JPS6244375Y2 - - Google Patents

Description

[0001] The present invention relates to a paper sheet detector, and more particularly to a paper sheet detector with improved detection stability.

Conventionally, in a paper sheet detection device, a fluorescent substance attached to a paper sheet is used to detect changes in excitation light that are different from those of the light receiving element of the object to be detected in order to stabilize detection. Detects the object with a light receiving element, controls the amplification degree of the light receiving circuit of the light receiving element of the object to be detected, and changes the threshold level of the binarization circuit of the light receiving circuit according to the method of stabilizing the output and the change in excitation light. A method has been devised. Since these were not calibrated in a loop that took into account changes in the excitation light and light-receiving element, as well as the effects of dust, etc., detection included unstable elements.

The present invention was developed based on the above-mentioned circumstances, and an object of the present invention is to provide a paper sheet detection device that enables calibration of the entire detection device with a relatively simple configuration and enables stable detection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an illustrated embodiment in which the present invention is applied to a detection device for a letter affixed with a stamp containing a fluorescent substance.

In FIG. 1, reference numeral 1 denotes a letter to which a stamp 2 containing a fluorescent substance is affixed, and this letter 1 is conveyed in the direction of the arrow in the figure by a conveyor belt (not shown). The stamp 2 is irradiated with ultraviolet light from an excitation light source 4 comprising an ultraviolet lamp, so that the fluorescent substance of the stamp 2 is excited to emit light. The excitation light from the stamp 2 passes through the detection window 3 which also serves as a dust-proof glass, is focused on the slit plate 8 by the imaging lens 5, and is filtered through the filter 9.
The light is guided to the light receiver 10 via. The slit plate 8 has slits made to match the size of the stamp, and the filter 9 is a glass filter with a color matching the color of the fluorescent material contained in the stamp 2. Further, 7 is a light shielding part that prevents external light from entering the light receiver 10.

On the other hand, a fluorescent tube 6 as a reference body is provided at a position facing the light receiver 10 across the conveyance path. Fluorescent tube 6
emits excitation light, and the excitation light enters the light receiver 10. Furthermore, 15 and 16 are detectors each consisting of a lamp and a light receiving element,
This detects whether the letter 1, which is an object to be detected, is passing through the optical system section.

Next, the signal processing circuit shown in FIG. 2 will be described. The output signal photoelectrically converted by the photoreceiver 10 is amplified by the amplifier 11 and then applied to the quantization circuit 14 and also to the gate circuit 12.
This gate circuit 12 is a gate control circuit 1 which will be described later.
The amplifier 11 is switched by the output of the amplifier 11.
The output signal is selectively supplied to the signal holding circuit 13. Thus, the output signal of the signal holding circuit 13 is applied to the quantization circuit 14 and used as a quantization level signal of the amplifier 11, that is, a slice level.

On the other hand, the output signal of the light receiving element 16 is amplified by an amplifier 17 and applied to a gate control circuit 18, which applies a gate inhibit signal to the gate circuit 12 while the letter 1 is passing through the optical system portion, and also supplies a detection enable signal to the quantization circuit 14 while the letter is passing through.

Next, to explain the operation of this circuit, when the letter 1 is not passing through the optical system section, the ultraviolet rays from the excitation light source 4 irradiate the fluorescent tube 6, so the excitation light from the fluorescent tube 6 passes through the detection window 3, imaging lens 5,
The light enters the light receiver 10 via the slit plate 8 and filter 9, respectively. The signal photoelectrically converted by the photodetector 10 is amplified by the amplifier 11 and applied to the quantization circuit 14 and also to the gate circuit 12. Here, since the detection permission signal is not output from the gate control circuit 18, the quantization circuit 14 does not output an output, and since the gate prohibition signal is not output, the output signal of the amplifier 11 is applied to the signal holding circuit 13. Become. The signal holding circuit 13 holds the signal from the amplifier 11, divides the signal, and outputs a quantization level signal to the quantization circuit 14. When the letter 1 is conveyed in this state, the light receiving element 16 detects that the letter 1 is passing, and the gate control circuit 18 outputs a gate prohibition signal and a detection permission signal to the gate circuit 12 and the quantization circuit 14. do. On the other hand, since the ultraviolet rays from the excitation light source 4 are irradiated onto the stamp 2, the fluorescent substance contained in the stamp 2 is excited and emitted light. The light enters the light receiver 10 via the light beam. The output signal photoelectrically converted by the photoreceiver 10 is applied to the quantization circuit 14 via the amplifier 11, and is quantized using the output signal of the signal holding circuit 13, which was held before the letter arrived, as the quantization level. The presence or absence of stamps is detected. At this time, since the gate inhibit signal is applied to the gate circuit 12, the output signal of the amplifier 11 is not applied to the signal holding circuit 13, and the signal holding circuit 13 continues to hold the value before the letter arrives. Further, when the letter 1 has passed, the signal is held in the signal holding circuit 13 by the excitation light from the fluorescent tube 6 serving as a reference body, as described above.

As described above, according to this embodiment, the excitation light of the reference body is measured and the quantization level is determined based on this reference, so the attenuation changes due to deterioration of the light source, receiver, amplifier, etc. Even so, stable detection can be performed.

In the above-mentioned embodiment, the quantization level of the quantization circuit was controlled by the light output from the reference body, but the same effect can be achieved even if the amplification degree of the amplifier is controlled as shown in FIG. Effects can be obtained.

That is, the photoelectrically converted output signal of the photoreceiver 10 is applied to an amplifier 11 whose amplification width is variable, and the amplified signal is applied to a quantization circuit 14 and a gate circuit 12. The output of the gate circuit 12 is compared with the reference level from the reference level generator 21 in the comparator circuit 22, and if there is a difference, the difference signal is applied to the signal holding circuit 23, which holds the signal. The amplification degree of the amplifier 11 is controlled by the signal from the circuit 23, and the received light output from the reference body is always output to the reference level generator 21.
The degree of amplification is controlled so that it is equal to the reference level from . Note that 18 is a gate control circuit similar to that of the previous embodiment.

Further, in this embodiment, by associating the reference level from the reference level generator with the quantization level of the quantization circuit, it is possible to compensate for changes in the characteristics of the quantization circuit.

In addition, in these examples, only the detection of fluorescent substances contained in stamps was explained, but the present invention is not limited to this, and phosphorescence or visible light may be used, and the detection object may also be paper sheets. It goes without saying that the present invention can be applied to other applications and various modifications can be made without departing from the gist of the present invention.

As explained above, according to the present invention, the reference body is placed opposite the light receiver, and the signal processing circuit is controlled by the light output from the reference body, so that the light source, the light receiver, the amplifier It is possible to provide a paper sheet detection device that can always perform stable detection even if the sensitivity of the entire device including the device changes.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention. Fig. 1 is a plan view showing the arrangement of the optical system, Fig. 2 is a block diagram showing the signal processing circuit, and Fig. 3 shows another embodiment of the signal processing circuit. FIG. 1...Letter, 2...Stamp, 4...Light source, 6...
Reference body (fluorescent tube), 10... Light receiver, 11
...Amplifier, 14...Quantization circuit, 13, 23...
...Signal holding circuit, 12...Gate circuit, 18...
Gate control circuit.

Claims (1)

[Claims for Utility Model Registration] (1) A conveyance path for conveying paper sheets, a light source that irradiates the paper sheets conveyed on this conveyance path, and light emitted from this light source and reflected by the paper sheets. a light receiver that receives light; a reference body that faces the light receiver across the conveyance path and is disposed at a position to be irradiated with the light of the light source; a holding means for holding the obtained reference signal; a signal processing circuit for inputting and processing the reference signal held by the holding means and the light signal reflected by the paper sheet; and a signal processing circuit provided in the conveyance path. a detector for detecting that paper sheets have been conveyed to the installation location of the light source and the light receiver; and a switching means for selectively supplying an output signal of the light receiver to the holding means in response to detection by the detector. A paper sheet detection device comprising: (2) The light source is constituted by an ultraviolet generating lamp, and a fluorescent substance is arranged as a reference body, so that the signal processing circuit detects the fluorescent substance applied to the paper sheet. Claim 1 Detection device for paper sheets as described in Section 1. (3) The paper sheet detection device according to claim 1 or 2 of the utility model registration claim, wherein the signal processing circuit is configured to control the degree of amplification using the reference signal. (4) The paper sheet detection device according to claim 1 or 2, wherein the signal processing circuit is configured to control the quantization level using the reference signal.