US-12616367-B2 - Optical system and inspection apparatus

US12616367B2US 12616367 B2US12616367 B2US 12616367B2US-12616367-B2

Abstract

An optical system is configured to guide light from a light source to a first target and a second target, and to guide first reflected light from the first target and second reflected light from the second target to an image sensor. The optical system includes a first optical element having a conical surface. An intermediate image is formed between the first optical element and each of the first target and the second target. The first reflected light and the second reflected light are guided to an imaging plane of the image sensor such that at least part of the first reflected light and part of the second reflected light overlap each other on the imaging plane.

Inventors

Hiroto Kano

Assignees

CANON KABUSHIKI KAISHA

Dates

Publication Date: 20260505
Application Date: 20230209
Priority Date: 20220218

Claims (14)

1 . An optical system comprising a first optical element having a conical surface, wherein the first optical element is configured to guide light from a light source to a first target and a second target, and to guide first reflected light from the first target and second reflected light from the second target to an image sensor, wherein an intermediate image is formed between the first optical element and each of the first target and the second target, and wherein the first reflected light and the second reflected light are guided to an imaging plane of the image sensor such that at least part of the first reflected light and part of the second reflected light overlap each other on the imaging plane.
2 . The optical system according to claim 1 , further comprising: a projection optical system configured to guide the light onto the first target and the second target; and an imaging optical system configured to guide the first reflected light and the second reflected light onto the image sensor, wherein the first optical element constitutes a part of the projection optical system and a part of the imaging optical system.
3 . The optical system according to claim 2 , wherein the imaging optical system includes a light shielding unit configured to shield part of at least one of the first reflected light and the second reflected light.
4 . The optical system according to claim 2 , wherein the imaging optical system includes a screen configured to diffuse the first reflected light and the second reflected light while maintaining a polarization state of each of the first reflected light and the second reflected light.
5 . The optical system according to claim 4 , wherein the imaging optical system includes a second optical element configured to guide light from the screen to the image sensor.
6 . The optical system according to claim 1 , further comprising an optical diaphragm, wherein the optical diaphragm has a rectangular or elliptical aperture, and wherein a longitudinal direction of the aperture is a direction from the first target to the second target.
7 . The optical system according to claim 6 , wherein the following inequality is satisfied: 1.8≤ Fo×β≤ 7.0 where Fo is a target-side effective F-number in the longitudinal direction, and β is a magnification.
8 . The optical system according to claim 6 , wherein the following inequality is satisfied: 20≤ L ×β/(2× Fo ) where Fo is a target-side effective F-number in the longitudinal direction of the optical system, β is a magnification, and L is the shortest distance from the intermediate image to a plane where the first target and second target are located.
9 . An inspection apparatus comprising: an image sensor; and an optical system, wherein the optical system includes a first optical element having a conical surface, wherein the first optical element is configured to guide light from a light source to a first target and a second target, and to guide first reflected light from the first target and second reflected light from the second target to an image sensor, wherein an intermediate image is formed between the first optical element and each of the first target and the second target, and wherein the first reflected light and the second reflected light are guided to an imaging plane of the image sensor such that part of the first reflected light and part of the second reflected light overlap each other on the imaging plane.
10 . The inspection apparatus according to claim 9 , further comprising a calculating unit configured to separate first image data corresponding to the first reflected light and output from the image sensor and second image data corresponding to the second reflected light and output from the image sensor.
11 . The inspection apparatus according to claim 10 , wherein the calculating unit separates the first image data and the second image data based on a polarization state of each of the first reflected light and the second reflected light.
12 . The inspection apparatus according to claim 9 , wherein the image sensor receives the first reflected light and the second reflected light from the first target and the second target disposed at positions conjugate with the intermediate image.
13 . The inspection apparatus according to claim 9 , wherein the first target and the second target are a left eyeball and a right eyeball, respectively, and wherein the image sensor simultaneously receives the first reflected light and the second reflected light.
14 . The inspection apparatus according to claim 9 , further comprising a calculating unit, wherein the first target and the second target are a left eyeball and a right eyeball, respectively, and wherein the calculating unit detects a fixation state of each of the left eyeball and the right eyeball.

Description

BACKGROUND Technical Field One of the aspects of the disclosure relates to an optical system and an inspection apparatus. Description of the Related Art It is known that the fovea (a dent or depression at the center of the macula of a retina in an eye) is a place where the best vision is obtained because the retinal cones are particularly concentrated this neurosensory region. It is also known that a position where a test subject (test person) is gazing for visual fixation is measurable by detecting the birefringence states of neurons around the fovea. U.S. Pat. No. 10,188,293 discloses an inspection apparatus that includes a projection apparatus configured to project light onto the retina in the eye, and a light detector (sensor) configured to receive light reflected on the retina. Alight receiving surface of the light detector disclosed in U.S. Pat. No. 10,188,293 is located at a position conjugate with the retina and receives the light reflected on the retina of the eye. The inspection apparatus disclosed in U.S. Pat. No. 10,188,293 includes lenses disposed near an intermediate image in order to optically separate lights reflected on the retinas of both eyes. However, the optical system of the projection apparatus and the optical system that guides the reflected light to the optical detector are different, and thus this configuration needs to suppress a relative positional shift between the optical system of the projection apparatus and the optical system that guides the reflected light in order to prevent the detection accuracy from lowering. As a result, the inspection apparatus becomes complicated and large. SUMMARY One of the aspects of the disclosure provides an optical system and inspection apparatus, each of which is small and has a simple configuration. An optical system according to one aspect of the disclosure is configured to guide light from a light source to a first target and a second target, and to guide first reflected light from the first target and second reflected light from the second target to an image sensor. The optical system includes a first optical element having a conical surface. An intermediate image is formed between the first optical element and each of the first target and the second target. The first reflected light and the second reflected light are guided to an imaging plane of the image sensor such that at least part of the first reflected light and part of the second reflected light overlap each other on the imaging plane. An inspection apparatus having the above optical system also constitutes another aspect of the disclosure. Further features of the disclosure will become apparent from the following description of embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an optical path diagram of an optical system according to Example 1. FIG. 2 is a sectional view of the optical system according to Example 1. FIG. 3 is an optical path diagram to both eyes via the optical system according to Example 1. FIG. 4 is a sectional view of the optical system and detector according to Example 1. FIG. 5 is a sectional view of an optical system according to a first variation of Example 1. FIG. 6 is a sectional view of an optical system according to a second variation of Example 1. FIG. 7 is an example of a second optical system according to Example 1. FIG. 8 is a sectional view of an optical system according to Example 2. FIG. 9 is a sectional view of an optical system according to Example 3. FIG. 10 is a block diagram of an inspection apparatus according to each example. FIG. 11 illustrates a state on an imaging plane according to each example. DESCRIPTION OF THE EMBODIMENTS Referring now to the accompanying drawings, a detailed description will be given of embodiments according to the disclosure. An optical system according to each example is used, for example, as a projection optical system for an inspection apparatus (fixation measuring apparatus) that inspects a position where an eye of a subject is gazing (fixation state). As used herein, the term “gazing” describes an action to look steadily and intently at something or someone for at least a predetermined amount of time. A detailed description will be given of the configuration of the optical system according to each example. EXAMPLE 1 Referring now to FIGS. 1 and 2, a description will be given of an optical system OS1 according to Example 1. FIG. 1 is an optical path diagram of the optical system OS1 (optical path diagram from a reduction plane (object or light emitting plane) OP to an enlargement plane (target plane, projection plane) PP via the optical system OS1). FIG. 2 is a sectional view of the optical system OS1. The optical system OS1 includes, in order from the reduction plane (light emitting plane) OP to the enlargement plane PP, a lens L11, a reflective surface R1, a diaphragm (optical diaphragm, aperture stop) AP, a lens L12, and a lens L13. Light from the reduction p