JPH0476071B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an optical detection device that optically detects the presence or absence of an object to be detected.

BACKGROUND ART FIG. 1 is a sectional view of a detection device 1 showing a prior art. The light emitting optical fiber 2 and the light receiving optical fiber 3 are supported by a support base 4 at a certain angle. A detection area 5 is an intersection area between a light projection area emitted by the light emitting optical fiber 2 and a light receiving area received by the light receiving optical fiber 3.
is an area for detecting the presence or absence of a detected object (not shown). When there is an object to be detected in the detection area 5, the presence or absence of the object can be detected by changing the amount of light received by the light-receiving optical fiber 3.

In this prior art detection device, malfunctions sometimes occurred due to differences in reflectance of objects to be detected.
In addition, the light emitting optical fiber 2 and the light receiving fiber 3 are
Another drawback was that the device was large because it was supported at a certain angle.

Purpose An object of the present invention is to be able to detect the presence or absence of a detected object without causing malfunction even for detected objects with different reflectances, and to also measure the moving distance of the detected object. An object of the present invention is to provide an optical detection device that can be configured to have a small size.

Configuration of the Invention The present invention includes a focusing lens, a focusing lens provided at a position offset from the optical axis of the focusing lens,
a light projecting means for projecting light onto the focusing lens on one end side in the optical axis direction of the focusing lens; a first light-receiving means for receiving direct reflected light via a converging lens from the object to be detected, which is provided on the other end side in the optical axis direction of the converging lens; a second light-receiving means for receiving diffusely reflected light from an object via a converging lens; a first logarithmic circuit for calculating a logarithmic value of the output of the first light-receiving means; and a second logarithmic circuit for calculating a logarithmic value of the output of the second light-receiving means. and a subtraction circuit for determining the difference between the outputs of the first logarithm circuit and the second logarithm circuit.

Embodiment FIG. 2 is a simplified diagram showing the light path of an optical detection device 10 according to an embodiment of the present invention. The optical detection device 10 includes a light projecting means 11, a first light receiving means 12, a second light receiving means 13, and a focusing lens 14.
Consists of. In the following description, this focusing lens 14
is sometimes abbreviated as lens 14. Light projecting means 11, first light receiving means 12 and second light receiving means 13
is realized by optical fiber. Since the optical detection device 10 is composed of an optical fiber and a lens, its shape can be made small. The light projected from the light projecting means 11 is converged by the lens 14 and irradiated onto the object 15 to be detected. The path of the light projected from the light projecting means 11 is indicated by reference numeral g1. The object to be detected 15 is located at the intersection point G of the light path g1 and the optical axis g2 of the lens 14.

Directly reflected light reflected from the object to be detected 15 is incident on the first light receiving means 12 . The path of the directly reflected light at this time is indicated by reference numeral g3.

The distance r1 is between the exit point from the lens 14 and the optical axis g.
It is the distance between 2 and 2. The distance r1a is the lens 14
It is the distance between the point of incidence on the optical axis g2 and the optical axis g2. Since the detected object 15 is located at the intersection point G of the path g1 and the optical axis g2, the distance r1a is the distance r1
is equal to The distance r2 is the distance between the emission position of the light projecting means 11 and the optical axis g2. The distance r2a is the distance between the incident position of the first light receiving means 12 and the optical axis g2. Since the distances r1 and r1a are equal, the distance r2a is equal to the distance r2.

In this way, the paths g1 and g3 are symmetrical with respect to the optical axis g2, and therefore the light transmitting means 11 and the first light receiving means 12 are provided at symmetrical positions with respect to the optical axis g2.

The diffusely reflected light diffused by the lens 14 is shown by paths g4 and g5. The second light receiving means 13 is arranged so that the intersection point of the paths g4 and g5 at this time is on the light receiving end surface of the second light receiving means 13.

The light projecting means 11 is provided at a position shifted upward in FIG. 2 from the optical axis g2 of the lens 14. (direction) to project light onto the lens 14.
The first light receiving means 12 is provided at a position symmetrical to the light projecting means 11 with respect to the optical axis g2 on one end side of the lens 14 in the optical axis direction (left side in FIG. 2). This 14th
The light receiving means 12 receives directly reflected light via the lens 14 from the detected object 15 provided on the other end side in the optical axis direction of the lens 14 (right side in FIG. 2).
The second light receiving means 13 is provided on the optical axis g2 at one end of the lens 14 in the optical axis direction (left side in FIG. 2), and receives the diffusely reflected light from the object 15 to be detected via the lens 14. In this way, the present optical detection device is configured to be able to receive and detect diffusely reflected light and directly reflected light with one configuration. The first light receiving means 12 serves to receive the direct reflected light from the light projecting means 11, and the second light receiving means 1 serves to receive the diffusely reflected light.
It is 3. The first light receiving means 12 is arranged symmetrically with the light projecting means 11 with respect to the optical axis g2 in order to receive the linearly reflected light from the light projecting means 11, thereby directly reflecting the light. The light is incident on the first light receiving means 12 such that the angle of incidence and the angle of reflection are equal. The second light receiving means 13 that receives the diffusely reflected light is arranged at a position shifted from the symmetrical position with respect to the light projecting means 11 with respect to the optical axis g2, that is, in this embodiment, the second light receiving means 13 is located on the optical axis of the focusing lens. established in

The distance from one end surface 14a of the lens 14a to time point G is defined as distance l1. Light path g1 and optical axis g2
Let the angle with θ1 be θ1. The distance l1 at this time is expressed by the first equation.

l1=r11/tanθ1 (1) Let n ₀ be the refractive index at the center of the lens 14, let the refractive index distribution constant of the lens 14 be √, and let P be the pitch. The length of the lens at this time is Z=P2π/√A. The other end surface 14b of the lens 14 and the second light receiving means 1
3 is the distance l2. The relationship between l1 and l2 can be expressed by equation (2).

l1=1/n ₀ √A×n ₀ l2√A(co
s√AZ+sin√AZ)／n ₀ l2√A(sin√AZ−sin√AZ)……
(2) The relationship between the incident position and the exit position of the lens can be expressed by the third equation.

The distances of each part of the optical detection device 10 can be determined by the first, second, and third equations.

The light projected from the light projecting means 11 is directed towards the object to be detected 1
By detecting the direct reflected light and the diffusely reflected light from the detected object 15, the presence or absence of the detected object can be detected.

When a detected object 15 having a predetermined reflectance is placed at a point G, the first light receiving means 12 and the second light receiving means 12
The amounts of received light incident on the light receiving means 13 are defined as reference amounts of received light P1 and P2, respectively. Assume that the reflectance changes by changing the detected object 15 and the amount of received light becomes S% of the reference amount of received light. The amounts of light received by the first light receiving means 12 and the second light receiving means 13 at this time are assumed to be the received light amounts PS1 and PS2, respectively. Received light amount PS
1 and PS2 can be expressed by the fourth and fifth equations, respectively.

PS1=P1×S/100...(4) PS2=P2×S/100...(5) The ratio of the received light amounts PS1 and PS2 is shown by the sixth equation.

PS1/PS2=P1×S/100/P2×S/100=P1/P2……(6
) As shown in equation 6, the ratio of the received light amounts PS1 and PS2 can be expressed as the ratio of the reference received light amounts P1 and P2. That is, even if objects to be detected have different reflectances, correct values can be obtained by calculating the ratio.

3 is a simplified sectional view of the first light receiving means 12, and FIG. 4 is a simplified sectional view of the second light receiving means 13. The first light receiving means 12 consists of a core 12a and a cladding 12b. Core 12a has a higher refractive index than cladding 12b. Therefore, the first light receiving means 12 can propagate the light incident on the core 12a. The diameter of the core 12a is d1a, and the diameter of the clad 12b is d1. The second light receiving means 13 also includes a core 13a and a cladding 1.
Consisting of 3b. The configuration of the second light receiving means 13 is similar to that of the first light receiving means 13.
It is similar to the light receiving means 12. The diameter of the core 13a is the diameter d2a, and the diameter of the clad 13b is the diameter d2.

FIG. 5 is a simplified diagram showing the path of light of the optical detection device 10 when the detected object 15 moves by a distance Δla. Detected object 15 is the reference mark
Assume that you have moved a distance Δla from the position indicated by GL. A path g1 of the light projected from the light projecting means 11 passes through a point G and reaches a point indicated by the reference mark GM. The directly reflected light at this time is incident on the light receiving end surface of the first light receiving means 12 through the light path g3a. The distance r1b is the distance from the incident position of the light path g3a to the optical axis g2. Since the detected object 15 is separated by a distance Δla from the position indicated by the reference mark GL, the distance r1b is then the distance rl
It will be longer than 1. Therefore, distance r2b is also longer than distance r2. Therefore, the light path g3a deviates from the center of the light-receiving end face of the first light-receiving means 12. Therefore, the amount of light received by the first light receiving means 12 becomes small.

On the other hand, the diffusely reflected light indicated by the light paths g4a and g5a forms an image on a point xa that is a distance x away from the light-receiving end surface of the second light-receiving means 13. point xa
When the diffusely reflected light imagined above reaches the light-receiving end face of the second light-receiving means 13, it forms an image having a width of 2δ. When the width 2δ is smaller than the diameter d2a of the core 13a of the second light receiving means 13, the center of the diffusely reflected light passes through the optical axis g2, so it can be considered that the amount of light received by the second light receiving means 13 remains unchanged. When the brightness of the lens is F, the width 2δ and the diameter d of the core 13a are
The relationship with 2a is shown by the following equation.

d2a≧2δ=2×F (7) Let the amount of light received that enters the first light receiving means 12 be the amount of received light P1, and the amount of light received that enters the second light receiving means 13 as the amount of received light P2. The amount of received light P1 changes depending on the moving distance of the object to be detected 15, and the amount of received light P2 remains unchanged.

Figure 6 shows the moving distance of the detected object 15 and the amount of received light P.
1 is a graph showing the relationship between the ratio of P2 and P2.
As shown in FIG.
Depending on the distance traveled from the position indicated by GL,
The ratio P1/P2 of the amounts of received light P1 and P2 becomes smaller.
By detecting the ratio P1/P2, the moving distance of the detected object 15 can be measured.

FIG. 7 is a block diagram showing the configuration of the optical detection device 10. The light projection system circuit 20 includes an oscillation circuit 21,
It consists of a drive circuit 22 and a light projecting element 23. The oscillation circuit 21 generates a signal to cause the light projecting means 11 to project light. The drive circuit 22 is the oscillation circuit 2
The light projecting element 23 is activated by the signal from 1. The light projecting element 23 generates light. Light projecting element 2
The light generated by 3 is projected through the light projecting means 11.

The oscillation circuit 21 generates a signal and at the same time outputs information indicating that the signal has been generated to the signal processing circuit 24. The light receiving system circuit 25 includes light receiving elements 25a, 25
Consists of b. The light receiving element 25a is the first light receiving means 12
Receives light from The light receiving element 25b receives light from the second light receiving means 13. Light receiving element 25a,
The optical signal received by 25b is sent to the processing system circuit 2.
6 is input. The light receiving circuit 27 includes a light receiving element 25a.
The optical signal from V1 is converted into an electrical signal V1. The logarithmic amplifier circuit 28 receives the electric signal V from the light receiving circuit 27.
Logarithmically amplify 1. The logarithmically amplified electrical signal is converted into an electrical signal lnV1 by the logarithmic amplifier circuit 28, and is output to the subtraction circuit 29.

On the other hand, the optical signal received by the light receiving element 25b is input to the light receiving circuit 30. The light receiving circuit 30 converts the optical signal from the light receiving element 25b into an electrical signal V2. The logarithmic amplifier circuit 31 logarithmically amplifies the electric signal V2 from the light receiving circuit 30, and generates an electric signal lnV2.
Convert it to The electrical signal lnV2 logarithmically amplified by the logarithmic amplifier circuit 31 is output to the subtraction circuit 29. A subtraction circuit 29 calculates the difference between the electrical signals lnV1 and lnV2.

Determining the difference between the logarithmically amplified electrical signals is equivalent to determining the ratio of the electrical signals V1 and V2. The output subtracted by the subtraction circuit 29 is input to the comparison circuit 32. The comparison circuit 32 is
It has a variable resistor 32a. Comparison circuit 32
can detect the presence or absence of the object to be detected 15 by comparing the signal input from the subtraction circuit 29 with the value determined by the variable resistor 32a. Further, the comparison circuit 32
The distance traveled can also be determined. Comparison circuit 32
The results of the comparison are input to the signal processing circuit 24. The signal processing circuit 24 processes the signal from the comparison circuit 32 and outputs the processing result to the output circuit 33. The output circuit 33 displays the presence or absence of the detected object 15 or the moving distance of the detected object 15.

The light projecting means 11, the first light receiving means 12, and the second light receiving means 13 are realized by optical fibers, but by directly connecting the light projecting element and the light receiving element to the lens 14, it is possible to eliminate the use of optical fibers. good.
Also, other devices may be used in place of the optical fiber.

The lens 14 is realized by a self-focusing lens, and directs the light from the light projecting means 11 to the detected object 1.
Any other lens may be used as long as it illuminates the object 15 and receives the direct reflected light and diffuse reflected light from the object 15 to be detected. Also, instead of the self-focusing lens 14, the light is directed to the detected object 15.
It may be realized by a combination of a lens that emits light to the target object, a lens that receives direct reflected light from the detected object 15, a lens that receives diffuse reflected light from the detected object 15, and the like.

Effects As described above, according to the present invention, the first light receiving means receives directly reflected light from the object to be detected, and the second light receiving means receives directly reflected light from the object to be detected.
By receiving the diffusely reflected light from the object to be detected by the light receiving means, the presence or absence of the object to be detected can be detected without causing malfunction even for objects to be detected with different reflectances. . Furthermore, the moving distance of the object to be detected can be measured, and the shape of the optical detection device can be made smaller.

Moreover, in the present invention, the light projecting means, the first light receiving means, and the second light receiving means are arranged on one side of the focusing lens,
By using a condensing lens in common for each of these means, it is possible to downsize the configuration.

Further, according to the present invention, by applying the respective outputs of the first and second light receiving means to the first and second logarithmic circuits and further subtracting the outputs of the first and second logarithmic circuits, direct reflection is achieved. The ratio between the light and the diffusely reflected light can be determined, thereby increasing the detection sensitivity of the object to be detected 15 and preventing malfunctions when the light output of the light projecting means fluctuates during measurement. You will be able to do this.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a detection device 1 showing a prior art;
FIG. 2 shows an optical detection device 10 according to an embodiment of the present invention.
Figure 3 is a simplified diagram showing the path of light in Figure 1.
FIG. 4 is a simplified cross-sectional view of the light receiving means 12, FIG. 4 is a simplified cross-sectional view of the second light receiving means 13, and FIG. FIG. 6 is a simplified diagram showing the path of light; FIG. 6 is a graph showing the relationship between the ratio of the amount of light received by the first light receiving means 12 and the second light receiving means 13 and the moving distance of the object to be detected 15; FIG. 1 is a block diagram showing the configuration of an optical detection device 10. FIG. 10... optical detection device, 11... light projecting means,
12...first light receiving means, 13...second light receiving means,
14... Lens, 15... Object to be detected, 20...
Light emitting system circuit, 25... Light receiving system circuit, 26... Processing system circuit.

Claims (1)

[Claims] 1. A focusing range, provided at a position offset from the optical axis of the focusing lens,
a light projecting means for projecting light onto the focusing lens on one end side in the optical axis direction of the focusing lens; a first light-receiving means for receiving direct reflected light via a converging lens from the object to be detected, which is provided on the other end side in the optical axis direction of the converging lens; a second light-receiving means for receiving diffusely reflected light from an object via a converging lens; a first logarithmic circuit for calculating a logarithmic value of the output of the first light-receiving means; and a second logarithmic circuit for calculating a logarithmic value of the output of the second light-receiving means. and a subtraction circuit that calculates the difference between the outputs of the first logarithm circuit and the second logarithm circuit.