JP3509446B2 - Optical coupling device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupling device used for detecting the position and displacement amount of an object to be detected.

[0002]

2. Description of the Related Art In recent years, a transmission type optical coupling device (photointerrupter) for detecting the presence or absence of an object to be detected has been used in a wider range of applications in recent years.
It has become necessary to accurately detect the position of the detected object. For example, in a storage device such as an FDD or a CD-ROM driver, it is necessary to detect the head position for reading with high accuracy. Further, in the ink jet printer, since the ink is ejected onto the printing paper, it is necessary to accurately match the distance between the printing surface and the print head portion.

9 and 10 show a conventional optical coupling device used in the above-mentioned OA equipment or FA equipment. In the figure, reference numeral 1 denotes a light emitting element, and an infrared light emitting diode chip is generally used. The light emitting element 1 is a lead frame 2
Is die-bonded with silver paste or the like, and is wire-bonded with the lead frame 4 with the gold wire 3 to be electrically connected. Then, the light emitting element 1 and the lead frames 2, 4
And a part of the gold wire 3 are molded by the translucent resin body 5.

Reference numeral 6 denotes a light receiving element, which is a photodiode or a phototransistor chip, is die-bonded to the lead frame 7 with silver paste or the like, and is wire-bonded to the lead frame 8 with the gold wire 3 for electrical connection. ing. The light receiving element 6, a part of the lead frames 7 and 8 and the gold wire 3 are molded with a light-transmissive resin body 9.

The light-transmitting side light-transmitting resin body 5 and the light-receiving side light-transmitting resin body 9 are housed in a case 10 made of a light-shielding resin, and are arranged to face each other with a passage 11 for the object H to be detected in between.
A light emitting side slit 12 and a light receiving side slit 13 are provided on the side surface of the case 10 facing the passage 11. When there is no object H to be detected, an optical path 14 is formed from the light emitting element 1 to the light emitting side slit 12, the light passing side path 11, the light receiving side slit 13, and the light receiving element 6. Reference numeral 15 in the drawing denotes an optical lens for condensing.

FIG. 11 shows changes in the amount of light received by the light receiving element 6 with respect to the amount of movement L when the object H to be detected moves as shown by the arrow in FIG. The change in the amount of received light when the slit width W is widened is shown by the solid line X, and the slit width W
If is narrowed, it becomes like a one-dot chain line Y. Therefore, by narrowing the slit width, it is possible to improve the position detection accuracy of the detected object H.

FIG. 12 is a diagram showing a signal processing circuit in the above optical coupling device. The light emitting element 1 emits light by passing a forward current IF. The light receiving element 6 is a photodiode, and when receiving the light from the light emitting element 1, a photocurrent Isc is generated. Reference numeral 16 denotes an amplifier, which has a photocurrent Isc
Is amplified and current-voltage conversion is performed to output V ₁
Cause Reference numeral 17 denotes a comparator, which compares the output V ₁ with the reference voltage Vref, and when V ₁ <Vref,
When the output Vo is set to the low level and V ₁ > Vref,
The output Vo is set to the high level.

Therefore, as shown in FIG.
13 is moved, the relative amount of light received by the light receiving element 6 is
When the detected object H is moved to the position L1 at which the voltage Vref changes to the reference voltage Vref ₁ or less, the output Vo changes from the High level to the Low level, and the detected object H
Detects that the vehicle has passed that position.

[0009]

However, the light emitting element 1
The infrared light emitting diode chip used in the above has a reduced light emission output when energized for a long time. This change is up to 50% when the light emitting element 1 is covered with a transparent resin.
A decrease of about (50,000 hr) is expected. When this output decrease occurs, the amount of light incident on the light receiving element 6 also decreases. Therefore, the output V _{1 of the} amplifier 16 also decreases, and the reference voltage Vref for the relative amount of received light changes from the position of Vref ₁ to Vref ₂ , and the position for detecting the detected object H moves from L1 to L2. Then, the detectable position changes.

In order to reduce the fluctuation of the detection position, it is possible to reduce the width W of the slits 12 and 13 as described above.
Since it is formed by injection molding, it is difficult to set the slits 12 and 13 to about 0.2 mm or less because of the structure. Further, if the slit width W is narrowed, the amount of light received by the light receiving element 6 in the absence of the object H to be detected decreases.
It is necessary to increase the amplification factor of, and there is a problem that the influence on noise also increases.

Further, since the output V _{1 of the} amplifier 16 is proportional to the moving amount L of the detected object H within the range of the slit width W, the moving amount L of the detected object H can be detected from the change in the output. However, as described above, when the output of the light emitting element 1 is reduced, the output of the amplifier 16 also changes, so that the detected movement amount L changes.

In view of the above, it is an object of the present invention to provide an optical coupling device capable of highly accurate position detection by obtaining a stable output from a light receiving element irrespective of output variation of the light emitting element.

[0013]

According to the present invention, a light emitting element and a light receiving element are arranged so as to face each other with a passage of an object to be detected in between, and a light for detecting the position of the moving object is detected. In the coupling device, the light receiving element includes a plurality of light receiving portions divided by a boundary line that obliquely crosses a moving axis of the object to be detected.

According to this, since the amount of light received by each light receiving unit changes with the movement of the object to be detected, the output variation of the light emitting element is influenced by the relative relationship of the amount of received light. It is possible to obtain an output from a light receiving element that does not exist.

Therefore, an arithmetic circuit for calculating the position of the object to be detected from the amount of light received by each light receiving section is provided. That is, by calculating and outputting the rate of change in the ratio of the amount of light received by an arbitrary light receiving unit to the total amount of received light, it is possible to recognize how much the detected object has moved from the reference position. Is detected. Further, by converting the above output into an electrical change amount, the movement amount of the detected object can be obtained as an absolute value.

In the above calculation, if all the light from the light emitting element is blocked by the object to be detected, the amount of light received by each light receiving section becomes 0, which may cause an abnormality in the calculation. The arithmetic circuit has a function of fixing the output to a constant value when the sum of the amount of light received by each light receiving unit becomes equal to or lower than a predetermined level. As a result, stable calculation can always be performed, and reliability can be improved.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The optical coupling device of this embodiment is shown in FIG.
As shown in FIG. 3, the light emitting element 1 and the light receiving element 20 are of a transmissive type, which are opposed to each other with the passage 11 of the detected object H interposed therebetween, and detect the position of the moving detected object H.

The light receiving element 20 is a two-divided photodiode chip (or phototransistor chip), and is divided into two light receiving portions 22a, 22b divided by a boundary line 21 diagonally crossing the movement axis G of the object H to be detected. Become.
That is, the light receiving portions 22a and 22b are obtained by equally dividing a rectangular plane, which is the planar shape of the light receiving element 20, into two regions by diagonal lines, and the diagonal lines cross the movement axis G obliquely.

Then, the light receiving element 20 is die-bonded to the mounting lead frame 23 with silver paste or the like, and the respective light receiving portions 22a and 22b are wire-bonded to the different lead frames 24 and 25 by the gold wire 3, respectively. A connection is being made. The light receiving element 20, the gold wire 3 and parts of the lead frames 23, 24, 25 are molded with a light transmitting resin to form a light receiving side light transmitting resin body 26.

The light emitting element 1 uses the same infrared light emitting diode chip as the conventional one, and the other structures and arrangements are the same as those of the conventional one, and therefore detailed description will be omitted.

Here, the light emitted from the light emitting element 1 is condensed by the optical lens 15, and the parallel optical axes 27a to 27a.
7c, passing through the light emitting side slit 12 of the case 10, passing through the passage 11 of the detected object H, and receiving side slit 1
After passing through 3, the light enters the light receiving element 20.

FIG. 2 shows a circuit block diagram of the optical coupling device. The light receiving portions 22a and 22b of the light receiving element 20 are connected to the amplifiers 28a and 28b, respectively.
The output currents Isc ₁ and Isc ₂ of b are amplified, and the current −
Performs voltage conversion. The outputs A and B of these amplifiers 28a and 28b are input to the arithmetic circuit 29, and in the arithmetic circuit 29,
The calculation of Vo = A / (A + B) is performed and output as Vo. As a result, the position or movement amount of the detected object H can be detected from the calculation result based on the light receiving amounts of the light receiving units 22a and 22b.

The amplifiers 28a and 28b and the arithmetic circuit 29 are mounted on a circuit board on which a lead frame is mounted, and the circuit board is housed in the case 10. Although the light receiving element 20, the amplifiers 28a and 28b, and the arithmetic circuit 29 are provided separately here, they may be integrated on the same chip. By doing so, the optical coupling device can be downsized. Can be achieved.

Next, the operation of the above circuit will be described with reference to a specific movement when the object H to be detected moves along the passage 11. Here, as shown in FIG.
Moves vertically on the passage 11 from top to bottom. The same circuit operation is performed when the detected object H moves horizontally on the passage 11.

When the detected object H moves by L with one end of the light receiving element 20 being 0, the light receiving state of the light receiving element 20 changes by covering the optical axes 27a to 27c. In one light receiving portion 22a, the portion P is shielded from light and the portion Q receives light. Similarly, in the other light receiving portion 22b, the R portion is shielded from light and the S portion is in a light receiving state. The output current Isc ₁ proportional to the amount of received light in the Q portion is amplified and current-voltage converted by the amplifier 28a to become the output A. Further, the output current Isc ₂ proportional to the amount of light received at the S portion is output by the amplifier 28.
It is amplified and current-voltage converted by b, and becomes the output B.

FIG. 4 shows the change characteristic of the light receiving area as a change characteristic with respect to the movement amount L of the object H to be detected. However, the light receiving area of the light receiving portions 22a and 22b when the detected object H is at the position of 0 is 100%.

A is the output obtained by amplifying the output current Isc ₁ proportional to the light receiving area of one light receiving portion 22a, and B is the output obtained by amplifying the output current Isc ₂ proportional to the light receiving area of the other light receiving portion 22b. Therefore, when the amplification factors of the amplifiers 28a and 28b are the same, the change situation of the outputs A and B is as shown in FIG.
It is the same as the change in area of Q and S shown in.

Therefore, the output Vo which is the calculation result in the calculation circuit 29 becomes Vo = A / (A + B), and the detected object H with respect to the length L ₂ of the light receiving element 20 in the moving axis direction.
From the relationship between the amount of movement L of light and the changes in the light receiving areas Q and S, Vo =
It becomes 0.5 + 0.5 (L / L ₂ ), and as shown in FIG. 5, the output Vo changes linearly from 0.5 to 1.0 with respect to the movement amount L. Further, since the change in the output Vo is output as a ratio with respect to the movement amount L, each of the light receiving units 22a, 2a.
It has nothing to do with the absolute value of the amount of light incident on 2b. Therefore, even if the output of the light emitting element 20 changes, the output Vo does not change with respect to the movement amount L. For example, the position where Vo is 0.75 is always L = except for the error on the circuit.
The position of L _2/2. Therefore, the same output Vo can always be obtained for the absolute position of the detected object H regardless of the output fluctuation of the light emitting element 1. This means that if the error on the circuit is ignored, it is possible to obtain a result in which the detected position of the detected object H is not displaced, and it is possible to detect the position with high accuracy.

Further, since the output Vo is a linear output varying from 0.5 to 1.0 within the range of the length L ₂ of the light receiving element 20, the movement amount of the detected object H from the output Vo is an absolute value. It is also possible to ask for.

Here, in the case of performing the above calculation, when the moving distance L of the detected object H becomes larger than L ₂ ,
There is a possibility that the detected object H blocks all the light from the light emitting element 1, the amount of light received by each of the light receiving portions 22a and 22b becomes 0, the output current becomes 0, and the calculation becomes abnormal. As a countermeasure against this, in the arithmetic circuit 29, when the output (A + B) corresponding to the sum of the light receiving amounts of the respective light receiving units 22a and 22b is below the level at which the noise tolerance is lost, the output Vo is set to 1.
This can be solved by adding the function of fixing to 0. Therefore, the reliability of the calculation result is increased, and stable position detection can be performed.

The present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention.

For example, as the light receiving element 20, two light receiving portions 2 shown in FIG.
You may use the light receiving element divided into 2a and 22b.

Further, the light receiving element 2 divided into four shown in FIG.
0 may be used, and the circuit configuration is as shown in FIG. At this time, even when the detected object H moves from an oblique direction as indicated by an arrow, each of the light receiving portions 22a, 22a
Since the incident state of light on b, 22c, and 22d changes,
The outputs A, B, C, D from the amplifiers 28a, 28b, 28c, 28d also change, and the position or the moving distance of the detected object H can be detected. As a result, it is not necessary to dispose the optical coupling device in consideration of the moving direction of the detected object H, and the versatility as an optical coupling device capable of position detection is enhanced.

[0034]

As is apparent from the above description, according to the present invention, the light emitting element and the light receiving element are arranged so as to face each other with the passage of the object to be detected in-between, and the light receiving element obliquely moves along the axis of movement of the object to be detected. Since it is composed of a plurality of light receiving units divided by a boundary line that crosses, the light receiving amount of each light receiving unit changes due to the movement of the detected object, by calculating the relative relationship of the light receiving amount of each light receiving unit, The output of the light receiving element corresponding to the movement amount of the detected object can be obtained.

Therefore, it is possible to stably detect the position or the amount of movement of the object to be detected, without being affected by the temporal change in the output of the light emitting element. This makes it possible to provide an optical coupling device suitable for use in OA equipment or FA equipment and capable of highly accurate position detection.

By fixing the output to a constant value when the sum of the amount of light received by each of the light receiving sections becomes equal to or lower than a predetermined level, stable calculation can be always executed and reliability can be improved.

Further, by integrating the light receiving element and the arithmetic circuit on the same chip, the size can be reduced.

[Brief description of drawings]

FIG. 1 shows an optical coupling device according to an embodiment of the present invention,
(A) is a cross-sectional view thereof, and (b) is a plan view of a light receiving element.

FIG. 2 is a circuit block diagram of an optical coupling device.

FIG. 3 is a diagram showing a light receiving state of a light receiving element when an object to be detected moves.

FIG. 4 is a diagram showing a change in a light receiving area of a light receiving unit with respect to a movement amount of a detected object.

FIG. 5 is a diagram showing the relationship between the amount of movement of the detected object and the output of the light receiving element.

FIG. 6 is a plan view of a light receiving element according to another embodiment.

FIG. 7 is a plan view of a light receiving element according to another embodiment.

FIG. 8 is a circuit block diagram of another embodiment.

FIG. 9 is a sectional view of a conventional optical coupling device.

FIG. 10 is a diagram showing a state in which an object to be detected moves along a passage.

FIG. 11 is a diagram showing changes in the amount of light received by the light receiving element with respect to the amount of movement of the detected object due to the difference in slit width.

FIG. 12 is a diagram showing a conventional signal processing circuit.

FIG. 13 is a diagram showing the relationship between the amount of movement of the detected object and the amount of light received by the light receiving element.

[Explanation of symbols]

1 Light emitting element 11 passage 20 Light receiving element 22a, 22b Light receiving part 29 Arithmetic circuit G movement axis H Object to be detected

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 31/12-31/173

Claims (3)

(57) [Claims] 1. An optical coupling device for detecting a position and a moving amount of a moving object to be detected, wherein a light emitting element and a light receiving element are arranged so as to face each other with a passage of the object to be detected interposed therebetween. Is a rectangular shape, and is composed of four light-receiving sections which are divided into four by two diagonal lines diagonally crossing the moving axis of the detected object. The position of the detected object is determined by the amount of light received by each light-receiving section. And an arithmetic circuit for calculating the amount of movement, and the arithmetic circuit calculates and outputs a rate of change in the ratio of the amount of light received by any light receiving unit to the sum of the amount of light received by each light receiving unit. Optical coupling device. 2. The arithmetic circuit fixes the output to a constant value when the light receiving element is shielded by the object to be detected and the sum of the light receiving amounts of the respective light receiving sections is below a predetermined level. 1. The optical coupling device according to 1. 3. The light receiving element and the arithmetic circuit are on the same chip.
The integrated circuit according to claim 1 or 2, wherein
Optical coupling device.