US-12622079-B2 - Optical element, image sensor and imaging device for wavwlength-dependent focusing of visible and near-infrared light

US12622079B2US 12622079 B2US12622079 B2US 12622079B2US-12622079-B2

Abstract

An optical element includes a transparent layer for covering a plurality of pixels each including a photoelectric conversion element, and a plurality of structure bodies arranged on the transparent layer or in the transparent layer in a plane direction of the transparent layer. The plurality of structure bodies is arranged in such a manner that, among incident light, first light having a wavelength in a near-infrared light region is condensed on a first pixel among the plurality of pixels, and light of a second color having a wavelength in a region outside the near-infrared light region is condensed on a second pixel.

Inventors

Masashi Miyata
Naru Nemoto
Fumihide KOBAYASHI
Toshikazu Hashimoto

Assignees

NTT, INC.

Dates

Publication Date: 20260505
Application Date: 20201130

Claims (8)

1 . An optical element, comprising: a transparent layer for covering a plurality of pixels each including a photoelectric conversion element; and a plurality of structure bodies arranged on the transparent layer or in the transparent layer in a plane direction of the transparent layer, wherein the plurality of structure bodies is arranged in such a manner that, among incident light, a first light having a wavelength in a near-infrared wavelength range is condensed on a first pixel among the plurality of pixels, and a second light of a second color having a wavelength outside the near-infrared wavelength range is condensed on a second pixel, and wherein the plurality of structure bodies is arranged to condense, onto a given pixel for a given color, a portion of the incident light having a wavelength range corresponding to the given color and incident on regions that face multiple pixels surrounding the given pixel.
2 . The optical element according to claim 1 , wherein each of the plurality of structure bodies is a columnar structure body having a refractive index higher than a refractive index of the transparent layer and giving an optical phase delay amount according to a cross-sectional shape to the incident light, and a cross-sectional shape of the plurality of structure bodies is set according to an optical phase delay amount distribution for achieving light condensation, and the plurality of structure bodies is arranged according to the optical phase delay amount distribution for achieving the light condensation.
3 . The optical element according to claim 1 , wherein a cross-sectional shape of each of the plurality of structure bodies is a four-fold rotationally symmetrical shape.
4 . An imaging element, comprising: the optical element according to claim 1 ; and the plurality of pixels covered with the transparent layer.
5 . The imaging element according to claim 4 , further including a filter layer provided between the plurality of pixels and the transparent layer.
6 . The imaging element according to claim 5 , wherein the filter layer is a near-infrared absorption filter provided only on the second pixel.
7 . An imaging device, comprising: the imaging element according to claim 6 ; and a signal processing unit configured to generate an image signal on a basis of an electric signal obtained from the imaging element.
8 . An optical element, comprising: a transparent layer for covering a plurality of pixels, each including a photoelectric conversion element; and a plurality of structure bodies arranged on the transparent layer or in the transparent layer in a plane direction of the transparent layer, wherein the plurality of structure bodies outputs a first light that has a wavelength in a near-infrared wavelength range among incident light, and outputs a second light of a second color having a wavelength outside the near-infrared wavelength range among the incident light, wherein the plurality of structure bodies is arranged to condense, onto a given pixel for a given color, a portion of the incident light having a wavelength range corresponding to the given color and incident on regions that face multiple pixels surrounding the given pixel.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a National Stage application under 35 U.S.C. § 371 of International Application No. PCT/JP2020/044561, having an International Filing Date of Nov. 30, 2020. The disclosure of the prior application is considered part of the disclosure of this application, and is incorporated by reference in its entirety into this application. TECHNICAL FIELD The present invention relates to an optical element, an imaging element, and an imaging device. BACKGROUND ART A general imaging device uses a lens optical system and a two-dimensional imaging element such as a charge coupled device (CCD) sensor or a complementary metal oxide semiconductor (CMOS) sensor to acquire a two-dimensional image including intensity information and color information of light from an imaging target. In recent years, there is an increasing demand for simultaneous imaging of images of near-infrared (NIR) light in addition to visible light (color information). Since the near-infrared imaging device can capture images at night, the near-infrared imaging device has attracted attention for applications such as in-vehicle cameras and monitoring cameras. Accordingly, as an imaging element that captures both color information of visible light and a near-infrared image, a configuration has been proposed in which four types of color filters obtained by adding NIR to red (R), green (G), and blue (B) are integrated on each pixel in order to acquire color information and NIR information. CITATION LIST Non Patent Literature Non Patent Literature 1: Takanori Kudo, Yuki Nanjo, Yuko Nozaki, Kazuya Nagao, Hidemasa Yamaguchi, Wen-Bing Kang, Georg Pawlowski, “PIGMENTED PHOTORESISTS FOR COLOR FILTERS”, Journal of Photopolymer Science and Technology, 1996, Vol. 9, No. 1, p. 109-119.Non Patent Literature 2: Monno, Yusuke, et al. “Single-Sensor RGB-NIR Imaging: High-Quality System Design and Prototype Implementation”. IEEE Sensors Journal 19.2 (2018):497-507. SUMMARY OF INVENTION Technical Problem However, in the conventional imaging element, there is a problem that the total amount of received light after filter transmission decreases due to absorption of light outside the transmission wavelength band by the color filter, and sensitivity is limited. Then, since a general color filter partially transmits light in the NIR wavelength region, in the conventional imaging element, in order to generate a color image, it is necessary to perform color calibration such as subtracting the NIR pixel value from the R, G, and B pixel values. The present invention has been made in view of the above, and an object of the present invention is to provide an optical element, an imaging element, and an imaging device capable of improving light receiving sensitivity with visible light and near-infrared light of incident light without causing light absorption. Solution to Problem In order to solve the above-described problem and achieve the object, an optical element according to the present invention includes a transparent layer for covering a plurality of pixels each including a photoelectric conversion element, and a plurality of structure bodies arranged on the transparent layer or in the transparent layer in a plane direction of the transparent layer, in which the plurality of structure bodies is arranged in such a manner that, among incident light, first light having a wavelength in a near-infrared light region is condensed on a first pixel among the plurality of pixels, and light of a second color having a wavelength in a region outside the near-infrared light region is condensed on a second pixel. Further, an optical element according to the present invention includes a transparent layer for covering a plurality of pixels each including a photoelectric conversion element, and a plurality of structure bodies arranged on the transparent layer or in the transparent layer in a plane direction of the transparent layer, in which the plurality of structure bodies outputs first light that is a wavelength in a near-infrared light region among incident light, and outputs light of a second color having a wavelength in a region outside the near-infrared light region among the incident light. Further, an imaging element according to the present invention includes the above-described optical element, and the plurality of pixels covered with the transparent layer. Further, an imaging device according to the present invention includes the above-described imaging element, and a signal processing unit configured to generate an image signal on a basis of an electric signal obtained from the imaging element. Advantageous Effects of Invention According to the present invention, light receiving sensitivity with visible light of incident light can be improved without causing light absorption. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side view illustrating a schematic configuration of an imaging device according to a first embodiment. FIG. 2 is a v