CN100423017C - Semiconductor Devices Suitable for Imaging Barcode Symbols - Google Patents

Abstract

A semiconductor device or miniaturized imager for imaging optical code symbols comprising not more than 1024 pixels, wherein each pixel has an aspect ratio greater than 2:1 and a short dimension not greater than 4 μm nor less than 2 μm, preferably Sets pixels in a single row. Optical and electrical systems of the miniaturized imager are optimized to reduce one or more dimensions or volumes of the imager. The semiconductor has an acquisition surface that can form no less than 256 and no more than 1024 pixels. Also provided is a bar code reader comprising a sensor for imaging the field of view of the reader comprising the single semiconductor device described above. Apparatus and techniques are provided that reduce and/or eliminate the need for imager target illumination, thereby reducing the overall power consumed by the imager and/or its overall size. An imager with an extended operating range is provided, as well as a light emitting diode that produces light with a reduced linewidth.

Description

Semiconductor Devices Suitable for Imaging Barcode Symbols

technical field

The present invention relates generally to semiconductor devices suitable for imaging optical code symbols, particularly bar code symbols, and to bar code readers including such semiconductor devices. In particular, the invention relates to imaging systems using solid-state sensors for detecting multiple image elements, including optically coded imagers and cameras. The situation of the present invention is particularly applicable to hand-held readers based on linear sensors and based on two-dimensional sensors. More particularly, the present invention relates to simplified elemental imagers.

Background technique

Optical codes are patterns composed of image regions with different light reflection or light emission properties, usually assembled according to existing rules. The term "barcode" is sometimes used to describe a certain kind of optical code. The optical properties and patterns of the selected optical codes are distinguished in appearance from the background environment in which they are used. Devices used to identify or extract data from optical codes are sometimes called "optical code readers," and barcode scanners are one type. Optical code readers can be installed in many different applications, both fixed and portable, such as in storage for inspection services, in production sites for workflow and inventory control, and in shipping vehicles for tracking packaging handling. Optical codes can be used as a rapid and versatile data entry device, for example, by reading a target barcode from a printed array of many barcodes. In some uses, the optical code reader is connected to a portable data processing device or a data collection and transmission device. Typically, optical code readers include hand-held sensors that are manually pointed at the target code.

Most traditional code readers are designed to read one-dimensional bar code symbols. A barcode is a pattern of rectangular bars of different widths separated by fixed or varying width intervals. Bars and spaces have different light reflection properties. An example of a one-dimensional barcode is a UPC/EAN code used for identification, such as a product inventory code.

Barcodes can be read using solid-state imaging devices. For example, an image sensor having a two-dimensional array of cells corresponding to picture elements or pixels in the field of view of the device or an optical sensor may be used. Such an image sensor may be a two-dimensional or area array charge-coupled device (CCD) and associated circuitry for generating electrical signals corresponding to pixel information of the field-of-view two-dimensional array. The use of one-dimensional linear photodiode arrays for detecting reflected images of barcodes is also known, eg, US Patent No. 6,138,915 to Danielson et al., which is also incorporated herein by reference.

As is well known in the art, optical code readers use a CCD image sensor and objective lens assembly. In the past, such systems employing complex objective lens assemblies were originally designed for relatively expensive video imaging systems. Such systems may have individually sharp focus and limited deepest range, which together with traditional aiming, lighting and signal processing and decoding algorithms limit the system's versatility and operating range.

Another known imaging system is designed primarily for reading optical codes. Such a Reading System consists of the combination and arrangement of several widgets. These components may include lenses, apertures, and 2D image sensor arrays such as CCD chips. Such structures are described, for example, in WO99/64980, which is incorporated herein by reference. A compact imager suitable for a hand-mounted code reader is disclosed in US Patent Application Serial No. 09/648,514, filed October 10, 2000 by Patel et al., which is also incorporated herein by reference.

The design of the imaging system is independent of the size of the package in which the imaging system is to be produced. Conventional imaging systems utilizing off-the-shelf components are difficult to miniaturize due to limited selection of off-the-shelf components. In addition, due to different optical phenomena in the design of miniaturized imagers, the trade-off between component size and scanned image quality must be weighed in the selection of components. Furthermore, the selection of certain components for use in an imager can limit the selection of other components for a miniaturized imager due to optical phenomena.

Contents of the invention

Accordingly, an object of the present invention is to provide a semiconductor device for imaging an optical code symbol, a miniaturized imager, and a bar code reader including such a semiconductor device.

Another object of the present invention is to provide a semiconductor device or a miniaturized imager capable of providing a suitable scanned image while miniaturizing the physical size and shape of the device, ie form factor.

Semiconductor devices or miniaturized imagers for imaging optical code symbols are often used in portable applications where semiconductor devices can be incorporated into hand-held devices. These handheld device devices have limited battery capacity.

An object of the present invention is to provide a semiconductor device or a compact imager suitable for imaging barcodes that uses a small amount of power in the acquisition and processing of images.

It is an object of the present invention to broaden the working range of an imaging system.

Traditional imaging systems employing solid-state imagers are limited by the distance that separates the target image from the imager's lens that the target imager can correctly decode. In particular, in conventional imaging systems, the plane of the solid-state imager pixel array is arranged perpendicular to the optical axis of the focusing lens. Therefore, the pixels of a solid-state imager are all focused on the same spatial plane of the target image.

Pixels all focused on the same spatial plane severely limit the working range of the imaging system, such as the distance between the imaging system and the target image. If a conventional imaging system has only a single fixed focus lens, an adjustment must be made between the imaging system and the target image in order to properly receive and decode the target image.

To provide illumination and facilitate aiming, imaging systems may employ lasers or light emitting diodes (LEDs). LEDs can be preferred over lasers because the incoherent nature of LED light sources does not produce the speckle noise effects produced by lasers. In addition, LEDs can be more cost-efficient than lasers due to the ease of producing and packaging them. Not only that, but LEDs can be manufactured more compactly and are easier to surface mount than lasers. However, compared to lasers, LEDs are not ideal point light sources. In particular, the light generated by the LEDs is less focused, resulting in an increase in the linewidth of the projected light. In order to reduce the linewidth of the light produced by the LED, many designers place mechanical slits in the front of the LED. However, the mechanical cutout reduces the amount of light the LED casts on the target.

It is therefore an object of the present invention to provide an LED having a reduced projected light linewidth without severely reducing the amount of light projected by the LED.

In a miniaturized imager that can be used in conjunction with the present invention, the pixel width or pitch of the imaging array is reduced compared to larger sized imagers while maintaining the instantaneous time per pixel compared to larger sized imagers. The area of the field of view and aperture. According to this embodiment, an imager with a pixel width or pitch of 4 μm can be produced with a detector array length less than or equal to 2 mm. According to one aspect of this embodiment, a one-dimensional imager can be produced with a pixel width or pitch of approximately 3 μm and a detector array length of approximately 0.75 mm by interleaving rows of pixels with half pixels relative to each other.

In another embodiment, an imager is provided that has a very small form factor and can be operated with little or no artificial illumination provided by the imager, thereby providing very low power operation. According to this embodiment, an imager chip is mounted on an imaging board within the imager housing. The imager housing forms a dark chamber around the imager chip, allowing the imager to operate without an external seal. According to one aspect of this embodiment, the size of the aperture can be increased so that the need for an imaging engine to provide artificial illumination can be reduced and/or eliminated. According to another aspect of this embodiment, a low noise imager with gain is provided to reduce and/or eliminate the need for an imaging engine to provide artificial lighting. According to yet another aspect of this embodiment, an imager capable of providing a non-linear response, such as a logarithmic imager, may be configured to reduce and/or eliminate the need for an imaging engine to provide artificial illumination.

According to another embodiment, an imager includes an image sensor and a focusing lens. The imager sensor has an array of pixels in a first plane and the focusing lens has an optical axis in a second plane. Arranging the first and second planes so that they are not perpendicular to each other increases the working range of the imager.

According to another embodiment, a device comprises a light emitting diode having a square portion and a rectangular portion, wherein the height and width of the rectangular portion are not equal to the height of the square portion. The device also includes a bond pad, wherein the bond pad is located on the square portion. According to an aspect of this embodiment, the light emitting diode further includes a second square portion, wherein the rectangular portion has first and second sides with a height dimension, wherein the square portion is located on the first side of the rectangular portion, and the second square portion is located on the first side of the rectangular portion. The second side of the rectangular section. The second bond pad is located on the second square portion. According to another embodiment, the LED die includes a rectangular shaped LED surrounding a bonding pad of the LED.

The above topics can be further defined as follows:

The imager comprises a solid-state image sensor for generating an electrical signal corresponding to an image of an object, wherein the image sensor comprises a pixel array having a pixel number of less than or equal to 1024 pixels and each pixel having a width or pitch of less than or equal to 4 μm; and an aperture for receiving light reflected from the target and passing the reflected light to an image sensor, wherein preferably, the image sensor is a one-dimensional image sensor, the number of pixels is less than or equal to 1024 pixels, and each pixel has a width of equal to 3 μm, whereby the array length is less than or equal to 1.5 mm, or wherein the number of pixels in the image sensor is less than or equal to about 500 pixels, each pixel has a width equal to 3 μm, and wherein the pixels are arranged adjacent to each other Two rows, one offset from the other by half a pixel, whereby the array length is less than or equal to 0.75 mm. Preferably, the above image sensor is a two-dimensional image sensor, whereby the longest length of the array is less than 2 mm. In particular, the above image sensor may be a CMOS detector array. The above image sensors are preferably suitable for mounting on printed circuit boards using reflow soldering techniques. The above imager may further comprise an illumination/aiming light emitting diode; an illumination/aiming lens; an imaging lens, wherein the imaging lens is disposed in an aperture, wherein the aperture is included in a molded package. Preferably, the imager has dimensions less than or equal to 5 mm x 3 mm x 2.25 mm.

In another aspect, there is provided an imager comprising an imager housing comprising an imager chip; a lens, wherein the lens is incorporated into the imager housing opposite the imager chip, and wherein the imaging housing has a volume less than or equal to 3.3 cm ³ (0.20 cubic inches). Preferably, the imager chip is housed in a dark chamber, allowing the imager to operate without external sealing. Advantageously, the imager has a maximum volume of 20.6 x 14.2 x 11.4 mm ³ . In a preferred embodiment, the imaging housing further includes a light emitting device for illuminating the target image, and/or the imaging housing includes an aperture, wherein the size of the aperture is selected to facilitate scanning of the target image when illumination of the imager is provided. Preferably, the above imager chip is a low-noise imager with gain, so that the target image can be scanned without the illumination of the imager. The above imager chip may be a logarithmic response imager, thereby improving the contrast between dark and bright portions of the target image, thereby enabling scanning of the target image without illumination of the imager.

According to another aspect, there is provided an imager comprising an imager housing, which includes an imager chip; a lens, wherein the lens is incorporated into the imager housing opposite the imager chip, and wherein the imager chip is a low Noise imager, which enables scanning of target images without imager illumination. Preferably, the imager housing has a volume of less than or equal to 3.3 cm ³ (0.20 cubic inches).

Still further, there is provided an imager comprising an imager housing, which includes an imager chip; a lens, wherein the lens is incorporated into the imager housing opposite the imager chip, and wherein the imager chip provides a A non-linear intensity response of light reflection to enable scanning of the target image without imager illumination, wherein preferably the non-linear representation is a logarithmic representation of the target image. Similarly, the imager housing preferably has a volume of less than or equal to 3.3 cm ³ (0.20 cubic inches).

According to yet another aspect, there is provided an imager comprising an imaging sensor mounted on a printed circuit board; an aperture, wherein the imager has a volume of less than or equal to 3.3 cm ³ . Preferably, the size of the imager is equal to or less than 20.6×14.2×11.4 mm. The imager may also contain light emitting diodes to provide illumination of the target image, and/or light emitting diodes to illuminate the target on the target image to facilitate aiming the imager.

In addition, there is provided an imager comprising a two-dimensional image sensor comprising a portion of its image elements horizontally aligned in a first plane; focusing optics having an optical axis, wherein the image sensor is oriented such that the first plane is out of contact with the light The axes are vertical and provide different focal lengths for different image elements. Preferably, the focusing optics comprise an objective symmetrically comprising a plane substantially non-parallel to the first plane. The imager may also contain light emitting diodes that provide illumination of the target image.

According to another aspect, there is provided a device including a light emitting diode, which has a square portion and a rectangular portion, wherein the height and width of the rectangular portion are not equal to the height of the square portion; partly on. In a particular embodiment, the rectangular portion has a height-sized first and second side, wherein the light emitting diode further comprises a second rectangular portion, wherein the square portion is located on the first side of the rectangular portion, and the second square portion is located on the side of the rectangular portion. The second side, and wherein the second bonding sheet is located on the second square portion.

Also provided is a device comprising a rectangular light emitting diode; and a bond pad, wherein the bond pad surrounds the light emitting diode so as to provide uniform light power emitted from the light emitting diode.

According to the present invention there is provided a semiconductor device for imaging an optical code symbol comprising not more than 1024 pixels, wherein each pixel has a short dimension not greater than 4 μm and not less than 2 μm, having an aspect ratio greater than 2 : 1, wherein preferably, the pixels are arranged in a single row. In addition, the semiconductor device may have a collection surface which may be provided with not less than 256 and not more than 1024 pixels.

According to another aspect of the present invention, there is provided a barcode reader including a sensor for imaging a field of view of the reader including the above-mentioned single semiconductor device.

Also described here is a miniaturized imager for reading target images. Optical and electrical systems of the miniaturized imager are optimized to reduce one or more dimensions or volumes of the imager. According to one embodiment, the pixel width or pitch and focal length are reduced from the size of the larger imager to maintain the relative field of view of each pixel. The reduced pixel width or pitch keeps the area of the aperture and the instantaneous field of view of the pixel constant while reducing the overall size of the imager. In other embodiments, devices and techniques are provided that reduce and/or eliminate the need for an imager to illuminate a target, thereby reducing the overall power consumed by the imager and/or its overall size. An imager with a widened operating range is provided because the light emitting diodes produce light with a reduced linewidth.

Description of drawings

Objects and advantages of the present invention will be understood by reading the following detailed description in conjunction with the accompanying drawings, in which:

Figures 1A and 1B depict top and side views, respectively, of the miniaturized imager;

Figures 2A-2C depict a top view, front view and side view, respectively, of another miniaturized imager;

Figure 3 depicts another miniaturized imager;

Figure 4 depicts the electrical components of the miniaturized imager;

Figure 5 depicts the imager with extended working range;

Figure 6A depicts a conventional LED;

Figure 6B depicts an LED that can be used with the present invention;

Figure 6C depicts another LED that can be used with the present invention;

Figure 6D depicts yet another LED that can be used with the present invention;

Figure 6E depicts yet another LED that can be used with the present invention; and

Fig. 7 depicts a semiconductor device according to the present invention.

Detailed ways

The following description is for purposes of explanation and not limitation, and specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known methods, devices, and circuits may be omitted so as not to obscure the description of the present invention.

Figures 1A and 1B depict top and side views, respectively, of a miniaturized imager. The imager is incorporated into a molded light package 110 . This structure and technique is disclosed in U.S. Patent Application Serial No. 09/880,906, entitled "Molded Imager Optical Encapsulation and Linear Detector-Based Scan Engine," filed June 15, 2001 by Mazz et al., and thus Use this specifically as a reference. The molded light package includes an imaging/decoding integrated circuit (IC) 120 , an illumination/aiming light emitting diode (LED) 130 , an imaging lens 140 and an illumination/aiming lens 150 . According to an embodiment of the present invention, imaging/decoding IC 120 is fabricated according to known complementary metal oxide semiconductor (CMOS) technology. Likewise, imaging/decoding IC 120 may comprise a CCD imager with associated decoding circuitry.

In operation, imaging/decoding IC 120 receives an image through imaging lens 140 . To facilitate decoding of the target image, the illumination LED 130 projects light on the target image through the illumination/aiming lens 150 . The position of the target image within the proper field of view of the imaging/decoding IC is obtained by projecting an aiming pattern on the target image using illumination/aiming LED 130 . The illumination/aiming LEDs are focused on the target image by the illumination/aiming lens 150 . It will be appreciated that the illumination/aiming lens 150 can be designed to scatter the light from the illumination/aiming LEDs on the target image in any known target pattern.

The volume of the imaging system is scaled by scaling the pixel width or pitch of the detector array of imaging/decoding IC 120 . It will be appreciated that pixel width or pitch refers to the spacing between image elements, such as pixels, on an image sensor. When the pixel width or pitch is reduced, the focal length is also reduced to maintain the corresponding field of view. If the aperture size is held constant, each pixel collects the same amount of light without loss of imager sensitivity. If the size of the aperture does not limit the size of the imager, then in a 2D (two-dimensional) imaging system all three-dimensional dimensions are scaled by the scaling factor of the pixels. In 1D imaging systems the two dimensions are scaled by the scaling factor of the pixels.

The imaging engine is designed to provide the same depth of focus and the same light flux per pixel. Doing so sacrifices the dynamic range of the pixel and the quantum efficiency of the pixel. The impact on pixel dynamic range is first order, but dynamic range is not very important for applications such as barcode imaging. The effect on the pixel quantum efficiency is second order for relatively large pixels, say larger than 5λ.

It will be appreciated that the light collected by the optical system from a point source is determined by:

$\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; aperture</span>}}}{{\mathrm{<span\; class="notranslate">\; \&pi;<figure-callout\; id="2"\; label="s"\; filenames="C0214693500191.png,C0214693500221.png"\; state="\{\{state\}\}">s</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

In this formula, A _aperture is the area of the aperture and S is the distance to the light source. By being uniform in the instantaneous field of view of a single pixel, the light collected by a pixel is determined by:

$\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; aperture</span>}}}{{\mathrm{<span\; class="notranslate">\; \&pi;S</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; pixelFOV</span>}}$

When the pixel pitch or width of the imaging system is reduced, the area of the aperture (A _aperture ) and the instantaneous field of view of the pixel can be kept constant while maintaining the depth of focus. This ensures that, in object space, everything such as aperture size, nominal focal length, field of view per pixel, and instantaneous field of view are the same when the size of the sensor is reduced. Thus, the imaging engine can be sized with little impact on barcode reading performance.

With the above discussion in mind, the miniaturized imager depicted in Figures 1A and 1B has 4 μm pixels and a CMOS detector array of 512 pixels. This advantageously makes the length of the small detector approximately 2mm. The focal length of the system is approximately 3mm. Accordingly, the overall dimensions of the scan engine depicted in FIGS. 1A and 1B may be on the order of 5×3×2.25 mm ³ .

A practical limit for pixel width or pitch is approximately 3 μm. In 1D systems, detector tracks can be further miniaturized by offsetting two or more rows of pixels, eg, interleaved with another row. For example, an array of 500 pixels of 3 μm pitch has a length of 1.5 mm. By arranging the array so that two adjacent rows are offset by half a pixel, the pixel width or pitch is maintained at 3 μm, but the detector array has a combined length of .75 mm. Since the array has a half-pixel offset, the pixel values can be combined to obtain a resolution equal to a 1.5µm pixel. The pixel width or pitch is maintained at a reasonable level for absorbing photons, but the footprint of the detector and thus the overall system volume can be significantly reduced.

Imaging detector arrays, readout electronics, analog-to-digital converters, and decoding logic can all be integrated into a single chip. The imaging/decoding chip is mounted on a carrier with two LED dies or small lasers. The carrier may be an FR4 substrate, which is an industry recognized organic substrate and contains lead frames or solder bumps for connection to larger circuit boards. The slide is covered with a cast plastic sheet with a clear surface cast into it. The cast plastic cover is optically superior and able to withstand the temperatures encountered in automated circuit board assemblies. The device is a complete scanner, including optomechanics and electronics, and can be handled like a surface mount integrated circuit and is compatible with reflow soldering techniques. The device depicted in Figures 1A and 1B is a complete imager that can be mechanically connected by only solder joints. Accordingly, the miniaturized imager depicted in FIGS. 1A and 1B does not require screws or any similar mechanical support, thereby reducing the size and complexity of the devices incorporating the imaging engine.

2A-2C depict top, front and side views, respectively, of another miniaturized imager. The miniaturized imager depicted in Figures 2A-2C has a very small form factor and can be operated with little or no artificial lighting suitable for very low power operation. The miniaturized imager includes an imager housing 210, which may be fabricated from any available metal or plastic material known to those skilled in the art. In imager housing 210, imager chip 220 is mounted on imaging board 230 using any of the available bonding and mounting techniques. Additionally, the imager chip 220 may be mounted on the imaging board 230 using circuit board technology. Imager chip 220 is disposed in imager housing 210 directly behind lens 240 . Lens 240 may be made of any suitable transparent material. The imager chip is housed in the dark chamber 250, which is formed in the imager housing 210, so that the imager chip 220 operates without external sealing, thereby simplifying the design of the main device, such as a camera, terminal or miniaturization computer.

To achieve contrast in the scene captured by imager chip 220, LED 260 may be provided. The LEDs 260 can be discrete or integrated into an array. Additional optics for diffusing light may be placed in the imager housing 210 for illuminating the scene, if desired. Also, to achieve contrast in the scene captured by imager chip 220, the size of the aperture may be increased. The increase in size of the aperture results in a reduction in the working range, but reduces power usage by minimizing or eliminating the need to illuminate the target image.

Another way to achieve contrast in the scene captured by the imager chip 220 is by using a low noise imager with gain or by using a logarithmic response imager. If the noise floor of the imager is below the quantization level of the analog-to-digital converter, the analog signal can be amplified to increase the contrast of the image captured with a small amount of light. Non-linear transformations such as logarithmic can be used in order to increase the contrast between dark parts of an image with little effect on bright parts. Additionally, any of the techniques described above for achieving contrast can be combined to improve the imager's response. Automatic gain control can be used to obtain a wide dynamic range of the interior scene.

It should be understood that the imager shown in Figures 2A-C may be further modified from that depicted in the Figures. It will be noted that lens 240 is not a necessary element and may be omitted and/or used with other elements. For example, the optics housing may contain one or more mirrors that direct light from the imager chip to help improve contrast in the scene. Additionally, the optical housing may contain prisms or other diffusing elements that direct light onto the imager chip. Additionally, the imager may contain a motor that inserts a plastic or optical integrity sheet between the lens and the imager to focus the lens in two different positions. To reduce the cost of the imager housing and lens, these components can be made of molded plastic. Additionally, screens used in molding can form dark chambers and lens apertures.

Accordingly, the miniaturized imager shown in Figures 2A-2C may have a small form factor, such as the SE900 form factor, with a maximum dimension of approximately 20.6 x 14.2 x 11.4 mm ³ (0.811 x 0.559 x 0.449 inches), resulting in The volume of the imager is 3.3 cm ³ (0.20 cubic inches). The SE900 form factor is the form factor used by the imager industry for producing imaging devices. Imagers contain sufficient optics and electronics to generate an analog or digital signal stream to an attached miniaturized computer or display. The imager of the imaging chip 220 can be CCD or CMOS.

Figure 3 depicts another miniaturized imager. The miniaturized imager shown in FIG. 3 includes an imager housing 310 . Inside the imager housing 310 is an image sensor 320 connected to a printed circuit board 330 . The image sensor 320 may be a CMOS image sensor. A printed circuit board is disposed near or behind the imager housing 310 . Aperture 340 is incorporated in imager housing 310 to allow image sensor 320 to capture the scene. The front surface of the imager housing 310 includes a plurality of LEDs 350 for scene illumination and aiming. It will be appreciated that the arrangement of LEDs 350 on the front surface of the imager housing can be of any known design so long as it illuminates the target and assists the user in aiming components incorporated into the imager of FIG. 3 . The dimensions of the imager of Figure 3 are approximately 20.6 x 14.2 x 11.4 mm ³ (width/depth/height), resulting in a volume of the imager of approximately 3.3 cm ³ (0.20 cubic inches). Of course, it is also possible to get smaller sizes, for example if more than 3.3 cm ³ (0.20 cubic inches) are used. Of course, it is also possible to get smaller sizes, for example if using fewer pixels or a smaller pixel width.

Figure 4 depicts the electronic components of the miniaturized imager. The imager of FIG. 4 includes a 2D area sensor 410 controlled by a clock driver and charge pump 420 . Control of the clock driver and charge pump 420 is based on signals received from the timing generator 430 . The image captured by the 2D area sensor 410 is provided to a correlated double sampling block (CDS) 440 . Since pixels do not always return to the same value when reset, correlated double sampling is used to remove the offset caused by pixels that have not yet returned to their normal reset value. Correlated double sampling thus involves capturing two values for a pixel. The first value is the pixel value of an ideal image, such as a barcode, and the second value is the pixel value after resetting. These two values are compared for each pixel to remove offsets caused by pixels that have not returned to their normal reset values. After correlated double sampling is performed, the image is passed through by weakening the AC coupling to the block DC component of the correlated double sampled image. After reducing the AC coupling, automatic gain control (AGC) 442 amplifies the signal that is then provided to analog-to-digital converter 444 . According to a preferred embodiment of the present invention, the analog-to-digital converter 444 is a 9-bit analog-to-digital converter.

Digital data is provided by analog-to-digital converter 444 to glue logic field programmable gate array (FPGA) block 450 . The glue logic/FPGA 450 compresses the digital data so that it can be read by the microprocessor 460, and the glue logic/FPGA 450 interfaces with the microprocessor 460 to provide control of all the cameras. Microprocessor 460 includes DRAM embedded on the same IC as the microprocessor, which increases the speed of the system while allowing the size and cost of the resulting imager to be reduced. Microprocessor 460 operates under the control of a program stored in Flash memory 470 via an external data and address bus.

The target image can be illuminated using an illumination module 475, which in a preferred embodiment of the invention is illuminated by a 650nm red LED. Set the LEDs so that the target image is evenly illuminated. To assist the user of the imager, an aiming module 480 may be used to provide a unique aiming pattern. Aiming module 480 may include a laser diode and diffractive optical element (DOE) to provide unique aiming patterns. Interaction between the host device incorporating the compact imager and the compact imager is provided using the host interface 490 . Since the imagers described herein are miniaturized, ie, have a small form factor, the host device may be a portable radiotelephone (cellular telephone), a personal digital assistant (PDA), or the like. Using the components described in connection with Figure 4, a miniaturized imager produced in the SE1223 form factor can be obtained. The SE1223 form factor is the form factor used by the imager industry for producing imaging devices.

The working range of an imager can be widened by positioning the image sensor at an angle that is not perpendicular to the optical axis of the focusing lens. Figure 5 depicts an imager with an extended operating range. In particular, the imager includes an image sensor 510 and a focusing lens 520 . The image sensor includes a plurality of horizontal rows of pixels facing the lens 520 . Although not shown in FIG. 5, it will be appreciated that the imager shown therein may have additional elements similar to those discussed in FIGS. 1-4.

As shown in FIG. 5 , the plane parallel to the front of the pixels of the imager 510 is inclined at an angle θ to the optical axis of the focusing lens 520 . Correspondingly, for example, one horizontal pixel row PR1 of the imager 510 is focused on a first spatial plane 1', and another horizontal pixel row PR2 is focused on a second spatial plane 2' different from the first spatial plane 1'. By placing the image sensor of the imager 510 at an angle θ that is non-perpendicular to the optical axis OA of the focusing lens 520, the imager can read and decode the distance Target images at different distances from the imager. This ability to read and decode target images at different distances reduces the hassle of having to manually adjust the distance between the imager and the target image to successfully read and decode the target image. The imager shown in Figure 5 can be used in manual or automatic mode to read 1D or 2D barcodes.

Figure 6A depicts a top view of a conventional LED. LED600 includes a bonding sheet through which power is supplied to LED600. A conventional LED, such as that shown in Figure 6A, has a square shape with dimensions approximately 350 μm x 350 μm. As shown in FIG. 6A , bond pad 610 is generally placed in the middle of LED 600 . This arrangement of bond pads 610 blocks approximately 30% of the light power emitted from LED 600 . Additionally, as discussed, conventional LEDs produce less focused light than lasers, which results in an increased linewidth of the projected light.

Figures 6B-6E depict three different embodiments of novel LEDs. Typically, novel LEDs have nearly the same modal area as conventional LEDs, thereby maintaining substantially the same emitted power as conventional LEDs. However, the novel LEDs are thinned in the focusing direction, ie, the direction that produces the linewidth, and elongated in the other direction. Referring now to FIG. 6B , LED 615 has a square portion 620 and an elongated rectangular portion 625 . More broadly and in other words, the novel LED has at least a main portion with a bond pad and an elongated portion extending from the main portion. It is not necessary for the main part to be square and the elongated part to be rectangular; for example, the corners of the embodiment of FIG. 6B could be rounded. Referring again to FIG. 6B , the square portion 620 has a bonding tab 630 . As represented in FIG. 6B , LED 620 has dimensions D _x x D _y , where D _y is the width of elongated portion 625 . Since the voltage to drive the LED is provided through the bond pad, the light power emitted from the LED is reduced, so the rest of the LED comes from the bond pad. Thus, the amount of optical power emitted from elongated portion 625 is reduced for the portion to the right of bond pad 630 in FIG. 6B .

Figure 6C depicts a top view of another novel LED. In particular, LED 635 has two square portions 640 and 647 connected by rectangular portion 642 . Square portion 640 has bond pad 645 thereon, and square portion 647 has bond pad 650 thereon. By placing bond pads 645 and 650 on each side of the rectangular portion 642, a more uniform amount of light power emitted from the rectangular portion can be obtained compared to the LED 615 shown in FIG. 6B.

Figure 6D depicts a top view of yet another novel LED. A bond pad 670 is placed adjacent to the rectangular portion of the LED 655 .

Therefore, the bond pad 670 does not block any light emitted from the elongated portion. In addition, the placement of the bonding pad in FIG. 6D ensures a more uniform distribution of light emitted from the center of the rectangular portion of the LED die 655, whereas the placement of the bonding pad in FIG.

Figure 6E depicts a top view of yet another novel LED. All sides of the rectangular portion 680 of the LED die 675 are surrounded by the bond pad 685 . By surrounding the rectangular portion 680 of the LED die 675 with a bond pad 685, a uniformly distributed light emission from the entire rectangular portion 680 of the LED die 675 is obtained as compared to the LED die shown in FIGS. 6B-6D. According to an embodiment of the present invention, D _y in FIGS. 6B-6D is less than or equal to 50um. In order to maintain the same emission power as conventional LEDs, _Dx in Figures 6B-6E is chosen so that the LEDs have the same modal area as conventional LEDs.

Fig. 7 is a schematic diagram of a semiconductor device 1 for imaging optical code symbols, in particular barcode symbols, according to the invention. The semiconductor device may find preferred application as a sensor application for field-of-view imaging of a bar code reader, and may be used with some or all of the elements described above, such as miniaturized imagers, or with LEDs, etc. as described above.

The semiconductor device 1 includes not more than 1024 pixels 2 . Preferably, the number of pixels is between 256 and 1024. A preferred embodiment may include, for example, 512 pixels. Each pixel 2 has an aspect ratio exceeding 2:1, and its short dimension is not larger than 4 μm and not smaller than 2 μm. While it is generally possible to arrange pixels, for example by interleaving rows of pixels with half pixels relative to each other as described above, it is preferable to arrange pixels in a single row as shown in FIG. 7 . As is clear from FIG. 7, the long dimension of the pixels is arranged perpendicular to the rows, while the rows formed with the short-sized pixels are arranged adjacent to each other. Pixel aspect ratios in excess of 2:1 will provide superior results for semiconductor devices used to read bar code symbols because the bars and spaces between the bar code symbols can be well discerned despite the small size of the semiconductor devices.

A semiconductor device as described above can be fabricated into a sensor for imaging a field of view in a barcode reader. Such sensors are extremely small, but still capable of reliably imaging barcode symbols. Since a single semiconductor device of the present invention is sufficient for imaging barcode symbols, the sensor (and thus the barcode reader) can be exceptionally small, particularly useful in portable and/or miniaturized barcode reader applications.

Claims (13)

1. A semiconductor device for imaging optical code symbols, comprising: a chip with no more than 1024 pixels, wherein each pixel has a long dimension, a short dimension and an aspect ratio greater than 2:1, each pixel The short dimension is not more than 4 μm and not less than 2 μm. 2. A device as defined in claim 1, wherein the pixels are arranged in a single row. 3. The device defined in claim 1, wherein the number of pixels is not less than 256 pixels. 4. A device as defined in claim 2, wherein the long dimension of each pixel is perpendicular to the row. 5. The device as defined in claim 1, further comprising a package supporting the chip, the package occupying a volume not exceeding 3.3 cubic centimeters. 6. The device defined in claim 5, wherein said volume measures approximately 20.6 mm x 14.2 mm x 11.4 mm. 7. A bar code reader for reading a symbol having bars spaced apart along a longitudinal direction, each bar extending lengthwise in a transverse direction perpendicular to the longitudinal direction, the bar code reader comprising: A sensor for imaging the field of view of a reader, the sensor comprising a single semiconductor chip of not more than 1024 pixels, wherein each pixel has a long dimension, a short dimension and an aspect ratio greater than 2:1, and the short dimension of each pixel is not greater than 4 μm Not less than 2 μm. 8. A reader as defined in claim 7, wherein the long dimension of each pixel extends along the length of the bar in the symbol. 9. A reader as defined in claim 7, wherein the pixels are arranged in a single row. 10. The reader as defined in claim 7, wherein the number of pixels is not less than 256 pixels. 11. The reader as defined in claim 9, wherein the long dimension of each pixel is perpendicular to the row. 12. The reader as defined in claim 7, further comprising a package supporting the chip, the package occupying a volume not exceeding 3.3 cubic centimeters. 13. A reader as defined in claim 12, wherein the volume measures approximately 20.6mm x 14.2mm x 11.4mm.

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