JPH0623921Y2 - Ring detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a ring detector for measuring the intensity distribution of diffracted light by Fraunhofer diffraction, and is used, for example, in a particle size distribution measuring device based on a laser light diffraction method. Regarding ring detector.

<Prior Art> When a circular aperture or particles are placed in a parallel light beam, the light is diffracted according to the diameter of the aperture or particles. FIG. 5 shows an explanatory view of the principle of particle size distribution measurement by a so-called laser light diffraction method in which the particle size distribution of particles in a dispersed flying state is measured by utilizing this Fraunhofer diffraction phenomenon.

The laser light from the laser light source 51 is collimated by the collimator lens 52.
The laser light is diffracted by irradiating the circular opening 53 (particles) with a parallel light flux. When the Fourier transform lens 54 is disposed behind the circular aperture 53, a concentric diffraction image depending on the size of the circular aperture 53 is formed on the focal plane of the lens. The size of the circular opening 53 can be obtained by disposing the photodetector 55 on this focal plane and measuring the radial light intensity distribution of the diffraction image.

In order to measure the light intensity distribution in the radial direction of a diffraction image as described above, conventionally, as shown in FIG. 6, light from a plurality of photodiodes or the like having semi-ring-shaped light receiving surfaces each having a different radius is used. A so-called ring detector is used, in which the sensors S ₁ , S ₂ ... S _n are concentrically arranged in a fan shape around a point O.

<Problems to be Solved by the Invention> By the way, when a ring detector as shown in FIG. 6 is used, optical axis adjustment becomes difficult for the following reasons.

The optical axis adjustment is performed by the point where the parallel light flux is condensed by the lens 54,
That is, the focus of the lens 54 and the center O of the ring detector
Is important, but this adjustment is usually performed while monitoring the output of each sensor S ₁ , S ₂ ... S _n of the ring detector. However, each sensor S _1, S ₂ ...... S _n of the ring detector is because it is symmetrical to the center line which bisects through the ring detector the point O as an axis, the current focal point any position on the detector It is not possible to accurately detect whether or not there is.

That is, as shown in FIG. 7, there sensor S _i
Since there is no difference in the output from the sensor S _i between the case where there is a spot at the point A on the light receiving surface and the case where there is a spot at the point B, which is symmetrical to the point A with respect to the center line, Cannot identify whether the spot is at point A or point B. Therefore, in this case, move the spot or ring detector to the left or right once,
It is necessary to judge whether the spot is at the point A or the point B from the change in the peak of the output of the sensors S ₁ , S ₂ ... S _n at that time.

Also, even if you move the spot or detector in either direction, it depends on the resolution of the device.
For example, as shown in FIG. 8, the positions of the spots are P ₁ to P _1.
In the range of _2, the output may not show a difference enough to make the above determination.

From the above, for example, a fine drive mechanism for adjusting the optical axis, such as an XY table, is provided on the detector side and the like, and the optical axis is adjusted based on the output signals of the respective sensors S ₁ , S ₂ ... S _n of the ring detector. Even if the automatic control is carried out, not only becomes a control system with many unnecessary operations, but also P ₁ ~
The system may vibrate near the spot position of P ₂ .

The present invention has been made in view of this point, and an object thereof is to provide a ring detector that can easily perform the above-described optical axis adjustment with a simple configuration.

<Means for Solving the Problems> A structure for achieving this object will be described with reference to FIGS. 1 to 3 corresponding to an embodiment. The present invention provides a semi-ring shape having different radii. A plurality of photosensors S ₁ , S ₂ , S ₃ ... S _n each having a light receiving surface are arranged so that each light receiving surface is concentrically fan-shaped around a point O on one plane. In the photodetector, a plurality of different photosensors (for example, S ₁ and S _{3 on the} left side) are provided outside the fan-shaped pattern F and on both sides of the line that passes through the point O and bisect the fan-shaped pattern F. , ..., S _2, S 4 to the _right, by with the light receiving surface of ...) is extended, and a shielding plate 12 of the removable covering a pattern E of a portion which is its extension, characterized Be attached.

<Operation> On the extended pattern E, the arrangement of the photosensors is asymmetrical with respect to the center line. Therefore, by bringing the spot position on the pattern E, each photosensor S ₁ , ~ S _n , the left and right positions of the spot with respect to the center line are known, and the spot can be immediately positioned on the center line.

In this state, the spot position is moved upward and, for example, when the amount of incident light on the center hole detector 3 placed behind the center hole H centering on the point O is maximized, the movement is stopped. , The spot position can be centered.

The incidence of light on the extension pattern E when measuring the light intensity distribution of the diffraction image can be prevented by mounting the shield plate 12.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of an embodiment of the present invention, and FIG. 2 is its II-II.
FIG.

A plurality of optical sensors S _{1 to} S _n including photodiodes and the like
However, each of the light receiving surfaces is arranged along the surface of the substrate 10.

The light receiving surface of each of the photosensors S _{1 to} S _n forms a fan-shaped (semi-circular) pattern F as a whole on the surface of the substrate 10 and a pattern E extended below the fan-shaped pattern F.

That is, the light-receiving surface of each of the optical sensors S _{1 to} S _n includes a semi-ring portion having a different radius, and a linear portion extending downward from one end of the semi-ring portion. The semi-ring portions are arranged concentrically around the point O on the surface of the substrate 10, and the fan-shaped pattern F is formed.
And the linear portion forms the extension pattern E. The details of the extension pattern E will be described later.

The substrate 10 has two pins 11 and 1 orthogonal to the surface thereof.
1 is planted, and a shield plate 12 is detachably attached to the pins 11, 11. The shield plate 12 is, for example, a black flat plate for preventing reflection, and can shield the extended pattern E from diffracted light when the pins 11 and 11 are mounted.

In addition, the substrate 10 is provided with a center hole H, which is a through hole centered at the point O, and the ring detector 1
In the case of assembling to a particle size distribution measuring device or the like, an opal glass 2 and a center hole detector 3 such as a photo sensor are provided behind the center hole H. The center hole detector 3 can detect the amount of light passing through the center hole H.

FIG. 3 is an enlarged view of the pattern of the light receiving surface of each of the photosensors S ₁ , S _2, ... Near the point O.

The extended pattern E is formed under the following conditions with respect to the center line that passes through the point O and divides the fan-shaped pattern F into two.

That is, in the fan-shaped pattern F, the light sensor whose light receiving surface is arranged on the innermost side is S ₁ , and S ₁ is arranged in order toward the outer side.
₂ , S ₃ , ..., The light-receiving surface of the odd-numbered photosensors S ₁ , S ₃ , S ₅ , ... Is extended on the left side of the center line, and the even-numbered photosensor S ₂ is extended on the right side. , S ₄ , S ₆ , ...
The light receiving surface of ... is extended. The arrangement density of the light receiving surface of each photosensor in the extension pattern E may be equal to or less than the density in the fan-shaped pattern F.

Next, the operation will be described together with the usage method.

Prior to adjusting the optical axis, the shield plate 12 is removed.

As shown in FIG. 4, when a line that passes through the point O and is orthogonal to the center line is m and each region partitioned by the line and m is respectively A to D, the spot exists in the region A or A. In that case, the outputs of the photosensors S _{1 to} S _n are continuously changed by moving the spot, which can be determined. When the spot is in the area C, only the outputs of the odd-numbered photosensors S ₁ and S ₃ are large, and when the spot is in the area D, the outputs of the even-numbered photosensors S ₂ , S ₄ ... However, it is possible to judge that fact.

Now, as the adjustment procedure, first move the spot position to the left and right, and if the spot exists in A or A, detect it by the above judgment and lower the spot position to the area of C or D. bring up. This allows
It is possible to immediately determine whether the spot is on the left side or the right side of the center line.

Next, the spot position is moved toward the center line based on the determination result. In the extension pattern E, the output of the innermost photosensor S ₁ or S ₂ becomes large and then becomes equal to S ₂ or S ₁ , or if either output becomes small, the spot is on the center line. It turns out that it has arrived.

The movement is stopped at that position, then the output of the center hole detector 3 is monitored, the spot position is gradually moved upward, and the output of the center hole detector 3 is stopped at the position where the output is maximum. As a result, the spot position is point O.
Will match.

If the shielding plate 12 is attached in this state, the diffracted light can be measured immediately.

The spot position may be moved by moving the spot itself or by moving the ring detector 1 side. Further, this movement may be performed manually or may be performed automatically. In any case, it is possible to perform centering without a mistake under a certain procedure.

The extension pattern E is not limited to extending the light-receiving surfaces of the odd / even-numbered photosensors to the left and right with the center line interposed therebetween as in the above-described embodiments, and it is of course possible that the left and right light beams differ according to predetermined conditions. The intended purpose is achieved by extending the light-receiving surface of the sensor and monitoring the output of each photosensor based on its conditions.

Depending on the spot diameter used and the inner diameter of the innermost optical sensor S _{1 in} the fan-shaped pattern F, the extension pattern E
Even when the light receiving surfaces of the two innermost left and right photosensors are extended to the center line side and the spot is located on the line, both of the light receiving surfaces of the two innermost left and right photosensors are inevitable. If the spot light is made incident on the spot, the positioning accuracy is improved by stopping the movement when the outputs of the two optical sensors become equal when the spot is positioned on the center line.

<Effects of the Invention> As described above, according to the present invention, the fan-shaped pattern F
Since the light receiving surfaces of the different photosensors are extended to the left and right with the center line sandwiched therebetween, and in this extension pattern E, the arrangement of the photosensors is asymmetric with respect to the center line, By bringing the spot to, it is possible to immediately determine whether the spot position is on the left or right side with respect to the center line. As a result, the positioning of the spot on the center line becomes extremely easy, and thereafter, the positioning on the point O becomes possible only by shifting the spot position upward. This means that both manual and automatic adjustments can be completed according to a certain set of steps, especially when making adjustments with automatic control. In addition, it is extremely useful because there is no risk of vibration of the system. Moreover, since it is sufficient to extend the light receiving surface of the photodiode or the like in a predetermined pattern and simply add a shield plate, the cost is not substantially increased as compared with the conventional one.

[Brief description of drawings]

1 is a front view of an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II, and FIG. 3 is an enlarged view of a light receiving surface of the optical sensors S ₁ , S ₂ ... The figure is an illustration of the operation. FIG. 5 is an explanatory view of the principle of particle size distribution measurement based on the laser light diffraction method, FIG. 6 is an explanatory view of a conventional ring detector, and FIGS. 7 and 8 are explanatory views of its action. 10 ... Substrate 11, 11 ... Pin 12 ... Shielding plate S ₁ , S ₂ ... _Sn ... Optical sensor H ... Center hole F ... Fan pattern E ... Extension pattern O ... Center of fan pattern Dot …… center line

Claims (1)

[Scope of utility model registration request] 1. A plurality of optical sensors each having a semi-ring-shaped light receiving surface having a different radius are arranged so that each light receiving surface is concentrically fan-shaped with a point on one plane as a center. In the photodetector, on the outside of the fan-shaped pattern, on both sides of a line that passes through the one point and bisects the fan-shaped pattern, the light-receiving surfaces of a plurality of different photosensors are respectively extended, A ring detector comprising a detachable shield plate for covering the pattern of the extended portion.