JPS6258446B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal detection device that detects a member to be detected that interrupts an optical axis set in a space.

Generally, an automatic control device detects various physical quantities and automatically controls the entire controlled device. Photointerrupters used in such automatic control devices have the feature of being able to detect physical quantities without contact, and play an important role as input circuits for various control devices. Conventional photo interrupter 1
As shown in FIG. 1, a light emitting element 2 and a light receiving element 3 are connected via an optical path l arranged in a set space 4, and the presence or absence of a detected member (not shown) that interrupts this optical path l is determined by changing the light amount. It receives this as a signal and outputs it to the input circuit of the control device. The light receiving element 3 of this photointerrupter 1 is fixed to a support member 6 facing the space 4 and protruding from the base 5, and receives light incident from the space 4 side at all angles. Therefore, in addition to the light from the light emitting element 2 passing through the optical path l, the light receiving element 3 is likely to receive disturbance light passing through the space 4 from the outside, and the noise level ( It exhibited poor characteristics such as a high S/N ratio (hereinafter simply referred to as S/N).

Furthermore, if the photo interrupter 1 is installed in a controlled device that generates a lot of vibration, electrical noise may be generated at the connection part of the connection wiring between the input circuit side and the light emitting element 2 and the light receiving element 3 in the photo interrupter. It has the disadvantage of deteriorating /N characteristics. Furthermore, since the light-emitting element 2 and the light-receiving element 3 are separate and independent from the main body of the control device, it is difficult to integrate the input circuits of the individual photo interrupters 1 for signal processing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal detection device that can prevent noise caused by ambient light and that can easily adjust the optical axis.

In this invention, a pair of support members are integrally provided on a base and protrude through a space, one support member is formed with a light transmission end receiving groove for holding a light transmission fiber, and the other support member is formed with a light transmission end receiving groove for holding a light transmission fiber. A light-receiving end receiving groove is formed, and the respective ends of the light-transmitting fiber and the light-receiving fiber are held in these grooves using a fixing member so that they align with the set optical axis, and the light passing through the set optical axis in the space is The sensor is configured to detect a change in the amount of light as a signal due to a change in the amount of light caused by the detected member.

According to this invention, the light transmitted by the light receiving fiber can be detected as a signal, and the light receiving element that receives this can generate an output signal. Therefore, the light that is repeatedly totally reflected within the light-receiving fiber and transmitted to the light-receiving element is only the light that is incident at an angle of incidence that is within the acceptance angle corresponding to the critical angle of the light-receiving fiber. Ambient light is removed. Furthermore, the light transmitting end can be held between the light transmitting end receiving groove and the fixing member, and the light receiving end can be held between the light receiving end receiving groove and the fixing member. Therefore, there is an advantage that fine adjustment to align the light transmitting end and the light receiving end with the set optical axis can be performed with these ends being held.

The present invention will be described below with reference to the accompanying drawings.

FIG. 2 shows a signal detection device 7 as an embodiment of the present invention, which is an input circuit 8 of a synchronization signal generator installed in a copying machine (not shown).
It is connected to the. This signal detection device 7 has a base 10 made of a light-shielding rigid material, here a plastic material, facing the passage R of the detected member 9.
The base 10 is integrally formed therewith, and the space 1
a pair of support members 12 facing each other via 1;
13 stands out. A pair of support members 12, 13
are a light receiving fiber facing surface 14 and a light transmitting fiber facing surface 1 whose sides facing the space 11 are parallel to each other.
5 is formed. Further, the tip end surface 1 of the support member 12
21 is formed with a light transmitting end receiving groove 16 which is long in the direction of the set optical axis l1 and has a V-shaped bottom surface 161, and a light receiving end receiving groove 16 having a similar shape is formed in the protruding end surface 131 of the support member 13. A groove 17 is formed. Bottom surface 16
The light transmitting end 181 of the light transmitting fiber 18 is placed on the light transmitting fiber 18 , and this light transmitting end is spaced between the bottom surface 161 and the lower end of the fixing member 19 fitted in the light transmitting end receiving groove 16 by a pressing surface 191 at the lower end. be held between. Similarly, the light receiving end 211 of the light receiving fiber 21 is held between the bottom surface 171 of the light receiving groove 17 and the pressing surface 201 of the fixing member 20 fitted into the receiving groove. Both fixing members 19, 2
0 accommodates a plurality of locking pieces 22 that fit into fixing holes 162 and 172 recessed in the inner walls of both receiving grooves 16 and 17. Each locking piece 22 is a fixed member 19, 2
0 is elastically pressed to the outside by a compression spring 23 disposed inside the fixing hole 1.
62, 172, it protrudes and fixes each fixing member 19, 20 to each receiving groove 16, 17. At this time, the light transmitting end 181 held between the fixed member 19 and the light receiving end receiving groove 16 and the light receiving end 211 held between the fixed member 20 and the light receiving end receiving groove 17 are set together. It is supported on the optical axis l1. That is, as shown in FIG. 3, when the light transmitting end 181 is sandwiched between the V-shaped bottom surface 161 and the pressing surface 191 of the fixing member 19, the center O of the light transmitting end 181 is aligned with the set optical axis l1. The positional relationship between the bottom surface 161 and the pressing surface 191 is set so that they match. One support member 12 has a light transmitting fiber support curved surface 1 on the side opposite to the space 11.
Similarly, the other support member 13 has a light-receiving fiber support curved surface 132 formed to bulge on the side opposite to the space 11. As shown in FIG. 4, the light transmitting fiber supporting curved surface 122 has the light transmitting fiber 18 extending from the light transmitting end receiving groove 16 curved in a direction substantially perpendicular to the set optical axis l1 (downward in the figure). To support. The light transmitting fiber 18 is further connected to a light emitting element 2 which is directly connected to the input circuit 8 through a through hole 24 formed in the base 10.
5. Similarly, the light-receiving fiber 21 extends from the light-receiving end receiving groove 17, has a curved portion 212 supported by the light-receiving fiber support curved surface 132, and passes through the through hole 25 on the base 10 to the light-receiving element 26 directly connected to the input circuit 8. optically coupled. In addition,
The curved portion 182 of the light transmitting fiber 18 (also the curved portion 212 of the light receiving fiber) supported by the light transmitting fiber support curved surface 122 is curved with a bending radius r. The value of this bending radius r is regulated by the diameter d of the light transmitting fiber 18. This is because if the bending radius r becomes too small, the radiation loss due to mode conversion of the light transmitted by total internal reflection within the light transmitting fiber 18 will increase, and the transmittance retention rate of the light transmitting fiber 18 will decrease. This is because the transmission loss of the optical fiber 18 increases. Therefore, when bending a commonly used commercially available plastic fiber, it is sufficient to use it within the range r>5d to 10d (1), and both the light transmitting fiber support curved surface 122 and the light receiving fiber support curved surface 132 are curved.
It is formed with a bending radius r that satisfies equation (1). FIG. 5 shows the bending radius-transmittance retention curve of a commercially available plastic fiber. In FIG. 5, line a shows the case where the optical fiber diameter is 0.25 [mm], line b the same 0.5 [mm], and line c the same 1.0 [mm].

The above-mentioned pair of support members 12 and 13 are arranged so that the light transmitting end face 183 of the light transmitting fiber 18 and the light receiving end face 213 of the light receiving fiber 21 are mutually set on the optical axis l1 in the space 1.
1 to face each other. The set optical axis l1 in the space 11 intersects with the path R of the detected member,
This detected member 9 blocks the set optical axis l1 during operation.

The signal detection device 7 having such a configuration operates as follows.

Light emitting element 2 driven by a well-known constant current circuit
The light from 5 is transmitted to the light transmitting end 1 by the light transmitting fiber 18.
81 and set optical axis l1 from the light transmitting surface 183.
is irradiated along the When this light passes through the space 11, it is intermittently changed by the member to be detected 9, and enters the light-receiving end face 213 of the light-receiving fiber in a state where the amount of light is changed. This incident light is transmitted to the other end side by the light receiving fiber 21 and is received by the light receiving element 26. That is, the light guided by the light receiving fiber 21 is received by the light receiving element 26 as a light amount change signal. This light receiving element 26 emits an output signal I corresponding to this light amount change signal to the input circuit 8.

The signal detection device 7 shown in FIG.
3 to support it on the set optical axis l1. In this case, the light transmitting end 181 is held between the light sending fiber receiving groove 16 and the fixing member 19, and the light receiving end 211 is only being held between the light receiving fiber receiving groove 21 and the fixing member 20, thereby almost setting the optical axis l1. Optical axis alignment is performed. However, if further fine adjustment is required, the signal detecting device 7 has the advantage that the light transmitting end 181 or the light receiving end 211, which are held in place, can be easily moved and adjusted manually.
Moreover, in some cases, after the fine adjustment is completed, adhesive may be poured into the internal gaps of both receiving grooves 16 and 21.
If the light transmitting end 181 and the light receiving end 211, which have been completely aligned with the optical axis, are fixed, there is an advantage that the optical axis can be prevented from shifting later. Note that the same effect can be obtained even if the adhesive is applied to the fixing members 19, 20, etc. in advance. Furthermore, the signal detection device 7 shown in FIG. 2 has a light transmitting fiber 18 and a light receiving fiber 21 pulled out to the lower side of the base 10, which can be handled in the same direction as the electrical wiring of a conventional photointerrupter. It has the advantage of being easy. Furthermore, in this case, the bending radius r of each curved portion 182, 212 is regulated to an appropriate value by the light transmitting fiber supporting curved surface 122 and the light receiving fiber supporting curved surface 132, so that the transmittance retention rate of both optical fibers does not decrease. . Furthermore, the characteristics of the optical fiber, that is, the exit angle and the acceptance angle at the light transmitting end face 183 and the light receiving end face 213 do not exceed the maximum value θ corresponding to the critical angle of the optical fiber, and the light transmitting end face 183 and the light receiving end face 213 do not exceed the maximum value θ corresponding to the critical angle of the optical fiber. Ambient light entering and exiting is removed (see Figure 4). For this reason, the S/N characteristics of the signal detection device 7 can be kept good. Furthermore, since the signal detection device 7 and the input circuit 8 can be placed at desired positions apart from each other and are electrically isolated, generation of electrical noise on the signal detection device 7 side can be prevented.

The fixing member 19 or 20 shown in FIG. 2 presses each optical fiber with its lower pressing surfaces 191 and 201, but as shown in FIG. It may be attached to the lower part of the fixing member 19. In this case, the light transmitting end 181 of the light transmitting fiber can be elastically and reliably clamped, and there is an advantage that optical axis deviation can be prevented without filling the gap in the light transmitting end receiving groove 16 with adhesive. .

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional photo interrupter.
Fig. 2 is a perspective view of a signal detection device as an embodiment of the present invention, Fig. 3 is an enlarged view of main parts of the same signal detection device, Fig. 4 is a side view of the same signal detection device, and Fig. 5
The figure is an optical fiber bending radius-transmittance retention diagram.
FIG. 6 is a perspective view of a main part of a signal detection device as another embodiment of the present invention. 7...Signal detection device, 9...Member to be detected, 10
... base, 11 ... space, 12, 13 ... support member, 122 ... light transmission fiber support curved surface, 132 ...
... Receiving fiber support curved surface, 16... Light transmitting end receiving groove,
161...Low surface, 17...Light receiving end receiving groove, 171...
...Low surface, 18...Light sending fiber, 181... Light sending end, 19, 20... Fixing member, 21... Light receiving fiber, 211... Light receiving end, l1... Setting optical axis.

Claims (1)

[Claims] 1. A base integrally protruding from a pair of support members arranged in parallel with each other with a space in between, and a light transmitting fiber that receives light from a light source and transmits the light from a light transmitting end. and,
It has a light receiving fiber that receives the light from the light transmitting fiber at its light receiving end and guides it to the light receiving element. A receiving groove is formed at each end, and the light transmitting end is held between the bottom surface of the light transmitting end receiving groove and a fixing member fitted in the light transmitting end receiving groove so as to be aligned with the set optical axis. The light receiving end is held in alignment with the set optical axis by the bottom surface of the light receiving end receiving groove and the fixing member fitted into the light receiving end receiving groove, and the light from the light transmitting fiber is directed to the detected member in space. A signal detection device configured to detect a change in the amount of light as a signal. 2. A light transmitting fiber supporting curved surface is formed on one of the supporting members to curve and support the light transmitting fiber extending from the light transmitting end receiving groove, and a light receiving fiber extending from the light receiving end receiving groove is formed on the other supporting member. 2. The signal detection device according to claim 1, further comprising a curved support surface for supporting the light-receiving fiber.