EPC635 datasheet(50/97 Pages) EPC

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DCS0: mga 0°, mgb 180°

mod_clk

led_mod

mga

mgb

DCS1: mga 90°, mgb 270°

mod_clk

led_mod

mga

mgb

LED

= 50ns

Figure 48: Sine mode 2x DCS modulation/demodulation waveforms

(mod_clk = 80MHz)

The first sample pair (DCS0 and DCS1) is enough to calculate 3D TOF distance for that pixel. The second pair (DCS2 and DCS3) can be

used for calculating the π-delay matching algorithm to compensate for fixed pattern noise and device mismatches during pixel readout op -

eration. The application SW must run the same algorithm on every pixel to compute the 3D TOF distance for the entire pixel-field.

Sine mode: Distance calculation algorithm

The use of the atan definition of the Cartesian coordinate system (atan2) guarantees a continuous distance calculation algorithm in the

range of phases between -π … +π. In our case, we use the range from 0º… 360º which corresponds to the distance from 0m up to the un-

ambiguity distance.

y-axis

x-axis

π/2

-π/2

-π

x / y

φ = atan2 (x , y) = atan2

)

Definition atan2 for the range -π … π

atan(y/x)

for x > 0

atan(y/x) + π

for x < 0, y ≥ 0

atan(y/x) - π

for x < 0, y < 0

atan2(x,y) :=

+π/2

for x = 0, y > 0

-π/2

for x = 0, y < 0

for x = 0, y = 0

Note: Variations in notation

φ = atan2(x , y ) or atan2(y, x)

The arguments are reversed depending on implementation.

Figure 49: Continuous atan representation for the range -π … +π

Let the respective 12 bit samples measured for a single pixel from 4 DCS (0, 1, 2, 3) frames be DCS0, DCS1, DCS2 and DCS3.

Thereof, the sampling of 4x DCS samples corresponds to the following sinusoidal signal representation for the epc635 chip:

tMOD

time

amplitude

time-of-flight

0°

90°

180°

270°

phase shift

DCS0

DCS1

DCS2

DCS3

sample

emitted AC signal

received AC signal

0°

Figure 50: Sampling of the received waveform

Characteristics subject to change without notice

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Datasheet_epc635-V1.02

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