Patent Description:
In order to uniformly illuminate a field of vision, there is a microscope with a fly-eye lens (refer to <CIT>, hereinafter Patent Document <NUM>, for example).

Also forming part of the state of the art relative to the present disclosure are <CIT>, <CIT>, and <CIT>.

It is desired to perform more uniform illumination using a microscope with a fly-eye lens.

In one aspect of the present invention, there is provided a microscope according to claim <NUM> below.

The dependent claims define particular embodiments of the present invention.

Hereinafter, some embodiments of the present invention will be described. The embodiments do not limit the invention according to the claims, and not all the combinations of the features described in the embodiments are necessarily essential to means provided by aspects of the invention.

<FIG> is a schematic diagram of a microscope <NUM>. The microscope <NUM> includes an observation optical system <NUM>, an illumination optical system <NUM>, and a light source <NUM>.

The observation optical system <NUM> forms an image of a sample <NUM>. The observation optical system <NUM> has an eye piece <NUM> and an objective lens <NUM>.

The objective lens <NUM> is disposed directly under the sample <NUM> placed on a stage <NUM>, so as to face toward the sample <NUM>. In the example of the diagram, a plurality of objective lenses <NUM> are attached to a revolver <NUM>, where the plurality of objective lenses <NUM> have respective magnification and objective pupil diameters of the objective lenses, which are different from each other.

The stage <NUM> has an observation hole that allows illumination and observation of the sample <NUM> from the lower side of the diagram, and the sample <NUM> is placed on the stage <NUM> to be an object for observation. Also, the stage <NUM> can be moved separately in the horizontal direction or the vertical direction in an environment where the microscope <NUM> is put down.

The illumination optical system <NUM> irradiates illumination light emitted from the light source <NUM> to the sample <NUM>. A filter cube <NUM> is disposed directly under the objective lens <NUM>. The filter cube <NUM> will be described below in detail.

<FIG> is a schematic diagram showing an optical configuration of the microscope <NUM>.

The observation optical system <NUM> includes the objective lens <NUM>, the filter cube <NUM>, an imaging lens <NUM>, a plurality of relay lenses <NUM>, <NUM>, and <NUM> and a plurality of reflection mirrors <NUM>, <NUM>, and <NUM>.

The objective lens <NUM> is disposed such that it faces toward an observation surface <NUM> for a sample <NUM>. Through the objective lens <NUM> and the imaging lens <NUM>, a primary image <NUM> of the sample <NUM> placed on the stage <NUM> is formed.

A secondary image <NUM> is formed via the relay lenses <NUM>, <NUM>, and <NUM> which relay the primary image <NUM> formed by the imaging lens <NUM>. A user of the microscope <NUM> observes the secondary image <NUM> through the eye piece <NUM>.

The filter cube <NUM> is disposed between the objective lens <NUM> and the imaging lens <NUM>. The filter cube <NUM> has an excitation filter <NUM>, a dichroic mirror <NUM>, and a barrier filter <NUM>. The excitation filter <NUM> has a characteristic of, for example, selectively transmitting light in a bandwidth that generates fluorescence to the sample <NUM> (excitation light), while blocking light in the other bandwidths.

The dichroic mirror <NUM> reflects illumination light irradiated from the illumination optical system <NUM>, as well as transmitting observation light such as fluorescence emanated from the sample <NUM>. Thereby, the illumination optical system <NUM> can perform illumination or excitation of the sample <NUM> from the same side of the objective lens <NUM>. The barrier filter <NUM> has a characteristic of blocking light in bandwidths, except where the fluorescence is emanated from the sample <NUM>.

The reflection mirrors <NUM>, <NUM> and <NUM> bend an optical path of the observation optical system <NUM>.

The microscope <NUM> includes a second observation optical system <NUM>, and a camera <NUM> that takes an observed image formed by the second observation system <NUM>. The second observation optical system <NUM> shares the objective lens <NUM>, the filter cube <NUM>, and the imaging lens <NUM> with the observation optical system <NUM>. Also, the second observation optical system <NUM> has relay lenses <NUM> and a prism <NUM>. The prism <NUM> is replaceably disposed on an optical path of the second observation optical system <NUM> to reflect observation light and direct it to the relay lenses <NUM>. The relay lenses <NUM> direct the reflected observation light to the camera <NUM> to form an image. The camera <NUM> uses an image sensor such as a CCD sensor or a CMOS sensor to convert the observed image into an electrical signal to output.

The illumination optical system <NUM> has a collector lens <NUM>, a fly-eye lens <NUM>, relay lenses <NUM> and <NUM>, and a field stop <NUM>. In addition, the objective lens <NUM> in the observation optical system <NUM> also acts as a condenser lens in the illumination optical system <NUM>. Furthermore, the illumination optical system <NUM> shares the filter cube <NUM> with the observation optical system <NUM>.

A light emitter such as an LED, an LD or the like is used as the light source <NUM>. The collector lens <NUM> is disposed at a position where its front focus coincide with a light-emitting surface of the light source <NUM>, and makes illumination light emitted from the light source <NUM> into substantially parallel light.

As shown in <FIG>, the fly-eye lens <NUM> has a plurality of lens elements <NUM>.

The illumination light radiated from the light source <NUM> and made into substantially parallel light at the collector lens <NUM> enters an incident end surface of the fly-eye lens <NUM>. Also, on an emission end surface of the fly-eye lens <NUM>, a light source image of the light source <NUM> is formed on each lens element <NUM>.

A pair of relay lenses <NUM> and <NUM> is disposed between the fly-eye lens <NUM> and the objective lens <NUM>. The emission end surface of the fly-eye lens <NUM> is disposed at a pupil conjugate position which is a position conjugate to a pupil position (rear focal position) of the objective lens <NUM>, or vicinity thereto. Note that, the vicinity of the pupil conjugate position is within ±<NUM> from the pupil conjugate position, for example.

The incident end surface of the fly-eye lens <NUM> is disposed at a position conjugate to the field stop <NUM>. In the example of <FIG>, the field stop <NUM> is disposed between the pair of relay lenses <NUM> and <NUM>.

As described above, since the emission end surface of the fly-eye lens <NUM> is disposed at a position conjugate to the pupil position (rear focal position) of the objective lens <NUM> (pupil conjugate position) or vicinity thereto, images of the lens elements <NUM> are projected on the pupil of the objective lens <NUM> through the pair of relay lenses <NUM> and <NUM>, forming a secondary light source.

At a position for the field stop <NUM>, images on incident end surfaces of the plurality of lens elements <NUM> are formed such that they overlap with each other. An image conjugate to this image is formed on the observation surface <NUM> holding the sample <NUM>, and illuminate the sample <NUM>.

The illumination light source <NUM>, the collector lens <NUM> and the fly-eye lens <NUM> may collectively form a replacement unit <NUM>, which can be collectively replaced according to an application of the microscope <NUM>. For example, when using an LED with a long emission wavelength of <NUM>, a resin fly-eye lens <NUM> may be used. In this case, for example, the LED with a long emission wavelength of <NUM>, the collector lens <NUM>, and the resin fly-eye lens <NUM> may be combined so that to they can be collectively replaced. Also, when using an LED with a short emission wavelength of <NUM>, <NUM> etc., a quartz or silicone resin fly-eye lens <NUM> may be used. In this case, the LED with a short emission wavelength of <NUM>, <NUM> etc., the collector lens <NUM> and the quartz or silicone resin fly-eye lens <NUM> may be combined so that to they can be collectively replaced.

<FIG> is a drawing showing a configuration of the fly-eye lens <NUM>. The fly-eye lens <NUM> has a configuration in which the lens elements <NUM>, each of which is hexagonal, are disposed in a beehive (honeycomb) pattern. As one example, each lens element <NUM> has the same curvature radiuses on its incident side and emission side, and when a parallel luminous flux enters from the incident side, it is converged on the emission end surface.

(a) to (e) in <FIG> are drawings respectively showing images of fly-eye lenses <NUM>, <NUM>, <NUM>, <NUM> and <NUM> which are projected on a pupil surface of the objective lens <NUM>. In (a) to (e) of <FIG>, the sizes of pupils <NUM> are the same, whereas respective sizes of images <NUM> of the lens elements <NUM> projected on the pupils <NUM> are different.

Here, in (a) to (e) of <FIG>, the images <NUM> of the lens elements are projected on an outer perimeter of the pupils <NUM>. The inventers of the present invention have found out that the images <NUM> of the lens elements projected on the outer perimeter of the pupils <NUM> affect unevenness in the illumination light. For example, in (a) of <FIG>, because ratio of the images <NUM> of the lens element that pass through the pupil <NUM> to the images <NUM> projected on the outer perimeter of the pupil <NUM>, that is, proportion of the images <NUM> contributing as illumination light differs between the X1 direction and the X2 direction in the drawing, two-dimensional unevenness in the illumination light is affected. The same can be said for the direction Y1 and the direction Y2 in the drawing (b) of <FIG>.

Therefore, the inventers have examined effect of the lens elements <NUM> projected on the outer perimeter of the pupil <NUM> upon two-dimensional unevenness in the illumination light. Specifically, they have simulated, from (a) to (e) of <FIG>, their respective illuminance distributions on the observation surface <NUM>. In the simulation, the illuminance distributions are calculated in one-dimensional direction.

First, as shown in (a) of <FIG>, the number of the images <NUM> of the lens elements in the image <NUM> of the fly-eye lens projected on the pupil <NUM> is as follows. In an image <NUM> of the fly-eye lens, the number (n<NUM>) of the images <NUM> of the lens elements projected on the outer perimeter of the pupil <NUM> is <NUM>. In other words, n<NUM> is the number of the images <NUM> of the lens elements that cross the outer perimeter of the pupil <NUM>. On the other hand, the number (n<NUM>) of the images <NUM> of the lens elements projected inside the pupil <NUM> is <NUM>. In other words, n<NUM> is the number of the images <NUM> of the lens elements surrounded by the images <NUM> of the <NUM> lens elements that cross the outer perimeter of the pupil <NUM>.

n<NUM> and n<NUM> of the image <NUM> of the fly-eye lens shown in (b) of <FIG> are <NUM> and <NUM> respectively. Relations between the n<NUM> and n<NUM> are shown in Table <NUM>, together with other examples not shown in <FIG>.

<FIG> is a graph showing respective simulation results of illuminance distributions on the observation surface <NUM>, which correspond to (a) to (e) of <FIG>.

As shown in <FIG>, it is found out that, with respect to (a) to (e) of <FIG>, respectively, when the number (n<NUM>) of lens elements <NUM> projected inside the pupil <NUM> is greater than the number (n<NUM>) of lens elements <NUM> projected on the outer perimeter of the pupil <NUM> (that is, when n<NUM> > n<NUM>), change of illuminance is less than <NUM>% in the one-dimensional direction on the observation surface <NUM>. Thus, it can be assumed that the illuminance is substantially uniform as the change of illuminance is less than <NUM>% in the one-dimensional direction on the observation surface <NUM>, and the effect upon unevenness of the illuminance distribution in the two-dimensional direction can be reduced. In other words, by making n<NUM> > n<NUM>, the illuminance distribution in the one-dimensional direction on the observation surface <NUM> becomes substantially uniform, thus the effect upon unevenness in the illuminance distribution in the two-dimensional direction caused by the images <NUM> of the lens elements projected on the outer perimeter of the pupil <NUM> can be reduced. Accordingly, the unevenness in the two-dimensional direction on the observation surface <NUM> is reduced.

<FIG> is a diagram for explaining correspondence of an image <NUM> of the lens elements <NUM> with change of a pupil diameter in the microscope <NUM>. The microscope <NUM> includes the plurality of objective lenses <NUM> attached to the revolver <NUM>, and can easily switch between the objective lenses <NUM> to use for observation.

Upon changing the objective lens <NUM> to use, a pupil diameter may change. For example, when a magnification of the objective lens <NUM> is changed from × <NUM> to × <NUM>, a pupil diameter may get smaller. That is, upon changing the objective lens <NUM> to use, a pupil <NUM> may change to a pupil <NUM> as shown in <FIG>. Therefore, in the microscope <NUM>, the illumination optical system <NUM> is configured so as to maintain the above condition, i.e., n<NUM> > n<NUM>, even when the objective lens <NUM> is switched and a pupil diameter gets smaller, in order to realize a microscope <NUM> of which uniformity of illumination light illuminance on the observation surface <NUM> does not drop by changing the objective lens <NUM> to be formed.

In the example of <FIG>, the illumination optical system <NUM> can be configured so as to maintain the relation of n<NUM> > n<NUM>, even for the pupil <NUM> with a small pupil diameter.

In other words, a first objective lens having a first pupil diameter and a second objective lens having a second pupil diameter smaller than the first pupil diameter are switchable, and it is preferable to configure the illumination optical system <NUM> such that the number n<NUM> is greater than the number n<NUM> with respect to the second objective lens. Particularly, when using more than or equal to <NUM> switchable objective lenses having pupil diameters different from each other, it is preferable to configure the illumination optical system <NUM> such that the number n<NUM> is greater than the number n<NUM> with respect to an objective lens with the smallest pupil diameter among the plurality of objective lenses. Thereby, in the microscope <NUM>, even when the objective lens <NUM> with a small pupil diameter is selected, an entire field of vision is uniformly illuminated.

<FIG> is a schematic diagram showing a configuration of another illumination optical system <NUM>. The illumination optical system <NUM> has the same configuration as that of the illumination optical system <NUM> shown in <FIG> except for the portions described below, thereby the same reference numerals are used for the components in common and redundant descriptions are omitted.

The illumination optical system <NUM> is different from the illumination optical system <NUM>, as it has a variable magnification optical system <NUM> formed of a plurality of lenses instead of having one of the relay lenses <NUM>. When magnification of the variable magnification optical system <NUM> is changed, the size of an image of the fly-eye lens <NUM> to be projected on a pupil surface changes.

<FIG> is a drawing for explaining an image of the fly-eye lens <NUM> through the variable magnification optical system <NUM>. In certain magnification of the variable magnification optical system <NUM>, as shown in (A) of <FIG> for example, assume that, in an image <NUM> of the fly-eye lens, the number (n<NUM>) of images <NUM> of lens elements projected on an outer perimeter of a pupil <NUM> is <NUM>, whereas the number (n<NUM>) of images <NUM> of lens elements projected inside the pupil <NUM> is <NUM>.

In the illumination optical system <NUM>, by using the variable magnification optical system <NUM>, the size of an image of the fly-eye lens <NUM> to be projected on the pupil <NUM> can be changed. Therefore, as shown in (B) of <FIG>, n<NUM> and n<NUM> can be <NUM> and <NUM> respectively, by changing magnification of the variable magnification optical system <NUM> smaller to reduce the size of an image <NUM> of the fly-eye lens <NUM> more than the size of the image <NUM> of the fly-eye lens <NUM>. In this way, by using the variable magnification optical system <NUM>, the n<NUM> > n<NUM> condition can be satisfied without changing the fly-eye lens <NUM> itself.

<FIG> is a diagram showing an image of the light source <NUM> projected on an emission surface of the fly-eye lens <NUM> in the illumination optical system <NUM>. Shown in the illustrated example is a case in which an LED with a square light-emitting surface is used as the light source <NUM>. As shown in <FIG>, a is a length of each side of the light source <NUM>. Also, a gap between parallel sides opposing to each other of the lens element <NUM> is equal to an element pitch p.

Magnification of the light source <NUM> projected on the emission surface of the fly-eye lens <NUM> can be expressed by (fFE/fcl), where fcl and fFE are the focal distance of the collector lens <NUM> and the focal distance of the lens elements <NUM> respectively. Thus, the length of one side of the image of the light source <NUM> projected on the emission surface of the fly-eye lens <NUM> is (fFE/fcl)a, and the area in which the LED is projected on each of the emission surfaces of the lens elements <NUM> can be expressed by (fFE/fcl)<NUM>a<NUM>.

The area of the emission surfaces of the lens elements <NUM> is ((<NUM><NUM>/<NUM>·p<NUM>)/<NUM>). Here, as shown in an image <NUM> of the light source <NUM>, when the image of the light source <NUM> is projected inside the emission surface of the lens element <NUM>, a filling rate of the image of the light source <NUM> in the lens element <NUM> can be defined as a ratio of the area of the image of the light source <NUM> to the area of the lens element <NUM>.

With respect to the above definition, it is preferable for the filling rate to be more than or equal to <NUM>%. It is because, if the filling rate is less than <NUM>%, the area of the image of the light source <NUM> in a pupil <NUM> is reduced, and thus a substantial NA drops. A condition therefor of the illumination optical system <NUM> is expressed as follows, where a is the length of one side of the light source <NUM>.

When an image of the light source <NUM> is larger than the emission surface of the lens element <NUM>, such as the image <NUM> of the light source <NUM> for example, it is preferable to make the length of one side of the image of the light source <NUM> shorter than a maximum length of the lens element <NUM> (the distance between opposite vertices in <FIG>). It is because, if the length of one side of the image of the light source <NUM> on the lens element <NUM> is longer than the maximum length of the lens element <NUM>, it causes a loss of light amount and flare. Therefore, the pitch p of the lens element <NUM> is expressed as follows, where a is the one side length of the light source <NUM>.

The following condition can be formed from the two equations above.

<FIG> is a diagram showing an image of a light source <NUM> projected on the emission surface of the fly-eye lens <NUM> in the illumination optical system <NUM>. Shown in the illustrated example is a case in which the light source <NUM> (an optical fiber <NUM>) with diameter b is used instead of the light source <NUM>.

From a similar consideration to the above case in <FIG>, the diameter and the area of the image of the optical fiber <NUM> projected on the emission surface of the lens element <NUM> are expressed by (fFE/fcl)b and π(fFE/fcl)<NUM>(b/<NUM>)<NUM> respectively. In the case of using the optical fiber <NUM> also, it is preferable for the filling rate to be more than or equal to <NUM>% when the image of the optical fiber <NUM> is projected inside the emission surface of the lens element <NUM> in a similar manner as that in <FIG> described above (an image <NUM> in <FIG>). Also, when the image of the optical fiber <NUM> is larger than the emission surface of the lens element <NUM> (an image <NUM> in <FIG>), it is preferable to make the diameter of the image of the optical fiber <NUM> shorter than a maximum length (the distance between opposite vertices in <FIG>) of the lens element <NUM>. Therefore, the pitch p of the lens element <NUM> is expressed as follows, where b is the diameter of the optical fiber <NUM>.

Hereinafter, an acceptance angle NA' of light radiated from the light source <NUM> is described. When an emission angle of the light source <NUM> is θ, the light intensity is rcos θ. In that case, a microvolume ΔV of the space shown with the polar coordinate shown in <FIG> can be expressed by the following Equation <NUM>.

Equation <NUM> is obtained by integrating this equation, which expresses an acceptance light amount in the range within the emission angle θ from a single point of the light-emitting surface of the light source <NUM>.

Here, considering a loss of the light amount, it is preferable to keep more than or equal to approximately <NUM>% of the acceptance light amount from the single point of the light-emitting surface. Assume that θ1 is an emission angle at which more than or equal to <NUM>% of acceptance light amount can be kept, and consider that the emission angle is <NUM>° when the acceptance light amount is <NUM>%, the equation therefor is as follows. <MAT> The relation in Equation <NUM> is obtained by solving cos θ1 on this equation and expressing the result by sin θ1.

Since the acceptance angle NA' is n·sin θ1, and n=<NUM> in the illumination optical system <NUM>, the following Equation <NUM> is obtained after rounding off to two decimal places. <MAT> Thus, by setting each optical parameter such that it satisfies the following Equation <NUM>, more light amount can be taken from the light source <NUM>.

In the above example, although an LED is used as the light source <NUM> in the illumination optical system <NUM>, it is obvious that the illumination optical system <NUM> with the fly-eye lens <NUM> can also accommodate another light source <NUM>, such as a halogen lamp. Also, an emission end which is a waveguide for an optical fiber or the like that introduces illumination light supplied from the outside can be used as the light source <NUM>.

Note that, in the above example, the illumination optical system <NUM> is used for vertical illumination. However, such illumination optical system <NUM> with the fly-eye lens <NUM> described above can also be used for illumination of the sample <NUM> in transmission illumination observation using the microscope <NUM>. Also, the above illumination optical system <NUM> may irradiate illumination light for bright field observation, or may irradiate excitation light for fluorescence observation.

While the embodiments of the present invention have been described, the technical scope of the invention is not limited to the above described embodiments. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiments. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the invention.

Claim 1:
A microscope (<NUM>) comprising:
an observation optical system (<NUM>) having an objective lens (<NUM>) having a predetermined pupil diameter; and
an illumination optical system (<NUM>) having a fly-eye lens (<NUM>) and configured to irradiate light from a light source (<NUM>) to a sample (<NUM>) through the fly-eye lens and the objective lens,
the fly-eye lens has a plurality of lens elements (<NUM>);
in the illumination optical system, images of the plurality of lens elements are projected inside and on an outer perimeter of a pupil of the objective lens;
the images of lens elements projected inside the pupil of the objective lens are images which are surrounded by the images of lens elements which are projected on the outer perimeter of the pupil of the objective lens; characterized in that
a number (m) of images of the lens elements projected inside the pupil of the objective lens is more than a number (n<NUM>) of images of the lens elements projected on the outer perimeter of the pupil of the objective lens, wherein
a plurality of objective lenses having respective pupil diameters different from each other are switchable; and
the number n<NUM> is greater than the number n<NUM> with respect to an objective lens with the smallest pupil diameter among the plurality of objective lenses.