JPS5949514A - Annular illumination device - Google Patents

Abstract

PURPOSE:To reduce the luminous flux intercepted by an annular aperture stop to improve the illumination efficiency considerably and make the field of illumination bright to shorten the exposure time, by converting the luminous flux of a light source to annular luminous flux. CONSTITUTION:The laser luminous flux from a light source 1 is converted to an approximately cylindrical luminous flux by a beam expander and is transmitted through a mat glass 3 to be made incoherent slightly, and the occurrence of speckle patterns is prevented, and the focusing capacity is improved. The transmitted light of the glass 3 is made incident from a round end face 4a of an optical fiber 4 and is emitted from an annular or a pair of arc-shaped exit end faces 4b to be converted to an annular luminous flux, and this luminous flux is condensed near an annular aperture stop 6 by an annular condenser lens 5. The luminous flux transmitted through the stop 6 illuminates an object face 8 uniformly without variance by a condenser lens 7. The luminous flux incident to an object lens 9 is focused temporarily and is intercepted by an annular filter 10 in this focus position to prevent the illumination luminous flux from being incident to an observing system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an annular illumination device for a phase contrast microscope, a dark field microscope, etc.

Conventional phase-contrast microscopes, dark-field microscopes, etc. collect light from a light source using a condensing lens to form a light source image, and place an annular aperture diaphragm with an annular aperture at the position of this light source image. An annular illumination device is known in which an annular light beam passing through the aperture diaphragm is used as illumination light.

In a lighting device configured in this manner, only a small portion of the light from the light source can pass through the annular aperture diaphragm, resulting in poor lighting efficiency and a dark illuminated field. In particular, images of objects near the resolution limit of the observation optical system do not have sufficient contrast, and it is desirable to use a filter with low transmittance when observing such objects, but this makes the illumination field even darker. , the exposure time for photography is long,
It was inconvenient. Further, in the case of an IC pattern precision reduction optical system, the exposure time on the wafer becomes long, resulting in a decrease in work efficiency.

In view of the above points, the present invention aims to provide an annular illumination device with sufficient brightness.This will be explained below with reference to embodiments shown in the drawings. 1 is a light source such as a laser tube, 2 is a beam expander that converts the light beam from the light source 1 into a cylindrical light beam, and 13 is a beam expander that reduces the coherence of the laser beam. In order to erase the mesh with matte glass, a minute vibration is applied in a direction perpendicular to the optical axis, as is known in the art. Reference numeral 4 denotes an optical fiber whose left end has one circular end surface 4a in the drawing, and whose right end has an annular or paired arc-shaped exit end surface 4b; 5 indicates an exit end surface 4b of the optical fiber 4; 7 is a condenser lens; 8 is an object surface to be illuminated; 9 is an objective lens; It's a filter.

Since the embodiment of the present invention shown in FIG. This makes it slightly incoherent, preventing the generation of speckle patterns and improving imaging performance.

- The cylindrical light beam transmitted through the matte glass 3 enters the circular end surface 4a of the optical fiber 4 and exits from the annular or paired arc-shaped exit end surface 4b, thereby converting it into an annular light beam, which is converted into an annular condensing lens. 5, the light is focused near the annular aperture stop 6.

The light beam passing through the aperture diaphragm illuminates the object surface 8 uniformly and evenly through the condenser lens 7. Note that the light beam passing through the object plane 8 and entering the objective lens 9 forms an image, and this image is blocked by the annular filter 10 disposed at a certain position to prevent the illumination light beam from entering the observation system. be.

FIG. 2 shows a case of an epi-reflection imaging system, particularly an IC pattern precision reduction optical system, and the same members as in FIG. 11 uniformly illuminates the master 12 of the mask pattern without loss of light quantity, and also has an annular aperture diaphragm! A field lens 14 images the master 12 onto the annular filter 13, and 14 is a precision high-M image reduction lens which also functions as a condenser lens, and images the master 12 onto the silicon wafer 15 on which a mask pattern is to be formed.

Since this embodiment is configured as described above, the light from the light source 1 is transmitted to the beam expander 2 as in FIG. Matte glass 3. Illumination is efficiently and uniformly carried out through the optical fiber 4I annular condenser lens 5 and annular aperture diaphragm 6, and further by the field lens 11. Therefore master 12
The silicon wafer 15 is connected to the precision high-resolution reduction lens 14.
The illumination light beam is imaged onto the silicon wafer 15 and is blocked by the annular filter 13 so as not to reach the silicon wafer 15 .

Here, since the precision high-resolution reduction lens 14 also acts as a condenser lens, the silicon wafer 15
A very bright image is formed above.

3 to 5 show optical systems that can be used in place of the optical fiber 4 in FIG. 2, and FIG. 3 shows an optical system 21 consisting of a pair of concentrically arranged conical mirrors. 4 shows an optical system 22 consisting of similarly arranged afocal spherical mirrors, and Fig. 5 shows an optical system 23 consisting of a pair of concentrically arranged afocal aspherical mirrors, with small mirrors 23a and Both or one of the large mirrors 23b is a press-molded aspherical surface.

In either case, the cylindrical light beam transmitted through the matte glass 3 is converted into an annular light beam.

FIG. 6 shows an annular light source in which a plurality of light sources such as laser tubes and beam expanders are arranged at equal angular intervals in an annular shape, and one large matte glass 3' is provided. Beam expander - 2° matte glass 3. It can be used in place of the optical fiber 4 and provides a brighter illumination field.

FIG. 7 shows an aspheric annular condensing optical system 24, in which both or one of the small mirror 24a and the large mirror 24b is a press-molded toric surface mirror, instead of the optical fiber 4 and the annular condensing lens 5 in FIG. can be used for.

That is, the cylindrical light beam transmitted through the matte glass 3 is converted into an annular light beam condensed at the annular aperture diaphragm.

In the cases of FIGS. 4, 5, and 7, the light flux in the shaded area is lost, but this is less than 25 times the total light amount and does not pose a problem in practice. It goes without saying that each of the optical systems shown in FIGS. 3 to 7 can be applied to the embodiment shown in FIG.

As described above, according to the present invention, by using an optical member that converts the luminous flux from the light source into an annular luminous flux,
Since most of the light from the light source is converted into an annular luminous flux and made incident on the annular aperture diaphragm so that it can be used as illumination light, the luminous flux blocked by the annular aperture diaphragm is greatly reduced.
Therefore, the illumination efficiency is significantly improved, the illumination field is brighter because a high-intensity light source is used, and the exposure time during photography is shortened. When a lighting device is applied, very favorable results can be obtained.

In the above explanation, a laser tube is used as the light source, but the light source is not limited to this, and high-intensity discharge tubes such as ultra-high-pressure mercury lamps, xenon arc lamps, xenon flanilles, or high-intensity iodine lamps may also be used. Although preferred, other light sources can also be used. In this case, the matte glasses 3, 3' are omitted. Further, in the embodiment shown in FIG. 2, the optical fiber 4 itself makes the laser beam incoherent to the extent that it becomes incoherent, so the matte glass 3 may be unnecessary. Furthermore, argon laser (5145A, 48
When using a helium-neon laser (80λ), a high output of 1 to 10W can be obtained, so there is no need to use multiple laser tubes as shown in Figure 6.
328 large) can also be used, in this case 1 to 2
An output of 00mW can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the optical system of the first embodiment of the annular illumination device according to the present invention, FIG. 2 is a diagram similar to FIG. 1 showing the second embodiment, and FIGS. 3 to 7 FIG. 2 is a diagram showing another embodiment of a reservoir that generates an annular light beam. 1°-11L, 2...beam expander,
3...Matte glass, 4...Optical fiber, 5
... Annular condensing lens, 6... Annular aperture diaphragm, 7. Mountain condenser lens, 8. Object surface, 9.
Middle objective lens, ]0113... annular filter,
11... Field lens, 12... Master, 14
...Precise high-resolution m-reflection lens, 15...Silicon wafer, 21.22.23...Afocal optical system, 24...Aspheric annular focusing optical system. :#3 Figure 21 3b Figure 16 Orr Figure 4b

Claims (1)

[Claims] a light source, a first optical member that converts the luminous flux from the light source into a cylindrical luminous flux, a second optical member that converts the cylindrical luminous flux into an annular luminous flux and focuses the annular luminous flux; An annular illumination device comprising: an aperture diaphragm disposed and having an annular aperture corresponding to the annular luminous flux.