JPH07245554A - Binarization device - Google Patents

Abstract

PURPOSE:To obtain a binarization signal having a constant duty ratio at all times even when an amplitude of an analog signal is changed by binarizing the analog signal with a period based on a threshold level obtained based on the effective value. CONSTITUTION:The binarization device is provided with an effective value calculation device 2, a threshold level setting device 4 and a comparator 6. Then the effective value calculation device 2 receives an analog signal 1 outputted from a light receiving section of an encoder, calculates the effective value and generates an effective value signal 3. Furthermore, the threshold level setting device 4 receives the effective value signal 3 to generate a threshold level signal 5 to obtain a desired duty ratio. Furthermore, the comparator 6 receives the threshold level signal 5 and the analog signal 1 to compare the both and to generate a binarization signal 7. When the binarization device is provided to the encoder, even when an amplitude of an analog signal outputted from a lighting light receiving section is changed due to any cause, the duty ratio of the obtained binarized signal is always kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binarizing device for producing a binarized signal having a desired duty ratio from an analog signal having periodicity.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing the structure of a conventional binarization device. This binarization device inputs a threshold value memory 8 to which a fixed threshold value is input, a threshold value signal 5 and an analog signal 1 output from the threshold value memory 8 and outputs both signals. And a comparator 6 for comparing. The binarization process in this device will be described with reference to FIGS. 5 and 6, the vertical axis is the voltage value and the horizontal axis is the time. Here, it is assumed that the SIN wave having the maximum value A is an analog signal with 0 as a reference and the SIN wave is converted into a binarized signal having a duty ratio of 50%. In this case, the threshold memory 8 stores 1/2 of the SIN wave maximum value A (that is, A
/ 2) is stored as the threshold signal 5 (see FIG. 5). The comparator 6 compares the analog signal 1 composed of the SIN wave having the maximum value A with the threshold signal 5 having the threshold value A / 2, and the value of the analog signal 1 exceeds the value of the threshold signal 5. Output a signal. Thus, the binarized signal 7 having the duty ratio of 50% (a / 2a) as shown in FIG. 6 is obtained.

Such a binarizing device has been used, for example, provided in an optical encoder for measuring a position and an angle. In an optical encoder, illumination light is applied to an incremental pattern in which transmissive parts and light-shielding parts having the same area are alternately arranged, and when the transmitted light is received by a photoelectric conversion element, the pattern is moved when the pattern is moved. A periodic analog signal is output from the light receiving portion of the light. The binarizing device binarizes the analog periodic signal so as to have a preset duty ratio. Then, the encoder obtains the position and angle to be measured based on the rising and falling positions of the binarized signal.

[0004]

However, since the value of the threshold signal is fixed in the conventional device, there is a problem that the duty ratio of the binarized signal also changes when the amplitude of the analog signal changes. there were. The state is shown in FIG.
It shows in FIG. 7 and 8, the vertical axis is the voltage value and the horizontal axis is the time. As shown in FIG. 7, when the maximum value A of the analog signal 1 decreases to A ′, the threshold value 5 whose threshold value is set to A / 2 and the analog signal 1 are obtained. The duty ratio of the binarized signal 7 is represented by b / (b + c) as shown in FIG. At this time, since c and b are not equal (c> b), the duty ratio of the binarized signal 7 does not reach a desired value (50%).

For example, in the above-mentioned optical encoder, when the luminance of the light source for the illumination light or the sensitivity of the photoelectric conversion element of the light receiving portion changes, the amplitude of the output analog periodic signal also changes. Therefore, in the conventional binarization device, the rising and falling positions of the generated binarization signal, that is, the duty ratio, changes with a change in the amplitude of the analog signal, and based on this binarization signal. There has been a problem that the accuracy of the obtained position and angle is reduced.

The present invention has been made in view of such a problem, and provides a binarizing device capable of obtaining a binarized signal having a desired duty ratio even if the amplitude of an analog signal changes. The purpose is to

[0007]

To achieve the above object, according to the present invention, an effective value calculating means for calculating an effective value of a periodic analog signal, and a desired duty ratio based on the effective value are provided. A threshold value setting means for setting the threshold value and a comparing means for binarizing the analog signal by using the threshold value constitute a binarization device.

[0008]

[Function] Effective value (RMS value) of analog signal with periodicity
Is obtained by the square root of the value averaged over one cycle of the square of the function value representing this signal. That is, this function y
Is a periodic function of t, the following equation holds.

[0009]

[Equation 1]

Here, R is an effective value of the function y, a is a value at an arbitrary time, and T is a period of the function. This effective value R changes in proportion to the amplitude of the analog signal. Therefore, in the present invention, the threshold value is set on the basis of the effective value so that the threshold value follows the change in the amplitude of the analog signal. The effective value changes in proportion to the amplitude (maximum value) of the analog signal, but the proportional coefficient α is determined to be a constant value by the function of the analog signal regardless of the amplitude of the analog signal. Therefore, if the function of the analog signal is known, the coefficient α can be obtained. At this time, the relationship between the effective value R and the maximum value of the analog signal can be expressed by the following equation. R = α · A (A: maximum value of analog signal) ··· Expression On the other hand, the duty ratio of the binarized signal depends on the value of the threshold value S. For example, in order to create a binarized signal with a duty ratio of 50%, the threshold value S is equal to the maximum value A of the analog signal.
It should be 1/2 (A / 2). The threshold value setting means of the present invention calculates the threshold value S from the effective value R according to a desired duty ratio. When the threshold value S is set to A / 2 to set the duty ratio to 50%, when the coefficient β is set, the product of this β and the effective value R is the threshold value S (= A
It should be equal to / 2). That is, the following formula should be satisfied. β · R = S (= A / n) (n: a constant determined according to the duty ratio) ··· Equation Here, when β is obtained from the equation, β = A / (nR)
= A / (n × α · A) = 1 / (n · α). As described above, α is constant if the function of the analog signal is fixed. Moreover, since n is also obtained as a constant, the value of β is always constant (constant). Therefore, if n is 2, the duty ratio 50 is obtained by comparing the analog signal with the threshold value S (= A / 2) obtained by substituting the value (effective value R) of the input signal and the constant β into. % Binarized signal is obtained (see FIG. 3). As described above, the effective value R is proportional to the amplitude of the analog signal, and the proportional coefficient α is determined to be a constant value by the function of the analog signal regardless of the amplitude of the analog signal. Therefore,
A binarized signal having a constant duty ratio can be generated regardless of the amplitude of the analog signal. And
If the value of α is obtained and the effective value is calculated by the effective value calculating means and the threshold value is set by the threshold value setting means, a binarized signal having a desired duty ratio can be obtained. . Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic block diagram of a binarizing apparatus showing an embodiment of the present invention. The binarization device of this embodiment includes an effective value calculator 2, a threshold value setter 4, and a comparator 6. The effective value calculator 2 inputs the analog signal 1 output from the light receiving portion of the encoder, calculates the effective value thereof, and creates the effective value signal 3. The threshold value setter 4 inputs the effective value signal 3 and creates the threshold value signal 5 so that a desired duty ratio can be obtained. The comparator 6 inputs the threshold value signal 5 and the analog signal 1, compares them, and creates a binarized signal 7.

The process of converting an analog signal into a binarized signal having a duty ratio of 50% in this embodiment will be described below with reference to FIGS. 2 and 3, the vertical axis is the voltage value and the horizontal axis is the time. The analog signal 1 output from the light receiving portion of the encoder is an analog signal composed of a SIN wave having a maximum value A with 0 as a reference. The analog signal 1 is input to both the effective value calculator 2 and the comparator 6. The effective value calculator 2 calculates an effective value R of the input analog signal 1 and creates an effective value signal 3 having this value R. Since the analog signal 1 is a SIN wave having the maximum value A of the period 2π, it can be expressed as a function of θ that is a function y = A / 2 (SIN θ + 1). Therefore, in the above equation, a is 0, T
When the effective value R is calculated with 2π and t as θ, R = A × (3
/ 8) ^1/2 , and the effective value R is (3/8) ^1/2 (= 0.61) of the maximum value A.
2) times (see Fig. 2). At this time, the relationship between the effective value R and the maximum value of the analog signal can be expressed by the following equation. R = 0.612 A = α · A The value of α is constant regardless of the maximum value A as long as the analog signal 1 is a SIN wave, and if the function of the analog signal 1 changes, the value of α also changes accordingly. Change. The rms value calculator 2 uses the calculated rms value signal 3 as a threshold value setter 4
Output to. The threshold value setter 4 creates a threshold value from the value R of this effective signal 3 based on the input effective value signal 3. In order to obtain a binarized signal with a duty ratio of 50%, a signal (A / 2) whose threshold value is 1/2 of the maximum value A of the analog signal 1 may be created. That is, when the coefficient β is set, the effective value R (=
The product of 0.612 A) should be equal to the threshold value S (= A / 2). Therefore, β is β · R = A / 2, and β =
A / (2R) = A / (2 × 0.612A) = 1 / (2 × 0.6
12) = 0.817. As mentioned above, analog signal 1
As long as it is a SIN wave, α (0.612) is constant, so β is always constant. Therefore, the threshold value setting unit 4 may be set so as to calculate the threshold value S from the following equation based on the input signal value and β (0.817). S (= A / 2) = β · R = 0.817R The comparator 8 inputs both the analog signal 1 and the threshold value S output from the threshold value setting device 4, and compares the values of these two signals. Then, when the value of the analog signal 1 exceeds the value of the threshold value signal 5, a signal is output. Thus, the duty ratio
A binarized signal 7 of 50% (a / 2a) is obtained (see FIG. 3). In this embodiment, the effective value calculator 2 for calculating the effective value and the threshold value setting device 4 for creating the threshold value from the effective value are provided independently of each other.
It may be configured to be performed by one means. Further, although the duty ratio is set to be 50%, it is possible to set an arbitrary ratio by setting the threshold value setting device 4 as described above.

When such a binarizing device is provided in the above-mentioned encoder, even if the amplitude of the analog signal output from the light receiving portion of the illumination light changes for some reason, the duty of the obtained binarized signal is changed. The ratio is always constant. Therefore, a stable reference signal can be obtained, and the distance and the angle can be accurately measured.

[0014]

As described above, according to the present invention, a periodic analog signal is binarized by a threshold value obtained based on its effective value. Therefore, even if the amplitude of the analog signal changes, a binarized signal having a constant duty ratio can be created.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a binarization process of the embodiment.

FIG. 3 is a diagram showing a binarized signal obtained in the example.

FIG. 4 is a schematic configuration diagram showing a conventional binarization device.

FIG. 5 is an explanatory diagram for explaining a conventional binarization process.

FIG. 6 is a diagram showing a signal binarized at a duty ratio of 50% by a conventional device.

FIG. 7 is an explanatory diagram showing a state in which the amplitude of the analog signal has changed during binarization by the conventional method.

FIG. 8 is a diagram showing a binarized signal binarized in the state of FIG. 7 in the conventional method.

[Explanation of symbols]

 1 analog signal 2 rms value calculator 3 rms value signal 4 threshold value setter 5 threshold value signal 6 comparator 7 binarization signal 8 threshold value memory

Claims (1)

[Claims] 1. An effective value calculating means for calculating an effective value of an analog signal having periodicity, and a threshold value setting means for setting a threshold value according to a desired duty ratio based on the effective value. A binarizing device comprising: a comparing unit that binarizes the analog signal using the threshold value.