Patent Application
20090109534
The present invention relates generally to devices and systems for improving the efficiency and accuracy of aiming patterns for imagers.
Imagers are commonly used data capture mechanisms for computing devices. To properly use an imager, a user must accurately aim the imager at its target. To assist the user in doing so, imagers typically include an element for generating an aiming pattern showing precisely where the imager is pointed.
Such aiming patterns may be generated using light generated by a laser diode, coupled with a diffractive optical element (“DOE”) to generate an aiming pattern. Ideally, an aiming pattern should accurately represent the imaging field of view and be visible both indoors and outdoors.
A device having a diffractive optical element portion diffracting an incident light beam to create a first portion of a target pattern and a refractive optical element portion refracting the incident light beam to create a second portion of the target pattern.
A system having a light source generating a light beam, a collimating lens collimating the light beam into a collimated light beam and a pattern generating element comprising a diffractive optical element portion and a refractive optical element portion, the pattern generating element creating a target pattern from the collimated light beam incident on the pattern generating element.
The exemplary embodiments of the present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The exemplary embodiments of the present invention describe devices and systems for generating aiming patterns for imaging devices. In the exemplary embodiments, a light source (e.g., a laser diode) emits a beam which shines through a collimating lens and subsequently through a DOE to achieve a desired aiming pattern. Various DOE configurations are disclosed in order to achieve a variety of aiming patterns.
Existing systems for generating aiming patterns typically use a collimating lens with a small input numerical aperture to cut the size of the central circular zone from the radiation of the laser diode. The use of this type of collimating lens results in significant power losses in the aperture of the collimating lens, and thus decreases the brightness of the aiming pattern and limits the total length of the aiming lines. Subsequently, the collimated light passes through a diffractive optical element to generate an aiming pattern. In order to achieve both indoor and outdoor visibility, it is desirable to have an aiming pattern having several lines and dots; when the pattern is generated using DOE, the lines themselves also consist of series of dots. Depending on the complexity of the aiming pattern, the DOE may generate a number of secondary, undesirable aiming dots that make the use of the aiming pattern less intuitive.
In order to maintain the aiming pattern without requiring protective eyewear in conformance with laser safety standards, it is necessary to provide highly accurate laser power distribution among the different parts of the aiming pattern. For some aiming patterns, such as those having one bright central aiming dot for outdoor visibility and a number of aiming lines, it is difficult to maintain an accurate ratio of power distribution between the central dot and the other lines.
The exemplary embodiments of the present invention use a high numerical aperture laser collimating lens in combination with a multi-segmented DOE to provide a number of improvements over prior existing systems.
The use of this type of lens provides a number of advantages over prior systems that use small numerical aperture collimating lenses. A high numerical aperture collimating lens may increase the brightness of the aiming pattern generated by the system 100. Further, it may help to reduce secondary, unwanted pattern dots. Additionally, the high numerical aperture collimating lens may help to sharpen the aiming lines and dots that are created. Finally, it may provide better control of the laser power distribution among different features of the aiming pattern.
The collimating lens 130 may emit a focused, collimated light beam 140. The light beam 140 may then become incident upon a multi-segmented pattern forming element 150, which will be described in further detail below. The pattern forming element may be, for example, the pattern forming element 350 of
Those skilled in the art will understand that, if the refractive area 370 is a hole or similar slit in the pattern forming element 350, there is no refractive index and the laser light may travel directly through the refractive area 370 to form the portion of the target pattern generated by the refractive area 370. In other exemplary embodiments, the refractive area 370 may be formed of a material having a defined refractive index. In such exemplary embodiments, the laser light will be refracted at an angle related to the refractive index of the material. Thus, the portion of the target that is generated by the refractive area 370 may be offset from the actual refractive area 370. In such an exemplary embodiment, the refractive area 370 may not be located in a central area of the pattern forming element, but may be located away from the center to account for the refractive index of the refractive area 370 and/or for the desired location of the portion of the target pattern generated by the refractive area 370.
The size of the refractive area 370 may be selected to allocate an appropriate amount of energy to the central dot 261. As an example, the incident laser spot 360 may provide 10 mW of power and 1 mW of power may be desired in central dot 261. If a uniform power distribution over the laser spot 360 is assumed, then the refractive area 370 would ideally be 1/10 the size of the laser spot 360. More realistically, the laser may typically have a Gaussian distribution of power. Because this is the case, those of skill in the art will understand that the power in the laser beam may be concentrated towards the center of the laser spot 360, and that the refractive area 370 may typically be sized smaller than 1/10 the size of the laser spot 360 for the above referenced power distribution.
The remainder of the pattern forming element 350 may comprise a diffractive optical element 380 for generating an aiming pattern, as discussed above. The portion of the laser spot 360 that is incident on the diffractive optical element 380 is diffracted, such as through constructive and destructive interference, to form the remainder of the aiming pattern, such as the lines 262, 263, 264, 265 of the pattern 160 shown in
Those of skill in the art will understand that the length of the lines 262, 263, 264, 265 may be proportional to the diffraction angle produced by the diffractive optical element, linearly scaled by the distance to the target 170. The diffraction angle, in turn, may be proportional to the wavelength of the light provided by the light source 110 and inversely proportional to the feature size, or spatial resolution, of the diffractive optical element 350.
The exemplary system shown in
Though
Referring to the aiming pattern 160 of
The horizontal lines 263 and 265 may be created by the zone 985 of the DOE 280 between the two refractive areas 970. The vertical lines 262 and 264 may be created by the zones 987 of the DOE 980 that lie outside the respective refractive areas 970. Accordingly, it may be seen how the exemplary pattern forming element 950 having multiple refractive areas 970 and multiple zones 985 and 987 of the DOE 980 may create an exemplary aiming pattern.
The quality (sharpness and cleanness) of the aiming pattern may be achieved by simplifying surface geometry because each zone forms less components of the aiming pattern. Further, the geometry of the zones is preferably chosen to minimize variation of laser power in different aiming pattern components. Thus, in the exemplary pattern forming element 950, each zone contributes to only one component of the aiming pattern, e.g., the refractive areas 970 in the form of two slit-shaped clear flat zones form the central aiming dot 261, the zone 985 of the DOE 980 forms the horizontal aiming lines 263 and 265, and the two outer zones 987 form the vertical aiming lines 262 and 264.
It should also be noted that, each of the zones may be implemented using diffraction or refraction technology. That is, it is possible to create the lines and/or the center dot of the aiming pattern using refractive area(s) and/or diffractive area(s).
Those of skill in the art will understand that the exemplary embodiments of the present invention improve the efficiency of light utilization by using a high numerical aperture collimating lens in conjunction with a pattern forming element with a central refractive area to allow passage of a large portion of incident light. Further, the exemplary embodiments may reduce secondary pattern dots and provide improved quality and sharpness among the aiming lines and dots that are created. In addition, those skilled in the art will understand that there are numerous other types of arrangements of refractive and diffractive elements that may be used based on the desired target pattern.
It will be apparent to those skilled in the art that various modifications may be made in the present invention, without departing from the spirit or the scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
