Abstract:
A flasher sonar device includes a flasher that produces light output pulses along a flasher ring display based upon sonar returns. A user interface selects between a normal mode and a zoom mode. When the normal mode is selected, a controller drives the flasher to display a normal range. When the zoom mode is selected, the controller divides the normal range into a first range and a second range, compresses the first range into a compressed range, enlarges the second range into an enlarged range, and drives the flasher to display the enlarged range interleaved with the compressed range.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of Provisional Application No. 61/004,832 filed Nov. 30, 2007 for “Flasher Fish Finder” by C. Arney, C. Bennett, D. Betts, S. Harrington, and D. Malphurs. This application is also related to co-pending, commonly assigned U.S. patent application entitled “Flasher Sonar Device with Light Guide” having Ser. No. 12/291,280, filed on even date herewith. This application is also related to, commonly assigned U.S. patent application entitled “Flasher Sonar Device with LCD Annotations” having Ser. No. 12/291,283, filed on even date herewith. 
     INCORPORATION BY REFERENCE 
     The aforementioned Provisional Application No. 61/004,832 is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present invention relates to sonar devices, and in particular, to a flasher type sonar device. 
     Sonar systems are widely used by anglers in determining the depth of water in a lake or river, as well as the presence and depth of fish. Sonar systems use a transducer to generate a sonar pulse that is directed down through the water. The transducer receives a sonar echo return from the bottom, as well as sonar returns from fish or other objects in the water column located within the sonar beam. The time between the transmission of the sonar pulse and the reception of the sonar return can be used as a measure of the distance from the transducer to the bottom, or the distance of the transducer to the fish. Currently popular fish finders take two different forms. In one form, the fish finder has a liquid crystal display that presents a scrolling picture of the bottom, suspended fish, and submerged structure such as weeds, trees, and the like. 
     The other form of fish finder (referred to as a flasher) has a circular ring lens with an adjacent scale indicating distance below the transducer. The location of the transducer appears at the top of the ring at the 12 o&#39;clock or 0° position. A motor driven disc or spinner carrying multiple colored light sources rotates behind the lens. As the disc rotates, light is emitted by the light sources at different positions around the ring to represent sonar returns from suspended fish or other objects, as well as from the bottom. The color of the light flashes represents the signal intensity of the sonar return, and the angular position of the flash represents a depth of the fish, object, or bottom from the transducer. Examples of flasher type fish finders are shown in Frederickson et al. U.S. Pat. No. 3,952,279; Yamamoto et al. U.S. Pat. No. 3,964,012; Grilk U.S. Pat. No. 4,644,512; Yamamoto et al. U.S. Pat. No. 5,973,997; Cummings et al. U.S. Pat. No. 6,768,701; Asakura U.S. Pat. No. 6,650,595; and Noda et al. U.S. Pat. No. 7,057,972. 
     SUMMARY 
     According to the present invention, a flasher sonar device includes a flasher that produces light output pulses along a flasher ring display based upon sonar returns. A user interface selects between a normal mode and a zoom mode. When the normal mode is selected, a controller drives the flasher to display a normal range. When the zoom mode is selected, the controller divides the normal range into a first range and a second range, compresses the first range into a compressed range, enlarges the second range into an enlarged range, and drives the flasher to display the enlarged range interleaved with the compressed range. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an exploded view of one embodiment of the flasher sonar device of the present invention. 
         FIG. 1B  is a front view of one embodiment of the flasher sonar device. 
         FIG. 1C  is a perspective view, from the rear of the sonar device of  FIG. 1A  with the rear housing assembly removed. 
         FIG. 2A  shows an exploded perspective view from the rear of the front housing assembly of the flasher of  FIGS. 1A-1C . 
         FIG. 2B  is a rear perspective view of an assembled front housing assembly, with display support foam pads shown in exploded view. 
         FIG. 2C  is an exploded front perspective view of the front housing assembly. 
         FIG. 3A  is an exploded view of the rear housing assembly. 
         FIG. 3B  is a perspective view showing the inside of the rear housing assembly. 
         FIG. 4A  is an exploded view of the LCD display module. 
         FIG. 4B  is a perspective view showing the rear side of the LCD display module. 
         FIG. 5A  is an exploded view from the rear of the spinner assembly. 
         FIG. 5B  is an exploded view from the front side of the spinner assembly. 
         FIG. 5C  is a side view of an alternative embodiment of a light guide assembly. 
         FIG. 5D  is a side view of another alternative embodiment of a light guide assembly. 
         FIG. 6A  is an exploded view generally from the front side of the main circuit board and motor assembly. 
         FIG. 6B  is a perspective view showing the rear side of the main circuit board and motor assembly. 
         FIG. 7  is a sectional view along section  7 - 7  of  FIG. 1B . 
         FIG. 8  is a block diagram of the flasher sonar device. 
         FIGS. 9A-9B  are front views of an embodiment of the flasher sonar device illustrating the dynamic depth range feature. 
         FIGS. 10A-10G  are front views of the flasher sonar device illustrating the active cursor feature. 
         FIGS. 11A-11D  are front views of the flasher sonar device illustrating the zoom feature. 
         FIGS. 12A-17A  show front views of the LCD display in unzoomed state. 
         FIGS. 12B-17B  show front views of the LCD display in a zoomed state. 
         FIG. 18A  shows the LCD display with all elements of the numerical displays, words, symbols, and icons activated. 
         FIG. 18B  shows a diagram of the keypad, encoder, and selector switch inputs. 
         FIGS. 19A-19J  illustrate information displayed on the LCD display in response to different input selections. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  shows an exploded view of one embodiment of flasher fish finder  10 , which includes front housing assembly  12 , gasket  14 , liquid crystal display (LCD) module  16 , flex connector  18 , LCD module mounting screws  20 , spinner assembly  22 , main printed circuit board assembly  24 , motor  26 , flex connector  28 , main PCB mounting screws  30 , rear housing assembly  32 , and main housing screws  34 . 
     On its front face (shown in  FIG. 1B ), front housing assembly  12  includes flasher display  40  and user inputs  42 . Flasher display  40  includes LCD display lens  44 , lens overlay ring  46  (which surrounds LCD display lens  44 ), and flasher ring lens  48  (which surrounds overlay ring  46 ). In the embodiment shown in  FIG. 1B , user inputs  42  include encoder knob  50 , selector knob  52 , and keys  54 A- 54 D. In other embodiments, two additional keys  54 E and  54 F are also included (see  FIGS. 9A-11D ). 
     LCD module  16  is positioned behind LCD display lens  44  and provides both alphanumeric information and icons. LCD module  16  cooperates with graduation markers on overlay ring  46  to provide dynamic annotated range scales for flasher display  40 . Depending upon the range selected using selection knob  52 , LCD module  16  provides the numerical values corresponding to the graduations, so that the user sees the appropriate numerical depth value for the selected range. 
     LCD module  16  also displays a digital depth value and provides visual feedback for settings such as sensitivity and noise. User interface icons and words are displayed by LCD module  16  to allow the user to quickly determine the current settings and operating modes of fish finder  10 . 
     The flasher light signals that appear through flasher ring lens  48  are produced by spinner assembly  22 , which is mounted behind LCD module  16 . Flasher ring lens  48  can be any circular or annular window, and is typically a transparent plastic ring with annular, concentric grooves. Spinner assembly  22  is a cup shaped unit that is mounted on the output shaft of motor  26 . Spinner assembly  22  carries a rotating fiber optic light pipe that has an inlet end at the center of spinner assembly  22 , and an outlet end at the outer periphery of spinner assembly  22 . Light is provided to the inlet end of the fiber optic light pipe by a multicolor LED source mounted on the back side of LCD module  16 . 
     Spinner assembly  22  also includes an interrupt arm (synchronization interrupter  154  shown in  FIGS. 5A and 5B ) that is used to synchronize flasher operation. Each time the interrupt arm passes through a detector carried on main circuit board  24 , a synchronization pulse is generated which is used to calculate spinner speed and top dead center position. 
     Main circuit board assembly  24  carries electronic circuitry that processes inputs from user interface, control operations of the sonar transducer (not shown), processes sonar return signals, and controls operation of LCD module  16  and spinner assembly  22 . Flex connector  18  connects LCD module  16  to main circuit board  24 . Flex connector  28  connects the user inputs  42  from front housing assembly  12  to main circuit board  24 . 
     Rear housing assembly  32  carries a connector panel on its rear surface. The connector panel provides electrical connection to a dual frequency/dual beam sonar transducer and to a battery power cable. 
     When the components shown in  FIG. 1A  are assembled, LCD assembly  16  is attached to front housing assembly  12  by screws  20 . Spinner assembly  22  is press fit onto the shaft of motor  26 , and main circuit board  24  is attached to front housing assembly  12  by screws  38 .  FIG. 1C  shows flasher  10  with all components assembled, except for rear housing assembly  32 . 
     Gasket  14  provides a seal between front housing assembly  12  and rear housing assembly  32  when they are assembled. Screws  34  attach rear housing assembly  32  to front housing assembly  12 . 
       FIGS. 2A-2C  show front housing assembly  12 . Front housing assembly  12  includes lens overlay ring  46 , encoder knob  50 , selector knob  52 , front housing  70 , bezel  72 , key pad  74  (including keys  54 A- 54 D), key pad printed circuit board  76 , encoder module  78  (with washers  80  and  82  and nut  84 ), rotary selector switch  86  (and nut  88 ), display support foam elements  90 , and screws  92 . As can be seen in  FIGS. 2A-2C , front housing  70  includes two additional apertures  94  and  96  for two additional keys. In the embodiment shown in  FIGS. 2A-2C , bezel  72  covers apertures  94  and  96 , so that only four keys  54 A- 54 D are accessible. In another embodiment, bezel  72  includes apertures with a line with apertures  94  and  96  so that six input keys  54 A- 54 F (shown in  FIG. 9A ) are available. This allows additional functions to be provided, as will be discussed later in this application. 
       FIGS. 3A and 3B  show rear housing assembly  32 , which includes rear housing  100 , label  102 , gasket  104 , connector panel  106 , screws  108 , and water tight air vent  110 . 
       FIGS. 4A and 4B  show LCD module  16 , which includes printed circuit board  120 , back light assembly  122 , LCD support foam  124 , and LCD display  126 . On the back side of LCD module  16  (as shown in  FIG. 4B ), multicolor LED light source  128  is mounted so that it will be aligned with the axis of rotation of spinner assembly  22 . The LED source  128  includes multiple light emitting diodes for emitting red, green, and blue light. By varying the intensity of red, green, and blue light emitted from the light emitting diodes, a full spectrum of different colors, including white, can be generated. 
       FIGS. 5A and 5B  show spinner assembly  22 , which includes spinner disc  130 , light pipe assembly  132  and light pipe cap  134 . Spinner disc  130  includes center cup  136 , outer flange  138 , counterweight rim  139 , hub  140 , light output area  142 , access slot  144 , fiber optic cradles  146  and  148 , inlet end holder  150 , mounting pins  152 , and synchronization interrupter  154 . 
     Light pipe assembly  132  includes a bundle of optical fibers  156 , inlet end  158 , sleeve  160 , and outlet end  162 . Optical fibers  156  are arranged in a circular bundle at inlet end  158 . They pass as a bundle through sleeve  160 , and then are arranged in a fan shaped arrangement in outlet end  162 . Inlet end  158  is supported by inlet end holder  150  of spinner disc  130 . Cradles  146  and  148  hold sleeve  160  in place. Slot  144  in spinner disc  130  is shaped to allow insertion of inlet end  158  and sleeve  160  into cup  136 , while allowing optical fibers  156  to pass from the interior of cup  136  to light output area  142 . The male portion of outlet end  162  of light pipe assembly  132  is received in the female portion of light output area  142  on the back side of flange  138 . The top surface of flange  138  has a matte finish which is relatively dark and non-reflective. Counterweight rim  139  is attached to flange  138  opposite of light pipe assembly  132  in order to balance spinner disc  130  when spinning. 
     Light pipe cap  134  fits over inlet end  158  of light pipe assembly  132  and inlet end holder of spinner disc  130 . Pins  152  extend through holes  164  in flange  166  of light pipe cap  134 . Center aperture  168  of cap  134  is aligned with fibers  156  at inlet end  158  of light pipe assembly  132 . 
     In other embodiments, light pipe assembly  132  could be one of a variety of light guides that can receive light from light source  128  at inlet end  158  and emit it at outlet end  162 . 
       FIG. 5C  illustrates an alternative embodiment of a light guide assembly. Light guide assembly  132 ′ includes a single element light pipe as opposed to including bundle of optical fibers  156 . Light guide assembly  132 ′ functions similarly to light pipe assembly  132  in that light enters at inlet end  158 ′ and is emitted at outlet end  162 ′.  FIG. 5D  illustrates another alternative embodiment of a light guide assembly. Light guide assembly  132 ″ includes a series of mirrors  169 A and  169 B configured to concentrate and reflect light emitted from light source  128 . Mirror  169 A can be an optically reflective surface configured to gather light at input end  158 ″ from light source  128  and reflect it to mirror  169 B. Mirror  169 B can be an optically reflective surface configured to receive light from mirror  169 A and reflect collimated light out outlet end  162 ″ toward flasher ring lens  48 . In still other embodiments, a light guide assembly can be a hybrid that includes a single-element light pipe together with a bundle of optical fibers or a hybrid that includes a curved mirror together with a bundle of optical fibers. In each of these embodiments, the light guide can direct light from the inlet end to an outlet end in a concentrated beam. 
       FIGS. 6A and 6B  show main circuit board assembly  24 . In these views, individual electronic components mounted on circuit board assembly  24  are not shown. In  FIGS. 6A and 6B , motor  26  is mounted on printed circuit board  170 . Screws  172  and lock washers  174  attach motor  26  to the back side of circuit board  170 . Shaft  176  of motor  26  extends through central aperture  178  in circuit board  170 , so that it can be attached to hub  136  of spinner assembly  22 . 
     As shown in  FIG. 6A , optical sensor  180  is mounted on the front side of circuit board  170 . Optical sensor  180  is a top dead center indicator that is positioned to detect interrupter  154  of spinner assembly  22  each time interrupter  154  passes through optical sensor  180 . This causes a synchronization pulse to be generated that is used by the circuitry carried on circuit board  170  to produce the top dead center reference line on the flasher display. 
       FIG. 7  is a perspective view of flasher fish finder  10 , sectioned along section  7 - 7  of  FIG. 1B . 
       FIG. 8  is a block diagram of flasher fish finder  10 . The main components shown in  FIG. 8  are LCD module  16 , main control board  24 , user interface  42 , the LED flasher display (formed by motor  26 , LED light source  128  and light pipe assembly  132 ), battery  200 , and dual frequency/dual beam sonar  202 . Operation of flasher fish finder  10  is coordinated and controlled by microprocessor  210  on main circuit board  24 . 
     Main circuit board  24  also includes power control  212 , boost transmit voltage supply  214 , adjustable sonar transmit voltage supply  216 , sonar transmit circuitry  218 , sonar receive circuitry  220 , battery monitor  222 , LED driver  224 , top dead center indicator  180 , motor control  228 , and LCD interface  230 . 
     LCD module  16  includes LCD display  126  and display controller  232 . User interface  42  includes user interface circuitry  234 , keypad  74 , rotary encoder  78 , selector switch  86 , and multitone buzzer  236 . Flasher display  46  includes spinner assembly  22 , motor  26 , and LED  64 . 
     Battery  200  provides electrical power to power control  212  on main circuit board  24 . Power control  212  turns on and off power to all of the components of flasher  10 . It also includes voltage regulation circuitry to provide the voltages required by the logic circuitry of flasher fish finder  10 . Boost transmit voltage supply  214  increases the voltage from power control  212  to 30 volts from the battery voltage of 12 volts. The 30 volt output of boost transmit voltage supply  214  is provided to adjustable sonar transmit voltage supply  216 , which provides the power to sonar transmit circuitry  218 . Microprocessor  12  can control adjustable sonar transmit voltage supply  216  in order to adjust the sonar power used to drive dual frequency/dual beam sonar  202  as a function of water depth. 
     In one embodiment, sonar transducer  212  is driven at one of two different frequencies: about 240 kHz for a wide beam and about 455 kHz for a narrow beam. The wide beam gives greater lateral coverage, while the narrow beam provides less coverage but higher resolution. 
     Sonar receive circuitry  212  receives the sonar returns from transducer  202 , and provides them to microprocessor  210 . Signal processing of the sonar returns, including noise settings, and gain settings can be achieved by adjusting thresholds used by microprocessor  210  in processing the sonar return signals. Microprocessor  210  stores the intensity of sonar return signals in bins based on the time between the sonar transmit pulse and the receipt of the sonar return signal. 
     Microprocessor  210  controls the flasher display based upon stored sonar returns and the top dead center signal received by top dead center indicator (optical sensor)  180 . The top dead center indication (which indicates when interrupter  154  passes through optical sensor  180 ) allows microprocessor  210  to synchronize the light output of multicolor LED  128  (and therefore the fiber optic light pipe  132 ) with rotation of spinner assembly  22 . Microprocessor  212  provides drive signals to LED  128  through LED driver  224 . The color of the light generated by LED  128  is dependent upon the color selected by microprocessor  210  with LED driver  224 . In one embodiment, LED  128  is a Harvatek red, green, blue power LED module. 
     Microprocessor  210  controls the rotation of spinner assembly  22 . Motor control signals that are provided by microprocessor  210  to motor control  228 , which controls the speed of motor  26 . 
     Microprocessor  210  controls operation of LCD display  126  through LCD interface  220  and display controller  232 . Depending upon the inputs microprocessor  210  receives from user interface  42 , different information can be displayed on LCD display  126  to provide a number of different display features and other functionality. 
     Microprocessor  210  receives input signals through interface circuitry  234  from rotary encoder  78 , keypad  74 , and selector switch  86 . Multitone buzzer  236  provides an audio feedback to the user when keys on keypad  74  are pressed. Microprocessor  210  provides signals to multitone buzzer  236  in response to detected key presses on keypad  74 . 
     Battery monitor  222  monitors the power from battery  200  to provide a signal representing the state of charge of battery  200 . Upon receiving an input from keypad  74  requesting battery status, microprocessor  210  causes a battery percentage value to be displayed on LCD display  126 . 
     The use of LCD display  126  in conjunction with the flasher display allows flasher  10  to provide a number of unique features that will be described in more detail with reference to  FIGS. 9A-19J .  FIGS. 9A and 9B  illustrate a dynamic depth range feature of flasher  10 .  FIGS. 10A-10G  illustrate operation of an active cursor or target depth feature.  FIGS. 11A-11D  illustrate operation of a zoom feature, as do  FIGS. 12A-17A  and  12 B- 17 B.  FIGS. 18A ,  18 B, and  19 A- 19 J show how different information can be displayed on LCD display  126  depending upon the particular feature selected by the user through user interface  42 . 
     In each of  FIGS. 9A-11D , a front view of flasher  10  is shown. User interface  42  includes rotary encoder knob  50 , select switch knob  52 , zoom key  54 A, gain key  54 B, noise key  54 C, beam key  54 D, color key  54 E, and cursor key  54 F. 
     LCD display  126 , ring overlay  46 , and flasher ring  48  provide a variety of different output alternatives, depending upon the particular inputs provided by the user through user interface  42 . Ring overlay  46  is positioned concentrically between LCD display  126  and flasher ring lens  48 . Ring overlay defines a scale that includes ten major graduations  300  that are separated by arcs of 36 degrees. The uppermost or top dead center graduation represents the location of the sonar transducer, i.e. a depth of zero. The distance between each pair of major graduations is divided into four segments of 9 degrees each. 
     The depth represented by the distance between major graduations  300  can vary depending upon the range selected by the position of rotary selector knob  52 . When the units of measurement are feet, the distance between two major graduations  300  can be as small as 2 feet and as large as 20 feet. 
     Rotary selector knob  52  shown in  FIG. 9A  has six possible positions: Off, A (automatic range selection), X 1 , X 2 , X 4 , and X 10 . When knob  52  is in the Off position, flasher  10  is turned off. The X 1  position indicates the smallest range, in which each distance between major graduations  300  is 2 feet. In that case, the full range of flasher display  40  is 0 to 20 feet. 
     The X 2  position of rotary selector knob  52  selects a range in which the distance between major graduations  300  is twice the base distance provided by the X 1  setting. In other words, the X 2  setting will produce a display in which the distance between major graduations  300  represents 4 feet. In that case, a full range in the X 2  position represents 0 to 40 feet. 
     The X 4  position, which is the position shown in  FIG. 9A , produces a distance between major graduations that is 4 times the base distance. When the units are in feet, this results in increments between major graduations equal to 8 feet. In  FIG. 9A ; LCD display  126  labels major graduations in 8 foot increments, and the full range of the flasher display represents 0 feet to 80 feet. 
     The X 10  position of rotary selector knob  52  will provide increments between major graduations  300  that are 10 times the base increments used for the X 1  range. When the units of measurement are feet, the X 10  range produces an increment of 20 feet between major graduations and a full range of 0 to 200 feet. 
     The A range setting of rotary selector knob  52  selects an automatic range feature. In that case, microprocessor  202  selects a range based upon the distance to bottom which will yield the best utilization of the full 360° of the flasher display. As a greater portion of the 360° available on the flasher display is used to represent the water column between the transducer and bottom, the resolution of the flasher signals displayed becomes better. This is because microprocessor  210  stores sonar return data in much finer resolution than that which is normally displayed. As the scale is expanded to best fit the 360° available for display, the data available from microprocessor  210  can be shown in more resolution. Microprocessor  210  will select a range from among the standard range settings (X 1  to X 10 ), or intermediate range settings if they provide a better fit.  FIG. 9B  illustrates operation in the automatic range mode. In this case, a best fit is provided by increments of 6 feet between major graduations. This would correspond to an X 3  range, which is not one of the preset ranges available by turning rotary selector knob  52 . Other range options automatically selectable include X 5 , X 6 , X 7 , X 8 , and X 9 . In another embodiment, a variety of possible range combinations can be selected manually by rotary selector knob  52  or automatically by microprocessor  202 . The range combinations can include different units of linear measurement (such as metric units) or simply include different numbers than those chosen in the illustrated embodiment. 
     In the case illustrated in  FIG. 9B , the depth bottom is 48.2 feet. By selecting an X 3  range automatically, a full range displayed is from 0 to 60 feet, so that a depth of 48.2 feet results in the best utilization of the full range of flasher display  40 . If X 2  range were selected, the range would be from 0 to 40 feet, which would result in the bottom not appearing on flasher display  40 . If an X 4  range were selected, the full range would be 0 to 80 feet, meaning that more than half of the full range of flasher display  48  is used (as illustrated in  FIG. 9A ). A comparison of  FIGS. 9A and 9B  show the better utilization and higher resolution possible with the auto-range feature. 
     Although these examples have been given in terms of feet, similar functionality is provided when the units of measurement are meters. A base range is defined by the X 1  range, and a maximum range is defined by the X 10  range. 
       FIGS. 9A and 9B  also illustrate the dynamic annotated range scale feature of flasher  10 . LCD display  126  provides the numerical depth values adjacent each of the major graduations  300 . In  FIG. 9A , the depth at the top dead center graduation is “0”. The numerical depth value displayed adjacent the first major graduation after top dead center is “8” representing 8 feet. Adjacent the next major graduation is “16” representing 16 feet, and so on. In the illustrated embodiment, the dynamic annotated range scale on LCD display  126  is adjacent to overlay ring  46 , which, is adjacent to flasher ring lens  48 . The graduations on overlay ring  46  cause the numbers of the dynamic annotated range scale to correspond to points on flasher ring lens  48 . In another embodiment, the dynamic annotated range scale on LCD display  126  can be directly adjacent to flasher ring lens  48 . In either embodiment, the dynamic annotated range scale is close enough to flasher ring lens  48  to be substantially adjacent to it. 
     In  FIG. 9B , LCD display  126  again displays “0” at the top dead center graduation. The first major graduation after top dead center has the number “6” displayed on LCD display  126  to represent a depth of 6 feet. The next major graduation has the number “12” adjacent representing 12 feet. The numbers continue from “0” through “52” in  FIG. 9B , in comparison to “0” through “72” in  FIG. 9A . 
     The ability to provide dynamic annotated range scales allows meaningful information to be displayed at all times, regardless of the range being used. Unlike prior flashers having fixed numerical values on the depth scale, the user of flasher  10  does not need to multiply the numeric values adjacent graduations in order to determine the actual depth, and does not need to know the particular range being used before knowing how to interpret the information on flasher display  40 . Instead, the numerical values corresponding to the major graduations are changed automatically by microprocessor  210  by providing appropriate signals to LCD display  126 . A change of numerical values corresponding to the major graduations occurs each time a different fixed range setting is selected, when an automatic range change is made, or when a zoom feature is activated. Also, when a change is made from feet to meters, a similar adjustment will be made as necessary to the numbers displayed by LCD display  126  adjacent the major graduations. As a result, flasher  10  provides an intuitive easy to use and understand display of information. In the disclosed embodiment, the dynamic annotated range scale changes the numeric values for many different manual and automatic functions. In another embodiment, the dynamic annotated range scale can change numeric values manually or automatically for as few as a single function. 
       FIGS. 10A-10G  illustrate an active cursor mode, which is selected by pressing cursor key  54 F. If  FIG. 10A , flasher display  40  shows top dead center reference mark TDC at 0 feet and bottom B near 48 feet. In addition, marks J and F appear at about 24 and about 26 feet respectively. Mark J represents a jig or lure, and mark F represents a suspended fish. 
     In  FIG. 10B , cursor key  54 F has been pressed, which causes an additional cursor mark C to appear on flasher display  40  adjacent reference mark TDC. Cursor mark C may, for example, be a white mark to distinguish it from the other marks appearing on flasher display  40 . Cursor C can be moved by rotation of encoder button  50 .  FIG. 10C  shows cursor mark C which has been moved from 0 to 8.2 feet. The depth represented by cursor C is also displayed numerically on LCD display  126 . 
     In  FIG. 10D , knob  50  has been rotated to move cursor C to 26.3 feet, which is right by mark F representing the fish. 
     In  FIG. 10E , the fish that was located at 26 feet has moved out of the water column covered by the sonar beam. As a result, jig mark J representing the jig or lure remains at 24 feet, and cursor C remains at 26.3 feet. 
     In  FIG. 10F , the user has lowered the jig so that jig mark J it is slightly above cursor C, and in  FIG. 10G , jig mark J is now below cursor C. This feature allows an angler to set a reference depth based upon sonar returns seen on the display, and leave that reference marker cursor in place after the fish has moved out of the sonar beam and no longer appears on the flasher display. Cursor C remains as a reference position for adjusting the location of the lure such as a jig. This is particularly advantageous in ice fishing, where the angler and sonar transducer are stationary, and fish can move in and out the sonar pulse column. 
       FIGS. 11A-11D  illustrate the zoom feature of flasher  10 .  FIG. 11A  shows flasher  10  before the zoom button  54 A is pressed. In  FIG. 11B , zoom key  54 A has been pressed, which causes the word “zoom” to appear on LCD display  126 . In addition, the series of five markers Z are displayed on LCD display  126  representing an arc from 0° to 90°. In the illustrated embodiment, markers Z are a series of circumferential lines. In alternative embodiments, markers Z can be any shape that clearly marks a zoom area, such as radial line cursors. Zoom cursors Z 1  and Z 2  are also displayed on flasher display  40  to define the 0° to 90° segment. 
     In  FIG. 11C , encoder knob  50  has been rotated to advance the 90° segment defined by markers Z on LCD display  126  and cursors Z 1  and Z 2  on flasher display  40 . In the position shown in  FIG. 11C , the 90° segment extends from 162° to 252°.  FIG. 11D  shows the display when knob  50  is pressed to activate zoom. The 90° segment is expanded to encompass 180° rather than 90° of display  40 . In the example shown in  FIG. 11D , the full range has been maintained, including the zoomed region within the 360° of flasher display  40 . This is in contrast with prior art zoom displays on flashers, in which the zoomed area normally is displayed on one half of the display (such as the left half) and a full range display is displayed on the opposite half. The prior art zoom displays are difficult to read and are non-intuitive. In the zoom feature of flasher  10 , the ability to expand a 90° segment to 180°, and to adjust the numerical values adjacent the major graduations to reflect the zoomed and compressed segments, makes the zoomed display easier to understand and easier to use. For example, in  FIG. 11C , the distance between each major gradation is annotated as 8 feet around the entire 360° of LCD display  126 . In  FIG. 11D , however, the zoomed region has been expanded and the remaining non-zoomed, or compressed, region has been compressed. Thus, the distance between each major gradation adjacent to the zoomed region has been reduced by 50% and is now 4 feet between each major gradation. Conversely, the distance between each major gradation adjacent to the compressed region has been increased by 50% and is now 12 feet between each major gradation. 
       FIGS. 12A-17A  and  12 B- 17 B illustrate another embodiment of the zoom feature.  FIGS. 12A-17A  show an unzoomed display on LCD display  126 . In each  FIG. 12A-17A , a 90° arc is identified by markers Z. The display shows a full range of 0-200 feet. In  FIG. 12A , the selected 90° segment corresponds to 0-50 feet. In  FIG. 13A , the segment corresponds to 30-80 feet. In  FIG. 14A , the 90° segment corresponds to 60-110 feet. In  FIG. 15A , the 90° segment corresponds to 90-140 feet. In  FIG. 16A , the 90° segment corresponds to 120-170 feet. Finally, in  FIG. 17A , the 90° segment corresponds to 150-200 feet. Thus, the 90° segment has been moved in six equal steps around the circumference of display  126  to define six potential zoom segments. 
       FIGS. 12B-17B  show the same selected segment of  FIGS. 12A-17A  zoomed so that it occupies 180° rather than 90° of the circumference. In each case, the numerical values adjacent the major graduations are adjusted in the zoomed and the non-zoomed or compressed regions in  FIGS. 12B-17B . For example, the major graduations in the zoomed area represent increments of 10 feet, which is 50% less than the 20 foot increments in  FIGS. 12A-17A . The major graduations in the compressed or non-zoomed area represent increments of 30 feet, which is 50% more than the 20 foot increments in  FIGS. 12A-17A . In other embodiments, the major graduations of the zoomed and the non-zoomed or compressed regions can be decreased and increased by any factor so long as the annotations correspond to the information displayed in the zoomed and the non-zoomed or compressed regions substantially accurately. 
       FIG. 18A  shows a view of LCD display  126  with all segments and icons activated.  FIG. 18B  shows input keys  54 A- 54 F, as well as knobs  50  and  52 . Various features of flasher  10  are selectable through the use of keys  54 A- 54 F and encoder knob  50 . In certain respects, segments and icons activated in  FIG. 18A  differ from segments and icons activated in other figures, such as  FIGS. 12A-17B . These differences illustrate just some of the embodiments of LCD display  126  that are possible. In other embodiments, segments and icons can be arranged in virtually any manner consistent with the invention disclosed, herein. 
     Zoom key  54 A is used to select a zoom mode, and encoder  50  is used to select the segment of the normal flasher display that will be expanded in a zoom display. To switch from a normal to a zoom display after the zoom mode has been selected, the user first selects the segment to be zoomed by rotating encoder knob  50 , and then switches to the zoom display by pressing encoder button  50 . To return to a normal display, the user presses encoder button  50  again. To exit the zoom mode, zoom button  54 A is pressed. 
     Gain key  54 B is used to select a gain setting. The gain setting is used by microprocessor  102  to set a threshold for return signals that will result in a flasher display line or pixel and the color of that line. The selection of a gain setting is provided by rotating encoder knob  50 . When the desired setting has been reached, it is entered by pressing encoder knob  50 . The gain setting is displayed on liquid crystal display  126  when the gain selection function has been selected by pressing gain key  54 B. 
     The gain key  54 B is also used to control whether backlighting will be provided to liquid crystal display  126 . The user can select backlighting by pressing and holding gain key  54 B until backlighting comes on. Similarly, backlighting can be turned off by again pressing and holding gain key  54 B. 
     Noise key  54 C is used to select noise settings. Pressing noise key  54 C causes the noise setting causes the noise settings to be displayed on liquid crystal display  126 . That noise setting then can be selected using encoder knob  50 . Selection of noise settings can be as simple as the selection between no noise filtering and filtering, or can involve multiple levels of noise rejection or filtering. 
     Noise key  56 C provides a different feature when it is pressed and held. In that case, a selection between feet and meters as the units of measurement can be made. The current depth using the current unit of measurement is displayed, and the user can change units by pressing encoder knob  50 . 
     Beam key  54 D allows the user to select either a wide beam or a narrow beam. Pressing beam key  54  toggles the narrow and wide beam selection. An icon appears on LCD display  126  indicating whether the current setting is a wide beam or a narrow beam. 
     Beam key  54 D can be used to obtain an indication of battery life remaining. The battery check feature is accessed by pressing and holding beam key  54 D. A battery life percentage appears on LCD display  126  to indicate battery life. 
     Color key  54 E allows the user to select one of three different color modes. Currently available flasher units typically use three colors: red, green, and amber, to represent the strength of the sonar return signals. Typically red represents the strongest sonar return signal and either green or amber represents the lowest sonar return signal that is displayed. When key  54 E is pressed, the user is given the opportunity to select one of three color modes. Two of the modes are three color modes, which differ from one another on whether green or amber is the weakest signal. The third mode is a six color mode, which provides much greater range of displayable information. In any of the three modes, a white line can also be generated, which is used for the active cursor feature described in conjunction with  FIGS. 10A-10G . 
     The color mode selection is done using color key  54 E to scroll between color modes  1 ,  2 , and  3 . The current selected color mode is displayed on LCD display  126  while the color selection mode is in process. 
     Cursor key  54 F is used to select an active cursor mode, which is illustrated in  FIGS. 10A-10G . 
       FIG. 19A-19J  show the center portion of display  126 . Different functions are selected using keys  54 A- 54 F and knobs  50  and  52 . 
       FIG. 19A  shows the display when zoom feature is active. The word “zoom” appears below the numerical depth. When the zoom feature is off, the word “zoom” does not appear. 
       FIG. 19B  shows the display when cursor key  54 F has been pressed. The cursor symbol appears immediately above the word “depth”. The same cursor symbol appears on cursor key  54 F. When the cursor symbol is present, the numerical depth value displayed is the cursor depth, rather than the bottom depth. 
       FIG. 19C  shows a gain setting of “14” and the word “gain”.  FIG. 19C  shows settings of “1” to “20” are indicated as available. In another embodiment, smaller or larger numbers of gain settings can be used. For example, in one embodiment, gain settings can vary from “1” to “45”. 
       FIG. 19D  illustrates the noise reject setting display. A numerical value (in this case 3) appears above the words “noise reject”. The settings may range 1 to 5 as illustrated in  FIG. 19D , or to larger or smaller numbers. 
       FIG. 19E  shows the color mode select when color key  54 E is pressed. Three possible modes are selectable, as described earlier. The mode selected is identified above the word “color”. 
     In  FIG. 19F , the status of battery  200  is displayed. This display is accessed by pressing and holding beam key  54 D. The numerical percentage displayed is generated by microprocessor  210  based upon a signal from battery monitor  222 . 
       FIG. 19G  shows a beam select display that is produced when beam key  54 D is pressed. Either a wide or narrow beam can be selected. A narrow beam icon appears in  FIG. 19G , while a wide beam icon appears in  FIGS. 19H ,  19 I, and  19 J. 
       FIG. 19H  shows the back light on/off display. When back lighting is on, the back light icon is displayed above the depth value. 
       FIG. 19I  illustrates a night mode which can be turned on or off. The night mode is designated by the moon icon that appears above the depth value. 
       FIG. 19J  illustrates display of depth in meters rather than feet. Selection of units is made by depressing and holding noise key  54 C. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.