■ Once, the cycle has started, it cannot be terminated until the end. All of the data except the “Saturated pixels” must be read before the

chip continues with the operation.

■ Do not change the type or the time commands during the sequence as they are not ignored and change the corresponding mode on the

fly (leading to data corruption).

1.3.2. Unambiguity range and integration time base

The epc610 3D TOF imager uses the time-of-flight principle. It is implemented with a repeating, continuous-mode modulation signal during

the measurement phase (refer to Figure 15). Consequently, only signals returning within the maximum time slots can be detected unam-

biguously. This corresponds for the epc610 device to a maximum operating range of 15m @10MHz LED modulation frequency. Strongly

reflected signals outside of this range may therefore interfere with the measurement.

The LED modulation frequency defines the unambiguity distance, the resolution of the distance signal and the time base for the integration

time. It can be changed by the MOD_CLK_DIV value (refer to chapter 3.5.3.: Command: WRITE LED modulation clock) to adapt the chip

to customer's application needs. Table 6 lists as an example some values of the LED modulation frequencies in function of the unambigui -

ty distance, of the distance resolution and for the corresponding divider of the LED clock.

LED modulation

frequency

Unambiguity

distance

Distance

LED clock

divider

20 MHz

7.5 m

0.25 cm

1

0

divided by 2

10 MHz

15 m

0.50 cm

2

1

as per chapter 3.5.1.

5 MHz

30 m

1.00 cm

4

3

multiplied by 2

2.5 MHz

60 m

2.00 cm

8

7

multiplied by 4

1.25 MHz

120 m

4.00 cm

16

15

multiplied by 8

Table 6: LED modulation frequencies vs. unambiguity distance and integration time

1

Distance resolution for an typical output range e.g. 0 - 3'000d

2

Refer to chapter 3.5.3.: Command: WRITE LED modulation clock.

2

Refer to chapter 3.5.1.: Command: WRITE Integration time.

The result is only uniquely defined below the unambiguity distance. It is the limit of the maximum operational distance.

1.3.3. Sensitivity, integration time and operating range

The operational range of the complete system is limited by the sensitivity of the receiver as well as by the illumination power emitted by the

modulating light source (e.g. LED) for distances below the unambiguity distance.

Time

(peak-to-peak)

Light

Intensity

Figure 15: The light detected by the receiver

sponds to the integration time: The longer the integration time, the more sensitive the measurement.

measurement result) in the following way:

t

INT-REF-AC

t

INT-AC

e.g.

E

nW

/ cm

2

LSB

⋅

103

μ s

205

μ s

⋅1'000 LSB = 16 μ W/cm

2

Illumination power, remission of the object (reflectivity), sensitivity of the sensor together with the integration time are limiting the distance

operational range. For more detailed information, refer to epc's application note: AN02 Reflected power calculation.

It will probably not be possible to cover the full operational range within one integration time step due to the dynamic range of the re-

ceiver's electronics. The possibilities to extend the operating range or to influence the response time are:

■ to adapt the integration time correspondingly to the necessary sensitivity as demonstrated in Figure 16.

© 2014 ESPROS Photonics Corporation

Characteristics subject to change without notice

11 / 34

Datasheet epc610 - V1.7

www.espros.ch