JP2010107950A - Focus detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus detecting device which has a small number of parts and a simple configuration and is reduced in size and cost and capable of automatic focusing. <P>SOLUTION: The focus detecting device 100 is configured to include a reflecting optical element 20 having: a first reflecting surface 20a which is arranged on the side of a light source 10 for irradiating a target 60 with light and reflects the light from the light source 10, to guide it in an optical axial direction; and a second reflecting surface 20b which is arranged on the side of a photodetecting means 80 for detecting the displacement amount of the light reflected by the target 60 from an optical axis and reflects the light from the target 60, to guide it to the photodetecting means 80. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a focus detection apparatus.

  Conventionally, as a focus detection device used for an epi-illumination microscope, a method of projecting a point light source such as a laser diode or a slit pattern onto a test object and detecting a reflected image by a light receiving element is known ( For example, see Patent Document 1). A focus detection procedure in this conventional focus detection apparatus will be described with reference to FIG. The light beam emitted from the light source 1 is halved by the light shielding plate 2, converted into parallel light by the collimator lens 3, reflected by the half mirror 4, and then formed on the object 6 by the objective lens 5. is doing. The light reflected by the test object 6 passes through the objective lens 5 again, passes through the half mirror 4, and forms an image on the two-divided light receiving element 8 by the condenser lens 7. The two-divided light receiving element 8 detects the direction of defocus and the amount of deviation from the difference in the amount of incident light to the two light receiving areas 8a and 8b. The objective lens 5 or the test object 6 is moved in the direction of the optical axis based on the direction and amount of defocus to position the in-focus position.

U.S. Pat. No. 3,721,827

  However, such a focus detection apparatus has a problem that the manufacturing cost is high because the structure of the optical system is complicated, and the apparatus becomes large.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a focus detection apparatus that can achieve downsizing and cost reduction with a simple configuration.

  In order to solve the above-described problems, a focus detection apparatus according to the present invention is a light source for irradiating light to a test object, and a displacement amount from the optical axis of light reflected by the test object. Light detection means, a first reflection surface arranged on the light source side, reflecting the light from the light source and guiding it in the direction of the optical axis, and arranged on the light detection means side, reflecting light from the object to be detected and reflecting light And a reflecting optical element having a second reflecting surface that leads to the detecting means.

  In such a focus detection apparatus, the first reflection surface is a conic surface having a line passing through the light source as a rotation axis, and the second reflection surface is a conic surface having a line passing through the light detection means as the rotation axis. Is preferred.

  In such a focus detection apparatus, the first reflecting surface is on the light source and the optical axis and has an image point conjugate with the object to be examined as a focal point, and a rotation with a line connecting the two focal points as a rotation axis. The second reflecting surface, which is a part of the ellipsoid, is preferably a part of the ellipsoid having the image point and the light detection means as a focal point, and a line connecting the two focal points as a rotation axis.

  In such a focus detection apparatus, the first reflecting surface is a part of a rotating paraboloid having a light source as a focal point and a line passing through the focal point and parallel to the optical axis as a rotation axis. The reflecting surface is preferably a part of a paraboloid of revolution having a light detection means as a focal point and a line passing through the focal point and parallel to the optical axis as a rotation axis.

  Further, in such a focus detection apparatus, the first reflecting surface rotates on the light source and the optical axis, with the image point conjugate with the object to be detected as the focus, and with the line connecting the two focal points as the rotation axis. A part of the hyperboloid, and the second reflecting surface is preferably a part of a rotating hyperboloid having the image point and the light detection means as a focal point and a line connecting the two focal points as a rotation axis.

Further, in such a focus detection apparatus, the reflective optical element is disposed in a conjugate manner with the pupil plane of the objective lens for observing the object to be examined, the effective diameter of the reflective optical element is φ ₁ , and the pupil diameter of the objective lens is φ ₂ , where β is the magnification from the reflecting optical element to the pupil of the objective lens, φ ₂ = βφ ₁
It is preferable to be configured to satisfy the above condition.

  In such a focus detection apparatus, the first reflection surface and the second reflection surface are preferably semi-reflective surfaces that reflect a part of the light beam from the object to be measured and transmit the rest.

  At this time, the semi-reflective surface is preferably a polarization separation surface that reflects part of the semi-reflective surface according to the polarization characteristics of the light beam and transmits the remaining light.

  Alternatively, the semi-reflective surface is preferably a wavelength selection surface that reflects part of the light depending on the wavelength of the light beam and transmits the rest.

  Further, such a focus detection apparatus further includes a light source, a reflection optical element, and a holding member that holds the light detection means, and the coefficient of thermal expansion of the material constituting the holding member constitutes the reflection optical element. It is preferable to be approximately equal to the coefficient of thermal expansion of the material.

  When the focus detection apparatus according to the present invention is configured as described above, it is possible to achieve downsizing and cost reduction with a simple configuration with a smaller number of parts than in the past, and automatic focus adjustment is possible.

It is a lens block diagram which shows the structure of the focus detection apparatus which concerns on 1st Embodiment. It is explanatory drawing for demonstrating the structure of the reflective optical element in 1st Embodiment, (a) shows the front view, top view, and left and right side view of a reflective optical element, (b) is (a). FIG. 5C is a cross-sectional view taken along line H-H ′, and FIG. 5C is a perspective view of the reflective optical element. It is a lens block diagram which shows the structure of the microscope optical system which has the focus detection apparatus which concerns on 1st Embodiment. It is a lens block diagram which shows the structure of the other microscope optical system which has the focus detection apparatus which concerns on 1st Embodiment. It is a lens block diagram which shows the structure of what applied the focus detection apparatus which concerns on 1st Embodiment to a finite objective lens. It is a lens block diagram which shows the structure of the focus detection apparatus which concerns on 2nd Embodiment. It is explanatory drawing for demonstrating the structure of the reflective optical element in 2nd Embodiment, (a) shows the front view, top view, and left and right side view of a reflective optical element, (b) is (a). FIG. 5C is a cross-sectional view taken along line H-H ′, and FIG. 5C is a perspective view of the reflective optical element. It is a lens block diagram which shows the structure of the focus detection apparatus which concerns on 3rd Embodiment. It is a lens block diagram which shows the structure of what applied the focus detection apparatus which concerns on 3rd Embodiment to the optical system which projects a slit pattern. It is a lens block diagram which shows the structure of the focus detection apparatus which concerns on 4th Embodiment. It is a lens block diagram which shows the structure of the focus detection apparatus which concerns on 5th Embodiment. It is a lens block diagram which shows the structure of the focus detection apparatus which concerns on 6th Embodiment. It is explanatory drawing for demonstrating the structure of the reflective optical element in 6th Embodiment, (a) shows the front view of a reflective optical element, a top view, and the side view on either side, (b) shows (a). FIG. 5C is a cross-sectional view taken along line H-H ′, and FIG. 5C is a perspective view of the reflective optical element. It is a lens block diagram which shows the structure of what applied the focus detection apparatus which concerns on 6th Embodiment to the infinity objective lens. It is a lens block diagram which shows the structure of the focus detection apparatus which concerns on a prior art.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, the configuration of the focus detection apparatus according to the first embodiment will be described with reference to FIG. The focus detection apparatus 100 shown in FIG. 1 includes a light source 10 for irradiating a test object 60 with light, a reflection optical element 20, an objective lens 50, and an optical axis of light reflected by the test object 60. And a two-divided light receiving element 80 as a light detecting means for detecting the amount of displacement.

  The reflective optical element 20 is disposed on the light source 10 side, and is disposed on the first reflecting surface 20a that reflects light from the light source 10 and guides the light in the optical axis direction, and the two-divided light receiving element 80 side, and the object 60 to be inspected. And a second reflecting surface 20 b that reflects the light from the light and guides it to the two-divided light receiving element 80.

  As shown in FIG. 1, the light beam emitted from the light source 10 is reflected by the first reflecting surface 20 a of the reflective optical element 20, converted into parallel light, and enters the objective lens 50. The objective lens 50 according to the first embodiment is an infinite objective lens, and focuses the parallel light from the reflective optical element 20 on the object 60 to form a light source image. The light reflected by the test object 60 passes through the objective lens 50 again and becomes parallel light and enters the second reflecting surface 20b of the reflecting optical element 20. The light beam reflected by the second reflecting surface 20 b is condensed on the two-divided light receiving element 80. The two-divided light receiving element 80 has two adjacent light receiving regions 80a and 80b, and is arranged such that the boundary between the light receiving regions 80a and 80b is located on the optical axis of the focus detection apparatus 100. . Therefore, in the two-divided light receiving element 80, defocusing is caused by the difference in the amount of incident light on the two light receiving regions 80a and 80b (that is, the amount of deviation from the optical axis of the image of the light source 10 reflected on the object 60). The direction and the amount of deviation can be detected. The objective lens 50 or the test object 60 is moved in the direction of the optical axis based on the direction and amount of defocus to position the in-focus position.

FIG. 2 shows a detailed configuration of the reflective optical element 20 in the first embodiment. The reflection optical element 20 reflects the light from the light source 10 and guides it in the direction of the optical axis C, and the second reflection surface 20a reflects the light from the object 60 and guides it to the two-divided light receiving element 80. And a reflecting surface 20b. Here, the first reflecting surface 20a is a partial region of the rotating paraboloid Pa obtained by rotating the parabola around the straight line l ₁ passing through the light source 10 and parallel to the optical axis C as a rotation axis. The light source 10 is disposed at the focal point Fa of the paraboloid Pa. The reflecting surface 20b is a partial region of the rotating paraboloid Pb obtained by rotating the parabola with the straight line l ₂ passing through the two-divided light receiving element 80 and parallel to the optical axis C as the rotation axis. A two-divided light receiving element 80 is disposed at the focal point Fb of the surface Pb. With this configuration, the light beam emitted from the light source 10 can be converted into parallel light and guided in the direction of the optical axis C. Further, the light reflected by the test object 60 is collimated by the objective lens 50 and then condensed on the two-divided light receiving element 80.

  The reflective optical element 20 is made by vapor-depositing chromium or aluminum on a glass surface, formed by reflecting metal plate processing, cutting processing, etc., or vapor-depositing chromium or aluminum on the surface of a molded product made of a thermoplastic resin. It is preferable to use things. As described above, in the first embodiment, the reflection surfaces (20a, 20b) are provided on the outer surface, and the reflection optical element 20 of the outer surface reflection type is obtained.

  At this time, in order to prevent the focal planes of the reflecting surfaces 20a and 20b from being caused by thermal expansion of the material, the holding member (not shown) that holds the light source 10, the reflecting optical element 20, and the two-divided light receiving element 80 has a coefficient of thermal expansion. It is desirable that the material is substantially equal to the coefficient of thermal expansion of the material constituting the reflective optical element. That is, the size of the holding member is changed by the amount of change in the focal length of the reflecting surfaces 20a and 20b due to thermal expansion, so that the proportional enlargement is performed so as to maintain the conjugate relationship between the reflecting optical element 20 and the light source 10 and the two-divided light receiving element 80 By being configured so that the image is reduced, stable focus detection can be performed regardless of the temperature environment in which the apparatus is used.

  In the microscope optical system using an actual infinity objective lens, in addition to the focus detection device 100 described above, an enlarged image of the test object 60 by the objective lens and the second objective lens by light from the test object 60. And an observation optical system for observing the magnified image, and an observation illumination optical system for illuminating the object 60 to be examined. This will be described with reference to FIGS.

  3 constitutes the observation optical system 300 in addition to the optical system of the focus detection apparatus 100 shown in FIG. 1, and reflects a part of light and transmits the remaining light. The splitting mirror 40 and the second splitting mirror 41, the observation illumination optical system 200, and the second objective lens 70 are further provided. The observation illumination optical system 200 includes an observation light source 201 and a condensing lens 202. The light emitted from the observation illumination optical system 200 is reflected by the first split mirror 41 and the second split mirror 40, collected by the objective lens 50 onto the object 60 to be irradiated. The light reflected from the test object 60 is substantially collimated by the objective lens 50, reflected by the first split mirror 40, transmitted through the second split mirror 41, and the test object by the second objective lens 70. 60 enlarged images I are formed. The magnified image I is visually observed through an eyepiece (not shown), or captured by a two-dimensional image sensor (CCD or the like) not shown.

  Here, the first split mirror 40 for splitting the optical path of the observation optical system 300 and the optical path of the optical system of the focus detection apparatus 100 uses a dichroic mirror that selectively transmits or reflects light according to the wavelength of light. Is desirable. For example, when the wavelength of light emitted from the light source 10 is infrared light and the wavelength of light emitted from the observation light source 201 of the observation illumination optical system 200 is visible light, the first split mirror 40 is made visible light. By using a dichroic mirror that reflects infrared light and transmits infrared light, the optical path of the observation optical system 300 (visible light) and the optical path of the optical system of the focus detection apparatus 100 (infrared light) can be branched. Become.

  In the microscope optical system 500 shown in FIG. 3, the optical path reflected by the first split mirror 40 is the observation illumination optical system 200 and the observation optical system 300, and the optical path that is transmitted is the optical system of the focus detection apparatus 100. As in the microscope optical system 500 ′ shown in FIG. 4, the reflected optical path may be the optical system of the focus detection apparatus 100, and the transmitted optical path may be the observation illumination optical system 200 and the observation optical system 300.

  In the present embodiment, the objective lens 50 is an infinite objective lens. However, as shown in FIG. 5, the objective lens 50 can be applied to a finite objective lens. A focus detection apparatus 110 shown in FIG. 5 includes a light source 10, a reflective optical element 20, an objective lens 51, a split light receiving element 80, and a condenser lens 90.

  The light beam emitted from the light source 10 is reflected by the first reflecting surface 20 a of the reflective optical element 20 and converted into parallel light, and then enters the condenser lens 90. The condensing lens 90 is arranged so that its focal point is located at a point Fc on the image plane of the objective lens 51, and the parallel light incident on the condensing lens 90 is on the image plane of the objective lens 51 (point Fc). And an image of the light source 10 is formed. The objective lens 51 is a finite objective lens, and a light source image condensed on the image plane of the objective lens 51 is formed on the object 60 to be examined. The light reflected by the object to be examined 60 passes through the objective lens 51 again, is condensed once on the image plane (point Fc), and then converted into parallel light by the condenser lens 90 to be converted into the parallel light by the second reflective surface of the reflective optical element 20. 20b. The light beam reflected by the second reflecting surface 20 b is condensed on the two-divided light receiving element 80. The two-divided light receiving element 80 detects the direction and amount of defocus from the difference in the amount of incident light to the two light receiving regions 80a and 80b, and the objective lens 51 or the object to be tested is detected from the direction and amount of defocus. 60 is moved in the direction of the optical axis and positioned at the in-focus position.

(Second Embodiment)
Next, the configuration of the focus detection apparatus 120 according to the second embodiment will be described with reference to FIG. In FIG. 6 and subsequent drawings, the same reference numerals are given to components having the same functions as those of the focus detection apparatus 100 shown in FIG. 1, and detailed description thereof will be omitted. The focus detection apparatus 120 according to the second embodiment includes a light source 10, a reflective optical element 21, an objective lens 51, and a two-divided light receiving element 80.

  As shown in FIG. 6, the light beam emitted from the light source 10 is reflected by the first reflecting surface 21 a of the reflecting optical element 21, condensed on the image plane (point Fc) of the objective lens 51, and then the objective. The light enters the lens 51. The objective lens 51 according to the second embodiment is a finite objective lens, and condenses the light from the reflective optical element 21 on the test object 60 to form an image of the light source 10. The light reflected by the test object 60 passes through the objective lens 51 again, is condensed on the image plane of the objective lens 51, and then enters the second reflecting surface 21b of the reflecting optical element 21. Then, the light beam reflected by the second reflecting surface 21 b is condensed on the two-divided light receiving element 80. As described in the first embodiment, the two-divided light receiving element 80 detects the direction of defocus and the amount of deviation from the difference in the amount of incident light to the two light receiving regions 80a and 80b, and this defocus direction. Then, the objective lens 51 or the test object 60 is moved from the amount of deviation and positioned at the in-focus position.

FIG. 7 shows a detailed configuration of the reflective optical element 21 in the present embodiment. The reflective optical element 21 reflects the light from the light source 10 and guides it to the point Fc on the optical axis C, and reflects the light from the point Fc on the optical axis C to reflect the two-divided light receiving element. And a second reflecting surface 21 b led to 80. Here, the first reflecting surface 21a is an ellipsoid obtained by rotating an ellipse having the point Fa and the point Fc on the optical axis as focal points, and a line m ₁ passing through Fa and Fc as a rotation axis. The light source 10 is disposed at the focal point Fa of the spheroid ha, and the objective lens 51 is disposed such that the image plane is located at the point Fc. The second reflective surface 21b is the point Fb and the point Fc of the ellipse and the focal point, respectively, Fb, the line m ₂ passing through the Fc in partial regions of the spheroid hb obtained by rotating a rotation axis Thus, the two-divided light receiving element 80 is disposed at the focal point Fb of the spheroid ellipsoid hb, and the objective lens 51 is disposed such that the image plane is located at Fc. With this configuration, the light beam emitted from the light source 10 can be condensed on the point Fc on the image plane of the objective lens 51 as shown in FIG. Further, the light reflected by the test object 60 is condensed on the point Fc on the image plane by the objective lens 51 and then condensed on the two-divided light receiving element 80.

(Third embodiment)
Next, the configuration of the focus detection apparatus 130 according to the third embodiment will be described with reference to FIG. The focus detection device 130 in the third embodiment includes the light source 10, the reflective optical element 21, the objective lens 50, the two-divided light receiving element 80, and the condenser lens 90 shown in the second embodiment. . In the focus detection device 130, the condensing lens 90 is disposed so that the focal point thereof is located on the point Fc described in the second embodiment.

  As shown in FIG. 8, the light beam emitted from the light source 10 is reflected by the first reflecting surface 21a of the reflective optical element 21, condensed at the point Fc, and then converted into parallel light by the condenser lens 90. The light enters the objective lens 50. The objective lens 50 according to the third embodiment is an infinite objective lens, and condenses the parallel light from the condenser lens 90 on the test object 60 to form an image of the light source 10. The light reflected by the test object 60 passes through the objective lens 50 again, becomes parallel light, enters the condensing lens 90, and is condensed once at the point Fc, and then the second reflecting surface 21b of the reflecting optical element 21. Is incident on. The light beam reflected by the second reflecting surface 21 b is condensed on the two-divided light receiving element 80. The two-divided light receiving element 80 detects the direction of defocus and the amount of deviation from the difference in the amount of incident light to the two light receiving regions 80a and 80b, and the objective lens 50 or the object to be tested is detected from the direction and amount of defocus. 60 is moved in the direction of the optical axis and positioned at the in-focus position.

Here, the reflective optical element 21 according to the third embodiment is arranged in a conjugate manner with the pupil plane P of the objective lens 50 via the condenser lens 90, and the effective diameter of the reflective optical element 21 is φ ₁ . When the pupil diameter of the lens 50 is φ ₂ and the magnification from the reflective optical element 21 to the pupil plane P of the objective lens 50 is β, the following conditional expression (1) is generally satisfied.

φ ₂ = βφ ₁ (1)

  By disposing the reflective optical element 21 so as to satisfy this conditional expression (1), it becomes possible to make a necessary and sufficient light beam incident on the objective lens 50 as illumination light, and within the objective lens 50 that causes flare. It becomes possible to prevent irregular reflection. Further, since all the light beams emitted from the pupil of the objective lens 50 can be received regardless of the defocus, it is possible to configure the focus detection device 130 with a small decrease in the detected light amount even when the focus is deviated.

  Further, off-axis light from the light source 10 can be projected onto the test object 60 without any vignetting in the optical system. Therefore, for example, as shown in FIG. 9, the light source unit 10 ′ of the focus detection device 140 includes an illumination light source 11, a condenser lens 12, and a slit 13, and a slit pattern is projected onto the object 60 to be examined. It is suitable when doing.

(Fourth embodiment)
The configuration of the focus detection apparatus 150 according to the fourth embodiment will be described below with reference to FIG. The focus detection device 150 according to the fourth embodiment includes a light source 10, a reflective optical element 22, an objective lens 50, and a two-divided light receiving element 80. In addition, the reflective optical element 22 in the fourth embodiment is configured by a transparent body that transmits light having a wavelength emitted from the light source 10, and the reflective surfaces (22a, 22b) are provided on the inner side to provide internal reflection. These are different from the external reflection type reflective optical elements 20 and 21 of the first to third embodiments. The reflective optical element 22 has an interface 22c on the objective lens 50 side, an interface 22d on the light source 10 side, and an interface 22e on the two-divided light receiving element 80 side. The interface 22 c is a plane perpendicular to the optical axis C, the interface 22 d is a plane perpendicular to the optical path of the light source 10, and the interface 22 e is a plane parallel to the light receiving surface of the two-divided light receiving element 80.

  As shown in FIG. 10, the light beam emitted from the light source 10 enters the reflective optical element 22 from the interface 22d on the light source 10 side, is reflected by the first reflecting surface 22a and converted into parallel light, and then the objective lens. The reflective optical element 22 is emitted from the interface 22c on the 50 side. The parallel light emitted from the reflective optical element 22 enters the objective lens 50. The objective lens 50 according to the fourth embodiment is an infinite objective lens, and focuses the parallel light from the reflective optical element 22 on the test object 60 to form an image of the light source 10. Then, the light reflected by the test object 60 passes through the objective lens 50 again, becomes parallel light, enters the reflective optical element 22 again from the interface 22c, is reflected by the second reflecting surface 22b, and is divided into two parts. After the reflective optical element 22 is emitted from the interface 22 e on the element 80 side, the light is condensed on the two-divided light receiving element 80. The two-divided light receiving element 80 detects the direction of defocus and the amount of deviation from the difference in the amount of incident light to the two light receiving regions 80a and 80b, and the objective lens 50 or the object to be tested is detected from the direction and amount of defocus. 60 is moved and positioned at the in-focus position.

  The reflective optical element 22 according to the fourth embodiment is preferably a molded product made of a thermoplastic resin, and can be manufactured at low cost.

(Fifth embodiment)
Hereinafter, a fifth embodiment in which a focus detection device 150 ′ is inserted in the optical path of the observation optical system 310 will be described with reference to FIG. In the fifth embodiment, the focus detection device 150 ′ having the same configuration as that of the fourth embodiment is inserted into the optical path of the observation optical system 310, so that the size of the device can be reduced. In order to configure the observation optical system 310, in addition to the focus detection device 150 ', an optical element 23 formed of a transparent body and a second objective lens 70 are further provided.

  As for the focus detection device 150 ′ in the fifth embodiment, a part of the light incident on the first and second reflection surfaces 22a and 22b of the reflection optical element 22 in the fourth embodiment is used. Except that the reflective optical element 22 'is composed of first and second semi-reflective surfaces 22a' and 22b 'composed of semi-reflective surfaces that transmit light and reflect the rest. . For example, the wavelength of light emitted from the light source 10 is infrared light, and the first and second semi-reflective surfaces 22a ′ and 22b ′ are wavelength selection surfaces that transmit visible light and reflect infrared light. Thus, the optical path (visible light) of the observation optical system 300 and the optical path of the optical system of the focus detection device 150 ′ can be branched.

  When the observation optical system 310 has such a configuration, as described in the fourth embodiment, the light (infrared light) emitted from the light source 10 is the first and second semi-reflective surfaces 22a ′ and 22b. The light is reflected by ′ and condensed on the two-divided light receiving element 80. On the other hand, light (visible light) from the test object 60 is substantially collimated by the objective lens 50, and then the reflection optical element 22 ′ (first and second semi-reflection surfaces 22 a ′ and 22 b ′) and the optical element 23. , And an enlarged image I of the test object 60 is formed by the second objective lens 70. This magnified image I is visually observed through an eyepiece (not shown).

  Here, the optical element 23 is used for the purpose of preventing the light beam of the observation optical system 300 from being refracted by the first and second semi-reflective surfaces 22a ′ and 22b ′ of the reflective optical element 22 ′. 'And the optical element 23 are made of materials having the same refractive index, and are joined by the first and second semi-reflective surfaces 22a' and 22b '. The interface 23c of the optical element 23 is a plane perpendicular to the optical axis C. With this configuration, the light from the objective lens 50 forms an enlarged image I by the second objective lens 70 without being refracted by the reflection optical element 22 ′ and the optical element 23.

  By adopting the configuration as shown in the fifth embodiment, the focus detection device 150 ′ can be arranged in the optical path of the observation optical system 310 for observing the object 60 to be examined. Can be realized.

  In the fifth embodiment, the first and second semi-reflective surfaces 22a ′ and 22b ′ formed on the reflective optical element 22 ′ are partially reflected according to the wavelength of incident light, The case where the remaining light is transmitted through the wavelength selection surface has been described. However, when the polarization state of the light emitted from the light source 10 and the polarization state of the light for forming the image of the test object 60 are different, these are used. The semi-reflective surfaces 22a 'and 22b' can be configured by a polarization separation surface that reflects part of the light and reflects the light depending on the polarization characteristics of the light incident on the surfaces.

(Sixth embodiment)
Next, the configuration of the focus detection apparatus 160 according to the sixth embodiment will be described with reference to FIG. The focus detection device 160 in the sixth embodiment includes the light source 10, the reflective optical element 24, the objective lens 51, and the two-divided light receiving element 80. The sixth embodiment is different in that the reflecting surfaces 21a and 21b of the reflecting optical element 21 in the second embodiment are changed from an ellipsoid to a hyperboloid. As a result, in the second embodiment, the point Fc (point on the image plane of the objective lens) on the optical axis C is a point connecting the real image of the light source, whereas in the sixth embodiment, it is shown in FIG. It becomes the point which connects a virtual image. Therefore, in the sixth embodiment, a space for forming a real image is not necessary, and there is an advantage that the focus detection device of the finite objective lens can be particularly downsized.

  As shown in FIG. 12, the light beam emitted from the light source 10 is incident on the objective lens 51 after being reflected by the first reflecting surface 24 a of the reflecting optical element 24. The objective lens 51 according to the sixth embodiment is a finite objective lens, and condenses the light from the reflective optical element 24 on the test object 60 to form an image of the light source 10. The light reflected by the test object 60 passes through the objective lens 51 again and enters the second reflecting surface 24b of the reflecting optical element 24. The light beam reflected by the second reflecting surface 24 b is condensed on the two-divided light receiving element 80. As described in the first embodiment, the two-divided light receiving element 80 detects the direction of defocus and the amount of deviation from the difference in the amount of incident light to the two light receiving regions 80a and 80b, and this defocus direction. Then, the objective lens 51 or the test object 60 is moved in the optical axis direction based on the amount of deviation, and positioning is performed at the in-focus position.

FIG. 13 shows a detailed configuration of the reflective optical element 24 in the present embodiment. The reflection optical element 24 collects light at the first reflection surface 24a that reflects light from the light source 10 and converts it into light equivalent to that emitted from the point Fc on the optical axis C, and the point Fc on the optical axis C. And a second reflecting surface 24 b that reflects the light to be guided to the two-divided light receiving element 80. Here, the first reflecting surface 24a is a rotating hyperboloid obtained by rotating a hyperbola with the point Fa and the point Fc on the optical axis as focal points, and a line n ₁ passing through Fa and Fc as a rotation axis. The light source 10 is arranged at the focal point Fa of the rotating hyperboloid ha, and the objective lens 51 is arranged so that the image plane is located at the point Fc. The second reflective surface 24b is to focus the point Fb and the point Fc, respectively, Fb, a partial area of the rotating hyperboloid hb obtained by rotating a line n ₂ through Fc as a rotation axis, A two-divided light receiving element 80 is disposed at the focal point Fb of the rotating hyperboloid hb, and the objective lens 51 is disposed such that the image plane is located at Fc. With this configuration, as shown in FIG. 12, the light beam emitted from the light source 10 can be converted into light equivalent to diverging from a point Fc on the image plane of the objective lens 51. Further, the light reflected by the object to be examined 60 becomes a light beam condensed at the point Fc on the image plane by the objective lens 51, is reflected by the second reflecting surface 24b, and is divided into two parts received in a conjugate manner with the point Fc. The light is condensed on the element 80.

  In the present embodiment, the objective lens 51 is a finite objective lens. However, as shown in FIG. 14, the objective lens 51 can also be applied to an infinity objective lens. A focus detection apparatus 170 shown in FIG. 14 includes a light source 10, a reflective optical element 24, an objective lens 50, a two-divided light receiving element 80, and condenser lenses 90 and 91. The light beam emitted from the light source 10 is reflected by the first reflecting surface 24 a of the reflective optical element 24 and then enters the condenser lens 91. The condensing lens 91 is arranged so that the point Fc forming the virtual image of the light source 10 and the point Fc ′ on the optical axis are conjugate, and the light beam incident on the condensing lens 91 is collected at the point Fc ′. Light and form a real image of the light source. The light beam condensed at the point Fc ′ by the condenser lens 91 is converted into parallel light by the condenser lens 90 and enters the objective lens 50. The objective lens 50 is an infinite objective lens, and condenses the parallel light from the condenser lens 90 on the test object 60 to form an image of the light source 10. The light reflected by the test object 60 again passes through the objective lens 50, becomes parallel light, enters the condenser lens 90, is condensed once at the point Fc ', passes through the condenser lens 91, and is reflected by the reflective optical element 24. Is incident on the second reflecting surface 24b. The light beam reflected by the second reflecting surface 24 b is condensed on the two-divided light receiving element 80. In the two-divided light receiving element 80, the direction of the focus shift and the shift amount are detected from the difference in the amount of incident light to the two light receiving regions 80a and 80b, and the objective lens 50 or the object to be tested is determined from the direction and the shift amount of the focus shift. 60 is moved in the direction of the optical axis and positioned at the in-focus position.

  As described above, the two reflecting surfaces formed on the reflecting optical element are the paraboloid of revolution shown in the first embodiment, the spheroidal surface shown in the second embodiment, or the sixth embodiment. Like a rotating hyperboloid, it can be constituted by a conic surface having a rotation axis that is a line passing through the light source 10 and the two-divided light receiving element 80.

10, 10 'Light source 20, 21, 22, 22', 24 Reflective optical element 50, 51 Objective lens 60 Test object 70, 90, 91 Condensing lens 80 Divided light receiving element (light detection means)
20a, 21a, 22a, 24a First reflective surface 22a 'First semi-reflective surface 20b, 21b, 22b, 24b Second reflective surface 22b' Second semi-reflective surface 100, 100 ', 110-170 Focus detection apparatus

Claims (10)

A light source for irradiating a test object with light;
A light detection means for detecting a displacement amount of the light reflected from the test object from the optical axis;
A first reflection surface disposed on the light source side, which reflects light from the light source and guides the light in an optical axis direction; and is disposed on the light detection means side, which reflects light from the object to be examined and transmits the light. And a reflective optical element having a second reflective surface leading to the detection means.   The first reflection surface is a conic surface having a line passing through the light source as a rotation axis, and the second reflection surface is a conic surface having a line passing through the light detection means as a rotation axis. Focus detection device. The first reflecting surface is a part of a spheroid having a focal point at an image point conjugate with the object to be examined on the light source and the optical axis, and a line connecting the two focal points as a rotation axis. Yes,
The focus detection apparatus according to claim 2, wherein the second reflection surface is a part of a spheroid with the image point and the light detection unit as a focal point and a line connecting the two focal points as a rotation axis. The first reflecting surface is a part of a rotating paraboloid with the light source as a focal point and a line passing through the focal point and parallel to the optical axis as a rotation axis.
3. The focus detection device according to claim 2, wherein the second reflection surface is a part of a rotating paraboloid having the light detection unit as a focal point and a line passing through the focus and parallel to the optical axis as a rotation axis. . The first reflecting surface is a part of a rotating hyperboloid having a focal point at an image point conjugate with the object to be examined on the light source and the optical axis, and a line connecting the two focal points as a rotation axis. Yes,
3. The focus detection apparatus according to claim 2, wherein the second reflection surface is a part of a rotation hyperboloid having the image point and the light detection unit as a focal point and a line connecting the two focal points as a rotation axis. The reflective optical element is disposed in a conjugate manner with the pupil plane of the objective lens for observing the test object, the effective diameter of the reflective optical element is φ ₁ , the pupil diameter of the objective lens is φ ₂ , and the reflective optics When the magnification from the element to the pupil of the objective lens is β, the following formula φ ₂ = βφ ₁
The focus detection apparatus according to claim 1, wherein the focus detection apparatus is configured to satisfy the following condition.   The said 1st reflective surface and the said 2nd reflective surface are semi-reflective surfaces which reflect a part of light beam from the said to-be-tested object, and permeate | transmit the remainder. Focus detection device   The focus detection apparatus according to claim 7, wherein the semi-reflective surface is a polarization separation surface that reflects a part of the semi-reflective surface according to a polarization characteristic of a light beam and transmits the remaining part.   The focus detection apparatus according to claim 7, wherein the semi-reflective surface is a wavelength selection surface that reflects part of the semi-reflective surface according to the wavelength of the light beam and transmits the rest.   It further has a holding member that holds the light source, the reflective optical element, and the light detection means, and the coefficient of thermal expansion of the material that constitutes the holding member is equal to the coefficient of thermal expansion of the material that constitutes the reflective optical element. The focus detection apparatus according to claim 1, which is substantially equal.

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