 9b are arranged mirror-symmetrically with respect to the rotation axis 22. Here, the second partial surface 9b is configured as the second edge surface of the mirror element 10.

The second end 15b of the fifth support member 11b and the third partial surface 13b of the mirror element 10 are connected to each other. Here, the third partial surface 13b is configured as the third edge surface of the mirror element 10. The second end 15a of the sixth support member 11a and the fourth partial surface 13a of the mirror element 10 are similarly connected to each other. Here, the third partial surface 13b is different from the fourth partial surface 13a. The third partial surface 13b and the fourth partial surface 13a are arranged mirror-symmetrically with respect to the rotation axis 22. Here, the third partial surface 13b is configured as the fourth edge surface of the mirror element 10.

The second support member 7a and the third support member 7b are arranged symmetrically with respect to the rotation axis 22. Similarly, the fifth support member 11b and the sixth support member 11a are arranged symmetrically with respect to the rotation axis 22.

To drive the optical reflecting element 1a, the optical reflecting element 1a has a first actuator 16a, a second actuator 16b, a third actuator 16c, and a fourth actuator 16d, which are configured as piezoelectric actuators here and are arranged on the upper surfaces of the arms 4a, 4b, 4c, and 4d of the first tuning fork vibrator 5a and the second tuning fork vibrator 6a, respectively.

Figure 2 is a schematic diagram of a second embodiment of the optical reflecting element 1b, viewed from below. Unlike the first embodiment, the second support member 30a, the third support member 30b, the fifth support member 31b, and the sixth support member 31a are configured as curved spring elements. The second support member 30a, the third support member 30b, the fifth support member 31b, and the sixth support member 31a extend in their respective longitudinal directions 38a, 38b, 39a, 39b, 41a, 41b, 42a, and 42b, approximately obliquely relative to the axis of rotation 22. The curved spring elements, the second support member 30a, the third support member 30b, the fifth support member 31b, and the sixth support member 31a, are connected to the mirror element 10 at oblique angles 40a, 40b, 40c, and 40d of approximately 30° relative to the axis of rotation 22 in this embodiment. Alternatively, the spring element may be connected to the mirror element 10 at an oblique angle of, for example, approximately 45° or approximately 90° relative to the axis of rotation 22.

The second end 49a of the second support 30a and the first partial surface 37a of the mirror element 10 are connected to each other. Here, the first partial surface 37a is configured as the first edge surface of the mirror element 10. Similarly, the second end 49b of the third support 30b and the second partial surface 37b of the mirror element 10 are connected to each other. Here, the first partial surface 37a is configured differently from the second partial surface 37b. The first partial surface 37a and the second partial surface 37b are arranged mirror-symmetrically with respect to the rotation axis 22. Here, the second partial surface 37b is configured as the second edge surface of the mirror element 10.

The second end 49d of the fifth support 31b and the third partial surface 36b of the mirror element 10 are connected to each other. Here, the third partial surface 36b is configured as the third edge surface of the mirror element 10. Similarly, the second end 49c of the sixth support 31a and the fourth partial surface 36a of the mirror element 10 are connected to each other. Here, the third partial surface 36b is configured differently from the fourth partial surface 36a. The third partial surface 36b and the fourth partial surface 36a are arranged mirror-symmetrically with respect to the rotation axis 22. Here, the third partial surface 36b is configured as the fourth edge surface of the mirror element 10.

Below the mirror element 10, second stabilizing member 33a, third stabilizing member 33b, fifth stabilizing member 33d, and sixth stabilizing member 33c extend and converge at a common center point of the mirror element 10 to stabilize the mirror element 10. In this embodiment, the second support member 30a and the second stabilizing member 33a are integrally formed. Similarly, the third support member 30b and the third stabilizing member 33b are integrally formed. Similarly, the fifth support member 31b and the fifth stabilizing member 33d are integrally formed. Similarly, the sixth support member 31a and the sixth stabilizing member 33c are integrally formed.

Figure 3 shows a schematic representation of a micro-projection device 50. Here, the micro-projection device 50 comprises an optical unit 51 configured as a laser unit and transmitting a light beam 52 of at least one wavelength to an optical reflecting element 53. The optical reflecting element 53, which may be configured according to the embodiment of Figures 1 and 2, is further configured to deflect the light beam 52 emitted by the optical unit 51 in the form of a deflected light beam 54 to a projection unit 55. The projection unit 55 is particularly configured as a screen.

Claims (18)

An optical reflecting element (1a, 1b, 53),
a support (2a, 2b) comprising a first support member (3a), the first end (19a) of which is supported by said support (2a, 2b);
a first tuning fork vibrator (5a) having a first arm (4a) and a second arm (4b), the first arm (4a) and the second arm (4b) of the first tuning fork vibrator (5a) being supported by a second end (19b) of the first support member (3a);
The first tuning-fork vibrator (5a) having the first support member (3a) vibrates torsionally around a rotation axis (22), and the optical reflecting element (1a, 1b, 53) further comprises at least
a second support member (7a, 30a),
a third support member (7b, 30b),
a mirror element (10),
The mirror element (10) is an optical reflecting element (1a, 1b, 53) supported by a second end (14a, 49a) of the second support member (7a, 30a) and a second end (14b, 49b) of the third support member (7b, 30b) so that the mirror element (10) repeatedly rotates and oscillates around the common rotation axis (22),
a first end (8a) of the second support member (7a, 30a) is supported by the first tuning-fork vibrator (5a), and a first end (8b) of the third support member (7b, 30b) is supported by the first tuning-fork vibrator (5a);
the second end (14a, 49a) of the second support member (7a, 30a) and the second end (14b, 49b) of the third support member (7b, 30b) have a width greater than the width of the second support member (7a, 30a) and the third support member (7b, 30b) along the short direction, respectively , and are connected to an edge surface on the back side opposite to the reflecting surface of the mirror element (10);
stabilizing members (33a, 33b) connected to the second end (14a, 49a) of the second support member (7a, 30a) and the second end (14b, 49b) of the third support member (7b, 30b), respectively, have widths substantially equal to widths of the second support member (7a, 30a) and the third support member (7b, 30b) along the short direction, and extend from the edge side of the back surface of the mirror element (10) toward the center side;
An optical reflecting element (1a, 1b, 53) characterized in that 2. The optical reflecting element (1a, 1b, 53) according to claim 1,
The optical reflecting element (1a, 1b, 53) is configured as a micromirror device. 3. The optical reflecting element (1a, 1b, 53) according to claim 1 or 2,
The optical reflecting element (1a, 1b, 53) is characterized in that the support (2a, 2b) is a frame element. a fourth support member (3b) of said support (2a, 2b), the first end (20a) of said fourth support member (3b) being supported by said support (2a, 2b);
a second tuning fork vibrator (6a) having a third arm (4c) and a fourth arm (4d), wherein the third arm (4c) and the fourth arm (4d) of the second tuning fork vibrator (6a) are supported by a second end (20b) of the fourth support member (3b);
The second tuning-fork vibrator (6a) having the fourth support member (3b) vibrates torsionally around the rotation axis (22), and the optical reflecting element (1a, 1b, 53)
a fifth support member (11b, 31b),
a sixth support member (11a, 31a),
The mirror element (10) is supported by second ends (15b, 49d) of the fifth support members (11b, 31b) and second ends (15a, 49c) of the sixth support members (11a, 31a) so that the mirror element (10) repeatedly rotates and vibrates around the common rotation axis (22), a first end (12b) of the fifth support members (11b, 31b) is supported by the second tuning-fork vibrator (6a), and a first end (12a) of the sixth support members (11a, 31a) is supported by the second tuning-fork vibrator (6a);
An optical reflecting element (1a, 1b, 53) described in any one of claims 1 to 3, characterized in that the second end (15b, 49d) of the fifth support member (11b, 31b) and the second end (15a, 49c) of the sixth support member (11a, 31a) have a width greater than the width along the short direction of the fifth support member (11b, 31b) and the sixth support member (11a, 31a), respectively. The optical reflecting element (1a, 1b, 53) of claim 4, characterized in that the second support member (7a, 30a) is connected to the first arm (4a) of the first tuning fork vibrator (5a), the third support member (7b, 30b) is connected to the second arm (4b) of the first tuning fork vibrator (5a), and/or the fifth support member (11b, 31b) is connected to the third arm (4c) of the second tuning fork vibrator (6a), and the sixth support member (11a, 31a) is connected to the fourth arm (4d) of the second tuning fork vibrator (6a). The optical reflecting element (1a, 1b, 53) according to claim 4 or 5, characterized in that the second support member (7a, 30a) and the third support member (7b, 30b) extend substantially parallel to the rotation axis (22) in the longitudinal direction (24a, 24b, 41a, 41b, 42a, 42b) of the second support member (7a, 30a) and the third support member (7b, 30b), and/or the fifth support member (11b, 31b) and the sixth support member (11a, 31a) extend substantially parallel to the rotation axis (22) in the longitudinal direction (25a, 25b, 38a, 38b, 39a, 39b) of the fifth support member (11b, 31b) and the sixth support member (11a, 31a). The optical reflecting element (1a, 1b, 53) described in claim 6, characterized in that the second support member (7a, 30a) and the third support member (7b, 30b), and/or the fifth support member (11b, 31b) and the sixth support member (11a, 31a) are configured as linear torsion bars. The optical reflecting element (1a, 1b, 53) according to any one of claims 4 to 7, characterized in that the second support member (7a, 30a) and the third support member (7b, 30b) extend approximately obliquely with respect to the rotation axis (22) in the longitudinal direction (24a, 24b, 41a, 41b, 42a, 42b) of the second support member (7a, 30a) and the third support member (7b, 30b), and/or the fifth support member (11b, 31b) and the sixth support member (11a, 31a) extend approximately obliquely with respect to the rotation axis (22) in the longitudinal direction (25a, 25b, 38a, 38b, 39a, 39b) of the fifth support member (11b, 31b) and the sixth support member (11a, 31a). The optical reflecting element (1a, 1b, 53) according to claim 8, characterized in that the second support member (7a, 30a) and the third support member (7b, 30b), and/or the fifth support member (11b, 31b) and the sixth support member (11a, 31a) are configured as curved spring elements. An optical reflecting element (1a, 1b, 53) as described in claim 9, characterized in that the spring element is connected to the mirror element (10) at an oblique angle (40a, 40b, 40c, 40d) relative to the rotation axis (22), in the range of 20° to 90°. An optical reflecting element (1a, 1b, 53) according to any one of claims 4 to 10, characterized in that the second support member (7a, 30a) and the third support member (7b, 30b) extend on opposite sides of the rotation axis (22), and/or the fifth support member (11b, 31b) and the sixth support member (11a, 31a) extend on opposite sides of the rotation axis (22). The second support member (7a, 30a) is connected to a first edge surface of the rear side of the mirror element (10), which is a first partial surface (9a, 37a) of the mirror element (10), the third support member (7b, 30b) is connected to a second edge surface of the rear side of the mirror element (10), which is a second partial surface (9b, 37b) of the mirror element (10) different from the first partial surface (9a, 37a), and/or the fifth support member (11b, 31b) is connected to a front edge surface of the mirror element (10), which is a second partial surface (9b, 37b) of the mirror element (10), which is different from the first partial surface (9a, 37a). The optical reflecting element (1a, 1b, 53) according to any one of claims 4 to 11, characterized in that the sixth support member (11a, 31a) is connected to a third edge surface on the rear side of the mirror element (10), which is a third partial surface (13b, 36b) of the mirror element (10), and the sixth support member (11a, 31a) is connected to a fourth edge surface on the rear side of the mirror element (10), which is a fourth partial surface (13a, 36a) of the mirror element (10) different from the third partial surface (13b, 36b). 13. The optical reflecting element (1a, 1b, 53) according to any one of claims 1 to 12, characterized in that a second stabilizing element (26a), a third stabilizing element (26b) , a fifth stabilizing element (27b) and a sixth stabilizing element (27a) extend from the edge side towards the center side of the rear surface of the mirror element (10) to stabilize the mirror element (10). An optical reflecting element (1a, 1b, 53) according to any one of claims 4 to 12, characterized in that the second support member (7a, 30a) and the third support member (7b, 30b) have a symmetrical arrangement with respect to the rotation axis (22), and/or the fifth support member (11b, 31b) and the sixth support member (11a, 31a) have a symmetrical arrangement with respect to the rotation axis (22). The optical reflecting element (1a, 1b, 53) further has a first actuator (16a) and a second actuator (16b), the first actuator (16a) being arranged on the upper and/or lower surface of the first arm (4a) of the first tuning fork vibrator (5a), the second actuator (16b) being arranged on the upper and/or lower surface of the second arm (4b) of the first tuning fork vibrator (5a), and/or the optical reflecting element (1a, 1b, 53) further has a third The optical reflecting element (1a, 1b, 53) according to any one of claims 4 to 12 or claim 14, further comprising an actuator (16c) and a fourth actuator (16d), wherein the third actuator (16c) is arranged on the upper and/or lower surface of the third arm (4c) of the second tuning fork vibrator (6a), and the fourth actuator (16d) is arranged on the upper and/or lower surface of the fourth arm (4d) of the second tuning fork vibrator (6a). The optical reflecting element (1a, 1b, 53) of claim 15, wherein the first actuator (16a) and the second actuator (16b) are first and second piezoelectric actuators, and the third actuator (16c) and the fourth actuator (16d) are third and fourth piezoelectric actuators. An optical reflecting element (1a, 1b, 53) according to any one of claims 4 to 12 or any one of claims 14 to 16, characterized in that the second support member (7a, 30a) and the third support member (7b, 30b) are configured differently from the fifth support member (11b, 31b) and the sixth support member (11a, 31a). A microprojection device (50) comprising an optical reflection element (1a, 1b, 53) according to any one of claims 1 to 17.