The invention relates to a scanner, in particular for the detection of one-dimensional and/or two-dimensional codes, having a light receiver arranged in a housing and an optical receiving system associated therewith and also accommodated in the housing.
Such scanners known from the state of the art, can be formed, for example as line scanners in order to be able to read barcodes in this way without a relative movement having to be made between the scanner and the code. Such scanners can, however, also be utilized for the reading of two-dimensional codes provided that a relative movement is generated between the scanner and the code by means, for example, of a conveying motion. Alternatively, it is moreover also possible to use area scanners known from the state of the art instead of a line scanner, with said area scanners being able to read two-dimensional codes without a relative movement between the scanner and the code.
Known scanners based on the functional principle described above have the disadvantage that codes are frequently only recognized incompletely or incorrectly or, in extreme cases, not at all as a result of inadequate or changing light conditions.
An object of the present invention comprises the further development of a scanner of the initially named kind such that reading errors caused by inadequate or changing light conditions can be at least largely excluded and in particular fully excluded.
This object is satisfied in accordance with the invention by at least one light source being additionally provided in the housing to illuminate the region to be scanned arranged in an object plane.
Since the scanner has its own light source in accordance with the invention which provides an optimum illumination of the region to be scanned or of the code to be read, the influence of the ambient light conditions is at least largely eliminated, which means that the codes can also be read reliably and correctly in a dark environment or in an environment with changing light conditions.
It is preferred for the light source to be designed to transmit a constant light intensity so that a continuous illumination is ensured which is constant during the reading procedure.
It is furthermore of advantage if the light source is formed by at least one laser diode since such a point light source allows a good beam formation.
It is preferred for an optical transmitting system to be associated with the light source, with said transmitting optical system transforming a substantially homocentric light bundle transmitted by the light source into a substantially linear light beam focussed on the object plane. When the scanner in accordance with the invention is used as a linear scanner, this measure ensures that at least a large part of the light energy transmitted from the light source is concentrated on the respective line to be read by the scanner, so that the line to be scanned is ideally illuminated. The optical transmitting system preferably consists of refractive, diffractive and/or holographic elements.
The intensity of the linear light beam can have a Gaussian distribution along the illuminated line. In this case, when a plurality of light sources are provided, skillful overlapping of the lines which are aligned to one another can be used to ensure that a relatively large line region is constantly illuminated.
To allow different distances to be set between the scanner and the object plane, i.e. different reading distances and/or different code sizes, the light source and/or the optical receiving system can be movably held in the housing and be adjustable to different positions, with it being particularly advantageous for the movements of the light source and the optical receiving system to be mechanically correlated with one another so that the user must, for example, only actuate one adjusting screw in order to move the light source and optical receiving system simultaneously and in a manner matched to each another such that, on the one hand, the optical receiving system is focused on the scanning plane and, on the other hand, an optimum illumination of the region to be scanned in the scanning plane is ensured.
In order to realize the said adjustment possibilities, the reception optics can be displaceable along its optical axis. Furthermore, the light source can be pivotably formed in a first plane which extends at least substantially parallel to the optical axes of the transmission and optical receiving system. It is possible due to these two adjustment possibilities to adapt the scanner in accordance with the invention to different reading distances and different code sizes.
It is moreover, also possible to mature the light source pivotable in a second plane substantially perpendicular to the said first plane, with this second plane including the optical axis of the optical transmitting system. This adjustment makes it possible to achieve a situation in which, for example, when a linear light beam is transmitted, this light beam can be adjusted, in the scanning plane, perpendicular to the line of light generated in the scanning plane, and can in particular be aligned with a further line of light.
It is particularly preferred if two units positioned with their optical axes at an angle to one another and consisting of one light source each and one optical transmitting system each are provided in the housing of the scanner in accordance with the invention. An even better illumination of the region to be scanned can be achieved by the provision of two or more light sources.
An embodiment of the invention having two light sources, which each generate a linear light beam, is explained in more detail below with reference to the description of the figures.
The light receiver can be formed as a spatial resolution detector, in particular as a CCD array, CCD area, CMOS array or CMOS area.