Patent Description:
Additionally, laser based systems can be easily commissioned, as a reading area of a laser scanner can be clearly marked by the laser line. This can allow users to quickly determine proper alignments of the laser scanner and peripheral devices. Further, laser scanning devices can have large viewing angles, (e.g. <NUM>-<NUM> degrees). The large viewing angle allows for laser scanners to be mounted very close to the object to be scanned, or the scanning area (i.e. a conveyor belt) while still maintaining sufficient reading area to be able to read a code.

However, laser based devices are subject to multiple regulations, and are generally regulated to limit the amount of energy that the laser can output. This regulation of the laser output power can limit the distances and fields of view ("FOV") over which the laser based scanning devices and systems can be used. Additionally, many laser based scanning devices utilize rotating or vibrating mirrors to generate a moving spot. These moving parts can subject laser based scanning systems to additional wear and tear, and thereby decrease both reliability and lifespan of the device.

Previously, vision or camera based systems have been used in an attempt to provide an alternate to using laser scanning devices. However, previous vision or camera based systems did not have sufficient scan rates to be able to scan many codes, particularly in applications where the codes are required to be scanned quickly. For example, in an application where the object is moving at approximately <NUM>/s, a laser scanner can scan the code at <NUM> lines per second. Thus, the code would move only <NUM> between scans. However, a typical vision or camera based system may have a scanning rate of only <NUM> frames per second, allowing for approximately <NUM> of movement between frames. This can result in missed codes or partially imaged codes, or possibly no capture at all of the code in any of the frames.

Further prior art may be found in <CIT>, <CIT> and <CIT>.

Further, in camera or vision based scanning systems, the opening angle of the field of view is determined by the focal length of the imaging lens and the sensor size. Generally, these systems have an opening angle of about <NUM> degrees to about <NUM> degrees. These opening angles are generally smaller than for laser based scanning systems. Therefore, for a camera or vision based scanning system to cover the same field of view as a laser based scanning system, the camera or vision based scanning system must be placed farther from the object to be imaged than a laser based scanning system. Thus, a solution for increasing a scanning rate of a vision system is needed.

An optical imaging device according to the features of claim <NUM> is disclosed. Furthermore, a method for reading optical codes using an optical device having the features of claim <NUM> is disclosed.

In some embodiments, only the predetermined lines of pixels are used to image an object. The sensor may have <NUM> lines of <NUM> pixels, and the predetermined used number of lines of pixels may be <NUM>.

In some embodiments, the plurality of illumination devices are light emitting diodes. These illumination devices may be configured on a plane that also contains the optical axis. The plurality of reflective surfaces can be mirrors. Some embodiments comprise reflective surfaces that are configured to fold an illumination axis along the same axis as the optical axis. In some embodiments, folding the optical axis reduces a minimum focused distance to a closest reading plane. Additionally, folding the optical axis may reduce a required mounting space between the device and a closest reading plane. Optionally, an illumination pattern produced by the illumination devices is conjugated with the sensor predetermined used number of lines of pixels.

The optical imaging device comprises an exit window, wherein the illumination path and the imaging path may exit the optical imaging device through the exit window. The exit window may additionally include a filter in at least one of the imaging path and illumination path to filter a determined band of the light wavelength spectra. In some embodiments, the exit window comprises multiple filters and the filters in the imaging path and in the illumination path are polarized with crossed directions of polarization.

The image device comprises an area sensor, a lens, an exit window, and at least one reflective surface. The area sensor includes a first plurality of lines of pixels. The area sensor is configured to sense with only a second plurality of lines of pixels that are arranged in a predetermined position of the area sensor and that include fewer lines of pixels than the number of lines of pixels in the first plurality of lines of pixels. The lens has an optical axis forming a portion of an optical imaging axis of the optical imaging device. The exit window is angled to the optical imaging axis. The exit window may include a filter to filter a determined band of light wavelength spectra. The tilted exit window may be tilted at approximately <NUM> to <NUM> degrees with respect to the optical imaging axis.

The reflective surface is disposed along the optical imaging axis between the lens and the exit window, the reflective surface configured to fold the imaging axis. A distance along the imaging path between the reflective surface and the exit window may be at least <NUM> millimeters (mm) distance. Alternatively, a distance along the imaging path between the reflective surface and the exit window may be at least <NUM>. More particularly, the distance may be in a range of about <NUM> to about <NUM>, in a range of about <NUM> to about <NUM>, or in a range of about <NUM> to about <NUM>. The reflective surface is tilted at an angle of at least about <NUM> degrees with respect to the optical axis of the lens. The exit window may be tilted at an angle in a range of <NUM> to <NUM> degrees of parallel to the reflective surface, and tilted at an angle of at least <NUM> degrees with respect to a plane perpendicular to the imaging plane. In some embodiments, a portion of a field of view (FOV) of the area sensor may be cropped by mechanical components of the optical imaging device.

In some embodiments, the device further comprises an enclosure mechanically coupled to the reflective surface and including a through hole defining the exit window. The reflective surface may be disposed off-center with respect to the optical imaging axis. A field of view (FOV) of the area sensor may be divided by the reflective surface, causing only a first portion of the FOV to be folded by the reflective surface, such that a second portion of the FOV of the area sensor falls within an interior the enclosure.

In some embodiments, the second plurality of lines of pixels may correspond to the first portion of the FOV that is folded by the reflective surface. Additionally, the reflective surface may divide the FOV of the area sensor asymmetrically. The second plurality of lines of pixels may corresponds to about <NUM>% of the first plurality of lines of pixels. The sensor may have <NUM> lines of <NUM> pixels, and the predetermined used number of lines of pixels is <NUM>. Alternatively, the predetermined used number of lines of pixels is <NUM>.

In some embodiments, the image device further comprises a plurality of illumination devices. The illumination devices may be configured to transmit an illumination pattern, wherein the plurality of illumination devices are configured on a plane that contains the optical axis.

Methods for reading optical codes using an optical device are also disclosed. The method comprises focusing an imaging path along an optical axis using a lens, generating an illumination pattern, folding the imaging path using a plurality of reflective surfaces, and sensing an object in the imaging path using an area sensor. The lens is integrated into the optical device, and the illumination pattern has an illumination path along an axis approximately the same as an axis of the imaging path. The sensor uses only a predetermined number of lines of pixels available to the sensor.

The method may optionally further comprise folding the illumination pattern using the plurality of reflective surfaces. The method may also further comprise reducing reflections from the optical codes using a filter, which may be an ultraviolet filter. The optical device may further include an optical filter in at least one of the imaging path and the illumination path for filtering out a determined band of the light wavelength spectra. The illumination pattern may be generated using a plurality of illumination devices, and the plurality of illumination devices may be integrated into the optical device.

The method comprises focusing an imaging path along an optical imaging axis using a lens having an optical axis; folding the imaging path using a reflective surface that is configured to fold the imaging axis; receiving light via an exit window that is angled to the optical imaging axis; and sensing light from an object in the imaging path using an area sensor. The light from the object is received at the area sensor via the exit window, the reflective surface, and the lens. The area sensor is configured to sense with only a second plurality of lines of pixels including fewer lines of pixels than the number of lines of pixels in the first plurality of lines of pixels.

In some embodiments, the method further comprises generating an illumination pattern having an illumination path along an illumination axis approximately the same as the optical imaging axis of an imaging path.

Folding attachment devices for an existing optical imaging device are also disclosed. In some embodiments, the folding attachment device comprises a folded optical path portion and a line-shaped illumination pattern generator. The folded optical path portion is configured to fold an optical path of the optical imaging device, and the line-shaped illumination pattern generator correlates to a windowed portion of a sensor of the optical imaging device. The line-shaped illumination pattern generator may optionally include at least one of a beam splitter and a dichroic mirror. The device may further comprise a tilted exit window to reduce reflections into the accessory device, and may be tilted at approximately <NUM> to <NUM> degrees.

In some embodiments, the folding attachment device comprises a folded optical path portion, and an exit window angled to the optical imaging path. The folded optical path portion may include a reflective surface configured to fold an optical imaging path of an existing optical imaging device. The reflective surface may be configured to fold the optical path between a lens of the existing optical imaging device and the exit window.

In some embodiments, a distance along the imaging path between the reflective surface and the exit window of the folding attachment device may be at least <NUM> millimeters (mm) distance. Alternatively, the distance along the imaging path between the reflective surface and the exit window may be at least <NUM>. More particularly, the distance may be in a range of about <NUM> to about <NUM>, in a range of about <NUM> to about <NUM>, or in a range of about <NUM> to about <NUM>. The reflective surface of the optical imaging device is tilted at an angle of at least about <NUM> degrees with respect to the optical axis of the lens. The exit window may be tilted at an angle in a range of <NUM> to <NUM> degrees of parallel to the reflective surface, and tilted at an angle of at least <NUM> degrees with respect to a plane perpendicular to the imaging plane of the existing optical imaging device. In some embodiments, a portion of a field of view (FOV) of an area sensor of the existing optical imaging device may be cropped by mechanical components of the folding attachment device.

In some embodiments, the folding attachment device further comprises an enclosure and an adaptor plate mechanically coupled to the enclosure. The adaptor plate may be configured to mount the folding attachment device to the existing optical imaging device. The enclosure may be mechanically coupled to the reflective surface and may include a through hole defining the exit window. The reflective surface may be disposed off-center with respect to the optical imaging axis, and an FOV of the area sensor may be divided by the reflective surface, causing only a first portion of the FOV to be folded by the reflective surface, such that a second portion of the FOV of the area sensor falls within an interior the enclosure. The second portion may correspond to about <NUM>% of the FOV.

Additionally, the use of the term "code" can be understood to mean various readable codes such as one dimensional "bar codes," two-dimensional codes (e.g. QD codes, etc.), and other various code types. The use of the term code is not limiting to the type of code applied.

The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention.

The use of imaging devices and systems to read codes, or even to perform basic imaging tasks, requires that the imaging device, or reader have a minimum distance from the object to be imaged to ensure proper field of view and focus can be achieved. In some applications, the available distance between a reader and the object to be imaged can, at times, be very limited. In some examples, the focal length of a lens used in an optical reader can be modified to reduce a minimum closest focused plane distance. However, reduction of the minimum closest focused plane distance by reducing a focal length can increase the field of view angle, causing a farthest imaging plane to increase in size. This increase in the size of a farthest imaging plane can reduce the resolution in the farthest imaging plane, thereby making it more difficult to analyze smaller objects. An example of adjusting a focal length to reduce the minimum focal distance can be seen in the discussion of <FIG>, below.

<FIG> illustrates a general optical reader <NUM> (not according to the invention) having a field of view ("FOV") <NUM>. The reader <NUM> can be configured to read data between a first plane <NUM> and a second plane <NUM>. The first plane <NUM> and the second plane <NUM> can be separated by a first distance <NUM>. In one example, the distance can be <NUM>. However, the first distance <NUM> can be more than <NUM> or less than <NUM>. Additionally the first plane <NUM> and the second plane <NUM> can have defined widths. In one example, the first plane <NUM> can have a width of <NUM>, and the second plane <NUM> can have a width of <NUM>. The FOV <NUM> of the reader <NUM> can therefore be defined once the size of the sensor and the focal length of a lens within the reader are determined. In the example of <FIG>, assuming a one-third inch sensor, and a <NUM> focal length lens, the FOV <NUM> can be ± <NUM> degrees, where the first plane <NUM> and the second plane <NUM> are arranged as discussed above. This results in a distance <NUM> between the first plane <NUM> and the reader <NUM> being approximately <NUM>. The distance <NUM> being <NUM> can be inappropriate for some applications, particularly where space is limited. The FOV <NUM> can generally be determined by the equation <MAT>, where α is equal to the FOV angle <NUM>, f' is equal to the focal length of a lens, and s is equal to and imaging sensor size. Alternatively, the FOV can be determine by the equation of <MAT>, where y is equal to half the length of the second plane <NUM>, (shown as distance <NUM>), and d is equal to the distance from the reader <NUM> to the farthest plane <NUM> (shown as distance <NUM>).

To reduce the minimum focal distance to the first plane <NUM>, the focal length of the lens of the reader <NUM> can be decreased. Turning now to <FIG>, an example imaging system <NUM> (not according to the invention) can be seen with a reader <NUM> having a lens with a focal length of <NUM>. The system <NUM> can further have a first plane <NUM> and a second plane <NUM> separated by a distance <NUM>. For purposes of comparison, in this example the first plane <NUM> and the second plane <NUM> are separated by approximately <NUM>. By reducing the focal length of the lens to <NUM>, from the <NUM> focal length used in the system in <FIG>, the minimum distance <NUM> to the first plane <NUM> can be reduced to <NUM>, assuming the same one-third inch sensor is used. Further, this changes the angle of a FOV <NUM> of the imaging path to approximately <NUM> degrees. Furthermore, the width of the second plane <NUM>, assuming the first plane <NUM> has a width of <NUM>, increases to <NUM>.

While the above examples provide a possible solution for reducing a minimum distance to the object to be imaged by the imaging system by reducing the focal length of the lens, in some examples it may not be possible to reduce the minimum distance to the object to be imaged enough for a given application. One solution to further reduce the space required between an imaging devxice and an object to be imaged is to fold the optical path. In one example, mirrors can be used to fold the optical path. However, other reflective surfaces can be used to fold the optical path, such as prisms where internal reflection is produced.

Turning now to <FIG>, an optical imaging system <NUM> can be seen. The optical imaging system <NUM> can have an imaging device <NUM>. The imaging device <NUM> can include a sensor <NUM>, one or more illumination devices <NUM> and an imaging lens <NUM>. The optical imaging system further includes a reflective surface <NUM>, which can be contained in an enclosure <NUM>, as shown in <FIG>. In one embodiment the sensor <NUM> can be a CMOS-type sensor. Alternatively, the sensor <NUM> can be a CCD type sensor, or other type of applicable sensor. In one embodiment, the sensor <NUM> can be an AR0134 sensor from Aptina. Imaging sensors can generally limit the scan speed of an object due to the limited frame rate available in many digital imaging sensors. To increase the frame rate of a digital imaging sensor, the effective sensing area of the sensor <NUM> can be reduced. For example, as shown in <FIG>, a graphical representation of a sensing area <NUM> of a sensor can be seen. The sensing area <NUM> can contain multiple pixels. The number of pixels in a given sensing area <NUM> determines the resolution of a given sensor. In some embodiments, sensors can have millions of pixels (megapixels). For example, common sensor sizes can be <NUM> megapixels, <NUM> megapixels, <NUM> megapixels, etc. The higher the number of pixels in the sensing area <NUM>, the greater the resolution of the sensor. While greater pixel counts increase the resolution of a sensor, the increase in resolution can have an adverse effect on scanning speed due to the required processing power associated with the increased number of pixels.

To increase a scanning speed of a sensor without reducing the desired resolution, the sensing area <NUM> is reduced such that only a portion of the sensing face <NUM> remains active. <FIG> shows a first inactive area <NUM> and a second inactive area <NUM> surrounding an active pixel area <NUM>. In one embodiment, the active pixel area <NUM> can be sized to the expected FOV required to view a particular code. For example, where a one dimensional bar code is expected to be scanned in a particular orientation (i.e. vertical or horizontal), the active pixel area <NUM> can be oriented similarly (vertically or horizontally). Further, as only a portion of the width of the given code is required for a one dimensional code, the active area <NUM> can be reduced to a few lines of pixels. For example, the active sensing area <NUM> can be reduced to between <NUM> lines and <NUM> lines. However, more or fewer lines of pixels can also be used, as necessary for a given application. In one example, for a sensor having a resolution of <NUM> lines <NUM> pixels, and a frame rate of <NUM> frames per second, by using only <NUM> lines of <NUM> pixels, the active sensing area <NUM> can be reduced by a factor of <NUM> and the frame rate can be increased by a corresponding factor of <NUM>. This increase in frame rate can allow for increased scanning speed and throughput when using an optical imaging system. Additionally, the active sensing area <NUM> can be reduced to a number of lines between <NUM> and <NUM>. While the active sensing area <NUM> could be reduced to less than <NUM> lines, maintaining at least <NUM> lines can reduce the effect of dead pixels in the sensor. Further, maintaining at least <NUM> lines in the active sensing area <NUM> can improve accuracy of an imaging device by providing increased information in comparison to a line sensor.

Turning now to <FIG>, the sensing face <NUM> of <FIG> is shown imaging a one dimensional bar code <NUM> as it passes through the sensing face <NUM> in the direction shown. The orientation of the imaged code is such that the active sensing area <NUM> is able to image all of the data in the bar code <NUM>, even though only a portion of the sensing face <NUM> is active. In one embodiment, the active sensing area <NUM> can be oriented horizontally (to coincide with the largest dimension of the sensor) to allow for a larger FOV and a better resolution, and can also be aligned with the movement direction of the code.

Returning now to <FIG>, the optical reader <NUM> can include one or more illumination devices <NUM>. In one embodiment, the illumination devices <NUM> can be light emitting diodes ("LED"). In some examples, the illuminations devices <NUM> can be a single color LED. Alternatively, multiple colored LEDs can be used to allow for different wavelengths to be presented to the object depending on the type of code to be imaged. In some embodiments, the illumination devices <NUM> can output light at a constant output. Alternatively, the optical reader <NUM> can vary the output of the illumination devices <NUM>. For example, in some applications, the code to be read may be on a highly reflective object, where high intensity light can obscure or "wash-out" the code. Thus, the output of the illumination devices <NUM> can be reduced to ensure proper illumination of the object. Additionally, the illumination devices may comprise illumination optics, which are discussed in more detail with reference to <FIG>.

Furthermore, filters located in an exit window <NUM> of the imaging device <NUM> can be used to filter out ambient light, as shown in <FIG>. Additionally, filters may be designed to filter out a determined band of the light wavelength spectra, and can filter the imaging path, illumination path, or both. In one example, the illumination devices <NUM> can output light in the ultraviolet spectrum. Further, in some examples, the codes on the objects can be printed using a fluorescent ink, wherein the emission wavelength is different from the excitation wavelength, the use of a filter on the imaging path can allow only the fluorescence emission wavelength provided by the fluorescent ink to pass through; thereby allowing only the object of interest (the code) to be imaged.

Additionally, cross-polarized light can be used to avoid reflections on the objects to be imaged. This feature is advantageous where the code to be imaged is on a shiny or reflective surface, such as a polished metal object. To polarize the light, a polarizer can be placed in front of the illumination devices <NUM>, and a polarizer with the polarizing direction perpendicular to the illumination polarizer can be placed in the imaging path. In one embodiment, the polarizer can be integrated into the exit window <NUM>. Alternatively, the polarizer can be incorporated into the illumination devices <NUM> and into the imaging lens. Further, the polarizer can be placed directly in front of the illumination devices <NUM> and in front of the imaging lens. In some embodiments the polarization direction of the imaging path can be parallel to the illumination polarizer; alternatively, the polarization direction can be perpendicular to the illumination polarizer. Generally, the orientation of the polarizer is selected based on the application.

The one or more illumination devices <NUM> can further be oriented such that the light is transmitted along approximately the same axis as an optical imaging axis <NUM>. In some embodiments, the illumination devices <NUM> are configured on a plane that contains the optical imaging axis <NUM>. In one embodiment, the illumination devices <NUM> can transmit light along a similar but separate axis from that of the optical imaging axis <NUM>. However, as both the optical imaging axis <NUM> and the illumination axis are approximately the same due to the use of the reflective surface <NUM>, both axis can be close enough such that the illumination devices <NUM> provide illumination in the field of view of the optical reader <NUM>.

In one embodiment, one or more illumination devices <NUM> can be used. Further, to help match an illumination pattern geometry to an imaging path or to coincide with a sensing area, such as active sensing area <NUM> discussed above. One example of positioning the illumination devices can be seen in <FIG> illustrates a plurality of illumination devices <NUM> and an imaging lens <NUM> positioned in an illumination optic <NUM>. As shown in <FIG> the illumination devices <NUM> can be arranged linearly. Further, the illumination devices <NUM> can be equally distributed on either side of the imaging lens <NUM>. Alternatively, the illumination devices <NUM> can be distributed unevenly, or in a non-linear pattern, as applicable. The illumination device <NUM>, as arranged in <FIG>, can project an illumination pattern similar to the active sensing area <NUM> of <FIG>.

The illumination optic <NUM> can be produced in a number of ways. In some embodiments, the illumination devices <NUM> are placed within an injection molded part, e.g., the illumination optic <NUM>, and can take on any desired shape, such as those shown in <FIG> for non-limiting examples of the illumination optics. In some embodiments, an aperture can be included for the imaging path. In some embodiments, the illumination optics are formed in a single injection molded part, like that shown in <FIG>. In other embodiments, illumination optics may be grouped together, such that a plurality, but not all of the illumination optics are positioned in a group of injection molded parts, as shown in <FIG>. In yet other embodiments, the illumination optics are positioned individually. It has been further contemplated that other polymer forming processes can be used, such as thermoforming, compression molding, blow molding, and others known in the art.

In some embodiments it is desirable to have the illumination devices <NUM> provide illumination along the same axis as the optical imaging axis. For example, when the imaging device is in close proximity to the object to be imaged, it can be advantageous to provide illumination in line with the optical imaging axis. For example, it can be advantageous to provide illumination along the same axis as an optical imaging axis when imaging objects over long distances, as where there is an angle between the imaging path and the illumination path, the illumination, after a certain distance, can be partially or totally outside the FOV. By having the illumination path in line with the optical imaging axis, the illumination will generally illuminate the FOV. This can further allow for increased efficiency when imaging objects over longer distances.

Additionally, by providing the illumination in line with the optical imaging axis, commissioning and set up of the optical imaging system <NUM> can be aided by allowing a user to use the illumination as a guide to understand exactly where the imaging path is. Thus, by providing illumination in line with the optical axis, an advantage of a laser based scanning system can be incorporated into an optical imaging system. In some embodiments, a beam splitter (for example, a <NUM>% transmission, <NUM>% reflection beam splitter) can be used to converge the illumination axis with the optical imaging axis. However, other optical manipulation devices can also be used. For example, a dichroic filter can be used in lieu of a beam splitter when different wavelengths are used for the illumination and imaging paths, such as when fluorescent imaging is used.

The reflective surface <NUM> of the optical reader <NUM> is used to "fold" the imaging path, as shown in <FIG>. In one embodiment, the reflective surface can be a mirror. Alternatively, other reflective materials, such as prisms, can be used. The reflective surface <NUM> can allow for the optical reader <NUM> to be placed near the closest desired reading plane. For example, the imaging lens <NUM> of the optical reader <NUM> can have a <NUM> focal length, such that to maintain the desired FOV described above would make the minimum focused distance <NUM>. This would generally require a closest reading plane to be at least <NUM> away from the imaging lens <NUM>. In some applications, the distance to the first focused plane needs to be smaller, for example, <NUM>. However, by positioning the reflective surface <NUM> at a <NUM> degree angle, the optical imaging axis <NUM> can be folded at a <NUM> degree angle. This can allow the optical reader <NUM> to be positioned closer to the closest reading plane. In the present example, assuming that the reflective surface <NUM> is positioned approximately <NUM> from the focal lens <NUM> and <NUM> from the exit window <NUM> of the enclosure <NUM>, <NUM> of the <NUM> minimum focus distance can be located within the optical imaging system <NUM>, thereby requiring only a distance of <NUM> between the exit window <NUM> of the optical imaging system <NUM> and the closest reading plane.

Turning now to <FIG>, an alternative embodiment of the optical imaging system <NUM> of <FIG> can be seen. <FIG> illustrates an optical imaging system <NUM>, the optical imaging system <NUM> can include an imaging device <NUM>. The imaging device <NUM> can include a sensor <NUM>, one or more illumination devices <NUM>, and an imaging lens <NUM>. In similar embodiments, the one or more illumination devices <NUM> can be located in the same horizontal plane as the imaging lens <NUM>. In embodiments such as this, a plurality of illumination devices <NUM> may be located on either side of the imaging lens <NUM>, such as in the orientation of illumination devices <NUM> and imaging lens <NUM> shown in <FIG>, or those other orientations discussed above. The optical imaging system further includes a reflective surface <NUM> which can be contained in an enclosure <NUM>. However, in this embodiment, the reflective surface <NUM> can be positioned approximately <NUM> from the focal lens <NUM> and <NUM> from an exit window <NUM> of the enclosure <NUM>. This can allow for zero distance between the exit window <NUM> of the optical reader <NUM> and a closest reading plane, where the imaging lens <NUM> has a <NUM> focal length. Thus, <FIG> illustrates a possible modification to the imaging path within the optical imaging system <NUM> to allow for the minimal focused distance to be contained completely within the optical imaging system <NUM>. This can allow for additional flexibility when integrating the optical imaging system <NUM> into an application.

Turning now to <FIG>, a further embodiment of an optical imaging system can be seen. <FIG> illustrates an optical imaging system <NUM>. The optical imaging system <NUM> can include an imaging device <NUM>. The imaging device <NUM> can include a sensor <NUM>, one or more illumination devices <NUM>, and an imaging lens <NUM>. The optical imaging system <NUM> can further include a first reflective surface <NUM>, a second reflective surface <NUM> and a third reflective surface <NUM>. The reflective surfaces <NUM>, <NUM>, <NUM> can be contained within an enclosure <NUM>. In this embodiment, the imaging and illumination paths can be folded by the reflective surfaces <NUM>, <NUM>, <NUM> to allow for an alternative enclosure <NUM> design. Similar to above, the reflective surfaces <NUM>, <NUM>, <NUM> can be positioned to allow for the entire minimum focused plane distance to be contained within the enclosure <NUM>, such that no additional distance is required between the exit window <NUM> and the closest reading plane. However, the reflective surfaces <NUM>, <NUM>, <NUM> could also be positioned to minimize the enclosure <NUM> size, while also limiting the additional distance required between the exit window <NUM> and the closest reading plane, as applicable. While the optical imaging system <NUM> is shown with three reflective surfaces, more than three reflective surfaces or less than three reflective surfaces can be used, as applicable.

In some examples, the multiple reflective surface optical reader <NUM> can be used in applications where the focal length of the imaging lens <NUM> requires a greater minimum focal length. For example, <FIG> shows a detailed view of a multiple reflective surface optical imaging system <NUM>. The optical imaging system <NUM> can include an imaging device <NUM>, the imaging device <NUM> including a sensor <NUM>, one or more illumination devices <NUM>, and an imaging lens <NUM>. The imaging system <NUM> can further include an optical folding device <NUM>, the optical folding device <NUM> can include a first reflective surface <NUM>, a second reflective surface <NUM> and a third reflective surface <NUM>. In one embodiment, the imaging device can be a DM150 or DM260 from Cognex. Further, a communication connection <NUM> can be seen coupled to the imaging device <NUM>. In one embodiment, the communication connection <NUM> can provide communication between the imaging device <NUM> and a processing device (not shown) such as a PC, or dedicated image processing system. In one embodiment, the communication connection <NUM> can communicate via a serial connection, such as RS-<NUM>, RS-<NUM>, Universal Serial Bus ("USB"), or via other protocols such as Firewire, Ethernet, ModBus, DeviceNet, or other applicable communication protocol. In a further embodiment, the communication link <NUM> can be a wireless communication link. For example, the communication link <NUM> can provide communication with other devices, such as the processing device discussed above, using wireless protocols such as Wi-Fi, Zigbee, Bluetooth, RF, cellular (<NUM>, <NUM>, LTE, CDMA), or other known or future developed wired or wireless communication protocols. Additionally, the communication connection <NUM> can be used to provide power to the imaging device <NUM>. Alternatively, the imaging device <NUM> may have an alternate power source, such as battery power, or a separate external power supply connection.

In this example, the imaging lens <NUM> can have a focal length of <NUM>. Thus, assuming that the first imaged plane is approximately four inches wide, the minimum object distance would be <NUM>. However, using the equations described above, a minimum focal length can be determined for any given closer and/or farther plane widths. Further, where the imaging lens <NUM> lens has a <NUM> focal length, the optical reader <NUM> can be designed to allow for <NUM> of the minimal focused distance to be folded between the reflective surfaces <NUM>, <NUM>, <NUM>. To do so, the distance (d1) between the focal lens <NUM> and the first reflective surface <NUM> can be <NUM>; the distance (d2) between the first reflective surface <NUM> and the second reflective surface <NUM> can be <NUM>; and, the distance (d3) between the second reflective surface <NUM> and the third reflective surface <NUM> can be <NUM>. Thus, a remaining distance of <NUM> is required between the third reflective surface <NUM> and an object plane <NUM> to achieve the minimal focused distance.

As the imaging and illumination planes are "folded" between the reflective surfaces <NUM>, <NUM>, <NUM>, the FOV of the imaging plane increases, requiring the reflective surfaces <NUM>, <NUM>, <NUM> to increase in size after each "fold. " Using the values discussed above, reflective surface <NUM> would require a dimension of about <NUM> about the long axis. Reflective surface <NUM> would require a dimension of about <NUM> about the long axis, and reflective surface <NUM> would require a dimension of about <NUM> about the long axis. The size of the individual reflective surfaces can be determined using the equation <MAT>, where α is the FOV angle, L is the length of the mirror, and d is the distance between the mirror and the reader (or, alternatively, between mirrors in a multiple mirror system). Thus, by varying the distances and sizes of multiple reflective surfaces, the imaging path can be "folded" to allow for a more compact installation by reducing the physical distance required between an imaging device and a first imaged plane.

Additionally, while the above optical imaging system <NUM> described as an entire system, in some embodiments it may be desirable to modify an existing imaging device (e.g. imaging device <NUM>) by incorporating an optical folding device (e.g. optical folding device <NUM>) onto the existing imaging device, to allow for existing devices to be modified accordingly.

Turning now to <FIG>, an isometric view of the optical imaging system <NUM> described above can be seen. Here, the FOV of the optical imaging path <NUM> can be seen. As seen in <FIG>, the FOV can have a substantially rectangular shape, to coincide with the imaged surface <NUM>. The shape can be chosen for processing optical codes <NUM> that may be passing through the imaged surface <NUM> in the direction shown. The rectangular shape can be caused by the windowed sensor, as discussed above. <FIG> further illustrates an enclosure <NUM> surrounding the imaging device <NUM>, and the reflective surfaces <NUM>, <NUM>, <NUM>. <FIG> shows a side view of the optical imaging system <NUM>. As seen in <FIG>, an angle of the FOV of the optical imaging path <NUM> can be seen as the image path exits the enclosure <NUM>. In the example discussed above, the output angle can be about <NUM> degrees.

Turning now to <FIG>, an alternative embodiment of a multiple reflective imaging system <NUM> can be seen. The imaging system <NUM> can include an imaging device <NUM>. The imaging device <NUM> can be an imaging device as discussed above. The imaging device <NUM> can be attached to a folding device <NUM> via an adaptor plate <NUM>. The folding device <NUM> can include a first reflective surface <NUM>, a second reflective surface <NUM>, a third reflective surface <NUM> and an exit window <NUM>. The folding device can further include illumination devices <NUM>. The illumination devices <NUM> can be a plurality of LEDs. Further, the folding device <NUM> can include an optical lens <NUM>. The optical lens <NUM> can be positioned at the output of the illumination devices <NUM>. In one embodiment, the optical lens <NUM> can create a line pattern using the output from the illumination devices. As discussed above, this can aid in commissioning and setup of the imaging system <NUM> by allowing a user to visualize where the optical imaging path is located, and to improve the illumination system efficiency. For example, the optical lens <NUM> can be used to shape the illumination to match a conjugate active portion of a sensor <NUM> in the imaging device <NUM> to match the illumination pattern to the imaging path FOV.

Turning now to <FIG>, a further embodiment of an optical reader can be seen as optical reader system <NUM>. The optical reader system <NUM> can include an imaging device <NUM> having an imaging lens <NUM>, a first reflective surface <NUM>, a second reflective surface <NUM>, and a third reflective surface <NUM>. The optical reader system <NUM> can further include one or more illumination devices <NUM>. In the embodiment of <FIG>, the illumination devices <NUM> can be located at the exit of the optical reader system <NUM> and adjacent to an exit window <NUM>. This can allow for an illumination axis <NUM> to have generally the same axis as an imaging axis <NUM>. Further, the illumination devices <NUM> can be configured to project light such that the imaging object <NUM> is illuminated throughout the imaging FOV <NUM>.

Turning now to <FIG>, a further embodiment of an optical reader system can be seen as optical reader system <NUM>. The optical reader system <NUM> can include an optical imaging device <NUM> having an imaging lens <NUM>, a first reflective surface <NUM>, a second reflective surface <NUM>, and a third reflective surface <NUM>. In one example, the optical imaging device <NUM> can be an optical imaging device as described above. The optical reader system <NUM> can also include one or more illumination devices <NUM>. In one embodiment, the illumination devices <NUM> can be positioned behind the first reflective surface <NUM>. The reflective surface <NUM> can be configured to allow the illumination to pass through the first reflective surface <NUM> and to align an illumination axis <NUM> with an imaging axis <NUM>. In one embodiment, the first reflective surface <NUM> can be a beam splitter. Alternatively, the first reflective surface <NUM> can be a dichroic filter. By aligning the illumination axis <NUM> with the imaging axis <NUM>, an imaging object <NUM> can be illuminated on axis through the imaging FOV <NUM>.

<FIG> illustrates an illumination distribution pattern <NUM> where an illumination path is transmitted along the same, or similar, axis as an optical imaging path. Here, the imaging FOV <NUM> is shown as being projected from an optical imaging system <NUM>. Similarly, the illumination distribution pattern <NUM> within the imaging FOV <NUM> is shown projected onto an imaging object <NUM>. As seen in <FIG>, the most intense illumination is shown in the darker portions of the illumination distribution pattern <NUM>, which is elongated in shape to coincide with the imaging FOV <NUM>. This distribution of illumination shown in illumination distribution pattern <NUM> can provide full illumination of the imaging object <NUM> to allow for more efficient and accurate imaging. If the sensor in the optical imaging system <NUM> is windowed to a predetermined number of lines of pixels, as described above with reference to <FIG>, the illumination field <NUM> can be conjugated with that number of lines of pixels, such that the illumination field <NUM> does not extend beyond the imaging FOV <NUM>. Although the imaging FOV <NUM> is constrained in <FIG>, it is important to note that the illumination field <NUM> can extend beyond the imaging FOV in multiple directions.

Turning now to <FIG>, a plurality of illumination optics <NUM>, <NUM>, and <NUM> can be seen. <FIG> illustrates an exemplary image of a freeform illumination lens <NUM>. The freeform illumination lens can be specifically formed to shape and/or pattern illumination from an illumination device. <FIG> illustrates an exemplary image of a cylindrical lens <NUM> for use with an illumination device. Finally, <FIG> illustrates a reflective optic <NUM> for use with an illumination device, in this example a total internal reflection (TIR) lens. Each of the illumination optics <NUM>, <NUM>, <NUM> described above can be used to help shape and or pattern illumination from an illumination device, such as those described above.

Turning now to <FIG>, a further embodiment of an optical reader system can be seen as optical reader system <NUM>. The optical reader system <NUM> can include an optical imaging device <NUM> having an imaging lens <NUM>, a first reflective surface <NUM>, a second reflective surface <NUM>, and a third reflective surface <NUM>. The optical imaging device <NUM> can also include one or more illumination devices <NUM>. The illumination devices <NUM> can be configured to align an illumination axis with an imaging axis. The optical reader system <NUM> can further include an exit window <NUM>. In one embodiment, the exit window <NUM> can be tilted at an angle to reduce reflections along the imaging axis. In one embodiment, the exit window <NUM> can be angled. In some embodiments, the exit window <NUM> is angled at approximately <NUM> degrees. However, the exit window can be angled at more than <NUM> degrees or less than <NUM> degrees, as applicable. For instance, the exit window may be angled at approximately <NUM> degrees. Further, while the exit window <NUM> is shown in <FIG> as angling from left to right, the direction of the angle can be modified for use in a given application to provide the optimal amount of reflection reduction.

Turning now to <FIG>, a process <NUM> for sensing an optical code using an optical imaging system as discussed above, can be seen. At process block <NUM> an illumination pattern can be generated. In one embodiment, the illumination pattern can be generated using a plurality of illumination devices as discussed above. Further, in some embodiments the illumination pattern can be shaped or filtered as described above, at process block <NUM>. For example, the illumination pattern may be shaped using beam splitters, dichroic filters, and/or by positioning the illumination devices in a pattern corresponding to a desired illumination pattern, and placed within the illumination path. In one embodiment, the illumination devices can be LEDs. At process block <NUM> the imaging path is focused using a lens of an optical imaging system. In one embodiment, the imaging path can be focused based on the focal length of the lens.

At process block <NUM> the imaging path is folded. In some embodiments, the imaging path can be folded using a plurality of reflective surfaces. For example, mirrors can be used to fold the imaging path, as described above. Folding the imaging path can allow for some or all of the minimum focus distance to be contained within the optical imaging system. Reduction of the focus distance by folding the imaging path is discussed in more detail above. At process block <NUM>, the imaging path can be filtered. In some optional embodiments, the imaging path is filtered at an exit window of the optical imaging system. For example, the exit window may have an ultraviolet filter, a polarized filter, a dichroic filter, or other filter as applicable. The exit window can also be tilted to provide filtering to reduce reflections from being returned along the imaging path. The exit window can be tilted between <NUM> and <NUM> degrees, such as, for example <NUM> degrees. The sensor is windowed <NUM> such that only a predetermined portion of the sensor is used to sense objects. As discussed above with reference to <FIG>, windowing can increase the sensing speed and refresh rate of the sensor by reducing the active pixel area. Finally, at process block <NUM>, an object in the imaging path can be sensed via the sensor of the optical imaging system. Additionally, in some embodiments, the image is registered and processed after the completion of process block <NUM>.

<FIG> is a graphical representation of another windowed sensor. <FIG> shows a sensing area in which only a portion of the sensing face <NUM> remains active. In some embodiments, the active pixel area <NUM> can be sized to the expected FOV required to view a particular code. For example, where a one dimensional bar code is expected to be scanned in a particular orientation (e.g., vertical or horizontal), the active pixel area <NUM> can be oriented similarly (vertically or horizontally). Further, as only a portion of the width of the given code is required for a one dimensional code, the active area <NUM> can be reduced to a few lines of pixels with a second inactive area (e.g., the second inactive area <NUM> described above in connection with <FIG>). For example, the active sensing area <NUM> can be reduced to between <NUM> lines and <NUM> lines. Alternatively, in some embodiments, the active pixel area <NUM> can substantially correspond to a cropped field of view of the image sensor. For example, as described below in connection with <FIG>, <FIG>, the image sensor and lens can be disposed with respect to a reflective surface (or one of multiple reflect surfaces) such that a portion of the field of view of the image sensor is not folded by a reflective surface. In such an example, a portion of the field of view can be cropped at a target plane, and the inactive area <NUM> can substantially correspond to the portion of the field of view that is cropped. As described below in connection with <FIG>, disposing the reflective surface to fold only a portion of the field of view can facilitate a reduction of one or more exterior dimensions of a device incorporating the windowed sensor. However, more or fewer lines of pixels can also be used. For example, for a sensor having a resolution of <NUM> lines that each include <NUM> pixels, and a frame rate of <NUM> frames per second, by using only about <NUM> lines of <NUM> pixels (e.g., about <NUM>% of the image sensor), the active sensing area <NUM> can be reduced by a factor of <NUM>/<NUM> and the frame rate can be increased (e.g., by a corresponding factor of <NUM>/<NUM> to about <NUM> frames per second for an image sensor configured to have a full image frame rate of <NUM> frames per second). In other words, the active sensing area <NUM> can be reduced by <NUM>%, and the frame rate can be increased by about <NUM>% (e.g., at <NUM> lines per image and a frame rate of <NUM> frames per second, the image sensor reads out about <NUM>,<NUM> lines in a second, and at <NUM> lines per image and a frame rate of <NUM> frames per second, the image sensor reads out about <NUM>,<NUM> lines in a second). In some embodiments, such an increase in frame rate can facilitate increased scanning speed and throughput when using an optical imaging system. In some embodiments, an image sensor configured with a higher full image frame rate (e.g., <NUM> frames per second, <NUM> frames per second, <NUM> frames per second, <NUM> frames per second, etc.) can be used to facilitate further increases in the frame rate. Note that although an image sensor having a resolution of <NUM> × <NUM> pixels is described above, this is merely an example, and the mechanisms described herein can be used with a image sensor having any suitable resolution (e.g., <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, <NUM> × <NUM>, or any other suitable resolution). In some embodiments, the image sensor can be configured to use a global shutter (e.g., in which each pixel records a value simultaneously). However, this is merely an example, the image sensor can be configured to use a rolling shutter (e.g., in which lines of the image sensor are exposed in a sequential manner), or other type of shutter. These examples may require additionally processing to correct an image for motion artifacts caused by motion of an object being imaged (e.g., a code on a box being moved by conveyor belt).

<FIG> is a graphical representation of another windowed sensor sensing a one dimensional bar code moving in a defined direction. Turning now to <FIG>, the sensing face <NUM> of <FIG> is shown imaging a one dimensional bar code <NUM> as it passes through the sensing face <NUM> in the direction shown. Note that the orientation of the imaged code is such that the active sensing area <NUM> is able to image all of the data in the bar code <NUM>, even though only a portion of the sensing face <NUM> is active. In some embodiments, the active sensing area <NUM> can be oriented horizontally to coincide with a portion of the field of view that is cropped by one or more optical components of an imaging system using the image sensor (e.g., as described below in connection with <FIG>, <FIG>).

<FIG> is a system view of an alternate one fold optical reader with longer inner path. <FIG> illustrates an optical imaging system <NUM>, the optical imaging system <NUM> can include an imaging device <NUM>. The imaging device <NUM> includes an imaging lens <NUM>, and an image sensor disposed at a focal length of the imaging lens. Although not shown, in some embodiments, one or more illumination devices (e.g., as described above in connection with <FIG>, <FIG>, <FIG>, <FIG>) can be disposed in any suitable configuration in connection with the imaging device <NUM> and/or the imaging lens <NUM>. The optical imaging system <NUM> further includes a reflective surface <NUM> which can be contained in an enclosure <NUM>. In some embodiments, the reflective surface <NUM> can be positioned approximately <NUM> from the imaging lens <NUM> and about <NUM> from an exit window <NUM> of the enclosure <NUM> along an optical imaging axis <NUM>. Note that this is one example, and the distance from the imaging lens <NUM> to the reflective surface <NUM> can be in a range of about <NUM> to about <NUM> depending on the application (e.g., based on the working distance from optical imaging system), and the distance from the reflective surface <NUM> to exit window <NUM> (along the optical axis) can be in a range of about <NUM> to about <NUM>. In more particular examples, the distance from the imaging lens <NUM> to the reflective surface <NUM> can be in a range of about <NUM> to about <NUM>, or in a range of about <NUM> to <NUM>, and the distance from the reflective surface <NUM> to exit window <NUM> (along the optical axis) can be in a range of about <NUM> to about <NUM>, or in a range of about <NUM> to <NUM>. In some embodiments, the exit window <NUM> can be disposed to be parallel to reflective surface <NUM>. Alternatively, the exit window <NUM> can be disposed at an angle of ± <NUM> degrees from parallel to the reflective surface <NUM>. In a particular example, the exit window <NUM> can be disposed at an angle of ± <NUM> degrees from parallel to the reflective surface <NUM>. Angling exit window <NUM> with respect to the optical imaging axis <NUM> can reduce internal reflections back along the imaging axis. However, as an angle of exit window <NUM> increases with respect to reflective surface <NUM>, exit window <NUM> can cause an increase in internal reflections back along the imaging axis. Additionally, angling the exit window <NUM> can reduce one or more dimensions of the optical imaging system <NUM>. For example, angling the exit window <NUM> away from the imaging device <NUM> (e.g., counterclockwise in <FIG>) can reduce a total height of the optical imaging device <NUM> (e.g., by shifting a corner <NUM> of the enclosure <NUM> toward reflective surface <NUM>). As another example, angling the exit window <NUM> toward the imaging device <NUM> (e.g., clockwise in <FIG>) can reduce a length of the optical imaging device <NUM> (e.g., by shifting the corner <NUM> of the enclosure <NUM> toward the imaging device <NUM>). In some embodiments, the reflective surface <NUM> can be formed using a mirror, a prism, a dichroic filter, and/or or any other suitable reflective surface. In some embodiments, a size of exit window <NUM> can be defined by a through hole in enclosure <NUM>. Additionally, in some embodiments, exit window <NUM> can formed from a transparent (at least in certain wavelengths) material, such as glass, plastic, etc. In some embodiments, exit window <NUM> can include one or more filters (e.g., as described above in connection with exit window <NUM> of <FIG>, and in connection with <FIG>.

The reflective surface <NUM> is disposed at an angle to the optical imaging axis <NUM> of greater than <NUM> degrees, which can result in a field of view <NUM> that is shifted toward optical imaging system <NUM> compared to a field of view <NUM> that would result from the reflective surface <NUM> being angled at <NUM> degrees. Additionally, disposing the reflective surface <NUM> at an angle to the optical imaging axis <NUM> of greater than <NUM> degrees can facilitate a reduction in the height h of corner <NUM> (e.g., from a. A reduction in the height of the corner <NUM> can facilitate use of the optical imaging device <NUM> in spaces with smaller height clearances. For example, the optical imaging device <NUM> can be installed between two conveyor belts, and reducing the overall height of the optical imaging device <NUM> can permit a space between the two conveyor belts to be reduced, which can facilitate more efficient use of space in a facility. In the arrangement shown in <FIG>, the reflective surface <NUM> is arranged at an angle of <NUM> degrees with respect to the optical imaging axis <NUM>. However, this is merely an example, and the reflective surface can be disposed at a different angle resulting in a different amount of shifting of the field of view <NUM> with respect to the field of view <NUM>. For example, the reflective surface can be angled at any suitable angle between <NUM> degrees and <NUM> degrees. In more particular examples, the reflective surface <NUM> can be angled at <NUM> degrees, at <NUM> degrees, at <NUM> degrees, at <NUM> degrees, at <NUM> degrees, or at an angle between two whole degrees (e.g., <NUM> degrees, <NUM> degrees, etc.). As used herein, an angle of about (or approximately) X degrees can include any angle of X ± <NUM> degrees.

As shown in <FIG>, the reflective surface <NUM> can be sized and/or positioned such that only a portion of the FOV of the image sensor is reflected (or folded) toward the exit window <NUM>. For example, the reflective surface <NUM> can be positioned such that the optical imaging axis <NUM> intersects the reflective surface closer to one side than the other (e.g., off center), which can cause the FOV to be divided asymmetrically with respect to the optical imaging axis <NUM> (e.g., with more lines on one side of the optical imaging axis <NUM> than on the other). As shown in <FIG>, with the reflective surface <NUM> positioned off center from the optical imaging axis <NUM>, resulting in a portion <NUM> of the field of view being cropped. Note that this is merely an example, and the reflective surface <NUM> may or may not be centered with respect to the optical imaging axis <NUM>, and may or may not be sized and/or positioned such that only a portion of the FOV of the image sensor is reflected (or folded) toward the exit window <NUM>. For example, the reflective surface <NUM> can be centered or not centered on the optical imaging axis, and can be sized such that a smaller portion of the FOV of the image sensor is reflected (or folded) toward the exit window <NUM> than in the example shown in <FIG>. In a particular example, the reflective surface <NUM> can be sized such that only a central portion of the FOV is reflected by the reflective surface <NUM>, and a first portion of the FOV above (in the context of <FIG>) the reflective surface <NUM> and a second portion of the FOV below the reflective surface <NUM> are not reflected. In some embodiments, for example as shown in <FIG>, by angling the reflective surface <NUM> at greater than <NUM> degrees with respect to the optical imaging axis, the size of the cropped portion <NUM> can be reduced. The configuration shown in <FIG> can have a FOV at a working distance of about <NUM> of about <NUM> by about <NUM> if the entire field of view of the image sensor were reflected by reflective surface <NUM>. However, in the configuration shown in <FIG>, the cropped portion <NUM> can reduce the FOV to about <NUM> by about <NUM>, which can be distributed asymmetrically around the optical imaging axis <NUM>. As used herein, an distance of about (or approximately) Xmm can include any distance of Xmm ± <NUM>. In the configuration shown in <FIG>, a wall <NUM> of the enclosure <NUM> can reflect light (e.g., light entering through exit window <NUM>, light originating within the enclosure <NUM> such as from one or more illumination devices disposed within the enclosure <NUM>) toward the imaging lens <NUM> due to the angle at which the wall <NUM> is disposed with respect to the imaging lens <NUM>. In some embodiments, an interior surface of the wall <NUM> can be configured to reduce an amount of light reflected toward the imaging lens <NUM>. For example, the interior surface can be textured to reduce the amount of light reflected toward the imaging lens <NUM> (e.g., by roughening the surface). As another example, the interior surface can be configured to have a dark matte finish (e.g., by painting the interior surface with a black matte paint, by adhering a dark matte material such as a sticker to the interior surface).

Note that angling the reflective surface <NUM> at an angle greater than <NUM> degrees can result in the depth of field being tilted with respect to a target plane that is oriented at <NUM> degrees from an imaging plane of the image sensor. For example, for a reflective surface at <NUM> degrees, the focal plane (e.g., a plane at which a point object produces a point at the imaging plan) is perpendicular to the imaging plane, and the depth of field can be disposed around the focal plane such that a first plane (e.g., first plane <NUM> or first plane <NUM>) at which a target can be considered in focus (e.g., having a circle of confusion below a pixel pitch of the image sensor) and a second plane (e.g., second plane <NUM>, second plane <NUM>) at which a target can be considered in focus are also perpendicular to the imaging plane. However, for a reflective surface at angle of greater than <NUM> degrees (or less than <NUM> degrees), the focal plane, the first plane, and the second plane are tilted with respect to a target plane that is oriented at <NUM> degrees from an imaging plane of the image sensor. Accordingly, a flat object (e.g., a side of a box on which a code has been placed) can be imaged as though the object is tilted, which can result in a portion of the code being out of focus if the focal plane and depth of field are sufficiently tilted.

In some embodiments, using a lens with a focal length of <NUM>, a distance between the lens and reflective surface <NUM> of about <NUM>, and a height h of about <NUM>, a closest reading plane can be about <NUM> from imaging lens <NUM> along the optical imaging axis (e.g., just beyond corner <NUM>). In an example in which the about <NUM> of the optical path length is included within the imaging system (e.g., imaging system <NUM>), the closest reading plane can be about <NUM> from the exit window along the optical imaging axis <NUM>.

As described above in connection with <FIG>, in some embodiments, the imaging device <NUM> can be mechanically attached to enclosure <NUM> via an adaptor plate. In such embodiments, enclosure <NUM>, reflective surface <NUM>,and exit window <NUM> can form a folding attachment device for an existing optical imaging device (e.g., imaging device <NUM>).

<FIG> illustrate a correspondence between a cropped portion of a field of view and windowing that can be applied to an image sensor. As shown in <FIG>, a portion of the FOV can be cropped in the Y direction. In the example shown in <FIG>, the FOV is cropped by about <NUM>%, which results in a change in the FOV at a working distance of <NUM> from a "top" surface of the imaging device <NUM>, which can cause the FOV to be divided unevenly (or asymmetrically) around the optical imaging axis. As shown in <FIG>, an angle between the optical imaging axis and the reflective surface (angle "A" in <FIG>) can be about <NUM> degrees. By using an angle A of greater than <NUM> degrees, the size of the housing can be reduced (e.g., by shifting or shortening the exit window laterally in <FIG>) as compared to using a reflective surface angled at <NUM> degrees. As shown in <FIG>, by using an angle A of greater than <NUM> degrees, the size of the cropped area given a similarly sized housing, can be reduced (e.g., by about <NUM>% compared to the size of the cropped area were a <NUM> degree reflective surface used).

Note that although only a single reflective surface is described in connection with <FIG>, <FIG>, this is merely an example, and multiple reflective surfaces can be used to fold the optical path multiple times between the imaging lens and the exit window (e.g., as described above in connection with <FIG>) while using at least one reflective surface angled at greater than <NUM> degrees to shift the FOV (e.g., toward or away from the imaging lens).

<FIG> illustrates a correspondence between a tilted field of view and reading areas of an image sensor. As shown in <FIG>, tilting the reflective surface <NUM> at an angle greater than <NUM> degrees to the optical axis can cause the FOV <NUM> to shift toward the imaging lens <NUM>. As described above in connection with <FIG>, a reading area can begin near corner <NUM>, and can extend to a working distance (e.g., about <NUM>). In some embodiments, details (e.g., details of codes) in a distal portion <NUM> of FOV <NUM> may be less clearly captured, as crosssectional area of the FOV area increases and each pixel is averaged over a larger portion of the scene.

Claim 1:
An optical imaging device (<NUM>) for reading optical codes; the device comprising:
an area sensor comprising a first plurality of lines of pixels, the area sensor being configured to sense with only a second plurality of lines of pixels, the second plurality of lines of pixels being arranged in a predetermined position of the area sensor and including fewer lines of pixels than the number of lines of pixels in the first plurality of lines of pixels;
a lens (<NUM>), the lens (<NUM>) having an optical axis forming a portion of an optical imaging axis (<NUM>) of the optical imaging device (<NUM>);
an exit window (<NUM>) angled to the optical imaging axis (<NUM>); and
a reflective surface (<NUM>) disposed along the optical imaging axis (<NUM>) between the lens (<NUM>) and the exit window (<NUM>), the reflective surface (<NUM>) being configured to fold the imaging axis (<NUM>), characterized in that the reflective surface (<NUM>) is tilted at an angle (A) of at least <NUM> degrees with respect to the optical axis of the lens (<NUM>).