JPS63188744A - Differential automatic measuring instrument for optical refractive index - Google Patents

Abstract

PURPOSE:To automate the measurement of the refractive index of a transparent body and simplify the measuring operation, and to eliminate individual errors, etc., by inserting a shutter right behind a V block in an optical path and providing a sensor which detects the position of a slit image, etc. CONSTITUTION:Light emitted from a slit 3 is converted by a collimator lens 4 into parallel light, which passes through the V block 5 and a sample 6 and is converged by an image forming lens 8 through the shutter 7 to form an image on a CCD sensor 9 placed on its focal plane. An operator inputs the refractive index of the V block 5 to a measuring instrument previously, places the sample 6 whose refractive index is unknown on the V block 5, and presses a start switch provided to a control unit 10. Then this instrument measures and analyzes the image formation position of the image of the slit 3 formed with the luminous flux and displays the refractive index as the result. Further, the luminous flux is switched by the shutter 7 automatically immediately after a measurement of one side is taken. Thus, the measuring operation is simplified to remove individual errors, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for automatically measuring the refractive index of transparent bodies such as optical glasses and transparent liquids.

(Prior Art) The following three types of conventional refractive index measuring devices are mainly known.

■) A prismatic version of the spectrometer? The refractive index of the sample is calculated by applying the III polishing process, allowing light to enter from one surface and emitting from the other surface, and measuring the deflection angle of the emitted light.

■) Prufrich refractometer A sample with an unknown refractive index (V4) is placed on top of a transparent body (base prism) with a known refractive index.
A base prism is placed on the base prism (the surface of which has been polished so that Light is sequentially refracted and transmitted from the sample through the base prism and exits from the base prism side. The critical angle of this total reflection is measured and the refractive index is determined from this.

Although ordinary spectrometers and Pluffrich refractometers are both excellent measuring instruments, their drawbacks include that they require optical polishing to process the sample, and that it takes time and effort to adjust the measuring instruments and perform measurement operations.

■)■ Block type refractometer In order to improve the above-mentioned drawbacks, this V block type refractometer was developed. This is a 1937 Messers Chancebro
This refractometer was developed by Hers & Co., Ltd. and has a configuration as shown in FIG. That is, the light rays emitted from the light source 31 pass through the filter 32 and the slit 33, and are turned into a parallel beam by the collimator 34.
The light enters a V-block prism 35 made of a transparent material with a known refractive index. The first step in the measurement process is to first prepare a transparent sample 3 that has exactly the same refractive index as the V block.
6 (hereinafter referred to as a standard piece) is placed on the sample position using a contact liquid, and the position of the slit image formed on a scale provided in the eyepiece of the telescope 37 is measured. In the next step, a sample with an unknown refractive index is placed in place of the standard piece 36, and the position of the slit image is determined by 1 m11 in the same manner.

The refractive index of the sample whose refractive index is unknown is then calculated using a predetermined calculation formula by determining the amount of deviation (deflection) between the positions of the two imaging slit images.

There are two methods for measuring this declination: a) a fixed telescope type (differential type) and b) a movable telescope type. In the former case, the telescope 37 is always fixed as shown by the solid line in FIG. 7, but in the latter case, the telescope is moved as shown by the dotted line in FIG.

The V-block refractometer configured in this way does not require polishing the sample compared to a spectrometer or a Pulfrich refractometer.
(to use a contact liquid with a refractive index similar to that of the sample),
There are advantages such as rapid measurement because the measurement can be performed in the state of sand sludge, lower processing costs, and easier measurement work.

In addition, compared to the movable telescope type, the fixed telescope type (differential type) described above has the advantage that if the refractive index of the block and sample is significantly different, the slit image will be out of the field of view of the eyepiece. Although it is a hassle to have to replace the declination each time, the declination angle is kept within a small range and the error in declination measurement is kept small.

(Problems to be Solved by the Invention) A conventional differential refractometer is configured as shown in FIG.
The declination angle was measured by visually measuring the scale provided in the eyepiece of the telescope 37 using a micrometer. For this reason, there are various problems as described below in the operation of adjusting the scale to the center of the slit image.

(1) Personal habits tend to emerge.

(2) The position of the slit image changes depending on the position of the observer's head (the angle at which the eyes look into the eyepiece).

(3) It is easy to misread the micrometer.

(4) People with severe astigmatism and presbyopia are particularly susceptible to eye strain.

(5) When the slit image becomes blurred due to the condition of the sample, it is difficult to locate the center of the image.

(6) After measuring the declination angle, mistakes and errors may occur during transcription, computer input, etc. during the refractive index calculation process.

(7) When measuring the declination angle, before measuring the sample: However, it is necessary to measure the angle of deviation slightly (depending on the assembled state of the block) in advance.

The present invention is intended to solve these problems, and the first purpose of the present invention is to simplify the measurement work by automating the refractive index measurement of transparent objects, and to eliminate individual errors. The second purpose is to improve measurement accuracy and reliability.

(Means for Solving the Problems) The above object of the present invention is to place a sensor instead of placing an eyepiece at the focal position of a telescope in the conventional differential refractometer shown in FIG. This was achieved by inserting a shutter immediately after the block, making the standard piece unnecessary.

Therefore, the present invention provides a differential optical refractive index measuring device comprising a slit, a transparent block, and an imaging lens.
a first optical path that passes through only the block (1), a second optical path that passes through the V block and the sample, and a shutter means that selectively switches between the first optical path and the second optical path;
a sensor for detecting the respective positions of the images of the slit formed through each of the first optical path and the second optical path; and means for controlling the drive of the shutter means and processing the output signal from the sensor. It is characterized by comprising the following.

The above sensor is a charge-coupled device sensor (COD
The COD sensor is preferably placed in a plane perpendicular to the optical axis. Further, the COD sensor may be one-dimensional (line sensor) or two-dimensional (area sensor). The output signal from the COD sensor is amplified by an amplifier and analyzed by a processing unit (CPU).

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an optical layout diagram showing a first embodiment of the present invention, in which a light source 1, a condenser lens 2, a slit 3, a collimator lens 4, a block 5, a sample 6, a shutter 7,
It is composed of an imaging lens 8, a COD sensor 9, and a control unit 10. The light source 1 is a discharge tube that emits a single wavelength, such as a helium discharge tube that emits light at a wavelength of 587.6 nm, a hydrogen discharge tube that emits light at 486.1 nm, or 656.3 nm. Instead of a discharge tube, H
An e-Ne laser or the like may also be used. The condenser lens 2 is used to form a light source image onto the slit 3, and a lens with a large aperture ratio is desirable because it brightens the image. The light emitted from the slit 3 is made into parallel light by the collimator lens 4, passes through the block 5 and the sample 6 (the optical path is slightly bent), passes through the shutter 7, is focused by the imaging lens 8, and is focused on the focal plane. An image is formed on the COD sensor 9 placed there.

FIG. 2 is a diagram showing the transparent block 5, sample 6, and shutter 7 in detail. ■Block 5 is a transparent body with a known refractive index, with apex angles of 90' and -45°, respectively.
The size is 40# square and the thickness is 15-25#*, and the surface through which the light beam enters and exits is polished. Sample 6 is a transparent body with an unknown refractive index whose apex angle is 9
It is processed to 0°. Shutter 7 emits light beams A and B
The light shielding plate 7a is driven by the light shielding plate 7a.

That is, the shutter 7 is provided with apertures independently from each other through which the light beams A and B can pass, and these apertures are closed by selectively moving the light shielding plate 7a under the control of the control unit. Selectively shaded. Here, the luminous flux A has passed through the V block 5 and the sample 6,
At the interface between them, the light beam is bent according to the difference in refractive index between the two. On the other hand, the light beam B passes only through the block 5 and does not pass through the sample 6, so it travels straight. Therefore, by detecting the positions of the slit image of the light beam formed on the COD sensor 9 and the slit image of the light beam °B, and electrically measuring the distance △X between the two positions as described in detail later, the measured value is The refractive index can be determined from a predetermined calculation formula. Shutter driving, position detection, analysis, and display are all performed by the central processing unit (CPU) and peripheral circuits within the control unit 9. In other words, by providing the shutter 7, it is no longer necessary to use a standard piece, and the operator has to perform the same operation twice, as in the past, by first placing the standard piece and determining the imaging position, and then performing the same operation on the sample. There is no longer a need to perform this process, and the measurement can be performed in a single operation, making automation possible.

The COD sensor 9 used in this embodiment has, for example, 3648 pixels each having a size of 8 μm x 8 μm arranged in a straight line. When the slit image is projected here, COD
The output signal from the sensor 9 is as shown in FIG.

Here, only the signal with 90% or more of the peak level is extracted, and the position of half the width is placed at the center of the image, respectively.
) and B, the position detection accuracy will be as high as 8 μm or less.

In the graph of FIG. 3, the two peaks are the pixels 9A, 9B of the CCD sensor 9 due to the luminous flux A and the luminous flux B, respectively.
- This shows a 9n output signal distribution, and the distance ΔX between both peaks (X, That is,
If the refractive index of the sample 6 is exactly equal to that of the V block 5, both peaks in FIG. 3 will coincide and show a single peak distribution.

Now, the calculation formula for determining the refractive index is as shown in the following formula (1) in the case of a differential refractometer.

Here, n: refractive index of sample 6 no: ■ refractive index of block 5 f: focal pressure of imaging lens 8 11t (m)ΔX:X
: Luminous flux Distance B between the imaging position X and X of the luminous flux B (in Fig. 2) (M) In the case of this example, △"""×8-xA"1000"" Therefore, the resolution in refractive index measurement In, 1X10'
If you want to achieve this, the focal length of the imaging lens should be set to 4
00m or more. In this example, this is set to 1000m, so the theoretical resolution is 4X1
It becomes 0'.

In this example, the operator first inputs the refractive index of the V block into the measuring device, and then places a sample with an unknown refractive index on the V block (at this time, ) and press the start switch (not shown) provided on the control unit. Then, the present arrangement immediately changes the imaging position of the slit image of the light beam A and the light beam Sn (xA).

x8) are sequentially measured and analyzed, and the resulting refractive index is displayed. Switching of the shutters for the light beam A and the light beam B is automatically performed immediately after the measurement on one side is completed. The time required for one measurement is approximately 5 seconds from pressing the start switch to displaying the resulting refractive index.

FIG. 4 shows a refractive index measurement value of 18 degrees measured with the refractive index measuring device of this example, and FIG. 5 shows the reproducibility of data with the refractive index measuring device of this example.

In Figure 4, individual data are the refractive index measurement values measured with the measuring device of this example and the precision spectrometer (Shimadzu G
The difference from the value measured with M-1 or GMR-1) is ×10
The frequency distribution is on the order of -5. The accuracy of refractive index measurement can be said to be approximately ±1 to 2×10 −5 . Fifth
In the figure, individual data is the difference between the average value and individual data when the same sample is measured 5 to 6 times.
The frequency distribution is on the order of 10'. The result was ±1X10'. Since the refractive index measurement using a precision spectrometer is ±1 to 2×10′, it is considered that the refractive index measurement device of this example is superior to a precision spectrometer in terms of reproducibility.

The V block used in this example was of glass type LF2 (nd=1.
59041), and the contact 'lis is a mixture of α-promonaphthalene and liquid paraffin LJIS 100 (viscosity calibration solution) with nd=1.59054. Sample 6
is glass type SK5 (nd~1.58800~1.5900
0).

FIG. 6 is a schematic optical layout diagram showing a second embodiment of the present invention. The refractive index measuring device of the second embodiment includes a light source 11, a condenser lens 12, a slit 13, a collimator lens 14, a block and sample 15, a shutter 17, an imaging lens 18, and a CCDt? sensor 19, control unit 20, R8232C interface 21, eyepiece 22, and mirrors 23-28.

As is clear from FIG. 6, this second embodiment is characterized by using a plurality of mirrors 23, 24, 25, 26 to bend the optical path, and the refractive index measurement operation is similar to that of the first embodiment. The same is true.

The refractive index measuring device of the second embodiment has the following features: (1) The size of the entire system is made compact by bending the optical path; (2) The optical path is divided by the driving mirror 28, and the measurement can be performed visually as before; and (2) The addition of an R8232C interface 21 enables communication with external equipment. This mirror 28 is a half mirror.
It is also possible to fix it by replacing it with . However, it is inevitable that the light intensity will decrease slightly.

In the second embodiment, rBloEJ, which is a Burroughs online terminal/offline personal computer, was connected to the external device. Then, the refractive indexes of a large number of blocks (1) are registered on the 810E side, and only the declination angle measurement is performed on the measurement shore side. That is, the refractive index calculation using equation (1) is processed and displayed at 810E.

This makes it possible to create more 1-block refractive index files, and also facilitates maintenance when replacing V-blocks.

(Effects of the Invention) As described above, according to the refractive index measuring device of the present invention,
Since the measurement work is automated, all human errors related to the measurement work can be eliminated, highly accurate data can be obtained, and the work time can be significantly reduced compared to that of conventional differential refractometers. . Furthermore, since the operator is freed from the act of looking through a conventional eyepiece, it is possible to significantly reduce the labor of the operator. Furthermore, in conventional differential refractometers, there was a risk that the standard piece would be lost or damaged, but according to the present invention, such a risk can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an optical layout diagram showing an embodiment of the present invention, FIG. 2 is an enlarged layout diagram showing the V block and shutter portion in the embodiment of FIG. 1, and FIG. 3 is an optical layout diagram of the embodiment of FIG. C
4 and 5 are graphs for explaining the accuracy of refractive index measurement values; FIG. 6 is an optical layout diagram showing another embodiment of the present invention; and FIG. 7 is a characteristic diagram showing the output of the CD sensor. The figure is an optical layout diagram showing a conventional differential refractive index measuring device. 1.11...Light source, 2.12...Condenser lens, 3.13...Slit, 4.14...Collimator lens, 5...V block, 15...■ block and sample, 6... Sample, 7.17... Shutter, 8
．． 18... Imaging lens, 9, 19... CCD sensor +, 10.20... Control unit, 21...
・Interface, 22...Eyepiece, 23-28
···mirror.

Claims (5)

[Claims] (1) In a differential optical refractive index measuring device comprising a slit, a transparent V block, and an imaging lens, a first optical path that passes through only the V block, and a second optical path that passes through the V block and the sample; the first optical path and the second optical path;
a shutter means for selectively switching the optical path; and a shutter means for selectively switching the optical path;
A sensor for detecting the respective positions of the images of the slit formed through each of the optical path and the second optical path, and means for controlling driving of the shutter means and processing an output signal from the sensor. A differential automatic measuring device for optical refractive index, characterized in that: (2) The shutter means is driven by the control means to selectively block light from two apertures for allowing each of the light rays in the first optical path and the light rays in the second optical path to pass through the apertures. The differential automatic measuring device for optical refractive index according to claim 1, which comprises a light shielding plate. (3) The differential automatic measuring device for optical refractive index according to claim 1 or 2, wherein the sensor is a charge-coupled device sensor formed by linearly arranging a large number of micropixels. . (4) The differential automatic measuring device for optical refractive index according to claim 1 or 2, wherein the sensor is a charge-coupled device sensor formed by two-dimensionally arranging a large number of micropixels. (5) The differential automatic measuring device for optical refractive index according to claim 1, wherein the optical path from the slit to the sensor is bent by a plurality of mirrors.