Data Sheet

ADPD2140

Rev. 0 | Page 9 of 12

OBJECT TRIANGULATION

While a single ADPD2140 allows for measurement of the x and

y coordinates of an object or light source, two ADPD2140 placed

at a distance apart can calculate the z distance using triangulation.

The superscripted A and B refer to ADPD2140 sensors that are

measured in Timeslot A and Timeslot B of the ADPD2140.

Calculate the triangulation distance z as follows:

2

)

–

(

B

A

y

y

C

z =

2

)

(

B

A

y

y

C

z

+

=

C is an empirically determined proportionality constant that

depends on the baseline distance between the two angle diodes,

which converts the x and y measurements to angles, in radians.

For reference, the baseline distance, c, between both angle diodes is

equal to 1” on the EVAL-ADPD2140Z evaluation board. This

quantity sets the units of the final distance measurement output.

Figure 12 shows the operation of a typical triangulation

measurement using the ADPD2140.

ADPD2140

TIMESLOT A

ADPD2140

TIMESLOT B

b

c

a

EMITTER

OBJECT

z

Figure 12. Triangulation Distance Measurement with the ADPD2140