JPH04240505A - Device for measuring dimension of transmission type - Google Patents

Abstract

PURPOSE:To enable highly-precise measurement of a dimension without being affected by a change in the quantity of sensed light when the change occurs due to deterioration of a light projecting part or a light sensing part, a change in characteristics caused by a change in temperature or the like, stain of a lens or others. CONSTITUTION:When an object 12 comes onto this side of a slit 10, it is detected by an auxiliary light-sensing element 8 and a sensed-light voltage VA of the whole quantity of sensed light before the slit 10 is shaded is stored and held in a hold circuit 16. When the object 12 reaches the slit 10, the quantity of the sensed light shaded by the object 12 is measured and a voltage VB of the sensed light is inputted to a division part 14. In the division part 14, a ratio between this sensed-light voltage VB and the sensed-light voltage VA of the whole quantity of the sensed light held in the hold circuit 16 is computed. The dimension of the object 12 is determined on the basis of the value (VB/VA) of this ratio.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a transmission type that measures the dimensions of an object by emitting parallel light from a light projecting section onto an object, and detecting the amount of received light that changes when the object blocks it, using a light receiving section. It relates to a dimension measuring device.

0002

2. Description of the Related Art FIG. 5 shows the configuration of a conventional transmission type dimension measuring device 51. The dimension measuring device 51 includes a light projecting section 52 and a light receiving section 53, which are arranged facing each other. Inside the light projecting section 52, a light emitting source 54 such as a semiconductor laser element is provided.
A lens 55 is built in to convert the light emitted from the light emitting source 54 into parallel light. However, the drive circuit 5
When the light emitting source 54 is driven by 6, a collimated light beam α is emitted from the light projecting section 52. In addition, the light receiving section 53
A slit 57 is opened in the front surface of the slit 57, and inside there is a light receiving element 58 such as a photodiode (PD) for receiving the light incident from the slit 57 and detecting the amount of received light. A lens 59 for condensing light is built in, a detection signal is output from the light receiving section 53 to a light receiving circuit 60, and a light receiving voltage V is output from the light receiving circuit 60.

FIG. 6 shows the relationship between the light receiving voltage V output from the light receiving circuit 60 and the amount of light shielding (or the external dimensions of the object 61). The light receiving voltage V decreases linearly as the external dimensions of the object 61 increase and the amount of light shielding increases. Therefore, based on the light receiving voltage output from the light receiving circuit 60, the amount of light shielding (outer dimensions) is determined.

[0004]The projected light beam α emitted from the light projecting section 52 is irradiated onto an area including the slit 57 of the light receiving section 53, as shown in FIG. At this time, when an opaque or translucent object 61 being conveyed by a conveyor or the like passes between the light projecting section 52 and the light receiving section 53, a portion of the projected light beam α emitted from the light projecting section 52 is blocked by the object 61, and the amount of light received by the light receiving section 53 (light receiving voltage V)
changes, so the dimensions of the object can be found.

[0005]

[Problems to be Solved by the Invention] However, with conventional dimension measuring devices, the dimensions of an object are determined based on changes in the light-receiving voltage at the light-receiving section. A problem was occurring.

■ Light emitting sources such as semiconductor laser elements built into the light emitting unit have problems such as fluctuations in the emitted light power due to temperature and attenuation of the emitted light power due to element deterioration. Even in this case, the amount of light received by the light receiving section fluctuates.

[0007] The light-receiving element such as a light-emitting diode built into the light-receiving section changes light-current (o-i) depending on the temperature.
Since the conversion efficiency varies, the light receiving voltage output from the light receiving circuit changes even if the amount of light received is the same.

[0008]Furthermore, even if there is no change in the light emitting power of the light emitting source or the efficiency of the light receiving element, the amount of light received may change due to dirt on the lens or the like.

The present invention has been made in view of the problems of the prior art described above, and its purpose is to improve the power of the light emitting part and the conversion of the light receiving part in a transmission type dimension measuring device. The objective is to prevent deterioration in dimensional measurement accuracy and erroneous detection due to factors such as fluctuations in efficiency or dirt on the lens.

0010

[Means for Solving the Problems] The transmission type dimension measuring device of the present invention irradiates an object with a light beam from a light projector, and detects the amount of received light that changes when the object is blocked by the light receiver. It is a device for measuring the dimensions of an object, and includes a means for determining when an object is present in the detection area and when it is not, and a means for determining the total amount of light received within the detection area and the amount of light shielded by the object. It is characterized by comprising means for detecting the amount of light received by the light receiving section and calculating the dimensions of the object from the ratio of the amount of light received blocked by the object to the total amount of light received.

[0011] Furthermore, in order to determine when an object is present in the detection area and when it is not, for example, the total amount of received light within the detection area and the amount of received light blocked by the object are measured. It is preferable that an auxiliary light-receiving element for obtaining a timing signal is provided in the light-receiving section.

0012

[Operation] In the present invention, the total amount of received light within the detection area and the amount of received light blocked by the object are detected by the light receiving section, and the ratio of the amount of received light blocked by the object to the total amount of received light, that is, the projected beam The dimensions of the object are calculated from the ratio of the amount of shielding.

Therefore, even if there are changes in the characteristics of the light emitting/receiving section, such as fluctuations in the light emitting power due to the temperature of the light emitting section or fluctuations in light-to-current conversion efficiency due to the temperature of the light receiving section, the amount of received light blocked by the object is It is corrected by the total amount of light received when the projected beam is not blocked, and the dimensions of the object can be measured or determined with high precision, and erroneous detections are also prevented.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 2 shows a schematic configuration diagram of an embodiment of the present invention. The light projecting unit 1 includes a semiconductor laser element and a light emitting diode (L
ED), a light emitting source 2 such as a lamp, and a collimating lens 3
The light emitting source 2 is driven by a drive circuit 4 to emit light, and the emitted light is converted into a collimated projection beam α through a lens 3 and emitted toward a light receiving unit 5. .

The light receiving section 5 includes a photodiode (PD).
A light receiving element 6 for detecting the amount of light received by a PD array, a charge-coupled device (CCD), etc., a lens 7 for focusing incident light on the light receiving element 6, and a sensor for determining whether an object exists within the detection area. A vertically long slit 10 is opened at a portion of the light receiving unit case 9 facing the light receiving element 6, and the light receiving unit case 9 has an auxiliary light receiving element 8 built therein.
A relatively small circular hole 11 is opened at a location facing the auxiliary light-receiving element 8, and the length of the opening in the longitudinal direction of the slit 10 is the detection range (detection area) of the object size. . Moreover, as shown in FIG. 1, the through hole 11 is provided at approximately the same height as the lower end of the slit 10, and on the side from which the object 12 moves.

The projected beam α emitted from the projecting section 1 is irradiated onto a region (shaded region in FIG. 1) including the slit 10 and the through hole 11 of the light receiving section 5, and the slit The shielding state of the light passing through the hole 10 is detected by the light receiving element 6, and the shielding state of the light passing through the through hole 11 is detected by the auxiliary light receiving element 8.

Further, as shown in FIG. 2, the output of the light receiving element 6 is connected to a light receiving circuit 13, and the light receiving circuit 13 outputs a light receiving voltage V corresponding to the amount of light received. Furthermore, the output of the light receiving circuit 13 is directly connected to the divider 14 and is also connected to the hold circuit 1 through an analog switch 15.
6. An auxiliary light receiving element 8 is connected to the control terminal of this analog switch 15 via an amplifier 17, and when the auxiliary light receiving element 8 is detecting the light passing through the through hole 11, the analog switch 15 is turned off.
When the light entering the through hole 11 is blocked, the analog switch 15 is turned on, and the held data (light receiving voltage V) in the hold circuit 16 is updated in synchronization with the rising operation of the analog switch 15. Further, the value of the light receiving voltage held by the hold circuit 16 is output to the dividing unit 14, and the dividing unit 14 holds the light receiving voltage VB directly input from the light receiving circuit 13 in the hold circuit 16. The value (VB/VA) divided by the received light voltage VA is calculated and output.

Next, the operation of the dimension measuring apparatus of the present invention will be explained according to the time chart shown in FIG. In Figure 3, (
(a) shows the on/off output of the auxiliary light receiving element 8, (b)
indicates the on/off state of the analog switch 15, and (c
) shows the data update operation of the hold circuit 16, and (d)
(e) shows the timing of measuring the amount of light received by the object 12 by the light receiving element 6, and (e) shows the calculation and output operation of the dividing unit 14.

As shown in FIG. 1, if an object 12 whose dimensions are to be measured is now flowing onto the belt conveyor, the through hole 1 is inserted just before the object 12 reaches the detection area (slit position).
1 is blocked by the object 12, and the output of the auxiliary light receiving element 8 changes from off to on at time T1 [FIG. 3(a)], and at the same time, the analog switch 15 turns on [FIG. 3(b)]. Furthermore, data in the hold circuit 16 is updated in synchronization with the rising operation of the analog switch 15, and the light reception voltage VA indicating the total amount of light received by the light receiving element 6 (the amount of light received without being blocked by an object) is updated in the hold circuit 16. It is retained [Figure 3 (
c)]. After the auxiliary light receiving element 8 and the analog switch 15 are turned from on to off, the object 12 reaches the position of the slit 10 at time T2, and a portion of the projected beam α is blocked depending on the size of the object 12. The amount of light received that is blocked by the object 12 is measured [FIG. 3(d)], and the amount of light received by the object 12 is measured [FIG. 3(d)].
4. Light receiving voltage VB for the amount of light received blocked by the object 12
is output, the ratio of the received light amount voltage VB blocked by the object to the total received light amount voltage VA is calculated by the dividing unit 14, and the ratio is calculated at time T.
3, when the object 12 passes through the slit 10, an analog voltage (VB/VA) according to this ratio is output [Fig.
(e)]. Here, since the detection range matches the set slit length, the dimensions of the object are measured based on the ratio of the calculation results. Then, each time the object to be measured 12 flows, the total received light amount voltage VA of the hold circuit 16 is updated, and the dimension measurement is repeated. Note that in FIG. 3, d is the distance between the objects 12 to be measured.

In the above embodiment, the object before passing through the slit position is detected by the auxiliary light receiving element, and the total received light amount voltage is stored in the hold circuit. good. In other words, the through hole and the auxiliary light receiving element are provided in the direction in which the object passes relative to the slit, the light receiving voltage when the object passes through the slit position is stored in a hold circuit, and the auxiliary light receiving element is used to detect the object at the slit position. The light-receiving element detects the light-receiving voltage of the total amount of light received, and the dividing section calculates the ratio of the light-receiving voltage stored in the hold circuit and the light-receiving voltage of the total amount of light received. good.

[0021]

According to the present invention, the dimensions of the object are calculated based on the ratio of the amount of light blocked by the light emitting beam, so even if the amount of light received changes due to changes in the characteristics of the light emitting part and the light receiving part, the received light remains constant. It is possible to measure or determine the dimensions of an object with high accuracy without being affected by variations in quantity, and it is also possible to prevent erroneous detection by the dimension measuring device.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing a light receiving section in an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of the embodiment same as above.

3A, 3B, 3C, 3D, and 3E are time charts showing the operations of an auxiliary light receiving element, an analog switch, a hold circuit, a light receiving element, and a dividing section, respectively.

FIG. 4 is a partially cutaway perspective view of a light receiving section in a conventional example.

FIG. 5 is a schematic configuration diagram of a conventional example.

FIG. 6 is a diagram showing the relationship between the amount of light blocked by an object and the received light voltage.

[Explanation of symbols]

1 Light projecting section 5 Light receiving part 6 Photo receiving element 8 Auxiliary light receiving element 10 slit 11 Through hole 12 Object 14 Division part 15 Analog switch 16 Hold circuit

Claims (2)

[Claims] 1. A device that measures the dimensions of an object by emitting a light beam from a light projecting section onto an object and detecting the amount of received light that changes due to being blocked by the object using a light receiving section, A means for determining when an object exists and when an object does not exist within the detection area, and a light receiving unit detects the total amount of received light within the detection area and the amount of received light that is blocked by the object, and detects the amount of received light that is blocked by the object. A transmission type dimension measuring device comprising means for calculating the dimensions of an object from the ratio of the amount of received light to the total amount of received light. 2. The transmission type according to claim 1, wherein the light receiving section is provided with an auxiliary light receiving element for obtaining a timing signal for measuring the total amount of light received within the detection area and the amount of light received that is blocked by an object. Dimension measuring device.