TWI734562B - Index grating of optical encoder - Google Patents

Abstract

According to the index grating of the optical encoder, the proportion of the light transmission area in the unit area is improved, the light blocking ratio caused by foreign matters such as dust can be reduced, and the influence degree of the optical encoder on the light intensity is reduced, so that the sensing precision of the optical encoder is improved.

Description

Indicating grating of optical encoder

The present invention is related to position sensing technology, in particular to an indicating grating of an optical encoder.

The encoder that uses sine wave signal to analyze the position uses a light sensor to receive different light intensity changes under the rotation of the encoder, and then analyzes to obtain the current position, and in order to generate an ideal sine wave, reduce the need for analysis In the conventional technology, the shape of the light receiving area, the shape of the light shield, or the shape of the grating can be changed to obtain the ideal light intensity change when the code wheel rotates.的结果。 The result.

Please refer to the conventional indicating grating structure shown in FIG. 1, which is provided on a grid plate (1) with a plurality of light-transmitting areas (2) arranged in sequence and almost in the shape of a figure of eight, so as to change the light source through the main grating. After being transmitted or reflected, and then passed through the indicating grating, the light intensity can be sensed by the optical sensing element to obtain a sine wave signal that is close to the ideal, thereby improving the accuracy of analysis to obtain an accurate position.

However, due to the increasing requirements of precision machinery for position resolution accuracy, and the conventional technology shown in Figure 1, the technical content of the transparent area (2) is still not perfect, resulting in the resolution accuracy it can provide , Accuracy and even the ability to avoid interference have their limitations, and it is difficult to fully meet the precision required by precision machinery.

Therefore, the main purpose of the present invention is to provide an optical encoder indicating grating, which can improve the light source utilization efficiency of the optical encoder, strengthen the signal strength, and reduce the degree of interference caused by foreign objects.

In order to achieve the above-mentioned object, the main technical feature of the indicator grating of the optical encoder provided by the present invention is to increase the ratio of the light-transmissible area of the grating in a unit area, thereby increasing the utilization efficiency of the light source and the signal intensity, and can reduce The proportion of light blocking caused by foreign matter such as dust, thereby reducing its influence on the light intensity, so as to improve the sensing accuracy of the optical encoder.

In order to increase the proportion of the light-transmittable area in a unit area, the present invention provides a technology that enables the indicating grating of an optical encoder to have multiple first light-transmitting areas and multiple second light-transmitting areas of the same shape, which are staggered with each other. Are arranged in sequence on a grid plate, and make the first light-transmitting regions close to a first side of the grid plate and away from a second side opposite to the first side, and at the same time make the first light-transmitting regions The two light-transmitting regions are close to the second side and far away from the first side, and the first light-transmitting regions and the second light-transmitting regions are formed between a first end and a second end in shape The length is the same as each other, and the width of the shape is gradually increased from the first end to the second end, and the second end of the first light-transmitting regions is between the first end and the Between the first side, the second ends of the second light-transmitting regions are between their first ends and the second side, and among them, the second ends of the first light-transmitting regions that are adjacent to each other The distance (D) from the second end of the second light-transmitting area, and the length (L) of the shape of the first light-transmitting area or the second light-transmitting area, and satisfies the formula: L≦D<2L . In this way, the area ratio of the light-transmitting areas provided by the first light-transmitting regions and the second light-transmitting regions can be increased in a unit area, so as to achieve the above-mentioned purpose and effect.

Wherein, the preferred ratio between the length (L) and the distance (D) is D=1.274L or D=1.196L.

Further, to make the sensed signal closer to the ideal sine wave signal, the shape of each of the first end and each of the second end can be circular, elliptical, parabolic, or hyperbolic, and simultaneously The varying width with the long axis direction makes it a trapezoid between the first end and the second end.

First, referring to Figures 2A, 2B and 3, the optical encoder (10) provided in a preferred embodiment of the present invention mainly includes a light source (20) and a main grating (30) , An indicating grating (40) and an optical sensing part (50).

The working principle of the optical encoder (10) and the relative spatial positional relationship between the constituent elements are similar to those disclosed in the prior art. The light generated by the light source (20) is transmitted through the main grating (30). After the disc reflects light (as shown in Figure 2B) or allows light to pass through (as shown in Figure 2A), it is sensed by the optical sensing portion (50) through the indicating grating (40), and passes through the optical The light intensity changes sensed by the sensing part (50), and the obtained signal can be used as the basis of calculation to analyze the rotation angle position of the rotating element connected to the main grating (30) to facilitate control, and among them, The optical sensing portion (50) may include a large number of photosensitive elements, but this is a technical subject disclosed in the prior art and not intended to be improved by the present invention, so there is no need to repeat it here.

Wherein, the indicating grating (40) structurally includes a grating plate (41), a plurality of first light-transmitting areas (42) and a plurality of second light-transmitting areas (43).

The shape and size of the grid plate (41) can be adapted to be installed on the optical sensing portion (50). In this embodiment, a rectangular plate-shaped body is taken as an example.

Each of the first light-transmitting regions (42) and each of the second light-transmitting regions (43) are formed on the grid plate (41) to form a three-dimensional structure through which light can pass, and each is on the grid plate (41). ) The same two-dimensional shape is formed on one of the side plates, which are arranged alternately along the rectangular long axis direction of the grid plate (41) to jointly form a grid plate (41) that can allow light to pass through. Transparent area.

Please refer to FIG. 4, in terms of the two-dimensional shape formed by each of the first light-transmitting regions (42) and each of the second light-transmitting regions (43) on one side of the grid plate (41), each of the first The length (L) of the shape of a light-transmitting area (42) and each of the second light-transmitting areas (43) is between a first end (421) (431) and a second end (422) (432) ), and the width of the shape is gradually increased from the first end (421) (431) to the second end (422) (432), so as to form the width ( W1) is narrower but adjacent to the width of the second end has a larger width (W2), so that the overall shape is slightly in the shape of a water drop. Furthermore, each of the first ends (421) (431) ) And the shape of each of the second ends (422) (432) are respectively arc-shaped, and the curvature of the arc is consistent with the curvature of a circle, an ellipse, a parabola, or a hyperbolic, etc., and in this embodiment The first ends (421) (431) and the second ends (422) (432) are respectively arc-shaped, and the radius of each first end (421) (431) is smaller than each of the first ends (421) (431). The radius of the two ends (422) (432) corresponds to the change of its own width; furthermore, the width of each of the first light-transmitting areas (42) and each of the second light-transmitting areas (43) changes in shape , Are respectively in their respective shapes, forming a trapezoidal area (423) (433) between the corresponding first end and the second end; wherein, for ease of understanding, the present invention is drawn as a dotted line in Figure 4 Between each of the first ends (421) (431) and the corresponding trapezoidal area (423) (433), and each of the second ends (422) (432) and the corresponding trapezoidal area (423) (433) The imaginary dividing line between, but the imaginary dividing line does not actually exist.

From the relative relationship with the grid (41):

Each of the first light-transmitting regions (42) is close to a first side (411) of one side of the rectangular long axis of the grid plate (41) and far away from a second side (411) opposite to the first side (411) (412), and make its second end (422) between its first end (421) and the first side (411);

Each of the second light-transmitting regions (43) is close to the second side (412) and far away from the first side (411), and has its second end (432) between its own first end ( 431) and the second side (412).

And by the relative state of each of the first light-transmitting regions (42) and each of the second light-transmitting regions (43) interlaced with each other, two adjacent first light-transmitting regions (42) and second light-transmitting regions (42) can be made The distance (D) between the respective second ends (422) (432) of the regions (43) is less than twice the length (L) of their respective shapes, so that each of the first light-transmitting regions ( 42) and the area of the light-transmitting area provided by each of the second light-transmitting regions (43) within the unit area of the grid plate (41).

Further, by changing the depth at which each of the first light-transmitting regions (42) and each of the second light-transmitting regions (43) intersect each other, the light intensity sensed by the optical sensing portion (50) can be changed more Close to the sine wave signal, and increase the proportion of light-transmitting area per unit area to achieve better light source utilization, so that the optical sensor (50) can increase the proportion of light-transmitting area under a higher proportion of light-transmitting area The number of photosensitive elements (not shown in the figure) it has is used to improve the error caused by uneven light intensity. At the same time, it can be reduced by high-density photosensitive elements under abnormal signals caused by foreign matter affecting light travel. The degree of influence of the abnormal signal enables the optical encoder (10) to provide a more accurate sensing result.

Under feasible implementation conditions, the interleaving depth between each of the first light-transmitting regions (42) and each of the second light-transmitting regions (43) satisfies the formula: L≦D<2L to achieve the invention Purpose and effect. In a better embodiment, D=1.274L or D=1.196L can be achieved. Under this condition, when used in some devices, the optical encoder (10) can achieve relatively better Good sensing accuracy.

(1): Grid (2): Transmissive area (10): Optical encoder (20): Light source (30) Main grating (40):: indicating grating (41): Grid (411): First side (412): second side (42): The first light transmission zone (421)(431): First end (422)(432): second end (423)(433): Trapezoid area (43): Second light transmission zone (50): Optical sensing part (W1)(W2): width (D): distance (L): length

Figure 1 is a plan view of a conventional indicating grating. Fig. 2A is a schematic diagram of a preferred embodiment of the present invention, showing a transmission type main grating. Fig. 2B is a schematic diagram of a preferred embodiment of the present invention, showing a reflective main grating. Fig. 3 is a plan view of an indicating grating in a preferred embodiment of the present invention. FIG. 4 is a partial enlarged view of a preferred embodiment of the present invention along the part A of FIG. 3. FIG.

(411): First side

(412): second side

(42): The first light transmission zone

(422)(432): second end

(43): Second light transmission zone

Claims (7)

An indicating grating of an optical encoder, including: A grid Most of the first light-transmitting regions are sequentially arranged on the grid plate; Most of the second light-transmitting regions are sequentially arranged on the grid plate, and are respectively located between adjacent ones of the first light-transmitting regions; wherein The first light-transmitting regions are close to a first side of the grid plate and away from a second side opposite to the first side, and the second light-transmitting regions are close to the second side. Away from the first side; Each of the first light-transmitting area and each of the second light-transmitting areas have the same shape, and the length of each shape is between a first end and a second end, and the width of the shape is from the The first end gradually increases toward the second end, and at the same time, the second ends of the individual shapes of the first light-transmitting regions are interposed between the first end and the first side of the first light-transmitting regions, and the second light-transmitting regions The second end of the individual shape of the light zone is between its own first end and the second side; and The distance (D) between the second end of the first light-transmitting area and the second end of the second light-transmitting area that are adjacent to each other, and the length in shape of the first light-transmitting area or the second light-transmitting area (L), the system satisfies the following formula: L≦D<2L. The indicating grating of the optical encoder as described in claim 1, where D=1.274L. The indicating grating of the optical encoder as described in claim 1, where D=1.196L. The indicating grating of the optical encoder according to claim 1, wherein the shape of each of the first ends is a part of a circle, an ellipse, a parabola, or a hyperbolic shape, respectively. The indicating grating of the optical encoder according to claim 4, wherein the shape of each of the second ends is a part of a circle, an ellipse, a parabola, or a hyperbolic shape, respectively. The indicating grating of the optical encoder according to claim 5, wherein the diameter of each of the first ends is smaller than the diameter of each of the second ends. The indicating grating of an optical encoder according to claim 1 or 6, wherein each of the first light-transmitting area and each of the second light-transmitting areas are respectively located between the first end and the two ends in shape , Departments are trapezoidal respectively.

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