Bolometer circuitry and methods for difference imaging

Patent metadata

Field	Value
Publication number	US-9958332-B2
Application number	US-201715483655-A
Country	US
Kind code	B2
Filing date	Apr 10, 2017
Priority date	Oct 16, 2014
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

Various techniques are disclosed for bolometer circuits and related methods for thermal imaging in a difference domain, where each pixel value represents a difference in incident IR radiation intensity between adjacent bolometers. For example, a bolometer circuit may include an array of bolometers each configured to generate a pixel signal in response to a bias and incident infrared radiation. Each column of the bolometer array may comprise an amplifier, a first plurality of switches each configured to selectively provide a supply voltage to a respective one of bolometers of the each column, a second plurality of switches each configured to selectively route a difference of the pixel signals of a respective adjacent pair of the bolometers of the each column to an input of the amplifier, and a third plurality of switches configured to selectively provide a common voltage to a respective one of the bolometers of the each column.

First claim

What is claimed is:

1. A bolometer circuit, comprising:
an array of bolometers each configured to generate a pixel signal in response to a bias applied and incident infrared (IR) radiation received at the each bolometer, wherein each column of the array of bolometers comprises:
an amplifier having an input and an output,
a first plurality of switches each configured to selectively provide a supply voltage to a respective one of the bolometers of the each column,
a second plurality of switches each configured to selectively route a difference of the pixel signals of a respective adjacent pair of the bolometers of the each column to the input of the amplifier, and
a third plurality of switches each configured to selectively provide a common voltage to a respective one of the bolometers of the each column; and

a control circuit configured to generate control signals for the first, second, and third pluralities of switches to obtain, at the output of the amplifier of each column, a difference signal representative of the difference of the pixel signals for a selected adjacent pair of the bolometers of each column.

2. The bolometer circuit of claim 1 , wherein the control circuit is configured to generate the control signals to close one of the first plurality of switches, one of the second plurality of switches, and one of the third plurality of switches while opening the remainder of the first, second, and third pluralities of switches, such that biases are applied to the selected adjacent pair of the bolometers of each column and the difference signal for the selected adjacent pair is obtained at the output of the amplifier.

3. The bolometer circuit of claim 2 , wherein:
the control circuit is configured to repeat generating the control signals to sequentially obtain even difference signals for a first plurality of adjacent pairs of the bolometers of each column, the even difference signals corresponding to those difference signals that are obtained by subtracting the pixel signals of odd rows from the pixel signals of corresponding even rows in the first plurality of adjacent pairs of the bolometers; and
the control circuit is further configured to repeat generating the control signals to sequentially obtain odd difference signals for a second plurality of adjacent pairs of the bolometers of each column, the odd difference signals corresponding to those difference signals that are obtained by subtracting the pixel signals of even rows from the pixel signals of corresponding odd rows in the second plurality of adjacent pairs of the bolometers.

4. The bolometer circuit of claim 3 , wherein:
the control circuit is further configured to repeat generating the control signals to sequentially obtain additional even difference signals for the second plurality of adjacent pairs of the bolometers, the additional even difference signals corresponding to those difference signals that are obtained by subtracting the pixel signals of odd rows from the pixel signals of corresponding even rows in the second plurality of adjacent pairs of the bolometers; and
the control circuit is further configured to repeat generating the control signals to sequentially obtain additional odd difference signals for the first plurality of adjacent pairs of the bolometers, the additional odd difference signals corresponding to those difference signals that are obtained by subtracting the pixel signals of even rows from the pixel signals of corresponding odd rows in the first plurality of adjacent pairs of the bolometers.

5. The bolometer circuit of claim 3 , further comprising a processor configured to combine the even difference signals and the odd difference signals to generate a difference image comprising both even and odd rows of difference signals.

6. The bolometer circuit of claim 5 , wherein the processor is further configured to reconstruct the difference image into a direct image by cumulatively adding the difference rows of the difference image.

7. The bolometer circuit of claim 1 , wherein:
the input of the amplifier is a first input of the amplifier,
the output of the amplifier is coupled to the first input via a thermally shorted bolometer providing a temperature-compensated feedback resistance, thereby configuring the amplifier as a transimpedance feedback amplifier;
the bolometer circuit further comprises a variable voltage source configured to provide a reference voltage level to a second input of the amplifier; and
the biases applied to the bolometers are set in response to the reference voltage level.

8. The bolometer circuit of claim 7 , wherein the variable voltage source comprises a digital-to-analog converter (DAC) configured to generate the reference voltage level in response to bias adjustment bits.

9. The bolometer circuit of claim 7 , wherein:
the variable voltage source is configured to provide a plurality of voltage levels on corresponding plurality of output lines in response to bias adjustment bits; and
each column of the array of bolometers further comprises a multiplexer connected to the plurality of output lines of the variable voltage source and to the second input of the amplifier of the each column, the multiplexer being configured to pass a selected one of the plurality of voltage levels as the reference voltage level to the second input of the amplifier of the each column in response to offset adjustment bits.

10. The bolometer circuit of claim 1 , further comprising one or more rows of blind bolometers substantially shielded from the incident IR radiation, wherein:
the one or more rows of blind bolometers are selectively connectable to a corresponding one or more rows of the array of bolometers to provide a pixel signal representing a reference IR intensity level; and
the control circuit is further configured to generate additional control signals to selectively connect the one or more rows of blind bolometers to the corresponding one or more rows of bolometers to obtain corresponding one or more rows of reference measurement signals, the reference measurement signals representing differences between the pixel signals of the blind bolometers providing the reference IR intensity levels and the pixels signals of the corresponding bolometers.

11. The bolometer circuit of claim 1 , wherein:
a contact between the bolometers of each adjacent pairs of each column is shared; and
the second plurality of switches are configured to route the difference of the pixel signals from the shared contact to the input of the amplifier.

12. A bolometer circuit, comprising:
an array of bolometers each configured to generate a pixel signal in response to a bias applied and incident infrared (IR) radiation received at the each bolometer, wherein the array of bolometers comprises:
a plurality of amplifiers each having an input and an output,
a first plurality of switches each configured to selectively provide a supply voltage to a respective bolometer of the array of bolometers,
a second plurality of switches each configured to selectively connect a respective pair of bolometers in adjacent columns of the array,
a third plurality of switches each configured to selectively route a difference of the pixel signals of a respective pair of bolometers in adjacent columns of the array to the input of a corresponding one of the plurality of amplifiers, and
a fourth plurality of switches each configured to selectively provide a common voltage to a respective bolometer of the array of bolometers; and

a control circuit configured to generate control signals for the first, second, third, and the fourth pluralities of switches to obtain, at the outputs of the amplifiers, co

Assignees

• Flir Systems

Inventors

• Simolon Brian B
• Aziz Naseem Y
• Högasten Nicholas

Classifications

• G01J1/44

  Electric circuits {(for command of an exposure part G03B7/02)} · CPC title

• G01J2005/0077

  Imaging · CPC title

• G01J5/24 Primary

  Use of specially adapted circuits, e.g. bridge circuits · CPC title

• G01J2005/202

  Arrays · CPC title