Filter for light receiving element, and light receiving device

• US 8,369,007 B2
• Filed: 09/09/2011
• Issued: 02/05/2013
• Est. Priority Date: 03/13/2009
• Status: Active Grant

• Current Assignee: Nalux Co., Ltd (Nalux Holdings Corp.)
• Original Assignee: Nalux Co., Ltd (Nalux Holdings Corp.)
• Inventors: Inoue, Yasuaki
• Primary Examiner(s): Lavarias, Arnel C
• Assistant Examiner(s): Washington, Tamara Y
• Application Number:
  US13/228,793
• Publication Number:
  US 20120019904A1
• Time in Patent Office: 515 Days
• Field of Search: 359/359, 359/360, 359/578, 359/723, 359885-891
• US Class Current: 359/350
• CPC Class Codes: G02B 5/208 for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
• CPC Class Codes: H01L 31/02162 for filtering or shielding light, e.g. multicolour filters for photodetectors
• CPC Class Codes: H01L 31/02325 the optical elements not being integrated nor being directly associated with the device

Abstract

A filter for a light receiving element, which can sufficiently eliminate disturbance due to sunlight and the like out of doors. The filter for a light receiving element according to one embodiment of the present invention is used for a light receiving element which receives signal light having a known spectral distribution. The filter for a light receiving element according to one embodiment of the present invention is configured so that when the energy density of the ambient light in the light receiving element is represented by N1 and the energy density of the signal light in the light receiving element is represented by N2, N1/(N2)² is minimized under constraints.

Claims

1. A filter for a light receiving element which receives signal light with a known spectral distribution

wherein when energy density of ambient light in the light receiving element is represented as N1 and energy density of signal light in the light receiving element is represented as N2, a ratio of an amount of light which passes through the filter to an amount of light which enters the filter is determined in a range from 70% to 87% such that N1/(N2)² is minimized while changing a ratio of an amount of light which passes through the filter to an amount of light which enters the filter by changing the transmittance versus wavelength characteristic of the filter.

2. A filter for a light receiving element according to claim 1, wherein the signal light is in the wavelength range of infrared light.

3. A filter for a light receiving element according to claim 2, wherein a light source of the signal light is a laser or a light emitting diode.

4. A filter for a light receiving element according to claim 1, wherein much of the ambient light is the sunlight.

5. A light receiving device which includes a lens optical system, a light receiving element and a filter for light receiving elements according to claim 1.

6. A distance measuring device which includes the light receiving device according to claim 5.

7. A method for producing a filter for a light receiving element which receives signal light with a known spectral distribution, the method comprising the steps of:

provisionally determining a transmittance versus wavelength characteristic of the filter;

determining N1 when energy density of ambient light in the light receiving element is represented as N1;

determining N2 when energy density of signal light in the light receiving element is represented as N2; and

obtaining N1/(N2)²;

minimizing N1/(N2)² while changing a ratio of an amount of light which passes through the filter to an amount of light which enters the filter by changing the transmittance versus wavelength characteristic of the filter.

8. A method for producing a filter for a light receiving element according to claim 7, wherein N1 is obtained based on a spectral distribution of ambient light and the transmittance versus wavelength characteristic of the filter and N2 is obtained based on the known spectral distribution of the signal light and the transmittance versus wavelength characteristic of the filter.