OPTICAL IMAGE CAPTURE UNIT AND METHOD FOR DETERMINING A SIZE RESERVE

Description

[0001] The present invention relates to an optical image capture unit for capturing a code and a method for determining a size reserve for the minimum resolution limit of a code contained in an image signal.

[0002] Optical image capture units for capturing codes are generally known from the prior art. The known image capture units comprise optical capture means that generate an image signal from a capture area to completely capture a code applied to an object. The resolution of the image signal depends on the properties of the optical capture means and the system configuration, i.e., the distance between the image capture unit and the object bearing the code. The properties of the capture means are determined on the hardware side by the selection of the lens, the size of the sensor capture area, the number of pixels in the sensor capture area, and / or the pixel size of the sensor capture area.

[0003] In this context, EP 3 789 906 A1 is known from the prior art, which discloses an optical image capture unit with optical capture means for generating an image signal, wherein the module size and thus the resolution of the code in the image signal is determined via the brightness distribution.

[0004] For the image capture units to function correctly, it is important that the code applied to the outside of an object is captured in the generated image signal with a sufficiently high resolution. A sufficiently high resolution is always present when the smallest unit of the code, i.e., the smallest code unit, can be correctly captured and thus decoded. This ensures the readability of the entire code, which, in particular, contains information about the object. At the same time, it is also desirable that the image signal be able to capture the largest possible detection area with a sufficiently high resolution.

[0005] When configuring and / or commissioning the optical image capture unit, the user is faced with the challenge of finding the application-specific optimum between the largest possible detection range on the one hand and a sufficiently high resolution of the image signal on the other hand to ensure that the captured code can be fully decoded.

[0006] For this purpose, it is known from the state of the art to evaluate the code contained in the image signal using a quality rating. Known solutions for the direct output of quality information are based on standards such as DIN / ISO 15416 for barcodes and DIN / ISO 15415 for data matrix codes. However, a statement about quality can only be made indirectly by evaluating multiple output variables, which is why an operator who is not properly trained often fails to interpret the data or misinterprets it. In practice, this results in system setups being implemented in which the optical image capture units used are not used optimally. This can lead to malfunctions, especially when capturing a large number of different codes, because critical codes are not fully captured.Furthermore, the detection range may be unnecessarily restricted, which means that the potential of the image capture unit is not fully utilized.

[0007] For this reason, the object of the present invention is to overcome the disadvantages known from the prior art. In particular, the object of the present invention is to further develop an image acquisition unit known from the prior art such that even an inexperienced operator can immediately achieve an optimal design. Furthermore, the object of the present invention is to provide a method for determining a size reserve for the minimum resolution limit of a code contained in an image signal, thus enabling an optimal design.

[0008] This object is achieved by an optical image capture unit according to the invention and a method according to the invention according to the independent claims.

[0009] Advantageous developments of the invention are described in the subclaims. The scope of the invention includes all combinations of at least two of the features disclosed in the description, the claims, and / or the figures.

[0010] To avoid repetition, features disclosed by the device should also be considered as disclosed by the method and claimable. Likewise, features disclosed by the method should also be considered as disclosed by the device and claimable.

[0011] The present invention relates to an optical image capture unit for capturing a code, comprising optical capture means configured to generate an image signal containing the code with a hardware-dependent and pixel-based resolution. Furthermore, the image capture unit according to the invention comprises evaluation means configured to determine a dimensional dimension of a smallest code unit in the image signal, as well as indication means configured to determine a size margin for the minimum resolution limit as a ratio between the dimensional dimension of the smallest code unit and a predeterminable limit value.

[0012] The image capture unit according to the invention has the advantage that the calculated size reserve determines a factor that is easy to understand for inexperienced operators, providing information about the code quality in terms of its imaged size and thus the individual system structure. This allows for optimal installation for each individual or customer-specific application during commissioning of the image capture unit. Furthermore, the image capture unit according to the invention can also be easily adapted subsequently to a modified system structure and / or a modified application, and / or its correct function can be verified by visually adapting the code and / or the system structure.

[0013] In addition to the easy readability of the generated quality information, which is virtually impossible to misinterpret and / or misinterpret even by an inexperienced operator, the image acquisition unit according to the invention is also characterized by low computational effort, since the size reserve can be determined by a simple mathematical operation, in particular by multiplying by the limit value stored as the reciprocal. Advantageously, the additional computational operations only insignificantly increase the computational requirements, which is why existing systems can also be converted accordingly and thus continue to be used.

[0014] Within the scope of the present invention, the evaluation means are preferably designed to execute a decoding algorithm. In addition to determining the dimensional value of the smallest code unit, the evaluation means can also be designed to decode the optically detected code. The decoding means first detect the code contained in the image signal, and subsequently, a complete decoding of the individual code units that together form the code can also take place.

[0015] In the present invention, the optical detection means are preferably embodied as a camera comprising a lens and / or a code reader comprising a lens and / or a scanner comprising a lens, which is why the design of the detection means significantly influences the properties of the image signal. The image signal is preferably formed by a two-dimensional, digital image having a fixed resolution that depends on the number of pixels of the sensor detection surface used for digitization. In other words, the pixels form, in particular, a planar sensor detection surface onto which the light rays bundled across the object impinge, which are then integratedly detected by the pixels.

[0016] For the purposes of the present invention, a code is understood to be a 1D code or a 2D code. The 1D code is preferably designed as a barcode and / or barcode, and the 2D code is preferably designed as a matrix code. The matrix code is more preferably an Aztec Code, Data Matrix ECC 200, Micro QR Code, or QR Code. Alternatively, the matrix code can also be implemented according to the Dot Code or PDF417 standard.

[0017] Furthermore, in the present invention, the dimension of the code unit, in particular the dimension of the smallest code unit, is understood to mean a bar width, in particular for 1D codes, and / or a module size, in particular for 2D codes.

[0018] The threshold value is a predefined value stored in the system, particularly in the indicators. This value is influenced by the structure of the code, such as the code type and / or code size, the optical detection means, particularly the resolution and / or optical properties, and the evaluation means, particularly the type and function of a decoding algorithm. The stored threshold value is preferably identical for codes such as Aztec Code, Data Matrix ECC 200, Micro QR Code, and QR Code, although a Dat Code and a PDF417 Code preferably have individual threshold values.

[0019] According to a first possible embodiment of the image capture unit according to the invention, the detectable code is designed as a 1D code, in particular as a barcode, or as a 2D code, in particular as a matrix code. The indication means in this context are designed and / or configured such that a first limit parameter can be selected for the limit value in the 1D code and a second limit parameter can be selected for the 2D code, and can thus be used to determine the size reserve. Preferably, the first limit parameter differs from the second limit parameter; however, the stored limit parameters can also be identical.

[0020] The use of multiple boundary parameters as threshold values ​​allows the system design to be optimized depending on the code to be detected. Depending on the specific application, this allows optimization for a large detection range and / or a reduction in the smallest dimension of the code to be detected.

[0021] As already mentioned, the limit parameter stored as a limit value depends on the type and / or nature of the code. Therefore, it is also intended that several limit parameters for the limit value be stored in the indication means. The indication means then select one of the stored limit parameters, particularly depending on the code type to be detected and / or other properties, and use it to determine the size reserve. The appropriate limit parameter is selected by the indication means based on the detected code and / or, in particular, on the decoding algorithm.

[0022] The operator can influence this selection and, in particular, can store general information on the system structure and / or the code to be captured in the system via an appropriately provided interface, whereby, in particular, a selection of different decoding algorithms, in particular a first and / or a second decoding algorithm, can also be made.

[0023] In a further development, the evaluation means are designed such that, depending on an input signal, in particular a selection made through user interaction, the dimensional measure of the smallest code unit can be determined using a first decoding algorithm in a computation-time-optimized manner and / or using a second decoding algorithm in a resolution-optimized manner. In this context, the indication means are designed such that a limit parameter can be used for the limit value depending on the decoding algorithm used to determine the dimensional measure.

[0024] In other words, this means that the operator has the possibility, in particular, to optimise the image acquisition unit and / or the evaluation means, in particular by a targeted selection of a decoding algorithm, with regard to the required computing time on the one hand or the accuracy in decoding and / or capturing the dimensional measure of the smallest code unit on the other hand.

[0025] In this context, computation time optimized means that a decoding algorithm is used that is characterized by low computational effort and can therefore be executed in a short time and / or using a cost-effective computing unit.

[0026] In this context, resolution-optimized means that a decoding algorithm is chosen that captures the code with a high resolution, although this does not generally result in a reduction in the overall computing time.

[0027] Since a high-resolution image signal has a greater distance to the resolution limit than a low-resolution image signal, the decoding algorithm used is also taken into account by the indicators when selecting the limit parameter.

[0028] A further development of the present invention comprises a configuration unit comprised by the image acquisition unit and / or the indication means, which is designed such that a limit parameter can be stored for the limit value depending on at least one device parameter of the image acquisition unit. The device parameter is preferably selected from at least one element of the following list: lens of the optical acquisition means, resolution and / or pixel size of the optical acquisition means, and illumination level of the optical acquisition means.

[0029] This refinement takes particular account of the properties of the sensor, the illumination, and the lens, which also affect the properties of the code contained in the image signal. Thus, the image capture unit can also be operated with an interchangeable and / or changeable lens. If this parameter changes, particularly if there is a relative speed between the object bearing the code and the image capture unit according to the invention, the stored limit value for determining the size reserve according to the invention can also change, in order to always implement an optimal system configuration and / or to obtain an estimate of the technical resolution limit of the existing system configuration.In this context, the operator would, in particular, store the changed properties of a replaced lens in the system, with the indication means selecting a correspondingly changed limit parameter based on the input and a stored relative speed, in particular of a robot arm comprising the image capture unit and / or a conveyor belt that guides the object with the code.

[0030] In a further development, an embodiment of the image capture means is provided, wherein the optical capture means are designed to capture a rotational position of the surface having the code in relation to a sensor detection area of ​​the capture means. Furthermore, in this context, the indication means are designed such that a reference parameter can be selected for the reference value depending on the rotational position, in particular a relative angle of rotation. This advantageously also allows the capture of codes that, in particular due to the external nature of the object and / or the system structure, lie in a plane rotated about an optical axis OA relative to the optical capture means. However, using corresponding evaluation algorithms generally known from the prior art, regions of such codes can also be captured and / or evaluated in such a way that complete decoding of the code can be achieved.Examples in this context include US Pat. No. 5,979,763 A and the scientific article entitled "Decoding bar codes from human-readable characters" by Kjersti Aas and Line Eikvil of the Norwegian Computing Center, PO Box 114 Blindern, N-0314 Oslo, Norway. However, such evaluation algorithms also affect the evaluation tools used to capture the dimensionality of the smallest code unit, which is why an adapted limit parameter should be used when calculating the size reserve for the limit value.

[0031] A preferred embodiment of the optical image capture unit according to the invention further comprises spacing means which are comprised by the image capture unit and which are designed such that a maximum distance between the optical image capture unit, in particular the sensor detection surface or a sensor housing outer surface aligned with the object, and the object comprising the code, in particular an object surface having the code, can be determined and in particular can be transmitted to an operator.

[0032] During initial commissioning and / or during the operating life of a production facility, an operator can thus directly determine the maximum distance d max between the outer surface of the sensor housing aligned with the object and a detection zone. The detection zone is preferably formed by an object plane, with the code applied to the object being arranged within the object plane.

[0033] In practice, this also contributes synergistically to the uncomplicated handling of the image acquisition unit according to the invention for the untrained operator, since the existing system structure can be evaluated at any time with regard to the resolution limit.

[0034] It should be noted that due to the design of the optical detection means, in particular due to the optical properties of the lens, a further

[0035] Optimization in relation to the calculated size reserve results, since the size reserve according to the invention does not take into account the internal distance d' formed within the lens.

[0036] Within the scope of a further development, it is further preferably provided that the evaluation means are designed such that a limit parameter can be taken into account for the limit value depending on the relative speed between the object that externally encompasses the code and the optical detection means when the code is detected. The influence of a handling device, such as a conveyor belt and / or a robot arm, on the image capture unit can thus be advantageously taken into account in order to capture the code "as the object passes by," i.e., when a relative speed exists between the object and the image capture unit.

[0037] In a further development, it is further provided that the evaluation means are designed to determine at least two dimensional measurements of two smallest code units of at least two codes contained in the image signal. The indication means are designed to determine a first size reserve of the first code and at least one second size reserve of the at least one second code. Furthermore, selection means comprised by the image capture unit or the indication means are provided, which are designed such that the smallest size reserve can be determined and, in particular, transmitted to an operator.

[0038] In other words, in such an embodiment, the image capture unit is designed to simultaneously capture multiple codes in the same image signal or temporally differing image signals. An individual size reserve can be determined for each code, particularly depending on its nature, with different limit values ​​potentially being used in the determination. Furthermore, it is now provided that the smallest size reserve is now determined by the included selection means, with it also being provided in particular that the smallest size reserve is then transmitted to the operator. This advantageously allows an inexperienced operator to optimize the design of the image capture unit for the most critical application.

[0039] In a further development, the optical detection means are designed to detect the code application technique, whereby a limit parameter can be selected for the limit value depending on the nature and / or application technique of the code. It has been shown that properties of the code, such as the print quality of the code and / or the general application technique, also influence the maximum size reserve. The application technique is understood, for example, to be the creation of needle-punched codes on metal bodies. Although such codes are robust against external influences such as UV radiation and / or high temperatures, they are usually difficult to detect optically. For this reason, the presence of such codes can lead to an additional limitation in code detection, which is reflected in a reduced size reserve, which then results from a correspondingly adjusted and selected limit parameter.

[0040] Furthermore, a preferred embodiment of the image acquisition unit according to the invention comprises display and / or output means which are designed such that the size reserve, in particular the smallest size reserve, can be displayed and / or that the display and / or output means comprise means for displaying, in particular in color, a factor and / or a value range.

[0041] Advantageously, the previously calculated size reserve can be output directly to the operator in order to enable easy transmission of the size reserve to the operator by means of various colored LEDs or a display for graphically outputting a range or factor.

[0042] Furthermore, within the scope of the present invention, protection is claimed not only for an optical image capture unit according to the invention, but also for a method for determining a size reserve for the minimum resolution limit of a code, which method is carried out in particular by means of an optical image capture unit according to the invention.

[0043] The method according to the invention comprises the following method steps. In a first method step, an image signal is generated from a code with a hardware-dependent and pixel-based resolution using optical detection means. Furthermore, in a second method step, a dimensional measurement of a smallest code unit in the image signal is detected using evaluation means. Furthermore, a size reserve for representing the resolution limit is determined using indication means, whereby the ratio between the dimensional measurement of the smallest code unit and a predeterminable limit value is determined.

[0044] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the

[0045] Drawings. In the drawings, the same reference symbols are always used for elements with the same function and / or structure.

[0046] They show: Fig. 1: a schematic representation of an optical image capture unit according to the invention in accordance with a first preferred embodiment; Fig. 2a / b: a schematic representation of the optical image capture unit of a second exemplary embodiment; Fig. 3a / b: a schematic representation of a sensor appearance surface with directly adjacent pixels shown as squares; and Fig. 4: a schematic sectional representation of a system structure to schematically depict the operating principle of the spacing means.

[0047] The Fig. 1 shows an optical image capture unit 1 according to the invention according to a first preferred embodiment in a highly schematic representation. The image capture unit 1 is designed to capture a code and initially has optical capture means 2 for generating an image signal. The image signal has a hardware-dependent and pixel-based resolution and contains a code that is applied, in particular, to an object. Functionally, the capture means 2 are in operative contact with evaluation means 3 of the image capture unit 1. The evaluation means 3 are configured to capture a dimensional measure of a smallest code unit of the code contained in the image signal.

[0048] If the code is a barcode, the smallest code unit consists of the smallest bar width of the barcode. In a matrix code, however, the smallest code unit is formed by the smallest module size.

[0049] Furthermore, the image capture unit 1 shown also includes indicator means 4 configured to determine a size margin for the minimum resolution limit of the code, in particular for the smallest code unit, by determining the ratio between the dimensional size of the smallest code unit and a predeterminable limit value. At least one limit parameter for the limit value is stored in the indicator means 4, which was determined in advance based on the properties of the image capture unit 1, the system structure, and the nature of the code.

[0050] Furthermore, the illustrated embodiment of the image acquisition unit 1 comprises display and / or output means 12 configured to graphically display and / or output the size reserve determined by the indication means 4. In this context, an output can be provided by a light source, for example, coded by a flashing sequence of one or more LEDs. Alternatively, the output can also be achieved by several colored LEDs, with a green LED indicating a large size reserve, a yellow LED indicating a small size reserve, and a red LED indicating an insufficient size reserve.

[0051] Furthermore, the display and / or output means 12 can also be designed by means for displaying a factor and / or a value range 13, for example to output a standardized factor by means of a 7-segment display or to use a standardized display for outputting the determined size reserve.

[0052] In addition, the illustrated embodiment of the optical image capture unit 1 according to the invention comprises distance means 8 which are designed to determine a maximum distance. The maximum distance results from the distance between the optical image capture unit 1, in particular a Fig. 1 illustrated sensor detection surface 9 of the optical sensor detection means 2 or a sensor housing outer surface 10 of the optical image detection unit 1 according to the invention, and the object having the code.

[0053] Furthermore, selection means 11 are schematically shown, which are designed such that when detecting several codes in an image signal and determining several different size reserves, only the smallest size reserve, which thus limits the system, can be transmitted to an operator via the display and / or output means 12.

[0054] Finally, the illustrated embodiment of the image capture unit 1 also comprises a configuration unit 7, which is designed such that a limit parameter can be stored for the limit value as a function of at least one device parameter of the image capture unit 1, wherein the properties of the lens 14 of the optical capture means 2 and / or the degree of resolution and / or the pixel size of the optical capture means 2 and / or a degree of illumination of the optical capture means 2, which is present when capturing the code and can thus be captured or specifically generated, are taken into account as device parameters.

[0055] In the Fig. 2a und 2b An optical image capture unit 1 according to the invention is shown according to a second embodiment, wherein the capture of a code 5 occurs. In the present case, the code 5 is designed as a barcode printed on the outside of a rectangular object.

[0056] In the Fig. 2a the detection of the code takes place with a distance d 1 between the sensor housing outer surface 10, which is aligned with the object and is thus defined in particular by the lens, and the object outer surface having the code, which is in relation to the distance d 1 defined in the Fig. 2b The distance d max shown is small. Advantageously, the original system design was based on the Fig. 2a regarding the largest possible detection range in the optimized system structure according to the Fig. 2b transferred, wherein the image acquisition unit 1 according to the invention in the optimized system structure according to the Fig. 2b is operated at the resolution limit. The detection range of the Fig. 2b is therefore larger than in the Fig. 2a , which is why the code contained in the image signal in the system structure is Fig. 2b visually smaller than in the system structure after the Fig. 2a .

[0057] When the optical image capture unit 1 is operated at the resolution limit, the resolution of the smallest code unit in the image signal is just large enough to completely capture the surrounding area of ​​the barcode and to allow the barcode captured therein to be decoded without error. The resolution limit is essentially determined by the dimension of the smallest code unit, which in the present embodiment is the smallest bar width of the black or white bars of the displayed barcode.

[0058] In the system structure after the Fig. 2a A size reserve r of 2 was determined by the indicator means 4 of the image capture unit 1 according to the invention, which is not graphically represented here. For the limit value, the indicator means 4 used a limit parameter of 1.5 pixels, which had been previously defined for the capture of printed barcodes using the present optical image capture unit 1. The evaluation means 3, which are not graphically represented here, were thus able to determine a value of 3 pixels from the image signal as a dimensional measure for the smallest bar width of the code.

[0059] In the system structure after the Fig. 2b has the size reserve r a value of 1. The limit parameter of 1.5 pixels still applies to the threshold. The dimension of the smallest code unit, i.e., the smallest bar width determined in the image signal, was determined by the evaluation tools to be 1.5 pixels.

[0060] The Fig. 3a und 3b each show a highly schematic section of the sensor detection area 9, which is shown in an upper area, and a section of a code 5 formed by a line cut, which is shown in a lower area.

[0061] The Code 5, represented in sections, is a barcode composed of light and dark areas along an X-direction. The width of the areas, i.e., the bar width of the barcode, is symbolically represented in the line section by the numbers "1," "2," and "3." The dimensional unit of the smallest code unit, i.e., the thinnest bar width, is thus "1" and is formed by white and black areas or bars.

[0062] The upper part of the Fig. 3a The sensor detection area 9 shown is formed by a plurality of directly adjacent pixels, which are graphically represented as cuboid-shaped boxes. All pixels are arranged in rows and columns to form the sensor detection area 9. A lens 14 of the detection means 2 (not shown in the figure) projects the code shown in the lower region onto the sensor detection area in a position-dependent manner with respect to the X direction. The incident rays are detected integrally by each pixel over an exposure time and converted into an output signal.

[0063] The first black line in the X direction, located on the far left and with a width of "1," is thus mapped to the pixels in the first column and partially to the pixels in the second column. The first white line, immediately adjacent to the first black line, is partially mapped to the pixels in the second column and completely to the pixels in the third column. Therefore, different relative gray values ​​result for the pixels in the first to third columns over the exposure time, which is symbolically represented by the different markings of the individual pixels. Dark hatching corresponds to a low relative gray value, light hatching corresponds to a medium relative gray value, and no hatching corresponds to a high relative gray value.

[0064] From the image signal, an amount of 1.5 pixels can be determined for the dimension of the smallest code unit.

[0065] The Fig. 3b essentially corresponds to the Fig. 3a , whereby the dimension of the smallest code unit, which in the code snippet shown is again represented by the number "1", can be determined to be 3 pixels, since the first black line is completely mapped by the lens onto the pixels of the first three columns.

[0066] In the Fig. 4 The essential connection of the spacer means 8, i.e. their operating principle, is shown schematically.

[0067] First of all, the Fig. 1 known image capture unit 1 with the sensor detection surface 9 and the optical detection means 2, which comprise the lens 14 with its optical axis OA, is shown. The lens 14 optically images an object plane onto an image plane, wherein a first principal plane H 1 and a second principal plane H 2 run through the lens 14. The first object plane OE 1 is spaced from the first principal plane H 1 along the longitudinal direction L by a first object distance g 1, wherein the first object distance g 1 is composed of an inner distance d' and an outer distance d 1, referred to below as the working distance. The inner distance extends between the first principal plane H 1 and the sensor housing outer surface 10 and thus runs completely within the image capture unit 1. The inner distance d' is therefore not visible to an operator.The working distance d 1 extends in the longitudinal direction L between the sensor housing outer surface 10 and the first object plane OE 1 .

[0068] About the magnification β with β = b g = f g − f , where b the image distance, g the object distance and f the focal length and the size reserve r with r = β 1 β 2 the following ratio for the size reserve r can be determined: r = g 2 − f g 1 − f = d ′ + d max − f d ′ + d 1 − f

[0069] This results in a calculation formula for the maximum distance d max , for which the following relationship applies: d max = d ′ − f r − 1 + rd 1

[0070] The distance means 8 are designed to carry out this calculation formula and include the inner distance specified by the manufacturer d' . The focal length f and the working distance d1 are stored in the distance means 8, which is why the distance means 8 can determine the maximum distance d max after the size reserve r has been determined once by means of the indication means 4.

[0071] With a focal length f of 6mm, a known inner distance d' of 20mm, a working distance set by the operator or automatically recorded d 1 of 50mm and a size reserve of 2 determined by the indication means 4 for the existing system structure, this results in a maximum distance d max of 114mm. Due to the internal distance d', which is unknown to the operator, the maximum distance d max not directly as a multiple of the size reserve, which leads to a further advantageous embodiment of the present optical image capture unit 1.

[0072] As a result, the present invention enables the handling of prior art image capture units to be optimized in a surprisingly simple manner. An inexperienced operator can thus easily obtain a quality assessment of an optically captured code to achieve application-specific optimization. This leads to advantageous cost savings and significantly expands the range of applications and the service life of the image capture unit according to the invention.

Claims

1. Optical image capture unit (1) for capturing a code (5), comprising optical capture means (2) which are designed such that an image signal that depicts the code (5) and has a hardware-dependent and pixel-based resolution can be generated, characterized by evaluation means (3) which are designed such that a dimension measurement of a smallest code unit in the image signal can be determined and indication means (4) which are designed such that a size reserve for the minimum resolution limit can be ascertained as a ratio between the dimension measurement of the smallest code unit and a predefinable limit value.

2. Optical image capture unit according to claim 1, characterized in that the detectable code is designed as a 1D code, in particular as a linear code and / or barcode, or as a 2D code, in particular as a matrix code, the indication means (4) being designed such that, for the limit value, a first limit parameter can be selected in the case of the 1D code and a second limit parameter can be selected in the case of the 2D code, the first limit parameter preferably differing from the second limit parameter.

3. Optical image capture unit according to claim 1 or claim 2, characterized in that the evaluation means (3) are designed such that, depending on an input signal, in particular on a selection made by a user interaction, the dimension measurement of the smallest code unit can be ascertained in a computing time-optimized manner by means of a first decoding algorithm and / or in a resolution-optimized manner by means of a second decoding algorithm, the indication means (4) being designed such that, for the limit value, a limit parameter can be stored depending on the decoding algorithm carried out to ascertain the dimension measurement.

4. Optical image capture unit according to any of the preceding claims, characterized by a configuration unit (7) comprised by the image capture unit (1) and / or by the indication means (4), which configuration unit is designed such that, for the limit value, a limit parameter can be stored depending on at least one device parameter of the image capture unit, the device parameter being selected from at least one element of the following list: lens (14) of the optical capture means (2), resolution and / or pixel size of the optical capture means (2), degree of illumination of the optical capture means (2).

5. Optical image capture unit according to any of the preceding claims, characterized in that the optical capture means (2) are designed to capture a rotational position of the surface which has the code in relation to a sensor capture surface (9) of the capture means (2), the indication means (4) being designed such that, for the limit value, a limit parameter can be selected depending on the rotational position, in particular on a relative rotation angle.

6. Optical image capture unit according to any of the preceding claims, characterized by spacing means (8) comprised by the image capture unit (1), which spacing means are designed such that a maximum distance between the optical image capture unit (1), in particular the sensor capture surface (9), which is aligned with the object, or a sensor housing outer surface (10), and the object which comprises the code (5), in particular an object surface which bears the code, can be ascertained and in particular transmitted to an operator.

7. Optical image capture unit according to any of the preceding claims, characterized in that the evaluation means (3) are designed such that, for the limit value, a limit parameter can be taken into account depending on a relative speed, when capturing the code, between the object which has the code (5) and the optical capture means (2).

8. Optical image capture unit according to any of the preceding claims, characterized in that the evaluation means (3) are designed to determine at least two dimension measurements of the two smallest code units of at least two codes (5) contained in the image signal, in that the indication means (4) are designed to ascertain a first size reserve of the first code (5) and at least one second size reserve of the at least one second code (5), and selection means (11) comprised by the image capture unit (1) and / or by the indication means (4), which selection means are designed such that the smallest size reserve can be determined and in particular transmitted to an operator.

9. Optical image capture unit according to any of the preceding claims, characterized in that the optical capture means (2) are designed to capture the application technique of the code (5), it being possible to select, for the limit value, a limit parameter depending on the application technique.

10. Optical image capture unit according to any of the preceding claims, characterized in that the optical image capture unit (1) comprises display and / or output means (12) which are designed such that the size reserve, in particular the smallest size reserve, can be displayed and / or that the display and / or output means (12) comprise means for displaying, in particular in color, a factor and / or a value range (13).

11. Method for ascertaining a size reserve for the minimum resolution limit of a code, in particular by means of an optical image capture unit (1) designed according to any of claims 1 to 10, the method comprising the following steps: - generating an image signal from a code which has a hardware-dependent and pixel-based resolution by means of optical capture means (2); - capturing a dimension measurement of a smallest code unit in the image signal by means of evaluation means (3); - ascertaining a size reserve for displaying the resolution limit by means of indication means (4), wherein the ratio between the dimension measurement of the smallest code unit (5) and a predefinable limit value is ascertained.