JP2001063190A - Density measuring method and measuring device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely and efficiently grasp the characteristics peculiar to an optical density sensor to many density levels and their changes with time so as to immediately utilize the resultant grasped characteristic information in order to allow to execute the measurement of a more precise and higher reflection density. SOLUTION: This measuring system is to produce a sensor calibration curve obtained from the relationship between the sensor output information of a density sensor 14, which is obtained by receiving a reflected light H4 with the reflecting member 43a of a reflecting means 31 for calibration of a light H1 sent from the light emitting element 12 of the density sensor 14 and then guided to the reflecting means 31 for calibration having a light amount adjusting filter 42, the transmitted light amount of which changes continuously through moving action during calibration, and the reflecting member 43a, which reflects the light passed through the filter 42 so as to be received by the light receiving element 13 of the density sensor 14, in order to calculate the value of a reflective density of the output value obtained from the sensor at the later measurement of density based upon the information on the calibration curve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for more accurately measuring the reflection density of an image recorded on an image recorded on a recording medium such as a sheet or a three-dimensional object in which various images such as an ink image and a toner image are recorded. And a measuring device suitable for the method.

[0002]

2. Description of the Related Art As a method for measuring the density of an ink image or a toner image in a printed matter obtained by a general printing technique, a copy or a printed matter obtained by an electrophotographic method or an ink jet recording method, a light emitting element such as a light emitting diode is used. And an optical density sensor having a light receiving element such as a photodiode, and irradiates light from the light emitting element toward an image of a printed matter or the like as a measurement target, and receives light reflected by the image as a light receiving element. A technique of measuring a reflection density of a corresponding image by obtaining a corresponding reflection density value from a relationship between a sensor output value and a reflection density value created in advance and obtaining a sensor output (voltage) obtained by receiving light in the above-described manner is adopted. (For example, see Japanese Patent Application Laid-Open No. 5-215679).
JP, JP-A-9-6121).

In a method and an apparatus for measuring the reflection density of an image using this optical density sensor, the light emitting element and the light receiving element of the density sensor deteriorate with time, or the sensor detection surface of the density sensor deteriorates. Due to contamination etc., the initial performance can not be maintained and accurate concentration measurement becomes difficult,
The calibration of the density sensor is performed using a calibration plate (reference reflector) having a constant density reference and a white reference calibration chart arranged near the density sensor. That is, at a preset time, the light (light) from the light emitting element of the density sensor is applied to the calibration plate or the calibration chart, and the reflected light is received by the light receiving element of the sensor. The necessary characteristics are calibrated for the performance characteristics of the density sensor by grasping the characteristics. Incidentally, a blank recording sheet may be used as the calibration plate or the calibration chart.

[0004]

However, in such a concentration measuring method and apparatus for performing calibration, since a calibration plate or a calibration chart used at the time of the calibration has only one reference density, the reference Although the calibration near the density can be performed accurately, the accuracy of the calibration for the other density regions is not always accurate and cannot be guaranteed in many cases. In addition, when recording paper is used as a calibration plate or calibration chart, there are differences in the light reflection characteristics of each recording paper used and unevenness in the paper density. .

Further, the light emitting element, the light receiving element, and the optical system constituting the density sensor have inherent variations in their characteristics. Therefore, even from this, a uniform calibration plate or calibration system having only one reference density is used. Even if the calibration is performed based on the chart, there is a possibility that the reliability is lacking.

Further, when the number of calibrations is small and the concentration measurement is continued for a long time after the calibration, the current of the light emitting element and the light receiving element fluctuates due to a slight temperature change near the concentration measuring apparatus after the calibration. The sensor output value may fluctuate due to thermal deformation of the optical system such as a lens or the sensor housing or the sensor housing. It has been difficult to maintain the performance of the above and to ensure the reliability of the measurement accuracy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned various problems, and it is possible to accurately and efficiently evaluate the characteristics unique to (individual) optical density sensors and changes with time for many density levels. It is an object of the present invention to provide a density measuring method capable of measuring a reflection density more accurately and accurately by immediately utilizing the grasped characteristic information and a density measuring device used when performing the measuring method. Aim.

[0008]

According to a first aspect of the present invention, there is provided a method for measuring a density, which comprises using a density sensor having a light-emitting element and a light-receiving element, wherein the light from the light-emitting element is transferred. A method of irradiating an image of an image recorded matter and measuring a reflection density of the image based on a sensor output value obtained when the light receiving element receives reflected light from the image, The light from the light emitting element, at the time of calibration, a light amount adjusting filter in which the amount of transmitted light continuously changes by a moving operation, and a reflecting member that reflects light passing through the light amount adjusting filter and causes the light receiving element of the density sensor to receive the light. Sensor output information of the density sensor obtained when the reflected light reflected by the reflecting member of the calibration reflecting means is received, and the light amount adjustment flag. A sensor calibration curve consisting of the relationship between the sensor output value and the reflection density value is created from the transmitted light amount information of the filter, and the reflection density value is calculated from the sensor output value obtained at the subsequent density measurement based on the information of the sensor calibration curve. It is characterized in that it is obtained.

In the case of this concentration measuring method, a series of calibration operations up to creation of a sensor calibration curve may be performed at any time when the calibration operation is necessary. It is configured to perform the density measurement before executing the density measurement on the recorded matter.

On the other hand, a density measuring apparatus of the present invention used for carrying out the above-mentioned density measuring method comprises a density sensor having a light emitting element and a light receiving element, and a detecting means for detecting a reflection density value based on a sensor output value from the density sensor. Processing means,
A sensor unit disposed on a transfer path of an image recording material to be measured for density, a light amount adjusting filter in which a transmitted light amount continuously changes, a reflecting member for reflecting light passing through the light amount adjusting filter, and the light amount adjusting filter A reflecting means for calibration having a moving means for moving the transmitted light amount so as to be continuously changed, and the light from the light emitting element of the density sensor in the sensor unit is introduced into the reflecting means for calibration,
A sensor output value and a reflection density value are obtained from sensor output information of the density sensor obtained when light reflected by the reflection member is received by the light receiving element of the density sensor in the sensor unit and transmitted light amount information of the light amount adjustment filter. A calibration unit having a calibration processing unit that creates a sensor calibration curve consisting of the following relationship, and sends information on the sensor calibration curve to the detection processing unit of the sensor unit. A reflection density value is detected from a sensor output value obtained at the time of subsequent density measurement based on information of a sensor calibration curve created by calibration processing means of a calibration unit.

In the case of this concentration measuring device, the light amount adjusting filter of the calibrating reflection means comprises a light shielding portion and a light transmitting portion, and the occupancy of the light shielding portion and the light transmitting portion per unit area is determined by the filter. It is desirable that the light-shielding portion and the light-transmitting portion are formed at a specific ratio so as to be increased or decreased by the movement of.

Further, in the case of this density measuring device, the reflection member of the calibration reflecting means is set so that its reflection surface is at the same height as the density measurement surface of the image recorded matter at the time of calibration. desirable.

Further, in the case of this density measuring device, a plurality of density sensors are arranged in the sensor section at intervals on the same circumference, and the light quantity adjusting filter of the calibration reflecting means is provided. Has a circular area of a plurality of density sensors disposed in the sensor section and a disk of substantially the same size, and has a spiral shape in a region of the disk surface passing below the plurality of density sensors. A light-shielding portion or a light-transmitting portion is formed, and the spiral light-shielding portion or the light-transmitting portion is arranged so as to continuously pass below the density sensors by rotating the light amount adjusting filter. Is desirable.

According to the concentration measuring method and the measuring apparatus as described above, at the time of calibration, the light from the light emitting element of the density sensor is guided to the calibration reflecting means, so that the light from the light emitting element is reflected by the calibration reflecting means. The amount of transmitted light reaches the reflecting member while being continuously changed by the light amount adjusting filter in the means, and the reflected light reflected by the reflecting member is received by the light receiving element of the density sensor. As a result, in the density sensor, a sensor output value (output information) that receives reflected light whose light quantity changes continuously (in multiple stages) is obtained.
This makes it possible to accurately and efficiently grasp the latest characteristics unique to the concentration sensor and changes with time for many concentration levels during the calibration.

Then, a sensor calibration curve comprising the relationship between the sensor output value and the reflection density value is created from the sensor output information at this time and the transmitted light amount information of the light amount adjustment filter, and the subsequent density measurement is performed based on the calibration curve. The reflection density value at the time will be measured. This makes it possible to immediately and accurately measure the reflection density using the grasped characteristic information. In particular, this operational effect is remarkably obtained when a series of calibration operations until the creation of the sensor calibration curve is performed before (preferably immediately before) the density measurement for a new image recorded matter.

Such a density measuring method and measuring device can be used without any particular limitation in the field of an image recorded matter whose density can be measured by the reflection density. It is particularly useful when used in areas where higher precision is required for concentration measurements.

[0017]

[First Embodiment] FIG. 1 is a schematic diagram showing one embodiment of a concentration measuring apparatus used for carrying out a concentration measuring method of the present invention. This density measuring device is roughly classified into an image 2 on an image recording material 1 to be measured.
A sensor unit 10 for optically measuring the reflection density of the sensor unit 10 and a calibrating unit 30 for performing necessary calibration work on the sensors of the sensor unit 10.

The sensor section 10 includes a light emitting element 12 such as a light emitting diode and a light receiving element 13 such as a photodiode.
Optical density sensor 14 provided with
And detection processing means 15 for detecting the reflection density based on the sensor output (voltage) value from the sensor 4.

In this embodiment, as shown in FIG. 2, four density sensors 14A,
4B, 14C, and 14D, and the respective density sensors 14
A to A are arranged such that they are arranged at equal intervals on the same circumference on the lower surface side of the box-shaped sensor holder 11. These density sensors 14A to 14D
In any case, the irradiation light H1 from the light emitting element 12 is emitted from the light exit port 14a toward the image recording material 1, while the density measurement surface of the image recording material 1 (the image 2 whose density is to be measured is formed). (Diffused) reflected light H2 reflected by the light receiving element 13 from the light entrance 14b. Further, these four concentration sensors 14
It is of a type that performs density measurement of images of different colors from each other. The image 2 is formed in a positional relationship corresponding to the position of each density sensor 14 or at least one of the image density sensors 14. The density of the image 2 formed in the positional relationship where the density is measured can be measured.

Further, the sensor unit 10 is used to
The sensor detection surface 11a, which is the lower surface of the sensor holder 11 and on which the density sensor 14 is disposed, is located on the transfer path (the dashed line in FIG. 1) of the image recording material 1. Are arranged facing each other with a predetermined distance E at which the density can be measured. Further, the detection processing means 15 is constituted by a microcomputer or the like, and is usually disposed so as to be incorporated in a control section of a device main body using the concentration measuring device. 11 may be provided.

The reference numeral 20 in FIG.
Means for transferring the printed matter in such a state that the surface to be measured can be opposed to the sensor detection surface 11a of the sensor section 10. As shown in FIG. 1 and FIG. 4, the recorded matter transport means 20 in this embodiment records the desired ink image or toner image 2 whose image recorded matter 1 is to be measured on a sheet-like material such as recording paper. In the case where the image recording sheet 1 is a dedicated transfer unit, the image recording sheet 1 as an image recording material can be transferred to a density measurement position separated from the sensor detection surface 11a of the sensor unit 10 by a distance E. It is composed of a plurality of feed-side transport roll pairs 21, a feed-side transport roll pair 22, and the like, which are respectively disposed on both sides of the sensor unit 10. The transport unit 20 also moves the sheet 1 between the transport row pairs 21 and 22 so that the image recording sheet 1 is maintained in a horizontal state by the transport roll pairs 21 and 22 and can pass through the position where the density is measured. Are transported under a predetermined tension. Further, the image recording sheets 1 are set so as to be transported one by one at predetermined intervals (periodically) so as to be located at the density measurement position P1.

The calibration unit 30 basically includes the sensor unit 1
A calibration reflecting means 31 used when performing a calibration work on the density sensor 14 of zero, a displacement means 32 for displacing the calibration reflecting means 31 to a predetermined position during calibration and at the time of non-calibration, respectively; The calibration processing unit 33 performs information processing necessary for calibration of the density sensor based on information obtained by performing a calibration operation using the reflection unit 31.

As shown in FIG. 1, a calibrating reflecting means 31 constituting the calibrating unit 30 includes a dustproof opening / closing member 41, a light amount adjusting filter 42, and a reflecting member inside a box-shaped holder 40 having a hollow structure. 43 are attached to the support shaft 44 in such a manner as to be superimposed from top to bottom in this order, and the first rotation moving means 45 and the light amount adjustment filter 42 for rotating the dustproof opening / closing member 41 during calibration are provided. Second rotation moving means 4 for rotationally moving at the time of calibration
6 are provided. Reference numeral 44 a in the figure denotes a pedestal for erecting the support shaft 44, which is fixed to the holder 40.

As shown in FIGS. 1 and 3, the holder 40 is formed so as to entirely function as a light-shielding cover. At the position opposite to the position, the irradiation light H1 from each density sensor 14 enters the inside of the holder at the time of calibration, and then the reflected light H3 reflected by the reflection member 43 goes out of the holder to output the density sensor 14 4 large enough to be received by
Two openings 47 are opened.

As shown in FIG. 3, the dustproof opening / closing member 41 is entirely formed in a disk shape, and its outer peripheral portion is provided with a total of four positions at positions corresponding to the openings 47 of the holder 40. A light transmission port (actually, an opening) 48 is formed,
The portion other than the light transmitting port 48 is formed so as to function as a closing surface that blocks the opening 47 and prevents dust and the like from entering the holder 40. As shown in FIG. 1, the disc-shaped opening / closing member 41 is rotatably supported by a support shaft 44 and supported by a driving force of a pulse motor serving as a first rotation moving means 45. It is designed to rotate about an axis 44. Then, at the time of calibration (FIG. 6), the opening / closing member 41 stops after rotating its light transmission port 48 to a position where it faces the opening 47 of the holder and coincides with it, and at the time of non-calibration (FIG. 3). Is the light transmission port 48
Is rotated to a position facing a portion other than the opening 47 of the holder and then stopped.

Incidentally, the rotational force of the pulse motor, which is the first rotational moving means 45, is transmitted via a gear to an opening / closing member 41 having a tooth profile with which the gear meshes on the outer peripheral edge. The amount of rotation of the opening / closing member 41 is accurately controlled by encoder control. The rotation drive transmission mechanism and the control method are similarly employed between the light amount adjustment filter 42 and the second rotation moving means 46 described later.

The light amount adjusting filter 42 is used for the density sensor 1 introduced into the calibrating reflection means 31 at the time of calibration.
4 is a filter for continuously changing the transmitted light amount of the irradiation light H1 from the light emitting element 4 (light emitting element 12). In this embodiment, as shown in FIG. 1 and FIG. 3, the filter as a whole has a disk shape having substantially the same size (area) as the circular region in which the plurality of concentration sensors 14 are arranged in the sensor unit 10. Basically, the light pass band 42 a through which the light from the density sensor 14 can pass is constituted by the light blocking portion 50 and the light transmitting portion 51. The light-shielding part 50 and the light-transmitting part 51 are both unit areas (the density sensor 1).
The occupation rate Y of the irradiation light H1 per spot diameter K) when reaching the filter 42 from 4 is increased / decreased by a rotational movement of the filter 42 at a specific ratio.

More specifically, as shown in FIG. 3 and FIG. 7, the area along the boundary line L composed of an involute curve is formed on the light passing band 42a having a width W corresponding to the light spot diameter K on the outer periphery of the filter. The light shielding portion 50 (or the light transmitting portion 51), which increases and decreases in proportion to the circumferential direction, is formed. That is, the light-shielding portion 50 and the light-transmitting portion 51 have their occupancy ratios per unit area of “0 to 0” during one rotation of the filter 42.
For example, the occupation ratio of the light shielding unit 50 increases from “0” to “100”.
Conversely, the occupation ratio of 1 is gradually reduced from “100 to 0”. Such a filter 42 is formed, for example, by applying a light-shielding material to a portion corresponding to the light-shielding portion 50 on a transparent glass disk and leaving the remaining portion as a transparent glass plate. It is formed.

As shown in FIG. 1, the light amount adjusting filter 42 is rotatably supported on a support shaft 44, and is supported by a driving force of a pulse motor serving as a second rotation moving means 46. It rotates around 44. Then, as shown in FIG. 7, the filter 42 has its rotation start point SP (the occupation ratio Y ₅₀ of the light shielding unit ₅₀ is “100” so that the amount of transmitted light per unit area is continuously changed during calibration. time in, at the rate of occupancy ratio Y ₅₁ of the light transmitting portion 51 by 1 ° week) of "0" starts to rotate intermittently, returning to (starting point SP after rotated by 360 ° for one rotation At) to stop.

Further, the amount of light transmitted (corresponding to the reflection density) by the light amount adjustment filter 42 is, as illustrated in FIG. 8, the irradiation light H from the light emitting element 12 of the density sensor 14.
Since the spot diameter at the time when 1 reaches the filter 42 is always at the same position, the light-shielding part 50 and the light-transmitting part 51 are separated from the spot diameter of the irradiation light H1 by the boundary line L composed of the involute curve. It is determined by the relationship with the occupancy Y per unit area. In particular, in this embodiment, since the light amount adjustment filter 42 is a disk-shaped member that rotates and moves, the transmitted light amount is equal to the irradiation light H1.
Is proportional to (depends on) the rotation angle of the filter corresponding to the relationship between the spot diameter and the occupation ratio Y of the light shielding portion 50 or the light transmitting portion 51. In this embodiment, the filter 4
2 is at the rotation start point SP, the amount of transmitted light with respect to the irradiation light H1 of the density sensor 14A becomes 100%, and when the filter 42 rotates in the direction of the arrow and its rotation angle θ is 50 ° C., the irradiation of the density sensor 14A It is configured such that the amount of transmitted light with respect to the light H1 is 0%.

As shown in FIG. 1 and FIG. 3, the reflection member 43 reflects the light after passing through the (light transmission section 51) of the light amount adjustment filter 40, and
4 is a member for causing the light receiving element 4 to receive light.
4 is fixed. In this embodiment, the whole is formed in a disk shape almost corresponding to the light amount adjusting filter 42, and at least the light amount adjusting filter 42
The region 43a corresponding to the light transmission band 42a is a reflection surface such as a mirror surface. Further, the reflecting member 43 is set such that the reflecting surface 43a thereof is at substantially the same height as the surface to be measured of the image recording sheet 1 at the time of calibration.

The displacement means 32 constituting the calibrating section 30 faces the sensor detecting surface 11a of the sensor section 40 at the time of calibrating the calibrating reflecting means 31, and irradiates the light from the light emitting element 12 of the density sensor 14 in the sensor section 10. In addition to displacing H1 to the calibration work position P1 into which the H1 can be introduced, at the time of non-calibration, it is displaced to at least the retreat position P2 which does not hinder the concentration measurement work.

In this embodiment, a cam mechanism is employed as the displacement means 32, and the calibration means 3 is provided by the cam mechanism.
A configuration is employed in which the device 1 is moved vertically just below the sensor unit 10. That is, the displacement means 32 moves the calibration reflection means 31 up and down by a necessary distance (about the distance E) together with the holder 40 by the cam action of the eccentric cam 32b rotated by the rotation shaft 32a. Thereby, at the time of calibration (FIG. 5), the entire holder is raised to a position where the upper surface of the holder 40 of the calibration reflecting means 31 approaches or contacts the sensor detection surface 11a which is the lower surface of the sensor unit 10, When not calibrating (Figs. 1 and 4)
Is set so that the calibration reflecting means 31 lowers the entire holder to a position where it does not hinder the transfer of the image recording sheet 1 by the transfer unit 20 or the hindrance of the density measurement. Moreover, in this embodiment, the displacement means 3
2, the reflecting surface 43 of the reflecting member at the time of calibration.
a is set to the same height as the density measurement surface of the image recording sheet 1 (FIG. 5), and the upper surface of the holder 40 is set to be almost the same height as the transfer path of the image recording sheet 1 during non-calibration. (FIGS. 1 and 4).

The calibration processing means 33 constituting the calibration section 30
Performs a process of creating a sensor calibration curve (FIG. 10) based on information obtained by the following calibration work, and transmitting information of the sensor calibration curve to the detection processing unit 15 of the sensor unit 10. It is composed of a microcomputer and the like. In the calibration operation, the irradiation light H1 from the light emitting element 12 in the density sensor 14 of the sensor unit 10 is guided into the holder 40 of the calibration reflection unit 31 displaced to the calibration operation position P1 by the displacement unit 32, and the movement operation is performed. The light passes through a light amount adjustment filter 42 in which the amount of transmitted light changes continuously, and the light H3 that has passed through the filter 42 is reflected by the reflection member 43 of the calibration reflection unit 31 and the reflected light H4 is received by the light receiving element 13 of the density sensor 14. This is the task of making In the calibration processing means 33, first, the sensor output information of the density sensor 14 obtained in the calibration work at this time and the transmitted light amount (movement amount) of the light amount adjustment filter 42.
From the information, a sensor calibration curve composed of the relationship between the sensor output value and the reflection density value is created. Next, the information of the sensor calibration curve is transmitted to the detection processing means 15 of the sensor unit 10 for use in the subsequent concentration measurement.

The creation of the sensor calibration curve is generally performed as follows.

First, when the amount of light transmitted by the light amount adjusting filter 42 is 100% (the occupation ratio Y of the light transmitting portion 51).
_{When 51} is "100" and the irradiation light H1 is transmitted through all the filters 42) and when the amount of transmitted light is 0% (when the occupation ratio Y50 of the light shielding unit ₅₀ is "0"). (In a case where the irradiation light H1 is completely blocked by the filter 42 and does not transmit), the sensor output value of the density sensor 14 is measured, and each output value at that time is referred to as the “brightness characteristic” of the calibration reflection means 31 of the calibration unit 30. "Or" dark characteristic ". At this time, even if the transmitted light amount is 0%, some light enters the light receiving element 13 so that the sensor output value does not become completely zero. And the "brightness"
The sensor output value at the time is the minimum value of the reflection density value D (Mi
n), and the sensor output value at the time of the “dark characteristic” is the maximum value (Max) of the reflection density value D.

Next, the light amount adjusting filter 42 is moved by a unit movement amount (calibration point) from the state of the filter 42 at the time of the "bright characteristic" to the state of the filter 42 at the time of the "dark characteristic". The sensor output value of the density sensor 14 corresponding to each transmitted light amount is measured and obtained while continuously changing the transmitted light amount by the light receiving device 42. As a result, sensor output information of the density sensor 14 (latest characteristic information) and transmitted light amount (movement amount) information of the light amount adjustment filter 42 at the time of the calibration work are obtained (FIG. 9). Then, after replacing (or converting) the transmitted light amount information with the reflection density value D, a sensor calibration curve (actually, a collation table) is created from the relationship between the reflection density value D and the sensor output information. .

The information on the sensor calibration curve created in this way is transmitted to the detection processing means 15 of the sensor unit 10 and used at the time of concentration measurement after the calibration work. That is, when the density sensor 14 of the sensor unit 10 measures the density of the image 2 of the image recording sheet 1 to be measured, the sensor output value obtained by the sensor unit 10 is compared with the sensor output value in the sensor calibration curve. A reflection density value corresponding to the output value is obtained in light of the relationship between the reflection density values.

In this density measuring apparatus, the image recording sheet 1 to be measured for density is intermittently moved by the recorded material transferring means 20 (with a gap such that the calibration by the calibration unit 30 can be performed). Since the transfer is performed and the density measurement is performed, at least before the density measurement of the one image recording sheet 1 is performed, the calibration operation by the calibration unit 30 is always performed once. Have been. In order to perform the calibration work at such a timing, the sensor unit 10 is always operated (a state in which the light emitting element 12 of the density sensor 14 is in a light emitting state and the light receiving element 13 is kept in a light receiving state). Each time, a predetermined change in the light receiving state (sensor output value) makes it possible to determine whether or not the image recording sheet 1 is transferred to a position directly below the sensor unit 10 and to determine whether the image recording sheet 1 is present. Is set so as to execute the calibration work by the calibration unit 30 when the calibration is performed.

Next, the operation of the concentration measuring device will be described.

When a command to start the concentration measurement is issued, FIG.
As shown in (1), the sensor unit 10 is activated to start detecting the presence or absence of the image recording sheet 1, and each of the transport roll pairs 21 and 22 of the recording material transport unit 20 is driven to rotate to transport the image recording sheet P1. Is started. In this embodiment, since the initial calibration work is performed, the transfer of the image recording sheet P1 is started after the initial calibration work is completed.

In this initial stage, the calibrating section 30 has the calibrating reflection means 31 at the retracted position P2. And
At this time, the upper surface of the holder 40 in the calibrating reflection means 31 has substantially the same height as the transfer path of the image recording sheet 1. Further, the dustproof opening / closing member 4 of the calibration reflecting means 31 is provided.
1 is stopped at a position to close the opening 47 of the holder 40 (FIG. 3). Thereby, the sensor unit 10 in the operating state is
Light H from the light emitting element 12 of the density sensor 14 at
When the image recording sheet 1 does not exist, the upper surface 1 is irradiated on the upper surface of the holder 40 (actually, the upper surface which is the closing surface of the dustproof opening / closing member 41 through the opening 47 of the holder 40), and is reflected by the upper surface. The reflected light H4 is transmitted to the density sensor 1
The light receiving element 13 receives light. For this reason, the upper surface of the dust-proof opening / closing member 41 is formed in a surface state such that at least diffused reflected light different from that of the image recording sheet 1 can be obtained.

Immediately after the density measurement start command is issued, the sensor unit 10 determines that the image recording sheet 1 does not exist at the density measurement position immediately below the sensor unit 10, and the first image recording sheet is recorded. Before the sheet 1 is transferred to the density measurement position of the sensor unit 10, a calibration operation by the calibration unit 30 is performed. The calibration work before starting the concentration measurement
Regardless of whether the sensor unit 10 detects the presence or absence of the image recording sheet 1, it is set to be forcibly performed before the image recording sheet 1 is transported.

First, as shown in FIG. 5, the calibrating reflection means 31 is moved by the cam of the displacement means 32 so that the holder 4 is moved.
It moves upward by 0, moves from the retreat position P2 to the calibration work position P1, and stops. As a result, the upper surface of the holder 40 of the calibrating reflection means 32 is in a state of being substantially in close contact with the sensor detection surface 11a of the sensor unit 10, and
The reflecting member 34 of the calibrating reflecting means 32 is at the same height as the surface of the image recording sheet 1 where the density is to be measured.

When the calibrating reflection means 31 moves to the calibration work position P1 and stops, the dustproof opening / closing member 41 is rotated in the direction of the arrow by the pulse driving of the pulse motor as the first rotation moving means 45, and its light transmission port is opened. 48 is the opening 4 of the holder
It stops when it reaches a position that matches the position opposite to (FIG. 6). Thus, the opening 47 of the holder is in an open state, so that the irradiation light H1 from the light emitting element 12 of the sensor unit 10 is guided into the holder 40 of the calibration reflection unit 32.

Subsequently, at the same time as the rotation of the dustproof opening / closing member 41 is stopped, as shown in FIG. 6, the light amount adjusting filter 42 is turned by 1 ° in the direction of the arrow by the pulse driving of the pulse motor as the second rotation moving means 46. Start to rotate little by little. Initially, as shown in FIGS. 6 and 7, the light amount adjustment filter 42 has its transmitted light amount set to “0” in a state where the light shielding portion 50 covers the entire spot diameter of the irradiation light H1 from the density sensor 14A. From that state, and rotate by 1 ° in the direction of the arrow. The light amount adjustment filter 42
May be continuously rotated instead of being rotated by 1 ° (data collection at the time of calibration is sufficiently possible).

As a result, as shown in FIG. 5, the transmitted light quantity of the irradiation light H1 guided into the holder 40 of the calibration reflection means 31 is continuously changed by the rotational movement of the light quantity adjustment filter 42. While being transmitted, the light is reflected by a reflecting member 43 located below the filter 42 and at the same height as the density measurement surface of the image recording sheet 1. At this time, since the height of the reflection surface of the reflection member 43 is substantially the same as the height of the density measurement surface of the image recording sheet 1, the density sensor 14 and the density measurement surface of the image recording sheet 1 at the time of density measurement are used. The same distance relationship as the distance to the distance is maintained, so that accurate calibration can be performed. afterwards,
The reflected light passes through the light amount adjustment filter 42, the light transmitting part 48 of the dustproof opening / closing member, and the opening 47 of the holder, and is received by the light receiving element 13 of the density sensor 14 in the sensor unit 10.

The reflected light is received by the light amount adjusting filter 4.
2 is continued by a predetermined angle, and then the filter 42 rotates to the rotation start point SP and returns to the initial state. As a result, a sensor output value (output information) of the density sensor 14 when the reflected light whose light quantity changes continuously (in multiple stages), that is, the reflected light whose reflection density continuously changes is received, is obtained. The calibration processing means 33 creates a sensor calibration curve based on the above information.

FIG. 9 is a table showing the relationship between the rotation angle θ of the light amount adjustment filter 42 (the angle of the rotational movement from the rotation start point SP) and the sensor output value obtained by the calibration work.

First, in this table, the dark characteristics of the calibration reflecting means 31 (similarly when the transmitted light amount is 0%,
The sensor output value at the rotation angle θ = 0 °) is 1 V, and its bright characteristic (the amount of light transmitted through the filter 42 is 100)
%, Which corresponds to a rotation angle θ = 310 °)
Indicates that the sensor output value at 5 V is 5V.
Further, the sensor output value of the bright characteristic is calculated as a reflection density value D.
Is set to the maximum value “2”, and the sensor output value in the dark characteristic is set to the minimum value “0.277” of the reflection density value D. Each sensor output value when the rotation angle θ of the light amount adjustment filter 42 is rotated by 1 ° (this corresponds to the resolution or the number of calibration points) is obtained. The sensor output value at this time is obtained by averaging a plurality of sensor output values obtained for each rotation angle θ, thereby improving the calibration accuracy. Regarding the transmitted light amount (%) of the light amount adjusting filter 42 with respect to each rotation angle θ, first, the change amount of the transmitted light amount of the filter 42 per rotation angle θ1 ° of the filter 42 is about 0.3226 (= 100% / 310 °). ) Is obtained as “0.3226 × rotation angle θ”. Further, as for the reflection density value D at this time, the difference between the maximum value and the minimum value is 1.7223 (= 2−0.2777), and the difference in the transmitted light amount by the light amount adjustment filter 42 is 3
10 (= 360-50), the rotation angle θ1
The reflection density value per degree is about 0.00555 (= 1.72).
23/310), and the reflection density value per rotation angle (the amount of transmitted light) is obtained as “2.0− (0.00555 × rotation angle θ)”.

FIG. 10 is a graph curve created from the relationship between the rotation angle θ of the light amount adjustment filter 42 obtained by the above-mentioned calibration operation and the sensor output value, and the rotation angle θ on the vertical axis is used as the reflection density value. The graph curve composed of the relationship between the sensor output value and the reflection density value becomes the “sensor calibration curve”. As a result, the actual state of the current (latest) performance characteristics of each concentration sensor 14 is reliably grasped. When there are a plurality of density sensors 14 as in this embodiment, the initial positional relationship between the light amount adjustment filter 42 and the spot diameter of the irradiation light H1 from each of the density sensors (for example, associating with the rotation angle θ). Calibration work is performed on a plurality of density sensors at the same time in advance as initial values for data acquisition, and a sensor calibration curve is created for each of the density sensors.

In the calibration processing means 33, a collation data table corresponding to such a sensor calibration curve is actually created. Then, the information on the sensor calibration curve is sent to the detection processing means 15 of the sensor unit 10 and used for subsequent concentration measurement. Thus, the initial calibration work before the concentration measurement is completed. Particularly in this embodiment, the sensor unit 1
Although the four density sensors 14 are arranged at 0, the time and space required for the calibration work can be minimized.

When the initial calibration work is completed,
First, as shown in FIG. 4, the calibration reflection means 31 is moved down together with the holder 40 by the cam operation of the displacement means 32, and moves from the calibration work position P1 to the retreat position P2 and stops. As a result, the calibration reflecting means 32
The upper surface of the holder 40 has substantially the same height as the conveying path of the image recording sheet 1, and the image recording sheet 1 to be measured for density is kept horizontal by the upper surface of the holder 40.

When the calibration reflecting means 31 moves to the retreat position P2 and stops, the dustproof opening / closing member 41 is rotated in the direction of the arrow by the pulse drive of the pulse motor as the first rotation moving means 45, and its light transmission port is opened. 48 is the opening 4 of the holder
It stops after rotating to a position facing a portion other than 7 (FIG. 3). As a result, the opening 47 of the holder 40 of the calibration reflection means 31 is closed, so that the irradiation light H1 from the light emitting element 12 is prevented from entering the holder 40 and the dust or the like enters the holder. Is prevented, and the filter 42 and the reflection member 43 are prevented from being stained.

Then, the calibration reflecting means 31 is moved to the retracted position P.
When the opening 47 of the holder is closed by the dustproof opening / closing member 41, the transport roll pairs 21 and 22 of the recording material transporting means 20 are driven to rotate, and the transport of the image recording sheet 1 is started. Subsequently, depending on the operation state of the sensor unit 10, the image recording sheet 1 is moved to the sensor detection surface 1 of the sensor unit 10.
When it is detected that the image recording sheet 1 has been transferred below, the density of the image recording sheet 1 is measured.

That is, as shown in FIG. 4, the image recording sheet 1 is kept below the sensor detecting surface 11a of the sensor unit 10 in a state where a predetermined tension is applied by the pair of conveying rolls 21 and 22 of the transferring means 20. When the image recording sheet 1 is conveyed at a speed of? Then, the diffuse reflected light H2 is received by the light receiving element 13 of the density sensor 14. The signal received by the light receiving element 13 is sent to the detection processing means 15 as a sensor output value.

The detection processing means 15 collates the sensor output value obtained by the density measurement based on the sensor calibration curve (FIG. 10) created by the above-mentioned initial calibration work.
The reflection density value D to be determined is detected. For example, when the sensor output value is 2 V, the reflection density value is determined to be “1.5” from the sensor calibration curve. As a result, the density measurement according to the actual state of the performance characteristics of the respective density sensors 14 is performed, so that a highly accurate density measurement can be performed.

When the density measurement of the image recording sheet 1 is completed, the image recording sheet 1 passes below the sensor section 10 by the transport of the recorded article transport means 20 and no longer exists. The light receiving state of the density sensor 14 changes depending on the state, and the image recording sheet 1
Is not below the sensor detection surface 11a of the sensor unit 10 (FIG. 1).

Then, the next calibration work is performed. That is, the calibration reflecting means 31 is moved to the calibration work position P1 again (FIG. 5), and the above operation steps are repeated in the same manner to create a sensor calibration curve, which is used for the next concentration measurement. . When the calibration operation is completed, the calibration reflection means 31 is moved to the retreat position P2 (FIG. 4), and the above-described operation steps are repeated in the same manner to measure the density of the next image recording sheet 1.

Thus, at the time of the next concentration measurement,
Since the concentration measurement is immediately performed in a state where the actual state of the performance characteristics immediately before the concentration sensor 14 is grasped, the highly accurate concentration measurement is always performed by the calibrated sensor unit 10. Therefore, according to the concentration measuring device and the concentration measuring method, the concentration sensor can be calibrated each time before the concentration measurement, so that it is possible to appropriately cope with a temporal change in performance characteristics and the like of the concentration sensor.

As shown in FIG. 11, as an image 2 to be measured for density, four images are arranged side by side in the direction perpendicular to the direction of transport of the image recording sheet 1 (dashed line with arrow in the figure). When two different images 2A, 2B, 2C, and 2D are formed, the four density sensors 14 in the sensor unit 10 are located in the passages of the respective images 2A to 2D (regions between the dotted lines). And measure the concentration. When the density sensors 4 are arranged in this manner, the density measurement of each of the images 2A to 2D can be performed simultaneously in parallel while being distributed to the density sensors 14A to 14D. Becomes possible. In addition, even when the density sensors 14 are arranged as described above, the calibration of each density sensor 14 is performed by the calibration reflection unit 3 having the light amount adjustment filter 42 described above.
1 can be done similarly and easily.

[Other Embodiments] In the first embodiment, the light amount adjusting filter 42 is of a type in which the light shielding portion 50 and the light transmitting portion 51 are formed in a spiral shape. The present invention can be applied to any filter having a configuration in which the amount of transmitted light changes continuously by operation without any particular limitation.

For example, as shown in FIG. 12, the light shielding portions 50 (or light transmitting portions) for shielding (or transmitting) the spots K of the irradiation light H1 from a plurality of density sensors arranged at intervals in a circular shape. The light transmitting portion 51) is formed in accordance with the interval between the spots, and is formed in such a manner that the transmitted light amount for each spot K is continuously changed by rotating and moving in the direction of the arrow. A transmission filter 420 can be applied.

Further, as shown in FIG. 13, the light-shielding portion is linearly moved with respect to the spot K of the irradiation light H1 from the density sensor arranged at a plurality of intervals in one or one horizontal row. The light transmitting portion 51 and the light transmitting portion 51 are formed symmetrically so that the occupancy Y changes while being continuously inverted. For example, by linearly moving in the direction of the arrow, the amount of transmitted light to the spot K changes continuously. It is also possible to apply a flat plate-like light amount adjustment filter 422 configured as described above. In the case of the filter 422 having such a configuration, instead of a method in which the entire filter is simply moved linearly in the direction of the arrow, the entire filter is formed in a flexible belt form, and only the area passing through the spot K passes in a smooth plane. The filter may be supported so as to rotate (circulate) the entire filter.

Further, in the first embodiment, the case where the cam mechanism is employed as the displacement means 32 of (the holder 40 of) the calibration reflection means 31 has been described, but in the present invention, the calibration reflection means 31 is moved to the calibration work position. Any means that can be displaced between P1 and the retreat position P2 can be applied. The retreat position P2 is also used in the first embodiment.
The position is not limited to such a position, but may be a position in the horizontal horizontal direction instead of a position below the calibration work position P1. Further, in the first embodiment, the calibration reflecting means 31
Although the case where the sensor unit 10 is displaced so as to approach the sensor unit 10 has been described as an example, the sensor unit 10 may be displaced so as to approach the calibration reflection unit 31 side.

In the first embodiment, the calibration is performed between the density measurement of the image recording sheet and the density measurement of the next image recording sheet (interval), and the density measurement of the first image recording sheet is performed. Although the case of performing immediately before performing (initial calibration work) is illustrated, the present invention is not particularly limited to this, and can be appropriately changed according to the accuracy required for concentration measurement and the like. For example, the calibration work may be performed only at intervals without performing the initial calibration work.

Further, in the first embodiment, the sensor 10
As an example, four density sensors 14 are used, but in the present invention, the number of the density sensors 14 is also arbitrary, and may be one or a plurality other than four. Further, the density sensor 14 and the arrangement thereof are also arbitrary, and can be changed as appropriate according to the use or the like. On the other hand, the image recorded matter to be measured for the density is not limited to the sheet-shaped material as in the first embodiment, but may be one in which the image 2 is formed on the surface of a three-dimensional structure. In this case, the three-dimensional structure may be transferred so as to be positioned below the sensor detection surface of the sensor unit 10 or the like.

[0068]

As described above, according to the density measuring method and the measuring apparatus of the present invention, the characteristics inherent to the optical density sensor and the change with time for many density levels can be accurately and efficiently grasped. By utilizing the grasped characteristic information immediately, it is possible to more accurately and accurately measure the reflection density.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a concentration measuring device according to a first embodiment.

FIG. 2 is an explanatory diagram showing a configuration of a sensor unit as viewed from a lower surface side thereof.

FIG. 3 is an exploded explanatory view showing a configuration and a positional relationship of each member of a calibration reflection unit at the time of non-calibration.

FIG. 4 is a schematic diagram showing a state of the concentration measuring device at the time of concentration measurement.

FIG. 5 is a schematic diagram showing a state of the concentration measuring device during a calibration operation.

FIG. 6 is an exploded explanatory view showing a configuration and a positional relationship of each member of the calibration reflecting unit at the time of calibration.

FIG. 7 is an explanatory diagram showing an operation state of a light amount adjustment filter.

FIG. 8 is an explanatory diagram showing a relationship between a light amount adjustment filter and a change state of a transmitted light amount due to rotational movement of the filter.

FIG. 9 is a table showing a correlation between a rotation angle of a light amount adjustment filter, a sensor output, and a reflection density value obtained by a calibration operation.

FIG. 10 is a diagram showing an example of a sensor calibration curve created by a calibration operation.

FIG. 11 is an explanatory diagram showing an example of an arrangement of density sensors suitable for images arranged in one horizontal row.

FIG. 12 is an explanatory plan view showing another configuration example of the light amount adjustment filter.

FIG. 13 is an explanatory plan view showing another configuration example of the light amount adjustment filter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image recording sheet (image recording material), 2 ... Image (of a density measurement object), 10 ... Sensor part, 12 ... Light emitting element, 13 ...
Light receiving element, 14: density sensor, 15: detection processing means, 3
0: calibration unit, 31: calibration reflection unit, 33: calibration processing unit, 42: light intensity adjustment filter, 43: reflection member, 50
... Shielding part, 51. Light transmitting part, H1. Irradiation light, H2, H4
... Reflected light, H3 ... Transmitted light whose transmitted light amount has changed.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Mao Nagata 2274 Hongo, Ebina-shi, Kanagawa Prefecture, F-term in Fuji Xerox Co., Ltd. MM14 2H027 DA09 DE02 DE07

Claims (6)

[Claims] 1. A light emitting element and a light receiving element are used to irradiate light from the light emitting element to an image of an image recording object to be transferred whose density is to be measured, and reflected light from the image is received by the light receiving element. A method for measuring the reflection density of the image based on a sensor output value obtained when the element receives light, wherein the light transmitted from the light emitting element of the density sensor is continuously adjusted by a moving operation at the time of calibration. And a reflection member for reflecting the light passing through the light amount adjustment filter and receiving the light by the light receiving element of the density sensor, and guiding the light to the calibration reflection means. The relationship between the sensor output value and the reflection density value from the sensor output information of the density sensor obtained when the reflected light is received and the transmitted light amount information of the light amount adjustment filter. Create a Ranaru sensor calibration curve, the concentration measurement method is characterized in that from sensor output values obtained during subsequent concentration measurement information of the sensor calibration curve based on to obtain the reflection density value. 2. The density measuring method according to claim 1, wherein a series of calibration operations until a sensor calibration curve is created is performed before executing a density measurement for a new image recorded matter. 3. A density sensor having a light emitting element and a light receiving element, and detection processing means for detecting a reflection density value based on a sensor output value from the density sensor. A sensor unit disposed on the transfer path, a light amount adjustment filter that continuously changes the amount of transmitted light, a reflection member that reflects light passing through the light amount adjustment filter, and a light amount adjustment filter that continuously changes the amount of transmitted light Calibration means having a moving means for moving the light from the light emitting element of the density sensor in the sensor unit into the calibration reflection means, and the reflected light reflected by the reflection member is reflected by the sensor unit. From the sensor output information of the density sensor obtained when the light is received by the light receiving element of the density sensor and the transmitted light amount information of the light amount adjustment filter. A calibration unit having a calibration processing unit that creates a sensor calibration curve composed of a relationship between a force value and a reflection density value, and sends information on the sensor calibration curve to a detection processing unit of the sensor unit. A density measuring device, wherein the detection processing means detects a reflection density value from a sensor output value obtained at the time of subsequent density measurement based on information of a sensor calibration curve created by the calibration processing means of the calibration unit. . 4. The light amount adjusting filter of the calibration reflecting means includes a light shielding portion and a light transmitting portion, and the occupancy of the light shielding portion and the light transmitting portion per unit area increases or decreases as the filter moves. The light shielding portion and the light transmitting portion are formed at a specific ratio as described above.
The concentration measuring device according to the above. 5. The calibration member according to claim 3, wherein the reflection member is set such that its reflection surface is at the same height as the surface to be measured of the image recording material at the time of calibration. Concentration measuring device. 6. A sensor according to claim 1, wherein a plurality of density sensors are arranged at intervals on the same circumference, and a light quantity adjusting filter of said calibration reflecting means is provided in said sensor section. A circular light-shielding portion or a light-transmitting portion is formed in a circular area in which the density sensor is disposed and a disk of substantially the same size, and in a region of the disk surface passing below the plurality of density sensors. 4. A light shielding portion or a light transmitting portion having a spiral shape and being disposed so as to continuously pass below each of the density sensors by rotating a light amount adjusting filter. The concentration measuring device as described in the above.