Granted Patent B2

US 12,192,644 · App. 17/865,128 · Granted Jan 7, 2025

Inventors: Nikolai E. Bock (San Jose, CA); Andrew Kenneth John McMahon (San Carlos, CA); Dario Clocchiatti (Los Gatos, CA); Emanuele Mandelli (Mountain View, CA); Gennady A. Manokhin (Cupertino, CA); Robert H. Mullis (Santa Cruz, CA)

Assignee: Apple Inc.

H04N23/73G04F10/005H04N5/04H04N23/71G11C11/419H01L27/14634

Abstract

Claims (40)

1. A method of operation of a pulse-width modulation (PWM) image sensor, the method comprising:

during a detection period, receiving a number of photons at a PWM pixel of the PWM image sensor;

converting the number of photons into a photocurrent as the number of photons is received;

accumulating a number of electrons at a sense node during the detection period, the number of electrons accumulated in response to the sense node receiving the photocurrent;

during and in synchronization with the detection period, incrementing a count non-linearly, each value of the count synchronized with a non-linear time reference; and

when the accumulated number of electrons reaches a threshold number of electrons, latching a value of the count in a memory of a time-to-digital converter (TDC) circuit.

2. The method of claim 1 , wherein:

the value of the count is latched in the memory at a triggering time, the triggering time having a non-linear relationship with the photocurrent; and

as the triggering time increases, the count increments at a decreased rate.

3. The method of claim 1 , wherein the time reference, t, is defined by

t

=

2

b

*

t

min

2

b

-

n

,

where p is a bit depth or the TDC circuit, n is a counter step number, and t min is a counter delay.

4. The method of claim 3 , wherein the counter delay is further defined by

t

min

=

q

*

N

T

⁢

H

I

max

,

where q is an elementary charge, N TH is the threshold number of electrons, and I max is a maximum producible photocurrent.

5. The method of claim 1 , further comprising transmitting image information, corresponding to the latched value of the count in the memory of the TDC circuit, via a bi-directional bus.

6. The method of claim 1 , further comprising terminating a duration of the detection period in response to the photocurrent.

7. The method of claim 6 , wherein a higher photocurrent results in a shorter detection period and a lower photocurrent results in a longer detection period.

Assignments (1)

Continuity (2)

References Cited (400)