JPS61283849A - Optical characteristic measuring apparatus for paper - Google Patents

Abstract

PURPOSE:To extend the life of a light source eliminating the need for initializing operation prior to measurement, by extinguishing the light source during the transition period when a measuring plate is changed over to read out the electric charge accumulated at a detection element sequentially during the period. CONSTITUTION:A light source 4 is turned ON by a lamp trigger signal during the measuring period when a white plate and a black plate, two equally divided parts of a disc 12, position on the back of a paper 3. Consequently, a photodiode composing a linear array sensor 8 provided on the focal plane of a spectroscope 7 is exposed by the reflected light from the paper 3 for a fixed period of time. A detection signal from the linear array sensor 8 is processed by a signal processing section 9 and when the light source 4 is put out, the reading of a signal is started on timing to the falling of a lamp trigger signal. Thus, during the transition period, as the electric charge accumulated at a detection element during the measuring period is held as intact with the irradiation with no light, thereby enabling accurate reading of signals. This also eliminates the need for separate initializing operation at the subsequent measurement.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to optical properties such as paper color, brightness, whiteness, etc.
More specifically, regarding a device for online measurement of The present invention relates to an apparatus for forming an image of a spectroscopic spectrum on a linear array sensor having a plurality of charge storage type photodetecting elements, and measuring optical characteristics of the paper based on detection signals from the linear array sensor.

<Prior art> Methods for experimentally measuring the color, whiteness, and opacity of paper are based on the Japanese Industrial Standards, JIS Z 8728, and JIS
P 8123 and JIS P 8138, respectively, and the methods for measuring these optical properties online are basically the same as the JIS methods.

Conventionally, an apparatus shown in FIG. 3 has been proposed as an apparatus for measuring optical properties of paper online.

In the figure, 1 is the upper detection section, and inside the housing 2 is a light back surface that irradiates light onto the surface of a sheet of paper 3 at an incident angle of 45 degrees! 4, a rotating hictor 5 that intermittently blocks the irradiated light, a lens 6 that collects the vertically reflected light from the paper 3, a spectroscope 7 that separates the collected reflected light into spectra, and a spectroscope 7. The linear array sensor 8 includes a linear array sensor 8 that is installed on the focal plane of the linear array sensor 8 and has a plurality of photodetecting elements arranged in the wavelength distribution direction of the spectrum, and a signal processing section 9 that processes detection signals from the linear array sensor 8.

10 is a lower detection section placed on the back side of paper 3;
Inside 1, a disk as shown in Fig. 4 is divided into two, and a black plate 1 is placed.
It includes a disk 12 provided with a 2a1 white plate 12b and a motor 13 that rotates this disk.

Although not shown in this figure, the upper detecting section 1 and the lower detecting section 10 are installed integrally on a frame, sandwich the paper 3, and are driven back and forth in the width direction thereof.

With this configuration, a black plate with a reflectance of 0.5% or less is used as the black plate 12a, a white plate with a reflectance of about 89% is used as the white plate 12b, and these are attached to the back side of the paper 3 at regular intervals. When switched and positioned, the reflected light from the paper 3 detected when the black plate 12a is backed and the reflected light detected when the white plate 12b is backed are detected according to the method specified in JIS P 8138. The opacity of the paper 3 can be measured from the ratio. .

Incidentally, in such a #& position, an MO8 type image sensor as shown in FIG. 5, for example, is used as the linear array sensor 8. This sensor connects MOS transistors 81 to 3n for switching to photodiodes D1 to Dn arranged in an array, respectively, and sequentially turns on these transistors 81 to 3n by a scanning pulse from a scanning circuit SC. Diode 01~D
The configuration is such that n is reverse biased by a power source E.

In the reverse bias state, the photodiodes D1 to Qn act as capacitors and are charged by l1iE. By the time the next scanning pulse is applied, when light enters the photodiodes D1 to Qn, a photovoltaic force is generated, which acts to cancel the charge ff1flt2 pressure of the photodiode, and the charge accumulated in the photodiode is discharge.

When the next scanning pulse is applied, each phototransistor is charged according to the amount of discharge, and the charging current at that time is taken out as a detection signal.

The photodiodes 01 to ()n are arranged in, for example, 10241i in the wavelength distribution direction of the spectrum, and when reflected light is applied to these elements, reading is performed sequentially from the 1flth element to the 1024th element. Figure 6 shows black board 1
2a and the white plate 12b switching state 1g (Figure (a)), and the readout state of the photodiodes D1 to [)n (
FIG.

The readout from the photodiodes D1-Dn begins when the paper 3 is backed by the black plate 12a and the white plate 12b (no readout takes place during the transition period when these measurement plates are switched).

Note that the light source 4 remains lit during this time.

The time t1 required for reading from the 119th photodiode to the 10241st photodiode is approximately 5Q.
ms. This time is the linear array sensor 8
It is determined according to the response speed of the analog circuit connected to the subsequent stage, and cannot be made any shorter.

The photovoltaic forces of the photodiodes D1 to [)n depend on the opening during irradiation and the amount of reflected light from the paper 3, and this time difference of 50 m5 is due to the difference between the 11th photodiode and the 10241st photodiode.
This appears as a difference in the opening of the eye's photodiode during irradiation, and becomes a cause of error.

Furthermore, the light 1 [i4 is lit even during the transition period when the black board 12a and the white board 12b are switched, and for example,
Even if the measurement with the white plate 12b is interrupted and -H initialization is performed, light still enters the photodiodes D1 to [)n after this, so this remains as an error factor. Therefore, it was necessary to perform an initialization operation again before the next measurement using the black plate 12a.

Furthermore, although a direct current lighting type lamp such as a halogen lamp is used as the light source 4, it is wasteful to leave it on during the transition period, and it is not preferable from the viewpoint of the life of the light source.

<Problems to be Solved by the Invention> The technical problems to be solved by the present invention are such that the time difference problem does not occur when reading signals from the linear array sensor, and an initialization operation is not required prior to measurement. The purpose is to avoid unnecessary lighting of the light source.

Means for Solving the Problems> In the configuration of the present invention, the light source is turned off during a transition period when measurement is switched from the one measurement plate to another measurement plate, and during this period, the detection of the linear array sensor is The reason is that the charges accumulated in the element are sequentially read out.

<Operation> The above technical means operates as follows. That is, during the measurement period in which the measurement plate is backed by the paper, signals are not read out from the linear array sensor, and signals are read out during the transition period when the light source is turned off. did. During the measurement period, each detection element is irradiated for a certain period of time, and during the period during which signals are read out, there is no light irradiation and the charges accumulated in the detection elements during the measurement WJ are held as they are. Therefore, accurate signal reading can be performed.

<Example> The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention. In the figure, in Figure 3! ! Elements that are the same as the element are given the same reference numerals, and explanations thereof will be omitted.

Reference numeral 14 denotes a synchronization signal generation port which uses a reflective optical switch or the like and generates a synchronization signal in accordance with the timing of switching between the black plate 12a and the white plate 12b in the disc 12, and the signal from this is sent to the detection unit 1. The signal is given to the signal processing section 9 inside.

15 is a lamp drive circuit for the light source 4 to which a signal from the signal processing section 9 is applied.

Next, the operation of the apparatus according to the embodiment of the present invention configured as described above will be explained according to the timing chart of FIG. In FIG. 2, (a) shows the state of switching between the black plate 12a and the white plate 12b in the disc 12, and (b) shows the counter synchronization signal detected by the synchronization signal generation circuit 14. C) is the light 114 created based on the synchronization signal in Figure (b).
Figure (d) shows the readout state of the photodiodes D1 to Qn constituting the linear array sensor 8 with respect to the lamp trigger signal for driving.

The light source 4 is turned on during the measurement period when the white plate 12b and the black plate 12a are located on the back side of the paper 3 by the lamp trigger signal shown in FIG. exposed by the reflected light. When the light source 4 is turned off, signal reading is started at the timing of the fall of the lamp trigger signal (FIG. (d)).

During the transient period in which the signal is read out, the light source 4 is turned off, and the photodiode D is turned off during the measurement period.
The charges accumulated in 1 to On are held as they are. Therefore, if signals are read out in this state, the signals can be read out without error.

<Effects of the Invention> According to the present invention, the problem of time difference does not essentially occur when reading out a signal, and the detection element is initialized when reading out a signal. No light is irradiated during the transition period (it is maintained until the next measurement, so there is no need to perform an initialization operation again for the next measurement).

Furthermore, since the light source is turned off during the transition period, unnecessary lighting can be avoided and the life of the light source can be extended.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an apparatus according to an embodiment of the present invention, and FIG.
3 is a timing chart illustrating the operation of the device according to the embodiment of the present invention, FIG. 3 is a configuration diagram showing a conventional device, and FIG.
FIG. 5 is a circuit diagram showing a specific example of a linear array sensor, and FIG. 6 is a timing chart explaining the operation of the conventional device shown in FIG. 3. 3... Paper, 4... Light source, 7... Spectrometer, 8...
Linear array member, 9...signal processing section, 12...
Disc, 12a...Black plate, 12b...White plate, 14
... Synchronization signal generation circuit, 15 ... Lamp drive circuit,
D1~Dn...Photodiode 1 Figure 3: Pile 4: Optical line 7: 32'Nonear signal 12
: Ensai and 14: Rikichi 5 registration circuit in the same month ^
^ ^ (-〇 ) Figure 4 Figure 5 Trace 2

Claims (1)

[Claims] Light from a light source is irradiated onto the surface of the paper at a predetermined angle of incidence, and a plurality of measuring plates are rotated on the back side of the paper, and the reflection from the paper is detected when the measuring plates back the paper. The light is separated by a spectroscopic means, the spectroscopic spectrum is detected by a linear array sensor in which a plurality of charge accumulation type photodetecting elements are arranged in the wavelength distribution direction, and based on the detection signal from this linear array sensor, the optical In the apparatus for measuring characteristics, the light source is turned off during a transition period when the measurement is switched from the one measurement plate to the other measurement plate,
A paper optical characteristic measuring device characterized in that during this period, charges accumulated in the detection elements of the linear array sensor are sequentially read out.