JPH0240157A - Detector - Google Patents

Abstract

PURPOSE:To improve stability and detecting accuracy by providing a light receiving element to always receive light from a light emitting element, a light receiving element whose whole photoreceiving plane is covered with a body to be detected, and a light receiving element in which part of the photoreceiving plane is covered according to the relative movement of the body to be detected. CONSTITUTION:The light emitting element 1 is arranged oppositely to a photoreceiving part 2 which receives the light from the light emitting element 1, and the body to be detected 3 being moved relatively for them is arranged in the neighborhood of the photoreceiving plane of the photoreceiving part 2 between the light emitting element 1 and the photoreceiving part 2. The photoreceiving part 2 consists of three light receiving elements (a), (b), and (c) arranged in a line in a direction intersecting orthogonally to the moving direction of the body 3 to be detected i.e. the width direction of the body 3 to be detected, and the light receiving element (a) always receives the light from the light emitting element 1 in spite of the relative movement of the body 3 to be detected, and detects its output characteristic. Also, as for the light receiving element (b), part of the photoreceiving plane is covered with the body 3 to be detected. and its range changes according to the relative movement of the body 3 to be detected, and the light receiving element (c) is always covered with the body 3 to be detected in spite of the relative movement of the body 3 to be detected, and can detect a dark current and disturbance light. In such a way, it is possible to compensate a position detecting signal, and to improve the accuracy and the stability.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a detection device that optically detects the position of a detected object using a light emitting element and a plurality of light receiving elements.
For example, it can be used to detect the position of a tape or other paper in a tape recorder.

(Prior Art) A device as shown in FIG. 7 is known as a conventional example of a device for optically detecting a change in the position of a detected object. This is to detect the rotational position of the pickup arm in the record player 26. A wedge-shaped window hole 25 is formed in the shutter plate 24, which rotates integrally with the pink-up arm. The light emitting element 2I and the first light receiving element 22 are placed in between, and the second light receiving element 21 always receives light from the light emitting element 21 regardless of the rotational position of the shank 24.
A light receiving element 23 is arranged. Since the output of the first light-receiving element 22 changes depending on the position of the window hole 25, that is, the rotational position of the pickup arm, the rotational position of the pickup arm can be detected from the output of the first light-reception element 22. Here, if the amount of light on the light-receiving surface of the light-receiving element changes due to fluctuations in the output of the light-emitting element 21 or other causes, the accuracy of detecting the position of the object to be detected will decrease, so the output of the second light-receiving element 23 is fed to the light-emitting element 21. The light emitting output of the light emitting element 21 is controlled by hacking, so that the output of the light emitting element 21 is always constant.

(Problem to be solved by the invention) The light-receiving surface of the light-receiving element is spread out with a certain area,
When the object to be detected moves relatively, the area of the light-receiving surface of the light-receiving element covered by the object to be detected changes, and the output of the light-receiving element changes. Here, for example, if the shape of the light-receiving surface of the light-receiving element is
If the shape is rectangular as shown in the figure, the change in the output of the light receiving element with respect to the change in the position of the object to be detected will have a linear relationship as shown in FIG. Line (1) shown in FIG. 8 is for an ideal light receiving element, and if the amount of light received by the light receiving element becomes zero depending on the position of the object to be detected, the output of the light receiving element also becomes zero.

However, the photodetector has a certain amount of dark current,
Further, a current flows due to the influence of external light other than light from the light emitting element. Therefore, as shown by A and B in Figure 8, even when the amount of light from the light emitting element is zero, it will have a certain output, and as shown by line (2), the output will increase overall and the ideal Line (1) may be translated in parallel, or line (3)
As shown in , the ratio of change in output to change in amount of received light changes, and the slope of the line changes.

When lines (2) and (3) appear, even if the detection output of the second light-receiving element 23, which directly receives light from the light-emitting element 21 as in the conventional detection device shown in FIG. It is not possible to compensate for the effects of current or disturbance light from the outside, causing measurement errors and making it impossible to accurately detect the position of the object to be detected.

The present invention has been made to solve the problems of the prior art, and is a detection device with high stability and detection accuracy by compensating for the effects of fluctuations in the output of the light emitting element, dark current of the light receiving element, ambient light, etc. The purpose is to provide

(Means for Solving the Problems) The present invention provides an optical detection device comprising a light emitting element and a light receiving element, in which the light receiving part always receives light from the light emitting element regardless of relative movement of a detected object. It is characterized by having a light-receiving element that receives light, a light-receiving element whose entire light-receiving surface is covered by the object to be detected, and a light-receiving element whose light-receiving surface is partially covered with relative movement of the object to be detected. do.

(Function) The position of the object to be detected can be detected from the output of the light-receiving element whose light-receiving surface is partially covered as the object moves relative to the object. Fluctuations in the output of the light-emitting element can be detected by the light-receiving element that always receives light from the light-emitting element regardless of the relative movement of the object to be detected, and thereby the fluctuation in the output of the light-emitting element can be compensated for. The influence of the dark current of the light receiving element and the disturbance light can be compensated by the output of the light receiving element whose entire light receiving surface is covered by the object to be detected.

(Example) Hereinafter, an example of the detection device according to the present invention will be described with reference to FIGS. 1 to 6.

The embodiment shown in FIG. 1 shows an example in which the detection device according to the present invention is applied to a tape edge position detection device for improving the relative position accuracy between a magnetic tape and a magnetic head in a tape recorder. In FIG. 1, a light emitting element 1 and a light receiving section 2 that receives light from the light emitting element 1 are arranged to face each other.

The light emitting element 1 can be composed of, for example, an LED. Between the light emitting element 1 and the light receiving part 2, a detected object 3 that moves relative to the light emitting element 1 and the light receiving element 2 is arranged at a position close to the light receiving surface of the light receiving part 2. The object to be detected 3 is a magnetic tape in this embodiment, and is transported in a direction perpendicular to the plane of the paper in FIG. The output of the light receiving section 2 is the output of the detected object 3.
changes when the position changes in the vertical direction indicated by the arrow and the amount of light received from the light emitting element 1 changes, so the vertical position of the detected object 3 can be detected from the output of the light receiving section 2. .

As shown in FIG. 2, the light receiving section 2 consists of three light receiving elements a, b, and c arranged in a direction perpendicular to the direction of movement of the detected object 3, that is, in the width direction of the detected object 3. Become. The light-receiving surfaces of the light-receiving elements a, b, and c are formed in a rectangular shape with the same shape and the same area, and the light-receiving elements a, b, and c are provided close to each other within the same chip. Here, the vertical dimension of each light receiving element is 1, and the horizontal dimension is L. The light receiving section 2 of the object to be detected 3 is positioned so that its upper edge moves relative to the light receiving surface of the central light receiving element. Therefore 1. The upper light-receiving element a of the Hllil light-receiving elements ab and c always receives light from the light-emitting element 1 regardless of the relative movement of the detected object 3. This is for detecting the output characteristics of the light emitting element 1. A part of the light-receiving surface of the intermediate light-receiving element is covered by the object 3 to be detected. The range covered by the detected object 3 changes with the relative movement of the detected object 3, and the output of the light receiving element changes accordingly, so the position of the detected object changes from the change in the output of the light receiving element. can be detected.

The entire light-receiving surface of the lower light-receiving element C is always covered by the object 3 regardless of the relative movement of the object 3 . Dark current and disturbance light can be detected from the output of this light receiving element C.

Now, assuming that the detected object 3 is not approaching the detection device according to this embodiment, the light from the light emitting element 1 is directly incident on the three light receiving elements a, b, and c, and each light receiving element is The outputs of both elements have the same value. At this time, the output of each light-receiving element reaches its maximum value as shown by black squares in the graph of FIG.

Next, the object to be detected 3 approaches and the light emitting element 1 and the light receiving part 2
When the light enters the optical path between the detected object 3 and the light-receiving surfaces of the light-receiving elements a, b, and c, the relationship is as described above. That is, the light-receiving element a always receives light from the light-emitting element regardless of the position of the object 3 to be detected, and outputs a value as shown by ■ in the graph of FIG. As a result, the light emitting element 1
This will detect the output characteristics of. Further, a part of the light receiving surface of the light receiving element is covered with the object to be detected 3, and receives a part of the light from the light emitting element 1, and outputs a value as shown by black in the graph of FIG. As a result, the position of the detected object 3 (edge position in the width direction of the detected object 3) is detected.

Furthermore, although the light-receiving surface of the light-receiving element C is always covered by the detected object 3 regardless of the position of the detected object 3, a dark current flows and a current based on disturbance light flows, so that the graph in FIG. As shown in ■, there is a certain amount of output.

If the detected object 3 is a magnetic tape as in this embodiment, the light transmitted through the magnetic tape enters the light receiving element C. Also includes signals based on

Now, with the position of output ■ of light receiving element C as a reference, let X be the position of output ■ of light receiving element A, and 1 be the position of output ■ of light receiving element a. The element 1 corresponds to the range in which light is received from the light emitting element 1, that is, the position of the detected object 3, and 1 corresponds to the vertical direction of the light receiving element b, which is the relative movement direction of the detected object 3 mentioned above. Corresponds to the dimensions.

The detection signals of each of the light receiving elements a, b, and c as described above are
By inputting the data to the arithmetic circuit shown in the figure, the position of the detected object 3 can be detected with high accuracy. In Figure 3,
The outputs of each light receiving element a, b, c are outputted by amplifiers 11 and 1, respectively.
2.13, the amplified output Vl, V2. It is considered to be V3. Output ■1 and V2 are input to the subtracter 14 and Vl-V2=V
4 is obtained, and the signal V4 is amplified and input to the divider 16. Further, the outputs ■2 and ■3 are input to the subtracter 15 to obtain V3-V2=V5, and the signal ■5 is amplified and input to the divider 16. The divider 16 calculates and outputs V5/V4, that is, (V3-V2)/(VIV2).

The relationship between this calculation output and the above-mentioned The moving position of the detected object 3 can be detected from the calculation output of the detector 16. If this detection signal is fed back to, for example, the position correction means of the detected object 3, the position of the detected object 3 can be adjusted to the correct position. can be retained.

According to the above embodiment, the arithmetic output signal of the divider 16 becomes a signal in which the output characteristics of the light emitting element 1 are compensated by the output of the light receiving element a, and the output of the light receiving element C is used to reduce dark current, ambient light, and interference. Since the signal is compensated for the influence of light transmitted through the detection object 3, etc., various factors that impede detection accuracy are removed, and extremely high-precision detection can be performed. Also,
Since each light receiving element a, b, and c are built in close proximity on the same chip, temperature changes of each light receiving element and uniformity of the light receiving surface may occur.
It is possible to accurately correct output changes due to dirt, etc. The same applies to correction for changes in the output of the light emitting element 1.

In the embodiments described above, the light emitting element 1 and the light receiving section 2 are arranged facing each other so that the light from the light emitting element 1 is directly received by the light receiving section 2. However, as shown in FIG. , the light from the light emitting element 1 is reflected by the mirror 4, the light reflected by the mirror 4 is received by the light receiving section 2, and the detected object 3 is relatively moved on the reflected optical path from the mirror 4 to the light receiving section 2. may be placed. The light receiving unit 2 has three light receiving elements configured similarly to the light receiving elements a, b, and c in the above-described embodiment, and detects the position of the detected object 3 through an arithmetic circuit as shown in FIG. Assume that a signal is output. Note that the light-emitting element 1 and the light-receiving section 2 in FIG. 5 may be interchanged, and the arrangement relationship may be such that the detected object 3 is located on the irradiation optical path from the light-emitting element 1 to the mirror 4.

If the object to be detected 3 is of a reflective type, such as a magnetic tape, the light receiving section 2 receives the light reflected from the light emitting element 1 by the object to be detected 3, as shown in FIG. Good too. In this case, the light receiving section 2 also transmits light from the light emitting element 1 reflected by the detected object 3 to the detected object 3.
A light receiving element that always receives light regardless of the relative movement of the light receiving element, a light receiving element that receives part of the light from the light emitting element 1 reflected by the detected object 3, and a light receiving element that receives part of the light from the light emitting element 1 reflected by the detected object 3. It is composed of a light-receiving element on which no light enters.

Note that the detection device according to the present invention is applicable not only to detecting the position of a magnetic tape, but also as an edge position detection device for paper, sheets, and other objects. Furthermore, even if the object to be detected transmits light and there are variations in light transmittance, it is possible to compensate by hacking the output of the light-receiving element whose entire light-receiving surface is covered with the object to be detected. Therefore, highly accurate position detection is possible.

The shape of the light-receiving element is not limited to a rectangle, and may be round, triangular, or other shapes. Also, 3
The areas and shapes of the individual light receiving elements do not necessarily have to be the same, and may be different from each other.

(Effects of the Invention) According to the present invention, in addition to the light receiving element that detects a change in the relative position of the detected object, there is also a light receiving element and a light receiving surface that always receive light from the light emitting element regardless of the relative movement of the detected object. Since the light-receiving element is provided so that the entire area is always covered by the object to be detected, it is possible to detect the dark current of the light-receiving element, ambient light, and output fluctuations of the light-emitting element, etc., thereby compensating the position detection signal of the object to be detected. Therefore, highly accurate and stable position detection can be performed.

[Brief explanation of the drawing]

FIG. 1 is an optical layout diagram showing one embodiment of the detection device according to the present invention, FIG. 2 is a front view showing the relationship between the light receiving section and the detected object in the same embodiment, and FIG. FIG. 4 is a circuit diagram showing an example of an applicable arithmetic circuit, FIG. 4 is a diagram showing the relationship between the output change of the light receiving element and the position of the object to be detected in the above embodiment, and FIG. 5 is a diagram showing another example of the detection device according to the present invention. FIG. 6 is an optical layout diagram showing yet another embodiment of the detection device according to the present invention, FIG. 7 is a perspective view showing an example of a conventional detection device, and FIG. FIG. 2 is a diagram showing the relationship between the output of a light receiving element and the position of a detection object. 1. Light emitting element 2. Light receiving section 3. Object to be detected a,
b, c...light receiving element-) 1g

Claims (1)

[Claims] A detection device that includes a light emitting element and a light receiving part that receives light from the light emitting element, and detects the position of a detected object that moves relatively on an optical path from the light emitting element to the light receiving part by the output of the light receiving part. In the light receiving section, the light receiving element always receives light from the light emitting element regardless of the relative movement of the detected object, the light receiving element whose entire light receiving surface is covered by the detected object, and the relative movement of the detected object. 1. A detection device comprising a light receiving element whose light receiving surface is partially covered as it moves.