JPH0460602A - Focus detector and observation device equipped with the same - Google Patents

Abstract

PURPOSE:To attain highly accurate focus position detection over a wide defocusing range wherein the quantity of defocusing is large by properly setting respective elements for making eccentric luminous flux incident on an image formation optical system and respective elements such as an auxiliary detector. CONSTITUTION:A light limiting member 91 has a reflecting surface which reflects reflected light from a surface to be inspected and directs it to a photodetector 7, the auxiliary photodetector 3 detecting part of the reflected light from the surface to be inspected which does not strike on the photodetector 7 by passing by the reflecting surface is arranged, and the position of the surface to be inspected in the direction of the optical axis 114 is adjusted according to the signal from this auxiliary photodetector 3. Then when a body 92 is large and in a defocusing state, a driving means 40 moves and adjusts the body 92 or image formation optical system 9 and then the reflected luminous flux from the body 92 is made incident on the photodetector 7, which outputs a specific difference signal. Consequently, the focus position of the image formation optical system 9 can be detected with high accuracy over the wide range.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a focus detection device and an observation device equipped with the focus detection device, and in particular, to a focus detection device and an observation device equipped with the focus detection device. The imaging optical system detects the incident position information on the detector surface of the luminous flux that passes through other areas of the imaging optical system among the reflected luminous flux from the object. The present invention relates to a focus detection device that detects the focus position of , and an observation device equipped with the focus detection device.

(Prior Art) Various types of focus detection devices that chargeably detect the focal position of an imaging optical system have been proposed.

For example, Japanese Patent Application Laid-Open No. 57-210308 proposes a so-called active type focus detection device in which a light beam is projected toward an object by a light projecting means and focus detection is performed using the light beam reflected from the object. Also, JP-A No. 57-72111 and JP-A No. 6
0-41013 and the like propose a passive focus detection device that performs focus detection using the imaging state of an object image formed by an imaging optical system. Also, JP-A-57-22
Publication No. 210 uses an active method, and at this time, the light beam is projected to the object side via an imaging optical system.
A focus detection device using a through-the-lens method has been proposed.

FIG. 5 is a schematic diagram of a main part of an optical system of a microscope equipped with a conventional active type focus detection device using a TTL type.

In the figure, reference numeral 1 denotes a light source for focusing, which is comprised of, for example, a laser diode, an LED (light emitting diode), or the like. A light beam from a light source 1 is condensed by a condenser lens 2. A part of the light beam condensed by the condenser lens 2 passes through the transmission surface 91a of the knife mirror 91, which has a reflection surface 91b on one side with respect to the optical axis and a transmission surface 91a on the other side. pass through. The light beam that has passed through the transmission surface 91a is reflected by the beam splitter 8 and enters the imaging optical system 9 as a light beam 18. The incident light flux to the imaging optical system 9 is a luminous flux whose principal ray is decentered with respect to the optical axis 114 of the imaging optical system 9 on the pupil plane 111, as shown in FIG. Area 112 (11
A light beam such as 3 passes through the inside (formed by the shape of the transmitting/reflecting surface of the knife mirror 91).

The light beam 18 that has passed through the imaging optical system 9 is projected onto an object 92 and forms a subo-soto image of the light emitting part of the light source 1 in the vicinity thereof. Of the luminous flux reflected by the object 92, the optical axis 1 at the time of projection is
The light beam 17 reflected along an optical path substantially symmetrical with respect to the optical path 14 passes through the imaging optical system 9 again. Then, it is reflected by the beam splitter 8, and the reflection surface 91b of the knife mirror 91 is reflected.
The light is reflected by the condenser lens 6 and is focused to form a spot image on the light receiving surface of the charge conversion element 7 for focus detection.

In the figure, the light source 1 and the object 92, and the object 92 and the photoelectric conversion element 7 are each in a substantially conjugate relationship with each other.

Reference numeral 10 denotes a television camera of the microscope, which is located at a substantially conjugate position with the object 92 through the imaging optical system 9, and observes the object 92. Now, when the object 92 is at the focused position 11 shown in FIG. 5, a light ray 104 as shown in FIG. 7 forms an image on the surface of the charge conversion element 7 as a good spot light. At this time, a steep intensity distribution as shown by a curve 101 shown in FIG. 7 is obtained from the photoelectric conversion element 7.

When the object 92 is at the front pin (rear pin) position 12 (13), a light ray 106 (105) as shown in FIG. 7 is incident on the surface of the photoelectric conversion element 7. Ray 1 at this time
06 (105) becomes a spot light that is spread out compared to the light ray 101, and from the charge conversion element 7 it spreads out like a curve 103 in the same figure, and the light beam 17 reflected from the object 92 or the optical axis 11
4, an intensity distribution shifted in the lateral direction from the intensity distribution due to the light ray 104 is obtained.

At this time, the amount of deviation of the incident light beam on the surface of the charge conversion element 7 and the amount of day focus from the focus position 11 of the object 92 are in a constant relationship. In the apparatus shown in FIG. 9, the focus of the imaging optical system 9 is detected by detecting the amount of deviation of the light intensity center of the light beam incident on the surface of the photoelectric conversion element 7 from a predetermined position.

That is, when a two-split sensor is used as the photoelectric conversion element 7 and the intensity distribution of the incident light beam is a curve 101, the output value from the left sensor 7a is A, and the output value from the right sensor 7b is A, as shown in FIG. The value is set to B so that the difference signal A-B between the output value A and the output value B becomes A-B=O.

FIG. 9 is an explanatory diagram showing the relationship between the day focus amount of the object 92 and the difference signal AB from the charge conversion element 7. That is, when object 92 is at position 12, the difference signal is A-
B>O1 When object 92 is at position 13, the difference signal is A-
B<O.

The focus detection device shown in FIG. 5 moves the imaging optical system 9 or the object 92 along the optical axis so that the difference signal A-B of the output signal from the photoelectric conversion element 7 or A-B=0. By moving the object 9, the object 9 is brought into focus on the imaging optical system 9.

(Problems to be Solved by the Invention) In the focus detection device shown in FIG. As shown in FIG. 7, the light beam 17 is at a distance β2·2 from the photoelectric conversion element 7.
- An image is formed on the point 105a in the front by about ΔX.

However, β is the paraxial lateral magnification when the object 92 is imaged onto the charging conversion element 7 side via the imaging optical system 9.

Here, if the object 92 is far away from the imaging optical system 9,
That is, as the day focus amount ΔX increases, the seventh
The distance β2·2·ΔX in the figure increases, and the reflected light beam 17 from the object 92 comes to be focused on a point 17a in front of the knife mirror 91, as shown in FIG. As a result, all of the reflected light beam 17 from the object 92 passes through the transmitting portion 91a of the knife mirror 91, is no longer reflected by the reflective surface 91b, and is no longer incident on the charge conversion element 7. At this time, the difference signal AB from the photoelectric conversion element 7 becomes AB=O as shown in FIG.

That is, when the day focus amount ΔX increases beyond a certain value ΔX MAX, the difference signal AB becomes AB=0, resulting in a problem that focus detection becomes impossible.

In the present invention, when an object is largely day focused, the driving means moves and adjusts the object or the imaging optical system, and the reflected light beam from the object enters the photodetector, and the photodetector outputs a predetermined difference signal. It is an object of the present invention to provide a focus detection device that can detect the focal position of an imaging optical system over a wide range with high accuracy.

(Means for Solving the Problems) A focus detection device of the present invention and an observation device equipped with the same include a light source, an objective optical system, and a light portion of the objective optical system that is blocked by blocking a portion of light from the light source. a light restricting member that directs a light beam eccentric with respect to the axis toward the objective optical system; and a photodetector that detects, via the objective optical system, reflected light from a test surface illuminated via the objective optical system. and detects a displacement of the surface to be measured in the direction of the optical axis based on a signal from the photodetector, wherein the light limiting member reflects the reflected light from the surface to be measured. an auxiliary photodetector having a reflective surface directed toward the photodetector, and detecting light that passes by the reflective surface and does not enter the photodetector among the reflected light from the test surface; , the position of the surface to be inspected in the direction of the optical axis is adjusted based on the signal from the auxiliary photodetector.

Further, the present invention includes a light source, an objective optical system, a light restriction member that extracts a part of the light from the light source and directs a light beam decentered with respect to the optical axis of the objective optical system to the objective optical system; and a photodetector that detects, via the objective optical system, reflected light from the surface to be inspected illuminated via the objective optical system. In the focus detection device that detects displacement in the direction of the optical axis, the light limiting member has a reflecting surface that reflects a part of the light from the light source and directs it toward the objective optical system, and Of the reflected light, the light that passes by the reflective surface is detected by the photodetector, and of the reflected light from the test surface, the light that is reflected by the reflective surface and does not enter the photodetector is detected. The present invention is characterized in that an auxiliary photodetector is arranged, and the position of the test surface in the direction of the optical axis is adjusted based on a signal from the auxiliary photodetector.

In addition, the present invention is characterized by having the following configuration.

(a) The light source includes a light emitting diode or a laser diode, and has a condenser lens that collects light from the light source, the light emitting diode, or the laser diode and directs it toward the light restriction member.

(b) The objective optical system includes an objective lens system that condenses the light beam from the light restriction member at a predetermined position, and the photodetector is configured to provide a relative relationship between the predetermined position and the test surface in the optical axis direction. The photodetector outputs a signal according to the displacement of the light, and the photodetector converts the light from the lens system to a lens system that collects the reflected light from the light restriction member and photoelectrically converts the light from the lens system to the incident position of the light. and a sensor that outputs a corresponding signal, and the objective optical system is configured such that the sensor and the predetermined position are optically conjugate, and/or the light emitting part of the light source and the predetermined position are optically conjugate. Having placed the system.

(c) An adjusting means is provided for adjusting the position of the test surface in the optical axis direction based on the signal from the photodetector and the signal from the auxiliary photodetector.

(d) The light restricting member has a transparent substrate and a reflective film formed on a part of the transparent substrate to constitute the reflective surface, and the transparent substrate is arranged at an angle with respect to the optical axis. , blocking light from the light source with the reflective film.

(*) The light restriction member has a transparent substrate and a reflective film formed on a part of the transparent substrate to constitute the above-mentioned reflective surface, and the transparent substrate is arranged at an angle with respect to the optical axis. and the photodetector detects reflected light from the test surface through a portion of the transparent substrate other than the reflective film.

(Embodiment) FIG. 1 is a schematic diagram showing a first embodiment of the focus detection device of the present invention, and shows how the focus detection device is mounted on a microscope.

The apparatus of this embodiment differs from the conventional focus detection apparatus shown in FIG. The photodetector 3 detects the light (light that does not enter the charge conversion element 7) that passes through the transmission surface 91a and is reflected by the reflection part 91b, out of the reflected light beam 17 that enters the knife mirror 91 from the beam splitter 8 side. are doing. The output signal from the auxiliary detector 3 at this time is input to the controller 4, and the object 92 is moved in the direction of the optical axis 114 of the imaging optical system 9 via the driving means 40 according to the command signal from the controller 4. move it. Thereby, the position of the object 92 is adjusted so that the reflected light beam (17) reflected from the surface of the object 92 is incident on the light receiving surface of the photoelectric conversion element 7.

In addition, the control aIJ device 4 controls the emission of light #1, and also responds to the output signal (A-B) from the charge conversion element 7 and manually inputs a predetermined signal to the drive means 40 to move the object. Imaging optics on the surface of 92,! It also operates to focus on -9.

Next, the configuration of the apparatus of this embodiment will be explained in sequence, although some parts overlap with the conventional focus detection apparatus shown in FIG.

In Fig. 1, ■ is the light source and the center wavelength λ. It consists of an LED (light emitting diode) that emits quasi-monochromatic light of wavelength λ. Monochromatic light or wavelength λ. It emits a beam of light that spreads around .

A condenser lens 2 condenses the light beam from the light source 1 and directs it toward the knife mirror 91. The condenser lens 2 is provided to efficiently direct the luminous flux from the light source 1 to the knife mirror 91, and also
The light-emitting section 92 forms an image of the light emitting section on the surface of the object 92 together with the imaging optical system. By exchanging the condenser lens 2, etc., the size of the image of this light emitting section (imaging magnification) can be adjusted.

The light restricting member 91 is composed of a knife mirror that has a reflecting part 91b on one side (upper side in the figure) and a light transmitting part 91a on the other side (lower side in the figure) with respect to the optical axis 114. ing. Reference numeral 8 denotes a beam splitter, which has a half mirror installed obliquely with respect to the optical axis 114. Naifetsuji Mirror 9
The light beam that passes through the light transmission section 91a of 1 and enters the beam splitter 8 is reflected by the beam splitter 8, and
The light enters the imaging optical system 9 as a light beam 18 . Imaging optical system 9
As shown in FIG.
1, the principal ray is a decentered light beam with respect to the optical axis 114 of the imaging optical system 9, and passes through a region 112 shown by diagonal lines on the pupil plane 111.

Thereafter, the light beam 18 exiting the imaging optical system 9 is directed to the object 92.
, and forms an image of the light emitting part of the light source 1 near the surface of the object 92. The reflected light beam reflected by the surface (test surface) of the object 92 travels in the opposite direction along an optical path that is approximately symmetrical with respect to the optical axis 114 and becomes a reflected light beam 17 and passes through the imaging optical system 9. pass again. The light is then reflected by the beam splitter 8, reflected by the reflecting portion 91b of the knife mirror 91, condensed by the condenser lens 6, and incident on the charging conversion element 7 for focus detection.

In the figure, when the surface of an object 92 is focused on the imaging optical system 9, the light emitting part of the light source 1 and the surface of the object 92, and the surface of the object 92 and the light receiving surface of the charge conversion element 7 are optically connected to each other. becomes conjugate to

10 is a television camera, and its imaging surface or imaging optical system 9
The focus detection device operates so as to be optically conjugate with the surface of the object 92 via the . Furthermore, this TV camera 10,
Observe object 92.

The imaging optical system 9 of this embodiment is an objective lens system of a microscope, and this lens system consists of a lens assembly including a plurality of lenses. Further, the photoelectric conversion element 7 is composed of a two-part sensor.

Further, as shown in FIG. 2, the knife mirror 91 has a reflective part 91b formed by forming a metal film such as Afl or AU on a part of a transparent substrate made of a glass plate, and the other part (metal The portion with no blank portion) is defined as a light transmitting portion 91a.

In FIG. 1, when the surface of the object 92 is at position 11, that is, the in-focus position, the reflected light beam 17 is reflected by the reflecting portion 91b of the knife mirror 91, and the photoelectric conversion element 7 A light beam 104 shown in FIG. 7 is incident on the light receiving surface of the light receiving surface, forming a clear light spot on the light receiving surface.

Also, when the surface of the object 92 is at position 12 (front pin),
Since the reflected light beam 17 comes to be focused behind the photoelectric conversion element 7, the reflected light beam 17 is reflected by the reflection part 91b of the knife mirror 91, and appears on the light receiving surface of the charge conversion element 7 as shown in FIG. The light beam 106 enters the light beam and forms a spread light spot on the light-receiving surface.

On the other hand, when the surface of the object 92 is at position 13 (rear focus) and the defocus amount ΔX is large, as shown in FIG.
As a becomes larger, β22・ΔX becomes larger. Therefore, as shown in FIG. 2, the reflected light beam 17 forms an image at a point 17b in front of the knife mirror 91, and then enters the knife mirror 91.

As described above, the reflected light beam 17 at this time does not enter the reflection part 91b of the knife mirror 91, or even if it does, the amount is small and the reflected light flux 17 enters the light transmission part 91a.
Almost all of 7 is now incident.

In other words, since almost none of the reflected light beam 17 enters the light receiving surface of the charge conversion element 7, the difference signal A-B from the charge conversion element 7 is always approximately A-B=O, which may lead to an error in the in-focus state. You will be able to get a signal.

Therefore, in this embodiment, as shown in FIG. A portion of the light beam 17 that has passed through 91a is detected. When the output value (signal level) corresponding to the intensity of the light received from the auxiliary light detector 3 is equal to or higher than a predetermined value, the controller 4 controls the object 92 to be greatly focused (
The controller 4 gives a predetermined command signal to the driving means 40, and the driving means 40 moves the object 92 on the optical axis in a direction toward the in-focus position 11 (imaging optical system 9).
direction).

FIG. 1O is an explanatory diagram showing the relationship between the day focus amount and the output value C from the auxiliary light detector 3.

In the same figure, day focus amount ΔX MAX (9th
(See figure) Day focus range ΔD
It is shown that an output signal C1 is obtained from the auxiliary photodetector 3 when the auxiliary photodetector 3 is within the range.

As described above, in this embodiment, when the surface of the object 92 is largely defocused in the rear focusing direction, a predetermined signal is obtained from the auxiliary light detector 3, and the controller 4 is controlled based on the output signal of the lever. By moving the object 92 by a predetermined amount along the optical axis 114 using the driving means 40, the object 92
The reflected light beam 17 from the surface of the mirror 91 is reflected by the reflecting portion 91b of the knife mirror 91 and is incident on the light receiving surface of the charge conversion element 7.

As a result, in the focus detection device of this embodiment, even if the object 92 is largely day-focused in the front focus direction or back focus direction, the reflected light beam 17 from the surface of the object 92 is incident on the photoelectric conversion element 7 surface. I'm trying to be able to do that.

According to this embodiment, even if the object 92 is day-focused over a wide range, the focal position can be detected accurately.

FIG. 3 is a flowchart showing the steps of a focus detection method using the focus detection device of this embodiment. The processing shown in the figure may be performed in a hardware manner by constructing an electric circuit, or may be performed in software by converting the output signals from the detectors 3 and 7 from analog to digital using a CPU.

In the above embodiment, when the output (light intensity) of the light source l is large and there is no need to increase the light utilization efficiency in the optical system,
The device can also be configured by removing the condenser lens 2 or by removing the condenser lens 2.6. Also in this case, when the surface of the object 92 is focused on the imaging optical system 9, this surface and
The light source 1 and the element 7 are arranged so that the light emitting part of the light W1 and the light receiving surface of the photoelectric conversion element 7 are conjugate with each other.

In the above embodiment, a two-split sensor was used as the charging conversion element 7, or a PSD sensor was used instead of this sensor.
(Position 5 sensitive detect
to), it is possible to use sensors such as one-dimensional or two-dimensional CCDs. Further, as the light source 1, a laser diode (semiconductor laser) can be used instead of an LED.

In the above embodiment, a half mirror 5 is arranged between the condenser lens 2 and the knife mirror 91 as shown in FIG. mirror 91
The light is guided to the transmitting section 91a of the beam splitter.
The reflected light beam 17 reflected by the half mirror 5 and passed through the transmission part 91a of the knife mirror 91 may be reflected by the half mirror 5 and made to enter the auxiliary light detector 3.

Furthermore, as shown in FIG. 11, the present invention is the same even if the system consisting of the light source 1, condenser lens 2, and auxiliary photodetector 3 is replaced with the system consisting of the condenser lens 6 and photoelectric conversion element 7. It can be used for buildings. In addition, Naifue Sosimilar-91 has a transparent substrate (as shown in Figure 2).
Al1. Although it can be constructed by forming a metal film such as Au, it is also possible to simply arrange a knife having a reflective surface on at least the surface on the side of the imaging optical system 9, as shown in FIG. In addition, when using the knife mirror 91 shown in FIG. 6, by appropriately setting the patterning shape of the reflective film, the pupil plane 111 of the imaging optical system 9 can be adjusted as shown in FIG. Partial circular area 11
It is also possible to allow the light beam 18 to pass only through the light beam 3.

In addition, in the present invention, focusing control on the test surface may be performed by moving the object up and down as in the above embodiment, but it is also possible to control the focus by moving the entire microscope up and down, or by moving a part of the optical system (for example, the objective lens) up and down. It is also possible to focus by moving the lens. Also,
The focus detection device of the present invention can be applied to optical instruments other than microscopes.

(Effects of the Invention) According to the present invention, each element for making an eccentric light beam incident on the imaging optical system and each element such as an auxiliary detector as described above when detecting the focal position of the imaging optical system. By appropriately setting , it is possible to achieve a focus detection device that can detect the focus position with high precision over a wide dayfocus range with a large dayfocus amount.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main parts of the optical system according to the first embodiment of the present invention, FIG. 2 is an explanatory diagram of the vicinity of the optical member in FIG. 1, and FIG. 3 is a flowchart of signal processing according to the first embodiment. FIG. 4 is a schematic diagram of the main parts of the optical system according to the second embodiment of the present invention, FIG. 5 is a schematic diagram of the main parts of a conventional focus detection device, FIG. 6 is an explanatory diagram of a part of FIG. 9 is an explanatory diagram of the light flux incident on the detector used in the focus detection device, FIG. 8 is an explanatory diagram of the light flux on the pupil plane of the imaging optical system of FIG. FIG. 10 is an explanatory diagram showing the relationship between the day focus amount and the output signal from the detector. FIG. 11 is a diagram showing a modified example of the real end side shown in FIG. 1, FIG. 12 is a diagram showing another example of the light restricting member, and FIG. 13 is a diagram showing another example of the light restricting member. FIG. 3 is an explanatory diagram of a light flux on a pupil plane of an imaging optical system. In the figure, 1 is a light source, 2 and 6 are condenser lenses, 3 is an auxiliary detector, 4 is a controller, 40 is a driving means, 5 is a half mirror, 17 is a detector, 8 is a beam splitter, 19 is an imaging optical system, 10 is a television camera, 92 is an object, 111 is a pupil plane of an imaging optical system, 114 is an optical axis, and 91 is a knife mirror 121 is a knife.

Claims (2)

[Claims] (1) A light source, an objective optical system, a light restriction member that blocks part of the light from the light source and directs a light beam decentered with respect to the optical axis of the objective optical system toward the objective optical system, and the objective optical system. a photodetector that detects, via the objective optical system, reflected light from the surface to be inspected that is illuminated via the optical system; In a focus detection device that detects displacement in an axial direction, the light restriction member has a reflecting surface that reflects light reflected from the test surface and directs it toward the photodetector, and the light restriction member An auxiliary photodetector is arranged to detect light that passes by the reflective surface and does not enter the photodetector, and the optical axis of the surface to be detected is detected based on a signal from the auxiliary photodetector. A focus detection device characterized by adjusting a position with respect to a direction. (2) An observation device characterized by using the focus detection device.