COLOR CAMERA

• US 20120075510A1
• Filed: 06/28/2011
• Published: 03/29/2012
• Est. Priority Date: 09/29/2010
• Status: Abandoned Application

• Current Assignee: Murakami Corporation
• Original Assignee: Murakami Corporation
• Inventors: SATO, Hidenori, TERADA, Yoshiyuki
• Application Number:
  US13/170,895
• Publication Number:
  US 20120075510A1
• Time in Patent Office: Days
• US Class Current: 348/273
• CPC Class Codes: G02B 26/007 the movable or deformable optical element controlling the colour, i.e. a spectral characteristic, of the light
• CPC Class Codes: G02B 5/281 designed for the infrared light
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: G03B 11/00 Filters or other obturators specially adapted for photographic purposes
• CPC Class Codes: G03B 7/08 Control effected solely on the basis of the response, to the intensity of the light received by the camera, of a built-in light-sensitive device
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof

Abstract

The present invention enables switching between bright-light shooting and low-light shooting with an infrared cut filter placed on an optical path. An optical system captures and focuses image light from a subject. The focused image light passes through a multilayer infrared cut filter placed on an optical path of the image light and forms an image on an imaging device. The imaging device has sensitivity to at least the visible to near-infrared region. The infrared cut filter is constructed by forming a multilayer dielectric film on a surface of a transparent substrate. The infrared cut filter has a cutoff wavelength near a boundary between the visible region and near-infrared region and is configured so as to have a high incident-angle dependence. An angle of the infrared cut filter with respect to an optical axis of the optical system is varied by an incident angle varying mechanism according to an amount of light on the subject, shifting the cutoff wavelength.

Claims

1. A color camera comprising:

an optical system adapted to focus image light from a subject;

an imaging device having sensitivity to at least the visible to near-infrared region and adapted to project an image focused by the optical system and thereby generate a video signal;

a multilayer infrared cut filter placed at any location on an optical path running from the subject to the imaging device, with a cutoff wavelength being set in the vicinity of a boundary between the visible region and the near-infrared region, and adapted to allow passage of the near-infrared region close to the boundary with the visible region when an incident angle is small and shift the cutoff wavelength toward shorter wavelengths with increases in the incident angle to decrease passage of the near-infrared region;

an incident angle varying mechanism adapted to vary the incident angle of the image light from the subject with respect to the multilayer infrared cut filter; and

a drive unit adapted to drive the incident angle varying mechanism according to the amount of light on the subject by an operator'"'"'s operation or automatically and thereby decrease the incident angle when an amount of light on the subject is small or increase the incident angle when the amount of light on the subject is large.

2. The color camera according to claim 1, wherein the drive unit comprises:

an electric drive source adapted to vary the incident angle by electrically operating the incident angle varying mechanism;

a light level detector adapted to detect the amount of light on the subject; and

a control unit adapted to automatically operate the electric drive source according to the amount of light detected by the light level detector and thereby decrease the incident angle when the detected amount of light is small or increase the incident angle when the detected amount of light is large.

3. The color camera according to claim 1, wherein the drive unit comprises a controller adapted to drive, when manually operated by an operator, the incident angle varying mechanism in mechanical response to the manual operation and thereby decrease the incident angle when the amount of light on the subject is small or increase the incident angle when the amount of light on the subject is large.

4. The color camera according to claim 1, wherein the drive unit comprises:

an electric drive source adapted to vary the incident angle by electrically operating the incident angle varying mechanism;

an operation signal output unit adapted to be operated by an operator and output an operation signal according to the operation by the operator.

a control unit adapted to operate the electric drive source according to the operation signal outputted from the operation signal output unit and thereby decrease the incident angle when the detected amount of light is small or increase the incident angle when the detected amount of light is large.

5. The color camera according to claim 1, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts 100 nm or more when the incident angle changes from 0°

to 60°

or vice versa.

6. The color camera according to claim 2, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts 100 nm or more when the incident angle changes from 0°

to 60°

or vice versa.

7. The color camera according to claim 3, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts 100 nm or more when the incident angle changes from 0°

to 60°

or vice versa.

8. The color camera according to claim 4, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts 100 nm or more when the incident angle changes from 0°

to 60°

or vice versa.

9. The color camera according to claim 1, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts toward a longer wavelength than 750 nm at an incident angle of 0°

, and shifts toward a shorter wavelength than 750 nm at an incident angle of 60°

.

10. The color camera according to claim 2, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts toward a longer wavelength than 750 nm at an incident angle of 0°

, and shifts toward a shorter wavelength

11. The color camera according to claim 3, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts toward a longer wavelength than 750 nm at an incident angle of 0°

, and shifts toward a shorter wavelength than 750 nm at an incident angle of 60°

.

than 750 nm at an incident angle of 60°

.

12. The color camera according to claim 4, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts toward a longer wavelength than 750 nm at an incident angle of 0°

, and shifts toward a shorter wavelength than 750 nm at an incident angle of 60°

.

13. The color camera according to claim 5, wherein the multilayer infrared cut filter has a property that a cutoff wavelength at a 50% transmittance shifts toward a longer wavelength than 750 nm at an incident angle of 0°

, and shifts toward a shorter wavelength than 750 nm at an incident angle of 60°

.