EPC635 datasheet(52/97 Pages) EPC

52 / 97 page

The quality indicator for the distance noise is the ratio of ambient-light EBW to the peak-to-peak value of modulated light ETOF PP (AMR). This

value may be calculated and used additionally to the above amplitude value if the respective application is subject to intense ambient light.

The peak-to-peak irradiance ETOF sine PP of the modulated signal at the surface of a pixel can be calculate out of the AC sensitivity STOF sine,

the used integration time tINT-TOF, the reference integration time tINT-REF-TOF and the peak-to-peak amplitude ATOF sine PP of the received modulat-

ed signal the following way:

[6]

ETOF sine PP

= STOF sine⋅

INT-REF-TOF

INT-TOF

⋅ATOF sine PP e.g.

TOF sine PP = 0.62

/mm

LSB

⋅

103

μ s

205

μ s

⋅1'000 LSB = 0.31μ W/mm

The formula to calculate the quality indicator “Ratio of ambient-light / modulated light” (AMR) is

[7]

AMR

[dB] = 20⋅ log

( EBW

TOFPP

)

e.g.

AMR

[dB] = 20⋅ log

(15.8μW/mm2

0.31

μ W/mm

) = 34dB

Refer for EBW to chapter 6.2. Grayscale mode.

This ratio is one of the influencing factors regarding the distance noise.

AMR value

Classification

Action

< 60 dB

excellent

No action necessary.

< 70 dB

sufficient

Is a lower noise level needed, do the next measurement with a longer integration time or with an in-

creased illumination power.

> 70 dB

weak

Do the next measurement with a longer integration time or with an increased illumination

power.

Table 29: Classification ratio ambient-light to modulated light (AMR) versus distance noise

There are also validity indicators delivered by the chip after a measurement. These will help to detect saturated or not illuminated pixels as

a result of too much/less illumination or too long/short integration time.

Validity indicator (per pixel)

Classification

Action

Saturation flag:

= set

Pixel saturation:

The pixel receives too much light (too much modulated

light-signal, too reflective object or too much ambi-

ent-light)

Refer to chapter 5.7.3. Pixel saturation detection and

pin XSYNC_SAT_CFG.

Dump data and repeat the measurement

with a decreased integration time or mea-

sure the ambient-light.

one or more of the DCSx values:

| DCSx | > 2'000 LSB

DCSx value over maximum signal limit:

The object is too reflective( It is too close to the sensor,

there is too bright illumination or too much modulation

signal is emitted)

Dump data and repeat the measurement

with a decreased integration time.

all DCSx values:

| DCSx | ≤ 25 LSB

DCSx values below noise level limit:

Absence of an object in the operating range.

The object has too little remission (reflectivity): It is too

far away, the illumination is too dim or too little modula-

tion signal is emitted)

Dump data and repeat the measurement

with an increased integration time.

Table 30: Validity indicator versus classification

Characteristics subject to change without notice

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