Distance measuring apparatus

Claim 2

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; first distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means when said light projection means is used; second distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means when said light projection means is not used; first reliability discrimination means for discriminating reliability of the distance calculated by said first distance measuring means on the basis of a first reliability discrimination value; and second reliability discrimination means for discriminating reliability of the distance calculated by said second distance measuring means on the basis of a second reliability discrimination value.

Claim 3

The apparatus according to claim 1, wherein each of the first and second reliability discrimination values is a value indicating a degree of coincidence between the two signals output from said first and second light-receiving means.

Claim 4

The apparatus according to claim 2, further comprising: control means for, when said first reliability discrimination means determines that the distance calculated by said first distance measuring means has no reliability, calculating the distance to the object using said second distance measuring means.

Claim 5

The apparatus according to claim 3, further comprising: calculation means for, when said first and second reliability discrimination means determine that the two distances calculated by said first and second distance measuring means have no reliability, checking if the two calculated distances fall within a predetermined range, and for, when the two calculated distances fall within the predetermined range, calculating an average value of the two calculated distances as the distance to the object.

Claim 6

The apparatus according to claim 3, further comprising: selection means for, when said first and second reliability discrimination means determine that the two distances calculated by said first and second distance measuring means have no reliability, selecting one, having higher reliability, of the two calculated distances as the distance to the object.

Claim 7

The apparatus according to claim 3, further comprising: output means for, when said first and second reliability discrimination means determine that the two distances calculated by said first and second distance measuring means have no reliability, outputting a predetermined value as the distance to the object.

Claim 8

The apparatus according to claim 6, wherein the predetermined value represents infinity.

Claim 9

The apparatus according to claim 2, wherein said first and second distance measuring means include first and second filter means for respectively performing filter processing for the signals obtained by said first and second light-receiving means.

Claim 10

The apparatus according to claim 8, wherein said first filter means performs processing for attenuating a spatial frequency in a high-frequency region of the signals obtained by said first and second light-receiving means, and said second filter means performs processing for attenuating a spatial frequency in a low-frequency region of the signals obtained by said first and second light-receiving means.

Claim 11

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; first distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means when said light projection means is used; second distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means when said light projection means is not used; contrast calculation means for calculating contrast values of the signals obtained by said first and second light-receiving means; first contrast discrimination means for discriminating the contrast values calculated by said contrast calculation means on the basis of a first contrast discrimination value; and second contrast discrimination means for discriminating the contrast values calculated by said contrast calculation means on the basis of a second contrast discrimination value.

Claim 12

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; first distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means when said light projection means is used; second distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means when said light projection means is not used; contrast calculation means for calculating contrast values of the signals obtained by said first and second light-receiving means; first contrast discrimination means for discriminating the contrast values calculated by said contrast calculation means on the basis of a first contrast discrimination value; and second contrast discrimination means for discriminating the contrast values calculated by said contrast calculation means on the basis of a second contrast discrimination value.

Claim 13

The apparatus according to claim 10, further comprising: first reliability discrimination means for discriminating reliability of the distance calculated by said first distance measuring means on the basis of a first reliability discrimination value; and second reliability discrimination means for discriminating reliability of the distance calculated by said second distance measuring means on the basis of a second reliability discrimination value.

Claim 14

The apparatus according to claim 11, wherein each of the first and second reliability discrimination values is a value indicating a degree of coincidence between the two signals output from said first and second light-receiving means.

Claim 15

The apparatus according to claim 12, wherein when one of said first and second reliability discrimination means determines that the calculated distance has reliability, the contrast value is discriminated by one of said first and second contrast discrimination means.

Claim 16

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means; reliability discrimination means for discriminating reliability of the distance calculated by said distance measuring means on the basis of a reliability discrimination value; and changing means for changing the reliability discrimination value used in said reliability discrimination means.

Claim 17

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means; reliability discrimination means for discriminating reliability of the distance calculated by said distance measuring means on the basis of a reliability discrimination value; and changing means for changing the reliability discrimination value used in said reliability discrimination means.

Claim 18

The apparatus according to claim 14, wherein the reliability discrimination value is a value indicating a degree of coincidence between the two signals output from said first and second light-receiving means.

Claim 19

The apparatus according to claim 15, wherein said changing means changes the reliability discrimination value in accordance with a luminance of the signal.

Claim 20

The apparatus according to claim 15, wherein said first and second light-receiving means include: a plurality of sensor arrays each including an array of a plurality of sensors for receiving the reflected light; accumulation means for accumulating electric charges obtained from the plurality of sensors during ON and OFF periods of said light projection means; charge transfer means, at least a portion of which is connected in a ring shape, for transferring the electric charges accumulated by said accumulation means; and calculation means for calculating signal outputs from the plurality of sensors by adding signal electric charges from said accumulation means in synchronism with the charges which circulate the portion coupled in the ring shape and subtracting the charges obtained during the OFF period of said light projection means by said accumulation means from the charges obtained during the ON period.

Claim 21

The apparatus according to claim 17, wherein said changing means changes the reliability discrimination value in accordance with the number of rounds of charges which circulate.

Claim 22

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means; contrast calculation means for calculating contrast values of the signals obtained by said first and second light-receiving means; contrast discrimination means for discriminating the contrast values calculated by said contrast calculation means on the basis of a contrast discrimination value; and changing means for changing the contrast value used in said contrast discrimination means.

Claim 23

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of two signals output from said first and second light-receiving means; contrast calculation means for calculating contrast values of the signals obtained by said first and second light-receiving means; contrast discrimination means for discriminating the contrast values calculated by said contrast calculation means on the basis of a contrast discrimination value; and changing means for changing the contrast value used in said contrast discrimination means.

Claim 24

The apparatus according to claim 19, wherein said changing means changes the contrast discrimination value in accordance with a luminance of the signal.

Claim 25

The apparatus according to claim 20, further comprising: reliability discrimination means for discriminating reliability of the distance calculated by said distance measuring means on the basis of a reliability discrimination value, and wherein said changing means changes the contrast discrimination value used in said contrast discrimination means and the reliability discrimination value used in said reliability discrimination means in accordance with the luminance of the signal.

Claim 26

The apparatus according to claim 21, wherein the reliability discrimination value is a value indicating a degree of coincidence between the two signals output from said first and-second light-receiving means.

Claim 27

The apparatus according to claim 20, wherein said first and second light-receiving means include: a plurality of sensor arrays each including an array of a plurality of sensors for receiving the reflected light; accumulation means for accumulating charges obtained from the plurality of sensors during ON and OFF periods of said light projection means; charge transfer means, at least a portion of which is connected in a ring shape, for transferring the electric charges accumulated by said accumulation means; and calculation means for calculating signal outputs from the plurality of sensors by adding signal electric charges from said accumulation means in synchronism with the charges which circulate the portion coupled in the ring shape and subtracting the charges obtained during the OFF period of said light projection means by said accumulation means from the charges obtained during the ON period.

Claim 28

The apparatus according to claim 23, wherein said changing means changes the reliability discrimination value in accordance with the number of rounds of charges which circulate.

Claim 29

The apparatus according to claim 22, wherein said first and second light-receiving means include: a plurality of sensor arrays each including an array of a plurality of sensors for receiving the reflected light; accumulation means for accumulating electric charges obtained from the plurality of sensors during ON and OFF periods of said light projection means; charge transfer means, at least a portion of which is connected in a ring shape, for transferring the electric charges accumulated by said accumulation means; and calculation means for calculating signal outputs from the plurality of sensors by adding signal charges from said accumulation means in synchronism with the charges which circulate the portion coupled in the ring shape and subtracting the charges obtained during the OFF period of said light projection means by said accumulation means from the charges obtained during the ON period.

Claim 30

The apparatus according to claim 25, wherein said changing means changes the reliability discrimination value in accordance with the number of rounds of charges which circulate.

Claim 31

The apparatus according to claim 19, wherein said contrast calculation means includes attenuation means for attenuating high-frequency noise of the signals, and calculates the contrast values on the basis of the signals, noise of which is attenuated by said attenuation means.

Claim 32

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; electric charge accumulation means for accumulating signal charges output from said first and second light-receiving means; first distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of the signal electric charges accumulated in said electric charge accumulation means when said light projection means is used; second distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of the signal electric charges accumulated in said electric charge accumulation means when said light projection means is not used; setting means for independently setting a maximum accumulation time of the electric charges accumulated in said electric charge accumulation means in correspondence with said first and second distance measuring means; and control means for controlling said electric charge accumulation means in accordance with the maximum accumulation time set by said setting means.

Claim 33

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the reflected light received from the object; electric charge accumulation means for accumulating signal charges output from said first and second light-receiving means; first distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of the signal electric charges accumulated in said electric charge accumulation means when said light projection means is used; second distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of the signal electric charges accumulated in said electric charge accumulation means when said light projection means is not used; setting means for independently setting a maximum accumulation time of the electric charges accumulated in said electric charge accumulation means in correspondence with said first and second distance measuring means; and control means for controlling said electric charge accumulation means in accordance with the maximum accumulation time set by said setting means.

Claim 34

The apparatus according to claim 28, wherein each of said first and second light-receiving means includes a plurality of photoelectric conversion elements for receiving the reflected light, and signal electric charge supply means for accumulating signal charges output from the photoelectric conversion elements and transferring the signal charges in accordance with a predetermined charge transfer pulse, and said electric charge accumulation means includes a group of transfer electrodes formed, via a gate oxide film, on a plurality of charge transfer channels which are connected in a loop shape and transfer charges in a predetermined direction, a floating gate electrode portion formed via a gate oxide film to detect a signal charge amount transferred by the charge transfer channels, and signal charge injection means for injecting signal charges from said signal charge supply means into the charge transfer channels, and constitutes a circulating shift register for accumulating the signal charges injected by said charge injection means by injecting the signal charges from said signal charge supply means into the charge transfer channels via said signal charge injection means and circulating the signal charges in accordance with a charge transfer pulse applied to the transfer electrodes.

Claim 35

The apparatus according to claim 29, wherein said setting means sets a maximum number of times of accumulation of the signal charges in said circulating shift register as the maximum accumulation time.

Claim 36

The apparatus according to claim 29, wherein said setting means sets the maximum accumulation time for said second distance measuring means to be shorter than the maximum accumulation time for said first distance measuring means.

Claim 37

The apparatus according to claim 29, wherein said control means controls to discriminate reliability of a calculation result of said first distance measuring means, and to perform a distance measurement using said second distance measuring means in accordance with a discrimination result.

Claim 38

A distance measuring apparatus for measuring a distance to an object on the basis of reflected light from the object, comprising: light-receiving means including a plurality of photoelectric conversion elements for receiving the reflected light; A/D conversion means for A/D-converting signals from said light-receiving means; correction means for detecting a level variation in signal A/D-converted by said A/D conversion means, and correcting the A/D-converted signals on the basis of a detection result; and distance calculation means for calculating the distance to the object on the basis of the signals corrected by said correction means.

Claim 39

A distance measuring apparatus for measuring a distance to an object on the basis of reflected light from the object, comprising: light-receiving means including a plurality of photoelectric conversion elements for receiving the reflected light; A/D conversion means for A/D-converting signals from said light-receiving means; correction means for detecting a level variation in signal A/D-converted by said A/D conversion means, and correcting the A/D-converted signals on the basis of a detection result; and distance calculation means for calculating the distance to the object on the basis of the signals corrected by said correction means.

Claim 40

The apparatus according to claim 33, further comprising: light projection means for projecting signal light onto the object.

Claim 41

The apparatus according to claim 34, wherein said distance calculation means includes: first distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of the signals output from said light-receiving means when said light projection means is used; and second distance measuring means for calculating the distance to the object by performing a correlation calculation on the basis of the signals output from said light-receiving means when said light projection means is not used.

Claim 42

The apparatus according to claim 35, wherein when said distance calculation means executes one of said first and second distance measuring means, said correction means performs correction.

Claim 43

The apparatus according to claim 33, wherein said light-receiving means uses a skim CCD sensor.

Claim 44

The apparatus according to claim 33, wherein said correction means detects the level variation in signal using a plurality of empty transfer portions including no signals in said light-receiving means, and performs correction on the basis of a detection result.

Claim 45

A distance measuring apparatus which comprises light projection means for projecting light onto an object, and measures a distance to the object on the basis of light from the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the light received from the object; and distance measuring means for calculating the distance to the object on the basis of two signals output from said first and second light-receiving means, wherein said distance measuring means includes: discrimination means for discriminating, on the basis of the signals obtained by said first and second light-receiving means, whether or not a distance measurement performed by said distance measuring means is successful when said light projection means projects light; and phase difference detection means for detecting a phase difference between the signals obtained by said first and second light-receiving means without activating said light projection means in accordance with a discrimination result of said discrimination means.

Claim 46

A distance measuring apparatus which comprises light projection means for projecting light onto an object, and measures a distance to the object on the basis of light from the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the light received from the object; and distance measuring means for calculating the distance to the object on the basis of two signals output from said first and second light-receiving means, wherein said distance measuring means includes: discrimination means for discriminating, on the basis of the signals obtained by said first and second light-receiving means, whether or not a distance measurement performed by said distance measuring means is successful when said light projection means projects light; and phase difference detection means for detecting a phase difference between the signals obtained by said first and second light-receiving means without activating said light projection means in accordance with a discrimination result of said discrimination means.

Claim 47

The apparatus according to claim 39, wherein said discrimination means discriminates contrast by performing a predetermined calculation for each of the signals, and comparing a calculation result with a predetermined value.

Claim 48

The apparatus according to claim 39, wherein a distance measurement result is set to be a predetermined value when the discrimination result of said discrimination means indicates "NG".

Claim 49

The apparatus according to claim 39, wherein the distance measurement is performed by receiving the reflected light from the object without using said light projection means when the discrimination result of said discrimination means indicates "NG".

Claim 50

The apparatus according to claim 39, wherein said first and second light-receiving means include: a plurality of sensor arrays each including an array of a plurality of sensors for receiving the reflected light; accumulation means for accumulating electric charges obtained from the plurality of sensors during ON and OFF periods of said light projection means; charge transfer means; at least a portion of which is connected in a ring shape, for transferring the electric charges accumulated by said accumulation means; and calculation means for calculating signal outputs from the plurality of sensors by adding signal electric charges from said accumulation means in synchronism with the charges which circulate the portion coupled in the ring shape and subtracting the charges obtained during the OFF period of said light projection means by said accumulation means from the charges obtained during the ON period.

Claim 51

The apparatus according to claim 43, wherein each of said sensor arrays comprises a charge coupled device (CCD).

Claim 52

The apparatus according to claim 39, wherein said light projection means comprises one of a light-emitting diode (LED) and an infrared light-emitting element (IRED).

Claim 53

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: light-receiving means for outputting signals in accordance with an amount of the reflected light received from the object; distance measuring means for calculating the distance to the object on the basis of the signals output from said light-receiving means; first comparison means for comparing the distance calculated by said distance measuring means with a predetermined distance; second comparison means for, when said first comparison means determines that the calculated distance is smaller than the predetermined distance, comparing the received-light amount of said light-receiving means with a predetermined light amount; and correction means for, when said second comparison means determines that the received-light amount is smaller than the predetermined light amount, correcting the calculated distance to be a predetermined value.

Claim 54

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: light-receiving means for outputting signals in accordance with an amount of the reflected light received from the object; distance measuring means for calculating the distance to the object on the basis of the signals output from said light-receiving means; first comparison means for comparing the distance calculated by said distance measuring means with a predetermined distance; second comparison means for, when said first comparison means determines that the calculated distance is smaller than the predetermined distance, comparing the received-light amount of said light-receiving means with a predetermined light amount; and correction means for, when said second comparison means determines that the received-light amount is smaller than the predetermined light amount, correcting the calculated distance to be a predetermined value.

Claim 55

The apparatus according to claim 46, wherein said light-receiving means includes first and second light-receiving means.

Claim 56

The apparatus according to claim 47, wherein each of said first and second light-receiving means comprises a skim CCD sensor.

Claim 57

The apparatus according to claim 46, wherein said light-receiving element comprises a semiconductor position sensing element.

Claim 58

The apparatus according to claim 47, wherein said light-receiving element comprises a semiconductor position sensing element.

Claim 59

The apparatus according to claim 46, wherein the predetermined distance is a far distance.

Claim 60

The apparatus according to claim 46, wherein the predetermined distance is infinity.

Claim 61

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: light-receiving means for outputting signals in accordance with an amount of the reflected light received from the object; distance measuring means for calculating the distance to the object on the basis of the signals output from said light-receiving means; first comparison means for comparing the distance calculated by said distance measuring means with a predetermined distance; and second comparison means for, when said first comparison means determines that the calculated distance is smaller than the predetermined distance, comparing the received-light amount of said light-receiving means with a predetermined light amount, wherein when said second comparison means determines that the received-light amount is smaller than the predetermined light amount, said distance measuring means performs a distance measurement by receiving the reflected light from the object without using said light projection means.

Claim 62

A distance measuring apparatus which comprises light projection means for projecting signal light onto an object, and measures a distance to the object on the basis of reflected light obtained by projecting the signal light toward the object, comprising: light-receiving means for outputting signals in accordance with an amount of the reflected light received from the object; distance measuring means for calculating the distance to the object on the basis of the signals output from said light-receiving means; first comparison means for comparing the distance calculated by said distance measuring means with a predetermined distance; and second comparison means for, when said first comparison means determines that the calculated distance is smaller than the predetermined distance, comparing the received-light amount of said light-receiving means with a predetermined light amount, wherein when said second comparison means determines that the received-light amount is smaller than the predetermined light amount, said distance measuring means performs a distance measurement by receiving the reflected light from the object without using said light projection means.

Claim 63

The apparatus according to claim 53, wherein said light-receiving means includes first and second light-receiving means.

Claim 64

The apparatus according to claim 54, wherein each of said first and second light-receiving means comprises a skim CCD sensor.

Claim 65

The apparatus according to claim 53, wherein said light-receiving element comprises a semiconductor position sensing element.

Claim 66

The apparatus according to claim 54, wherein said light-receiving element comprises a semiconductor position sensing element.

Claim 67

The apparatus according to claim 53, wherein the predetermined distance is a far distance.

Claim 68

The apparatus according to claim 53, wherein the predetermined distance is infinity.

Claim 69

A distance measuring apparatus which comprises light projection means for projecting light onto an object, and measures a distance to the object on the basis of light from the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the light received from the object; and distance measuring means for calculating the distance to the object on the basis of two signals output from said first and second light-receiving means, wherein said distance measuring means includes: discrimination means for discriminating, on the basis of the signals obtained by said first and second light-receiving means, whether or not a distance measurement performed by said distance measuring means is successful; phase difference detection means for detecting a phase difference between the signals obtained by said first and second light-receiving means in accordance with a discrimination result of said discrimination means; and said first and second light-receiving means include: a plurality of sensor arrays each including an array of a plurality of sensors for receiving the light; accumulation means for accumulating electric charges obtained from the plurality of sensors during ON and OFF periods of said light projection means; charge transfer means, at least a portion of which is connected in a ring shape, for transferring the electric charges accumulated by said accumulation means; and calculation means for calculating signal outputs from the plurality of sensors by adding signal electric charges from said accumulation means in synchronism with the charges which circulate the portion coupled in the ring shape and subtracting the charges obtained during the OFF period of said light projection means by said accumulation means from the charges obtained during the ON period.

Claim 70

A distance measuring apparatus which comprises light projection means for projecting light onto an object, and measures a distance to the object on the basis of light from the object, comprising: first and second light-receiving means for respectively outputting signals in accordance with an amount of the light received from the object; and distance measuring means for calculating the distance to the object on the basis of two signals output from said first and second light-receiving means, wherein said distance measuring means includes: discrimination means for discriminating, on the basis of the signals obtained by said first and second light-receiving means, whether or not a distance measurement performed by said distance measuring means is successful; phase difference detection means for detecting a phase difference between the signals obtained by said first and second light-receiving means in accordance with a discrimination result of said discrimination means; and said first and second light-receiving means include: a plurality of sensor arrays each including an array of a plurality of sensors for receiving the light; accumulation means for accumulating electric charges obtained from the plurality of sensors during ON and OFF periods of said light projection means; charge transfer means, at least a portion of which is connected in a ring shape, for transferring the electric charges accumulated by said accumulation means; and calculation means for calculating signal outputs from the plurality of sensors by adding signal electric charges from said accumulation means in synchronism with the charges which circulate the portion coupled in the ring shape and subtracting the charges obtained during the OFF period of said light projection means by said accumulation means from the charges obtained during the ON period.

Claim 71

The apparatus according to claim 60, wherein each of said sensor arrays comprises a charge coupled device (CCD).