JPH01110239A - Precise differential refractometer - Google Patents

Abstract

PURPOSE:To eliminate the unstableness of optical axes at parts of an optical system due to a geometric change or the like caused by mechanical vibration and aging of material of apparatus, by fastening on a box frame body a collimator section and a telescope section optically connected with a retroreflector. CONSTITUTION:Light from a light source 2 is condensed onto a slit 6 via a condenser lens 3 and a small reflection mirror 4 and passes through a collimator section 8 to emit a parallel light beam. This parallel light beam is turned back reversely with a retroreflector (corner cube) 13 maintaining parallelism with an outgoing light and incident into a telescope objective mirror 9 via a differential section 18 with a V-block prism 16 which carries a reference sample or a sample 17 to be inspected on a sample base 15 to form an image of the slit 6. The position of the image is measured with a light position detector 19. It should be noted that a telescope section 11 provided with the collimator section 8, a lens section 9 and an opening 10 is fastened on a one-piece stainless steel box frame body 5 divided vertically in two inside along an optical path thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a precision differential refractometer used for measuring the refractive index of solids or liquids.

[Prior Art] A differential refractometer has been known as a solid or liquid refractive index measuring device. Usually, as shown in FIG. 5 of the appendix, this device linearly and sequentially moves a monochromatic light source section 2, a collimator 8 having a slit 6 and an objective lens 7, and a refractor on a surface plate 1 according to a light beam path. V-block prism with known rate value or V-prism cell containing sample solution 1
6, a telescope 1 equipped with a differential section 18 and an objective lens 9.
1 and the telescope 11, a micrometer or optical position detector 19 for measuring the imaging position of the slit 6 is arranged. For example, in the case of a solid sample, the measurement operation is performed in advance by
A reference sample having the same refractive index and an apex angle of 90' is placed on the block prism via a liquid film having approximately the same refractive index, and measurement is performed for reference alignment. The object sample is similarly measured, and the refractive index of the object sample is determined from the difference from the former measurement.

[Problem to be solved] However, in the conventional technology described above, in order to improve the measurement accuracy, it is necessary to increase the focal length of the collimator and the telescope due to the design. The installed equipment is extremely large. For this reason, conventional differential refractometers have poor mechanical stability, and are affected by vibrations and deflection due to changes in the surface plate over time, which can cause misalignment of the collimator and telescope, and the optical axis of each part of the optical system. The disadvantage is that the angular stability deteriorates, making it difficult to obtain high measurement accuracy.

SUMMARY OF THE INVENTION In view of the drawbacks of the prior art, it is an object of the present invention to provide a precision differential refractometer with excellent mechanical stability and extremely high precision.

[Means for solving the problem] In order to achieve the above-mentioned purpose, Ki-ai Kirisha conducted various tests and research, and found that the collimator section and the telescope section were fixed to a strong box frame body, and the above-mentioned solution was achieved. By arranging a retroreflector between the optical paths of the collimator section and the telescope section, which maintains the angular relationship between the incident and reflected rays accurately and constant even if there is a slight change in position, the two sections are coupled together. The inventors have found that the above object can be achieved and have completed the present invention.

That is, the feature of the configuration of the precision differential refractometer according to the present invention is that the light source section, collimator section, and
In a differential refractometer equipped with a differential section, a telescope section, and an optical position detector, the collimator section and telescope section are fixed to a strong box frame, and the light rays emitted from the collimator section are directed in parallel in opposite directions. The reason is that a retroreflector is provided between the optical path of the collimator section and the telescope section so that the light is reflected back and enters the telescope section.

In the precision differential refractometer of the present invention, it is preferable that the collimator section and the telescope section are arranged in parallel within the box frame because this arrangement is simpler than other arrangements. Further, the internal configurations of both of these parts may be either a lens system or a reflection system, or both parts may be a combination of different systems. However, in order to avoid chromatic aberration over a wide range of wavelengths and to measure without reducing the intensity of the UV light, it is even more preferable to provide reflective optical systems in both the collimator section and the telescope section.

In the precision differential refractometer of the present invention, the light source section, retroreflector, and differential section are generally placed on the surface plate, since even minute positional fluctuations do not affect measurement accuracy after they are installed at appropriate positions. However, it is preferable that the optical position detector is fixedly attached to the telescope box frame.゛[Example] Example 1 Solid-state refraction when an example of the precision differential refractometer according to the present invention is equipped with a collimator of a lens optical system, a telescope, and a retroreflector (corner cube) using an optical path medium. The refractometer for index measurement will be explained with reference to the drawings.

FIG. 1 is a partially transparent plan view of the entire apparatus, and FIG. 2 is a partially cutaway side view taken along line X--Y in FIG. This refractometer device consists of a surface plate L installed on an anti-vibration table (not shown), a monochromatic light source 2, a condensing lens 3, a small flat reflector 4, and an integral structure in which the interior is vertically divided into two along the optical path. A stainless steel box frame 5, a collimator section 8 equipped with a slit 6 and an objective lens 7 attached to one division of the box frame 5, and a collimator section 8 attached to the other division of the box frame 5 in parallel with the collimator section 8. and a telescope section 11, which includes a lens 9 and an aperture 10, each having an optical axis parallel to the optical axis of the telescope section 11. An optical path tube 12 , a corner cube 13 supported by a support 14 , a differential section 18 having a V-block prism 16 on which a reference sample or a subject sample 17 is placed on a sample stage 15 , and a support fixed to the box frame 5 An optical position detector 19 fixed on a table 20 is provided.

This optical position detector consists of a vibrating slit, a micro-movement device, a micrometer, and a photoelectric detector (not shown).

In the figure, light emitted from a light source 2 passes through a condenser lens 3 and a small reflecting mirror 4, is condensed onto a slit 6, passes through a collimator section 8, and is emitted as a parallel beam. This parallel light ray is turned back in the opposite direction by the corner cube 13 while maintaining a parallel relationship with the optical axis of the emitted light, and the differential section 1
Go to 8.

The light enters the telescope objective lens 9 and forms an image of the slit 6. The position of this image is measured by an optical position detector 19.

When the refractive index of a subject was measured in a daily work environment using the refractometer configured in this example, it was found that conventional refractometers were unable to guarantee a refractive index value on the order of 10-5. On the other hand, it was possible to easily guarantee a value on the order of 10-6, and the measurement accuracy was significantly improved.

Example 2 Another example of the precision differential refractometer according to the present invention is used for solid refractive index measurement when equipped with a reflective optical system collimator and telescope, and an achromatic retroreflector that does not use an optical path medium. A similar statement will be made regarding the refractometer.

FIG. 3 is a partially transparent plan view of this embodiment, and FIG. 4 is a partially cutaway side view taken along line X--Y in FIG. In the figure,
This refractometer includes a surface plate 1, a white or monochromatic light source 2, a quartz condensing lens 3, a monochromator 21 capable of selecting light of any wavelength, a condensing optical system device 22, a small flat reflecting mirror 4, and the above-mentioned implementation. Similar to Example 1, the cast iron box frame 5' has an integral structure with the interior vertically divided into two parts, the slit 6 attached to one division of the box frame 5', and the upper planes arranged diagonally opposite each other on the same vertical plane. A collimator section 8' includes a reflector 23 and a lower concave reflector 24, a lower concave reflector 26 and an upper flat reflector 25 arranged in the same manner as the collimator section 8', and the collimator section 8' A telescope section 11' arranged in parallel with the optical axis parallel to the optical axis, an achromatic retroreflector 13' fixed on the support 14, and fixed on the support 20 measure a wide wavelength range. It is equipped with an optical position detector 19' with possible high sensitivity COD.

This reflective optical system refractometer maintains high accuracy by
The collimator section and the telescope section have the above structure because they need to have a long focal point and are designed to cancel out aberrations. The light incident on the collimator section 8' is reflected by the upper plane reflecting mirror 23, then reflected again by the lower concave reflecting mirror 24, and is emitted as parallel light beams, which are then directed toward the reflector 13'.

The light passes through the differential section 18, enters the telescope section 11', is reflected and condensed by the lower concave reflecting mirror 26, is reflected by the upper flat reflecting mirror 25, and is focused by the optical position detector 19'.

When the refractive index of the object was measured using the refractometer of this example, it was possible to easily guarantee a value on the order of 1O-6, as in Example 1. Furthermore, the refractometer of this embodiment has the advantage that the entire optical system can select any wavelength from a wide wavelength range ranging from visible light to ultraviolet rays and infrared rays, so that the measurement can be applied in a very wide range of applications.

Although the embodiments have been described above, the precision differential refractometer of the present invention is not limited to the above embodiments. For example, the collimator section and the telescope section within the box frame may be arranged in parallel on a vertical plane, and are not necessarily limited to the above embodiments. It is not necessary to arrange these in parallel, and the material of the box frame body may be a known low-expansion ceramic or metal with sufficient mechanical strength, etc., as long as it does not deviate from the basic technical idea of the present invention. It can be changed as appropriate.

[Effects of the Invention] As explained above, the precision differential refractometer of the present invention optically couples the collimator section and the telescope section by introducing the retroreflector, and fixes them to the box frame. This eliminates the instability of the optical axis of each part of the optical system due to mechanical vibrations or changes in the shape of the equipment material over time, making it easier and more stable to measure refractive index with higher precision than before. be able to.

[Brief explanation of the drawing]

FIG. 1 is a partially transparent plan view of an embodiment of the present invention;
FIG. 2 is a partially cutaway side view taken along line X-Y in FIG. 1. Third
and FIG. 4 are similar views of other embodiments of the invention. FIG. 5 is a side view of a conventional device. (Symbol) 2...Φ...Light source 3...Reference...Condenser lens 4...Small flat reflector 6...Work...・Slit 7.9...Objective lens 8.8'...Collimator section 10.10'...Aperture 11.11'...Telescope section 13.13 '...Retroreflector-16...
...Fist -■Block prism 17・Meeting...Sample 19.19'...Optical position detector 21-...Monochromator-22...
... Condensing optical system device 23.25 - ... Planar reflector 24.26 Conflict ... Concave reflector Patent applicant OHARA Co., Ltd.

Claims (3)

[Claims] (1) In a differential refractometer equipped with a light source section, a collimator section, a differential section, a telescope section, and an optical position detector, the collimator section and the telescope section are fixed to the box frame body in order according to the beam path, and A precision differential refractometer characterized by a retroreflector provided between the optical path of the collimator section and the telescope section. (2) A precision differential refractometer according to claim (1), characterized in that the collimator section and the telescope section are arranged in parallel and fixed to the box frame. (3) A precision differential refractometer according to claims (1) and (2), wherein the collimator section and the telescope section are reflective optical systems.