METHOD FOR ACQUISITION OF IMAGES BY A SPACE OR AIRBORNE OPTICAL INSTRUMENT WITH WIDE FIELD OF VIEW

• US 20170134671A1
• Filed: 11/07/2016
• Published: 05/11/2017
• Est. Priority Date: 11/06/2015
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: PIGOUCHE, Olivier, GAUCEL, Jean-Michel, LIOTARD, Arnaud
• Granted Patent: US 10,416,534 B2
• Time in Patent Office: Days
• CPC Class Codes: B64D 47/08 Arrangements of cameras
• CPC Class Codes: G01C 11/025 by scanning the object
• CPC Class Codes: G03B 15/006 Apparatus mounted on flying objects
• CPC Class Codes: G06T 1/0007 Image acquisition
• CPC Class Codes: G06T 2207/10032 Satellite or aerial image; Remote sensing
• CPC Class Codes: H04N 23/45 for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images
• CPC Class Codes: H04N 25/46 by combining or binning pixels
• CPC Class Codes: H04N 25/702 SSIS architectures characterised by non-identical, non-equidistant or non-planar pixel layout

Abstract

A method for the acquisition of images by a spacer airborne optical instrument, comprises the following steps: a) acquisition, by the instrument, of a first image having a first field of view including the projection on the ground of the optical axis of the instrument and delimited by a first field edge, the first image being sampled spatially with a first sampling step; b) acquisition, by the same instrument, of a second image having a second field of view not including the projection on the ground of the optical axis of the instrument and extending beyond the first field edge, the second image being sampled spatially with a second sampling step greater than the first sampling step. Space or airborne optical instruments and an image acquisition system for implementing the method are provided.

Claims

1. A method for acquisition of images by a space or airborne optical instrument, comprising the following steps:

a) acquisition, by means of said instrument, of a first image having a first field of view comprising the projection on the ground of the optical axis of the instrument and delimited by a first field edge, said first image being sampled spatially with a first sampling step;

b) acquisition, by means of this same instrument, of a second image having a second field of view extending beyond the first field edge, said second image being sampled spatially with at least one second sampling step, said or each said second sampling step being greater than said first sampling step.

2. The method according to claim 1, wherein the first sampling step is chosen so as to define a first Nyquist spatial frequency such that the modulation transfer function of the instrument, or a figure or merit proportional to said modulation transfer function, at said first Nyquist frequency is greater than or equal to a predefined threshold over all said first field of view;

and said or each said second sampling step is chosen so as to define at least one second Nyquist spatial frequency (such that said modulation transfer function, or said figure of merit, at said or at each said second Nyquist frequency, is also greater than or equal to said predefined threshold over all said second field of view.

3. The method according to claim 1, wherein said step b) comprises the following substeps:

b1) acquisition of said second image, sampled with a sampling step equal to that of said first image;

b2) downsampling of said second image.

4. The method according to claim 3, wherein said first and second images are acquired by means of pixelated sensors having pixels of the same dimensions, corresponding to the first sampling step, the downsampling of said second image being obtained by a post-acquisition signal processing.

5. The method according to claim 1, wherein said first and second images are acquired by means of pixelated sensors having pixels of different dimensions, the pixels of the sensor or sensors used for the acquisition of the second image having dimensions greater than those of the pixels of the sensor or sensors used for the acquisition of the first image, whereby the downsampling of said second image is obtained at the same time as the acquisition thereof.

6. The method according to claim 1, wherein said second field of view surrounds said first field of view.

7. The method according to claim 1, wherein said optical instrument is embedded on board a spacecraft and said steps a) and b) are implemented on board said spacecraft, the method also comprising a step of transmission to the ground of the samples forming said first and second images.

8. The method according to claim 7, also comprising the following steps, implemented on the ground:

c) upsampling of said second image with a third sampling step equal to said first sampling step,

d) obtaining, from the first image and from the upsampled second image, of a single image having a uniform sampling step and comprising a first region corresponding to said first image and a second region corresponding to the part of said second image which is not superimposed on said first image.

9. A space or airborne optical instrument for the acquisition of images, comprising:

an image-forming optical system;

a sensor or set of sensors for acquiring the images formed by said optical system; and

a processor for processing the images acquired by said sensor or set of sensors;

wherein these elements are configured to implement a method according to claim 1.

10. The instrument according to claim 9, wherein said sensor or sensors are of CMOS type and said processor is at least partly co-integrated with said or at least one of said sensors.

11. The space or airborne optical instrument for the acquisition of images for implementing a method according to claim 5, comprising:

an image-forming optical system; and

a set of pixelated sensors for acquiring the images formed by said optical system;

wherein;

these elements are configured to acquire, by means of one or more first sensors of said set, a first image having a first field of view comprising the projection on the ground of the optical axis of the instrument and delimited by a first field edge and, by means of one or more second sensors of said set, a second image having a second field of view extending beyond the first field edge; and

in that;

the pixels of the second sensor or sensors have dimensions greater than those of the pixels of the sensor or sensors used for the acquisition of the first image.

12. An image acquisition system suitable for implementing a method according to claim 1, wherein said optical instrument is embedded on board a spacecraft and said steps a) and b) are implemented on board said spacecraft, the method also comprising a step of transmission to the ground of the samples forming said first and second images, said system comprising:

a space or airborne optical instrument for the acquisition of images, comprising elements including;

an image-forming optical system;

a sensor or set of sensors for acquiring the images formed by said optical system; and

a processor for processing the images acquired by said sensor or set of sensors;

wherein said elements are configured to implement the method according to claim 1; and

a transmission device suitable for transmitting to the ground, samples forming a first image and a second image acquired by said instrument, said second image having a field of view extending beyond an edge of the field of view of the first image and being sampled spatially with at least one sampling step greater than that of the first image; and

a ground segment comprising a reception device suitable for receiving said samples and a data processing system suitable for;

upsampling said second image to a sampling step equal to that of the first image,

obtaining, from the first image and from the upsampled second image, a single image having a uniform sampling step and comprising a first region corresponding to said first image and a second region corresponding to the part of said second image which is not superimposed on said first image.