JPH0263168B2 - - 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. This detection signal is used for a feedback signal and display in a control system for the rotational angular position and rotational 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 poles in two orthogonal directions of the stator, 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. Furthermore, in order to obtain a predetermined magnetic flux distribution during manufacture, 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 reaches each light receiving part via each of the first to fourth stationary polarizing plates. The amount of light that arrives varies 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 an 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, corresponding outputs are 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, light sources in particular are prone to characteristic changes due to aging, etc., and in such a case, the amplitude of the output of the light receiving section will also change, resulting in a problem in which the signals formed using the amplitude information will be inconsistent. There is.

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 and disposed opposite the non-overlapping portion of the first plate body; and a second plate body arranged to face the non-overlapping portion of the first plate body and the second plate A first light source and a first light receiving section, which are arranged to face each other across first and second polarizing plates of the body, and a second light receiving section.
a third light source and a third light receiving section, which are arranged to face each other across the overlapped portion of the first plate; and the first, second, and third light receiving sections. a lighting control section that sends a constant DC lighting signal to the light source of No. 3 and controls the amount of light emitted from the light source based on input from a light amount correction section described later; and outputs of the first, second, and third light receiving/receiving sections.
Input e ₁ , e ₂ , e ₃ and calculate e ₀ = (e ₁ − e ₃ ) sinωt + (e ₂ −
e ₃ ) an arithmetic unit equipped with a modulation circuit and an adding/subtracting circuit for calculating cosωt [here, e ₀ : output, ω : angular frequency of a sinusoidal periodic signal for modulation], and the third light receiving unit output and the setting signal of the setting device are input to a deviation calculator to form a deviation signal of both inputs, and the light amount correction section is configured to send the deviation signal to the lighting control section as an increase/decrease signal of a constant DC lighting signal. This is a photoelectric displacement detector.

The first, second, and third light sources may be different light sources, or two or all of them may be the same light source. Furthermore, the order of calculations in the calculation section is the same regardless of whether the input difference is first calculated and then modulated and added, or whether each input is first modulated and then added or subtracted.

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 of the overlapping part of the first plate α ₃
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 and the first and second polarizing plates of the second plate are The amount of light from the light sources placed on one side of the sandwich is multiplied by their respective transmittances α ₁ and α ₂ and reaches the first and second light receiving parts placed on the other side. The amount of light from the light source placed on one side is multiplied by a certain transmittance α _{by 3} and reaches the light receiving section placed on the other side.

As a result, if the amount of light emitted is now set as C, and the conversion coefficient between the light amount of the light receiving section and the electric signal is set as β, then the first to third light receiving sections have the following outputs e ₁ to e ₃ occur respectively.

e ₁ = α ₁ Cβ = K ₃ cos2θ + K ₄ e ₂ = α ₂ Cβ = −K ₃ sin2θ + K ₄ ... e ₃ = α ₃ Cβ = K _4Here , K ₃ = K ₁ Cβ K ₄ = K ₂ Cβ Below , these outputs e ₁ to _{e 3} are introduced into the calculation section,
First, in the adder/subtractor circuit, the calculations (e ₁ -e ₃ ) and (e ₂ -e ₃ ) are performed, and the constant term K ₄ in e ₁ and e ₂ is removed. These differences are then sent to a modulation circuit, which generates sinusoidal periodic signals that are 90 degrees out of phase with each other.
After being modulated by sinω and cosωt, the respective modulation signals are added in the adder/subtractor circuit, and the output e with a positional shift corresponding to the relative rotational displacement θ of the first and second plates is as follows. ₀ is formed.

e ₀ = (e ₁ − e ₃ ) sin ωt + (e ₂ − e ₃ ) cos ωt = K ₃ sin (ω t − 2θ) ... In addition, the calculation in the calculation section first calculates e ₁ , e ₂ , e ₃
After modulating, addition and subtraction are performed in exactly the same way.

Next, when the light amount C of the light source changes, the amplitude of the light receiving section outputs e ₁ to _{e 3} will change, but if the rate of change is the same, the phase of the above output e ₀ will change depending on the rotational displacement θ 2θ, which corresponds to , and there is no problem in calculating the displacement. However, at this time, the amplitude of the output e ₀ will change as a result of the change in the amplitude of e ₁ to _{e 3} , and a problem will occur if the output whose amplitude has changed is connected to and inputted to another device. For example, the output
When e ₀ is applied as a feedback signal to the drive circuit of an AC servo motor, if the amplitude of e ₀ changes, this will directly cause a change in the rotational speed of the motor. Therefore, in most cases other than simple applications such as simply determining rotational displacement θ, it is necessary to keep the amplitude of this output e ₀ constant.

The light intensity correction section performs this operation.
The third light-receiving section output _e3 is input here, and first, the deviation between it and the setting signal of the setting device is determined by a deviation calculator. Therefore, the occurrence of this deviation means a change in the light source, and the magnitude of the deviation indicates the extent of the change. Therefore, this deviation signal is then sent to the lighting control section as a control signal for increasing or decreasing the constant DC lighting signal, thereby changing the amount of light emitted by the first, second, and third light sources. As a result, the third light receiving section output e ₃
The amount of light is compensated so that the amount of light emitted by the first, second, and third light sources represented by this is always constant. Note that if the degree of light intensity change differs depending on the light source, there is a problem in using only the output _e3 of the third light receiving section as a feedback signal, but in most cases, the light source It can be considered that almost the same characteristic changes occur, and there is no problem in practical use.

EXAMPLE Hereinafter, as an example, a first plate body is formed by overlapping two large and small polarizing discs, and a second plate body is formed by arranging two polarizing plates in parallel. The present invention will be explained in detail.

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, a large-diameter polarizing disk 11 and a small-diameter polarizing disk 12 are arranged concentrically and superimposed 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.

Further, a third light source 23 and a third light receiving section 33 are arranged facing each other across the overlapping portion of the large diameter and small diameter polarizing discs 11 and 12 located on the inner peripheral side of the first plate body 10. has been done.

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 a lighting control unit that controls the amount of light emitted from the first to third light sources, and a rotation of the first plate 10 by calculating the outputs of the first to third light receiving units. This is an example of a calculation unit that calculates displacement, and the first to third light sources 21 to 23 and light receiving units 31 to 33, which are given the same numbers as in Figures 1 and 2, are the same as in Figures 1 and 2. be.

In this case, the output terminal of the lighting control section 50 consisting of a constant current generator is connected to the first to third light sources 21 to 23.
are connected in series with the first to third light sources 21 at all times.
A constant amount of light is emitted from ~23.

Further, the light amount correction section 70 includes a deviation calculator 71 between the output of the third light receiving section 33 and a setting electric signal corresponding to the target light emission amount outputted from the setting device 72, and the deviation signal is sent to the lighting control section 50. sent to
The lighting control unit 50 changes the magnitude of the lighting signal sent to each of the light sources 21 to 23 in response to the deviation.

Further, the calculation section 60 operates on the first and second light receiving sections 3
1, 32 outputs e ₁ , e ₂ and the output of the third light receiving section 33
The first and second adding/subtracting circuits 61, 62 calculate the difference from e ₃ , respectively, and the carrier sent from the carrier oscillator 66 to the output of the adding/subtracting circuits 61, 62.
first and second modulators 63 that multiply sinωt and cosωt;
64, and a third adding/subtracting circuit 65 that calculates the sum of the outputs of the respective modulators 63 and 64.

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 first, second and third light sources 21, 2
The constant amount of light emitted from 2 and 23 is multiplied by α ₁ , α ₂ , and α ₃ and sent to each corresponding light receiving unit 31 to 33.
The light receiving units 31 to 33 generate electric signals e ₁ to e ₃ shown in the above equations corresponding to the amount of light received.

Then, in the first and second adjusting circuits 61 and 62, the difference between the first and second light receiving section outputs e ₁ , e ₂ and the third light receiving section output e ₃ is calculated, and then the difference is calculated. is balanced modulated by a sine wave having a phase difference of 90 degrees in the first and second modulators 63 and 64, and then
The third adding/subtracting circuit 65 adds the sum to form the output e ₀ shown in the above equation.

When the amount of light emitted from the light source 23 changes, the output of the light receiving section 33 changes, and as a result, a deviation occurs in the deviation calculator 71, and the lighting signal sent from the lighting control section 50 is changed. , light source 21~
Control is performed so that the amount of light emitted by the light source 23 becomes a predetermined amount.

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.

Furthermore, the order in which the calculation unit 60 performs calculations on the outputs of the light receiving units is not limited to the above embodiment, and the order in which the calculation unit 60 performs the calculations on the outputs of the light receiving units is not limited to the above embodiment, and may be performed by calculating e ₁ and e ₂ by 90
modulated by a periodic signal with a phase difference of 90 degrees and then added, and e ₃ is modulated by a signal (sinωt + cosωt) of the sum of periodic signals with a phase difference of 90 degrees,
The same effect can be obtained by subtracting the modulation signal from the sum signal (e ₁ sinωt+e ₂ cosωt).

Moreover, although the above-mentioned embodiment illustrated the case where the first to third different light sources were made to face each light receiving part, the same effect can be obtained even if a single shared light source is made to face each light receiving part.

Moreover, although the above-mentioned embodiment illustrated the case where the first to third different light sources were made to face each light receiving section, the same effect can be obtained even if a single light source is made to face each light receiving section.

Further, in the above embodiment, the first plate 10 is fixed to the shaft 1 and rotated, but the first and second polarizing plates of the second plate 40 are shaped like donuts. The same effect can be achieved by providing the discs on different radii and fixing them to a shaft for rotational displacement.

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 amount of light emitted by the light source changes, the amount of light emitted is automatically corrected by the light amount correction section that uses the output of the light receiving section as a feedback signal, so the amplitude of the output that has a phase corresponding to the rotational displacement also changes. It is always kept constant, reducing restrictions when connecting its 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 that are arranged to face each other with a second polarizing plate in between, and an overlapping portion of the second light source, the second light-receiving section, and the first plate body. A third light source and a third light source are arranged facing each other across the
a light receiving section, a lighting control section that sends a constant DC lighting signal to the first, second, and third light sources and controls the amount of light emitted from the light sources based on input from a light amount correction section described later; 1, second and third light receiving unit outputs e ₁ ,
Input e ₂ and e ₃ and get e ₆ = (e ₁ − e ₃ ) sinωt + (e ₂ − e ₃ )
an arithmetic unit including a modulation circuit and an adjustment circuit for calculating cosωt [here, e ₀ : output, ω : angular frequency of a sinusoidal periodic signal for modulation]; and the output of the third light receiving unit and a setting device. and a light amount correction section that inputs the setting signal of the input signal and the setting signal into a deviation calculator to form a deviation signal of both inputs, and sends the deviation signal to the lighting control section as an increase/decrease signal of a constant DC lighting signal. Detector. 2. Claim 1 in which two or all of the first, second, and third light sources are light sources with the same effect.
The photoelectric displacement detector described in . 3 The calculation section includes a modulation circuit that modulates the outputs of the first and third light receiving sections and the outputs of the second and third light receiving sections using sinusoidal periodic signals sinωt and cosωt that have a phase difference of 90 degrees between them. , the difference between the modulation signals of the outputs of the first and third light receiving sections and the sum of the difference between the modulation signals of the outputs of the second and third light receiving sections. The photoelectric displacement detector according to any one of Item 2. 4 The arithmetic unit includes an adding/subtracting circuit that calculates the difference between the outputs of the first and third light receiving sections and the difference between the outputs of the second and third light receiving sections, and a sine converter that calculates each difference between the outputs of the first and third light receiving sections. 3. The photoelectric displacement detector according to claim 1, comprising a modulation circuit that modulates each waveform periodic signal sinωt and cosωt, and an adder/subtractor circuit that calculates the sum of the modulation signals.