LENS MODULE

Abstract

A lens module (38) is provided that has a module housing (42) having a base (44) and a side wall (46), an adaptive lens (40) variable in its focal length in the module housing (42), and a pressing element (48) to hold the adaptive lens (40) in the module housing (42), The pressing element has a wave spring (48) here.

Claims

1. A lens module that has a module housing having a base and a side wall, an adaptive lens variable in its focal length in the module housing, and a pressing element to hold the adaptive lens in the module housing, wherein the pressing element has a wave spring.

2. The lens module in accordance with claim 1, wherein the adaptive lens is one of a gel lens and a liquid lens.

3. The lens module in accordance with claim 1, wherein the adaptive lens has at least one electrode and the lens module has a connection lead to contact the electrode from outside the module housing.

4. The lens module in accordance with claim 3, wherein the connection lead is a flexible cable.

5. The lens module in accordance with claim 1, that has a temperature sensor.

6. The lens module in accordance with claim 5, wherein the temperature sensor is configured as a resistor on the connection lead.

7. The lens module in accordance with claim 1, that has an insulation element between the adaptive lens and the wave spring.

8. The lens module in accordance with claim 7, wherein the insulation element is simultaneously configured as an assembly element for inserting the adaptive lens into the module housing.

9. The lens module in accordance with claim 1, that has a further pressing element for pressing the wave spring onto the adaptive lens.

10. The lens module in accordance with claim 1, that has an insulation element between the adaptive lens and the wave spring, as well as a further pressing element for pressing the wave spring onto the adaptive lens, wherein the further pressing element, the wave spring, the insulation element, the adaptive lens, and the base are arranged above on another in this order.

11. The lens module in accordance with claim 10, wherein the insulation element is simultaneously configured as an assembly element for inserting the adaptive lens into the module housing.

12. An objective having a lens module, the lens module having a module housing having a base and a side wall, an adaptive lens variable in its focal length in the module housing, and a pressing element to hold the adaptive lens in the module housing, wherein the pressing element has a wave spring, the objective further having a second spring that presses the lens module onto the objective.

13. The objective in accordance with claim 12, wherein the second spring is configured as a multiturn spring.

14. The objective in accordance with claim 12, wherein a clearance fit for a rotation of a connection lead of the lens module into the correct position is provided between the lens module and the objective.

15. The objective in accordance with claim 12, that has an extraneous light filter that is arranged above the second spring.

16. An optoelectronic sensor having at least one of a light transmitter and a light receiver as well as an objective disposed upstream of the light transmitter and/or the light receiver, the objective having a lens module, the lens module having a module housing having a base and a side wall, an adaptive lens variable in its focal length in the module housing, and a pressing element to hold the adaptive lens in the module housing, wherein the pressing element has a wave spring, the objective further having a second spring that presses the lens module onto the objective.

17. The optoelectronic sensor in accordance with claim 16, wherein the objective is pressed toward a front screen of the sensor by the second spring.

Description

[0027] The invention will be explained in more detail in the following also with respect to further features and advantages by way of example with reference to embodiments and to the enclosed drawing. The Figures of the drawing show in:

[0028] FIG. 1 a schematic sectional representation of an optoelectronic sensor with an adaptive lens in the reception optics;

[0029] FIG. 2 a schematic sectional representation of an optoelectronic sensor with an adaptive lens in the transmission optics;

[0030] FIG. 3 a schematic representation of an adaptive lens in accordance with the invention;

[0031] FIG. 4 a sectional representation of a lens module;

[0032] FIG. 5 a cut-away three-dimensional representation of the lens module in accordance with FIG. 4;

[0033] FIG. 6 a three-dimensional representation of the lens module in accordance with FIGS. 4 and 5; and

[0034] FIG. 7 a three-dimensional representation of the lens module in accordance with FIGS. 4 to 6 together with an installed lens module at the objective.

[0035] FIG. 1 shows a schematic sectional representation of an optoelectronic sensor for detecting object information from a monitored zone 12. An image sensor 16, for example a CCD or CMOS chip, generates recordings of the monitored zone 12 via a reception optics 14. The image data of these shots are forwarded to a control and evaluation unit 18.

[0036] The reception optics 14 has an adaptive lens whose focal length can be changed by an electronic control of the control and evaluation unit 18. FIG. 1 shows by dashed lines by way of example an alternative focal length setting and the functional principle of a conceivable design of the adaptive lens will be explained in more detail below with reference to FIG. 3. A temperature sensor 20 is connected to the control and evaluation unit and is arranged such that it is at least indirectly in thermal connection with the adaptive lens.

[0037] FIG. 2 shows a further embodiment of the optoelectronic sensor 10. This embodiment differs from the embodiment shown in FIG. 1 by a light transmitter 22 having a transmission optics 24. The adaptive lens is now part of the transmission optics 24; the reception optics 14 has a fixed focal position. A temperature sensor 20 as in FIG. 1 is also possible for the adaptive lens of the transmission optics 24 in the embodiment of FIG. 2. Mixed forms of the embodiments in accordance with FIG. 1 and FIG. 2 are furthermore conceivable in which the reception optics 14 and the transmission optics 24 have an adaptive lens or a common optics is provided having an adaptive lens for the image sensor 16 and for the light transmitter 22, with the adaptive lens in turn being able to have a temperature sensor 20. In addition, a light transmitter 22 having a transmission optics without an adaptive lens can be added in FIG. 1, for example to illuminate the monitored zone 12 or to generate a light signal whose time of flight is determined for the distance measurement.

[0038] FIGS. 1 and 2 are therefore schematic diagrams that are representative for a plurality of sensors. The sensor 10 in accordance with FIG. 1 is, for example, a camera with a variable focus that is inter alia suitable in a variety of applications for the inspection and measurement of objects, preferably in a stationary installation at a conveyor system that moves the objects through the monitored zone 12. A barcode scanner or a camera-based code reader arises by the use of signal processing or image processing known per se for the reading of codes. The image sensor 16 can have a linear arrangement or a matrix arrangement of pixels. In further embodiments, a different light receiver instead of the image sensor 16 is used, for example a photodiode or an APD (avalanche photodiode). The latter is, for example, used in a light sensor, in particular a distance measuring light sensor, or in a laser scanner.

[0039] The light transmitter 22 can also satisfy a variety of functions. For example, with the aid of the transmission optics 24, a specific illuminated monitored zone 12 is set, a sharp contrast pattern, a sharp target pattern to mark a recording or reading zone, or a sharp light spot is projected at a specific distance. Such different sensors 10 as a camera-based code reader, a code scanner, or a 3D camera are thus conceivable.

[0040] FIG. 3 shows the adaptive lens of the reception optics 14 or of the transmission optics 24 in an exemplary embodiment as a liquid lens 26 after the electrowetting effect. It is here only a question of the functional principle; the specific design and construction shape may differ. The operation will be explained with reference to this liquid lens 26, but the invention also comprises other adaptive lenses, for example those having a liquid chamber and having a membrane which covers it and whose curvature is varied by pressure on the liquid, or having lenses with a gel-like, optically transmitting material which is mechanically deformed by an actuator.

[0041] The actively tunable liquid lens 26 has two transparent, non-miscible liquids 28, having different refractive indices and having the same densities. The shape of the liquid boundary layer 32 between the two liquids 28, 30 is used for the optical function. The activation is based on the principle of electrowetting which shows a dependence of the surface tension or of the boundary surface tension on the applied electrical field. It is therefore possible to vary the shape of the boundary layer 32 and thus the optical properties of the liquid lens 26, by an electric control at a terminal 34, whereby corresponding voltages are applied to an electrode 36. In addition to an adjustment of the focal length, a tilting is also conceivable for which purpose then at least one further electrode is provided at the liquid lens 26.

[0042] FIGS. 4 to 6 show a lens module 38 having an adaptive lens 40 in a sectional representation, a cut-away three-dimensional representation, and a three-dimensional representation from the outside. The adaptive lens 40 can be a liquid lens, as described with respect to FIG. 3, or can use a different principle for the adjustment of the focal length. The adaptive lens 40 is accommodated in a module housing 42 having a base 44 and a side wall 46. A wave spring 48 presses the adaptive lens 40 downwardly toward the base 44. The wave spring 48 is in turn pressed from above by a pressing ring 50. An insulation element 52 is arranged between the wave spring 48 and the adaptive lens 40.

[0043] As can in particular be recognized in the three-dimensional representations of FIGS. 5 and 6, said components are cylindrical or are designed as a ring and are at least approximately shaped as rotational bodies about the optical axis.

[0044] Electrodes 54a-b of the adaptive lens 40 are contacted by a connection lead 56 designed as a flexible cable so that the electrodes 54a-b can be controlled laterally from outside the lens module 38. An optional resistor 58 on the connection lead 56 is shown in FIG. 5 that serves as a temperature sensor.

[0045] In accordance with the invention, the adaptive lens 40 is spring loaded by the wave spring 48, i.e. is pressed toward the base 44 by a defined force. It thus replaces the conventional tolerance-critical O ring and avoids the disadvantages associated therewith. The wave spring 48 is preferably of metal and is, for example, a precision wave spring of a ball bearing producer. The advantage comprises the characteristic line of the wave spring 48 extending almost linearly and practically no fluctuations of the exerted force occurring over the total industrial temperature range. An electrical insulation is required between the electrodes 54a-b of the adaptive lens 40 for a metal wave spring 48 that is electrically conductive in contrast to a conventional O ring. The insulation element 52 that is shaped as a ring and can simultaneously be used as an installation aid satisfies this function. The thickness of the press ring 50 is preferably configured such that, on the installation of the lens module, its front surface is pressed as a block to the module housing 42 and the correct force of the wave spring 48 on the adaptive lens is thus automatically set in the typical range <10 N.

[0046] FIG. 7 shows a lens module 38 installed at an objective in a three-dimensional representation. The lens module 38 is arranged on an objective 60 or on its connection piece 62 (barrel). The designation objective 60 is a little imprecise since the combination of the objective 60 and of the lens module 38 can also be understood as an objective. No further distinction is made here; the objective 60 anyway has one or more lenses that cooperate with the adaptive lens 40 of the lens module 38 in the manner of an objective.

[0047] For the module integration, the lens module 38 is placed onto the connection piece 62 and is pressed on via a multiturn spring 64 and is thus held in position. The multiturn spring 64 is pressed and thereby tensioned on the opposite side toward a front screen 66, for example of an optoelectronic sensor 10 or, alternatively to the front screen 66, to a different element. An optional extraneous light protection or an extraneous light filter 68 can be arranged therebetween.

[0048] The multiturn spring 64 can be configured such that it is suitable for different objective distances or objectives 60 and a spring force is respectively produced on the adaptive lens 40 in the desired range. An exact alignment of the adaptive lens 40 at the optical axis of the objective 60 takes place via a clearance fit between the objective 60 or the connection piece 62 and a module housing 42 of the lens module 38. The assembly of the lens module 38 on the objective 60 can take place without tools. The electrodes 54a-b of the adaptive lens 40 are contacted by the connection lead 56. The lens module 38 is placed on and the first the multiturn spring 64 and subsequently the cover of the sensor 10 with the front screen 66 and the extraneous light filter 68 are placed on. The connection lead 56 is rotated into the correct position by the clearance fit in assembly.