MULTIBAND CAMERA, AND MULTIBAND IMAGE CAPTURING METHOD

• US 20130235256A1
• Filed: 11/07/2011
• Published: 09/12/2013
• Est. Priority Date: 11/16/2010
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Kodama, Kenichi
• Granted Patent: US 8,908,087 B2
• Time in Patent Office: Days
• US Class Current: 348/360
• CPC Class Codes: G01J 2003/1213 Filters in general, e.g. dichroic, band
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G02B 27/1013 for colour or multispectral image sensors, e.g. splitting an image into monochromatic image components on respective sensors spectral imaging systems G01J
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G03B 11/00 Filters or other obturators specially adapted for photographic purposes
• CPC Class Codes: G03B 17/02 Bodies

Abstract

A multiband camera comprises: a band-pass filter having four or more optical filters; a microlens array having arrayed microlenses; a photoelectric conversion element including a plurality of pixels; and a measurement unit for measuring spectral intensity. The multiband camera satisfies the expression below, where Pl is a pitch between the microlenses, Ps is a pitch between the pixels, n is a number of pixels corresponding to one microlens, u is an effective dimension in a prescribed direction of the pixels, t is a dimension in the prescribed direction of a real image that the band-pass filter forms on a plurality of two-dimensionally arrayed pixels, Na is a number of microlenses arrayed in the prescribed direction, L is a distance from an exit pupil to the microlens, and f is a focal length of the microlens.

$\left[\mathrm{Expression}14\right]$ $\begin{array}{cc}\left(1-\frac{f}{L}\right)n\mathrm{Ps}-\frac{3\mathrm{Ps}-u-t}{\mathrm{Na}}\le \mathrm{Pl}\le \left(1-\frac{f}{L}\right)\mathrm{nPs}+\frac{3\mathrm{Ps}-u-t}{\mathrm{Na}}& \end{array}$

Claims

1. A multiband camera for capturing an image of an image capture wavelength region in mutually different wavelength bands divided into four or more bands when capturing an image of a subject, comprising:

a band-pass filter that is disposed in a position of a pupil of an optical system and has four or more optical filters for respectively transmitting the wavelength bands divided into four or more bands;

a microlens array having two-dimensionally arrayed positive microlenses;

a photoelectric conversion element that is disposed in the vicinity of a focal point of the microlens array and is disposed in or proximal to a conjugate position with the band-pass filter, and includes a plurality of two-dimensionally arrayed pixels on which is incident a flux of light transmitted through the band-pass filter and guided by the microlens array; and

a measurement unit for measuring a spectral intensity of the flux of light from the subject based on a signal output from the pixels corresponding to the optical filters;

wherein;

the expression below is satisfied;

where Pl is a pitch in a prescribed direction between the microlenses of the microlens array;

Ps is a pitch in the prescribed direction between the pixels of the photoelectric conversion element;

n is a number of pixels in the prescribed direction corresponding to one of the microlenses;

u is an effective dimension in a prescribed direction of the pixels;

t is a dimension in a prescribed direction of a real image of the band-pass filter formed on the plurality of two-dimensionally arrayed pixels;

Na is a number of microlenses arrayed in a prescribed direction;

L is a distance from an exit pupil corresponding to the pupil to the microlens; and

f (<

<

L) is a focal length of the microlens.

2. The multiband camera according to claim 1, wherein a real image of the subject is formed on the microlens.

3. The multiband camera according to claim 1, wherein:

the pixels are rectangular; and

each of the optical filters of the band-pass filter also is rectangular, and the optical filters are disposed in an array adjacently without any light-blocking region to block light.

4. The multiband camera according to claim 1, wherein:

the pixels are rectangular;

each of the optical filters of the band-pass filter also is rectangular; and

the band-pass filter is disposed in an array with a light-blocking region for blocking light interposed between adjacent filters.

5. The multiband camera according to claim 1, wherein the photoelectric conversion element has an insensitive band that does not output an electrical signal even when a flux of light is incident between adjacent pixels.

6. The multiband camera according to claim 1, wherein the number of pixels of the photoelectric conversion element corresponding to one of the microlenses is an integer multiple of the number of the optical filters.

7. The multiband camera according to claim 1, wherein the optical system includes an imaging optical system for forming a first real image of the subject or a relay optical system for forming a second real image from the first real image of the imaging optical system.

8. The multiband camera according to claim 7, wherein the band-pass filter is disposed in the relay optical system.

9. The multiband camera according to claim 1, wherein a spacer having a thickness T satisfying the expression below is disposed between the microlens array and the photoelectric conversion element.

10. The multiband camera according to claim 1, further comprising a display unit for displaying the subject based on the signal output from the photoelectric conversion element.

11. The multiband camera according to claim 1, further comprising:

a pair of polarizers that are disposed on an optical axis connecting the subject and the photoelectric conversion element;

wherein;

at least one polarizer of the pair of polarizers is relatively rotatable around the optical axis.

12. The multiband camera according to claim 1, wherein adjustment is made so that the real image of the subject is formed on the microlens by moving only the lens closer to the subject relative to the pupil among the lenses constituting the optical system in the direction of the optical axis connecting the subject and the photoelectric conversion element.

13. A multiband image capturing method for capturing an image of a subject with a photoelectric conversion element comprising two-dimensionally arrayed pixels by way of a band-pass filter being disposed in a position of a pupil of an optical system and having optical filters corresponding to wavelength bands divided into four or more bands and by way of a microlens array for guiding a flux of light transmitted through the band-pass filter, comprising:

a preparation step for preparing the microlens array having the microlenses satisfying the expression below;

a sensitivity correction step for correcting a sensitivity for each of the pixels of the photoelectric conversion element;

an image capturing step for capturing an image of the subject with the photoelectric conversion element by way of the band-pass filter and the microlens array; and

a measurement step for measuring a spectral intensity of each of the divided wavelength bands based on a signal output upon image capturing being performed in the image capturing step.

14. The multiband image capturing method according to claim 13, further comprising, after the preparation step and before the sensitivity correction step:

a positional alignment step for performing positional alignment within the photoelectric conversion element plane between the microlens array and the photoelectric conversion element, so that a spot formed on the photoelectric conversion element by parallel light rays incident on a microlens positioned in the center of the microlens array in the prescribed direction is positioned in the center in the prescribed direction of the plurality of pixels of the photoelectric conversion element corresponding to the microlens positioned in the center of the microlens array in the prescribed direction.

15. The multiband image capturing method according to claim 13, further comprising a display step for displaying on a display unit the image of the subject or a spectrum of each portion of the image based on the signal output upon image capturing being performed in the image capturing step.