an embodiment of a filmless dental radiography system according to the present invention is depicted in fig1 . as can be seen , the system includes an electronic sensor 1 , including a connector 1a , a remote board 2 and a computer 4 , with the remote board 2 and the computer 4 being connected through the computer &# 39 ; s usb port 4a . the electronic sensor 1 may comprise a ccd , an aps array or some other solid state device capable of converting electromagnetic radiation into electrical signals . the electronic sensor 1 might also comprise on top of the ccd , aps array or other solid state device a scintillator layer which converts x - rays into visible light . the computer 4 may be any conventional desktop , tower , laptop or notebook computer that is equipped with a usb port 4a and a corresponding usb channel . in addition to the usb port 4a , the computer 4 is equipped with various known software modules that support the usb channel , such as usb host controller software , and a known usb hardware interface . the computer 4 is either connected to or has built in one or more input devices , such as a keyboard 5 and a mouse 6 , and one or more output devices , such as a monitor 7 and a printer 8 . these devices allow the user to control the operation of the system , and to view the dental images that the system creates . the computer might also include or be connected to some type of storage device ( not shown ), such as a hard drive , for permanent storage of the images in patient files . image data flows from the electronic sensor 1 to the usb port 4a through the remote board 2 . the remote board 2 and usb port 4a are physically connected through a standard usb cable 3 which includes a usb plug 3a that couples with the usb port 4a . the usb cable 3 , illustrated schematically in fig2 is a four - wire bi - directional cable that includes a power line v , a data plus line d +, a data minus line d - and a ground line gnd . this cable carries serial image data from the remote board 2 to the usb port 3a , and also carries serial control instructions from the usb port 3a to the remote board 2 , such as for example tokens broadcasted by the usb host controller software . one preferred embodiment of the remote board 2 present invention is depicted in fig3 . in this preferred embodiment , the remote board 2 includes all of the processing circuitry necessary to , among other things , effect x - ray signal integration by the electronic sensor 1 ; read - out analog data from the electronic sensor 1 at the high rate required for a scientific sensor ; convert the analog data to digital data ; store that digital data ; process that data into a form suitable for transmission over the usb channel ; and transmit the processed data to the computer 4 via the usb port 4a at a rate slow enough for the usb channel to support . the remote board 2 also includes a power supply module that couples with the v and gnd lines of the usb to receive power and provide the appropriate voltages to the electronic sensor 1 and the other components on the remote board 2 . the core of the remote board 2 in this preferred embodiment is a reduced instruction set computer ( risc ) chip 31 . an example of an appropriate risc chip is the sl11 - r - usb controller ( manufactured by scanlogic corporation , 4 preston court , bedford , mass . 01730 , http //: www . scanlogic . com ), a 48 mhz , 16 - bit risc with a built - in 3k × 16 bios mask rom , a 1 . 5 k × 16 internal sram , a 2 mbyte sram / dram memory interface port , a 12 mbps ( 1 . 5 mbps ) usb port , an 8 - or 16 - bit direct memory access ( dma ) or input / output ( i / o ) port , a serial eeprom ( seeprom ) interface and four high - speed pulse width modulation or programmable output channels . the full description of the sl11 - r - usb risc can be found in the &# 34 ; sl11r / sl16 / sl11p2usb / sl08 / slepp2usb hardware specification ,&# 34 ; published by scanlogic corporation . under the control of firmware specific to the type of electronic sensor that the system incorporates , the risc chip 31 receives signals from and interfaces with the usb host controller software , and produces signals that control all aspects of the electronic sensor &# 39 ; s operation , including data read - out and x - ray signal integration . the remote board 2 includes two memory blocks -- a random access memory dram 38 for storing the image data read - out of the sensor and a read - only memory seeprom 39 for storing system initialization programs , test programs , usb support programs and configuration data . dram 38 may be accessed by the risc chip 31 either via software or via dma . a complex programmable logic device ( cpld ) 32 decodes signals from risc chip 31 to provide specific control signals to electronic sensor 1 and to other components on the remote board 2 . more particularly , cpld 32 generates digital signals that are provided to a digital - to - analog converter ( dac ) 34 , which dac 34 in turn converts those digital signals into analog voltages suitable for effecting x - ray signal integration by and read - out of electronic sensor 1 . these analog voltages are provided to electronic sensor 1 via a buffer 35 . the analog data read - out of electronic sensor 1 are provided to an input filter 36 ( which may be , for example , a fourth - order bessell low - pass filter ), and from there to analog - to - digital converter ( adc ) 37 . adc 37 , under the control of cpld 32 , converts the analog data retrieved from electronic sensor 1 into digital data that can be processed by risc chip 31 . to ensure that the data corresponding to a captured image is retrieved before a unacceptable amount of dark signal can accumulate , the reading - out of the sensor is performed at a relatively high rate , such as for example rates on the order of 1 mpps or more . these read - out rates , in conjunction with an adc of 16 -, 12 - or even 8 - bits , however , result in data transfer rates that are either close to or exceed the theoretical 1 . 5 mbps maximum bandwidth of the usb , and are therefore too fast for the usb to support . accordingly , the data retrieved from electronic sensor 1 are stored temporarily in dram 38 . after being stored in dram 38 , the data are read - out by risc chip 31 and assembled into a usb - compatible format . the risc chip 31 might also be programmed to perform other required or desirable processing operations as well , such as for example dark signal subtraction . the assembled and processed data are then transmitted under the control of risc chip 31 to the usb port 4a of the computer 4 . due to the bandwidth constraints of the usb , this transmission occurs at a rate slower than the rate at which the image data were read - out of electronic sensor 1 , and which the usb can comfortably support . for example , if the filmless dental radiography system is the only peripheral connected to the usb port 4a , the transfer will take place at rates on the order of 750 kilobytes per second ( kbps ). if on the other hand several peripherals are connected to the usb port 4a , such as via a hub , the data transfer will take place at rates slower than that . in any event , the rate of transfer of the data over to the usb port 4a will have no effect on the quality of the image , since the data is being not being read - out of the sensor at the slower rate , but rather out of the dram 38 . the unique approach of the present invention allows data to be read - out of the electronic sensor 1 at a fast rate to prevent the accumulation of an unacceptably high amount of dark signal , while at the same time exploiting the advantages of the computer &# 39 ; s usb without exceeding or straining its bandwidth limitations . it is to be understood that the above description and drawings are illustrative of the present invention and detail contained therein are not to be construed as limitations thereon . changes in components , procedure and structure may be made without departing from the scope of the present invention as defined in the following claims .
a filmless dental radiography system includes an intraoral sensor that outputs image data and a computer having a universal serial bus port that receives data . the image data output by the intraoral sensor are input to the computer through the universal serial bus port .