Object lens and condenser

An object lens includes a first optical system that obtains a magnified image of an object, a second optical system that guides dark field illumination light to the object, a barrel that contains the first optical system and the second optical system and has an optical path around the first optical system for the dark field illumination light, and a shield mechanism that is disposed on the optical path and that varies the incident area of the dark field illumination light to shield the dark field illumination light.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an object lens and a condenser that is mounted on a microscope and that can be used for dark field observation.

2. Description of the Related Art

Object lens and condensers mounted on microscopes and so forth have been used for not only regular bright field observation, but dark field observation. The dark field observation is performed by supplying a light beam from the periphery of an optical system such as an object lens or a condenser lens and guiding the light beam to the surface of an object. Thus, the dark field observation can be performed for samples that have flaws, foreign matter, unevenness, gap, or low reflectivity that cannot be observed by the bright field observation (for example, see FIG. 1 and so forth of Japanese Patent Application Laid-Open Publication NO. SHO 60-225817).

SUMMARY OF THE INVENTION

However, when the dark field observation is performed with an object lens or a condenser, since a ring-shaped light beam is equally emitted from the periphery of the optical system, not only a portion that has microscopic flaws and foreign matter but also directional flaws cannot be detected.

DETAILED DESCRIPTION OF THE INVENTION

From the foregoing point of view, an object of the present invention is to provide an object lens and a condenser with which an observation can be performed more finely than the dark field observation.

To solve the foregoing problem, a main aspect of the present invention is an object lens, comprising a first optical system that obtains a magnified image of an object; a second optical system that guides dark field illumination light to the object; a barrel that contains the first optical system and the second optical system and has an optical path around the first optical system for the dark field illumination light; and a shield mechanism that is disposed on the optical path and that varies the incident area of the dark field illumination light to shield the dark field illumination light.

The first optical system is a lens group that is conventionally used in for example reflection type illumination observation. The second optical system is disposed for example in the vicinity of the opening portion of the optical path. The second optical system is composed of a ring-shaped lens having a diffusion surface such as a ground glass surface for the incident surface of dark field illumination light, a mirror member disposed at a diaphragm portion at the forward end of the barrel, or the like. The object is for example a precise part, a metal material, or the like used for a semiconductor substrate or the like.

According to the present invention, when the incident area of dark field illumination light to the second optical system is varied, the dark field illumination light can be emitted to only a part of an object to be observed. In addition, the dark field illumination light can be emitted to the object to be observed from any direction. Thus, microscopic flaws, foreign matter, and so forth that cannot be detected by the conventional dark field observation can be detected. In addition, only directional flaws can be detected. Thus, a more microscopic observation can be performed than the conventional dark field observation.

According to one aspect of the present invention, the shield mechanism has a plurality of shield plates layered in the direction of the optical axis of the first optical system, the shield plates being rotated about the optical axis so as to vary the incident area of the dark field illumination. When the shield plates are closed, the optical path is narrowed and the incident area becomes small. When the shield plates are opened, the optical path is widened and the incident area becomes large. Since a plurality of shield plates are layered, the incident area can be varied stepwise. Thus, an object can be observed more microscopically.

According to one aspect of the present invention, the barrel has a hold member that holds the first optical system. Each of the shield plates has a first fit portion that fits the hold member so that each of the shield plates can be opened/closed; and a second fit portion that causes each of the shield plates to be rotated together while the first fit portion fits the hold member so that the shield plates are opened/closed. For example, the hold member is cylindrically disposed around the first optical system. The first fit portion is disposed in for example a ring shape so that the first fit portion fits the cylindrical hold member. Since the second fit portion causes each shield plate to be rotated together and opened/closed, when only one shield plate is operated and opened/closed, the incident area can be easily adjusted. Thus, the operability is improved.

According to one aspect of the present invention, the second fit portion has a fit protrusion that is disposed on the upside of each of the shield plates and that fits the upper adjacent shield plate, and a guide groove that is disposed on the underside of each of the shield plates and that fits the fit protrusion of the lower adjacent shield plate and guides the fit protrusion when each of the shield plates is opened/closed. Thus, when the fit protrusion of each shield plate is fit to the guide plate of the adjacent shield plate and the shield plates are rotated together, each shield plate is rotated together and opened/closed. As a result, the incident area can be easily varied.

The second fit portion may have a fit protrusion that is disposed on the underside of each of the shield plates and that fits the lower adjacent shield plate, and a guide groove that is disposed on the upside of each of the shield plates and that fits the fit protrusion of the upper adjacent shield plate and guides the fit protrusion when each of the shield plates is opened/closed.

According to one aspect of the present invention, when each of the shield plates that are fit are rotated so that the incident area becomes the minimum, the shield plates overlap each other for a predetermined area. Thus, dark field illumination light can be prevented from leaking out from adjacent shield plates when each shield plate is closed. As a result, the shield plates can securely shield the dark field illumination light. Thus, observation can be accurately performed.

According to an aspect of the present invention, at least one of the shield plates has a handle member that protrudes from the barrel. The handle member may be disposed for example at the uppermost shield plate and the lowermost shield plate. Thus, when the user holds the handle, applies force to it, and rotates it, the other shield plates are rotated together and opened/closed. As a result, the incident area can be easily varied.

According to one aspect of the present invention, the shield mechanism has a first shield plate group of the shield plates, the first shield plate group being rotatable together; and a second shield plate group of the shield plates, the second shield plate group being rotatable together, the second shield plate group being operable independently from the first shield plate group. Thus, when the first shield plate group and the second shield plate group are separately rotated and opened, not only the incident area of the dark field illumination light that enters the second optical system through the optical path, but the incident direction thereof can be freely varied. As a result, dark field illumination light can be emitted from any direction to an object.

Another main aspect of the present invention is a condenser, comprising a diaphragm mechanism that restricts dark field illumination light in a ring shape; a condenser lens that guides the dark field illumination light restricted by the diaphragm mechanism to an object; and an shield mechanism that varies the incident area of the dark field illumination light that enters the condenser lens so as to shield the dark field illumination light.

The condenser is used for transmission type illumination observation. In this structure, when the incident area of dark field illumination light to the condenser lens is varied, the dark field illumination light can be emitted to only a part of an object to be observed. In addition, the dark field illumination light can be emitted from any direction to an object to be observed. Thus, like the foregoing object lens, microscopic flaws, foreign matter, and so forth that cannot be detected by the conventional dark field observation can be detected. In addition, only directional flaws can be detected. Thus, an object can be observed more microscopically than the conventional dark field observation.

According to one aspect of the present invention, in the condenser, the shield mechanism has a plurality of shield plates layered in the direction of the optical axis of the condenser lens, the shield plates being rotated about the optical axis so as to vary the incident area of the dark field illumination.

According to one aspect of the present invention, the condenser further comprises a rotation shaft that rotates the shield plates. Each of the shield plates has a first fit portion that fits the rotation shaft so that each of the shield plates can be opened/closed; and a second fit portion that causes each of the shield plates to be rotated together while the first fit portion fits the holding member so that the shield plates are opened/closed.

According to one aspect of the present invention, in the condenser, the second fit portion has a fit protrusion that is disposed on the upside of each of the shield plates and that fits the upper adjacent shield plate, and a guide groove that is disposed on the underside of each of the shield plates and that fits the fit protrusion of the lower adjacent shield plate and guides the fit protrusion when each of the shield plates is opened/closed.

According to one aspect of the present invention, in the condenser, the second fit portion has a fit protrusion that is disposed on the underside of each of the shield plates and that fits the lower adjacent shield plate, and a guide groove that is disposed on the upside of each of the shield plates and that fits the fit protrusion of the upper adjacent shield plate and guides the fit protrusion when each of the shield plates is opened/closed.

According to one aspect of the present invention, in the condenser, when each of the shield plates that are fit are rotated so that the incident area becomes the minimum, the shield plates overlap each other for a predetermined area.

According to one aspect of the present invention, in the condenser, at least one of the shield plates has a handle member with which the shield plates are opened/closed.

According to one aspect of the present invention, in the condenser, the shield mechanism has a first shield plate group of the shield plates, the first shield plate group being rotatable together; and a second shield plate group of the shield plates, the second shield plate group being rotatable together, the second shield plate group being operable independently from the first shield plate group.

According to the present invention, an object lens and a condenser with which an object can be more microscopically observed than the dark field observation can be provided.

Next, with reference to the accompanying drawings, embodiments of the present invention will be described.

First Embodiment

Firstly, a first embodiment of the present invention will be described.FIG. 1is a perspective view showing the appearance of an object lens100according to this embodiment. The object lens100is used for a microscope.FIG. 2is an exploded perspective view showing the object lens100. The lighting systems of the microscopes are mainly categorized as a reflective type (used for an observation object such as metal that does not transmit light, but reflects it) and a transmission type (used for an observation object such as a microscopic organism that transmits light). However, it is assumed that the object lens100according to this embodiment is an object lens used for the reflection type lighting system.

A barrel1of the object lens100is composed of an upper barrel portion1a, a middle barrel portion1b, a lower barrel portion1c, and a diaphragm portion1d. Disposed in the barrel1is a concentric inner barrel3. The barrel1and the inner barrel3are connected by a connection member4. Held in the inner barrel3is a central lens group2that condenses bright field illumination light supplied from a light source that will be described later. Disposed at the top of the upper barrel portion1ais a thread portion1fthat mounts the object lens100to the microscope (not shown).

Formed between the barrel1and the inner barrel3is a ring-shaped optical path5through which ring-shaped dark field illumination light supplied from the light source through a ring diaphragm that will be described latter passes. Disposed over the optical path5and in the vicinity of the upside of the diaphragm portion1dof the barrel1is a ring-shaped lens6that condenses the dark field illumination light, which passes through the optical path5and enters the light to the observation object. The ring-shaped lens6has for example a ground glass surface that causes the dark field illumination light to diffuse so that illumination loss of the dark field illumination light decreases.

Disposed at a lower portion of the inner barrel3is a concaved fit portion3a. Fit to the fit portion3aare shield plates7that shield the dark field illumination light that enters the ring-shaped lens6through the optical path5. Next, the shield plates7will be described in the following.

FIG. 3is an exploded vertical sectional view showing the object lens100.FIG. 4is an exploded sectional view showing the shield plates7shown inFIG. 3.FIG. 5is an exploded perspective top view showing the shield plates7.FIG. 6is an exploded perspective bottom view showing the shield plate7.

The shield plates7are composed of for example 12 plates (shield plates7-1,7-2,7-3,74,7-5,7-6,7-7,7-8,7-9,7-10,7-11and7-12) layered in the direction of the optical path of the central lens group2. However, the number of the shield plates7is not limited to this number. Each shield plate7is composed of a ring portion7athat fits the fit portion3aand a nearly trapezoidal shape blade portion7bthat shields the optical path5(seeFIG. 2toFIG. 6). While the ring portion7ais fit to the fit portion3aof the inner barrel3, the ring portion7ais rotatable around the optical axis of the central lens group2. This rotation causes the blade portion7bto move horizontally on the optical path5and the shield plate7to open and close. When the shield plate7is opened, the dark field illumination light passes through the optical path5only from the open portion to the optical path5and enters the object through the ring-shaped lens6.

Disposed on the upper surface of the ring portion7aand in the vicinity of the boundary of the blade portion7bis a guide pin7c(seeFIG. 4andFIG. 5) and on the lower surface of the ring portion7aand in the vicinity of the boundary of the blade portion7bis a guide groove7d. When the guide pin7cof each shield plate7and the guide groove7dof the upper adjacent shield plate7are fit, they are fit. When the guide pin7cis guided to the guide groove7dand fit to the edge portion of the guide groove7d, force applied to the guide pin7ccauses each shield plate7to be rotated together.

When the guide pin7cand the guide groove7dof each shield plate7are rotated in the direction of which the shield plate7is closed and the guide pin7cof each shield plate7is fit to the edge portion of the guide groove7dof the upper adjacent shield plate7, they overlap for a predetermined area. Thus, the dark field illumination light is prevented from leaking out from the two adjacent shield plate7. As a result, the optical path5can be securely shielded.

As shown inFIG. 6, length d1of the guide groove7dis slightly shorter than width d2of the innermost periphery of each blade portion7b. In addition, the guide pin7cis positioned within width d2of the innermost periphery of the blade portion7b. Thus, when the guide pin7cand the guide groove7dof each shield plate7are rotated in the direction of which the shield plate7is closed and the guide pin7cof each shield plate7is fit to the edge portion of the guide groove7dof the upper adjacent shield plate7, the adjacent shield plates7overlaps for predetermined area S. Thus, the dark field illumination light can be prevented from leaking out from the adjacent shield plates7. Thus, the optical path5can be securely shielded.

The guide groove7dof the lower surface of the sixth shield plate7-6is formed fully on the ring portion7ain a ring shape (seeFIG. 6). When the guide pin7cof the seventh shield plate7-7is fit to the ring-shaped guide groove7dand guided thereby, the shield plate7-7can be rotated by 360°, not moved together with the shield plate7-6. In other words, the upper six shield plates7are rotated together, while the lower six shield plates7are rotated together. The sixth shield plate7is not rotated together with the seventh shield plate7. Thus, when the shield plate7is opened, not only the incident area of the dark field illumination light that enters from the optical path5to the ring-shaped lens6, but the incident direction thereof can be freely varied. Thus, the dark field illumination light can be emitted to the object from any direction. For example, when the optical path5is shielded on one side of the object lens100and the opposite side thereof, the dark field illumination light enters from the left and right directions. In addition, when all 12 shield plates7are placed at the rear, front, left, or right, the dark field illumination light enters from one direction.

The shield plates7-1,7-6,7-7, and7-12each have a handle7e. When the user holds each handle7eand applies force to it in the horizontal direction, the upper six shield plates7and the lower six shield plates7can be moved together so that they are opened/closed. As shown inFIG. 1andFIG. 2, the middle barrel portion1bof the barrel1has a slit portion1ethrough which each handle7erotatably protrudes.

FIG. 7are schematic diagrams showing the state of which illumination light is emitted from a light source to an object through the object lens100.FIG. 7(a) shows the case of bright field illumination light.FIG. 7(b) shows the case of dark field illumination light.

As shown inFIG. 7(a), when bright field observation is performed, bright field illumination light11emitted from a light source8is restricted by a bright field observation open-type diaphragm9, reflected by a reflection mirror10, and guided to an object12placed on a stage13through the central lens group2of the object lens100. In this case, the bright field illumination light11vertically enters the object12. The bright field illumination light11is reflected by the central lens group2and then guided to an eyeglass (not shown). As a result, the user can observe the object.

On the other hand, as shown inFIG. 7(b), when dark field observation is performed, dark field illumination light15emitted from the light source8is restricted by a dark field observation ring-type diaphragm14in a ring shape, reflected by the reflection mirror10, passed through the optical path5of the object lens100, and guided to the object12through the ring-shaped lens6. When a part of the optical path5is shielded by each shield plate7, the dark field illumination light15is emitted to the object12through the non-shielded portion of the optical path5. The dark field illumination light15emitted to the object is reflected to the central lens group2and observed through the eyeglass as with the bright field illumination light11.

In this case, the dark field illumination light15is diagonally emitted to the object12. Only diffusely reflected light is observed. Thus, unlike the case of the bright field observation, since the background and the front surface of the object are dark, the unevenness, flaws, and so forth of the object can be brightly observed. The object12is for example a semiconductor substrate or a metal material.

Next, the operation of the object lens100that has the foregoing structure will be described.FIG. 8are top views of the object lens100showing states of which the shield plates7are opened/closed stepwise when the dark field observation shown inFIG. 7(b) is performed.FIG. 9are perspective views showing the states of which the shield plates7are opened/closed stepwise.

In the state that all the shield plates7are closed (seeFIGS. 8(a) and9(a)), when the user holds each handle7eof the shield plates7-6and7-7and applies force to them in the directions of arrows A and B, the shield plates7-6,7-5, and so forth are rotated together by the guide pin7cand the guide groove7dalong the fit portion3aof the inner barrel3as shown inFIGS. 8(b) and9(b). Likewise, the shield plates7-7,7-8, and so forth are rotated together by the guide pin7cand the guide groove7dalong the fit portion3aof the inner barrel3as shown inFIGS. 8(b) and9(b). As a result, the shield plates7are open and the optical paths5appear (seeFIGS. 8(b) and9(b). When the user further applies force to each handle7ein the directions of arrows A and B, the shield plates7are further opened and the sections of the optical paths5become large. The optical paths5are opened until the upper six shield plates7are placed on top of each other and the lower six shield plates7are placed on top of each other (seeFIGS. 8(c) and9(c)). Thus, the sections of the optical paths5, namely, the incident area of the dark field illumination light to the ring-shaped lens6and the object12can be varied. As a result, microscopic flaws, unevenness, and so forth that cannot be observed by the conventional dark field observation can be observed.

Of course, when the user applies force to each handle7eof the shield plates7-1and7-12instead of each handle of the shield plates7-6and7-7, the optical paths5can be opened/closed. In addition, as described above, since the shield plate7-6and the shield plate7-7are not rotated together, when the upper six shield plates7and the lower six shield plates7are rotated together to predetermined positions, the shield positions (shield directions) of the optical paths5can be freely adjusted. Thus, not only the incident area of the dark field illumination light, but the incident position thereof (incident direction thereof can be freely varied. Thus, directional flaws, unevenness, and so forth of the object can be easily observed.

In addition, as described above, even if each shield plate7is rotated in the direction of which the optical paths5are closed (opposite direction of arrows A and B), the shield plates7overlap for a predetermined area. Thus, the shield plates7can securely shield the dark field illumination light.

Next, an effect of which the dark field observation is performed with the object lens100according to this embodiment will be described.FIG. 10(a) is a schematic diagram showing an observed image of which the bright field observation is performed for a circuit board as the object12.FIG. 10(b) is a schematic diagram showing an observed image of which the dark field observation is performed for a circuit board with a conventional object lens that does not have the shield plates7.

As shown in these drawings, there are microscopic horizontal stripe flaws at the center of the observed image of the circuit board. Wires are observed on the left of the flaws and vertical lines on the right of the flaws. In the dark field image shown inFIG. 10(b), since a ring-shaped light beam is equally emitted to the circuit board, the front surface of the substrate are darkly observed, whereas flaws, wires, and lines are whitely observed.

FIG. 11are schematic diagrams showing the open positions of the shield plates7and observed images of a circuit board when the dark field observation is performed by varying the open positions and open areas of the shield plates7.

FIG. 11(a) shows the state of which the dark field observation is performed by opening the shield plates7so that the dark field illumination light is emitted from the near side of the object lens100. As shown in the drawing, the upper portion of radial wires disappears from the dark field image shown inFIG. 10(b). As a result, center flaws can be easily observed. Thus, the upper pattern of the flaws that does not clearly appear in the dark field image shown inFIG. 10(b) can be clearly observed.

FIG. 11(b) shows the state that the dark field observation is performed by opening the shield plates7so that the dark field illumination light is emitted from the right of the object lens100. As shown in this drawing, right handed vertical lines and a part of lower left wires disappear. As a result, flaws can be easily observed. In addition, the lower pattern of the flaws can be clearly observed.

FIG. 11(c) shows the state that the dark field observation is performed by opening the shield plates7so that the dark field illumination light is emitted from the right and left of the object lens100. As shown in this drawing, the right vertical lines disappear from the dark field image shown inFIG. 10(b). Thus, flaws can be easily observed. In addition, the upper and lower patterns of the flaws can be clearly observed.

Thus, when the shield plates7are used, portions such as wires and vertical lines that obstruct flaws to be observed can be concealed. Thus, microscopic flaws and unevenness can be more easily observed than the conventional dark field observation. In addition, since the direction of which the dark field illumination light is emitted can be varied, directional flaws and so forth can be easily observed.

When the object lens100according to this embodiment is applied to not only industrial samples such as a circuit board and a metal material, but for example medical samples, microscopic variation in a pathologic sample, a sign of special variation, and so forth can be observed.

Second Embodiment

Next, a second embodiment of the present invention will be described. According to the first embodiment, an object lens used for reflection-type dark field observation was described. However, according to the second embodiment, the present invention is applied to a condenser used in transmission-type dark field observation. As described above, a transmission type illumination system is used when an organism such as a microscopic organism, which transmits illumination light.

FIG. 12is a schematic diagram showing the structure of a condenser200according to this embodiment and the path of dark field illumination light.FIG. 13is a bottom view showing the condenser200. In these drawings, similar portions to those of the first embodiment are denoted by similar reference numerals and their description will be simplified or omitted.

As shown inFIG. 12, the condenser200according to this embodiment is composed of a condenser lens portion16and a turret17. The turret17is composed of an upper fixed portion17aand a lower rotating portion17b. The rotating portion17bhas a bright field observation optical path19and a dark field observation optical path18. When the rotating portion17bis horizontally rotated about a rotation shaft24, the bright field observation can be switched to the dark field observation or vice versa. A ring-shaped diaphragm23that restricts the dark field illumination light25in a ring shape is disposed on a dark field observation optical path18.

An inner barrel21is disposed on the dark field observation optical path18and secured to a rotation portion17bby a connection member22. The inner barrel21has a fit portion21a. Shield plates20are fit to the fit portion21a. The basic structure of the shield plates20is the same as that of the shield plates7of the first embodiment. Some shield plates20have a handle20athat protrudes from the lower surface of the rotating portion17b. When the user horizontally applies force to the handle20a, like the case of the first embodiment, the handle20ais rotated in the direction of an arrow shown inFIG. 13about the inner barrel21. As a result, the shield plates20can be opened/closed.

Dark field illumination light25is emitted from a light source29, reflected to a reflection mirror30, guided from the dark field observation optical path18to the ring diaphragm23, and emitted to an object27placed on a stage28through the condenser lens portion16. While the shield plates20are closed, the dark field illumination light25is shielded. The dark field illumination light25is emitted to the object27. The object transmits the dark field illumination light25. The dark field illumination light25is guided to the object lens26. As a result, a dark field image can be observed by an eyeglass or the like (not shown).

Thus, when the transmission type dark field observation is performed with the condenser200that has the shield plates20, like the first embodiment, by shielding the dark field illumination light25, the incident area and incident direction of the dark field illumination light that enters the object27can be varied. As a result, an object can be more microscopically observed than the conventional transmission type dark field observation.

The present invention is not limited to the foregoing embodiments. Various modifications of the foregoing embodiments may be performed without departing from the spirit of the present invention.

In the first and second embodiments, the shield plates have a ring and a trapezoidal shape. However, the shape of the shield plates is not limited to that example. As long as the shield plates can shield dark field illumination light, the shield plates may have any shape.

According to the first embodiment and the second embodiment, a guide pin and a guide groove are disposed on the upper surface and the lower surface of each shield plate, respectively. Instead, the guide groove and the guide pin may be disposed on the upper surface and the lower surface, respectively.

According to the first and second embodiments, the shield plates are grouped as upper six plates and lower six plates. The upper six plates and the lower six plates are rotated together as groups. Instead, the guide groove of the sixth shield plate may have the same structure as that of each of the other plates so that all the plates are rotated together. Instead, the uppermost shield plate and the lowermost shield plate may be fixed to the barrel and the inner barrel of the condenser, respectively, so that the shield plates can be opened or closed when the user applies force to one handle.

In the object lens100of the first embodiment, the ring-shaped lens6is disposed at the upside of the diaphragm portion1dto condense the dark field illumination light and diagonally emit the dark field illumination light to the object. Instead, when a mirror is disposed inside the diaphragm portion1dor the inner surface of the diaphragm portion1dis formed on a mirror, the dark field illumination light can be condensed.

According to the second embodiment, the present invention is applied to a condenser that allows both the bright field observation and the dark field observation to be performed by rotating the rotating portion of the turret. Of course, the present invention can be applied to a condenser dedicated for the dark field observation.