this chapter explains present invention in such greater detail so any person skilled in the art would be readily able to make a product based on the outlined principle . one preferred embodiment of present invention is shown , it is obvious that various embodiments could be derived from principle of present invention . “ visual icon ” used herein refers to graph , text , picture , photo or any other objects that conveys meanings through vision , a visual icon could be 2 or 3 dimensional . “ surface ” used herein could be of any material , including but not limited to paper , wood , plastics , stone , glass , acrylic , etc . and it could be of any area , including but not limited to table , floor , wall , book , map , mat , mirror . “ data storage ” used herein refers to any device that could store data , such as memory cards ( e . g . compact flash card , smartmedia card , secure digital card , multimedia card , etc . ), optical disk ( e . g . cd - rom , dvd - rom ), magnetic media ( e . g . hard drive , tape ). “ response data ” used herein refers to data that responds to a user &# 39 ; s input . it could be data that represents sensible output such as sound , speech , music , flashing of leds ( light emitting devices ), picture , video or motion emulation shown on lcd ( liquid crystal display ), or control of internal components such as volume control , brightness control of lcd , change of surface , etc . “ game rules ” used herein refer to a collection of instructions that enable a user to play games . for example , a game rule consists of a question and an answer . in the question and answer game , the system asks the user a question , and it expects the user to give a right answer . in another example , a game rule is a tracing game that instructs the user to trace a letter , or an animal . there are numerous other types of game rules , including but not limited to walking a maze , memory game , matching game , etc . fig1 shows a regular surface 10 . on surface 10 , several graphics 13 and texts 16 exist . this regular surface 10 is not interactive by nature , since it does not accept user input nor produce output . an object of present invention is to provide game activity for a regular surface 10 . another object of present invention is intuitive usage , when a user points at a visual icon like graphic 13 or text 16 or surface number 11 , a response would be immediately provided by present invention . it is another object of present invention to work with a regular surface that does not require special attachment of buttons or electronics on it . those objects collectively would make this system more easy to use , more fun to use and cheaper to produce . fig2 depicts the functional block diagram 200 of presentation . it is shown that present invention consists of a surface 201 , an ultrasonic position determination device 210 , a control unit 220 , data storage 230 and a response unit 240 . ultrasonic position determination device 210 further consists of an ultrasonic base unit 213 and an ultrasonic pointing unit 216 . ultrasonic pointing unit 216 is used by a user to point at a visual icon on a regular surface with visual icons 201 that he or she would like to interact with . once said visual icon is pointed at , ultrasonic position determination device 210 would be able to calculate the coordinate of ultrasonic pointing unit 216 . said coordinate is input to control unit via interface 273 . based on said coordinate , control unit would search for response data correspond to it in data storage 230 . said response data could be processed and destine for its output via response unit 240 , or it could be used as control data for other components like volume control . response unit 240 may include a plurality of output such as speaker for audible response data , leds or lcd for visual effect . it is thus the great advantage of present invention , since it provides an intuitive way for a user to point at a visual icon then get the response . it is another great advantage of present invention since it employs ultrasonic position determination device 210 . unlike prior arts that generally use a sensor board placed underneath surface , present invention doesn &# 39 ; t require said sensor board , thus make it more economical to accommodate large and thick surface . fig3 outlines the principle 300 of ultrasonic position determination device . ultrasonic base unit includes a pair of ultrasonic transducers 310 . a and 310 . b located apart at a known distance “ w ” 313 . ultrasonic pointing unit includes an ultrasonic transducer 320 . given measured distance “ a ” 321 . a between transducers 310 . a and 320 , as well as distance “ b ” 321 . b between transducers 310 . b and 320 . position of ultrasonic pointing unit , ( x , y ) 323 , could be triangulated using “ w ” 313 , “ a ” 321 . a and “ b ” 321 . b . the same principle could be applied to a 3 dimensional space as well . it is a known and mature technique to measure distance using ultrasonic wave , which derive distance by measuring time - of - flight of ultrasonic wave propagating between 2 corresponding ultrasonic transducers . a common technique is to measure time - of - flight by threshold . fig4 illustrates one embodiment 400 of ultrasonic position determination device based on threshold . the device decides arrival of ultrasonic wave when its received signal level exceeds a threshold . the use of threshold is to avoid wrong decision if background noise exists . a 4 mhz crystal oscillator 433 clocks 2 counters 430 . a and 430 . b , which are initially reset to zero . when a user points at a visual icon using ultrasonic pointing unit 216 , an interrupt 412 to micro - controller 410 is triggered . transmit interrupt service routine 422 is invoked to serve the interrupt , which in turn triggers the 40 khz pulse generator 440 to produce 20 cycles of pulse , which in turn is converted to ultrasonic wave transmitted by ultrasonic transducer 320 of ultrasonic pointing unit 216 . in the mean time , counters 430 . a , 430 . b are triggered to run according to the clock . said transmitted ultrasonic wave propagates then is received by ultrasonic transducers 310 . a , 310 . b of ultrasonic base unit 213 . said received signals are amplified by stages of 450 . a , 450 . b respectively , then are compared against a threshold by comparators 453 . a , 453 . b respectively . once signal level exceeds said threshold , comparator 453 . a , 453 . b produce a pulse respectively , which stops the running of counters 430 . a , 430 . b respectively . interrupts 414 . a , 414 . b indicates the stop of counter 430 . a and 430 . b respectively . receive interrupt service routines 424 . a , 424 . b serve interrupts 414 . a , 414 . b respectively . receive interrupt service routines 424 . a , 424 . b read counters 430 . a , 430 . b respectively . counter values are converted to time by multiplying with period of 4 mhz crystal oscillator . thus distance “ a ” 312 . a between transducers 320 and 310 . a could be calculated by multiplying time with sound - speed , so does distance “ b ” 312 . b between transducers 320 and 310 . b . position calculation routine 426 is invoked to calculate the position ( x , y ) 323 of ultrasonic pointing unit 216 . other techniques exist to determine the position of ultrasonic pointing unit 216 . in principle , they base on time - of - flight of ultrasonic wave . once position ( x , y ) 323 of ultrasonic pointing unit 216 is determined . ( x , y ) 323 serve as input to control unit 220 . based on ( x , y ) 323 , control unit 216 searches for response data corresponding to ( x , y ) 323 in data storage 230 . in accordance with present invention , fig5 shows one embodiment 500 of logical organization of response data in data storage 230 . data storage 230 contains a set of response data records 510 , each response data record 510 consists of identifier 520 , area descriptor 530 , response data 540 . identifier 520 is used to uniquely identify a response data record . area descriptor 530 is used to approximate an area occupied by a visual icon using a rectangle . area descriptor is represented in a vector form ( p , x ′, y ′, l , w ), p denotes surface number , ( x ′, y ′) denotes coordinate of upper - leftmost point of said rectangle . l and h are the length and width of said rectangle , respectively . response data 540 is data that responds to user . when control unit 220 receives position ( x , y ) 323 of ultrasonic pointing unit 216 , control unit 220 finds a response data record 510 whose associated area descriptor 530 having said rectangle covers ( x , y ) 323 . if a response data record is found , then control unit 220 retrieves the corresponding response data 540 . control unit 220 processes retrieved response data 540 according to its type . for example , it could decode adpcm speech , mp3 music before direct them to audio output in response unit 240 . fig6 shows a regular surface 10 having a plurality of visual icons . area of each visual icon is approximated by a rectangle describing by a surface number p 11 , coordinate of upper - leftmost point ( x ′, y ′) 620 , length l 623 , width 626 . once a visual icon is pointed at using ultrasonic point unit 216 , the associated rectangle could thus be identified , and its associated response data 540 could be retrieved . thus , the use of present invention is intuitive , since it provides “ what you point is what you get ” capability . fig7 shows one embodiment 700 of response unit 240 . an audio circuit 713 drives a speaker 715 for audio output . control unit 220 implements audio driver software 711 to output audio response data to audio circuit 713 . a lcd driver circuit 723 drives a lcd for visual output . control unit 220 implements lcd driver software 721 to output visual response data to lcd driver circuit . a led driver circuit drives an array of leds . control unit 220 implements led driver software 731 to output visual response data . with the sound produced by speaker 715 , graphics or video shown on lcd 735 or flashing leds 735 , reading becomes an entertaining activity . fig8 shows the perspective view of an interactive book system 800 in accordance with present invention . interactive book system 800 includes a surface 201 . surface 201 consists of at least one regular surface 10 on which several graphics 13 and texts 16 are printed . interactive book system further includes an ultrasonic position determination device 210 ( not shown on this figure ). ultrasonic position determination device 210 further consists of an ultrasonic base unit 213 ( not shown here ) and an ultrasonic pointing unit 216 . ultrasonic pointing unit 216 has the shape of a pen , thus making it natural to use . ultrasonic base unit 213 further includes 2 ultrasonic transducers 310 . a and 310 . b . ultrasonic pointing unit 216 further includes an ultrasonic transducer 320 . interactive system book 800 further includes a memory card 850 where response data 500 is stored . memory card 850 is accessible by control unit 220 ( not shown on this figure ) to retrieve response data 540 . interactive system book 800 further includes a keypad 841 for user to enter surface number 11 , and a power switch 843 for turning on or off the system . interactive system book 800 further includes a response unit 240 ( not shown on this figure ) to respond to a user &# 39 ; s input . response unit 240 further consists of a speaker 715 , leds 735 , a lcd 725 . excluding surface 201 , interactive book system 800 could be made in a 6 ″× 3 ″× 2 ″ form , and it could work with surface 201 as large as 24 ″× 24 ″× 1 ″ ( e . g . a big book of maps ). unlike prior arts , it would impossible or very expensive to make a system with capabilities of present invention . fig9 is the open view 900 of interactive book system 800 . components are mounted on a pcb 910 . components invisible in fig8 are shown in this figure . micro controller 940 is used in control unit 220 . micro - controller 950 is used in ultrasonic position determination device . there are ics 961 for driving speaker , lcd and leds . and there is a connector 953 for memory card 850 . since the number of components of present invention is relatively small , so interactive book system 800 is relatively cheap to make . fig1 is the perspective view of one embodiment 1000 of an ultrasonic pointing unit 216 used in interactive book system 800 . embodiment 1000 is a pen like unit with a tip 1001 . once tip 1001 is pressed , interrupt 412 would be triggered . and pulses of 40 khz ultrasonic waves would be transmitted from ultrasonic transducer 320 . beam angle of ultrasonic transducer 320 is omni - directional , so embodiment 1000 could be used with ease without careful orientation toward ultrasonic transducers 310 . a , 310 . b of ultrasonic base unit 213 . embodiment 1000 further includes a cable 1003 connecting to micro - controller 410 . since embodiment 1000 is a pen like unit , so interactive book system 800 is natural and intuitive to use . fig1 shows one embodiment 1100 of logical organization of game rules . the games rules are a collection of game rule records 11110 . each game rule 11110 consists of game rule id 1120 , game 1130 and action 1140 . a game 1130 is a question 1150 and answer 1160 . in present embodiment , the system would ask user a question 1150 , then expect the right answer 1160 , then adding scores if the user answers correctly . in accordance with present invention , use of preferred embodiment 800 consists of following steps turn on power of system by using power switch 843 ; place a surface 10 ; enter a surface number 11 by using keypad 841 ; select a visual icon by using ultrasonic pointing unit 216 ; user would get immediate response corresponding to selected visual icon from speaker , leds or lcd . the system asks the user a question , then expects the user to answer the user answers the questions by pointing at a visual icon if the user answers correctly , the system would respond by adding a score or producing an encouraging sound . the use of preferred embodiment 800 is shown to be easy , intuitive . the additional sound or visual effects provided by present invention could help engage users to interact with a surface with visual icons 201 . it is particularly useful for language learning or storytelling , and make reading a more entertaining process . also , it could make a tradition r / c toy to interact on the surface . in accordance with present invention , principle of design and one preferred embodiment are shown in this chapter . it is clear that anyone skilled in the art would be readily to make different embodiments of present invention , thus the description herein should not be used to limit the scope of present invention .
a system for users to play games on regular surface such as printed material is provided . the system consists of an ultrasonic pointing unit , an ultrasonic base unit , a control unit and a response unit , together with response data and game rules . the user interacts with the surface by placing the ultrasonic pointing unit on various areas of the surface . ultrasonic wave propagates between the ultrasonic point unit and ultrasonic base unit . by measuring multiple time - of - flight of ultrasonic wave , the location of the ultrasonic pointing unit could be determined , and the device makes appropriate audio or other responses . also , with the additions of game rules , the system could ask users questions , or instruct users to tracing pictures or letters , or instruct users to walk a maze , etc . a surface is thereby transformed into an interactive experience with various sound or visual effects . the sound effects or other response data and game rules are stored in data storage accessible by the control unit . any number of different surfaces can be used as long as the specific response data for each different surface is stored in data storage accessible by the control unit .