JP3272471B2 - Concentration measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentration measuring device.

[0002]

2. Description of the Related Art When evaluating the quality of a fine image such as a laser printer image or a halftone dot image for printing, it is necessary to measure the density of the fine portion of the image with high accuracy and to measure the density distribution on the image plane. There is.

In order to measure the density distribution on the image plane, a process of measuring the density while moving on the image plane is required. This process is generally called a density trace, and measures the density of a minute portion. The case is particularly referred to as concentration microtrace.

Conventionally, a microdensitometer is known as a device for measuring the concentration of a fine portion, and a spectrophotometer, which is another device, measures transmittance and absorbance with respect to the wavelength of light. The area of the part is relatively large.

[0005]

However, although the microdensitometer can perform micro tracing, its error is about ± 0.02D, and the accuracy of concentration measurement is insufficient. As the visual characteristics of the naked eye are already known,
A density difference of 0.004D can be identified at intervals of approximately 1 mm. For this reason, a microdensitometer having a measurement error of ± 0.02D may be regarded as having the same density even if there is a density difference that can be recognized by the naked eye.

On the other hand, the spectrophotometer has an error of ± 0.0
Although it is about 02D and the accuracy of density measurement is sufficient,
The range to be measured is a wide range of about 10 mm in diameter, and there is a drawback that micro tracing cannot be performed. Further, the spectrophotometer requires switching of a light beam by a chopper or the like and AC signal processing, and the configuration and processing are complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to realize a high-precision concentration measuring apparatus capable of measuring a concentration microscopically and performing micro tracing at a low cost with a simple configuration. .

[0008]

In order to achieve the above object, the present invention provides a laser beam irradiating means for irradiating an image sample whose density is to be measured with a fine laser beam, and irradiating a laser beam on the image sample. A moving means for moving the laser light irradiating means or the image sample so as to move the position and remove the image sample from the optical path of the laser light, and a position measuring means for measuring a laser light irradiating position on the image sample; A light amount detecting means for detecting a light amount of the laser light transmitted through the image sample or a laser light reflected by the image sample; a light amount detected by the light amount detecting means; and a light amount fluctuation pattern of the laser light irradiating means. At a predetermined timing, the image sample is removed from the optical path of the laser light by the moving means, and the laser light emitted from the laser light irradiating means is irradiated with the light quantity detection means. Calculating means for calculating the density of the image sample based on the light amount of the laser light from the laser light irradiating means detected by the light amount detecting means when the light is guided by the light amount detecting means, and the laser light measured by the position measuring means. The density measuring device is configured to obtain the density distribution of the image sample from the irradiation position and the density of the image sample calculated by the calculation means.

[0009]

According to the present invention, according to the above construction, the calculating means controls the moving means at a predetermined timing based on the light quantity of the transmitted or reflected light of the image sample detected by the light quantity detecting means and the light quantity variation pattern of the laser light irradiating means. The density of the image sample is calculated based on the light amount of the laser light from the laser light irradiation unit detected by the light amount detection unit when the image sample is removed from the optical path of the laser light.

[0010] In addition, the moving means moves the laser beam irradiation position on the image sample, thereby enabling micro trace of the density.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a concentration measuring apparatus according to the present invention.

Reference numeral 1 denotes a He-Ne laser, which emits a laser beam 2 indicated by a broken line. The cylinder 3 indicated by a dashed line is provided around the optical path of the laser light 2 to prevent the laser light 2 from being refracted under the influence of air fluctuation and changing the optical path. Reference numeral 4 denotes a half mirror, which reflects a part of the total light amount of the laser beam 2 and transmits the rest.

The laser beam 2 reflected by the half mirror 4 is received by a photodiode 17, and the photodiode 17 generates a current corresponding to the amount of the received laser beam 2. This current is voltage-converted and amplified by the amplifier 18, converted to a digital value by the A / D converter 19, and then input to the CPU 20.

On the other hand, the laser beam 2 transmitted through the half mirror 4 is deformed by the cylindrical lens 5 into a vertically elongated slit shape, and then the slit 6 has a portion where the amount of light in the upper and lower portions of the vertically elongated slit shape is weak. Is cut and the side is 2
The light beam becomes 0 μm and the vertical length is 1000 μm. By using the vertically elongated slit light as described above, the granular noise of the sample is suppressed. Also, if the sample surface is set slightly before the beam waist of the lateral diameter (for example, the He-Ne laser 1 side of about 0.1 mm), the sample is irradiated with a converged beam, so that the granular noise is more effectively reduced. Can be suppressed.

Reference numeral 7 denotes a single-axis mechanical stage,
In response to a command from U20, it is controlled by the stage controller 12 to move in the left-right direction. The sample 9 is fixed to the sample holder 8 on the uniaxial mechanical stage 7, and the sample 9 is moved left and right by moving the uniaxial mechanical stage 7 left and right.
The sample 9 can be microtraced, and the sample 9 can be removed from the optical path of the laser beam 2. The position (moving distance) of the uniaxial mechanical stage 7 is precisely measured by the laser length measuring device 11 and reported to the CPU 20. The sample 9 used in the present embodiment is in the form of a film, and the density of the sample 9 is measured based on the amount of the laser beam 2 transmitted through the sample 9.

The laser beam 2 that has passed through the slit 6
And is received by the photodiode 10. The photodiode 10 generates a current corresponding to the amount of the received laser beam 2. This current is voltage-converted and amplified by the amplifier 13, converted to a digital value by the A / D converter 14, and then input to the CPU 20. The current is also voltage-converted and amplified by the amplifier 15, and is converted by the A / D converter 16. After being converted into a digital value, it is input to the CPU 20.

The amplifiers 13 and 15 have different amplification factors. In this embodiment, the amplifier 15 has an amplification factor 10 times that of the amplifier 13. The amplifier 13 amplifies the output current of the photodiode 10 when the sample 9 is removed from the optical path of the laser light 2, while the amplifier 15 inserts the sample 9 into the optical path of the laser light 2 and This is for amplifying the output current of the photodiode 10 when tracing.

This is because there is a large difference in the amount of light between the laser beam 2 that has passed through the slit 6 without the sample 9 and the laser beam 2 that has passed through the sample 9, and the output current of the photodiode 10 is amplified with the same amplification factor. This is because, when converted into a digital value, the change in the light amount of the laser beam 2 transmitted through the sample 9 is extremely small, so that the measurement resolution deteriorates.

In this embodiment, the laser beam 2 transmitted through the sample 9
Although one amplifier 15 is provided to amplify the output current of the photodiode 10 when light is received, a plurality of amplifiers having different amplification factors are provided in order to correspond to various types of samples. Different amplifiers may be used.

By the way, it is known that the light quantity of the He-Ne laser fluctuates as time passes after the power is turned on. FIG. 2 is a diagram showing a change in a light amount voltage of the laser light 2 reflected by the half mirror 4.

The vertical axis of FIG. 2 is the light quantity voltage of the laser beam 2 detected by the photodiode 17 shown in FIG. 1, and the horizontal axis is H
This is the elapsed time after the power of the e-Ne laser 1 is turned on.

Immediately after the power is turned on, the light amount of the laser beam 2 emitted from the He-Ne laser 1 is not stable and fluctuates as shown in FIG.

FIG. 3 is a diagram showing a change in the light quantity voltage of the laser beam 2 reflected by the half mirror 4 one hour after the power of the He-Ne laser 1 is turned on.

The vertical axis in FIG. 3 is the light quantity voltage of the laser beam 2 detected by the photodiode 17 shown in FIG. 2, and the horizontal axis is H
This is the elapsed time since the power of the e-Ne laser 1 was turned on.

As can be clearly understood from a comparison with FIG. 2, the laser beam 2 is emitted one hour (3600 seconds) after the power is turned on.
Is stable immediately after the power is turned on, but there are still small fluctuations. This is a characteristic of the He-Ne laser,
It occurs independently of fluctuations in the power supply. Also, He
Even if a laser other than the -Ne laser is used, a slight change in light amount occurs.

Generally, when the density of a sample is measured based on the amount of transmitted light, the density D of the sample is determined by setting the incident light amount to I ₀ ,
When the transmitted light amount is I, it can be expressed by Equation 1.

[0028]

D = log (I ₀ / I) As described above, since the amount of the laser beam 2 emitted from the He—Ne laser 1 varies with time, the amount of the laser beam 2 transmitted through the sample 9 is naturally fluctuate. Therefore, if I ₀ in Equation 1 is not corrected even though the light amount of the laser beam 2 transmitted through the sample 9 (I in Equation 1) fluctuates, the value of the density D obtained in Equation 1 changes. This change causes an error in the density measurement.

As can be seen from FIG. 3, the light quantity voltage of the laser beam 2 reflected by the half mirror 4 is about 0.7%.
Fluctuating. For example, when the incident light intensity I ₀ is to calculate the density D from Equation 1 is not corrected even though I ₀ changes by 0.23 percent, the concentration D deviates from the true value by about 0.001D. As described above, it is known that the visual characteristics of the naked eye can discriminate a density difference of 0.004D at intervals of about 1 mm. Is 0.001
This must be performed with an error of about D, and it cannot be ignored that the light quantity voltage of the laser beam 2 reflected by the half mirror 4 fluctuates by about 0.7%.

The present invention is intended to correct the value of I ₀ in Equation 1 as needed to eliminate a measurement error due to a change in the amount of incident light. By the way, if the correction simply corresponds to the change in the incident light amount, the above-described spectrophotometer has already performed the correction. However, in the spectrophotometer, the configuration and the processing for the correction corresponding to the change in the incident light amount are performed. It is complicated and has the drawback that it cannot be traced. According to the present invention, it is possible to perform a correction corresponding to a change in the amount of incident light while micro-tracing the density with a simple configuration and processing as shown in FIG.

Next, the correction according to the present invention corresponding to the fluctuation of the incident light amount will be described.

FIG. 4 is a flow chart of a correction process according to the present invention corresponding to a change in the amount of incident light.

First, as initialization, I _M0 which is a reference value of the fluctuation of the light amount detected by the photodiode 17 shown in FIG.
Is set to 1 as an initial value (F-1). Next, half mirror 4
In the reflected light amount of the laser beam 2 actually detected by the photodiode 17, and sets the detected value to the I _M1 (F-
2).

In step (F-3), it is checked whether or not the fluctuation of the light amount has exceeded a threshold value. In this embodiment, the threshold value is set to 0.23%, and the fluctuation of the light amount is set to 0.23%.
When this is the case, a correction operation is performed. If the fluctuation of the light amount is less than 0.23%, the process returns to step (F-2) and the process is repeated.

As a correction operation, the uniaxial mechanical stage 7 is moved by the stage controller 12, and the sample holder 8 is removed from the optical path of the laser beam 2 passing through the slit 6 (F-4). Here, the CPU 20 uses the amplifier 13 and the A / D converter 14 to convert the light amount of the laser beam 2 incident on the photodiode 10 directly from the slit 6 into I _0.
(F-5). Finally, the single-axis mechanical stage 7 is moved by the stage controller 12,
The sample holder 8 is placed in the optical path of the laser beam 2 passing through the slit 6.
The return to the same location as before the move (F-6), and updates the I _M0 is the reference value of the variation of the light quantity (F-7) Step (F-
Return to 2) and repeat the process.

The measurement of the concentration of the sample 9 is performed by moving the uniaxial mechanical stage 7 by the stage controller 12 and inserting the sample 9 into the optical path of the laser beam 2 having passed through the slit 6, and operating the correction processing flow. As a measurement procedure, the light amount of the laser beam 2 transmitted through the sample 9 is detected by the photodiode 10 and taken into the CPU 20 via the amplifier 15 and the A / D converter 16. Then, the transmitted light amount as I, determining the concentration D using equation 1 with I ₀ obtained in step (F-5) in FIG.

In this embodiment, the single-axis mechanical stage 7 is intermittently moved by a minute amount, and the concentration of the sample 9 is measured at each stop position. At this time, the moving distance of the single-axis mechanical stage 7 is measured by a laser measuring device. By precisely measuring at 11, a micro trace of the sample 9 is realized.

In this embodiment, the cylinder 3 is provided along the optical path of the laser beam 2 as shown in FIG.
The laser light 2 is made to pass through the inside. here,
This effect will be described.

FIG. 5 is a diagram showing the amount of light transmitted through the sample 9 when the cylinder 3 is not provided.

FIG. 6 is a diagram showing the amount of light transmitted through the sample 9 when the cylinder 3 is provided.

5 and 6, the ordinate represents the light intensity voltage of the laser beam 2 detected by the photodiode 10 shown in FIG. 1, and the abscissa represents one time from when the power of the He-Ne laser 1 is turned on.
This is the elapsed time from the predetermined time, assuming that a predetermined time that has passed the time or more is 0. In FIG. 5, the transmitted light voltage is considerably scattered, while in FIG. 6, the scatter is very small.

As described above, the tube 3 prevents the laser beam 2 from being refracted by the influence of air fluctuation and changing the optical path.

Next, the sample holder 8 shown in FIG. 1 will be described.

FIG. 7 is a sectional view of the sample holder 8.

The sample holder 8 is provided with a transparent support 8a made of glass, for example, together with the outer frame 8b, and the sample 9 is fixed by being sandwiched between the transparent supports 8a. By doing so, when the laser beam 2 is incident on the sample 8, the sample 8 can be prevented from being slightly deformed or moved by the heat.

FIGS. 8 to 11 show the effect of the transparent support 8a. FIG. 8 is a graph showing the fluctuation range of the density measured when the transparent support 8a is not provided.

In FIG. 8, the vertical axis represents the fluctuation range of the concentration (difference between the maximum value and the minimum value in 25 measurements) when the concentration of the sample 9 was measured 25 times without moving the uniaxial mechanical stage 7. The horizontal axis represents the moving distance of the uniaxial mechanical stage 7 (that is, the concentration measurement position on the sample 9).

FIG. 9 is a diagram showing the density measured when the transparent support 8a is not provided.

In FIG. 9, the vertical axis represents the average value of the density of the sample 9 measured 25 times without moving the single-axis mechanical stage 7, and the horizontal axis represents the moving distance of the single-axis mechanical stage 7 (that is, the sample 9). Upper density measurement position).

8 and 9, it can be seen that the fluctuation range of the density of the sample 9 is large at the portion where the density of the sample 9 changes largely (the portion where the slope of the curve in FIG. 9 is large).

FIG. 10 is a diagram showing the fluctuation width of the density measured when the transparent support 8a is provided.

In FIG. 10, the vertical axis represents the fluctuation range of the concentration (difference between the maximum value and the minimum value in 25 measurements) when the concentration of the sample 9 was measured 25 times without moving the uniaxial mechanical stage 7. Yes, horizontal axis is uniaxial mechanical stage 7
(That is, the concentration measurement position on the sample 9).

FIG. 11 is a diagram showing the density measured when the transparent support 8a is provided.

In FIG. 11, the vertical axis represents the average value of the density of the sample 9 measured 25 times without moving the single-axis mechanical stage 7, and the horizontal axis represents the moving distance of the single-axis mechanical stage 7 (that is, the sample 9). Upper density measurement position).

When comparing FIG. 8 with FIG. 10, FIG.
It can be seen that the variation width of the density is clearly smaller in this case, and the effect of the provision of the transparent support 8a on the sample holder 8 is clear. By firmly fixing the sample 9 with the transparent support 8a so that the sample 9 does not move or vibrate under the influence of the heat of the laser beam, the sample 9
The maximum density fluctuation width can be reduced from 0.0042 to 0.0025 to about 60% in a portion having a density gradient where the positional deviation greatly affects.

Since the transparent support 8a must be fixed firmly so that the sample 9 does not move, it is desirable that the transparent support 8a be made of a material having sufficient hardness such as glass. Further, it is preferable that the transparent support 8a is thin. This is because the laser light 2 is diffused by the sample 9 when the amount of the laser light 2 transmitted through the sample 9 is detected.
Is required to be as close to the sample 9 as possible.

Even when the sample holder 8 is not provided with a transparent support, the window through which the sample 9 is exposed when the sample 9 is fixed to the sample holder 8 is reduced, so that the sample 9
Is fixed, the same effect as that of providing the transparent support 8a can be obtained.

In the above-described embodiment, the density of the sample is measured by using the transmitted light of the sample. However, the present invention is not limited to this, and the density of the sample is measured by using the reflected light from the sample. Of course, it can be applied to. In this case, when the sample is removed from the optical path of the laser beam, a mirror or a standard white plate is arranged on the uniaxial mechanical stage so that the mirror or the standard white plate comes to the position where the sample has been up to that point, and the reflected light from the sample is reflected. What is necessary is just to make it possible to receive the reflected light from the mirror or the standard white plate by the photodiode that has received the light.

Further, in the above-described embodiment, when detecting the incident light amount I ₀ used for obtaining the density D from the _{equation 1} ,
By removing the sample from the optical path of the laser beam, incident light was received by the photodiode that had received the transmitted light before.However, the present invention is not limited to this. , it is of course to be adapted to detect the amount of incident light I ₀ by moving between the He-Ne laser and the sample. This method can also be applied to the case where the concentration of a sample is detected based on the reflected light from the sample.

In this embodiment, the sample 9 is moved to perform the microtrace of the concentration. However, by moving the optical path of the laser beam 2 to change the position on the sample 9 where the laser beam 2 is irradiated. A micro trace of the concentration may be performed.

[0061]

As described above, according to the present invention,
Since the laser beam irradiated for the density measurement can be monitored by the photodiode used for the density measurement, it is compared with the case where the light beam is divided into two light beams and the light amount fluctuation is corrected by a separate photodiode.
There is no error due to aging of the beam splitter or individual differences in photodiodes. Therefore, a highly accurate concentration measuring device capable of micro-tracing can be realized at a low cost with a simple configuration.

Since the density measuring apparatus according to the present invention has a very high accuracy, it can be used for checking the granularity of a photographic film, for example.
It can also be used for analysis of medical output film images such as scanners and MRI, and analysis of printed halftone images.

[Brief description of the drawings]

FIG. 1 is a block diagram of a concentration measuring device according to the present invention.

FIG. 2 is a diagram showing a change in a light amount voltage of a laser beam reflected by a half mirror immediately after power-on of a He-Ne laser shown in FIG. 1;

FIG. 3 is a diagram showing a change in a light amount voltage of a laser beam reflected by a half mirror one hour after the power of the He—Ne laser shown in FIG. 1 is turned on.

FIG. 4 is a flowchart of a correction process according to the present invention corresponding to a change in the amount of incident light.

FIG. 5 is a diagram showing the amount of light transmitted through a sample when no cylinder is provided.

FIG. 6 is a diagram showing the amount of light transmitted through a sample when a cylinder is provided.

FIG. 7 is a cross-sectional view of the sample holder shown in FIG.

FIG. 8 is a diagram showing a fluctuation range of density measured when a transparent support is not provided.

FIG. 9 is a diagram showing a density measured when a transparent support is not provided.

FIG. 10 is a diagram showing a fluctuation width of a density measured when a transparent support is provided.

FIG. 11 is a diagram showing the density measured when a transparent support is provided.

[Explanation of symbols]

 Reference Signs List 1 He-Ne laser 2 Laser beam 3 Tube 4 Half mirror 5 Cylindrical lens 6 Slit 7 Uniaxial mechanical stage 8 Sample holder 8a Transparent support 8b Outer frame 9 Sample 10 Photodiode 11 Laser measuring device 12 Stage controller 13 Amplifier 14 A / D Converter 15 Amplifier 16 A / D converter 17 Photodiode 18 Amplifier 19 A / D converter 20 CPU 21 Beam expander

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-303365 (JP, A) JP-A-2-247544 (JP, A) JP-A-2-159543 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 Practical file (PATOLIS) Patent file (PATOLIS)

Claims (5)

(57) [Claims] A laser beam irradiating unit for irradiating a fine laser beam to an image sample whose concentration is to be measured; moving a laser beam irradiation position on the image sample and removing the image sample from an optical path of the laser beam; Moving means for moving the laser light irradiating means or the image sample, position measuring means for measuring a laser light irradiating position on the image sample, and laser light transmitted through the image sample or reflected by the image sample A light amount detecting means for detecting a light amount of the laser light; an optical path of the laser light by the moving means at a timing determined based on a light amount detected by the light amount detecting means and a light amount variation pattern of the laser light irradiating means; The laser light emitted from the laser light irradiation means was detected by the light quantity detection means when the laser light was guided into the light quantity detection means. Calculating means for calculating the density of the image sample based on the amount of laser light from the laser light irradiating means, wherein the laser light irradiation position measured by the position measuring means and the density of the image sample calculated by the calculating means Wherein the density distribution of the image sample is obtained from the following. 2. The apparatus according to claim 1, further comprising: an irradiation light amount detecting unit configured to detect a light amount of the laser light irradiated by the laser light irradiation unit, wherein the timing at which the image sample is removed from the optical path of the laser light corresponds to the light amount detected by the irradiation light amount detecting unit. The concentration measurement device according to claim 1, wherein the concentration measurement device is determined based on a variation amount of the concentration. 3. A cylinder is provided around an optical path of a laser beam irradiated by said laser beam irradiating means.
Alternatively, the concentration measuring device according to claim 2. 4. The density measuring apparatus according to claim 1, wherein the image sample has a density measurement surface covered with a transparent support and is held by scissors. 5. An at least one first amplifier for amplifying an output of said light amount detecting means with a different amplification factor for each type of image sample.
And an amplifier for amplifying the output of the light amount detection means when the image sample is removed from the optical path of the laser light, and the amplification factor of the first amplifier is set to the second amplifier.
5. The concentration measuring device according to claim 1, wherein the amplification factor is larger than the amplification factor of the amplifier.