Optical apparatus and beam splitter

• US 20050218297A1
• Filed: 05/31/2005
• Published: 10/06/2005
• Est. Priority Date: 02/19/2004
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Washisu, Koichi, Suda, Yasuo
• Granted Patent: US 7,112,779 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: G02B 27/143 using macroscopically faceted or segmented reflective surfaces
• CPC Class Codes: G02B 27/16 used as aids for focusing
• CPC Class Codes: G02B 7/34 using different areas in a pupil plane
• CPC Class Codes: G03B 17/18 Signals indicating condition of a camera member or suitability of light indicating depth of field G03B13/30
• 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: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof

Abstract

An optical apparatus is disclosed, which can take high-quality images by using light transmitted through a beam splitter. The optical apparatus comprises a light-receiving element and a beam splitter. The first surface of the beam splitter reflects part of incident light and transmits the other part of the incident light toward the light-receiving element. The second surface transmits other incident light other than the incident light to the first surface toward the light-receiving element. The transmittance of the second surface is set so that a light amount distribution on the light-receiving element may be substantially even in a case where the light is incident to the first and second surfaces from an object having a substantially even luminance.

Claims

1. An optical apparatus comprising:

a light-receiving element, which has sensitivity to light in a predetermined wavelength region; and

a beam splitter, which has an inclination angle with respect to an incident optical axis and includes a first surface and a second surface, the first surface reflecting part of incident light in the predetermined wavelength region and transmitting the other part of the incident light toward the light-receiving element, and the second surface being formed so as to be orthogonal to the incident optical axis and to contact with the first surface, and the second surface transmitting incident light in the predetermined wavelength region other than the incident light to the first surface toward the light-receiving element,

wherein the transmittance of the second surface for the predetermined wavelength region is set so that a light amount distribution on the light-receiving element may be substantially even in a case where the light from an object having a substantially even luminance is incident to the first and second surfaces.

2. The optical apparatus according to claim 1, wherein the first surface is a surface whose reflectance and transmittance for the predetermined wavelength region are substantially the same.

3. The optical apparatus according to claim 1, further comprising an optical low pass filter, which is disposed in place of the beam splitter,

wherein, in the predetermined wavelength region, an optical length for the light transmitted through the optical low pass filter is substantially the same as an optical length for the light transmitted through the beam splitter.

4. An optical apparatus comprising:

a light-receiving element, which has sensitivity to light in a predetermined wavelength region;

a beam splitter, which has an inclination angle with respect to an incident optical axis and includes a first surface and a second surface, the first surface reflecting part of incident light in the predetermined wavelength region and transmitting the other part of the incident light toward the light-receiving element, and the second surface being formed so as to be orthogonal to the incident optical axis and to contact with the first surface, and the second surface transmitting incident light in the predetermined wavelength region other than the incident light to the first surface toward the light-receiving element; and

a gain adjuster, which adjusts a gain to an output from the light-receiving element so as to make an output distribution after adjustment substantially even in a case where the light from an object having a substantially even luminance is incident to the first and second surfaces.

5. The optical apparatus according to claim 4, wherein the first surface is a surface whose reflectance and transmittance for the predetermined wavelength region are substantially the same.

6. The optical apparatus according to claim 4, further comprising an optical low pass filter, which is disposed in place of the beam splitter,

wherein, in the predetermined wavelength region, an optical length for the light transmitted through the optical low pass filter is substantially the same as an optical length for the light transmitted through the beam splitter.

7. An optical apparatus comprising:

a light-receiving element, which has sensitivity to light; and

a beam splitter, which has a first region and a second region, the first region including a beam splitting surface that reflects part of incident light and transmits the other part of the incident light toward the light-receiving element, and the second region transmitting incident light other than the incident light to the first region toward the light-receiving element,

wherein the transmittance of the second region is substantially the same as that of the first region.

8. The optical apparatus according to claim 7, wherein a neutral density filter is provided on at least one of the incident surface and the emergent surface in the second region.

9. The optical apparatus according to claim 7, wherein a focus detection unit is provided, which performs focus detection using the light reflected by the beam splitting surface.

10. A beam splitter comprising:

a first region, which includes a beam splitting surface that reflects part of incident light and transmits the other part of the incident light; and

a second region, which transmits incident other than the incident light to the first region,

wherein the transmittance of the second region is substantially the same as that of the first region.

11. The beam splitter according to claim 10, wherein a neutral density filter is provided on at least one of the incident surface and the emergent surface of the second region.

12. An optical apparatus comprising:

a light-receiving element, which has sensitivity to light; and

a beam splitter, which has a first region and a second region, the first region including a beam splitting surface that reflects part of incident light and transmits the other part of the incident light toward the light-receiving element, and the second region transmitting incident light other than the incident light to the first region toward the light-receiving element,

a processor, which performs image processing for making a luminance distribution of an image that is obtained using the light-receiving element substantially even in a case where the light from an object having a substantially even luminance is incident to the first and second regions.

13. The optical apparatus according to claim 12, further comprising a focus detection unit, which performs focus detection using the light reflected by the beam splitting surface.

14. An optical apparatus comprising:

a beam splitter, which has a first region and a second region, the first region including a beam splitting surface that reflects part of incident light and transmits the other part of the incident light toward the light-receiving element, and the second region transmitting incident light other than the incident light to the first region; and

a filter, which reduces the transmittance of the second region.

15. The optical apparatus according to claim 14, wherein the filter is a neutral density filter.

16. The optical apparatus according to claim 14, wherein a focus detection unit is provided, which performs focus detection using the light reflected by the beam splitting surface.

17. A beam splitter comprising:

a first region, which includes a beam splitting surface that reflects part of incident light and transmits the other part of the incident light toward the light-receiving element;

a second region, which transmits incident light other than the incident light to the first region; and

a filter, which reduces the transmittance of the second region.

18. The beam splitter according to claim 17, wherein the filter is a neutral density filter.