DE102018132699B4 - Sight system and adjustable lens system for a sight system - Google Patents

Abstract

A vision system that compensates for the drift of a lens assembly (LL1, LL2, VL), comprising: an image sensor (130, 230, 910, 1010) operatively connected to a vision system processor (140); a lens assembly (LL1, LL2, VL) that changed their shape or refractive index; anda fixed lens assembly configured to attenuate an action of the adjustable lens assembly (LL1, LL2, VL) over a predetermined operating range of the object, the fixed lens assembly and the adjustable lens assembly (LL1, LL2, VL) being part of an overall lens assembly that light onto the image sensor (130, 230, 910, 1010), wherein an overall optical power of the overall lens assembly is primarily defined by the optical power of the fixed lens assembly, so that the drift of the adjustable lens assembly (LL1, LL2, VL) is compensated, characterized in that the fixed lens assembly comprises: (a) a front lens (940) having a front concave surface (942) and a rear convex surface (944) and a central biconvex lens (952) spaced from the front lens (940), or (b) a front biconvex lens (1040) and a rear stacked lens assembly with a front positive lens, a central biconcave lens (1060) and a rear positive lens, or (c) a front plano-concave lens and a front negative lens (1442), a central stacked lens assembly with a biconvex lens (1446) and a plano-convex lens (1448), and a rear biconvex lens (1454) and a rear positive lens (1452), or (d) one anterior plano-convex lens and an anterior positive lens as well as a posterior positive lens (1552) and an posterior negative lens (1556), or (e) an anterior stacked lens assembly with a biconvex lens (1642) and a biconcave lens (1648) as well as a posterior posterior convex lens (1654) Negative lens (1656).

Description

RELATED APPLICATION

The present application is based on a partial continuation of the also filed US patent application with the serial number 14 / 271,148, entitled SYSTEM AND METHOD FOR REDUCTION OF DRIFT IN A VISION SYSTEM VARIABLE LENS on June 5, 2014.

FIELD OF THE INVENTION

The present application relates to cameras that are used in machine vision, and more particularly to lens assemblies with automatic focusing.

BACKGROUND OF THE INVENTION

Vision systems for carrying out measurements, tests, object alignment processes and / or decoding symbol sets (e.g. bar codes or more simply "ID" identifiers) are used in a wide range of applications in numerous industries. These systems are essentially based on the use of an image sensor, which captures images (usually one, two or three-dimensional grayscale or color images) of the object or object and processes the images captured in this way by means of a built-in or activated vision system processor. The processor generally includes both processing hardware and non-volatile computer readable program instructions that perform one or more vision system processes to produce a desired output based on the processed image information. This image information is generally provided within an arrangement of image pixels, each of which has different colors and / or intensities. In the example of an ID reader, the user or the automated process captures an image of an object, assuming that it contains one or more ID identifiers. The image is processed to recognize ID features which are then decoded by a decoding process and / or processor to obtain the information contained therein (e.g. alphanumeric data) which is encoded in the pattern of the ID identifier.

Often, a vision system camera includes an internal processor and other components that enable it to operate as a stand-alone unit, with desired output data (e.g. decoded symbol information) being provided to a downstream process, such as a computer system for inventory tracking or a logistics application .

An example lens design that may be desirable in certain vision system applications is the auto focus assembly (auto focus assembly). For example, such an autofocus lens can be simplified by a type of “adjustable lens” assembly (defined below), also known as a so-called liquid lens assembly. One form of liquid lens sold by the French company Varioptic uses two liquids of the same density - oil as an insulator and water as a conductor. By changing the voltage that is passed through the lens by a surrounding circuit, a change in the degree of curvature of the liquid / liquid interface can be achieved, which in turn leads to a change in the focal length of the lens. The main advantages that speak for the use of a liquid lens include the robustness of the lens (it has no mechanically moving parts), its fast response times, its relatively good optical quality and its low energy consumption and small size. The use of a liquid lens can desirably simplify the installation, setup, and maintenance of the vision system because it eliminates the need to manually touch the lens. Compared to other auto focus mechanisms, the liquid lens has extremely fast response times. It is therefore also ideal for applications in which the reading distances change from object to object (from surface to surface) or during the switch from reading an object to reading another object - such as when scanning a moving conveyor belt that contains objects of different sizes / heights (such as shipping boxes). The ability to make a “dynamic” focus adjustment during operation is generally desirable in many vision system applications.

A further development in the field of liquid lens technology has recently been offered by the Swiss company Optotune AG. This lens uses a moveable membrane, the one Liquid reservoir covered to adjust its focal length. A coil exerts pressure to change the shape of the membrane and thus to adjust the lens focus. The coil is moved within a preset range by changing the input current. Different current levels provide different focal lengths for the liquid lens. This lens advantageously provides a larger aperture (e.g. 6 to 10 millimeters) than competing designs (e.g. Varioptic, France) and works faster. Due to the thermal drift and other factors, the calibration and focus setting can generally change during runtime usage and over time. A variety of systems can be provided to compensate for and / or correct the focus changes and other factors. However, such compensation routines may require processing time (in the camera's internal processor), which slows down the overall response time of the lens to reach a new focus. Likewise, such compensation routines (e.g. for thermal drift) can be standardized and not adapted to the individual circumstances of the lens, which makes them less reliable with regard to specific drift conditions that a lens can experience over time. It should be noted that the drift in a liquid lens e.g. B. about 0.15 diopter / ° C (ie for some liquid lenses currently in production and / or for specific, commercially available Varioptic products). Some vision applications require a stability of the optical power of the image converter lens of +/- 0.1 diopter, especially when it comes to recognizing small features from a long distance.

It is recognized that a control frequency of at least about 1000 Hz may also be required to adequately control and maintain the focus of the lens within desired ranges. This places a burden on the vision system processor, which can be based on a DSP or similar architecture. Thus, vision system tasks would suffer if the DSP were continuously engaged in lens control tasks. All these disadvantages make drift compensation a particular challenge in many applications.

From the US 2015/0323709 A1 a vision system with an image sensor, an adjustable lens assembly and a fixed lens assembly is known, which compensates for the drift of the adjustable lens assembly. Another vision system with an image sensor, an adjustable lens assembly and a fixed lens assembly is in the US 2010/0231783 A1 described.

OVERVIEW OF THE INVENTION

The present invention overcomes the disadvantages of the prior art by providing a vision system that is designed to compensate for the optical drift that can occur with certain lens assemblies whose optical power is variable, the change in optical power (and thus the Focal length / the focus distance, focal length = 1 / optical power) by controlling the lens shape or the refractive index of the lens. Such lens assemblies include, among other things, liquid lens arrangements in which, for example, two fluids are used, rather density or a flexible membrane, and which are generally also referred to here as “adjusting lenses” assemblies. The system includes an image sensor that is functionally connected to a vision system processor, and an adjustment lens assembly that is designed to control its focal length (e.g., by the vision processor or another area determining device). A positive lens assembly is designed to mitigate an effect of the adjustable lens assembly over a predetermined operating range of the object as seen from the positive lens assembly. The adjustable lens assembly includes, for example, a liquid lens assembly, and such a liquid lens assembly can basically be changed over a range of approximately 20 diopters. The positive lens assembly and the adjustable lens assembly are, for example, housed together in a lens barrel, which can be removed with respect to a camera housing and the image sensor. The image sensor is located, for example, within the camera housing. Likewise, the vision processor can be located in whole or in part in the camera housing. In one embodiment, the lens barrel has a C-mount lens base and the positive lens assembly includes a double lens that includes a front convex lens and a rear concave lens. The positive lens assembly can define an effective focal length range of 40 millimeters. The usable focal length of the lens (e.g. a double lens) is, for example, between approximately 10 and 100 millimeters. In addition, the adjustable lens assembly (e.g., the liquid lens assembly) is typically adjacent to, but still distant from, a focal point of the positive lens assembly, which is the front or, more typically, the rear / rear focal point of the positive lens assembly can. The distance between the adjustment lens assembly and the focal point can be approximately between 0.1 times and 0.5 times a focal length F of the positive lens assembly. In this way, the positive lens assembly and the adjustable lens assembly are part of an overall lens assembly that focuses light onto the image sensor. The optical strength of the positive lens assembly thus makes an optical strength of the overall lens assembly “ predominantly defined ”- in other words, the magnification / optical power is largely provided by the positive lens assembly, thereby minimizing the drifting effect of the adjustable lens assembly.

In an exemplary embodiment, a drift compensating vision system is provided. The vision system includes an image sensor that is functionally connected to a vision system processor, an adjustable lens assembly, the shape or refractive index of which can be changed, and a fixed lens assembly is designed to weaken an effect of the adjustable lens assembly over an operating range of the object that is predetermined by the positive lens assembly. For purposes of illustration, the adjustable lens assembly includes a liquid lens assembly. This can be positioned between the image sensor and the fixed lens assembly and can be adjustable over a range of approximately 20 diopters. Furthermore, the fixed lens assembly can define a positive optical power. The fixed lens assembly and the adjustable lens assembly are housed, for example, in a lens barrel, which can be removed with respect to a camera assembly housing and the image sensor, wherein the image sensor can be located in the camera assembly housing. The camera module housing can be electrically connected to the adjusting lens module by means of contact surfaces or by a cable module in order to operate and / or control the latter. The fixed lens assembly may include: (a) a front lens with a front concave surface and a rear convex surface and a central biconvex lens spaced from the front lens, or (b) a front biconvex lens and a rear stacked lens assembly with a front positive lens, a central biconcave lens and a rear positive lens, or (c) a front plano-concave lens and a front negative lens, a central stacked lens assembly with a biconvex lens and a plano-convex lens and a rear biconvex lens and a rear positive lens, or (d) a front plano-convex lens and a front positive rear positive lens and a rear negative lens, or (e) a front stacked lens assembly with a biconvex lens and a biconcave lens as well as a rear plano-convex lens and a rear negative lens. In addition, at least one lens of the fixed lens assembly may comprise a polymer material. The fixed lens assembly can, for example, define an effective usable focal length range from about 0.3 meters to about 8 meters. The adjusting lens assembly can also be located adjacent to a focal point of the fixed lens assembly, for example as well. The focal point is either a front focal point or a rear focal point of the fixed lens assembly. In some embodiments, the fixed lens assembly may include a front lens assembly and a rear lens assembly, with the adjustable lens assembly positioned between them and the rear lens assembly being able to define a positive optical power. In addition, in such embodiments, the front lens assembly may have a pair of lenses each having front convex surfaces and rear concave surfaces, and a lens having opposite concave surfaces, and the rear lens assembly may have a lens having opposite convex surfaces. For the sake of illustration, the fixed lens assembly and the adjustable lens assembly are part of an overall lens assembly that focuses light onto the image sensor, wherein an optical power of the overall lens assembly is predominantly defined by an optical power of the fixed lens assembly.

In another exemplary embodiment, an adjustment lens system is provided for a vision system with an image sensor that transmits image data to a processor. The system includes an adjustable lens assembly (e.g., a liquid lens assembly). The system includes a fixed lens assembly with one focus. The adjustment lens assembly is located adjacent to the focal point. The fixed lens assembly and the adjustable lens assembly can be part of an overall lens assembly that focuses light on the image sensor. The optical strength of the overall lens assembly can thus be predominantly defined by the optical strength of the positive lens assembly. For example, the liquid lens assembly can be changed over a range of approximately 20 diopters. In some embodiments, the fixed lens assembly and the adjustable lens assembly are housed in a lens barrel that is removable with respect to a camera assembly housing and the image sensor. The image sensor is located in the camera assembly housing. The camera module housing can be electrically connected to the adjusting lens module by means of contact surfaces or by a cable module in order to operate and / or control the latter. For purposes of illustration, the fixed lens system may include: (a) a front lens with a front concave surface and a rear convex surface and a central biconvex lens spaced from the front lens, or (b) a front biconvex lens and a rear stacked lens assembly with a front positive lens, a central one Biconcave lens and a positive rear lens, or (c) a front plano-concave lens and a front negative lens, a central stacked lens assembly with a biconvex lens and a plano-convex lens and a rear biconvex lens and a rear positive lens, or (d) a front and front plano-convex lens a rear positive lens and a rear negative lens, or (e) a front stacked lens assembly with a biconvex lens and a biconcave lens as well as a rear plano-convex lens and a rear negative lens.

Figure list

• 1 ein Diagramm einer der Veranschaulichung dienenden Sichtsystemanordnung ist, welche eine Sichtsystemkamera mit zugehörigem Sichtprozessor und mit einer Linsenbaugruppe aufweist, die den im zeitlichen Verlauf auftretenden, inhärenten Drift ausgleicht, wobei das Erfassen von Bildern eines Beispielobjekts in einer Situation gemäß einer beispielhaften Ausführungsform gezeigt ist;
• 2 ein Strahlenverfolgungsdiagramm für ein beispielhaftes Linsensystem ist, das eine Verstelllinsenbaugruppe enthält, welche ein Objekt abbildet;
• 3 ein Strahlenverfolgungsdiagramm für ein beispielhaftes Linsensystem mit einer Verstelllinsenbaugruppe ist, wobei eine Positivlinsenbaugruppe entlang der optischen Achse in einer vorbestimmten Entfernung von der Verstelllinsenbaugruppe positioniert ist, um dadurch ein drifttolerantes Linsensystem bereitzustellen;
• 4 einen Seitenquerschnitt einer Linseneinheit darstellt, die eine Verstelllinsenbaugruppe samt Positivlinse enthält und gemäß einer beispielhaften Ausführungsform Drifttoleranz aufweist, wobei die relativen Abmessungen des Linsentubus und der zugehörigen Komponenten gezeigt sind;
• 4A ein Seitenquerschnitt der Linseneinheit aus 4 ist, wobei die relative Komponentenplatzierung entlang der optischen Achse gezeigt ist;
• 5 ein Strahlenverfolgungsdiagramm für die beispielhaften Linseneinheit aus 4 ist, wobei die Abbildung eines Objekts in einem ersten Abstand gezeigt ist;
• 6 ein Strahlenverfolgungsdiagramm für die beispielhafte Linseneinheit aus 4 ist, wobei die Abbildung eines Objekts in einer zweiten Entfernung gezeigt ist, die weiter als die erste Entfernung ist;
• 7 ein Strahlenverfolgungsdiagramm für die beispielhafte Linseneinheit aus 4 ist, wobei die Abbildung eines Objekts in einer ersten Entfernung gezeigt ist;
• 8 ein Diagramm der Beziehung zwischen der Positivlinsenbaugruppe, der Verstelllinsenbaugruppe und dem Brennpunkt der Positivlinse gemäß vorliegenden Ausführungsformen ist;
• 9 ein Diagramm einer Linsenanordnung für ein drifttolerantes Linsensystem ist, bei welchem sich gemäß einer Ausführungsform eine Verstelllinsenbaugruppe zwischen der Optik und dem Bildsensor befindet;
• 10 ein Diagramm einer Linsenanordnung für ein drifttolerantes Linsensystem ist, bei welchem sich gemäß einer Ausführungsform eine Verstelllinsenbaugruppe zwischen zwei vor einem Bildsensor platzierten Optik-Gruppen befindet;
• 11 ein Diagramm einer Linsenanordnung für ein drifttolerantes 12-Millimeter-Linsensystem ist, bei welchem sich gemäß einer anderen Ausführungsform eine Verstelllinsenbaugruppe zwischen der Optik und dem Bildsensor befindet;
• 12 eine Perspektivansicht einer Linsenbaugruppe ist, welche die Linsenanordnung aus 11 enthält;
• 13 ein Seitenquerschnitt der Linsen entlang der Linie 13-13 aus 12 ist;
• 14 ein Diagramm einer Linsenanordnung für ein drifttolerantes 16-Millimeter-Linsensystem ist, bei welchem sich gemäß einer anderen Ausführungsform eine Verstelllinsenbaugruppe zwischen der Optik und dem Bildsensor befindet;
• 14A ein Diagramm der Bildkreise eines rechteckigen Bildsensors, der in dem Sichtsystem gemäß einer Ausführungsform verwendet werden kann;
• 15 ein Diagramm einer Linsenanordnung für ein drifttolerantes 25-Millimeter-Linsensystem ist, bei welchem sich gemäß einer anderen Ausführungsform eine Verstelllinsenbaugruppe zwischen der Optik und dem Bildsensor befindet;
• 16 ein Diagramm einer Linsenanordnung für ein drifttolerantes 35-Millimeter-Linsensystem ist, bei welchem sich gemäß einer anderen Ausführungsform eine Verstelllinsenbaugruppe zwischen der Optik und dem Bildsensor befindet;
• 17 eine Perspektivansicht einer Linsenbaugruppe ist, welche eine Version der Linsenanordnung aus 16 enthält; und
• 18 ein Seitenquerschnitt der Linsen entlang der Linie 18-18 aus 17 ist.

The following description of the invention makes reference to the accompanying drawings, in which:

• 1 FIG. 2 is a diagram of an illustrative vision system arrangement that includes a vision system camera with associated vision processor and with a lens assembly that compensates for the inherent drift over time, wherein capturing images of an example object is shown in a situation according to an example embodiment;
• 2nd FIG. 4 is a ray tracing diagram for an exemplary lens system that includes an adjustable lens assembly that images an object; FIG.
• 3rd FIG. 12 is a ray tracing diagram for an exemplary lens system with a lens assembly wherein a positive lens assembly is positioned along the optical axis a predetermined distance from the lens assembly, thereby providing a drift-tolerant lens system;
• 4th FIG. 3 illustrates a side cross-section of a lens unit that includes an adjustable lens assembly including a positive lens and, according to an exemplary embodiment, has drift tolerance, the relative dimensions of the lens barrel and the associated components being shown;
• 4A a side cross section of the lens unit 4th with relative component placement shown along the optical axis;
• 5 FIG. 8 shows a ray tracing diagram for the exemplary lens unit 4th with the image of an object shown at a first distance;
• 6 FIG. 8 shows a ray tracing diagram for the exemplary lens unit 4th wherein the image of an object is shown at a second distance that is farther than the first distance;
• 7 FIG. 8 shows a ray tracing diagram for the exemplary lens unit 4th with the image of an object shown at a first distance;
• 8th FIG. 14 is a diagram of the relationship between the positive lens assembly, the reticle lens assembly, and the focus of the positive lens according to the present embodiments;
• 9 FIG. 2 is a diagram of a lens arrangement for a drift-tolerant lens system, in which, according to one embodiment, an adjustable lens assembly is located between the optics and the image sensor;
• 10th FIG. 2 is a diagram of a lens arrangement for a drift-tolerant lens system, in which, according to one embodiment, an adjusting lens assembly is located between two optical groups placed in front of an image sensor;
• 11 FIG. 3 is a diagram of a lens arrangement for a drift-tolerant 12 millimeter lens system in which, according to another embodiment, there is an adjustable lens assembly between the optics and the image sensor;
• 12 FIG. 4 is a perspective view of a lens assembly that makes up the lens assembly 11 contains;
• 13 a side cross section of the lenses along the line 13-13 out 12 is;
• 14 FIG. 4 is a diagram of a lens arrangement for a drift-tolerant 16 millimeter lens system, in which, according to another embodiment, an adjustable lens assembly is located between the optics and the image sensor;
• 14A a diagram of the image circles of a rectangular image sensor that can be used in the vision system according to an embodiment;
• 15 FIG. 2 is a diagram of a lens arrangement for a drift-tolerant 25 millimeter lens system, in which, according to another embodiment, an adjustable lens assembly is located between the optics and the image sensor;
• 16 FIG. 4 is a diagram of a lens arrangement for a drift-tolerant 35 millimeter lens system, in which, according to another embodiment, an adjustable lens assembly is located between the optics and the image sensor;
• 17th Figure 3 is a perspective view of a lens assembly, which is one version of the lens assembly 16 contains; and
• 18th a side cross section of the lenses along the line 18-18 out 17th is.

DETAILED DESCRIPTION

System overview

1 shows a vision system 100 in detail, this is a vision system camera assembly 110 including the associated lens unit / assembly 120 contains. The construction of the lens unit 120 is described in more detail below. In one embodiment, the lens unit 120 attached to the camera and can be removable using a specific or conventional mounting base, such as the well-known cine mount. The camera contains a body / housing in which a plurality of operating components, such as an image sensor or image converter 130 (shown in dashed lines). In this embodiment, the imager is 130 functional with a built-in visual processor 140 connected who operates a variety of hardware and / or software processes, generally as a visual process 142 be designated. The vision process 142 may include a variety of software applications designed to perform general or specific vision system tasks, such as tasks of finding and decoding ID codes (ID codes), edge detection, blob analysis, surface inspection, robot manipulation and / or other operations. See e.g. B. the exemplary ID 144 . The processes 142 may also include various imaging and manipulation applications, e.g. B. histogram formation, threshold value formation, etc., whereby image data are brought into a form which can be better used for vision system tasks. These tasks and processes are known to those skilled in the art and can be obtained from a commercial vision system provider such as Cognex Corporation, Natick, MA. The exemplary vision system processor 140 is included in the camera body as shown here. Visual system data in "raw" form, in pre-processed form (e.g. as found, not yet decoded ID image data) or in completely processed form (e.g. as decoded ID data) can be connected via a cable and / or wireless connection 144 to a suitable data processing system or a suitable processor, e.g. B. an independent single computer or to a server system. Alternative systems such as mobile computer systems, cloud-based facilities and the like can be provided as part of alternative implementations. The data processing system stores and manipulates the image-based data in accordance with the user request, for example as quality control or inventory control data. In alternative embodiments, some or all of the vision system processors / processes may be in a remote processor (e.g., the computing device / processor 150 ) can be instantiated and / or carried out in a manner known to the person skilled in the art via a suitable wired and / or wireless connection (e.g. the connection 144 ) with the camera 110 connected is.

It should be noted that the terms “process” and / or “processor” used here are to be interpreted broadly so that they encompass a large number of functions and components based on electronic hardware and / or software. In addition, a process or processor shown here can be combined with other processes and / or processors or divided into different subprocesses or subprocessors. Such subprocesses and / or subprocessors can be combined with one another in various ways according to the present embodiments. Likewise, it is expressly contemplated that each function, process, and / or processor listed here will use electronic hardware, software consisting of program instructions available on a non-volatile, computer-readable medium, or a combination of hardware and Software can be implemented. In a system arrangement, such processes / process functions can be described as occurring / present in a corresponding “module” or “element”. For example, in an "ID reading module" that performs those functions that are related to reading and / or decoding ID codes.

The lens assembly 120 is along the optical axis OA shown aligned (where the plane of the sensor 130 is usually arranged perpendicular to the axis). The lens assembly 120 and the sensor 130 form an object O from. The object O can, for example, have any two-dimensional (2D) or three-dimensional (3D) surface or shape that is partially or entirely in the field of view, FOV ) fits. In the example shown, the area / distance (do) of the object O to the camera 110 (e.g. to the focal plane of the sensor 130 ) can be changed, however (according to an exemplary embodiment) a predetermined operating range is defined within which the object O is to be depicted.

By way of example, this embodiment compensates for a potential optical drift that occurs over time in the case of an adjusting lens (for example a liquid lens) that forms part of the overall lens assembly 120 is by defining an operating range for the vision system in which the influence of the optical strength of the adjusting lens on the optical strength of the overall lens assembly (including all fixed lenses contained therein) is reduced. In this way, the drift represents only a small component of the total internal power of the lens assembly. This exemplary arrangement is useful where the adjustable focal length range can be reduced. This system is therefore useful in various embodiments - for example, those in which the distance (do) of the object surface from the focal plane is relatively constant or in which this distance (do) changes only by a small relative distance. For example, this system can be used in vision system applications that read from long distances, with the required optical range being only a small fraction (approximately 2 diopters) of the specified range of commercially available liquid lenses (20 diopters). As described above, the adjustable lens assembly of the embodiments contemplated herein may include a variety of lens types that are capable of changing optical power. In particular, in some embodiments the change in the optical power (and thus the focal length / focus distance, the focal length = 1 / optical power) takes place by controlling the lens shape and / or the refractive index of the lens. Such adjustable lens assemblies include liquid lenses and a variety of lens types, such as those with fluids of the same density (from Varioptic) or those with a membrane (from Optotune) etc. can be used. Likewise, adjustable lenses can be used that work using other mechanisms, such as electromechanical actuation.

Drift reducing lens assembly

The example of a further illustration of the basic ideas of an embodiment shows 2nd a ray tracing diagram of a basic optics arrangement for an exemplary vision system 200 with an exemplary object O1 , an image sensor 230 and a generalized adjustment lens (e.g. a liquid lens ( LL1 )). The object O1 is at a distance d1 from the adjustable lens LL1 positioned. This system has no additional lenses and those from the object O1 reflected rays 240 go through the adjustable lens LL1 and, as shown, directly on the image sensor 130 focused. Thus, every (for example drift-related) slight change in the focal point of the adjustment lens LL1 to a potentially significant blur condition that can affect the vision system's ability to provide a correct result.

To this sensitivity for drift and other focus deviations in z. B. to consider a liquid lens is now on 3rd Reference, which is a generalized optical arrangement for a vision system 300 according to one embodiment. A positive (non-adjustable) fixed lens PL is located at a predetermined distance d in front of the adjustable lens assembly (e.g. liquid lens assembly) LL2 along the optical path between the system and the depicted object O2 .

Wenn der Abstand zwischen der Verstelllinse LL2 und der Positivlinse PL relativ groß ist (z. B. d = k/A1 (wobei k = 0,5 ... 0,9 ist und das Produkt der Stärke der Positivlinse A1 und des Abstands d darstellt; d. h. k = d*A1)), so kann die optische Gesamtstärke A des oben definierten Linsensystems mit den Stärken A1 und A2 und dem relativen Abstand d wie folgt wiedergegeben werden: $$\text{A}=\text{A}1+\left(1-\text{k}\right)*\text{A}2$$

und ist der Drift, der als Differential der optischen Stärke (dA) der Linse pro Einheitszeit (dT) (dA/dT) des Systems dargestellt ist, wie folgt: $$\text{dA}/\text{dT}=\text{dA}1/\text{dT}+\left(1-\text{k}\right)*\text{dA}2/\text{dT}$$

was bedeutet, dass der Drift des Gesamtsystems dA/DT der Summe des Drifts der Positivlinse dA1/dT und (1 - k) mal dem Drift der Verstelllinse dA2/dT entspricht.Thus the optical strength is A of this system 300 (where A1 is the optical power of the positive lens assembly PL , A2 the optical strength of the lens assembly LL2 and d the distance between the positive lens PL and the adjustable lens LL2 corresponds) as follows: $$\text{A}=\text{A}1+\text{A}\mathrm{2nd}-\text{d}*\text{A}1*\text{A}\mathrm{2nd}$$

If the distance between the adjustable lens LL2 and the positive lens PL is relatively large (e.g. d = k / A1 (where k = 0.5 ... 0.9 and is the product of the power of the positive lens A1 and the distance d; ie k = d * A1)), the total optical power A of the lens system defined above with the powers A1 and A2 and the relative distance d can be reproduced as follows: $$\text{A}=\text{A}1+\left(1-\text{k}\right)*\text{A}\mathrm{2nd}$$

and the drift, represented as the differential of the optical power (dA) of the lens per unit time (dT) (dA / dT) of the system, is as follows: $$\text{there}/\text{dT}=\text{there}1/\text{dT}+\left(1-\text{k}\right)*\text{there}\mathrm{2nd}/\text{dT}$$

which means that the drift of the overall system dA / DT corresponds to the sum of the drift of the positive lens dA1 / dT and (1 - k) times the drift of the adjustable lens dA2 / dT.

In one embodiment, the positive fixed lens PL be chosen as a glass lens with inherently low drift (ie dA1 / dT ≈ 0), so that in comparison to the original design 2nd using the positive lens PL and the larger power of the positive lens (ie larger k) effectively reduce the overall drift dA / dT of the system 3rd by a factor of 1 - k (= 0.1 times ... 0.5 times), the greater the drift reduction in the adjustable lens.

It is now going on 4th Reference is made in detail to a cross section of an integrated lens unit / assembly 120 for use in the exemplary vision system camera 110 out 1 shows. This lens assembly 120 can various electrical connections and / or lines (here schematically dashed as a cable 410 and connectors 412 shown) which are different from the adjustable lens assembly (e.g. liquid lens assembly) 420 to a location on the camera body 110 extend that with appropriate, the vision processor 140 associated control processors / components. It should be noted that the exemplary liquid lens assembly 420 , which can be a type with a membrane, a type with liquids of the same density or an equivalent type, within a tube 430 is included and the line 410 is constructed so that it extends from one place on the tube 430 extends from. This connection allows control signals to be supplied to the liquid lens assembly (e.g., by current and / or voltage modulation) to change and adjust the focus of the liquid lens assembly 420 in response to commands from the processor. The correct focus can be determined and / or set using a variety of techniques known to those skilled in the art - such as using the sharpness of imaged edges after various focus settings have been tried and / or using an external area finder . Although a separate cable connection with an associated connector is used on the camera housing in the embodiment shown, the connection arrangement can also be in the interior of the tube 430 be provided - e.g. B. in the form of mutually aligned contact surfaces and / or contact rings (on the lens and the camera housing), which are connected to each other when the lens assembly 120 is attached to the camera body.

The tube 430 the lens assembly is in this embodiment with the form factor of a conventional C-mount lens with a corresponding thread base 440 dimensioned and arranged. The illustrated external thread of the tube base (the flange 440 ) is designed so that it fits a corresponding internal thread (not shown) on the camera housing. It is a conventional thread size (e.g. 1 inch X 32). It should be noted that the camera housing can contain a variety of accessories and functional components, such as a ring illuminator that surrounds the lens and / or connections for an external lighting assembly. Such accessories and / or components can be attached to the camera to perform various vision system tasks. The tube 430 can be constructed from a variety of materials, e.g. B. made of cast or machined aluminum alloy. The threaded base allows the tube and the associated overall lens assembly contained therein to be detachably attached to the camera housing and, depending on the needs of the manufacturer or user, to be replaced by other types of lenses. Even if the form factor of a C-mount base is used in this embodiment, any suitable lens base shape can be used in alternative embodiments, which enables the accommodation of a liquid lens or another usable adjustment lens. For example, an F-mount lens base can also be used.

The dimensions of the lens barrel 430 are in 4th shown using an example without any restrictive character. As shown, the tube outer diameter ODL may be approximately 28 to 29 millimeters in one embodiment. This takes into account the general size restrictions / parameters of a C-mount lens. The length of the tube is also OLL 430 from the front end 432 to the thread base 440 approximately 32 to 34 millimeters for illustrative purposes. The distance DS between the lens base 440 and the focal plane of the image sensor 130 is approximately 17.5 millimeters. It should be noted that these dimensions are exemplary of a wide range of possible relationships known to those skilled in the art.

It will now refer to 4A , the positioning of the internal optical components of the lens is described in detail. A positive lens assembly 450 which is related to the diameter of the adjustment lens ( 420 ) has a relatively large diameter, is adjacent to the front end 432 of the tube 430 located. This positive lens assembly 450 (also called "positive lens") is located in a recess formed at the front end of the tube 454 . The positive lens 450 is on hers Front by one 456 Threaded ring attached. It should be noted that the arrangement is designed to be extremely variable in alternative embodiments and that a plurality of fastening and / or attachment mechanisms can be used in alternative embodiments. With the positive lens 450 It is an achromatic double lens that defines an effective focal length (f) of 40 mm and a rear focal length of 33.26 millimeters. The open aperture is 24 millimeters. The diameter of the entire lens assembly is 25 millimeters. For the sake of illustration, it consists of a front convex lens 458 and a rear concave lens 459 . The convex lens 458 defines a front radius RL1 of 27.97 millimeters and a rear radius RL2 of 18.85 millimeters (with positive and negative radii each indicating directions with respect to the orientation relative to the object depicted, positive radii being oriented toward the object and negative radii toward the image sensor). The concave lens 459 defines a front radius (also RL2 ) of 18.85 millimeters (and complements the counter surface of the convex lens 458 ) and a rear radius RL3 of 152.94 millimeters. The convex lens 458 has a center thickness TC1 (along the optical axis OA ) of 9.5 millimeters and the concave lens has a center thickness TC2 of 2.5 millimeters. These dimensions can be very different in alternative embodiments. The embodiment described above and the associated dimensions of a positive lens assembly 450 (e.g. with double lens) is commercially available from Edmund Optics Inc., Barrington, NJ, under item number 32321. In this embodiment, the distance is ODLF approximately 49 millimeters between the front of the lens and the sensor plane according to one embodiment. It is understood that the dimensions of the positive lens and / or the component arrangement can differ greatly from one another in alternative embodiments.

The adjustable lens assembly (e.g. liquid lens assembly) 420 (which can be obtained from a variety of manufacturers) is adjacent to the rear end of the lens barrel 430 positioned. In this embodiment, as an example, without limitation, the lens assembly 420 an Arctic liquid lens 416 , available from Varioptic, France. The exemplary lens assembly has a focus range of approximately 20 diopters (ie, from 5 centimeters to infinity), a diameter of 7.75 millimeters and a thickness (along the optical axis) of 1.6 millimeters. The exemplary liquid lens assembly shown 420 consists of the on a controller circuit board 472 mounted lens unit 470 with a central aperture 474 that is aligned along the optical axis and through the focused light to the sensor 130 reached.

The lens assembly 130 can by means of an integral or as a unitary spacer, a shoulder arrangement and / or a support structure 460 inside the tube 430 be stored. The supporting structure 460 ensures that the adjustable lens assembly 420 in an appropriate alignment with respect to the optical axis OA remains. The distance DLR from the back of the positive lens to the front of the adjustable lens unit 470 is 18.0 millimeters in this embodiment. It should be noted that the image sensor 130 in one embodiment, a conventional 0.5 inch (6.9 millimeter (horizontal) by 5.5 millimeter (vertical) - SW in CMOS sensor 5 ) can define.

It is now on the 5 to 7 Reference is made to show the vision system and lens assembly operating with a plurality of focal lengths within the operating range of the system. The object O is therefore in the ray tracing diagram from the 5 , 6 and 7 each in three different, exemplary intervals DO1 , DO2 and DO3 . For example, the distance is DO1 about 219 millimeters, the distance DO2 about 430 millimeters and the distance DO3 about 635 millimeters. Within this range, the optical power of the lens assembly is +10.73 diopters for F = 37.4 millimeters (5); to +0.32 diopters for F = 39.8 millimeters (6); and changed to -3.81 diopters for F = 42.3 millimeters. This focal length range from 219 to 635 millimeters is associated with a change of 6.9 diopters. In comparison, a system configuration with the illustrated lens assembly in a conventional arrangement in which the lens is closely spaced from the front lens usually requires a change of 3.3 diopters. Thus, the exemplary system effectively reduces the potential drift relative to a conventional arrangement by more than a factor of 2.

More generally, the adjustable lens assembly (e.g., liquid lens assembly) is adjacent to but is distant from a focal point of the positive lens assembly, which may be the front or, more typically, the rear / rear focal point of the positive lens assembly. It is understood that the positioning adjacent to the focal point enables the adjustment lens to contribute to the overall strength of the lens system. The distance between the adjustment lens assembly and the focal point can be approximately between 0.1 times and 0.5 times a focal length F of the positive lens assembly. For the sake of illustration, reference is made to the diagram 8th taken with a positive lens assembly PL along the optical axis OA is positioned, with an adjustable lens VL adjacent to the focal point FP the positive lens. Between the positive lens PL and the focus FP the focal length F is shown. The distance (1 - k) * F is the distance between the adjustment lens VL and the focus lens characterizes and the focal point FP is characterized with k = 0.9 to 0.5 (ie 0.9 * F to 0.5 * F). The distance between the positive lens PL and the adjustable lens VL is thus k * F (ie 0.1 * F to 0.5 * F). In this way, the positive lens assembly PL and the adjustable lens assembly VL Part of an overall lens assembly LA which focuses light on the image sensor, with which an overall optical power of the overall lens assembly is “predominantly” defined by the optical power of the positive lens assembly - in other words, the magnification / optical power is largely provided by the positive lens assembly, thereby minimizing the drifting effect of the adjustment lens assembly becomes.

It is now on the 9 and 10th Reference is shown in which two embodiments of drift reducing lens assemblies are shown according to corresponding embodiments. The tables below also provide corresponding, exemplary parameters for each lens element. 9 is a lens arrangement 900 in connection with an image sensor 910 of (e.g.) conventional design. In this embodiment, the adjustment lens comprises a liquid lens assembly 920 . The rays shown 930 are from an object (not shown) that is at a distance of (e.g.) 200 millimeters from the first lens 940 can be placed in the lens assembly 900 reflected into it. As an example, without limitation, this lens includes 940 a front concave surface 942 and a rear convex surface 944 . This lens can comprise a polymer, such as polycarbonate (or another optically suitable material). A central lens assembly includes a composite front lens 950 with a convex lens 952 that have a front surface 954 and a back surface 956 having. This fits with a concave lens 958 with a convex surface of a similar radius and a rear convex surface 960 together. It should be noted that the lens element (s) ( 950 ) can also be made of polycarbonate (or another optical material). A disc-shaped optical element 970 (e.g. an IR filter) with infinite radii on each side (e.g. on parallel planes) is behind the compound lens assembly 950 . The Rays 930 run off the disk 970 on the adjustable lens assembly (liquid lens assembly) 920 out together. This exemplary assembly can essentially be found on the Arctic 416 from Varioptic of France or on another suitable lens (e.g. a liquid lens). It includes a front cover 980 that with the lens control circuit 990 connected lens element 982 who have favourited aperture stop 984 (with an associated radius of 341.763 millimeters) and a rear cover plate 986 . The lens control circuit can be operatively connected to the vision system described above. This element is adapted to focus on the image sensor 910 to maintain and counteract a drift based on a variety of conditions described above. The spacing between the liquid lens assembly 920 and the imager can be approximately 13-14 millimeters and the spacing between the disk 970 and the liquid lens assembly 920 can be about 3-4 millimeters. It should be noted that the shape of the exemplary lenses and the spacing between them can be modified in accordance with the relevant specialist knowledge. Likewise, the adjustable lens assembly can comprise many different types of lenses, which are operated according to different physical principles. For example, a liquid lens with membrane available from the Swiss company Optotune as well as mechanical lens types can be used as a replacement.

In 10th Now referenced is another embodiment of a lens assembly 1000 mapped that can provide low drift across a given operating range. This arrangement includes an image sensor 1010 of conventional design and an adjustable lens assembly (liquid lens assembly) 1020 . The Rays 1030 become from a (not shown) object in a range of (e.g.) 80-100 millimeters to a front convex lens 1040 reflected. As an example, without limitation, the front lens includes 1040 a front convex surface 1042 and a rear concave surface 1044 . The next lens 1046 defines a front convex surface 1048 and a rear concave surface 1050 . The next lens 1060 is on both surfaces 1062 and 1064 concave, with a front surface 1062 and a back surface 1064 . The Rays 1030 emerge from this lens 1060 and are introduced into the adjustable lens assembly (e.g., the liquid lens assembly) 1020, which in this embodiment is located in the center of the optics assembly, with additional lenses 1080 and 1088 between this and the image sensor 1010 are positioned. In this example, the liquid lens assembly is similar 1020 the model and construction according to the assembly described above 920 (with an aperture stop having a radius of 10.101 millimeters) and it is controlled by a lens controller 1090 controlled, which can be operated similarly to the controller also described above 990 . Alternative embodiments of the adjustable lens assembly can optionally be used, as described above with reference to the arrangement 900 has been described. From the liquid lens assembly (e.g., the liquid lens assembly) 1020, the rays 1030 into a convex lens 1080 initiated, which is spaced approximately 1.2 millimeters from the liquid lens assembly. The convex lens 1080 includes a front convex surface 1082 and a rear convex surface 1084 . A disc-shaped filter (e.g. an IR filter) 1088 can be located behind the convex lens 1080 are located. In the current embodiment, this is arranged at a distance of approximately 10-12 millimeters in front of the image sensor. As an example, without limitation, the lenses are made from an optical glass in this embodiment, with one or more of the lenses (or other optical elements) being made from another acceptable material, such as polycarbonate or another suitable equivalent material can be.

The lens arrangements described above 900 and 1000 can be adapted to be enclosed in a lens package with (e.g.) a conventional camera base mount, such as a "C-mount" mount described above. Suitable electrical connectors can be provided between the lens body and the camera base to allow control of the adjustment lens assembly. All or part of the electronics of the control circuit can be accommodated in the lens body, or suitably also in the camera housing.

As an example, without limitation, the lenses of the various embodiments herein can define the parameters specified in each of the tables set forth below. The parameters of the lens assembly 900 ( 9 ) are provided below in the first table, where (if available) the associated front and rear surfaces of each structure or element within the overall assembly (from left to right) are given in the order of 0 - 13: surface structure Reference # Radius (mm) Thickness or distance to the next surface (mm) material Half diameter (mm) 0 Object (not shown) 200.414 1 Lens 940 942 -5.758 3,543 Polycarbonate 3.28 2nd 944 -6.977 4,121 4.00 3rd Lens 950 954 11,027 3,012 480R + PC 4.00 4th 956 -5,976 0.792 4.00 5 960 -48.925 0.100 4.00 6 Filter 970 infinite (flat) 1,300 B270 4.00 7 infinite (flat) 3,000 4.00 8th Liquid lens 920 infinite (flat) 0.550 multiple 2.00 9 infinite (flat) 2.00 10th variable 1.15 11 infinite (flat) 0.300 2.00 12 infinite (flat) 13,884 2.00 13 Photo 910

The table below applies to the lens assembly 1000 ( 10th ), whereby (if available) the associated front and rear surfaces of each structure or element within the overall assembly (from left to right) are each given in the order of 0 - 14: surface structure Reference # Radius (mm) Thickness or distance to the next surface (mm) material Half diameter (mm) 0 Object (not shown) 82,081 1 Lens 1040 1042 13,078 1,461 N-LASF9 4.00 2nd 1044 49.620 0.256 4.00 3rd Lens 1046 1048 19.922 1,770 N-SF6 4.00 4th 1050 18,444 1,066 4.00 5 Lens 1060 1062 -25,000 1,495 N-SF6 4.00 6 1064 25,000 2,000 4.00 7 Liquid lens 1020 infinite (flat) 0.550 multiple 2.00 8th infinite (flat) 2.00 9 variable 1.15 10th infinite (flat) 0.300 2.00 11 infinite (flat) 1,200 2.00 12 Lens 1080 1082 23.854 1,400 N-LASF9 3.00 13 1084 -18,000 1,433 3.00 14 Filter 1088 infinite (flat) 1,300 B270 3.00 15 infinite (flat) 11,100 3.00 16 image 1010

It is also contemplated that the drift compensating lens assembly of the present embodiments may be used in combination with other drift reducing methods, such as temperature stabilization of the lens system or the optical feedback systems. Such arrangements in the commonly assigned US patent application with the serial number 8,576,390, entitled "SYSTEM AND METHOD FOR DETERMINING AND CONTROLLING FOCAL DISTANCE IN A VISION SYSTEM CAMERA" (system and method for determining and controlling the focal length of a system) are an example without restrictive character Vision system camera), shown and described by Nunnink and these are incorporated here by reference as useful background information. Furthermore, reference is made to the US patent application with the serial number 14 / 139,867, with the title “CONSTANT MAGNIFICATION LENS FOR VISION SYSTEM CAMERA” (constant magnifying lens for a vision system camera), by Nunnink; and U.S. Patent Application Serial No. 13 / 800,055, entitled LENS ASSEMBLY WITH INTEGRATED FEEDBACK LOOP FOR FOCUS ADJUSTMENT, by Nunnink et al. For purposes of illustration, the present application provides a detachably attachable lens assembly for a vision system camera that includes an integrated auto-focus liquid lens unit in which the lens unit compensates for focus changes using a feedback control circuit integrated into the lens assembly body. The feedback control circuit receives motion information related to the actuator, such as a lens coil (which tensions the electrically controllable membrane to different degrees) from a position sensor (e.g., a Hall sensor) and uses this information internally to detect motion changes from the set position correct the lens at a target lens focal length setting. The position sensor can be a single unit or a combination of different ones with respect to the actuator or the coil arranged, discrete sensors act with or with which movements are measured at different points in the area around the lens unit. For purposes of illustration, the feedback circuit may be connected to one or more temperature sensors that adjust the lens adjustment position for a particular temperature value. The feedback circuit may also communicate with an accelerometer that senses the direction of gravity and thereby corrects a potential sag (or other orientation-related deformation) of the lens membrane based on the spatial orientation of the lens.

Drift reducing lens assembly

In the 11 - 18th Embodiments of a drift-reducing lens are described in different ways that enable object features (e.g., ID codes) to be read over a wider area for use in various camera assemblies and associated applications, including portable and stationary devices. With the present lens arrangements, focal length ranges of up to approximately 8 meters can be imaged. In general, the exemplary arrangements provide a focus-adjustable lens (e.g., a liquid lens) that is positioned behind the rest of the fixed lens optics package, so that the focusing lens is generally on the back of the lens assembly between the fixed optics package and the camera image sensor. In 11 which is now referred to is a lens assembly 1100 shown. This arrangement is applicable to a 12 millimeter lens (f = 12). As shown, a relative scale scale 1110 the total lens arrangement (in millimeters). The lens fixed optics area (in the dashed box 1120 shown) consists of a front plate element 1130 followed by a biconvex lens 1132 . Behind the biconvex lens 1132 is a set consisting of three lenses with smaller diameters 1134 (positive), 1136 (biconcave) and 1138 (positive, with opposite orientation). In this embodiment, the fixed optical package 1120 provided in a separate lens housing, while a focus lens assembly 1140 mounted in the scope of the vision system housing (e.g. in a portable ID reader, as described in the commonly assigned US patent application with the serial number 14 / 550,709, entitled IMAGE MODULE INCLUDING MOUNTING AND DECODER FOR MOBILE DEVICES (image module, including Bracket and decoder, for mobile devices), filed on November 21, 2014). The adjustable lens assembly can be used as an example without restrictive character 1140 the liquid lens mechanism described above, available from the Swiss company Optotune. Alternatively, the adjustable lens assembly may include any usable, manually or electronically adjustable lens assembly, including those described above, available from the French company Varioptic. The adjustable lens assembly 1140 can be connected (via a cable, printed circuit boards, etc.) to the vision system processor or to another controller that allows focal length adjustment of the lens. This controller can be integrated with the feedback system described above. The adjustable lens assembly 1140 is, if appropriate, optionally equipped with one or more filters and / or dust covers. An aperture stop 1142 is also provided in this embodiment. The adjustable lens assembly 1140 focuses light (the rays 1150 ) on the image sensor 1152 with a view to transmission to the vision system processor. The total length 1160 the arrangement 1100 between the front surface of the plate 1130 and the image sensor 1152 is approximately 15.2 millimeters. The distance 1162 between the back surface of the back lens 1138 and the image plane (the image sensor 1152 ) is approximately 10.26 millimeters. As an example, define the approximate parameters of the arrangement 1100 an aperture F / # with 7; an image radius of 3 millimeters (ie 1/3 inch for a 1.2 megapixel sensor up to a 5.0 megapixel sensor); an RMS spot radius of 1.7 µm at 3 mm image height; and a measured distortion of less than 3% - 4%.

The table below applies to the lens assembly 1100 ( 11 ), whereby (if available) the corresponding front and rear surfaces of each structure or element within the overall assembly (from left to right) are each given in the order of 0 - 16: surface structure Radius (mm) Thickness or distance to the next surface (mm) material Half diameter (mm) 0 Object (not shown) 500 1 Filter 1130 infinite (flat) 0.650 B-270 2.50 2nd infinite (flat) 0.200 2.50 3rd Lens 1132 11.175 1,300 N-SK16 2.50 4th -11.175 0.200 2.50 5 Lens 1134 3,765 0.850 N-SK16 1.50 6 5,228 0.336 1.00 7 Lens 1136 -5,227 0.800 N-SF2 1.50 8th 5,227 0.150 1.20 9 Aperture diaphragm 1142 0.150 multiple 0.63 10th Lens 1138 -8.538 0.800 N-BAF10 1.20 11 -3,331 1,100 1.50 12 Liquid lens 1100 variable multiple 1.60 13 infinite (flat) 1.60 14 Sensor window 1152 infinite (flat) 0.400 D263T 15 infinite (flat) 0.125 16 Fig. 1160

It should be noted that the lens parameter tables presented above and below are only to be regarded as examples of a wide range of possible implementations. It will be understood by those skilled in the art that any or all of the present lenses and / or optical components can be modified by using different parts, sizes, focal lengths, thicknesses, etc., as appropriate for the mechanical and optical requirements of the imaging application .

The 12 and 13 show a lens assembly 1200 which of the fixed optics pack 1120 corresponds. The lens elements are in a tube housing 1210 included, which is made of aluminum or other usable material. The lens elements are numbered similarly to their counterparts in the assembly 1120 out 11 . The base 1230 of the lenses 1200 can be in any usable format - for example, a C-mount thread base (ie 1 inch X 32 threads per inch) can be specified for the total length of the tube. Alternatively, an M8x0.5 thread can be specified for the total length of the tube, or in both cases for an appropriate section thereof. As in the cross section 13 shown, can be an aperture stop 1310 between the biconcave lens 1136 and the rearmost positive lens 1138 are located. The one in the tube 1210 contained lenses 1130-1138 through a front retaining ring 1240 with an outer diameter 1330 held by 10 millimeters, which on the front end of the tube 1210 is screwed on. A threaded spacer ring 1250 is also screwed onto the tube and is located at a point along it to adjust the focal length of the lens assembly with respect to the image plane. In one embodiment, the ring 1250 after correct positioning on the lens barrel 1210 are permanently / semi-permanently attached to the tube by means of a thread locking compound, an adhesive or another fastening mechanism (e.g. a set screw, a pin, etc.). When the lens is screwed into the lens holder of the device, the ring comes 1250 against the bracket and thus provides the desired spacing. In one embodiment, the total lens length is 1340 approximately 6.9 millimeters and the set distance is 1350 between the back surface of the retaining ring 1250 and the image plane 1360 about 12.15 millimeters.

The 14 - 18th depict versions of a drift-reducing lens assembly in different ways, which can include the adjustment lens in its overall structure and which (e.g.) can be used in stationary vision systems - for example, in ID readers used in logistics and object tracking applications.

In 14 To which reference is now made, a 16 millimeter lens array 1400 is shown. This arrangement can be with a housing 1410 be configured which the adjustable lens assembly (e.g. the liquid lens assembly) 1430 included in the overall package. The lens assembly is via a cable 1432 or otherwise connected to a connector / contact on the camera or other vision system housing which communicates with the processor such that the focal length of the lens assembly 1430 can be controlled. It should be noted that differently designed circuitry can be built into or attached to the lens housing to perform some or all of the functions of the lens control.

The lens arrangement 1400 includes a front negative lens 1440 , followed by a negative lens with a smaller diameter 1442 , another biconvex lens 1444 and a double lens with a smaller diameter 1445 consisting of a biconvex lens 1446 and a plano-concave lens 1448 . A second double lens with a smaller diameter 1450 consisting of a positive lens 1452 and a biconvex lens 1454 , is behind the first double lens 1445 provided and a positive lens 1456 is between the double lens 1450 and the adjustable lens assembly (liquid lens assembly) 1430 intended. In addition, an aperture diaphragm 1458 on the back surface of the last positive lens 1456 be provided. The relative scale, given in millimeters 1470 is shown and the rear focal length 1480 between the back of the adjustable lens 1430 and the image plane on the surface of the image sensor 1490 is set to approximately 8.5 millimeters using appropriate adjustment rings, bases, brackets, etc. that should be understood by those skilled in the art. As in 14A In short, an image circle of approximately 8 millimeters in diameter is created. This is within the maximum image circle 1496 (of approximately 8.83 millimeters) of the exemplary sensor shown 1490 , which is a CMOS image sensor of the model IMX265 (from the Japanese company Sony). That is, the image circle 1496 circumscribes the corners of the rectangular perimeter 1495 that the usable arrangement of image pixels for the sensor 1490 represents. Other image sensors, such as the one through the rectangle 1494 has a defined pixel arrangement, are characterized by a different (in this example smaller - e.g. 7.66 millimeter) image circle dimension ( 1493 ) out. Such a small-sized sensor is available from the British company Teledyne e2v, Ltd. available.

Other exemplary optical parameters of the lens assembly 1400 may include a focal length of approximately 16.2 to 16.6 millimeters, an aperture size of F8, a total length of approximately 27.9 millimeters, a focus range of 1.0 to 4.0 meters and an operating range for the focusing lens of approximately 0, 0 to 2.5 diopters. Within this range there is theoretically 2.5 times less drift than with a conventional design. The RMS spot radius is less than 2.2 microns in the extreme field of view position (FOV position).

The table below applies to the lens assembly 1400 ( 14 ), where (if available) the corresponding front and rear surfaces of each structure or element within the overall assembly (from left to right) are each given in the order of 0 - 20: surface structure Radius (mm) Thickness or distance to the next surface (mm) material Half diameter (mm) 0 Object (not shown) 1828,571 1 Lens 1440 25,720 1,143 N-BK7 3,886 2nd 6,657 1,000 3,000 3rd Lens 1442 14.130 2,000 N-SK16 3,000 4th 5,789 1,000 2,500 5 Lens 1444 20,400 0.914 N-SK16 2,500 6 -32.069 0.229 2,266 7 Double lens 1445 10,082 1,234 N-SK16 + N-SF2 2,237 8th -32.093 1,097 2,129 9 32.093 0.200 1,988 10th Double lens 1450 5,850 1,097 N-SF2 + N-BK7 2,000 11 5,000 1,500 2,000 12 -12.411 0.229 2,000 13 Lens 1456 6,259 1,000 N-SF2 2,000 14 3,130 0.229 0.920 15 Aperture diaphragm 1458 1,000 multiple 0.898 16 Liquid lens 1430 variable multiple 1,600 17th infinite (flat) 9.740 1,600 18th Sensor window 1490 infinite (flat) 0.400 D263T 19th infinite (flat) 0.125 20th Fig. 1494

In 15 To which reference is now made, a 25 millimeter lens array 1500 is shown. This arrangement can be with a housing 1510 be configured which the adjustable lens assembly (e.g. the liquid lens assembly) 1530 included in the overall package. As described above, the lens assembly is via a cable 1532 or otherwise connected to a connector / contacts. The lens arrangement 1500 includes a front lens 1540 with a slightly concave front surface, followed by a plano-convex lens with a smaller diameter 1542 and a double lens 1544 consisting of a biconvex lens 1546 and a biconcave lens 1548 . A second double lens with a smaller diameter 1550 consisting of a first positive lens 1552 and a second lens 1554 , is behind the first double lens 1544 provided and a negative lens 1556 is between the double lens 1550 and the adjustable lens assembly (liquid lens assembly) 1530 intended. In addition, an aperture diaphragm 1558 on the back surface of the last positive lens 1556 be provided. The relative scale, given in millimeters 1570 is shown and the rear focal length 1580 between the back of the adjustable lens 1530 and the image plane on the surface of the image sensor 1590 (e.g., approximately an 8 millimeter image circle) is set to approximately 8.5 millimeters using appropriate adjustment rings, bases, brackets, etc. that should be understood by those skilled in the art. Other parameters of the lens assembly include a focal length of approximately 24.2 to 25.2 millimeters, an aperture size of F8, an overall length of approximately 27.6 millimeters, a focus range of 1.0 to 4.0 meters and an operating range for the lens of about 0.0 to 4.0 diopters. Within this range, there is theoretically four times less drift than with a conventional design. The RMS spot radius is less than 1.9 microns in the extreme field of view position (FOV position).

The table below applies to the lens assembly 1500 ( 11 ), where (if available) the corresponding front and rear surfaces of each structure or element within the overall assembly (from left to right) are each given in the order of 0 - 16: surface structure Radius (mm) Thickness or distance to the next surface (mm) material Half diameter (mm) 0 Object (not shown) variable 1 Lens 1540 141.523 1,786 N-SK16 6,071 2nd infinite (flat) 0.300 6,071 3rd Lens 1542 24,589 1,429 N-SK16 4,286 4th 179.888 0.357 4,286 7 Double lens 1544 11.789 1,929 N-SK16 + N-SF2 4,286 8th -13.653 1,714 4,286 9 13,653 1,434 3,571 10th Double lens 1550 6,888 1,714 N-SF2 + N-BK7 2,500 11 8,747 1,071 2,500 12 14.691 0.357 1,786 13 Lens 1556 8,245 0.714 N-BK7 2,500 14 4,122 0.357 1,786 15 Aperture diaphragm 1558 1,429 multiple 0.850 16 Liquid lens 1530 variable multiple 1,600 17th infinite (flat) 8,500 1,600 14 Sensor window 1590 infinite (flat) 0.400 D263T 15 infinite (flat) 0.125 16 Fig. 1594

In 16 To which reference is now made, a 35 millimeter lens array 1600 is shown. The lens assembly in this embodiment is for use in large-scale camera assemblies such as those used in high volume logistics operations (e.g. fulfillment services, bulk shipping operations, etc.) that handle objects of different sizes. This lens arrangement 1600 can with a housing 1610 (in 16 Shown as a dashed box and described in more detail below), which the adjustable lens assembly (e.g. the liquid lens assembly) 1630 included in the overall package. As described above, the lens assembly is via a cable 1632 or otherwise connected to a connector / contacts.

The lens arrangement 1600 includes a front plano-convex lens with a large diameter 1640 , followed by a biconvex lens with a smaller diameter 1642 , stacked with a double lens 1644 consisting of a positive lens 1646 and a biconcave lens 1648 . A second double lens with a smaller diameter 1650 consisting of a first positive lens 1652 and a second plano-convex lens 1654 , is behind the first double lens 1644 provided and a negative lens 1656 is between the double lens 1650 and the adjustable lens assembly (liquid lens assembly) 1630 intended. In addition, an aperture diaphragm 1658 on the back surface of the last negative lens 1656 be provided. The relative scale, given in millimeters 1670 is shown and the rear focal length 1680 between the back of the adjustable lens 1630 and the image plane on the surface of the image sensor 1690 (e.g., an 8 millimeter image circle) is set to approximately 8.5 millimeters. Other parameters of the lens assembly include a focal length of approximately 32.4 to 34.8 millimeters, an aperture size of F8, an overall length of approximately 49.6 millimeters, a focus range of 1.0 to 4.0 meters and an operating range for the adjustable lens of approximately 0.0 to 6.5 diopters. Within this range, there is theoretically 6.5 times less drift than with a conventional design. The RMS spot radius is less than 3.4 microns in the extreme field of view (FOV) position.

The table below applies to the lens assembly 1600 ( 16 ), where (if available) the corresponding front and rear surfaces of each structure or element within the overall assembly (from left to right) are each given in the order of 0 - 20: surface structure Radius (mm) Thickness or distance to the next surface (mm) material Half diameter (mm) 0 Object (not shown) variable 1 Lens 1640 55,586 2,500 N-SK16 8,500 2nd infinite (flat) 10,000 8,500 3rd Lens 1642 20,856 3,000 N-SK16 6,000 4th -24,197 0.500 6,000 7 Double lens 1644 -20.861 2,700 N-SK16 + N-SF2 6,000 8th 17.704 2,400 6,000 9 17.704 7,479 5,000 10th Double lens 1650 8,787 2,400 N-SF2 + N-BK7 3,500 11 9,034 1,500 3,500 12 -2195.069 0.500 2,500 13 Lens 1656 11.052 1,000 N-BK7 3,500 14 5,526 0.500 2,500 15 Aperture diaphragm 1658 2,000 0.892 16 Liquid lens 1630 variable multiple 1,600 17th infinite (flat) 8,500 1,600 18th Sensor window 1690 infinite (flat) 0.400 D263T 19th infinite (flat) 0.125 20th Image 1694

The table below applies to the lens assembly 1800 ( 18th ), where (if available) the corresponding front and rear surfaces of each structure or element within the overall assembly (from left to right) are each given in the order of 0 - 22: surface structure Radius (mm) Thickness or distance to the next surface (mm) material Half diameter (mm) 0 Object (not shown) variable 1 Filter 1840 infinite (flat) 2,000 multiple 10.750 2nd infinite (flat) 3,500 10.750 3rd Lens 1842 infinite (flat) 2,000 N-SK16 9,500 4th -46.710 1,000 9,500 5 Double lens 1844 19.310 2,700 N-SK16 + N-SF2 7,500 6 infinite (flat) 2,400 7,500 7 62,220 1,500 7,000 8th Lens 1850 -30,000 2,000 N-SF2 7,500 9 30,000 1,000 7,000 10th Lens 1852 24,550 3,400 N-SK16 7,500 11 300,000 1,000 7,000 12 Lens 1854 -300,000 3,400 N-SF2 7,000 13 -24.550 1,000 7,500 14 Double lens 1856 18,000 2,400 N-SF2 + N-SK16 4,000 15 9,000 1,500 4,000 16 12,700 1,000 3,500 17th Lens 1858 30,000 1,500 N-SK16 4,000 18th 17.140 0.500 3,000 19th Aperture aperture 1859 0.987 20th Liquid lens 1860 variable multiple 1,600 21st infinite (flat) 9.103 1,600 22 Picture (not shown)

In the 17th and 18th , to which reference is now made, is another embodiment and / or implementation of the drift reduced 35 millimeter lens 1700 shown in more detail. This lens assembly 1700 includes an outer housing 1710 , which comprises a series of lenses that are compatible with the above in 16 described arrangement 1600 are functionally similar or identical. The housing can be made of any usable material (e.g. an aluminum alloy) and in various shapes. As shown, the housing includes 1710 a front end 1720 , a main tube 1730 and a rear end 1740 . With further reference to 18th becomes the front of the lens 1720 screwed into an internal thread that in an expanded flange 1820 of the main tube 1730 is trained. It should be noted that in this or in other embodiments, an optional filter (e.g. a red bandpass filter) 1840 can be attached to the front of the lens. The total diameter DF of the front end 1720 the lens is approximately 27.5 millimeters. Generally, the filter can be 1840 a commercially available thread filter with appropriate optical specifications (e.g. wavelength bandpass for visible colors, IR, UV, etc.). In the main tube 1730 are a plano-convex lens 1842 in front of a double lens 1844 , consisting of a plano-convex lens 1846 and a plano-concave lens 1848 which together create a positive lens geometry. A biconcave lens 1850 is behind the double lens 1844 stacked. A pair of oppositely aligned plano-convex lenses with a smaller diameter 1852 and 1854 is behind the biconcave lens 1850 intended. A double lens with a smaller diameter 1856 defines a negative lens behind the lenses 1852 and 1854 . This double lens 1856 is located behind a rearmost positive lens 1858 . The adjustable lens (ie the liquid lens) 1860 is behind the lenses 1858 . It is formed by an annular and threaded retaining ring 1862 that is in a rear collar 1864 with (e.g.) an M13 x 0.5 internal thread, in the rear end with smaller dimensions 1740 captured. The inside diameter IDC the collar is approximately 13 millimeters (thread area) and the outer diameter ODC is approximately 14 millimeters and its axial length LC can be approximately 3.1 millimeters. The retaining ring 1862 can be a slit 1866 comprise for tightening the ring by a sheet-shaped tool of appropriate size and shape. It should be noted that the lens assembly 1700 also in the optical path at a suitable location - for example, adjacent to the liquid lens assembly 1860 on the back surface of the lenses 1858 an aperture stop 1859 may include.

The tube 1730 can at its rear end 1734 be provided with a thread that fits into an internal thread on the lens mount of the camera assembly. The depth of the recording is determined by an adjusting sleeve 1736 controlled that on the tube 1730 can be postponed. One or more between the inner surface of the sleeve 1736 and the outer surface of the tube 1730 Traced keyways (not shown) can be used to restrict rotation of the sleeve relative to the tube and, at the same time, axial displacement movement (with axial direction parallel to the optical axis OA is to be understood). The sleeve 1736 is by one or more set screws 1760 held in a desired position. The threaded rear end 1734 the tube may define a standard C-mount thread size in one embodiment. The outer diameter of the tube 1730 is about 25 millimeters. The lens shown can create at least 3 megapixel resolution with moderate drift.

Final note

It goes without saying that the above-described embodiments provide a system which is extremely expedient, in particular in the case of a feature (or feature set) with small dimensions, such as, for example, an ID code, for capturing images from a relatively long distance. The effect of the adjustable lens assembly is weakened by the use of the positive lens assembly according to one embodiment. This arrangement is acceptable in the context of the target operating range and the desired feature dimension. In further embodiments, in the case of the (for example removable) lens arrangement, the adjusting lens is placed behind the fixed optic components which generate the drift-reduced feature. The adjusting lens thus represents the rearmost optical component of the arrangement in front of the sensor. The adjusting lens can be integrated in the lens arrangement / lens housing, or it can be a component of the camera assembly.

Exemplary embodiments of the invention have been described in detail above. Various modifications and additions can be made without departing from the spirit and scope of the present invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate to provide a variety of combinations of features in corresponding new embodiments. Furthermore, it should be noted that although the foregoing shows a number of separate embodiments of the device and the method according to the present invention, what has been described here is only illustrative of the application of the principles of the present invention. For example, various directional and alignment-related expressions used here such as "vertical", "horizontal", "upward", "downward", "lower, -r / -s", "upper, -r / -s", "lateral, -r / -s ”,“ front, -r / -s ”,“ rear, -r / -s ”,“ left, -r / -s ”,“ right, -r / -s ”and the like only as relative references and not used as absolute orientations with respect to a fixed coordinate system such as that of gravity. It is also contemplated that the system, even if the lens assembly shown here is integrated in a removable lens unit, can also be used in a fixed and / or permanently installed lens. Likewise, even if the lens sizes and spacings described above are used for the exemplary operating range, such sizes and spacings can be scaled up or down in arrangements that have similar relative parameters but a larger or smaller overall size. In addition, a “lens assembly” used and / or described here can consist of one or more discrete individual lenses that provide a desired optical effect. Accordingly, the present description is intended to be exemplary only and is in no way intended to limit the scope of the present invention.

Claims (18)

A vision system that compensates for the drift of an adjustable lens assembly (LL1, LL2, VL), comprising: an image sensor (130, 230, 910, 1010) operatively connected to a vision system processor (140); an adjustable lens assembly (LL1, LL2, VL) that changes shape or refractive index; and a fixed lens assembly configured to attenuate an action of the adjustable lens assembly (LL1, LL2, VL) over a predetermined operating range of the object, the fixed lens assembly and the adjustable lens assembly (LL1, LL2, VL) being part of an overall lens assembly that light onto the image sensor (130, 230, 910, 1010) focused, wherein an optical total strength of the overall lens assembly is mainly defined by the optical strength of the fixed lens assembly, so that the drift of the adjustable lens assembly (LL1, LL2, VL) is compensated, characterized in that the fixed lens assembly comprises : (a) a front lens (940) with a front concave surface (942) and a rear convex surface (944) and a central biconvex lens (952) spaced from the front lens (940), or (b) a front biconvex lens (1040 ) and a rear stacked lens assembly with a front positive lens, a central biconcave lens (1060) and a rear positive lens , or (c) a front plano-concave lens and a front negative lens (1442), a central stacked lens assembly with a biconvex lens (1446) and a plano-convex lens (1448) as well as a rear biconvex lens (1454) and a rear positive lens (1452), or (d) a front plano-convex lens and a front positive lens and a rear positive lens (1552) and a rear negative lens (1556), or (e) a front stacked lens assembly with a biconvex lens (1642) and a biconcave lens (1648) as well as a rear plano-convex and a lens (1654) rear negative lens (1656). Vision system after Claim 1 wherein the adjustable lens assembly comprises a liquid lens assembly (420, 920, 1020). Vision system after Claim 2 , wherein the liquid lens assembly (420, 920, 1020) can be changed over a range of approximately 20 diopters. Vision system after Claim 1 , the fixed lens assembly defining a positive optical power. Vision system after Claim 1 , wherein the fixed lens assembly and the adjustable lens assembly (LL1, LL2, VL) are accommodated in a lens barrel, which can be removed with respect to a camera assembly housing and to the image sensor (130, 230, 910, 1010), the image sensor (130, 230 , 910, 1010) is located in the camera assembly housing. Vision system after Claim 5 , wherein the camera assembly housing is electrically connected to the adjustment lens assembly (LL1, LL2, VL) by contact surfaces or by a cable assembly in order to operate and / or control it. Vision system after Claim 1 wherein at least one lens of the fixed lens assembly comprises a polymer material. Vision system after Claim 1 , wherein the fixed lens assembly defines an effective usable focal length range from about 0.3 meters to about 8 meters. Vision system after Claim 1 , wherein the adjustable lens assembly (LL1, LL2, VL) is located adjacent to a focal point of the fixed lens assembly. Vision system after Claim 9 , wherein the focus is either a front focus or a rear focus of the fixed lens assembly. Vision system after Claim 1 , wherein the fixed lens assembly comprises a front lens assembly and a rear lens assembly, with the adjustment lens assembly (LL1, LL2, VL) positioned between them. Vision system after Claim 12 , the rear lens assembly defining a positive optical power. Vision system after Claim 12 , wherein the front lens assembly has a pair of lenses each having front convex surfaces and rear concave surfaces and a lens having opposite concave surfaces, and the rear lens assembly has a lens having opposite convex surfaces. A lens system for a vision system that compensates for a drift effect of a lens assembly (LL1, LL2, VL), with an image sensor (130, 230, 910, 1010) that transmits image data to a processor, comprising: an adjustable lens assembly (LL1, LL2, VL); and a fixed lens assembly having a focal point, the adjustable lens assembly (LL1, LL2, VL) being located adjacent to the focal point, the fixed lens assembly and the adjustable lens assembly (LL1, LL2, VL) being part of an overall lens assembly, which light onto the image sensor (130, 230, 910, 1010), and an optical power of the overall lens assembly is mainly defined by an optical power of the fixed lens assembly, characterized in that the fixed lens assembly comprises: (a) a front lens (940) with a front concave surface (942) and one rear convex surface (944) and a central biconvex lens (952) spaced from the front lens (940), or (b) a front biconvex lens (1040) and a rear stacked lens assembly with a front positive lens, a central biconcave lens (1060) and a rear Positive lens, or (c) a front plano-concave lens and a front negative lens (1442), including a central stacked lens assembly he biconvex lens (1446) and a plano-convex lens (1448) as well as a rear biconvex lens (1454) and a rear positive lens (1452), or (d) a front plano-convex lens and a front positive lens as well as a rear positive lens (1552) and a rear negative lens (1556 ), or (e) a front stacked lens assembly with a biconvex lens (1642) and a biconcave lens (1648) as well as a rear plano-convex lens (1654) and a rear negative lens (1656). Lens system after Claim 14 wherein the adjustable lens assembly comprises a liquid lens assembly (420, 920, 1020). Lens system after Claim 15 , wherein the liquid lens assembly (420, 920, 1020) can be changed over a range of approximately 20 diopters. Lens system after Claim 16 , wherein the fixed lens and the adjustable lens assembly (LL1, LL2, VL) are accommodated in a lens barrel, which can be removed with respect to a camera assembly housing and to the image sensor (130, 230, 910, 1010), the image sensor (130, 230, 910, 1010) is located in the camera assembly housing. Lens system after Claim 17 , wherein the camera assembly housing is electrically connected to the adjustment lens assembly (LL1, LL2, VL) by contact surfaces or by a cable assembly in order to operate and / or control it.

Images