Electronic sensor with optimised counting capacity

• US 20080253498A1
• Filed: 04/04/2008
• Published: 10/16/2008
• Est. Priority Date: 04/06/2007
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Original Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Inventors: Dupont, Bertrand, Chamming's, Gilles, Villard, Patrick, Martin, Jean-Luc
• Granted Patent: US 7,702,062 B2
• Time in Patent Office: Days
• US Class Current: 377/19
• CPC Class Codes: G01J 5/24 Use of specially adapted circuits, e.g. bridge circuits

Abstract

Electronic sensor comprising at least:

• • capture means producing a signal s comprising x pulses during a given capture time, such that a′<x<b′, where a′, b′ and x are non-null natural integers,
  • counting means receiving the signal s, which are incremented with each pulse received, comprising a maximum counting capacity equal to z such that (b′−a′)≦z<a′, where z is a non-null natural integer, resetting the counting when the maximum counting capacity z is exceeded and outputting, at the end of the capture time, a number representative of the number of pulses x of the signal s.

Claims

1. Electronic sensor comprising at least:

capture means producing a signal s comprising x pulses during a given capture time, such that a′

<

x<

b′

, where a′

, b′ and

x are non-null natural integers,

counting means receiving the signal s, which are incremented with each pulse received, comprising a maximum counting capacity equal to z such that (b′

−

a′

)≦

z<

a′

, where z is a non-null natural integer, resetting the counting, when the maximum counting capacity z is exceeded and outputting, at the end of the capture time, a number representative of the number of pulses x of the signal s.

2. The sensor according to claim 1, the capture means comprising at least one bolometer whereby the signal s may be obtained.

3. The sensor according to claim 1, the counting means comprising at least one analogue counter.

4. The sensor according to claim 3, the analogue counter comprising at least one capacitor, where the maximum counting capacity z of the counting means is proportional to the value of the capacity of the capacitor, where the number output from the counting means is a voltage at the terminals of the capacitor.

5. The sensor according to claim 4, the analogue counter also comprising:

a comparator comprising a first input coupled to application means of a reference voltage, a second input coupled to the capacitor and an output coupled to a first input of an OR logical gate, a second input of the OR logical gate being intended to receive a counting reset signal,

a reset transistor of the capacitor wherein the grid may be coupled to the output of the OR logical gate,

a counting transistor wherein the drain is coupled to the second input of the comparator and the grid may be coupled to the input of the counting means.

6. The sensor according to claim 5, the analogue counter also comprising an inverter arranged between the output of the comparator and the first input of the OR logical gate.

7. The sensor according to claim 1, the counting means comprising at least one digital counter.

8. The sensor according to claim 7, the digital counter comprising k bits such that 2^k=z, k being selected such that m<

<

n, where;

m=n−

c,

where n is determined by the equation 2<sup>n−

1</sup>≦

(b+d)<

2ⁿ,

where c is determined by the equation

$2^c\le <br><br>\frac{2^n}{\left(b-a\right)+2<br><br><br><br>d}<<br><br>2^{c+1},$

where a, b, c, d, k, m and n are non-null natural integers, d corresponding to the variations in the number of pulses of ±

d due to technological dispersions of some components of the sensor, a=a′

+d and b=b′

−

d.

9. The sensor according to claim 1, the capture means comprising at least:

comparison means comprising a first input coupled to a capacitor, a second input coupled to application means of a reference voltage and an output whereon the signal s is output,

a recharging transistor wherein the grid may be coupled to the output of the comparator and the drain may be coupled to the first input of the comparator,

a selection transistor wherein the drain is coupled to the first input of the comparator, the source coupled to a variable load, a polarisation voltage applied to the selection transistor grid.

10. The sensor according to claim 9, the comparison means including a hysteresis comparator.

11. The sensor according to claim 9, the variable load being a thermistor, such as the bolometer when the capture means comprise a bolometer.

12. The sensor according to claim 9, the comparison means comprising a comparator followed by an inverter, the comparator receiving the reference voltage on its positive input, the grid of the PMOS transistor and the input of the counter being coupled to the output of the inverter.

13. The sensor according to claim 1, said sensor comprising a reading circuit of a bolometer.

14. Infrared image sensor, comprising a plurality of pixels, each pixel comprising at least one sensor according to claim 13.

15. Counting method of the number of pulses x of a signal s produced by an electronic sensor for a given capture time, such that a′

<

x<

b′

, where a′

, b′ and

x are non-null natural integers, comprising at least the following steps;

applying the signal s to an input of counting means comprising a maximum counting capacity equal to z such that (b′

−

a′

)≦

z<

a′

, where z is a non-null natural integer,

incrementing the counting means with each pulse received on the input and resetting the counting when the maximum counting capacity z is exceeded,

outputting from the counting means the number which is representative of the number of pulses x of the signal s.