JPH0263170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a detector for rotational displacement of a shaft. The rotation angle is detected, and this detection signal is used as a feedback signal or display in a control system for the rotation angle position and rotation speed of the object to be detected.

Prior Art This type of detector includes a rotary encoder, a resolver, and the like. Among them, resolvers have a relatively simple structure despite having high resolution, and have the characteristic that angular information can be extracted for each period of the carrier wave.

That is, the resolver has first and second coils wound around the poles of the stator in two orthogonal directions, respectively.
A third coil is wound around the rotor rotating inside the rotor, and the first and second coils are supplied with carrier waves Va, Vb, which have a phase difference of 90 degrees, Va=V ₂ sinωt Vb=V ₂ cosωt The magnetic flux corresponding to the carrier waves Va and Vb is radiated from each pole. Here,
V ₂ represents the amplitude of the carrier wave, and ω represents the angular frequency. Therefore, when this rotor is connected to the shaft to be measured and rotated, the proportion of the magnetic flux interlinking with the rotor among the respective radiation magnetic velocities changes depending on the rotation angle θ, and as a result, the third A phase signal Vc Vc=K ₂ V ₂ cosωtsinθ +K ₂ V ₂ sinωtcosθ = K ₃ V ₂ sin(ωt+θ) is induced in the coil. Here, K ₂ and K ₃ represent proportionality coefficients. However, since resolvers use electromagnetic signal generation means as described above, they require coils and rotary transformers for extracting signals from the coils, which imposes restrictions on downsizing. The problem is that the moment of inertia is also larger than that of a rotary encoder. In addition, in order to obtain a predetermined magnetic flux distribution during manufacturing, strict precision is required in the shape and position of the coil, resulting in a problem of high cost.

This drawback of the resolver is due to the use of electromagnetic signal generation means, and a possible solution to this problem is to use photoelectric signal generation means.

Examples of this type include, for example, U.S. Patent No.
There is one disclosed in No. 3306159. In this system, four stationary polarizing plates, numbered 1 to 4, are arranged to face a portion of the polarizing plate fixed to the rotating shaft, and each stationary polarizing plate has its transmission axis shifted by 45 degrees from each other. Then, a light source and a light receiving section are arranged facing each other on the outside of each of the stationary polarizing plates and the rotating polarizing plate.

In the above, the light from the light source passes through the rotating polarizing plate, and then passes through each of the first to fourth stationary polarizing plates to reach each light receiving part, but at this time, each light receiving part The amount of light that reaches this value changes depending on the intersection angle of the transmission axes of the rotating polarizing plate and each of the first to fourth stationary polarizing plates. That is, the transmittance of light changes corresponding to a cosine function of the angle of intersection. Therefore, when the rotating polarizing plate is now rotated by the angle θ, the intersection angles between the rotating polarizing plate and the first to fourth stationary polarizing plates are θ, θ+45°, θ+90°, and θ+, respectively.
135°, and as a result, each transmittance is
Corresponding to cos2θ, -sin2θ, -cos2θ, and sin2θ, outputs corresponding to these are also generated in each light receiving section. However, the above transmittance is always greater than 0, so if the above transmittance is expressed strictly, the intersection angle is 90
In the case of 3 degrees, it is the sum of the orthogonal transmittance and the above-mentioned transmittance, and each light receiving section also includes a DC component corresponding to the orthogonal transmittance.

Next, the carrier wave sinωt,
cosωt, −sinωt, and −cosωt are multiplied and then added. Therefore, the DC component mentioned above is canceled by this addition, and the added output is sin(ωt+2θ) whose phase changes corresponding to the rotation angle θ of the rotating polarizing plate.
becomes.

Problem to be Solved by the Invention However, in this case, it is necessary to accurately arrange the first to fourth polarizing plates so that their transmission axes are shifted by 45 degrees. It is unavoidable that assembly and adjustment techniques require skill and a large amount of work time.

In addition, the light source in particular is prone to characteristic changes due to the aging rate, etc., and in such a case, the amplitude of the output of the light receiving section will also change, resulting in a problem when using the amplitude information. That is, even if the amplitude of the output of each light receiving section changes, if the rate of change is the same, the phase of the added output formed based on it is 2θ corresponding to a rotational displacement of 0, and there is no problem. However, at this time, the amplitude of the addition output changes as the amplitude of the output of each light receiving section changes. Therefore, a problem arises when this output with a changed amplitude is connected to and inputted to other equipment. For example, if the added output is applied as a feedback signal to the drive circuit of an AC servo motor, if the amplitude changes, this will directly cause the rotational speed of the motor to change. Therefore, in most cases other than simple applications such as simply determining rotational displacement θ, it is necessary to always keep the amplitude of this addition output constant.

The present invention aims to solve the problem of having to adjust the position of a large number of polarizing plates when arranging them.

At the same time, the present invention attempts to solve the problem of changes in the amount of light emitted due to changes in the characteristics of the light source.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention reduces the position adjustment of the transmission axis of the polarizing plate to two locations, and shifts the transmission axis by 45 degrees to produce polarized light from two large and small plates. A first plate body in which the plates are overlapped to form an overlapping part and a non-overlapping part, and a first plate body with the transmission axis shifted by 45 degrees from each other.
a second plate body to which a second polarizing plate is fixed, the second plate body disposed opposite the non-overlapping portion of the first plate body, the non-overlapping portion of the first plate body, and the second plate body; The first of
A first light source and a first light-receiving section, a second light source and a second light-receiving section, and an overlapping portion of the first plate are arranged to face each other with a second polarizing plate in between. A third light source and a third light receiving section, a fourth light source and a fourth light receiving section, and an AC lighting signal that changes sinusoidally to the first and third light sources, which are arranged to face each other. a lighting control unit that sends an AC lighting signal having a phase difference of 90 degrees from the AC lighting signal that changes sinusoidally to the second and fourth light sources, and the first, second, third, and The fourth light receiving unit output e ₁ ,
an arithmetic unit that inputs e ₂ , e ₃ , and e ₄ and calculates e ₀ = (e ₁ + e ₂ )−(e ₃ + e ₄ ); and one or both of the third and fourth light receiving units. Input the output and the setting signal of the setting device to a deviation calculator to form a deviation signal of both inputs,
The light amount correction section sends the deviation signal to the lighting control section as an amplitude increase/decrease signal of an AC lighting signal having a constant amplitude.

Incidentally, instead of arranging the first and second light receiving sections separately, a common light receiving section is provided facing the first and second light sources, and the third and fourth light receiving sections are similarly arranged. Instead of arranging each light source separately, a common light receiving section is provided facing the third and fourth light sources, and the arithmetic section is connected to the first light source.
By inputting the outputs (e ₁ + e ₂ ) and (e ₃ + e ₄ ) of the common light receiving section of the second light source, the common light receiving section of the third and fourth light sources, and e ₀ = (e ₁ + e ₂ ). The same effect can be obtained by performing the calculation of -(e ₃ +e ₄ ) and inputting (e ₃ +e ₄ ) to the light amount correction section. Also, one of the first and second light receiving sections or the third and fourth light receiving sections is used as a shared light receiving section, and the other is set as a separate light receiving section, and the light receiving section outputs e ₁ , e ₂ and (e ₃ +e ₄ ), or the output of the light receiving section (e ₁ +
e ₂ ), e ₃ , and e ₄ to the calculation section and e ₈ = (e ₁ + e ₂ ) −
(e ₃ + e ₄ ), and (e ₃ + e 4 )
e ₄ ), or e ₃ and e ₄ as inputs to the light amount correction section.

Effect When the first and second plates generate a relative rotational displacement θ, the polarizing plate of the non-polymerized portion of the first plate and the first and second polarizing plates of the second plate The intersection angle with each transmission axis is shifted by θ, and as a result, the transmittances α ₁ and α ₂ of each light change as follows.

α ₁ = (H ₀ − H ₉₀ ) cos ² θ + H ₉₀ = K ₁ cos2θ + K ₂ ... α ₂ = (H ₀ − H ₉₀ ) cos ² (θ + 45°) + H ₉₀ = K ₁ cos2 (θ + 45°) + K ₂ = −K ₁ sin2θ＋K ₂ ... Here, H ₀ : Parallel transmittance H ₉₀ : Orthogonal transmittance K ₁ = (1/2) (H ₀ −H ₉₀ ) K ₂ = (1/2) (H ₀ −H ₉₀ ) At this time, the transmittance α ₃ of the overlapping part of the first plate
is constant regardless of the rotational displacement θ of the second plate, and is as follows.

α ₃ = (H ₀ − H ₉₀ ) cos ² 45° + H ₉₀ = K ₂ ... Therefore, the non-polymerized portion of the first plate is connected to the first and second polarizing plates of the second plate. The amount of light from the light sources placed on one side is determined by their respective transmittances α ₁ and α ₂
It is multiplied and reaches the light receiving part placed on the other side, and
The amount of light from the light source placed on one side of the overlapping portion is multiplied by a certain transmittance α _{by 3} and reaches the light receiving section placed on the other side.

Now, the first and third light sources and the second and fourth light sources each have periodic signals whose phases are shifted by 90 degrees from each other.
For example, a lighting signal consisting of a sine wave, B(Asinωt+
1), the amount of light emission is controlled by B (Acosωt+1),
They emit the following amounts of light C ₁ , C ₃ , C ₂ , and C ₄ , respectively.

C ₁ = C ₃ = E (Dsinωt+1) C ₂ = _{C 4} = E (Dcosωt+1) ... Here, A _{, B} , D, and E are proportional coefficients _. 1. When passing through the second plate, the above-mentioned transmittance α ₁ , α ₂ , α ₃ , α ₃ respectively
is multiplied and reaches each corresponding first to fourth light receiving section,
There, it is converted into electrical signals e ₁ to _{e 4} corresponding to the amount of received light. That is, e ₁ =K ₃ sinωtcos2θ+K ₄ cos2θ +K ₅ sinωt+K ₆ e ₂ =−K ₃ cosωtsin2θ−K ₄ sin2θ +K ₅ cosωt+K ₆ e ₃ =K ₅ sinωt+K ₆ e ₄ =K ₅ cosωt+K ₆ ……Here, the light amount and Letting β be the conversion coefficient of the electrical signal, K ₃ = DEK ₁ β K ₄ = EK ₁ β K ₅ = DEK ₁ β K ₆ = EK ₂ β And the outputs of these light receiving parts are processed in the calculation part as follows. is calculated, and an output e ₀ having a positional shift corresponding to the relative rotational displacement θ of the first and second plates is generated.

e ₀ = e ₁ + e ₂ − (e ₃ + e ₄ ) = K ₃ (sinωtcos2θ−cosωtsin2θ) +K ₄ (cos2θ)−sin2θ = K ₃ sin(ωt−2θ) +K ₅ (cos2θ−sin2θ ... At this point, the light is turned on. The frequency of the light source is set sufficiently high compared to the rotational displacement speed, and by passing the output e ₀ through a high-pass filter, it becomes a phase signal with the second term in the equation removed.

In addition, although the light-receiving parts were made to face each of the first to fourth light sources in the above, the light amounts C ₁ and C ₂ and C ₃ C ₄ of the first and second light sources, and the third and fourth light sources were respectively When the light is received by a common light receiving section, the addition of outputs e ₁ +e ₂ and e ₃ +e ₄ , which is part of the calculation, can be performed by the light receiving section.

Next, if the light intensity C ₁ to _{C 4} of each light source changes,
The amplitudes of the outputs e ₁ to _{e 4} of the light recording/receiving section change. The output of the third light receiving section is sent to a light amount correction section, where it is compared with a set value corresponding to a predetermined light amount. Then, the deviation signal is sent to the lighting control section, and the amplitude of the lighting signal is changed according to the deviation. As a result, the amount of light emitted from each light source is changed, and as a result, the amount of light emitted from each light source is controlled to be constant at all times.

Examples Below, as examples, the first plate body is formed by overlapping two large and small polarizing discs, the second plate body is formed by two polarizing plates arranged in parallel, and four light sources are formed. The present invention will be explained in detail by taking as an example a device using four light receiving sections.

In FIGS. 1 and 2 showing the constituent parts of the embodiment,
Reference numeral 1 denotes a rotatably supported shaft, and on the shaft 1 there is provided a large-diameter polarizing disc 11 and a small-diameter polarizing disc 12, which are superimposed concentrically with their transmission axes shifted by 45 degrees. One plate body 10 is integrally fixed.

A second plate is located opposite to a non-overlapping portion consisting only of the large-diameter polarizing disc 11 located on the outer circumferential side of the first plate.
A plate body 40 is disposed, and the second plate body 40 includes first and second polarizing plates 4 whose transmission axes are shifted by 45 degrees from each other.
1 and 42 are fixed. And the first one,
The first and second light sources 2 are placed facing each other with the second polarizing plates 41 and 42 and the non-overlapping portion of the first plate body 10 in between.
1, 22 and first and second light receiving sections 31, 32 (however, 32 is not shown). is installed.

In addition, third and fourth light sources 23 and 24 and a third,
Fourth light receiving sections 33 and 34 are arranged.

Therefore, in this mechanism part, when the large and small diameter polarizing disks 11 and 12 are superposed, the transmission axis is assembled and adjusted to 45 degrees, and the first and second plates in the second plate are assembled and adjusted.
There are only two adjustment operations: shifting the transmission axes of the second polarizing plates 41 and 42 by 45 degrees and assembling and adjusting them.

Next, FIG. 3 shows the first to fourth light sources 21 to 2.
a lighting control section that controls the amount of light emitted by the first to fourth lights;
This is an embodiment of a calculation unit that calculates the rotational displacement of the first plate body 10 by calculating the outputs of the fourth light receiving units 31 to 34, and the light sources 21 to 2 with the same numbers as in FIGS.
4. The light receiving sections 31 to 34 are the same as those shown in FIGS. 1 and 2.

First, the lighting control section 50 controls the first and third light sources 2
1, 23, second and fourth light sources 22, 24, periodic lighting signals are made of sine wave signals having a phase difference of 90 degrees between them, B(Asinωt+1), B(Acosωt+
1) to emit light in amounts C ₁ to C ₄ shown in the above formula.

Next, the calculation section 60 includes first and second addition/subtraction circuits 61 and 62 that calculate the output difference between the first and third, second and fourth light receiving sections 31 and 33, and 32 and 34; A third adding/subtracting circuit 63 that calculates the sum of both adding/subtracting circuits.
It consists of.

In the above, when the shaft 1 is rotationally displaced by θ, the first plate 10 is also rotated integrally by θ,
The intersection angles of the transmission axes of the first and second polarizing plates 41 and 42 and the non-overlapping portion of the polarizing plate 11 are θ and (θ
+45°), and its transmittance α ₁ and α ₂ are as above,
It changes according to the rotational displacement θ as shown in the equation.

On the other hand, the transmittance of the overlapping portion of the first plate 10 is constant regardless of the rotational displacement θ of the shaft 1, and is expressed by the above equation.

Therefore, the amounts of light C ₁ to _{C 4} emitted from the first to fourth light sources 21 to 24 are multiplied by α ₁ to α ₃ , respectively, and sent to the corresponding first to fourth light receiving sections 31 to 34. The light receiving units 31 to 34 generate electrical signals e ₁ to e ₄ according to the above equations corresponding to the amount of light received.

Then, the outputs e ₁ to ₄ of each light receiving section are sent to the calculation section 60.
First, (e ₁ − e ₃ ) and (e ₂ − e ₄ ) are calculated, and then the sum (e ₁ − e ₃ ) + (e ₂ − e ₄ ) is calculated in the third adding/subtracting circuit. 63 to form the output e ₀ shown in the above equation.

During this time, if the amount of light emitted by the light sources 23 and 24 changes, the outputs of the light receiving sections 33 and 34 change, and as a result, a deviation occurs in the deviation calculators 71 and 72, which causes the output from the lighting control section 50 to change. The amplitude of the lighting signal changes, and the amount of light emitted from the light sources 21 to 24 is controlled to be a light amount that changes periodically with a predetermined amplitude. The above is a case where the light intensity correction is performed based on the outputs of both the light receiving sections 33 and 34, but since the changes in the light intensity of each light source of the same standard and produced in the same lot can be considered to be approximately the same, it is natural that the output of one light receiving section is corrected. The amount of light may be corrected based on.

In addition, in the above embodiment, the light source and the light receiving section are exemplified using a direct light emitting element and a light receiving element.
The same effect can be obtained by using these and optical fibers.

Further, the order of calculations performed by the calculation section 60 on the outputs of the light receiving sections is not limited to the above embodiment, and may be any order as long as it satisfies the above calculation formula.

Furthermore, in the above embodiment, each of the light receiving sections is arranged to face the first to fourth light sources, but the first and second light sources, the third and fourth light sources, and each common light receiving section are arranged to face each other. , (e ₁ +e ₂ ), and (e ₃ +e ₄ ) may be directly generated.

In this case, since the changes in the amount of light from each light source can be considered to be substantially the same, the changes in the amount of light from each light source correspond to changes in the output of the common light receiving section shared by the third and fourth light sources. Therefore, by correcting the light amount using the output (e ₃ +e ₄ ) of the shared light receiving section as input to the light amount correcting section, the light amount of each light source can be similarly corrected.

Further, in the above embodiment, the first plate body 10
In the example shown, the first and second polarizing plates of the second plate body 40 are shaped like donuts, and are provided on different radii of the disc, and are attached to the axis 1. The same thing can be done even if it is fixed to and rotated.

Effects of the Invention As described above, the present invention provides a first polarizing plate having a polymerized portion and a non-polymerized portion of two polarizing plates.
The two polarizing plates of the second plate are opposed to the non-overlapping portion of the first plate, and the changes in the amount of transmitted light between them and the amount of transmitted light at the overlapping portion of the first plate are converted into electrical signals. processing to form an output corresponding to the rotational displacement of the first and second plates, the transmission axes of the polarizing plates only need to be adjusted for the two pairs of polarizing plates.
Overall assembly and procurement is simplified and work efficiency is improved.

In addition, when the light emission amount of the light source changes, the light emission amount is automatically corrected by the light amount correction section that uses the light receiving section output as a feedback signal, so the output having a phase corresponding to the rotational displacement is The amplitude is also kept constant at all times, reducing restrictions when connecting the output to other equipment.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the mechanism section of the present invention, FIG. 2 is a left side view of FIG. 1, and FIG. 3 is a block diagram showing an embodiment of the lighting control section and calculation section of the present invention. It is. 10: first plate, 40: second plate, 20:
Light source, 30: Light receiving section, 60: Arithmetic section, 50: Lighting control section.

Claims (1)

[Claims] 1. A first polarizer in which two large and small polarizing plates are stacked with their transmission axes shifted by 45 degrees to form an overlapping portion and a non-overlapping portion.
a second plate body, to which first and second polarizing plates are fixed with their transmission axes shifted by 45 degrees from each other, and which is disposed facing the non-overlapping portion of the first plate body; , a non-polymerized portion of the first plate and a first portion of the second plate,
A first light source and a first light-receiving section, a second light source and a second light-receiving section, and an overlapping portion of the first plate are arranged to face each other with a second polarizing plate in between. A third light source and a third light receiving section, a fourth light source and a fourth light receiving section, and an AC lighting signal that changes sinusoidally to the first and third light sources, which are arranged to face each other. a lighting control unit that sends an AC lighting signal having a phase difference of 90 degrees from the AC lighting signal that changes sinusoidally to the second and fourth light sources, and the first, second, third, and Fourth light receiving unit output e ₁ , e ₂ ,
A calculation section that inputs e ₃ and e ₄ and calculates e ₀ = (e ₁ + e ₂ ) - (e ₃ + e ₄ ), and the output and settings of one or both of the third and fourth light receiving sections. a light amount correction unit that inputs the setting signal of the device into a deviation calculator to form a deviation signal of both inputs, and sends the deviation signal to the lighting control unit as an amplitude increase/decrease signal of an AC lighting signal with a constant amplitude. Photoelectric displacement detector. 2. The photoelectric displacement detector according to claim 1, wherein the first light receiving section and the second light receiving section are a shared light receiving section. 3 The third light receiving section and the fourth light receiving section are composed of a shared light receiving section, and the light amount correction section inputs the output of the shared light receiving section and the setting signal of the setting device to a deviation calculator and calculates the deviation between both inputs. A signal is formed, and a deviation signal thereof is sent to the lighting control unit as an amplitude increase/decrease signal of an AC lighting signal with a constant amplitude.
The photoelectric displacement detector according to any one of Items 1 and 2.