Microscope illuminating apparatus

Abstract: A microscope illuminating apparatus includes a light-shielding tube (33a) surrounding an objective lens (25), detachably mounted on a revolver (21) of a system microscope in order to guide illumination light to irradiate an observation field, thus separating an illumination optical path and an observation optical path. An annular illuminating section (30) serving as a light source of the illumination light is provided at a position to oppose an end portion aperture of the illumination optical path in the revolver (21).

Description: The present invention relates to a microscope illuminating apparatus used in, e.g., a system microscope. Conventionally, in a system microscope in which an attachment and various types of optical members are present in its observation optical system in accordance with the content of microscopic observation, an infinity correction observation optical system is used so that the optical members do not adversely affect the magnification and the image forming characteristics. The following general considerations facilitate the understanding of the invention. Fig. 12 shows a reflected illuminating apparatus applied to a system microscope having an infinity correction observation optical system. Referring to Fig. 12, an objective lens 1 is mounted on a revolver 2 of the microscope through an objective lens outer frame la. An objective lens system 3 constituting part of the infinity correction observation optical system is provided at the central portion of the objective lens 1. A lens frame 3a for separating dark field illumination light and bright field illumination light is provided on the outer circumference of the objective lens system 3. An annular condenser lens 4 is provided on the outer circumference of the distal end portion of the objective lens system 3. An annular mirror 5 having a hole for deflecting illumination light toward the condenser lens 4 is arranged above the objective lens system 3. A light-shielding tube 6 is arranged at the central portion of the holed mirror 5 to be coaxial with the observation optical axis. The light-shielding tube is arranged to prevent annular illumination light from mixing in the observation optical path. Light emitting from a light source 7 is collimated to illumination light comprising parallel rays by illumination lenses 8 to 10 and is incident on the holed mirror 5. Since the optical members, e.g., an attachment and the half mirror described above are interposed between the objective lens system 3 and the light-shielding tube 6, a sufficient distance is set between the objective lens system 3 and the light-shielding tube 6. A light-shielding tube 12 for separating an illumination optical path and the'observation optical path is provided between the objective lens system 3 and the light-shielding tube 6. The objective lens system 3 described above apparently serves as a condenser lens during reflected bright field illumination. In the reflected illuminating apparatus having the above arrangement, the illumination light emitted from the light source 7 is set to parallel illumination light by the illumination lenses 8 to 10 and is incident on the holed mirror 5. Annular illumination light reflected by the holed mirror 5 is incident on the annular condenser lens 4 through the illumination optical path and is condensed on an object surface 0. Light reflected by the object surface O is incident on a focusing lens (not shown) through the objective lens system 3 and the light-shielding tube 6. When the light reflected by the object surface O passes through the light-shielding tube 6, generation of flare in the light-shielding tube 6 is prevented by a stop 11 provided in the light-shielding tube 6. In the reflected illuminating apparatus described above, however, the numerical aperture must be set large to improve the resolution of the objective lens system 3, and the distance between the objective lens system 3 and the stop 11 must be set long to interpose the attachment in the observation optical system. This leads to a lack in quantity of light around the observation field. This problem will be discussed with reference to Fig. 13. Note that Fig. 13 schematically shows the infinity correction observation optical system between the object surface O and the stop 11 of the light-shielding tube 6. In the infinity correction observation optical system in Fig. 13, the ray of light emitting from a center P2 of the observation field propagates in parallel with the optical axis, as indicated by ν1 to v3, while the ray of light emitting from a periphery P1 of the observation field propagates obliquely to the optical axis, as indicated by v4 to v6. Therefore, if the stop 11 is present halfway, although the ray from the center P2 of the observation field is entirely transmitted through it, the rays from the periphery P1 from the observation field may be cut by the stop 11, and the farther from the center of the observation field, the larger the attenuation amount of the quantity of light, resulting in a dark image. This tendency becomes strong as the stop position becomes farther as from a to b . A similar lack in quantity of light also occurs when the numerical aperture of the objective lens is increased. This lack in quantity of light can be solved to a certain degree by widening the observation optical path. In the conventional reflected illuminating apparatus, however, since the annular illumination optical path and the observation optical path are separated by the light-shielding tube 12 in order to prevent mixing of the illumination light in the observation optical path, the width of the observation optical path is limited, and it is difficult to widen the observation optical path. Optical microscopes are widely utilized in the field of biology as they can observe a live specimen. Above all, a dark field microscope has the features of the optical microscope while it has a resolving power greatly higher than that of the optical microscope. The dark field microscope can thus detect a very small molecule, e.g., a molecule having a size of several tens of nm and is effective in examining the dynamic behavior of, e.g., various small molecules constituting a small organ in a cell. Fig. 14 shows an illuminating apparatus of a conventional transmitted dark field-microscope having an arrangement as follows. A stage 63 for placing a specimen 62 thereon is supported on a microscope frame 61 to be movable along an observation optical axis 64. An objective lens 65 for enlarging and observing the specimen 62 is fixed above the frame 61 along the observation optical axis 64. A lamphouse 67 housing an illumination light source 66 is fixed below the frame 61. A beam emitted from the light source 66 is guided to a reflecting mirror 71 through a plurality of filters 69 and a field stop 70 sequentially, and the beam reflected by the reflecting mirror 71 is guided toward the specimen 62. The filters 69 can be inserted in and removed from the illumination optical path in order to adjust the brightness of the illumination light source 66 and the nature of the light, e.g., color. The arrangement described above is the same as that of an ordinary microscope for transmitted illumination field observation. In addition to this arrangement, the dark field microscope needs a dark field condenser 72 as follows. That is, the dark field condenser 72 must be constructed that it has a numerical aperture larger than that of the objective lens 65 and can illuminate the specimen 62 such that the illumination light will not be directly incident on the objective lens 65 and such that only the light scattered by the specimen 62 is incident on the objective lens 65. For this purpose, the dark field condenser 72 has an annular condenser case 73, a dark field condenser lens 74 fixed on the end portion of the aperture of the condenser case 73 and having first and second spherical reflecting surfaces 74a and 74b, and a ring slit 75 fixed inside the condenser case 73 to be close to the condenser lens 74. The dark field condenser 72 having this arrangement is supported by and fixed on a condenser carrier 76 which is supported to be movable along the observation optical axis 64-and adjustable in the vertical direction with respect to the observation optical axis 64. The condenser carrier 76 is mounted on the stage 63. Thus, the illumination light emitted from the illumination light source 66 passes through the ring slit 75 to become annular, is directed outward by the first reflecting surface 74a of the dark field condenser lens 74, and is then directed inward by the second reflecting surface 74b of the condenser lens 74. As a result, the illumination light is not directly incident on the objective lens 65 but is radiated on the specimen 62. In this case, of the transmitted bright field beams, only the beam which has passed through the ring slit 75 serves as the dark field illumination beam. This dark field microscope has problems as follows: (1) Since only the beam, of the illumination beams, that has passed through the ring slit 75 serves as the dark field illumination beam, the illumination efficiency is very low, and accordingly the dark field illumination becomes very dark. (2) To perform switching between the dark field illumination and the bright field illumination, the entire dark field condenser 72 must be exchanged, and after the exchange, optical adjustment of the condenser 72, i.e., centering of the specimen 62 and adjustment of the distance between the specimen 62 and the condenser lens 74 must be performed every time illumination is switched. (3) The beam passing through the ring slit 75 of the condenser 72 for the dark field illumination is the beam emerging from the periphery of the field stop 70, and in dark field observation, an operation for aperture the field stop 70 need be performed. (4) Since the quantity of light to be observed is largely changed after switching between the dark field the and bright field, the filters 69 for brightness control must be inserted or removed. A microscope illuminating apparatus from which the problem (1) is solved is conventionally known, as described in Published Unexamined Japanese Patent Application No. 55-140811 (EP 0 019 309) This microscope illuminating apparatus has a light source remote from a precious stone to be examined, a glass fiber optical guide member extending to an annular endpiece, and a reflecting mirror mounted on the endpiece, and has a function as follows. That is, light emitted from the light source is gathered by the glass fiber bundle. The fiber constituting the bundle is dispersed in the endpiece so as to transmit the annular light to the upper surface of the endpiece. Light emerging through the endpiece is focused by the reflecting mirror and is radiated on the precious stone. Hence, although this known example can prevent dark field illumination problem (1), the remaining problems (2), (3), and (4) cannot be solved. Recently, in reflected dark field observation, a method having an optical fiber bundle in order to perform illumination having a small variation with a large illuminance is disclosed in the specification of Japanese Patent Application No. 3-77881. According to this method, an annular optical fiber 100 is detachably formed on a revolver 101, and light emerging from the optical fiber 100 is supplied to an objective lens 102 as dark field illumination light, as shown in Figs. 15 and 16. Light-shielding tubes 103a and 103b for separating the dark field illumination light and the observation light are fixed in the revolver 101 and the objective lens 102, respectively, by three stays 104a, 104b, and 104c shown in Fig. 16. Two end portions D and F of each of the three stays 104a, 104b, and 104c are arcuatedly formed, as shown by the stay 104a, and a central portion E connecting the two end portions D and F is linearly formed. DE-A-31 00 662 discloses a microscope illumination system comprising an objective, surrounded by a light shielding tube, and a annular light source constituted by annularily arranged ends of optical fibers and a annular lense. From GB-A-2 168 167 a microscope with a microscope illumination system having the features of the preamble of claim 1 is known which system can be switched between bright field illumination and dark field illumination. It is an object of the present invention to provide a microscope illumination apparatus which can easily perform said switching between dark field illumination and bright field illumination, and which provides excellent illumination in both illumination modes. This object is solved by a microscope illumination apparatus in accordance with claim 1 respectively. An advantageous further development is subject matter of claim 2. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a sectional view schematically showing an arrangement of a microscope illuminating apparatus according to a first embodiment of the present invention; Fig. 2 schematically shows an arrangement of a system microscope to which a microscope illuminating apparatus according to a second embodiment of the present invention is applied; Fig. 3 shows a state in which a revolver is being mounted on an arm portion of a microscope body; Fig. 4 shows a state in which an electrical means for electrically driving a total reflection mirror is provided to a dark field illumination unit; Fig. 5 is a sectional view schematically showing an arrangement of the dark field illumination unit mounted on the system microscope shown in Fig. 2; Fig. 6 is a side view of the portion shown in Fig. 5; Fig. 7 is a plan view of a mirror seat incorporated in the dark field illumination unit and the total reflection mirror provided on the mirror seat; Fig. 8 is a sectional view schematically showing an annular light source section mounted on a bright/dark field revolver of the system microscope shown in Fig. 2 and an optical fiber tube connected to the annular light source section; Fig. 9 is a sectional view schematically showing an arrangement of a slider applied to a microscope illuminating apparatus according to the twelfth embodiment of the present invention; Fig. 10 is a side view of the portion shown in Fig. 9; Fig. 11 schematically shows an arrangement of a system microscope to which a microscope illuminating apparatus according to the fourteenth embodiment of the present invention is applied; Fig. 12 shows an arrangement of a conventional microscope reflected illuminating apparatus; Fig. 13 explains a decrease in quantity of light corresponding to a stop position; Fig. 14 shows an arrangement of a conventional microscope transmitted illuminating apparatus; Fig. 15 is an enlarged sectional view of an objective lens portion of the conventional microscope reflected illuminating apparatus shown in Fig. 14; and Fig. 16 is an enlarged sectional view of a light-shielding barrel provided to the objective lens shown in Fig. 15 and stays supporting the light-shielding barrel. A microscope illuminating apparatus according to the present invention will be described with reference to Fig. 1. Note that the same portions as in the conventional apparatus shown in Fig. 14 are denoted by the same reference numerals, and a detailed description thereof is omitted. As shown in Fig. 1, in the microscope illuminating apparatus according to this embodiment, an illumination switching mirror 80 is disposed in the optical path between a condenser lens 68 and light control filters 69 in a lamphouse 67. The illumination switching mirror 80 can be operated from the outside of the lamphouse 67 to switch the illumination beam emitted from a light source 66 toward the light control filters 69 or toward an optical path branching case 81. An opening is formed in a wall surface of the light source close to the illumination switching mirror 80, and the bottomed cylindrical optical path branching case 81 is coupled to this opening. The optical path branching case 81 has a condenser lens 82 and light control filters 83 which can be inserted in and removed from the illumination beams guided through the condenser lens 82 to adjust the brightness, color, or the like of illumination. An incident end 84a of an optical fiber bundle 84 is detachably connected to the bottom surface of the optical path branching case 81. An exit end 84b of the optical fiber bundle 84 is annularly disposed in an annular condenser case 86 of a bright/dark field condenser 85 to be described below. An annular collimator lens (annular illuminating section) 87 for collimating the beam to an annular beam is disposed in the condenser case 86. A condenser lens 88 and an annular dark field condenser lens 89 having an arcuated wall surface to house the condenser lens 88 are housed in the condenser case 86. The dark field condenser lens 89 is formed to transmit the beam passing through the condenser lens 88 therethrough along the optical axis. First and second reflecting surfaces 89a and 89b are formed on the inner and outer circumferential surfaces of the dark field condenser lens 89. The dark field condenser lens 89 and the condenser lens 88 are coaxially bonded to each other. When dark field observation is to be performed by using this apparatus, the illumination switching mirror 80 is moved to a position indicated by a solid line in Fig. 1. As a result, the illumination beam emitted from the light source 66 is transmitted through the collector lens 68, reflected by the illumination switching mirror 80, and guided to the incident end 84a of the optical fiber bundle 84 through the condenser lens 82 and the light control filters 83. The illumination beam emerging from the exit end 84b through the optical fiber bundle 84 is collimated to an annular parallel beam by the annular collimator lens (annular illuminating section) 87 and radiated on the dark field condenser lens 89. The annular parallel beam incident on the dark field condenser lens 89 is guided from the first reflecting surface 89a to the second reflecting surface 89b and focused on a specimen 62. As a result, the illumination light is not directly incident on an objective lens 65, and efficient dark field illumination for the surface of the specimen 62 can be performed. When bright field observation is to be performed, the illumination switching mirror 80 is moved to a position indicated by a broken line in Fig. 1. As a result, the illumination beam emitted from the light source 66 is incident on the bright/dark field condenser 85 through the filters 69 and a reflecting mirror 71. Since the condenser lens 89 is hollow along the optical axis, the illumination beam incident on the bright/dark field condenser 85 is focused on the specimen 62 through the condenser lens 88. As a result, bright field illumination is performed on the surface of the specimen 62. As described above, not only very efficient dark field illumination can be performed in dark field observation, but also switching between dark field illumination and bright field illumination can be smoothly performed by only operating the illumination switching mirror 80. Furthermore, if the brightness, color, or the like of dark field illumination is adjusted by the light control filters 83 and if the illumination field is adjusted by a field stop 70 in advance, switching between dark field illumination and bright field illumination can be performed by only operating the illumination switching mirror 80. In this embodiment, when a semi-transparent mirror is used as the illumination switching mirror 80, dark field illumination and bright field illumination can be simultaneously performed. A microscope illuminating apparatus according to a second embodiment of the present invention will be described with reference to Figs. 2 to 8. As shown in Figs. 2, 3, and 4, a system microscope to which the microscope illuminating apparatus according to the second embodiment of the present invention has a microscope body 150 and a bright field system projection tube 151 provided on the microscope body 150. For example, a round dovetail engaging portion 152 is formed at one end of the bright field system projection tube 151, and a dark field illumination unit 153 is detachably mounted on the engaging portion 152. A lens barrel sleeve 154 is connected to the other end of the bright field system projection tube 151. A lens barrel 155 projects from the upper portion of the lens barrel sleeve 154, and an eyepiece 156 is mounted on the distal end of the lens barrel 155. As shown in Fig. 3, a linear slide groove 157 is formed on an arm portion 150a of the microscope body 150. As a result, various types of revolvers 158 can be Mounted on and detached from the arm portion 150a by inserting and removing (insertion and removal directions are indicated by a double-headed arrow S) their dovetail portions 159 along the linear slide groove 157. In the second embodiment, a bright/dark field revolver 158 to be described later is detachably mounted on the arm portion 150a. A lamphouse 162 incorporating a lamp 161 is detachably mounted on the dark field illumination unit 153 through, e.g., a round dovetail engaging portion 160 having the same figure as the round dovetail engaging portion 152. The dark field observation unit 153 will be described with reference to Figs. 5, 6 and 7. The dark field illumination unit 153 has a switching unit 163, mounted between the bright field system projection tube 151 and the lamphouse 162 through the engaging portions 152 and 160 described above, and an attachment 164 mounted on the switching unit 163. A hollow space for transmitting the illumination light from the lamphouse 162 therethrough is formed in the switching unit 163 and a total reflection mirror 165 as shown in Fig. 7 is provided in this hollow space. The total reflection mirror 165 is fixed to a mirror seat 166. One end portion of the mirror seat 165 is supported on a pivotal shaft 167 so that the mirror seat 166 is swingable about the pivotal shaft 167. The pivotal shaft 167 extends in the hollow space in a direction perpendicular to the optical axis of the illumination light. The two ends of the pivotal shaft 167 are pivotally supported by the switching unit 163. The mirror seat 166 is swingable between a position A (a 45° position with respect to the optical axis) and a position B (off the optical path) in Fig. 6 and is held at the position A or B through a click 168 (see Fig. 5). A control 169 for pivoting the pivotal shaft 167 is provided on the outer portion of the switching unit 163. A hole having a predetermined size is formed at the central portion of the mirror seat 166. Thus, when a half mirror or the like is supported by the mirror seat 166, part of the illumination light incident on the half mirror or the like can be transmitted toward the bright field system projection tube 151. The attachment 164 incorporates a condenser lens 170 for receiving the illumination light reflected by the total reflection mirror 165. A dark field system illumination filter 171 (e.g., a color temperature change filter or an ND filter) is provided below the condenser lens 170. The filter 171 is detachably supported through a notched portion 172 formed on the inner circumferential surface of the attachment 164. A joint portion 173 of an optical fiber is fixed at a lowermost portion of the attachment 164 by a screw 174. An optical fiber tube 175 extending from the joint portion 173 extends through the arm portion 150a of the microscope body 150 and is connected to an annular light source section (i.e., an annular illuminating section) 176 (see Figs. 2, 3, and 8) detachably provided in the bright/dark field revolver 158. The dark field illumination unit 153 can be rotated through 360° about the optical axis by the engaging portions 152 and 160 described above. Hence, when the dark field illumination unit 153 is mounted on various types of lens bases, the dark field illumination unit 153 can be rotated so as not to be interfered with by the exit end of the optical fiber and the operating section 153 of the dark field illumination unit 153 can be set at an easily accessible position. The operation of the microscope illuminating apparatus according to the second embodiment will be described. A bright field system revolver is removed, and the bright/dark field revolver 158 is mounted on the arm portion 150a of the microscope body 150. The lamphouse 162 is temporarily removed from the bright field system projection tube 151, and the dark field illumination unit 153 is mounted on the bright field system projection tube 151. Then, the lamphouse 161 is mounted on the dark field illumination unit 153. Thereafter, the optical fiber tube 175 is inserted in the arm portion 150a, and the joint portion 173 of the optical fiber tube 175 is connected to the attachment 164. Assume that when assembly of this apparatus is completed, bright illumination field system observation is to be performed first. This case will be described with reference to Figs. 2 to 8. The control 169 (see Fig. 5) is pivoted to fix the mirror seat 166 at the position B (see Fig. 6) by the click 168. When the mirror seat 166 is at the position B, the total reflection mirror 165 supported by the mirror seat 166 is off the optical path of the illumination light. Thus, the parallel illumination rays having a predetermined wavelength which are supplied from the lamp 161 through a collector lens 177 and a filter 178 are guided to the lens barrel sleeve 154 (see Fig. 2) through the dark field system unit 153 and the bright field system projection tube 151. As shown in Fig. 2, the guided illumination light is radiated on a half mirror 179 which is disposed in the lens barrel sleeve 154 at an angle of 45° with respect to the optical axis. The illumination light reflected by the half mirror 179 is focused on a specimen 182 (see Fig. 8) disposed on a stage 181 through the bright/dark field revolver 158 and a bright/dark objective lens 180. The light reflected by the specimen 182 is radiated on a imaging lens (not shown) through the bright/dark objective lens 180, the bright/dark revolver 158, and the half mirror 179. Bright field system observation for the surface of the specimen 182 is performed through the eyepiece 156 by observing the image formed by the imaging lens. A case in which dark field system observation is to be performed will be described with reference to Figs. 2 to 8. The control 169 is pivoted to fix the mirror seat 166 at the position A (see Fig. 6) by the click 168. When the mirror seat 166 is at the position A, the total reflection mirror 165 supported by the mirror seat 166 is disposed at an angle of 45° with respect to the optical axis of the illumination light. Hence, the parallel dark field illumination rays supplied from the lamp 161 through the collector lens 177 and the filter 178 are reflected by the total reflection mirror 165 toward the attachment 164 and radiated on the condenser lens 170. The illumination light radiated on the condenser lens 170 is condensed on the joint portion 173 of the optical fiber tube 175 through the filter 171. The illumination light condensed on the joint portion 173 is guided, through the optical fiber tube 175, to the annular light source section (i.e., the annular illuminating section) 176 detachably provided in the bright/dark field revolver 158. The guided dark field illumination light is collimated to parallel rays by an annular lens 183 (see Fig. 8) opposing the annular light source section (i.e., the annular illuminating section) 176. The parallel dark field illumination rays are radiated on an annular condenser lens 187 through a dark field illumination optical path 186 defined between an outer frame 184a of an objective lens 184 and a light-shielding tube 185 for separating the illumination light from the observation light. The dark field illumination light is radiated on the specimen 182 on the stage 181 by the annular condenser lens 187. The diffracted light reflected by the specimen 182 is radiated on a imaging lens (not shown) by the bright/dark field objective lens 180 supported by the light-shielding tube 185 in the objective lens 184 through the bright/dark field revolver 158 and the half mirror 179. The dark field system observation for the surface of the specimen 172 is performed through the eyepiece 156 by observing the image formed by the imaging lens. Since the illumination light supplied from the collector lens 177 incorporated in the lamphouse 162 is collimated, it will not adversely affect the optical system on the bright field system projection tube 151 side even if the dark field illumination unit 153 is mounted while the distance between, e.g., the collector lens 177 and the illumination lens (not shown) incorporated in the bright field system projection tube 151 is set long. In this manner, according to the microscope illuminating apparatus according to the second embodiment of the present invention, reflected dark field observation , can be performed by using the bright field system projection tube 151 without a change. Thus, the performance of the microscope as a system can be improved. As a result, since an expensive bright/dark field projection tube need not be separately purchased, unlike in the conventional apparatus, an extra expenditure can be eliminated. Since the dark field illumination unit 153 is used, the light source of the lamphouse 161 together with the incidence projection tube can be used without a change. Hence, an expensive external light source need not be separately purchased. The present invention is not limited to the arrangement of the second embodiment described above. For example, other polarizing elements (i.e., a half mirror or a beam splitter having a different transmittance) can be used in place of the total reflection mirror 165. When such a polarizing element, is used, reflected dark field observation and other optical observations (e.g., reflected bright field observation) can be simultaneously performed. Accordingly, reflected fluorescence observation and reflected dark field observation can be simultaneously performed in the field of biology, time required for observation of a specimen dyed with multiple of colors can be shortened, and the observation precision can be improved. As shown in Fig. 4, as a method of performing switching among dark field observation and other optical observations, an electrical means (e.g., a motor 188) is connected to the pivotal shaft 167 provided to the dark field illumination unit 153 to remote-control the dark field illumination unit 153. The microscope body 150 and the bright field system projection tube 151 and the lens barrel sleeve 154 can be integrally formed. A microscope illuminating apparatus according to a third embodiment of the present invention will be described with reference to Figs. 9 and 10. Note that the same portions as in the second embodiment are denoted by the same reference numerals, and a detailed description thereof is omitted. As shown in Figs. 9 and 10, the microscope illuminating apparatus according to the third embodiment has a slider 190 between a bright field system projection tube 151 and a lamphouse 162. The slider 190 extends in a direction perpendicular to the optical axis, and is supported on a slider support member 191 to be slidable in a direction perpendicular to the optical axis. This slidable movement can be easily performed by pushing or pulling a control 192, provided to the end portion of the slider 190, in a direction perpendicular to the optical axis. The slider 190 is held at a predetermined position by a click 193 provided in the slider support member 191. The slider 190 has a total reflection mirror 165 and a filter box 194. A hole portion 195 for transmitting the illumination light from the lamphouse 162 therethrough is formed between the total reflection mirror 165 and the filter box 194. The total reflection mirror 165 is disposed at an angle of 45° with respect to the optical axis of the illumination light irradiated on the total reflection mirror 165. Filters 196 (e.g., a color temperature change filter or an ND filter) for imparting predetermined optical characteristics to the illumination light are detachably supported by predetermined notched grooves 197. Thus, a desired filter 196 can be arranged as required. An attachment 164 the same as that described above is fixed on the slider support member 191. The slider support member 191 is provided by engaging portions 152 and 160 the same as those described above to be rotatable about the optical axis through 360°. Hence, the slider_support member 191 can be set at a desired position by the control 192. As a result, operability of the microscope during observation is improved. The operation of the microscope illuminating apparatus having the above slider 190 will be described with reference to Figs. 2, 8, 9 and 10. The slider 190 is moved through the control 192. The slider 190 is fixed by the click 193 to position the total reflection mirror on the optical axis. As a result, the illumination light from the lamphouse 162 is reflected by the total reflection mirror 165 and irradiated on a condenser lens 170. The illumination light irradiated on the condenser lens 170 is condensed on a joint portion 173 through the condenser lens 170. The dark field illumination light condensed on the joint portion 173 is guided, through an optical fiber tube 175, to an annular light source section (i.e., an annular illuminating section) 176 (see Figs. 2 and 8) detachably mounted in a bright/dark field revolver 158. The illumination light guided to the annular light source section 176 is irradiated on an annular condenser lens 187 through an annular lens 183 provided to oppose the annular light source section 176 to irradiate a specimen 182 on a stage 181 as the dark field illumination light. The diffracted light reflected by the specimen 182 is irradiated on a imaging lens (not shown) by a bright/dark field objective lens 180 through the bright/dark field revolver 158 and a half mirror 179. The dark field observation of the surface of the specimen 182 is performed through an eyepiece 156 by observing the image formed by the imaging lens. The slider 190 is moved by the control 192. The slider 190 is fixed by the slick 193 to position the hole portion 195 on the optical axis. As a result, the illumination light from the lamphouse 162 is irradiated on the bright field system projection tube 151 through the hole portion 195. The illumination light imparted with a predetermined optical characteristics by the bright field system projection tube 151 is incident on the bright/dark field objective lens 180 through the half mirror 179 and irradiated on the specimen 182 on the stage 181 as the bright field system illumination light. The light reflected by the specimen 182 is radiated on the imaging lens (not shown) through the bright/dark field objective lens 180, the bright/dark field revolver 158, and the half mirror 179. The bright field system observation for the surface of the specimen 182 is performed through the eyepiece 156 by observing the image formed by the imaging lens. The slider 190 is-moved through the control 192. The slider 190 is fixed by the click 193 to position the filter box 194 along the optical axis. As a result, the illumination light from the lamphouse 162 and imparted with the predetermined optical characteristic is irradiated on the specimen 182, and predetermined optical observation is performed. With the microscope illuminating apparatus having the arrangement described above, a similar effect to that obtained in the eleventh embodiment can be obtained. In addition, since the filter box 194 is mounted on the slider 190, an auxiliary filter 196 other than the filter inserted in the illumination optical path of the reflected bright field system projection tube 151 can be additionally inserted in the illumination optical path, and switching among reflected dark field observation, reflected bright field system observations, and other optical observation can be performed within a short period of time by moving the slider 190. A microscope illuminating apparatus according to the fourth embodiment of the present invention will be described with reference to Fig. 11. Note that the same portions as in the above embodiments are denoted by the same reference numerals, and a detailed description thereof is omitted. As shown in Fig. 11, a bright field system projection tube 151 is removed from a system microscope to which the microscope illuminating apparatus according to the fourth embodiment is applied. A dark field illumination unit 153, a transmitting illumination lamphouse 201, a connection cord 202, a control 203, and the like are provided to the lower portion of a microscope body 150 in the same manner as in the embodiments described above. The dark field illumination unit 153 incorporates a mirror 205 having a different transmittance. As a result, the illumination light generated by the lamp 200 is radiated on the mirror 205 through a collector lens 206. Part of the illumination light irradiated on the mirror 205 is reflected by the mirror 205 to be incident on an attachment 164. Another part of the illumination light is transmitted through the mirror 205 and is guided to the microscope body 150. The microscope body 150 has a pair of lenses 208 and 209 for guiding the illumination light guided to the microscope body 150 to a reflecting mirror 207, a field stop 210, and an aperture stop 211. As a result, the illumination light guided through the above optical system is focused on a specimen 182 (see Fig. 8) on a stage 181 through a condenser lens 212. The lens 208 has a function of converting the parallel illumination light incident on it to Koehler illumination light. The illumination light incident on the attachment 164 is guided to an annular light source section (i.e., an annular illuminating section) 179 through an optical fiber tube 175 and irradiated on the specimen 182 on the stage 181 through an annular condenser lens (see Fig. 8). As a result, transmission bright field system observation and reflected dark field observation of the specimen 182 can be simultaneously performed. The dark field illumination unit 153 of this embodiment is mounted by engaging portions 152 and 160 identical to those described above to be rotatable through 360° about an optical axis. In this embodiment, since the light source of the transmission illumination lamphouse 201 can be commonly used as the light source for dark system illumination, a low manufacturing cost can be achieved. The present invention is not limited to the arrangements of the embodiments described above, and various changes and modifications can be made without departing from the scope of the invention as defined in the claims.

Claims: A microscope illuminating apparatus comprising: a condensor (85) mounted on a system microscope to condense illumination light on an observation field, said condensor comprising a condensor lens (88) serving as an illumination source for bright field illumination light in order to condense the bright field illumination light on the observation field; and an annular illumination section (87) serving as an illumination source for dark field illumination light in order to condense the dark field illumination light on the observation field; an illumination unit (67, 90) being connected optically to said condensor lens (88) and said annular illumination section (87); and switching means (80) connected to said illumination unit (67,) to perform selective switching between bright field illumination and dark field illumination; characterized in that said switching means are constructed such as to allow switching an illumination beam emitted from said light source (66) between an optical path through said condenser lens (88) and an optical path through an incident end (84a) of an optical fibre bundle (84), the exit end (84b) thereof being annularly disposed and optically coupled to said annular illumination section (87). An apparatus according to claim 1, characterized in that said switching means (80) comprises a half mirror or beam splitting means and control means for selectively adjusting a ratio in quantity of light of the bright field illumination light to the dark field illumination light as required.

Inventors: NAGANO TAKASHI, OSA KAZUHIKO, TAMURA KEISUKE, NAGANO, TAKASHI, OSA, KAZUHIKO, TAMURA, KEISUKE, Nagano, Takashi, c/o Intellectual Prop. Legal Dept, Osa, Kazuhiko, c/o Intellectual Prop. Legal Dept., Tamura, Keisuke, c/o Intellectual Prop. Legal Dept
Applicants: OLYMPUS OPTICAL CO, OLYMPUS OPTICAL CO., LTD.
Application year: 1992
Main classification: G02B21
IPC codes: G02B21