JP2788370B2 - Densitometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention illuminates a photograph, a printed matter, etc. with light, and receives a reflected light beam from the object to be measured.
The present invention relates to a densitometer that measures the reflection density of an object to be measured based on the received light intensity.

[0002]

2. Description of the Related Art Geometric optical conditions of a densitometer used for measuring the reflection density of a photograph, a printed matter or the like are specified by JIS and the like. For example, a density is measured by irradiating an object to be measured (hereinafter, referred to as a sample) with light, receiving a reflected light beam from the sample, and measuring the reflection density of the sample from the intensity of the reflected light. Normally, the solid angle of light at the time of irradiation and light reception is set within 5 degrees, and the light is irradiated perpendicularly to the surface of the sample, and the reflected light of 45 degrees is received, or A method of irradiating light at 45 degrees to the surface and receiving vertical reflected light is adopted.

In a densitometer used for measuring the reflection density, a light beam reflected from a sample is received by a light-receiving sensor, and a density value is determined based on the intensity of the reflected light. The stability of the light intensity of a light source lamp (hereinafter, referred to as a light source lamp) for performing measurement has an important effect on the accuracy of measurement, but the light intensity of the light source lamp often fluctuates.

The factors that cause the light intensity of the light source lamp to fluctuate are: (1) fluctuation in the supply voltage to the light source lamp; (2) temporal change in the light intensity of the light source lamp itself; It can be considered that the light intensity of the light source lamp fluctuates from the rising characteristic until the light intensity of the light source lamp reaches a predetermined value and stabilizes.

Conventionally, the following measures have been taken to cope with the above-mentioned factors that cause the light intensity of the light source lamp to fluctuate. That is, with respect to the fluctuation of the supply voltage to the light source lamp in (1), the voltage is stabilized in the densitometer so that a constant voltage is always supplied to the light source lamp even if the voltage of the main power supply of the densitometer fluctuates. Provide a circuit.

With respect to (2) the temporal change of the light intensity of the light source lamp itself, for example, the luminous intensity of the light source lamp is measured periodically or before the measurement is started, and the output correction (calibration) of the light receiving sensor is performed based on the result. Or use a light source lamp with relatively little change in light intensity over time.

[0007] The rising characteristic of the light intensity of the light source lamp (3) has a property that it changes depending on, for example, the tube temperature, the measurement environment temperature, the total lighting time, etc. of the light source lamp before the light source lamp is energized. Further, the light intensity of the light source lamp is stabilized as time elapses after lighting. However, it takes a very long waiting time for the light intensity of the light source lamp to stabilize to such an extent that the measurement error of the density value caused by the fluctuation of the light intensity of the light source lamp can be sufficiently ignored.

Accordingly, with respect to the fluctuation of the rising characteristic of the light intensity of the light source lamp of (3), after turning on the main power of the densitometer, it is necessary to delay the measurement start time until the densitometer becomes usable. Alternatively, the densitometer is set so that the light source lamp is always turned on when the main power of the densitometer is turned on, or a light source lamp that requires a relatively short time to start up is used.

[0009]

However, the conventional methods for coping with the above-mentioned factors (1) to (3) have the following problems.

First, in the conventional method for coping with the factor (1), a constant voltage is always supplied to the light source lamp even if the operating environment temperature of the densitometer or the voltage of the main power supply of the densitometer fluctuates. A high-precision voltage stabilizing circuit must be provided in the densitometer, but this increases the manufacturing cost of the densitometer.

Next, in the conventional method for coping with the factor (2), the luminous intensity of the light source lamp is measured, for example, periodically or before the measurement is started, and the output of the light receiving sensor is corrected (calibrated) based on the result. This significantly deteriorates the operability of the densitometer, and the cost of manufacturing the densitometer is increased because the light source lamp whose light intensity changes relatively little over time is expensive.

Further, in the method of the related art for coping with the factor (3), after turning on the main power of the densitometer, delaying the measurement start time until the densitometer becomes usable requires a long time for the measurement. Therefore, setting the densitometer so that the light source lamp is always lit when the main power of the densitometer is turned on shortens the life of the light source lamp and starts up. A light source lamp that requires a relatively short time is expensive, and thus increases the manufacturing cost of the densitometer.

Therefore, it is urgently necessary to solve the above-mentioned problem and to manufacture a densitometer capable of sufficiently reducing the measurement error of the density value caused by the fluctuation of the light intensity of the light source lamp to a negligible level. I have.

[0014]

According to a first aspect of the present invention, there is provided a densitometer for irradiating an object to be measured with light and receiving a reflected light beam from the object to be solved. A light source for vertically irradiating light to an object to be measured at a central portion of a substantially cylindrical measuring head, wherein the light intensity of the light source is and it has a detection means for detecting, from the measurement object
The reflected light beam is reflected toward the center of the measuring head to make a polygon mirror.
Equal to the number of annular spherical mirrors and optical sensors
Measures reflected light from the above-mentioned annular spherical mirror
A multi-sided surface that reflects light toward the edge of the head and collects light on the optical sensor
A mirror surrounding the light source, and a plurality of optical sensors surrounding the light source for measuring the red, green, and blue light receiving intensities of the reflected light beam from the object to be measured, and the reflected light beam. When light is received, a correction means for correcting the received light intensity with the light intensity of the light source is provided.

[0015]

According to the first aspect of the present invention, the optical path length of the light (reflected light flux) from the light source to the optical sensor via the object to be measured is determined by:
Since the light sensors for measuring the received light intensity of red, green, and blue can be set uniformly, the light receiving conditions of the light sensors, that is, the measuring conditions of each color, can be set the same. Further, of the reflected light from the object to be measured, all reflected light beams, for example, at 45 degrees with respect to the normal direction of the surface of the object to be measured can be used for measuring the received light intensity. Therefore, the density value of each color can be accurately measured. Further, according to the above configuration, it is possible to prevent reflected light beams (for example, green and blue) other than the reflected light beam (for example, red) necessary for measuring the received light intensity from being received by the optical sensor. Since the amount of the reflected light beam received by each optical sensor can be equalized, the density value of each color can be measured under the same measurement condition, and the density value of each color can be measured more accurately. it can. Further, in the above configuration, the influence of the fluctuation of the light intensity of the light source lamp on the measurement accuracy of the density value can be reduced to a negligible extent, so that the stability over time of the measurement accuracy of the density value is improved. The number of times that the output correction (calibration) is performed is small, and the operability of the densitometer can be significantly improved.

Also, after the light source lamp is turned on, it is possible to start measuring the density before the light intensity of the light source lamp is sufficiently stabilized, so that the measuring time required for measuring the density is greatly reduced. Can be.

Furthermore, since the lighting time of the light source lamp can be greatly reduced, the life of the light source lamp is extended, and a voltage stabilizing circuit for stabilizing the voltage supplied to the light source lamp is unnecessary or extremely simple. The measurement accuracy of the density value can be ensured without increasing the manufacturing cost of the densitometer.

Therefore, it is possible to manufacture a densitometer capable of sufficiently reducing the measurement error of the density value caused by the fluctuation of the light intensity of the light source lamp to a negligible level.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In this embodiment, a color densitometer will be described as an example of a densitometer according to the present invention.

As shown in FIG. 5, the color densitometer according to the present embodiment has a measurement circuit section 1, a measurement head 2 and a DC power supply 5 which is a main power supply of the color densitometer built in an outer case 3, which will be described later. I have. A measurement stand 4 is provided on the lower surface 3b side of the outer case 3 where the measuring head 2 is exposed, so as to face the lower surface 3b, and a color densitometer is provided on a rear side surface 3c of the outer case 3. And a host computer (not shown), a host interface cable 6 for transferring measurement data from the color densitometer to the host computer, and a switch 11 for a main power supply of the color densitometer are provided.

The DC power supply 5 is, for example, a dry battery of 5 V or less.
Power may be obtained from outside the color densitometer via a converter or the like.

The measuring stand 4 includes a lower surface 3 of the outer case 3.
b, and has a measurement surface 4b large enough to cover the entire lower surface 3b of the outer case 3. The measuring stand 4 and the outer case 3 are connected to the measuring stand 4.
Rear connecting portion 4a and rear side connecting portion 3d of outer case 3
Are rotatably attached in the direction of AA 'in FIG.

When measuring the concentration of an object to be measured (hereinafter referred to as a sample), the measuring stand 4 is attached to the outer case 3.
For use in a state where the measurement stand 4 is closed with respect to the outer case 3, a portion of the measurement surface 4 b of the measurement stand 4 facing the measurement head 2 when the measurement stand 4 is closed with respect to the measurement head 2 is used to position a sample (not shown). Is provided.

Next, on the upper surface 3a of the outer case 3, FIG.
As shown in the figure, a zero adjustment key 7 operated when zero density adjustment of the densitometer is performed, a measurement key 8 for starting density measurement, and an error occurs when an error occurs during the density measurement by turning on or blinking. And a ready indicator 10 for lighting and displaying that the densitometer is in a usable state after the main power is turned on.

Next, the measuring head 2 will be described below with reference to FIGS. In addition, as the measurement head 2 of the color densitometer according to the present embodiment, the solid angle of light at the time of irradiation and light reception is set within 5 degrees, and light is irradiated perpendicularly to the surface of the sample. A method for receiving reflected light will be described.

The measuring head 2 has a substantially cylindrical shape and comprises an irradiation optical system 12, a light receiving optical system 13, and a filter 14, as shown in FIG. The irradiation optical system 12 is installed at the center of the measuring head 2, the light receiving optical system 13 is formed in a cylindrical shape so as to surround the irradiation optical system 12, and the filter 14 is
It is installed between the light receiving optical system section 13 and an optical sensor 22 described later.

The irradiation optical system 12 includes a light source lamp 12
a, lamp house 12b, projection lens 12
c, a light guide 12d and an irradiation optical system member 12e. The light source lamp 12a is housed in a lamp house 12b provided at a central portion in the irradiation optical system member 12e, and is installed downward so that the central axis of the light source lamp 12a is perpendicular to the surface of the sample 15. Have been.

The projection lens 12c for condensing the light so that the light emitted from the light source lamp 12a irradiates the measurement area 15a on the surface of the sample 15 at a solid angle within 5 degrees. It is adjusted and installed at an optimal position between 12a and the sample 15. The projection lens 12c is sandwiched between a pedestal 12h provided inside the irradiation optical system member 12e and a pressing plate 12g so as not to shift from a predetermined position.

Further, a light guide 12d having a circular opening 12i in the center is used to transmit light condensed by the projection lens 12c to a measurement area 15 on the surface of the sample 15.
It is provided at the lower end of the irradiation optical system member 12e so as to irradiate only inside a.

The measurement area 15a on the surface of the sample 15
The measurement opening 2a provided with a circular opening having a size corresponding to the size of the sample so that light from the outside other than the light emitted from the light source lamp 12a does not enter the light receiving optical system 13 described later. 15 is provided at the lower end of the lower housing part 2b of the measuring head 2 that is in contact with the measuring head 15.

The lamp house 12b has an opening 12j for an optical fiber for detecting the light intensity of the light source lamp 12a, and the light entering the opening 12j for the optical fiber passes through the optical fiber 16. Then, the light is introduced into the light sensor 21 for the light source lamp installed on the upper part 2 c of the housing of the measuring head 2. The opening position of the optical fiber opening 12j and the installation position of the optical fiber 16 may be provided at any position in the irradiation optical system 12 as long as the measurement of the concentration of the sample 15 is not hindered. The lamp light sensor 21 is integrated with the measurement circuit unit 1 and its operation will be described later.

Next, the light receiving optical system section 13 is formed in a cylindrical shape so as to surround the irradiation optical system section 12, and includes a mask plate 13a, an annular spherical mirror 13b, and a triangular mirror 13c. Mask plate 13a
Indicates that the light emitted from the light source lamp 12a
Of the reflected light reflected on the surface measurement area 15a, a reflected light flux 17 of 45 ± n degrees with respect to the normal direction of the sample 15 surface.
Only is extracted and introduced into the annular spherical mirror 13b. still,
The above n defines the solid angle of the reflected light, and usually an angle of 5 degrees or less is used.

The annular spherical mirror 13b reflects the reflected light flux 17 passing through the mask plate 13a and focuses the reflected light flux 17 on the triangular mirror 13c. Triangular mirror 13c
Divides the reflected light flux 17 condensed by the annular spherical mirror 13 b into three and introduces the light into the filter unit 14.

Next, the filter section 14 controls the reflected light beam 17
An infrared cut filter 14a for removing infrared rays therein,
And red, green, and blue color filters 14b for extracting red, green, and blue from the reflected light flux 17, respectively.
, And the infrared cut filter 14a
And the red color filter 14b to extract red in the reflected light flux 17, and combine the infrared cut filter 14a and the green color filter 14b to reduce the green color in the reflected light flux 17 to the infrared cut filter 14a and the blue light. By combining the color filters 14b, blue in the reflected light beam 17 is extracted. Therefore, as shown in FIG. 2, the filter section 14 is divided into three places corresponding to these three colors and installed at a predetermined position on the housing upper portion 2 c of the measuring head 2.

The reflected light flux 17 divided by the triangular mirror 13c is divided into three color filters 14b.
Red, green, and blue, respectively, are extracted, and then each of the red, green, and blue optical sensors 22 is extracted.
Introduced in ... Therefore, as shown in FIG. 2, the optical sensors 22 are also provided at predetermined positions on the upper portion 2c of the housing of the measuring head 2 so as to correspond to the filter section 14. There is no particular limitation on the order in which the red, green, and blue optical sensors 22 are arranged. Each optical sensor 22 is integrated with the measurement circuit unit 1 and its operation is performed. Will be described later.

Next, the measurement circuit section 1 will be described below with reference to FIG. The measurement circuit unit 1 includes a power supply circuit unit 3
1, a sensor signal processing unit 32 and a device control unit 33, which are installed on a substrate (not shown).

First, the power supply circuit section 31 comprises a power supply control section 31a, a DC-DC converter 31b, a constant voltage generating circuit 31c for the light source lamp 12a, and two constant voltage circuit sections 31d and 31e. The DC voltage supplied from the DC power supply 5 which is the main power supply of the color densitometer is
DC-DC converter 3 via power supply control unit 31a
1b and constant voltage generating circuit 31c for light source lamp 12a
To supply.

The power supply control unit 31a includes a switch 1
1 to turn on / off the main power supply of the color densitometer, detect a voltage drop of the DC power supply 5 and notify an input / output device 33f described later, and further, a reset signal to the device control unit 33 described later. It has the function of generating.

The DC-DC converter 31b
Boosts the voltage supplied from the DC power supply 5 and supplies the boosted voltage to the two constant voltage circuit units 31d and 31e. The constant voltage circuit units 31d and 31e convert the voltage boosted by the DC-DC converter 31b to, for example, 5V and supply the converted voltage to the sensor signal processing unit 32 and the device control unit 33.

The constant voltage generating circuit 31c for the light source lamp 12a has a very simple configuration.
The light source lamp 12a is provided so that a substantially constant voltage is always applied to the light source lamp 12a even when the voltage supplied from the DC power supply 5 fluctuates.

Next, the sensor signal processing section 32 includes an optical sensor 22, an optical sensor 21 for a light source lamp, a sensor signal amplifier circuit 32a, an analog multiplexer 32b, a logarithmic conversion circuit 32c, an offset removal circuit 32d, and an A / D converter.
The conversion circuit 32e has a function of processing an output signal from the optical sensors 22 that receive the reflected light beam 17 from the sample 15 and transmitting the processed signal to the device control unit 33.

First, the reflected light beam 17 from the sample 15
As described above, after any one of red, green, and blue is extracted by the filter unit 14 installed on the upper housing portion 2c of the measurement head 2, each of the red, green, and blue colors is taken out. Are introduced into the optical sensors 22. And
The optical sensors 22 measure the light intensities of the extracted lights, and output the results as analog signals to the corresponding sensor signal amplifier circuits 32a. At the same time, the light emitted from the light source lamp 12a is also introduced into the light sensor 21 for the light source lamp via the optical fiber 16 to measure the light intensity, and the result is output as an analog signal to the corresponding sensor signal amplifier circuit 32a. I do.

The analog signals output from the optical sensors 22... And the light source lamp optical sensor 21 are amplified by the corresponding sensor signal amplifier circuits 32a to a level required for signal processing in the subsequent stage.

The analog signal amplified by the sensor signal amplifying circuits 32a... Together with the data signal 33g of the calibration sample having a known reflection density of the sample, which is required in the measurement data processing described later. −
The signal is input to a multiplexer (multiplexing device) 32b.
The calibration sample data signal 33g is stored in an EEPROM 33e described later.

The analog multiplexer 32b combines the signals from the sensor signal amplifier circuits 32a, etc. into one and outputs the measured data directly to an A / D converter (analog / digital converter) 32e, or
The signal is output to the A / D converter 32e via the logarithmic conversion circuit 32c.

The logarithmic conversion circuit 32c is provided to guarantee the accuracy of the subsequent analog / digital conversion in the entire measurable density range. The logarithmic conversion circuit 32c includes an offset removal circuit 32d and a sensor. Signal processing unit 3
2 are connected to remove a circuit offset in each analog circuit.

The measurement data of the analog signal input directly to the A / D converter 32e from the analog multiplexer 32b or via the logarithmic conversion circuit 32c is converted into a digital signal by the A / D converter 32e. The data is output and read by the MPU 33a of the device control unit 33.

Next, the device control section 33 includes an MPU (microcomputer) 33a, a program ROM (read only memory) 33b, a working RAM (random write / read memory) 33c, a host interface 33d, and gamma correction of measured data. (Electrically erasable and rewritable read-only memory) 33e and an input / output device 33f in which a gamma correction table and the like for performing
And has a function of controlling a measurement process of the densitometer, processing measurement data (calculating a density value), an interface with a host computer (not shown), and performing various error processing.

The MPU 33a has a program ROM 3
A program such as control of these measurement processes stored in advance in 3b is executed using the working RAM 33c to control each unit in the measurement circuit unit 1.

That is, the measurement data converted into a digital signal by the A / D converter 32e and read by the MPU 33a of the device control unit 33 is first stored in the working RAM 33c. The MPU 33a stores the work RAM 3
3c and the EEPROM 33 in advance.
The density value is calculated based on the data of the calibration sample whose reflection density of the sample is known and the gamma correction table stored in e. The calculated density value is transferred to the host computer via the host interface 33d.

The input / output device 33f transmits the operation of the measurement key 8 and the zero adjustment key 7 to the MPU 33a, and turns on the ready indicator 10 indicating that the densitometer can be used. And a function of turning on or blinking the error indicator 9 when various errors are detected during the measurement of the density.
Further, it has a function of selecting various data input to the analog multiplexer 32b and outputting the selected data to the A / D converter 32e.

In the measuring circuit section 1 having the above configuration, the measuring process of the densitometer is performed in the following procedure.

First, after the sample 15 is set at a predetermined position by the positioning part 4c of the measuring stand 4, the measurement is started by operating the measuring key 8 or a command from the host computer. Then, the light source lamp 12
In a, a voltage is applied by the constant voltage generation circuit 31c to irradiate the sample 15 with light. After the elapse of the rising time of the light intensity of the light source lamp 12a, the reflected light flux 17 from the sample 15 is measured by the optical sensors 22.

The time from when the light source lamp 12a is turned on to when the reflected light flux 17 from the sample 15 is measured by the optical sensors 22 is 1 second in consideration of the operability of the densitometer and the reduction of the measurement time. It is desirable to be within.

However, the light intensity of the light source lamp 12a within one second after the light source lamp 12a is turned on is set to a level necessary for performing the subsequent signal processing with the reflected light beam 17 from the sample 15, so that the light sensors 22 ... Although it has risen to a state where an output level can be obtained, it has not yet reached a stable state at this point. That is, at this point, the light source lamp 1
The light intensity 2a changes depending on, for example, the tube temperature, the measurement environment temperature, the total lighting time, and the like.

Therefore, in order to eliminate the influence of the change on the measurement accuracy of the density, the reflected light beam 17 from the sample 15 is measured by the optical sensors 22 and at the same time, one of the light beams emitted from the light source lamp 12a is measured. The portion is measured by the light source lamp light sensor 21 via the optical fiber 16.

When the density value is calculated by the MPU 33a, the signal from the optical sensor 22 is corrected using the signal from the optical sensor 21 for the light source lamp, and the measured data and the data stored in the EEPROM 33e in advance are corrected. The density value is calculated based on the data of the calibration sample and the gamma correction table.

Next, a method of processing the measurement data in the sensor signal processing section 32 will be described below with reference to FIG.

In the light emitted from the light source lamp 12a, the light intensity of the light reflected by the sample 15 is defined as RI, and the light source measured at this time by the light source lamp optical sensor 21 via the optical fiber 16 is used. Lamp 12
Let I be the light intensity of a. The light intensity RI of the reflected light is converted into a signal having an intensity proportional to the intensity by the optical sensor 22 and then amplified by the sensor signal amplifier circuits 32a to a level suitable for the subsequent signal processing. Here, the output signal of the sensor signal amplifier circuits 32a is the light intensity R of the reflected light.
It is a signal having a strength proportional to I, and G ₁ · RI when the proportional coefficient is G ₁ . In addition, actually, the proportional coefficient G ₁
Are different for each of the red, green, and blue light sensors 22..., But the same value will be considered for the sake of simplicity.

Similarly, the light intensity I of the light source lamp 12a is
After being converted by the light source lamp optical sensor 21 into a signal having an intensity proportional to the intensity, the sensor signal amplifying circuit 32a
Thus, the signal is amplified to a level suitable for subsequent signal processing.
Here, the output signal of the sensor signal amplification circuit 32a is a signal having an intensity proportional to the light intensity I of the light source lamp 12a,
Assuming that the proportional coefficient is G ₂ , G ₂ · I is obtained.

Next, G ₁ · RI and G ₂ · I are
Along with data REF _1, REF ₂ calibration samples for erasing proportionality factor K ₁ of the subsequent log conversion circuit 32c analogue - is input to the multiplexer 32b. G ₁
・ The data of the calibration sample for RI is REF ₁ , G ₂
Data of the calibration samples for I is a REF _2.
These four data are selected by the input / output device 33f and input to the channel A of the A / D conversion circuit 32e or directly to the channel B of the A / D conversion circuit 32e via the sequential logarithmic conversion circuit 32c.

[0062] Incidentally, in general, input-output relation of the logarithmic conversion circuit 32c is inputted to in, the output out, to represent the proportional coefficient in _{K 1, out = K 1 ×} log (in) ...... (1) Also, In general, the A / D conversion circuit 32e inputs AD,
When the output is represented by D and the proportional coefficient is represented by K ₂ , D = K ₂ × AD (2)

Therefore, the converted data of the above four data by the A / D conversion circuit 32e is converted by the converted digital signal D ₂ ... G ₂ .I signal channel A by the channel A of the D ₁ ... G ₁ .RI signal. Converted digital signal D ₃ ... Converted digital signal based on channel A of REF ₁ signal D ₄ ... Converted digital signal based on channel A of REF ₂ signal D ₅ ... Converted digital signal based on channel B of REF ₁ signal D _6. Expressed as a converted digital signal by channel B of _two signals, the proportional coefficient K _{1 of the} above equations (1) and (2)
The following two operations are performed in order to eliminate K ₁ and K ₂ , and their values are set to F ₁ and F ₂ , respectively.

F ₁ = (D ₄ −D ₁ ) / (D ₄ −D ₃ ) (3) F ₂ = (D ₄ −D ₂ ) / (D ₄ −D ₃ ) (4) Calculating F ₁ from (1) to (4), F ₁ = {K ₁ K ₂ · log (REF ₂ ) −K ₁ K ₂ · log (G ₁ · RI)} / ｛K ₁ K ₂ Log (REF ₂ ) −K ₁ K ₂ · log (REF ₁ )｝ = log (REF ₂ / G ₁ · RI) / log (REF ₂ / REF ₁ ) = log (D ₆ / K ₂ G ₁ · RI ) / Log (D ₆ / D ₅ ) (5) From equation (5), log (G ₁ · RI) = F ₁ · log (D ₅ / D ₆ ) + log (D ₆ ) + log (K ₂ ) ... (6) Similarly, the following equation (7) is derived by calculation of F _2. log (G ₂ · I) = F ₂ · log (D ₅ / D ₆ ) + log (D ₆ ) + log (K ₂ ) (7) Equations (6) and (7) can be transformed as follows. . RI = S × 10 ^{log (K2)} / G ₁ (8) I = L × 10 ^{log (K2)} / G ₂ (9) where S = 10 ^{F1 log (D5 / D6) + log (D6 )} (10) L = 10 ^{F2 log (D5 / D6) + log (D6)} (11) Next, the above equations (8) and (9) obtained by measuring a calibration sample having a known reflection density. The right side of) is RI
ref and Iref, and the right sides of the above equations (8) and (9) obtained by measuring the sample 15 are RIs and
Is. Further, the density value of the sample 15 is set to DENs,
The concentration value of the calibration sample is DENref.

Generally, the concentration value of a sample is expressed by the following equation (1)
Required in 2). DENs = DENref + log (RIref / RIs) (12) In order to add the light intensity of the light source lamp 12a to the above equation (12), for example, the light intensity RI of the reflected light is converted to the light intensity I of the light source lamp 12a. And the density value of the sample is calculated as in the following equation.

DENs = DENref + log (RIref × Is / RIs × Iref) (13) In this way, the equation (12) for calculating the concentration value of the sample is obtained.
By adding a term for the light intensity I of the light source lamp 12a to the above, the deterioration of the measurement accuracy due to the fluctuation of the light intensity of the light source lamp is improved.

The method of correcting the light intensity fluctuation of the light source lamp is not limited to the method of the above equation (13), but may be measured by correcting the light intensity of the reflected light so as to be inversely proportional to the light intensity of the light source lamp. What is necessary is just to perform the correction method according to the system.

As described above, the color densitometer having the above configuration has the light sensor for the light source lamp for detecting the light intensity of the light source lamp for irradiating the sample with light, and also receives the reflected light beam from the sample, and Since the sensor signal processor corrects the received light intensity with the light intensity of the light source lamp, even if the light intensity of the light source lamp varies, the sensor signal processor accurately measures the reflection density of the sample. It has become possible.

[0069]

As described above, the densitometer according to the first aspect of the present invention has a light source for vertically irradiating the object to be measured with light at the center of the substantially cylindrical measuring head. Has detection means for detecting light intensity, and reflection from the object to be measured
Reflects the light beam toward the center of the measuring head and focuses it on a polygon mirror
And the number of surfaces equal to the number of optical sensors
Measuring head for measuring the reflected light flux from the annular spherical mirror
Polygon mirror that reflects light in the peripheral direction of the light and focuses it on the optical sensor
Having a plurality of optical sensors surrounding the light source for measuring the red, green, and blue light receiving intensities of the reflected light beam from the object to be measured , and receiving the reflected light beam. In this case, the light receiving intensity is corrected by the light intensity of the light source.

Therefore, the light receiving condition of the optical sensor, that is,
The same color measurement conditions can be set. In addition,
In the reflected light from the object, the direction of the normal to the surface of the object
For example, measurement of the received light intensity of all reflected light beams at 45 degrees
Can be provided. In addition, measuring the received light intensity
Reflected light (for example, red) other than the required reflected light (for example, red)
(Green / blue) is not received by the optical sensor
And the amount of reflected light flux received by each optical sensor is equalized.
The same measurement of the density value of each color
It can be measured under conditions. Therefore, the density value of each color
It can be measured accurately. In addition, since the influence on the measurement accuracy of the density value due to the fluctuation of the light intensity of the light source lamp can be reduced to a negligible extent, the stability of the measurement accuracy of the density value with time is improved, and thus the output correction (calibration) of the light receiving sensor ) Is performed less frequently, and the operability of the densitometer can be significantly improved.

Further, after the light source lamp is turned on and before the light intensity of the light source lamp is sufficiently stabilized, the measurement of the density can be started, so that the measurement time required for the measurement of the density can be greatly reduced. Can be.

Further, since the lighting time of the light source lamp can be greatly reduced, the life of the light source lamp is extended, and a high-precision voltage stabilizing circuit for stabilizing the voltage supplied to the light source lamp is not required. The measurement accuracy of the concentration value can be ensured without increasing the manufacturing cost of the meter.

Accordingly, an effect is obtained that it is possible to manufacture a densitometer capable of reducing the measurement error of the density value caused by the fluctuation of the light intensity of the light source lamp to a sufficiently negligible level.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a measuring head of a densitometer according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a measuring head of the densitometer.

FIG. 3 is a block diagram of a measurement circuit unit of the densitometer.

FIG. 4 is a block diagram of a sensor signal processing section of a measurement circuit section of the densitometer.

FIG. 5 is a side view of the densitometer.

FIG. 6 is a front view of the densitometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measuring circuit part 2 Measuring head 2a Measuring opening 2b Lower case 2c Upper case 3 Outer case 4 Measurement stand 5 DC power supply 6 Host interface cable 7 Zero adjustment key 8 Measurement key 9 Error indicator 10 Ready indicator 11 Switch 12 Irradiation optics System unit 12a Light source lamp 12c Projection lens 12d Light guide 12j Optical fiber opening 13 Light receiving optical system unit 13a Mask plate 13b Annular spherical mirror 13c Triangular mirror 14 Filter unit 14a Infrared cut filter 14b Color filter 15 Sample 16 Optical fiber 17 Reflected light amount 21 Light source Lamp light sensor 22 Light sensor 31 Power supply circuit unit 31a Power supply control unit 31b DC-DC converter 31c Constant voltage generation circuit 31d Voltage circuit section 32 Sensor signal processing section 32a Sensor signal amplification circuit 32b Analog-multiplexer 32c Logarithmic conversion circuit 32d Offset removal circuit 32e A / D conversion circuit 33 Device control section 33a MPU 33b Program ROM 33c Working RAM 33d Host interface 33e EEPROM 33f I / O device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 21/00-21/61 G01J 3/00-3/52

Claims (1)

(57) [Claims] 1. A densitometer of a system for irradiating an object with light, receiving a reflected light beam from the object, and measuring the reflection density of the object based on the intensity of the received light. A light source for vertically irradiating light is provided at a central portion of a substantially cylindrical measuring head, and a detecting means for detecting the light intensity of the light source is provided, and a reflected light beam from an object to be measured is measured.
An annular sphere that reflects light toward the center of the head and focuses it on a polygon mirror
With a surface mirror and the number of surfaces equal to the number of optical sensors,
Reflected light beam from annular spherical mirror
A polygon mirror for reflecting light to the optical sensor and condensing the light on the optical sensor,
A manner surrounding the has a plurality of optical sensors for measuring the red, green and blue light reception intensity of the reflected light beam from the object to be measured so as to surround the light source, and, when receiving a reflected light beam, the What is claimed is: 1. A densitometer, comprising: correction means for correcting the received light intensity with the light intensity of the light source.