JPH0616010B2 - Concentration calibration method - Google Patents

Description

The present invention relates to a density calibration method for calibrating a measured value using a density reference plate.

[Conventional technology]

The densitometer includes a transmission densitometer for measuring the transmission density of the measured object and a reflection densitometer for measuring the reflection density of the measured object. These densitometers are widely used in the field of image recording (photographing, printing, etc.) for measuring the characteristics of an image recording medium and measuring the density of a recorded image. Also in the field of measurement, pressure measurement using, for example, a pressure measurement film and a reflection densitometer is performed. This pressure measuring film is
The color density (magenta density) is designed to change according to the pressure. These are placed in a place where pressure is applied to develop color, and the reflection density of this color development part is measured. The pressure is checked by referring to the conversion table showing the relationship.

A conventional densitometer is composed of a densitometer main body provided with an arithmetic unit, a meter, a power supply circuit and the like, and a measuring head for measuring reflected light or transmitted light of an object to be measured. This measuring head is provided with a light projecting system that emits illumination light, a measurement system that measures reflected light or transmitted light, and a reference light measurement system that measures reference light obtained by extracting a part of the illumination light. There is.

In general, when using a densitometer, it is necessary to perform zero point correction before measuring the object to be measured. this is,
It is intended to correct measurement errors due to environmental factors such as ambient temperature and external light, and internal factors due to aging of lamps, light receiving elements, etc. It is adjusted so that there is no deviation from the value.

At the time of this zero point correction, for example, the low-concentration reference plate is measured, and the adjusting knob is turned so that the meter pointer of the densitometer body indicates the low-concentration reference value which is the concentration of the low-concentration reference plate. Next, the high-concentration reference plate is measured, and the adjusting knob is adjusted so that the meter pointer indicates a known high-concentration reference value.
This adjustment operation is performed multiple times so that the meter pointer indicates the known low-density reference value and high-density reference value.

[Problems to be solved by the invention]

In the above-described conventional zero-point correction method, the adjustment knob has to be operated a plurality of times to adjust the shake of the meter pointer, so that the adjustment operation is troublesome.

[Object of the Invention]

It is an object of the present invention to provide a concentration calibration method that does not require an adjusting operation at the time of zero correction.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention was obtained by measuring a low-density reference plate and a high-density reference plate whose low-density reference value R _L and high-density reference value R _H are known at the time of zero correction, respectively. Concentration reference measurement values R ₁ and R _{2 of} various types and known concentration reference values R _L ,
The zero point correction data is calculated from the deviation from _RH and stored in a memory, and the measured value obtained by measuring the object to be measured is calibrated using this zero point correction data. . The zero-point correction data is composed of a coefficient term α and a constant term K, and is calculated by the following equations.

Then, when the measured concentration value of the object to be measured is R _D , the calibrated measured value R is obtained as R = R _D −αR _D −K.

[Action]

According to the present invention, the zero point correction data is created at the time of zero point correction, and the measured value is calibrated using the zero point correction data. Therefore, the conventional adjustment operation is not necessary, and the zero point correction is extremely simple.

An embodiment of the present invention will be described in detail below with reference to the drawings.

〔Example〕

FIG. 2 shows an external view of a reflection densitometer embodying the present invention, which has a handy type structure in which a densitometer main body and a measuring head are integrated to facilitate handling and carrying. The vertically long densitometer main body 10 has a shape in which the depth of the bottom is wider than that of the top in order to ensure stability during measurement, and is formed of plastic. A display panel 11 is attached to the upper part of the densitometer main body 10 and digitally displays the measured reflection density. On the side of the densitometer body 10, a slide type power switch 1
2, a push-type measurement switch 13, and a zero point correction switch 14 are provided. The zero point correction switch 14 is arranged in the notch 15 so as not to be inadvertently operated in a mode other than the zero point correction mode.

At the bottom of the densitometer body 10, a bottom surface and a recess 16 cut out forward are formed, and a transparent plate 17 is attached so as to close the bottom surface of the recess 16. A measurement aperture 17a is formed substantially at the center of the transparent plate 17, and the measurement aperture 1a is formed.
7a has a frustoconical shape that spreads upward. The reflected light that passes through the inner peripheral surface of the measurement aperture 17a is blocked,
Moreover, in order to make the measurement aperture 17a easy to see, its inner peripheral surface is painted black.

FIG. 1 shows an electric circuit built in the densitometer body. The light-shielding cylinder 20 is arranged at an angle of 45 degrees with respect to the measuring aperture 17a, and the lamp 2
1 is stored. In this projection system, the lamp 2
1, the luminous flux of the illumination light is regulated by the opening formed at the tip of the light shielding tube 20, and the measurement aperture 1
The object 22 to be measured located inside 7a is illuminated in a spot shape.

A light-shielding tube 23 is vertically arranged so as to face the measurement aperture 17a, and a lens 24 is housed therein. In this reflected light measurement system, the light reflected on the surface of the object to be measured 22 in the measurement aperture 17a is regulated by the opening provided at the tip of the light shielding tube 23,
Then, it enters the light receiving element 26 through the lens 24 and the filter 25, and is photoelectrically converted there.

The reference light measuring system includes a light blocking tube 27 that communicates with the light blocking tube 20,
It is composed of a filter 25 and a light receiving element 28,
A part of the illumination light emitted from the lamp 21 is extracted and photoelectrically converted by the light receiving element 28.

The filter 25 is for passing only reflected light in a specific wavelength range, and in this embodiment, a green filter is used to measure the density of magenta color development. Note that the filter 25 is not necessary when measuring the black-and-white density, and the three-color reflection density can be measured by making the filter 25 switchable.

The signals output from the light receiving elements 26 and 28 are sent to logarithmic conversion amplifiers 30 and 31, respectively, where they are amplified and logarithmically converted. The output signals of the logarithmic conversion amplifiers 30 and 31 are subjected to subtraction processing by the subtractor 32 and converted into density signals. This density signal is sent to the A / D converter 33 and converted into a digital signal (measurement data) at a predetermined cycle. The N pieces of measurement data obtained by this digital conversion are C
It is taken in by the PU 34 and stored in the memory 35. The CPU 34 sequence-controls the operation of each unit according to the program stored in the memory 35.

A battery 38 is replaceably loaded in the densitometer body 10, and is connected to a power supply circuit 39 and a battery check circuit 40 via a power switch 12. This power supply circuit 39 is provided when the power switch 12 is ON.
Each part is supplied with a predetermined voltage. In the present embodiment, it is possible to measure about 10,000 times with four AA batteries, but if the number of measurements is exceeded, the voltage will gradually drop. When this voltage drop becomes large, the emission brightness of the lamp 21 and the logarithmic conversion amplifiers 30, 3 are increased.
Since the characteristic of 1 deviates from the design value, it becomes impossible to perform accurate measurement. Therefore, the battery check circuit 40 detects the voltage of the battery 38 and sends a warning signal to the CPU 34 when the voltage drops below a certain value.

A liquid crystal panel is used as the display panel 11, and 3
The digit display 11a and the zero correction mode are set to "ADJ".
Displayed by the display unit 11b indicated by and the one measured in the zero correction mode shows "H density reference value" or "Low density reference value".
A display unit 11c for displaying "I" and "LO" and a battery mark 11d for displaying battery replacement by a symbol mark are provided.

The memory 35 stores a plurality of channels in which a high density reference value and a low density reference value are combined. This channel selection is performed by measuring the high-concentration reference plate and the low-concentration reference plate when the reflection densitometer is shipped, and selecting the closest channel according to the obtained high-concentration reference value and low-concentration reference value. Designated by the circuit 41. In this example, 4
Since one channel is prepared, two DIP switches 41a and 41b are provided.
The channel is designated by the code signal by N and OFF. Reference numeral 42 is a buzzer.

Next, the operation of the above embodiment will be described with reference to FIGS. When the power switch 12 is turned on after holding the densitometer body 10 with one hand, the zero-point measurement mode is entered, as shown in FIG. When the zero point measurement mode is executed, the measurement mode is set and the power switch 12 is turned off.
The object to be measured can be repeatedly measured until FF.

When the zero point correction mode is entered, as shown in FIG. 4, the numeral display portion 1a of the display panel 11, "ADJ" 11b,
"HILO" 11c blinks. Therefore, as shown in FIG. 2, with the densitometer body 10 standing upright, a high-concentration reference plate and a low-concentration reference plate attached to a densitometer storage case (not shown) are measured to correct the zero point. Create the data. That is, when the bottom of the densitometer body 10 is inserted into a predetermined position of the densitometer housing case, the transparent plate 17 attached to the bottom surface of the densitometer body 10 comes into contact with the density reference plate and the projection formed on the densitometer housing case. As a result, the zero point correction switch 14 is turned on and the measurement is started. The measurement of the density reference plate is the same regardless of which is performed first.

As shown in FIG. 5, when the concentration measurement is started, the lamp 21 is turned on for a time T1 (for example, 0.9 seconds). When the lamp 21 is turned on, the spot light whose size is regulated by the light shielding tube 20 passes through the measurement aperture 17a of the transparent plate 17 and illuminates the density reference plate. The light reflected by the density reference plate is used as the measurement aperture 17a.
Through the light shielding tube 23, the lens 24, the filter 25
The light is incident on the light receiving element 26 via and is photoelectrically converted here. On the other hand, a part of the illumination light emitted from the lamp 21 is
The reference light is taken out through the light-shielding cylinder 27, passes through the filter 25, enters the light receiving element 28, and is photoelectrically converted therein.

The signals output from the light receiving elements 26 and 28 are logarithmically converted and amplified by logarithmic conversion amplifiers 30 and 31, and then sent to a subtractor 32, and the difference between them is output as a reflection density signal. When the power switch 12 is turned on, the light receiving elements 26, 28, the logarithmic conversion amplifiers 30, 31, etc. are operating, so that the subtraction circuit 32 outputs the reflection density signal even when the lamp 21 is turned off. However, as will be described later, the reflection density signal is taken out only during the lighting period of the lamp 21.

After starting the lighting of the lamp 21, the CPU 34 fetches the output signal of the battery check circuit 40 and checks the battery before taking out the measurement data in order to check whether the power source is in a normal state. The battery check circuit 40 compares the voltage of the battery 38 with a reference voltage by a comparator, and outputs a binarized warning signal when the voltage is less than a predetermined value. In this case, the CPU 34 stops the execution of the measurement sequence, and the blinking numeral display 11a, "AJD" 11b, "HILO".
In addition to 11c, the battery mark 11b is displayed blinking at a predetermined cycle. Further, the buzzer 42 is driven to give a sound to warn of battery replacement. Here, when the battery is replaced, the zero point correction mode is restored again.

As shown in FIG. 7, when the time T2 (for example, 0.5 seconds) required for stabilizing the emission brightness of the lamp 21 elapses, CP
The U34 drives the A / D converter 33 at a predetermined cycle T3 (for example, 0.1 seconds) and performs A / D conversion a plurality of times, for example, four times. Since the A / D converter 33 has a sampling function, the density signal output from the subtractor 32 is
Since sampling is performed once and converted into a digital signal (measurement data), substantially four measurements are performed. The obtained four measurement data are loaded into the CPU 34 and stored in the memory 35.
Memorized in. When the battery voltage is low, the CPU 34 does not send a conversion command to the A / D converter 33, so the A / D converter 33 does not operate, and thus the measurement data is not captured.

These four measurement data may vary due to fluctuations in the light emission brightness of the lamp 21, transient characteristics of the logarithmic conversion amplifiers 30, 31, etc., noise, etc. The minimum value is cut off, the average value is calculated from the remaining two measurement data, and this is used as the concentration reference measurement value.

Since the low-density reference value and the high-density reference value are designated by the channel selection circuit 41, it is checked which of the measured values obtained by the actual measurement approximates. For example, when it is close to the low-density reference value R _L , it is determined that the low-density reference plate is measured, and “L” on the display unit 11c is displayed.
"O" is displayed. Along with this, the measured value is displayed on the numeric display 1
Digital display is performed on 1a, and "ADJ" 11b is also displayed. These displays blink to indicate that the measurement is in the zero correction mode.

Next, when the bottom surface of the densitometer body 10 is pressed against another concentration reference plate, for example, a high concentration reference plate, the high concentration reference plate is specified by the procedure shown in FIG. Is digitally displayed on the display panel 11, and "HI" is displayed at the same time.
And "ADJ" are also displayed.

When the measurement of the high density reference plate and the low density reference plate is completed by the above procedure, the CPU 34 creates zero point correction data.
The creation of this zero point correction data will be described with reference to FIG. In FIG. 8, the solid line is an appropriate reference density line, the dotted line is a measured density line obtained by actual measurement, and there is a deviation between them. Here, the symbol _RL is a low density reference value preset by the channel designation as the density reference value of the low density reference plate, and _RH is a preset high density reference value. R ₁ is a low-concentration reference measurement value obtained by measuring a low-concentration reference plate,
R ₂ is a high-concentration reference measurement value obtained by measuring the high-concentration reference plate.

When a straight line (shown by a one-dot chain line) passing through the low concentration reference measurement value R ₁ and parallel to the reference concentration line is drawn, the calibrated measurement value R for an arbitrary measurement value R _D is calculated from the following equation.

R = _RD -X-K (1) Here, K is a constant term that is not related to the measured value _RD . On the other hand, X is a coefficient term that increases / decreases according to the measured value R _D , and when the coefficient is α, X = α · R _D. Therefore, equation (1) can be rewritten as follows.

R = _RD -α * _RD -K (2) The coefficient α and the constant K are expressed by the following equations.

When the coefficient α and the constant K are substituted into the equation (2) and rearranged, the following equation (5) is obtained.

The CPU 34 calculates the coefficient α and the constant K from the equations (3) and (4), and stores them in the memory 35 as zero-point correction data. Once this correction data is created and stored,
The CPU 34 drives the buzzer 42 to display that the zero point correction mode is completed. Along with this, the display panel 1
“ADJ” and “HI” displayed in 1 are erased, and blinking drive of the display panel 11 is switched to continuous lighting. In fact, before the display goes into the turn-off cycle,
Since the creation of the zero correction data is completed, the display of the last measured value is substantially continuous lighting.

When measuring the reflection density of the object to be measured 22, as shown in FIG. 2, the bottom surface of the densitometer main body 10 is placed on the object to be measured 22 in a standing state. Next, the object to be measured 22 is observed obliquely from above the recess 16 through the transparent plate 17, and the measurement aperture 17a is aligned so as to match the desired measurement portion. After positioning the measurement aperture 17a, the measurement switch 13 is pressed with a finger to start the concentration measurement of the object 22 to be measured.

As shown in FIG. 6, when the measurement switch 13 is turned on, the lamp 21 emits light for a short time as described above, and during that time, the battery check and a plurality of data acquisitions are sequentially performed, and the measured data is measured from these measurement data. The measured value of the object 22 is obtained. This measured value is calibrated with the correction data obtained in the zero correction mode. That is, the CPU 34 reads the coefficient α and the constant K stored in the memory 35, and uses the calibration formula
Substitute in (2) to calculate calibrated measurements.

For example, the low concentration reference value R _L is 0.05, the high concentration reference value R _H is 1.30, and the low concentration reference measurement value R ₁ is 0.0.
8, and the high-concentration reference measurement value R ₂ is 1.40, the coefficient α and the constant K for calibrating the zero correction data are as follows.

α = 0.05 K = 0.03 When the measured values are 1.00, substituting them into the calibration equation (2) gives R = 0.98, and the calibrated measured values are digitally displayed on the display panel 11. Along with this, the buzzer 42 is driven and the completion of measurement is displayed by sound. The display of the calibrated measurement value is continuously lit, and continues until the previous measurement value is erased by the next measurement. Also, if a printer or the like is connected, data transfer is performed, and necessary conversion can be performed in this printer to print the reflection density value and the converted value.

Although the handy type reflection densitometer that can be operated with one hand has been described in the above embodiment, the present invention separates the densitometer main body having an arithmetic circuit, a display, a power supply circuit and the like from the measuring head, It can be used for a conventional reflection densitometer connected by a cord, and can also be used for a transmission densitometer.

〔The invention's effect〕

As described in detail above, according to the present invention, the reference measurement values obtained by measuring the densities of the low-density reference plate and the high-density reference plate, respectively, and the density preset as the density of these density reference plates Since the zero point correction data is calculated from the deviation from the reference value and stored in the memory and the zero point correction data is used to calibrate the measured value obtained by measuring the measured object, It becomes unnecessary to adjust the position of the meter pointer by operating the adjusting knob as described above, and the zero point correction becomes extremely simple.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electric circuit of a reflection densitometer embodying the present invention. FIG. 2 is an external view showing a handy type reflection densitometer embodying the present invention. FIG. 3 is a flowchart showing the outline of the measurement procedure. FIG. 4 is a flowchart showing the zero point correction mode. FIG. 5 is a flowchart showing the acquisition of measurement data. FIG. 6 is a flowchart showing the measurement mode. FIG. 7 is a timing chart showing the relationship between the lighting of the lamp and the acquisition of measurement data. FIG. 8 is a graph for explaining the zero point correction data. 10 ... Concentration meter body 11 ... Display panel 12 ... Power switch 13 ... Measurement switch 14 ... Zero correction switch 17a ... Measurement aperture 21 ... Lamp 22 ... Object to be measured 26, 28 ... Element 30, 31 ... Logarithmic conversion amplifier 41 ... Channel selection circuit.

Claims (1)

[Claims] 1. A low-concentration reference measurement value R ₁ and a high-concentration reference measurement value R obtained by measuring the densities of a low-concentration reference plate having a low-concentration reference value R _L and a high-concentration reference plate having a high-concentration reference value R _H , respectively. Got ₂ and
The following formula By obtaining the coefficient α and the constant K of the zero-point correction data, with respect to the density measurement value R _D of the object to be measured, R = R _D - [alpha] R _D - wherein to obtain a calibrated measured value R by performing the correction of K Concentration calibration method.