Patent Publication Number: US-8978981-B2

Title: Imaging apparatus having imaging lens

Description:
FIELD OF THE INVENTION 
     The present invention relates, in general, to registers and specifically to optical based registers. 
     BACKGROUND OF THE INVENTION 
     Indicia reading terminals for reading decodable indicia are available in multiple varieties. For example, minimally featured indicia reading terminals devoid of a keyboard and display are common in point of sale applications. Indicia reading terminals devoid of a keyboard and display are available in the recognizable gun style form factor having a handle and trigger button (trigger) that can be actuated by an index finger. Indicia reading terminals having keyboards and displays are also available. Keyboard and display equipped indicia reading terminals are commonly used in shipping and warehouse applications, and are available in form factors incorporating a display and keyboard. A display and keyboard combination can be provided by a touch screen. In a keyboard and display equipped indicia reading terminal, a trigger button for actuating the output of decoded messages is typically provided in such locations as to enable actuation by a thumb of an operator. Indicia reading terminals in a form devoid of a keyboard and display or in a keyboard and display equipped form are commonly used in a variety of data collection applications including point of sale applications, shipping applications, warehousing applications, security check point applications, and patient care applications, and personal use, common where keyboard and display equipped indicia reading terminal is provided by a personal mobile telephone having indicia reading functionality. Some indicia reading terminals are adapted to read bar code symbols including one or more of one dimensional (1D) bar codes, stacked 1D bar codes, and two dimensional (2D) bar codes. Other indicia reading terminals are adapted to read OCR characters while still other indicia reading terminals are equipped to read both bar code symbols and OCR characters. In one commercially available indicia reading terminal, a feature for reduction of chromatic aberration includes an aspherical lens. Indicia reading terminals that comprise image sensor arrays can be regarded as imaging apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features described herein can be better understood with reference to the drawings described below. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. 
         FIG. 1  is a block diagram of an apparatus for use in decoding a bar code symbol, the apparatus having multiple elements supported on a common printed circuit board, in accordance with an aspect of the invention; 
         FIG. 2  is an exploded assembly perspective view of an imaging module, in accordance with an aspect of the invention; 
         FIG. 3  is a perspective view of an imaging module, in accordance with an aspect of the invention; 
         FIG. 4  is an emission profile of a “white light” light source that emits light spanning a range of visible color emission wavelength bands; 
         FIG. 5  is a pass band profile of an exemplary triple band pass filter that passes light in three separate transmission pass bands (one blue, one green, one red) in the visible color spectrum; 
         FIG. 6  is a diagram of an imaging system having an imaging lens designed according to a four configuration method; 
         FIGS. 7-9  are through focus MTF plots in three wave bands illustrating characteristics of an imaging lens designed according to a four configuration method; 
         FIG. 10  is a diagram of a system having an imaging lens designed according to a single configuration method; 
         FIGS. 11-13  are through focus MTF plots in three wavelength bands in an imaging lens designed according to a single configuration method; 
         FIG. 14  is a timing diagram illustrating operation of an imaging apparatus; 
         FIG. 15  is a physical form view of an imaging apparatus. 
     
    
    
     SUMMARY OF THE INVENTION 
     There is set forth herein in one embodiment an imaging apparatus having an imaging assembly and an illumination assembly. The imaging assembly can comprise an imaging lens and an image sensor array. The illumination assembly can include a light source bank having one or more light source. The imaging assembly can define a field of view on a substrate and the illumination assembly can project light within the field of view. The imaging apparatus can be configured so that the illumination assembly during an exposure period of the imaging assembly emits light that spans multiple visible color wavelength bands. 
     DETAILED DESCRIPTION OF THE INVENTION 
     There is set forth herein in one embodiment an imaging apparatus having an imaging assembly and an illumination assembly. The imaging assembly can comprise an imaging lens and an image sensor array. The illumination assembly can include a light source bank having one or more light source. The imaging assembly can define a field of view on a substrate and the illumination assembly can project light within the field of view. The imaging apparatus can be configured so that the illumination assembly during an exposure period of the imaging assembly energizes one or more light source of the illumination assembly so that the illumination assembly emits light that spans multiple visible color wavelength bands (e.g., the blue, green and red wavelength bands). 
     An exemplary hardware platform for support of operations described herein with reference to an imaging apparatus  1000  as set forth in connection with  FIG. 1 . 
     Imaging apparatus  1000  can include a housing  1014  indicated by the dashed line of  FIG. 1 . Apparatus  1000  can include an image sensor  1032  comprising a multiple pixel image sensor array  1033  having pixels arranged in rows and columns of pixels, associated column circuitry  1034  and row circuitry  1035 . Associated with the image sensor  1032  can be amplifier or gain circuitry  1036  (amplifier), and an analog to digital converter  1037  which converts image information in the form of analog signals read out of image sensor array  1033  into image information in the form of digital signals. Image sensor  1032  can also have an associated timing and control circuit  1038  for use in controlling e.g., the exposure period of image sensor  1032 , gain applied to the amplifier  1036 . The noted circuit components  1032 ,  1036 ,  1037 , and  1038  can be packaged into a common image sensor integrated circuit  1040 . Image sensor integrated circuit  1040  can incorporate fewer than the noted number of components. In one example, image sensor integrated circuit  1040  can incorporate a Bayer pattern filter, so that defined at the image sensor array  1033  are red pixels at red pixel positions, green pixels at green pixel positions, and blue pixels at blue pixel positions. Frames that are provided utilizing such an image sensor array incorporating a Bayer pattern can include red pixel values at red pixel positions, green pixel values at green pixel positions, and blue pixel values at blue pixel positions. In an embodiment incorporating a Bayer pattern image sensor array, CPU  1060  prior to subjecting a frame to further processing can interpolate pixel values at frame pixel positions intermediate of green pixel positions utilizing green pixel values for development of a monochrome frame of image data. Alternatively, CPU  1060  prior to subjecting a frame for further processing can interpolate pixel values intermediate of red pixel positions utilizing red pixel values for development of a monochrome frame of image data. CPU  1060  can alternatively, prior to subjecting a frame for further processing interpolate pixel values intermediate of blue pixel positions utilizing blue pixel values. An imaging assembly of apparatus  1000  can include image sensor  1032  and a lens assembly  200  for focusing an image onto image sensor array  1033  of image sensor  1032 . In one example, image sensor array  1003  can be a hybrid monochrome and color image sensor array having a first subset of monochrome pixels without color filter elements and a second subset of color pixels having color sensitive filter elements. 
     In the course of operation of apparatus  1000 , image signals can be read out of image sensor  1032 , converted, and stored into a system memory such as RAM  1080 . A memory  1085  of apparatus  1000  can include RAM  1080 , a nonvolatile memory such as EPROM  1082  and a storage memory device  1084  such as may be provided by a flash memory or a hard drive memory. In one embodiment, apparatus  1000  can include CPU  1060  which can be adapted to read out image data stored in memory  1080  and subject such image data to various image processing algorithms. Apparatus  1000  can include a direct memory access unit (DMA)  1070  for routing image information read out from image sensor  1032  that has been subject to conversion to RAM  1080 . In another embodiment, apparatus  1000  can employ a system bus providing for bus arbitration mechanism (e.g., a PCI bus) thus eliminating the need for a central DMA controller. A skilled artisan would appreciate that other embodiments of the system bus architecture and/or direct memory access components providing for efficient data transfer between the image sensor  1032  and RAM  1080  can be utilized. 
     Referring to further aspects of apparatus  1000 , imaging lens assembly  200  can be adapted for focusing an image of a decodable indicia  15  located within a field of view  1240  on a substrate, T, onto image sensor array  1033 . Imaging lens assembly  200  in combination with image sensor array  1033  can define a field of view  1240  on a substrate T. 
     Apparatus  1000  can include an illumination assembly  800  for illumination of target, T, and projection of an illumination pattern  1260 . Illumination pattern  1260 , in the embodiment shown can be projected to be proximate to but larger than an area defined by field of view  1240 , but can also be projected in an area smaller than an area defined by a field of view  1240 . Illumination assembly  800  can include a light source bank  500 , comprising one or more light sources. The apparatus  1000  may be configured so that the light from light source bank  500  is directed toward a field of view  1240 . In one embodiment, illumination assembly  800  can include, in addition to light source bank  500 , illumination light shaping optics  300 , as is shown in the embodiment of  FIG. 1 . In light shaping optics  300  can include, e.g., one or more diffusers, mirrors and prisms. In use, apparatus  1000  can be oriented by an operator with respect to a target, T, (e.g., a piece of paper, a package, another type of substrate) bearing decodable indicia  15  in such manner that illumination pattern  1260  is projected on a decodable indicia  15 . In the example of  FIG. 1 , decodable indicia  15  is provided by a 1D bar code symbol. Decodable indicia  15  could also be provided by a 2D bar code symbol or optical character recognition (OCR) characters. 
     In one embodiment light source bank  500  can project light in first narrow wavelength band. In one embodiment light source bank  500  can project light in a first narrow wavelength band and a second narrow wavelength band. In one embodiment light source bank  500  can project light in first narrow wavelength band, a second narrow wavelength band, and a third narrow wavelength band. In one embodiment, light source bank  500  can project light in N narrow wavelength bands wherein N is greater or equal to 1. In one embodiment, light source bank  500  includes one or more light source that emits “white” light that spans multiple visible wavelength bands. In one example, the one or more light source can be an LUW CP7P-KTLP-5E8G-35 light source of the type available from OSRAM Opto Semiconductors GmbH. 
     A physical form view of an example of an illumination assembly is shown in  FIGS. 2-3 . As shown in  FIGS. 2-3 , an imaging module  400  can be provided having a circuit board  402  carrying image sensor  1032  and lens assembly  200  disposed in support  430  disposed on circuit board  402 . In the embodiment of  FIGS. 2 and 3 , illumination assembly  800  has a light source bank  500  provided by first light source  502 , second light source  504  and third light source  506 . Each light source  502 ,  504 ,  506  can be provided e.g., by an LED. In one embodiment, each light source  502 ,  504 ,  506  can emit “white light,” e.g., light that includes emissions spanning the blue, green and red wavelength bands. In one embodiment, each light source  502 ,  504 ,  506  can emit light in a different narrow wavelength band. In one embodiment first light source  502  can emit narrow band light in the red wavelength band, second light source  504  can emit narrow band light in the green wavelength band and third light source  506  can emit narrow band light in blue wavelength band. The light sources  502 ,  504 ,  506  can be simultaneously energized to emit white light. Whether illumination assembly  800  includes one or more white light sources or one or more narrow band light source illumination assembly  800  during an exposure period can simultaneously project on a target light within the blue wavelength band, the green wavelength band and the red wavelength band. Illumination assembly  800  can further include a light shaping optics optical element  302 ,  304 ,  306  associated with each light source  502 ,  504 ,  506 . Light shaping elements  302 ,  304 ,  306  can define light shaping optics  300  of illumination assembly  800 . Light shaping elements  302 ,  304 ,  306  can be formed on optical plate  310  forming part of imaging module  400 . 
     The apparatus  1000  can be adapted so that light from each of a one or more light source  502  of light source bank  500  e.g., light source  502 ,  504 ,  506  is directed toward field of view  1240  and utilized for projection of illumination pattern  1240 . Each of the one or more light source  502 ,  504 ,  506  can include an emission profile as set forth in  FIG. 4 . Each light source, as indicated in  FIG. 4 , can emit light within the blue wavelength band, the green wavelength band, and the red wavelength band. 
     In another aspect apparatus  1000  can include band pass filter  250 . In one embodiment, band pass filter  250  can be a triple band pass filter that selectively passes narrow band light within discrete narrow band wavelengths. In one embodiment, band pass filter  250  can have a transmission profile as set forth in  FIG. 5  having a first pass band passing blue light, a second pass band passing green light and a third pass band passing red light. The filter as set forth in  FIG. 5  can selectively transmit light within the blue wavelength band, can selectively transmit light within the green wavelength band and can selectively transmit light within the red wavelength band. In the embodiment as described with reference to  FIG. 5 , the pass bands can be separated, e.g., “gaps” in the pass bands can be present between about 480 nm and 515 nm and between about 560 nm and 590 nm. In the embodiment described with reference to  FIG. 5 , light at wavelengths shorter than the first pass band are blocked (attenuated). Light at wavelengths longer than the third pass band is also blocked (attenuated). 
     In another aspect, apparatus  1000  can include an aperture stop  270  defining an aperture  272 . Aperture  272  can be a relative small aperture having an F# in the range of 8.0≦F#≦9.0. In one embodiment, an F# of aperture  272  is equal to or greater than 6.0. In one embodiment an F# of aperture  272  is equal to or greater than 7.0. In one embodiment, an F# of aperture  272  is equal to or greater than 8.0. An imaging system  900  of apparatus  1000  can include imaging lenses  200 , aperture stop  270 , band filter  230  and image sensor array  250 . 
     Because of chromatic aberrations, best focus points for different wavelengths can diminish an optical performance of lens assembly  200  and can decrease a signal to noise ratio (SNR) imaging lenses  200  can be designed so that chromatic aberrations are reduced. In one embodiment, merit functions are defined to optimize wavefront aberrations to find a solution. In one embodiment, four configurations are established. Three narrow wave bands (R, G, B) are defined in three configurations, respectively. The primary wavelengths of three bands are defined in the fourth configuration. Merit functions are defined in these four configurations to seek the optimized solution for the three wave bands. An advantage of the solution is to provide improved optical performance (MTF, DOF) in three working spectrum bands. Another advantage is to maximize the SNR on the sensor with the triple bandpass applied in the lens system. 
     Further aspects of imaging lens  200  are now described. In one embodiment, imaging lens  200  can be a well corrected imaging lens well corrected for chromatic aberration. 
     Various approaches have been implemented for achieving chromatic correction. Imaging lenses having more than three elements have been proposed. Also, lens elements having aspherical surfaces have been proposed. Also, hybrid lenses have been proposed having more than one material type. Such approaches are advantageous in certain applications. 
     An example of a method for design of a particular well corrected lens is set forth in Example 1. 
     EXAMPLE 1 
     For design of an imaging lens, four configurations are defined. In configuration #1, wavelengths are defined as (0.440 um, 0.455 um, 0.470 um), which matches the blue band of the triple-band filter as described in connection with  FIG. 5 . In configuration #2, wavelengths are defined as (0.520 um, 0.540 um, 0.560 um) for matching the green band. In configuration #3, wavelengths are defined as (0.600 um, 0.650 um, 0.700 um) for matching the red band. In configuration #4, wavelengths are defined as (0.455 um, 0.540 um, 0.650 um), which are the center wavelengths of three narrow wavelength bands. Merit functions are then established in four configurations to seek the optimized solution for the three wave bands. According to the method set forth in Example 1, optical performance in three wavelength bands is improved to increase the signal to noise ratio (SNR) of a signal output by image sensor array  1033  implemented in apparatus  1000  having triple band pass filter  250 . With the four configuration approach set forth in Example 1, first, second and third configurations are defined to match first, second and third narrow bands, a fourth configuration is defined by the respective center wavelengths of the three narrow bands, and merit functions are established in the four configurations to identify an optimized solution for the four configurations. 
     Lens specifications of one embodiment in accordance with Example 1, are as follows: 
     Lens Specifications: 
     
         
         
           
             1. EFL: 8.4 mm 
             2. FOV: 12.2°×15.8° 
             3. Focus distance: 9.4″ 
             4. Image size: 6.2 mm diagonal 
           
         
       
    
     An imaging lens  200  in one embodiment in accordance with Example 1 is implemented as a two element glass lens as shown in  FIG. 6 . The two element glass lens as shown in  FIG. 6  can have first lens element  202  and second lens element  204 . Where imaging lens  200  is provided by a two element lens, imaging lens  200  is devoid of lens elements other than first and second lens elements. Lens specification and prescription data set forth herein are based on simultaneous utilizing ZEMAX optical design simulations software. 
     A prescription for imaging lens  200  in accordance with Example 1 is presented in Table 1. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Surface: Type 
                 Comment 
                 Radius 
                 Thickness 
                 Glass 
                 Semi-Diameter 
                 Nd 
                 Vd 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Standard 
                 Object location 
                 Infinity 
                 236.000 
                   
                 85.340 
                   
                   
               
               
                 1 
                 Standard 
                 S1 of E1 
                 1.909 
                 1.560 
                 H-FK61 
                 1.600 
                 1.496998 
                 81.5947 
               
               
                 2 
                 Standard 
                 S2 of E1 
                 2.021 
                 0.120 
                   
                 1.250 
               
               
                 Stop 3 
                 Standard 
                 Aperture 
                 Infinity 
                 0.050 
                   
                 0.308 
               
               
                 4 
                 Standard 
                   
                 Infinity 
                 1.780 
                   
                 0.334 
               
               
                 5 
                 Standard 
                 S1 of E2 
                 5.340 
                 0.990 
                 H-ZLAF1 
                 1.600 
                 1.801663 
                 44.2823 
               
               
                 6 
                 Standard 
                 S2 of E2 
                 8.234 
                 0.200 
                   
                 1.600 
               
               
                 7 
                 Standard 
                 Filter 
                 Infinity 
                 0.300 
                 SCHOTT_D263 
                 2.150 
               
               
                 8 
                 Standard 
                   
                 Infinity 
                 2.600 
                   
                 2.150 
               
               
                 9 
                 Standard 
                 Cover on Sensor 
                 Infinity 
                 0.550 
                 SCHOTT_D263 
                 2.578 
               
               
                 10  
                 Standard 
                   
                 Infinity 
                 0.780 
                   
                 2.717 
               
               
                 11  
                 Standard 
                 Sensor location 
                 Infinity 
                 0.000 
                   
                 3.050 
               
               
                   
               
               
                 Nd is refractive index of glass; 
               
               
                 Vd is V number of glass 
               
            
           
         
       
     
       FIG. 7  (blue),  FIG. 8  (green) and  FIG. 9  (red) are through focus MTF plots in three wave bands. By the approach set forth herein, the best focus difference between blue and red light is 0.15 mm, and the ratio of chromatic aberration to effective focal length is 0.018. The chromatic aberration is much improved. Meanwhile, compared to a design having aspherical lens surfaces, the design in accordance with Example 1 alleviates performance degradation in an off-axis area. 
     Results set forth by application of the four configuration method set forth with reference to Example 1 are compared to an alternative system in which a two element glass imaging lens design is provided by building merit functions in a single configuration and the optimization process is driven to search a local minimum point. An alternative lens design can be provided by defining visible wavelengths as (0.486 um, 0.587 um, 0.656 um), and a primary wavelength as 0.587 um (green light). Merit functions in a comparison alternative system can be built in one configuration and drive optimization process to search a local minimum point. More particularly, with a one configuration approach an imaging lens design is optimized for a single broad band configuration. With the one configuration approach, a configuration is defined to match a single broad band and merit functions are established in the broad band to identify an optimized solution for the one configuration. A resulting solution has the best focus for the primary wavelength (green light). Due to the chromatic aberration, the best focus points of red light and blue light are away from the green focus point. The blue light focus before the green light, and the red light focus after the green light. The amount of chromatic aberration can be measured by the separation of the best focus points of blue and red light. With a two elements system designed by the single configuration approach, the focus difference of blue light and red light is 0.23 mm. The ratio of chromatic aberration to effective focal length is 0.027. A diagram of a two element glass imaging lens having first lens element  206  and second lens element  208  designed according to a one configuration approach is shown in  FIG. 10 . Imaging lens  200  as shown in  FIG. 10  has a first glass lens element  202  and a second glass lens element  204 . A prescription for a comparison two element glass design using the single configuration approach is set forth in Table 2. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Surface: Type 
                 Comment 
                 Radius 
                 Thickness 
                 Glass 
                 Semi-Diameter 
                 Nd 
                 Vd 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 OBJ 
                 Standard 
                 Object location 
                 Infinity 
                 236.000 
                   
                 85.628 
                   
                   
               
               
                 1 
                 Standard 
                 S1 of E1 
                 3.078 
                 2.260 
                 H-LAK53A 
                 1.875 
                 1.755002 
                 52.3293 
               
               
                 2 
                 Standard 
                 S2 of E1 
                 2.849 
                 0.270 
                   
                 1.200 
               
               
                 Stop 3 
                 Standard 
                 Aperture 
                 Infinity 
                 0.050 
                   
                 0.292 
               
               
                 4 
                 Standard 
                   
                 Infinity 
                 1.450 
                   
                 0.323 
               
               
                 5 
                 Standard 
                 S1 of E2 
                 8.867 
                 1.130 
                 H-ZLAF3 
                 1.875 
                 1.855449 
                 36.5981 
               
               
                 6 
                 Standard 
                 S2 of E2 
                 Infinity 
                 0.200 
                   
                 1.875 
               
               
                 7 
                 Standard 
                 Filter 
                 Infinity 
                 0.300 
                 BK7 
                 2.150 
               
               
                 8 
                 Standard 
                   
                 Infinity 
                 3.000 
                   
                 2.150 
               
               
                 9 
                 Standard 
                 Cover on Sensor 
                 Infinity 
                 0.550 
                 BK7 
                 2.840 
               
               
                 10  
                 Standard 
                   
                 Infinity 
                 0.629 
                   
                 2.980 
               
               
                 11  
                 Standard 
                 Sensor location 
                 Infinity 
                 0.000 
                   
                 3.090 
               
               
                   
               
               
                 Nd is refractive index of glass; 
               
               
                 Vd is V number of glass 
               
            
           
         
       
     
     MTF plots in three bands for an imaging lens designed according to the signal configuration approach are set forth in  FIG. 11  (blue),  FIG. 12  (green) and  FIG. 13  (red). By comparison of Table 2 and Table 1 it is seen that an imaging lens designed according to the four configuration design approach as compared to imaging lens designed according to the one configuration design approach features a first lens element including light entry and exit surfaces of increased curvature, a second lens element including light entry and exit surfaces of increased curvature, a first lens element having a reduced index of refraction and increased V number, and a second lens element having a reduced index of refraction and increased V number. There is set forth herein a method for reducing chromatic aberrations of an imaging lens having first and second lens elements, the method comprising two or more of (a) through (h); (a) increasing a curvature of a light entry; (b) increasing a curvature of a light exit surface of the first lens element; (c) increasing a curvature of a light entry surface of the second lens element; (d) increasing a curvature of a light exit surface of the second lens element; (e) decreasing an index of refraction of the first lens element; (f) decreasing an index of refraction of the second lens element; (g) increasing a V number of the first lens element; (h) increasing a V number of the second lens element. 
     By comparison as set forth herein, a two element glass lens provided in accordance with the method of Example 1 has a focus difference of blue light and red light of 0.15 mm and a ratio of chromatic aberration of 0.018. In one embodiment, an imaging lens can have a ratio of chromatic aberration to effective focal length of less than 0.025. In one embodiment, an imaging lens can have a ratio of chromatic aberration to effective focal length of less than 0.024. In one embodiment, an imaging lens can have a ratio of chromatic aberration to effective focal length of less than 0.023. In one embodiment, an imaging lens can have a ratio of chromatic aberration to effective focal length of less than 0.022. In one embodiment, an imaging lens can have a ratio of chromatic aberration to effective focal length of less than 0.021. In one embodiment, an imaging lens can have a ratio of chromatic aberration to effective focal length of less than 0.020. 
     In one aspect of the imaging lens  200  as set forth in  FIG. 6  each lens surface of first lens element  202  and second lens element  204  are spherical. By making each lens surface spherical, cost is reduced and performance degradation in off-axis areas can be reduced. The selection of glass (as opposed to polymer based materials) can optimize performance for the reason that glass elements are available in a wider range of refractive indices and V numbers, and/or can be fabricated accorded to specification more precisely to a certain index of refraction or V number. In some applications polymer based lens materials are preferred. With a design as set forth herein, excellent chromatic aberration correction can be achieved with a two element design which in one embodiment can be a two element glass imaging lens. The design set forth herein facilitates use of a two element glass lens in an imaging apparatus having an image sensor array with color sensitive pixels. 
     Referring to further aspects of apparatus  1000 , light source bank electrical power input unit  1206  can provide energy to light source bank  500 . In one embodiment, electrical power input unit  1206  can operate as a controlled voltage source. In another embodiment, electrical power input unit  1206  can operate as a controlled current source. In another embodiment electrical power input unit  1206  can operate as a combined controlled voltage and controlled current source. Electrical power input unit  1206  can change a level of electrical power provided to (energization level of) light source bank  500 , e.g., for changing a level of illumination output by light source bank  500  of illumination assembly  800  for generating illumination pattern  1260 . 
     In another aspect, apparatus  1000  can include power supply  1402  that supplies power to a power grid  1404  to which electrical components of apparatus  1000  can be connected. Power supply  1402  can be coupled to various power sources, e.g., a battery  1406 , a serial interface  1408  (e.g., USB, RS232), and/or AC/DC transformer  1410 ). 
     Further regarding power input unit  1206 , power input unit  1206  can include a charging capacitor that is continually charged by power supply  1402 . 
     Apparatus  1000  can also include a number of peripheral devices including trigger  1220  which may be used to make active a trigger signal for activating frame readout and/or certain decoding processes. Apparatus  1000  can be adapted so that activation of trigger  1220  activates a trigger signal and initiates a decode attempt. Specifically, apparatus  1000  can be operative so that in response to activation of a trigger signal, a succession of frames can be captured by way of read out of image information from image sensor array  1033  (typically in the form of analog signals) and then storage of the image information after conversion into memory  1080  (which can buffer one or more of the succession of frames at a given time). CPU  1060  can be operative to subject one or more of the succession of frames to a decode attempt. 
     For attempting to decode a bar code symbol, e.g., a one dimensional bar code symbol, CPU  1060  can process image data of a frame corresponding to a line of pixel positions (e.g., a row, a column, or a diagonal set of pixel positions) to determine a spatial pattern of dark and light cells and can convert each light and dark cell pattern determined into a character or character string via table lookup. Where a decodable indicia representation is a 2D bar code symbology, a decode attempt can comprise the steps of locating a finder pattern using a feature detection algorithm, locating matrix lines intersecting the finder pattern according to a predetermined relationship with the finder pattern, determining a pattern of dark and light cells along the matrix lines, and converting each light pattern into a character or character string via table lookup. CPU  1060 , which, as noted, can be operative in performing processing for attempting to decode decodable indicia, can be incorporated in an integrated circuit  2060  disposed on circuit board  402  (shown in  FIGS. 2 and 3 ). 
     Apparatus  1000  can include various interface circuits for coupling various of the peripheral devices to system address/data bus (system bus)  1500 , for communication with CPU  1060  also coupled to system bus  1500 . Apparatus  1000  can include interface circuit  1028  for coupling image sensor timing and control circuit  1038  to system bus  1500 , interface circuit  1102  for coupling electrical power input unit  1202  to system bus  1500 , interface circuit  1106  for coupling illumination light source bank power input unit  1206  to system bus  1500 , and interface circuit  1120  for coupling trigger  1220  to system bus  1500 . Apparatus  1000  can also include a display  1222  coupled to system bus  1500  and in communication with CPU  1060 , via interface  1122 , as well as pointer mechanism  1224  in communication with CPU  1060  via interface  1124  connected to system bus  1500 . Apparatus  1000  can also include range detector unit  1210  coupled to system bus  1500  via interface  1110 . In one embodiment, range detector unit  1210  can be an acoustic range detector unit. Apparatus  1000  can also include a keyboard  1226  coupled to system bus  1500  via interface  1126 . Various interface circuits of apparatus  1000  can share circuit components. For example, a common microcontroller can be established for providing control inputs to both image sensor timing and control circuit  1038  and to power input unit  1206 . A common microcontroller providing control inputs to circuit  1038  and to power input unit  1206  can be provided to coordinate timing between image sensor array controls and illumination assembly controls. Apparatus  1000  may include a network communication interface  1252  coupled to system bus  1500  and in communication with CPU  1060 , via interface  1152 . Network communication interface  1252  may be configured to communicate with an external computer through a network. 
     A succession of frames of image data that can be captured and subject to the described processing can be full frames (including pixel values corresponding to each pixel of image sensor array  1033  or a maximum number of pixels read out from image sensor array  1033  during operation of apparatus  1000 ). A succession of frames of image data that can be captured and subject to the described processing can also be “windowed frames” comprising pixel values corresponding to less than a full frame of pixels of image sensor array  1033 . A succession of frames of image data that can be captured and subject to the described processing can also comprise a combination of full frames and windowed frames. A full frame can be read out for capture by selectively addressing pixels of image sensor  1032  having image sensor array  1033  corresponding to the full frame. A windowed frame can be read out for capture by selectively addressing pixels of image sensor  1032  having image sensor array  1033  corresponding to the windowed frame. In one embodiment, a number of pixels subject to addressing and read out determine a picture size of a frame. Accordingly, a full frame can be regarded as having a first relatively larger picture size and a windowed frame can be regarded as having a relatively smaller picture size relative to a picture size of a full frame. A picture size of a windowed frame can vary depending on the number of pixels subject to addressing and readout for capture of a windowed frame. 
     Apparatus  1000  can capture frames of image data at a rate known as a frame rate. A typical frame rate is 60 frames per second (FPS) which translates to a frame time (frame period) of 16.6 ms. Another typical frame rate is 30 frames per second (FPS) which translates to a frame time (frame period) of 33.3 ms per frame. A frame rate of apparatus  1000  can be increased (and frame time decreased) by decreasing of a frame picture size. 
     Referring to the timing diagram of  FIG. 14 , signal  5504  is a trigger signal which can be made active by actuation of trigger  1220 , and which can be deactivated by releasing of trigger  1220 . A trigger signal can also become inactive after a time out period or after a successful decode of a decodable indicia. Signal  5510  is a frame exposure signal. Logic high periods of signal  5510  define frame exposure periods  5320 ,  5322 ,  5324 ,  5326 ,  5328 . Signal  5512  is a read out signal. Logic high periods of signal  5512  define read out periods  5420 ,  5422 ,  5424 ,  5426 ,  5428 . Processing periods  5520 ,  5522 ,  5524 ,  5526 ,  5528  can represent processing periods during which time CPU  1060  of imaging apparatus  1000  processes stored (e.g., buffered) frames representing a substrate that can bear decodable indicia. Such processing can include processing for attempting to decode a decodable indicia as described herein. 
     With further reference to the timing diagram of  FIG. 14 , an operator at time, t 0 , can activate trigger signal  5504  (e.g., by depression of trigger  1120 ). In response to trigger signal  5504  being activated, apparatus  1000  can expose a succession of frames. During each frame exposure period  5320 ,  5322 ,  5324 ,  5326 ,  5238  a frame of image data can be exposed. 
     Referring further to the timing diagram of  FIG. 14 , signal  5508  is a light pattern control signal. Logic high periods of signal  5508 , namely periods  5220 ,  5222 ,  5224 ,  5226 ,  5228  define “on” periods for projected illumination pattern  1260 . A light source bank  500  of illumination assembly  8000  can be energized to project illumination pattern  1260  during illumination periods  5220 ,  5222 ,  5224  that overlap frame exposure periods  5320 ,  5322 ,  5324  so that at least a portion of an illumination period occurs during an associated frame exposure period and further that a portion of a frame exposure period occurs during an associated illumination period. At time t 1 , trigger signal  5504  can be deactivated e.g., responsively to a successful decode, a timeout condition being satisfied, or a release of trigger  1120 . Regarding illumination periods  5220 ,  5222 ,  5224 ,  5226 ,  5228 , the illustrated on times in one embodiment can be “continuously on” on times. The illustrated on times in another embodiment can be strobed on times wherein light source bank  1204  is turned on and off rapidly during an illumination period. In one embodiment, two of light sources  502 ,  504 ,  506  are simultaneously energized during each illumination period  5220 ,  5222 ,  5224 ,  5226 ,  5228 . In another embodiment, three of light sources  502 ,  504 ,  506  are simultaneously energized during illumination periods  5220 ,  5222 ,  5224 . 
     Referring Now to  FIG. 15 , an example apparatus  1000  is shown. Specifically, apparatus  1000  can have a housing  1014 , which as shown in  FIG. 15 , may be a hand held housing. Housing  1014  is configured to encapsulate image sensor integrated circuit  1040  (shown in  FIG. 15 ). A microprocessor integrated circuit  1060  having a CPU for attempting to decode decodable indicia can be disposed on circuit board  402  (shown in  FIG. 15 ). Such microprocessor integrated circuit  1060  can be disposed externally to circuit board  402 , for example, on a circuit board external to circuit board  402  within housing  1014 . In one embodiment, apparatus  1000  can include CPU  1060 , memory  1085 , and network communication interface  1252  comprising a first computer housed within housing  1014  (shown as a dashed border in  FIG. 1 ), and a second computer  6000  external to housing  1014 , having a CPU  6010 , memory  6020  and a network communication interface  6030 . Image data can be transmitted to the second computer  6000  for processing by the CPU  6010  for attempting to decode decodable indicia. Where second computer  6000  is not utilized for a referenced processing, apparatus  1000  can be regarded as being provided by the first apparatus. 
     A small sample of systems methods and apparatus that are described herein is as follows: 
     A 1  An imaging apparatus comprising: an imaging assembly including an imaging lens and an image sensor array, the imaging assembly defining a field of view, the image sensor array having a plurality a pixels, the plurality of pixels including color sensitive pixels having wavelength selective color filter elements; an illumination assembly that, during a frame exposure period of the imaging assembly simultaneously projects on a target light within the blue wavelength band, the green wavelength band and the red wavelength band; wherein the imaging lens is a two element glass imaging lens, the imaging lens having a first glass lens element and a second glass element; wherein the imaging apparatus captures a frame of image data representing light incident of the image sensor array during an exposure period; and wherein the imaging apparatus includes a pass band filter that selectively passes light within first second and third pass bands, the first pass band being defined in the blue wavelength band, the second pass band being defined in the green wavelength band, the third pass band being defined in the red wavelength band; wherein the imaging apparatus processes the frame of image data for attempting to decode decodable indicia. A 2 . The imaging apparatus of claim A 1 ,wherein the first pass band is separated from the second pass band and wherein the second pass band is separated from the third pass band. A 3 . The imaging apparatus of claim A 1 ,wherein the imaging lens has a chromatic aberration to effective focal length ratio of less than 0.0025. A 4 . The imaging apparatus of claim A 1 ,wherein the imaging lens has a chromatic aberration to effective focal length ratio of less than 0.0020. A 5 . The imaging apparatus of claim A 1 , wherein the illumination assembly comprises a single light source. A 6 . The imaging apparatus of claim A 1 ,wherein the illumination assembly includes a white light source emitting light that spans multiple visible color wavelength bands. A 7 . The imaging apparatus of claim A 1 , wherein the imaging lens includes a chromatic aberration of less than would be exhibited by the imaging lens if the imaging lens were optimized in a single broad band configuration. A 8 . The imaging apparatus of claim A 1 ,wherein the first lens element has a light entry surface curvature greater than a light entry surface curvature that would be exhibited by the first lens element if the imaging lens were optimized in a single broad band configuration. A 9 . The imaging apparatus of claim A 1 ,wherein the first lens element has a light entry surface curvature greater than a light entry surface curvature that would be exhibited by the first lens element if the imaging lens were optimized in a single broad band configuration. A 10 . The imaging apparatus of claim A 1 , wherein the first lens element has a light entry surface curvature greater than a light entry surface curvature that would be exhibited by the first lens element if the imaging lens were optimized in a single broad band configuration. A 11 . The imaging apparatus of claim A 1 ,wherein the second lens element has a light entry surface curvature greater than a light entry surface curvature that would be exhibited by the second lens element if the imaging lens were optimized in a single broad band configuration. A 12 . The imaging apparatus of claim A 1 ,wherein the first and second lens elements have indices of refraction reduced relative to indices of refraction that would be exhibited by the first and second lens elements if the imaging lens were optimized in a single broad band configuration. A 13 . The imaging apparatus of claim A 1 ,wherein the first and second lens elements have V numbers increased relative to V numbers that would be exhibited by the first and second lens elements if the imaging lens were optimized in a single broad band configuration. A 14 . The imaging apparatus of claim A 1 ,wherein the first lens element and the second lens element are devoid of aspherical light entry and light exit lens surfaces. A 15 . The imaging apparatus of claim A 1 ,wherein the imaging apparatus includes a hand held housing in which the image sensor array is disposed. 
     B 1 . A method comprising: defining first second and third configurations, wherein the first second and third configurations are defined to match first second and third pass bands of a multiple pass band filter; defining a fourth configuration having first second and third wavelengths, respectively, within the first second and third pass bands; providing an imaging lens by establishing merit functions within the four configurations to seek an optimized solution for the first, second and third pass bands. B 2 . The method of claim B 1 , wherein the method includes incorporating the imaging lens into an imaging apparatus having the multiple pass band filter. B 3 . The method of claim B 1 , wherein the method includes incorporating the imaging lens into an imaging apparatus having an image sensor array including color sensitive pixels and indicia decoding capability. 
     C 1 . A method for reducing chromatic aberrations of an imaging lens having first and second lens elements, the method comprising two or more of (a) through (h); (a) increasing a curvature of a light entry; (b) increasing a curvature of a light exit surface of the first lens element; (c) increasing a curvature of a light entry surface of the second lens element; (d) increasing a curvature of a light exit surface of the second lens element; (e) decreasing an index of refraction of the first lens element; (f) decreasing an index of refraction of the second lens element; (g) increasing a V number of the first lens element; (h) increasing a V number of the second lens element. C 2 . The method of claim C 1 , wherein the method includes performing three or more of (a) through (h); (a) increasing a curvature of a light entry; (b) increasing a curvature of a light exit surface of the first lens element; (c) increasing a curvature of a light entry surface of the second lens element; (d) increasing a curvature of a light exit surface of the second lens element; (e) decreasing an index of refraction of the first lens element; (f) decreasing an index of refraction of the second lens element; (g) increasing a V number of the first lens element; (h) increasing a V number of the second lens element. C 3 . The method of claim C 1 , wherein the method includes performing each of (a) through (h); (a) increasing a curvature of a light entry; (b) increasing a curvature of a light exit surface of the first lens element; (c) increasing a curvature of a light entry surface of the second lens element; (d) increasing a curvature of a light exit surface of the second lens element; (e) decreasing an index of refraction of the first lens element; (f) decreasing an index of refraction of the second lens element; (g) increasing a V number of the first lens element; (h) increasing a V number of the second lens element. 
     While the present invention has been described with reference to a number of specific embodiments, it will be understood that the true spirit and scope of the invention should be determined only with respect to claims that can be supported by the present specification. Further, while in numerous cases herein wherein systems and apparatuses and methods are described as having a certain number of elements it will be understood that such systems, apparatuses and methods can be practiced with fewer than or greater than the mentioned certain number of elements. Also, while a number of particular embodiments have been described, it will be understood that features and aspects that have been described with reference to each particular embodiment can be used with each remaining particularly described embodiment.