DE102018132699A1 - System and method for reducing drift in an adjustment lens of a vision system - Google Patents

Abstract

The present invention provides a vision system that is designed to compensate for optical drift that may occur, inter alia, with certain adjustment lens assemblies, such as liquid lens assemblies. The system includes an image sensor operatively connected to a vision system processor and an array lens assembly configured to control its focal length (eg, by the vision processor or other region determining device). A positive lens assembly is configured to attenuate an effect of the adjustment lens assembly over a predetermined operating range of the object as viewed from the positive lens assembly. The adjustment lens assembly is located adjacent to a front or back focus of the positive lens. The adjustment lens assembly includes, by way of example, a liquid lens assembly that may be inherently variable over a range of about 20 diopters. In one embodiment, the lens barrel has a C-mount lens base.

Description

RELATED APPLICATION

The present application is a continuation-in-part of co-pending United States Patent Application Serial No. 14 / 271,148, entitled SYSTEM AND METHOD FOR REDUCTION OF DRIFTING IN A VISION SYSTEM VARIABLE LENS (system and method for drift reduction on a vision system phasing lens), filed on Dec. 1, 2003 05. 06. 2014, the teachings of which are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present application relates to cameras used in machine vision, and more particularly to automatic focus lens assemblies.

BACKGROUND OF THE INVENTION

Vision systems for performing measurements, checks, object alignments, and / or decryption of symbol sets (eg, bar codes or, more simply, "ID" identifiers) are used in a wide range of applications in many industries. These systems are essentially based on the use of an image sensor which captures images (typically one-, two- or three-dimensional grayscale or color images) of the object or object and processes the images thus acquired by means of a built-in or connected vision system processor. The processor generally includes both processing hardware and non-transitory computer readable program instructions that perform one or more vision system processes to generate a desired output based on the processed image information. This image information is typically provided within an array of image pixels, each having different colors and / or intensities. In the example of an ID reader, the user or automated process captures an image of an object, assuming it contains one or more ID identifiers. The image is processed to recognize ID features that are subsequently decoded by a decoding process and / or processor to retrieve the information (eg, alphanumeric data) contained therein that 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 standalone unit, providing desired output data (eg, decoded icon information) to a downstream process such as a computer inventory tracking system or a logistics application ,

An exemplary lens design that may be desirable in certain vision system applications is the auto focus assembly (autofocus assembly). By way of example, such an autofocus lens can be simplified by a type of "adjusting lens" assembly (also described in more detail below), also known as a so-called "liquid lens assembly". In one form of liquid lens marketed by the French company Varioptic, two liquids of equal density - oil as an insulator and water as a conductor - are used. By changing the voltage conducted by a surrounding circuit through the lens, a change in the degree of curvature of the liquid / liquid interface can be achieved, which in turn results in a change in the focal length of the lens. Amongst others, 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 are among the main advantages that speak for the use of a liquid lens. The use of a liquid lens can desirably simplify installation, setup and maintenance of the vision system, eliminating the need to manually touch the lens. Compared with other autofocus mechanisms, the liquid lens has extremely fast response times. It is therefore also ideal for applications where the reading distances change from object to object (from surface to surface) or during the transition from reading an object to reading another object - such as when scanning a moving conveyor belt containing objects of different size / height (such as shipping crates) is the case. The ability to "dynamically" adjust focus 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 movable membrane that covers a liquid reservoir to adjust its focal length. A coil exerts pressure to change the shape of the diaphragm and thereby adjust the lens focus. The coil is moved by changing the input current within a preset range. 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 (eg, Varioptic, France) and operates faster. Due to thermal drift and other factors, there may generally be a change in calibration and focus adjustment during run time usage and over time. A variety of systems may be provided to compensate for and / or correct the focus changes and other factors. However, such balancing routines may require processing time (in the camera's internal processor), thereby slowing down the overall response time of the lens to reach a new focus. Likewise, such balancing routines (eg, for thermal drift) may be standardized and not adapted to the individual conditions of the lens, thereby being less reliable with respect to specific drift conditions that a lens may experience over time. It should be noted that the drift in a liquid lens z. For example, about 0.15 diopters / ° C (ie, some of the liquid lenses currently in production and / or Varioptic for specific commercial products). Some vision applications require +/- 0.1 diopter optical stability of the imager lens, especially when it comes to detecting small features from a distance.

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

OVERVIEW OF THE INVENTION

The present invention overcomes the disadvantages of the prior art by providing a vision system adapted to compensate for the optical drift that can occur in certain lens assemblies whose optical power is variable, the change in optical power (and thus the optical power) Focal length / focal distance where focal length = 1 / optical power) by controlling the lens shape and the refractive index of the lens, respectively. Such lens assemblies include, but are not limited to, liquid lens assemblies employing, for example, two fluids of equal density or a flexible membrane, and which are generally referred to herein as the "adjustment lens" assembly. The system includes an image sensor operatively connected to a vision system processor, and an adjustment lens assembly configured to control its focal length (eg, by the vision processor or other area determiner). A positive lens assembly is configured to attenuate an effect of the adjustment lens assembly over a predetermined operating range of the object as viewed from the positive lens assembly. The adjustment lens assembly includes, by way of example, a liquid lens assembly, and such a liquid lens assembly is generally changeable over a range of about 20 diopters. The positive lens assembly and the adjustment lens assembly are exemplarily housed together in a lens barrel which is detachable with respect to a camera body and the image sensor. The image sensor is located, for example, inside the camera housing. Likewise, the vision processor may be wholly or partially in the camera body. In one embodiment, the lens barrel has a C-mount lens base, and the positive lens assembly includes a dual 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 (eg a double lens) is between about 10 and 100 millimeters by way of example. Moreover, the recliner lens assembly (eg, the liquid lens assembly) is typically adjacent to, but still away from, a focal point of the positive lens assembly, which is the front or, more typically, the back / rear focus of the positive lens assembly can. The distance between the adjustment lens assembly and the focus may 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 adjustment lens assembly are part of an overall lens assembly that focuses light onto the image sensor. Thus, the optical power of the positive lens assembly "predominantly defines" an optical power of the overall lens assembly-in other words, the magnifying power / optical power is largely provided by the positive lens assembly, thereby minimizing the drift effect on the adjustment lens assembly.

In an exemplary embodiment, a drift compensating vision system is provided. The vision system includes an image sensor operatively connected to a vision system processor, an adjustment lens assembly whose shape or refractive index is changeable, and a fixed lens assembly adapted to attenuate an effect of the adjustment lens assembly over a predetermined operating range of the object as viewed from the positive lens assembly. Illustratively, the adjustment lens assembly includes a liquid lens assembly. This may be positioned between the image sensor and the fixed lens assembly and may be adjustable over a range of about 20 diopters. Moreover, the fixed lens assembly can define a positive optical power. The fixed lens assembly and the adjustment lens assembly are exemplarily housed in a lens barrel which is removable with respect to a camera assembly housing and the image sensor, wherein the image sensor may be located in the camera assembly housing. The camera assembly housing may be electrically connected to the adjustment lens assembly by contact pads or by a cable assembly for operating and / or controlling the same. The fixed lens assembly may include: (a) a front lens having a front concave surface and a rear convex surface and a central biconvex lens spaced from the front lens, and (b) a front biconvex lens and a rear stacking lens assembly having a forward positive lens, a center biconcave lens and (c) a front plano-concave lens and a front negative lens, a central stacking lens assembly having a biconvex lens and a plano-convex lens, a rear biconvex lens and a posterior positive lens, and (d) a front plano-convex lens and a front positive lens, and a (e) a front stacking lens assembly with a biconvex lens and a biconcave lens and a rear plano-convex lens and a rear negative lens. Additionally, at least one lens of the fixed lens assembly may comprise a polymeric material. For example, the fixed lens assembly may define an effective focal length range of about 0.3 meters to about 8 meters. The adjustment lens assembly may also be located, for example, adjacent a focal point of the fixed lens assembly. The focal point is either a front focus or a back focus of the fixed lens assembly. In some embodiments, the fixed lens assembly may include a front lens assembly and a rear lens assembly, wherein the adjustment lens assembly is positioned therebetween and the rear lens assembly may define a positive optical power. Additionally, in such embodiments, the front lens assembly may include 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 comprise a lens having opposite convex surfaces. For purposes of illustration, the fixed lens assembly and the adjustment lens assembly are part of an overall lens assembly that focuses light onto the image sensor, wherein optical power of the overall lens assembly is primarily defined by optical strength of the fixed lens assembly.

In another exemplary embodiment, an adjustment lens system is provided for a vision system having an image sensor that transmits image data to a processor. The system includes an adjustment lens assembly (eg, a liquid lens assembly). The system includes a fixed lens assembly with a focal point. The adjustment lens assembly is located adjacent to the focal point. The fixed lens assembly and the adjustment lens assembly may be part of an overall lens assembly that focuses light onto the image sensor. As a result of the optical strength of the positive lens assembly, the optical strength of the overall lens assembly can thus be predominantly defined. For example, the liquid lens assembly can be varied over a range of about 20 diopters. In some embodiments, the fixed lens assembly and the adjustment 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 assembly housing may be electrically connected to the adjustment lens assembly by contact pads or by a cable assembly for operating and / or controlling the same. The fixed lens system may, for illustrative purposes, comprise: (a) a front lens having a front concave surface and a rear convex surface and a central biconvex lens spaced from the front lens, and (b) a front biconvex lens and a rear stack lens assembly having a forward positive lens, a central one Or (c) a front plano-concave lens and a front negative lens, a central stacking lens assembly with a biconvex lens and a plano-convex lens and a rear biconvex lens and a posterior positive lens, and d ) a front plano-convex lens and a front positive lens and a rear positive lens and a rear negative lens, and (e) a front stacking lens assembly having a biconvex lens and a biconcave lens and a rear plano-convex lens and a rear negative lens.

list of figures

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

DETAILED DESCRIPTION

System Overview

1 shows a vision system 100 in details, that a visual system camera assembly 110 together with associated lens unit / assembly 120 contains. The structure of the lens unit 120 is described in more detail below. In one embodiment, the lens unit is 120 attached to the camera and may be removable using a specific or conventional mounting base, such as the well-known Cine mount. The camera includes a body / housing containing a plurality of operating components, such as an image sensor or imager 130 (shown in dashed lines) can be accommodated. In this embodiment, the imager is 130 functional with a built-in visual processor 140 which operates a variety of hardware and / or software processes, generally as a visual process 142 be designated. The visual process 142 may comprise a plurality of software applications configured to perform general or specific vision system tasks, such as ID tag (ID code) finding and decoding tasks, edge detection, blob analysis, surface inspection, robotic manipulation, and / or other operations. See, for example, For example, the example ID 144 , The processes 142 may also include various image capture and image manipulation applications, e.g. Histogram formation, thresholding, etc., which translates image data into a form more usable for vision system tasks. These objects and processes are known to those skilled in the art and may 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 preprocessed form (eg, as found, as yet un-decoded ID image data), or in fully processed form (eg, as decoded ID data) may be transmitted via a wired and / or wireless connection 144 to a suitable data processing system or processor, e.g. As an independent single computer or to a server system can be provided. Alternative systems such as mobile computing systems, cloud-based devices and the like may be provided in alternative implementations. The data processing system stores and manipulates the image-based data according to the user's request, such 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 (eg, the data processing device / processor 150 ) are instantiated and / or carried out, in a manner known to the person skilled in the art, via a suitable wired and / or wireless connection (eg the connection 144 ) with the camera 110 connected is.

It should be understood that the terms "process" and / or "processor" as used herein broadly should be construed to include a variety of electronic hardware and / or software based functions and components. In addition, a process or processor depicted here can be combined with other processes and / or processors or subdivided into different subprocesses or subprocessors. Such sub-processes and / or sub-processors may be combined in various ways according to present embodiments. Likewise, it is expressly contemplated that any function, process and / or processor listed herein may be constructed using electronic hardware, software consisting of program instructions resident on a non-transitory computer-readable medium, or a combination of hardware and software Software can be implemented or can. In a system arrangement, such processes / process functions may be referred to as occurring / present in a corresponding "module" or "element". For example, in an "ID read module" that performs those functions related to the reading and / or decoding of ID codes.

The lens assembly 120 is along the optical axis OA aligned (the plane of the sensor 130 usually arranged perpendicular to the axis). The lens assembly 120 and the sensor 130 form an object O from. The object O may, for example, have any two-dimensional (2D) or three-dimensional (3D) surface or shape that is partly or wholly in the field of view (field of view, FOV ) fits. In the example shown, the range / distance ( do ) of the object O to the camera 110 (eg to the focal plane of the sensor 130 ), but (according to an example embodiment) defines a predetermined operating range within which the object O is to represent.

By way of example, this embodiment compensates for potential optical drift in the course of time with an adjustment lens (eg, a liquid lens) that is part of the overall lens assembly 120 by defining for the vision system an operating range in which the influence of the optical power of the adjustment lens on the optical power of the overall lens assembly (including all the fixed lenses contained therein) is reduced. In this way, the drift is only a small component of the total firing power of the lens assembly. This exemplary arrangement is useful where the adjustable focal length range can be reduced. Thus, this system is useful in various embodiments - for example, in those where the distance ( do ) of the object surface relative to the focal plane is relatively constant or in which this distance ( do ) changed only by a small relative distance. For example, this system can be used in vision system applications that read from longer distances, with the required optical range representing only a small fraction (about 2 diopters) of the specified range of commercially available liquid lenses (20 diopters). As described above, the adjustment lens assembly of the embodiments contemplated herein may include a variety of types of lenses capable of varying the optical power. In particular, in some embodiments, the change in optical power (and hence the focal length / focus distance, where the focal length = 1 / optical power) is accomplished by controlling the lens shape and / or refractive index of the lens. Such adjustment lens assemblies include, but are not limited to, liquid lenses, and a variety of types of lenses, such as those having the same density fluids (from Varioptic) or those having a membrane (from Optotune), etc., can be used. Similarly, adjustment lenses can be used that work by other mechanisms, such as by means of electromechanical actuation.

II. Drift reducing lens assembly

Using the example of a further illustration of the basic idea of an embodiment shows 2 a ray trace diagram of a base optics assembly for an exemplary vision system 200 with an exemplary object O1 , an image sensor 230 and a generally illustrated adjustment lens (such as a liquid lens ( LL1 )). The object O1 is at a distance d1 from the adjustment lens LL1 positioned. This system has no additional lenses and that of the object O1 reflected rays 240 go through the adjustment lens LL1 and are, as shown, directly on the image sensor 130 focused. Thus, any (approximately drift-related) slight change in the focus of the adjustment lens LL1 to a potentially significant blurring condition that may affect the vision system's ability to provide a correct result.

In order to reduce this sensitivity for drift and other focus deviations in z. B. to take into account a liquid lens is now on 3 Reference is made to the generalized optical arrangement for a vision system 300 according to one embodiment. A positive (non-adjustable) fixed lens PL is at a predetermined distance d in front of the adjustment lens assembly (eg liquid lens assembly) LL2 along the optical path between the system and the imaged 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: $$\text{A}=\text{A}1+\left(1-\text{k}\right)*\text{A2}$$

und ist der Drift, der als Differential der optischen Stärke (dA) der Linse pro Einheitszeit (dT) (dA/dT) des Systems dargestellt ist, wie folgt: $$\text{dA}/\text{dT}=\text{dA1}/\text{dT}+\left(1-\text{k}\right)*\text{dA2}/\text{dT}$$

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 A this system 300 (in which A1 the optical power of the positive lens assembly PL . A2 the optical strength of the adjustment lens assembly LL2 and d the distance between the positive lens PL and the adjustment lens LL2 corresponds) as follows: $$\text{A}=\text{A1}+\text{A2}-\text{d}*\text{A1}*\text{A2}$$

When the distance between the adjustment lens LL2 and the positive lens PL is relatively large (eg d = k / A1 (where k = 0.5 ... 0.9 and the product of the strength of the positive lens A1 and the distance d represents; ie k = d * A1)), so the total optical strength A of the above-defined lens system with the starches A1 and A2 and the relative distance d as follows: $$\text{A}=\text{A}1+\left(1-\text{k}\right)*\text{A2}$$

and is the drift that is used as a differential of optical power ( there ) of the lens per unit time ( dT ) (dA / dT) of the system is as follows: $$\text{there}/\text{dT}=\text{<figure-callout id="1" label="dA" filenames="DE102018132699A1\_0012.png,DE102018132699A1\_0014.png" state="{{state}}">dA</figure-callout> 1}/\text{dT}+\left(1-\text{k}\right)*\text{dA2}/\text{dT}$$

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

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

It will be up now 4 Referring to FIG. 1 in detail, 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 dashed lines as a cable 410 and connectors 412 shown) extending from the adjustment lens assembly (eg, liquid lens assembly). 420 to a spot on the camera body 110 extend that with appropriate, the visual processor 140 related control processors / components. It should be noted that the exemplary liquid lens assembly 420 , which may be a diaphragm type, a fluid density type, or an equivalent type, within a tube 430 is included and the line 410 is designed so that it extends from a point on the tube 430 extends out. This connection allows control signals to be supplied to the liquid lens assembly (eg, by current and / or voltage modulation) to alter and adjust the focus of the liquid lens assembly 420 in response to enable commands from the processor. The correct focus can be determined and / or adjusted using a variety of techniques known to those skilled in the art, such as using the crispness of imaged edges after trying various focus adjustments, and / or using an external ranging device , Although a separate cable connection with associated connector is used on the camera body in the embodiment shown, the connection arrangement can also be located inside the tube 430 be provided - z. In the form of mutually aligned contact surfaces and / or contact rings (on the lens and the camera body) that communicate with each other when the lens assembly 120 is attached to the camera body.

The tube 430 The lens assembly in this embodiment is the form factor of a conventional C-mount lens with a corresponding thread base 440 measured and arranged. The pictured external thread of the tube base (the flange 440 ) is designed so that it fits to a corresponding internal thread (not shown) on the camera body. It is a conventional thread size (eg 1 inch X 32). It should be appreciated that the camera body may include a variety of accessories and functional components, such as a ring illuminator surrounding the lens, and / or external lighting assembly terminals. Such accessories and / or components may be attached to the camera to accomplish various vision system tasks. The tube 430 can be constructed from a variety of materials, e.g. As cast or machined aluminum alloy. The threaded base allows the tube and the associated overall lens assembly contained therein to be removably attached to the camera body and replaced with other lens types as needed by the manufacturer or user. Although the form factor of a C-mount base is used in this embodiment, in alternative embodiments, any suitable lens base shape may be used which enables the placement of a liquid lens or other serviceable adjustment lens. For example, an F-mount lens base can also be used.

The dimensions of the lens barrel 430 are in 4 shown by way of example without limitation. As shown, the tube outer diameter ODL be about 28 to 29 millimeters in one embodiment. This takes into account the general size constraints / parameters of a C-mount lens. Likewise, the length is OLL of the tube 430 from the front end 432 to the thread base 440 for illustrative purposes, about 32 to 34 millimeters. The distance DS between the lens base 440 and the focal plane of the image sensor 130 is about 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, referring hereinafter to 4A , The positioning of the internal optical components of the lens is described in detail. A positive lens assembly 450 that have a relative to the diameter of the adjustment lens ( 420 ) of 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 formed at the front end of the tube recess 454 , The positive lens 450 is at her Front by one 456 Threaded ring attached. It should be noted that in alternative embodiments the arrangement is highly variable and in alternative embodiments a variety of attachment and / or attachment mechanisms may be used. With the positive lens 450 is a double achromatic 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 total lens assembly is 25 millimeters. For illustrative purposes, here 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 18.85 millimeters (where positive and negative radii respectively represent directional references relative to the imaged object with positive radii aligned toward the object and negative radii aligned with 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 (eg with double lens) is commercially available from Edmund Optics Inc., Barrington, NJ, under the item number 32321. In this embodiment, the distance ODLF between the lens front side and the sensor plane according to an embodiment approximately 49 millimeters. 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 adjustment lens assembly (eg 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 adjustment lens assembly 420 a liquid lens of the model Arctic 416 , available from Varioptic, France. The exemplary adjustment lens assembly has a focus range of about 20 diopters (ie, from 5 inches 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 board 472 mounted lens unit 470 with a central aperture 474 , which is aligned along the optical axis and through the focused light to the sensor 130 arrives.

The lens assembly 130 can by means of an integral or formed as a unit spacer, a shoulder assembly and / or a support structure 460 inside the tube 430 be stored. The supporting structure 460 ensures that the adjustment lens assembly 420 in an appropriate orientation with respect to the optical axis OA remains. The distance DLR from the back of the positive lens to the front of the adjustment lens unit 470 is 18.0 millimeters in this embodiment. It should be noted that the image sensor 130 In one embodiment, a conventional CMOS sensor with a size of 0.5 inches ( 6 , 9 mm (horizontal) by 5.5 mm (vertical) - SW in 5 ).

It will now be on the 5 to 7 Referring to Figure 4, the vision system and lens assembly operate at a plurality of focal lengths within the operating range of the system. The object O is thus located in the ray tracing diagrams of the 5 . 6 and 7 each at three different, exemplary intervals DO1 . DO2 and DO3 , For example, the distance is DO1 about 219 millimeters, the distance DO2 about 430 mm and the distance DO3 about 635 millimeters. Within this range, the optical power of the adjustment 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 of 219 to 635 millimeters is associated with a change of 6.9 diopters. In comparison, in a conventional arrangement where the adjustment lens is mounted at a close distance to the front lens, a system structure with the illustrated adjustment lens assembly typically requires a change of 3.3 diopters. Thus, the exemplary system effectively reduces the potential drift by more than a factor of 2 relative to a conventional arrangement.

More generally, the recliner lens assembly (eg, liquid lens assembly) is adjacent to, but still away from, a focal point of the positive lens assembly, which may be the front or, more typically, the back / rear focus of the positive lens assembly. It is understood that the positioning adjacent to the focal point allows the adjustment lens to contribute to the overall thickness of the lens system. The distance between the adjustment lens assembly and the focus may 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 will be made to the diagram 8th taken, wherein a positive lens assembly PL along the optical axis OA is positioned, with an adjustment lens VL adjacent to the focal point FP the positive lens is located. Between the positive lens PL and the focal point 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 by k = 0.9 to 0.5 (ie 0.9 * F to 0.5 * F). The distance between the positive lens PL and the adjustment lens VL is thus k * F (ie 0.1 * F to 0.5 * F). This is the positive lens assembly PL and the adjustment lens assembly VL Part of a total lens assembly LA , which focuses light onto the image sensor, whereby a total optical power of the overall lens assembly is "predominantly" defined by the optical power of the positive lens assembly - in other words, the magnification power / optical power is largely provided by the positive lens assembly, thereby minimizing the drift effect on the adjustment lens assembly becomes.

It will now be on the 9 and 10 Referring to FIG. 2, there are shown two embodiments of drift reducing lens assemblies according to respective embodiments. The tables below also each provide corresponding example parameters for each lens element. 9 is a lens arrangement 900 in conjunction with an image sensor 910 of (eg) conventional type. In this embodiment, the adjustment lens comprises a liquid lens assembly 920 , The pictured rays 930 are from an object (not shown) at a distance of (eg) 200 millimeters from the first lens 940 can be placed in the lens assembly 900 reflected in it. As an example, without limitation, this lens includes 940 a front concave surface 942 and a rear convex surface 944 , This lens may comprise a polymer such as polycarbonate (or other optically suitable material). A central lens assembly includes a front compound lens 950 with a convex lens 952 that has a front surface 954 and a back surface 956 having. This fits with a concave lens 958 with a convex surface of similar radius and a posterior convex surface 960 together. It should be noted that the lens element (s) ( 950 ) may also be constructed of polycarbonate (or other optical material). A disc-shaped optical element 970 (eg an IR filter) with infinite radii on each side (eg on parallel planes) is located behind the compound lens assembly 950 , The Rays 930 run from the disk 970 on the adjustment lens assembly (liquid lens assembly) 920 out together. This exemplary assembly can essentially be found on the Arctic 416 Varioptic from France or another suitable lens (eg a liquid lens). It includes a front cover 980 that with the lens control circuit 990 connected lens element 982 , the aperture diaphragm 984 (with an associated radius of 341.763 millimeters) and a rear cover 986 , The lens control circuit may be operatively connected to the vision system described above. This item is adapted to focus on the image sensor 910 counteract a drift based on a variety of conditions described above. The spacing between the liquid lens assembly 920 and the imager can be about 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 as well as the spacing therebetween may be modified according to the pertinent art. Likewise, the recliner lens assembly may include a variety of different types of lenses operated according to different physical principles. For example, a liquid lens with membrane as well as mechanical lens types, which are available from the Swiss company Optotune, can be used as replacement.

In 10 to which reference is now made, is another embodiment of a lens assembly 1000 which can provide low drift over a given operating range. This arrangement includes an image sensor 1010 of conventional type and an adjustment lens assembly (liquid lens assembly) 1020 , The Rays 1030 become from a (not shown) object in a range of (for example) 80-100 millimeters to a front convex lens 1040 reflected back. 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 rear surface 1064 , The Rays 1030 step out of this lens 1060 out and into the adjustment lens assembly (eg the liquid lens assembly) 1020 introduced, which is located in the middle of the optical assembly in this embodiment, 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 (where an aperture stop has a radius of 10.101 millimeters) and is passed through a lens controller 1090 controlled, which is similar operable as the controller also described above 990 , Alternative embodiments of the adjustment lens assembly may optionally be used, as described above with reference to the arrangement 900 has been described. From the liquid lens assembly (eg, the liquid lens assembly) 1020, the rays become 1030 in a convex lens 1080 which is 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 disk-shaped filter (eg an IR filter) 1088 can be behind the convex lens 1080 are located. This is located in the current embodiment at a distance of about 10 - 12 millimeters in front of the image sensor. The lenses are made of an optical glass in this embodiment, for example, without limitation, and one or more of the lenses (or other optical elements) are made of another acceptable material, such as polycarbonate or other equivalent material suitable for use can be.

The lens arrangements described above 900 and 1000 may be adapted to be enclosed in a lens package with (eg) a conventional camera base mount, such as a "C-mount" mount described above. Suitable electrical connectors may be provided between the lens body and the camera base to facilitate control of the adjustment lens assembly. The electronics of the control circuit may be housed in whole or in part in the lens body, or suitably also in the camera body.

As an example, without limitation, the lenses of the various embodiments herein may 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 any) the associated front and back faces of each structure or element within the overall assembly (from left to right) are respectively 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 2 944 -6.977 4,121 4.00 3 Lens 950 954 11.027 3,012 480R + PC 4.00 4 956 -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 10 variable 1.15 11 infinite (flat) 0,300 2.00 12 infinite (flat) 13.884 2.00 13 Picture 910

The table below is for the lens assembly 1000 ( 10 ), where (if any) the respective front and back surfaces of each structure or element within the overall assembly (from left to right) are indicated in the order of 0-14, respectively: 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 2 1044 49.620 0.256 4.00 3 Lens 1046 1048 19.922 1,770 N-SF6 4.00 4 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 10 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 further 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 adjustment lens systems or optical feedback systems. By way of non-limiting example, such arrangements are described in commonly assigned U.S. Patent Application Serial No. 8,576,390, entitled "SYSTEM AND METHOD FOR DETERMINING AND CONTROLLING FOCAL DISTANCE IN A VISION SYSTEM CAMERA" (system and method for zooming and control of focal length) Vision system camera), by Nunnink, are shown and described and incorporated by reference herein as convenient background information. Further, reference is made to the US patent application serial number 14 / 139.867 , entitled "CONSTANT MAGNIFICATION LENS FOR VISION SYSTEM CAMERA" (Constant Magnifying Lens for a Vision System Camera), by Nunnink; and to the US patent application serial number 13 / 800.055 , entitled LENS ASSEMBLY WITH INTEGRATED FEEDBACK LOOP FOR FOCUS ADJUSTMENT (lens assembly with integrated feedback-tuning loop for focus adjustment), by Nunnink et al. The present application illustratively provides a detachably mountable vision system camera lens assembly including an integrated autofocus liquid lens unit in which the lens unit compensates for focus changes using a feedback control circuit integrated with the lens assembly body. The feedback control circuit receives motion information related to the actuator, such as a lens coil (which biases the electrically controllable diaphragm to varying degrees) from a position sensor (eg, a Hall sensor) and uses that information internally to detect motion changes from the set position the lens at a target lens focal length setting differ, to correct. The position sensor may be a single unit or a combination of different, differently arranged with respect to the actuator or coil, discrete sensors, with which or with which movements are measured at various locations in the area around the lens unit around. For the sake of illustration, the feedback circuit may be connected to one or more temperature sensors that adjust the lens setting position for a particular temperature value. In addition, the feedback circuit may communicate with an accelerometer which senses the direction of gravity action and thereby corrects for any potential sag (or other orientational deformation) of the lens diaphragm based on the spatial orientation of the lens.

III. Drift reducing lens assembly

In the 11 - 18 For example, various embodiments of a drift-obstructing lens are described which enable area-extended reading of object features (eg, ID codes) for use in various camera assemblies and associated applications, including portable and stationary devices. With the present lens arrangements, focal lengths of up to about 8 meters can be imaged. In general, the exemplary arrangements provide a focus adjustable lens (eg, a liquid lens) positioned behind the remainder of the solid lens optic package so that the adjustment lens is located generally posteriorly on the lens assembly between the solid optics package and the camera image sensor. In 11 to which reference is now made, is a lens assembly 1100 shown. This arrangement is applicable to a 12 millimeter lens (f = 12). As shown, a relative scale scale becomes 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 of three smaller-diameter lenses 1134 (positive), 1136 (biconcave) and 1138 (positive, with opposite orientation) provided. In this embodiment, the solid-state pack is 1120 provided in a separate lens housing while an adjustment focus lens assembly 1140 is mounted within the vision system housing (eg, in a portable ID reader, as described in the commonly assigned US patent application serial number 14 / 550.709 titled IMAGE MODULE INCLUDING MOUNTING AND DECODER FOR MOBILE DEVICES (image module, including mobile device mount and decoder), filed November 21, 2014). As an example, without limitation, the adjustment lens assembly 1140 the liquid lens mechanism described above available from the Swiss company Optotune. Alternatively, the adjustment lens assembly may include any serviceable, manually or electronically adjustable lens assembly, including those previously described, available from the French company Varioptic. The adjustment lens assembly 1140 may be connected (via a cable, printed circuit traces, etc.) to the vision system processor or to another controller that allows focal length adjustment of the lens. This controller may be integrated with the feedback system described above. The adjustment lens assembly 1140 is, as appropriate, optionally equipped with one or more filters and / or dust covers. An aperture stop 1142 is also provided in this embodiment. The adjustment lens assembly 1140 focuses light (the rays 1150 ) on the image sensor 1152 in view of 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 about 15.2 millimeters. The distance 1162 between the back surface of the rear lens 1138 and the image plane (the image sensor 1152 ) is about 10.26 millimeters. As an example, define the approximate parameters of the arrangement 1100 an aperture F / # at 7; a 3 millimeter image radius (ie 1/3 inch for a 1.2 megapixel sensor, up to a 5.0 megapixel sensor); a RMS spot radius of 1.7 μm at 3 mm image height; and a measured distortion of less than 3% - 4%.

The table below is for the lens assembly 1100 ( 11 ), where (if any) the respective front and back surfaces of each structure or element within the overall assembly (from left to right) are indicated in the order of 0-16, respectively: 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 2 infinite (flat) 0,200 2.50 3 Lens 1132 11.175 1,300 N-SK16 2.50 4 -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 aperture 1142 0,150 multiple 0.63 10 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 Picture 1160

It should be noted that the lens parameter tables presented above and below are only to be considered as examples of a wide range of possible conversions. It will be understood by those skilled in the art that any or all of the present lenses and / or optical components may be modified by utilizing various 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 the Festoptikpackung 1120 equivalent. The lens elements are in a tube housing 1210 which is made of aluminum or another usable material. The lens elements are numbered similar to their equivalents in the assembly 1120 out 11 , The base 1230 the lenses 1200 may be in any convenient format - for example, a C-mount thread base (ie, 1 inch X 32 threads per inch) may be specified for the overall length of the tube. Alternatively, an M8x0.5 thread may be specified for the overall length of the tube, or in both cases for a reasonable portion thereof. As in the cross section from 13 shown, can be an aperture 1310 between the biconcave lens 1136 and the farthest positive lens 1138 are located. The in the tube 1210 contained lenses 1130 - 1138 be 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 threaded onto the tube and located at a location therealong to adjust the focal length of the lens assembly with respect to the image plane. In one embodiment, the ring 1250 after successful, correct positioning on the lens tube 1210 be attached to the tube in a permanent / semi-permanent manner by means of a threadlock compound, an adhesive or other attachment mechanism (eg, a set screw, a pin, etc.). When screwing the lens into the lens holder of the device comes the ring 1250 against the bracket to concern, thus providing the desired spacing. In one embodiment, the total lens length is 1340 about 6.9 millimeters and is the set distance 1350 between the back surface of the retaining ring 1250 and the picture plane 1360 about 12,15 mm.

The 14 - 18 Form versions of a drift reducing lens assembly in various manners, which may include the adjustment lens in its overall construction, and which may be used (eg) in stationary vision systems, such as ID readers used in logistics and object tracking applications.

In 14 to which reference is now made, is a 16 millimeter lens assembly 1400 shown. This arrangement can be with a housing 1410 which is the adjustment lens assembly (eg the liquid lens assembly). 1430 in the overall package. The lens assembly is via a cable 1432 or otherwise connected to a connector (s) on the camera or other vision system housing that 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 may be incorporated into or attached to the lens housing to perform some or all of the functions of the adjustment lens control.

The lens arrangement 1400 includes a front negative lens 1440 followed by a smaller diameter sized negative lens 1442 , another biconvex lens 1444 and a smaller diameter sized double lens 1445 consisting of a biconvex lens 1446 and a plano concave lens 1448 , A second, smaller in diameter dimensioned double lens 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 adjustment 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 scale given in millimeters 1470 is shown and the rear focal length 1480 between the back of the adjustment lens 1430 and the image plane on the surface of the image sensor 1490 is set at about 8.5 millimeters - using (eg) convenient adjustment rings, bases, brackets, etc., which should be understood by those skilled in the art. As in 14A In short, this creates an image circle of about 8 millimeters in diameter. This lies within the maximum image circle 1496 (about 8.83 millimeters) of the illustrated exemplary sensor 1490 , which is a CMOS image sensor model IMX265 (the Japanese company Sony). That is, the picture circle 1496 circumscribes the corners of the rectangular circumference 1495 , which is the usable arrangement of image pixels for the sensor 1490 represents. Other image sensors, such as the one through the rectangle 1494 defined pixel arrangement are characterized by a different (in this example smaller - eg 7.66 millimeters) Bildkreisabmessung ( 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 about 16.2 to 16.6 millimeters, an aperture size of F8, an overall length of about 27.9 millimeters, a focus range of 1.0 - 4.0 meters, and an adjustment lens operating range of about 0, 0 to 2.5 dioptres. Within this range, there is theoretically a 2.5-fold lower drift than 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 is for the lens assembly 1400 ( 14 ), where (if any) the respective front and back surfaces of each structure or element within the overall assembly (from left to right) are indicated in the order of 0-20, respectively: 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 2 6,657 1,000 3,000 3 Lens 1442 14.130 2,000 N-SK16 3,000 4 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 10 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 aperture 1458 1,000 multiple 0,898 16 Liquid lens 1430 variable multiple 1,600 17 infinite (flat) 9,740 1,600 18 Sensor window 1490 infinite (flat) 0,400 D263T 19 infinite (flat) 0,125 20 Picture 1494

In 15 to which reference is now made, is a 25 millimeter lens assembly 1500 shown. This arrangement can be with a housing 1510 which is the adjustment lens assembly (eg the liquid lens assembly). 1530 in the overall package. The lens assembly is, as described above, 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 smaller diameter plano-convex lens 1542 and a double lens 1544 consisting of a biconvex lens 1546 and a biconcave lens 1548 , A second, smaller in diameter dimensioned double lens 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 adjustment 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 scale given in millimeters 1570 is shown and the rear focal length 1580 between the back of the adjustment lens 1530 and the image plane on the surface of the image sensor 1590 (e.g., about an 8-millimeter image circle) is set to about 8.5 millimeters - using (eg) appropriate adjustment rings, bases, brackets, etc., which should be understood by those skilled in the art. Other parameters of the lens assembly include a focal length of about 24.2 to 25.2 millimeters, an aperture size of F8, an overall length of about 27.6 millimeters, a focus range of 1.0 - 4.0 meters, and an adjustment range of the adjustment lens about 0.0 to 4.0 diopters. Within this range, there is theoretically four times less drift than 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 is for the lens assembly 1500 ( 11 ), where (if any) the respective front and back surfaces of each structure or element within the overall assembly (from left to right) are indicated in the order of 0-16, respectively: 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 2 infinite (flat) 0,300 6,071 3 Lens 1542 24.589 1,429 N-SK16 4,286 4 179.888 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 10 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 aperture 1558 1,429 multiple 0,850 16 Liquid lens 1530 variable multiple 1,600 17 infinite (flat) 8,500 1,600 14 Sensor window 1590 infinite (flat) 0,400 D263T 15 infinite (flat) 0,125 16 Picture 1594

In 16 to which reference is now made, is a 35 millimeter lens assembly 1600 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 mailing, etc.) where objects of different sizes are handled. This lens arrangement 1600 can with a housing 1610 (in 16 shown as a dashed box and described in more detail below), which is the adjustment lens assembly (eg, the liquid lens assembly). 1630 in the overall package. The lens assembly is, as described above, via a cable 1632 or otherwise connected to a connector / contacts.

The lens arrangement 1600 comprises a front, large-diameter plano-convex lens 1640 followed by a smaller diameter sized biconvex lens 1642 , stacked with a double lens 1644 , consisting of a positive lens 1646 and a biconcave lens 1648 , A second, smaller in diameter dimensioned double lens 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 adjustment 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 scale given in millimeters 1670 is shown and the rear focal length 1680 between the back of the adjustment lens 1630 and the image plane on the surface of the image sensor 1690 (eg, an 8-millimeter image circle) is set to about 8.5 millimeters. Other parameters of the lens assembly include a focal length of about 32.4 to 34.8 millimeters, an aperture size of F8, a total length of about 49.6 millimeters, a focus range of 1.0 - 4.0 meters, and an operating range for the adjustment lens of about 0.0 to 6.5 diopters. Within this range, there is theoretically a 6.5-fold lower drift than a conventional design. The RMS spot radius is less than 3.4 microns in extreme field of view position (FOV position).

The table below is for the lens assembly 1600 ( 16 ), where (if any) the respective front and back surfaces of each structure or element within the overall assembly (from left to right) are indicated in the order of 0-20, respectively: 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 2 infinite (flat) 10,000 8,500 3 Lens 1642 20.856 3,000 N-SK16 6,000 4 -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 10 Double lens 1650 8,787 2,400 N-SF2 + N-BK7 3,500 11 9,034 1,500 3,500 12 -2,195.069 0,500 2,500 13 Lens 1656 11.052 1,000 N-BK7 3,500 14 5.526 0,500 2,500 15 Aperture aperture 1658 2,000 0,892 16 Liquid lens 1630 variable multiple 1,600 17 infinite (flat) 8,500 1,600 18 Sensor window 1690 infinite (flat) 0,400 D263T 19 infinite (flat) 0,125 20 Picture 1694

The table below is for the lens assembly 1800 ( 18 ), where (if any) the corresponding front and back surfaces of each structure or element within the overall assembly (from left to right) are indicated in the order of 0-22, respectively: 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 2 infinite (flat) 3,500 10,750 3 Lens 1842 infinite (flat) 2,000 N-SK16 9,500 4 -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 10 Lens 1852 24.550 3,400 N-SK16 7,500 11 300000 1,000 7,000 12 Lens 1854 -300000 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 17 Lens 1858 30,000 1,500 N-SK16 4,000 18 17.140 0,500 3,000 19 Aperture aperture 1859 0.987 20 Liquid lens 1860 variable multiple 1,600 21 infinite (flat) 9.103 1,600 22 Picture (not shown)

In the 17 and 18 to which reference is now made, 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 similar to those previously described in 16 described arrangement 1600 functionally similar or identical. The housing may be formed of any suitable material (eg, an aluminum alloy) and in various shapes. As shown, the housing includes 1710 a front end 1720 , a main tube 1730 and a back end 1740 , With further reference to 18 becomes the front of the lens 1720 screwed into an internal thread in an extended flange 1820 of the main tube 1730 is trained. It should be noted that in this or other embodiments, an optional filter (eg, a red bandpass filter) 1840 may be attached to the front of the lens. The overall diameter DF of the front end 1720 the lens is about 27.5 millimeters. In general, the filter may be 1840 to trade a commercially available thread filter with reasonable optical specifications (eg visible wavelength bandpass, 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 housed. A biconcave lens 1850 is behind the double lens 1844 stacked. A smaller diameter sized pair of oppositely directed plano-convex lenses 1852 and 1854 is behind the biconcave lens 1850 intended. A diameter smaller dimensioned double lens 1856 defines a negative lens behind the lenses 1852 and 1854 , This double lens 1856 is behind a farthest positive lens 1858 , The adjustment lens (ie the liquid lens) 1860 is behind the lenses 1858 , It is characterized by an annular and threaded retaining ring 1862 who is in a rear collar 1864 with (eg) an M13 x 0.5 female thread, in the smaller diameter rear end 1740 recorded. The inner diameter IDC the collar is about 13 millimeters (thread area) and the outside diameter ODC is about 14 mm and its axial length LC can be about 3.1 mm. The retaining ring 1862 can a slot 1866 comprise for tightening the ring by a sheet-shaped tool of appropriate size and shape. It should be noted that the lens arrangement 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 threaded, which fits into an internal thread on the lens mount of the camera assembly. The depth of the shot is through an adjustment sleeve 1736 controlled on the tube 1730 is deferrable. One or more between the inner surface of the sleeve 1736 and the outer surface of the tube 1730 formed splines (not shown) can be used to restrict rotation of the sleeve relative to the tube and at the same time an axial displacement movement (under axially a direction parallel to the optical axis OA to understand). The sleeve 1736 is by one or more screws 1760 held in a desired position. The threaded, rear end 1734 of the tube may in one embodiment define a standard C-mount thread size. The outer diameter of the tube 1730 is thus about 25 millimeters. The imaged lens can provide at least a 3 megapixel resolution with moderate drift.

concluding remark

It should be understood that the embodiments described above provide a system which is particularly useful in a feature (or feature set) of small dimensions, such as an ID code, for relatively long distance image capture. The effect of the recliner lens assembly is mitigated by the use of the positive lens assembly according to one embodiment. This arrangement is acceptable within the scope of the desired operating range and the desired feature size. In further embodiments, in the (eg, detachable) lens assembly, the adjustment lens is placed behind the fixed optics components that generate the drift-reduced feature. The adjustment lens thus represents the rearmost optical component of the arrangement in front of the sensor. The adjustment lens can be integrated in the lens arrangement / the lens housing, or it can be a component of the camera assembly.

In the foregoing, exemplary embodiments of the invention have been described in detail. Various modifications and additions may 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 as appropriate with features of other described embodiments to provide a variety of feature combinations in corresponding new embodiments. It should also be understood that although the foregoing shows a number of separate embodiments of the apparatus and method of the present invention, what has been described herein is merely illustrative of the application of the principles of the present invention. For example, various directional and orientation-related expressions used herein, such as "vertical", "horizontal", "up", "down", "lower, -r / -s", "upper, -r / -s", "lateral," -r / -s "," front, -r / -s "," back, -r / -s "," left, -r / -s "," right, -r / -s "and the like only as relative references and not used as absolute orientations relative to a fixed coordinate system such as that of gravity. It is also contemplated that, although the imaged lens assembly is incorporated herein in a detachable lens unit, the system may also be used in a fixed and / or fixed mountable lens. Likewise, although the above-described lens sizes and spacings are used for the exemplary operating range, such sizes and spacings may be scaled up or down to scale for assemblies having similar relative parameters but greater or lesser overall size. Moreover, a "lens assembly" used and / or described herein may be comprised of one or more discrete lenslets that provide a desired optical effect. Accordingly, the present description is intended to be merely exemplary in nature and, in no way limit the scope of the present invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 14139867 [0033]
• US 13800055 [0033]
• US 14550709 [0034]

Claims (21)

Vision system with drift compensation comprising: an image sensor in operative communication with a vision system processor; an adjustment lens assembly that changes its shape or refractive index; and a fixed lens assembly adapted to attenuate an effect of the adjustment lens assembly over a predetermined operating range of the object. Visual system after Claim 1 wherein the adjustment lens assembly comprises a liquid lens assembly. Visual system after Claim 2 , wherein the liquid lens assembly can be changed over a range of about 20 diopters. Visual system after Claim 1 wherein the fixed lens assembly defines a positive optical power. Visual system after Claim 1 wherein the fixed lens assembly and the adjustment lens assembly are housed in a lens barrel detachable with respect to a camera assembly housing and the image sensor, the image sensor being in the camera assembly housing. Visual system after Claim 5 wherein the camera assembly housing is electrically connected by contact surfaces or by a cable assembly with the Verstelllinsenbaugruppe to operate and / or to control these. Visual system after Claim 1 wherein the fixed lens assembly comprises: (a) a front lens having a front concave surface and a rear convex surface and a central biconvex lens spaced from the front lens, and (b) a front biconvex lens and a rear stacking lens assembly having a forward positive lens, a central one And (c) a front plano-concave lens and a front negative lens, a central stacking lens assembly with a biconvex lens and a plano-convex lens, a rear biconvex lens and a posterior positive lens, and (d) a front plano-convex lens and a front positive lens, respectively (e) a front stacking lens assembly having a biconvex lens and a bi-concave lens and a posterior plano-convex lens and a rear negative lens. Visual system after Claim 7 wherein at least one lens of the fixed lens assembly comprises a polymeric material. Visual system after Claim 7 wherein the fixed lens assembly defines an effective focal length range of about 0.3 meters to about 8 meters. Visual system after Claim 1 wherein the adjustment lens assembly is located adjacent a focal point of the fixed lens assembly. Visual system after Claim 9 wherein the focus is either a front focus or a back focus of the fixed lens assembly. Visual system after Claim 1 wherein the fixed lens assembly includes a front lens assembly and a rear lens assembly with the adjustment lens assembly positioned therebetween. Visual system after Claim 12 wherein the rear lens assembly defines a positive optical power. Visual system after Claim 12 wherein the front lens assembly comprises 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 comprises a lens having opposite convex surfaces. Visual system after Claim 1 wherein the fixed lens assembly and the adjustment lens assembly are part of an overall lens assembly that focuses light onto the image sensor and optical power of the overall lens assembly is primarily defined by optical strength of the fixed lens assembly. An adjustment lens system for a vision system having an image sensor that transmits image data to a processor, comprising: an adjustment lens assembly; and a fixed lens assembly having a focal point, wherein the adjustment lens assembly is located adjacent to the focal point, the fixed lens assembly and the adjustment lens assembly being part of an overall lens assembly that focuses light onto the image sensor and optical power of the overall lens assembly is primarily defined by optical power of the positive lens assembly , Lens system after Claim 16 wherein the adjustment lens assembly comprises a liquid lens assembly. Lens system after Claim 17 , wherein the liquid lens assembly can be changed over a range of about 20 diopters. Lens system after Claim 16 wherein the fixed lens and the adjustment lens assembly are housed in a lens barrel detachable with respect to a camera assembly housing and the image sensor, the image sensor being in the camera assembly housing. Lens system after Claim 19 wherein the camera assembly housing is electrically connected by contact surfaces or by a cable assembly with the Verstelllinsenbaugruppe to operate and / or to control these. Lens system after Claim 16 wherein the fixed lens assembly comprises: (a) a front lens having a front concave surface and a rear convex surface and a central biconvex lens spaced from the front lens, and (b) a front biconvex lens and a rear stacking lens assembly having a forward positive lens, a central one And (c) a front plano-concave lens and a front negative lens, a central stacking lens assembly with a biconvex lens and a plano-convex lens, a rear biconvex lens and a posterior positive lens, and (d) a front plano-convex lens and a front positive lens, respectively (e) a front stacking lens assembly having a biconvex lens and a bi-concave lens and a posterior plano-convex lens and a rear negative lens.

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