JPH055703A - Absorbance detection device - Google Patents

Abstract

PURPOSE:To enable an absorbance of a maximum sensitivity to be measured according to a sample by adjusting a quantity of light of a light source according to the absorbance of the sample automatically and then adjusting a light-reception sensitivity in a direction which is opposite to that of increase/decrease of the quantity of light in synchronization with it. CONSTITUTION:A control device 1 feeds a maximum gain as a signal for quantity of light (light-source gain) which determines a quantity of light of a light source 2 to a D/A converter 4. At the same time, since a product of light-reception amplifier gains G1 and G2 is set to a constant value in the device 1, the minimum gain G1 is sent to a D/A converter 8. The device 1 obtains a quantity of reference light IR when there are no samples and then allows the sample to flow. A light-reception sensor 5 detects the quantity of light of the sample and then amplifies it with the gain G1 by a light-reception amplifier 6 and then feeds a measured quantity of light IM to the device 1 through an A/D converter 7. The device 1 calculates an absorbance according to the quantities of light IR and IM. In this case, when the device 1 judges that the absorbance is not at a proper level, it allows the gain G2 to be reduced by a specified amount, namely the gain G1 increases by a specified amount simultaneously, thus resulting in an increased light-reception sensitivity. This operation is repeated, thus enabling the absorbance at the maximum sensitivity to be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an electrophoretic device, etc.
The present invention relates to an absorbance detection device suitable for a field requiring high detection sensitivity with high absorbance.

[0002]

2. Description of the Related Art Conventionally, an optical density detector for measuring the optical density of a sample in a liquid or gas, that is, the optical density, is
For example, it was configured as shown in FIG.

The absorbance detector shown in FIG. 3 is composed of three blocks, a light projecting side, a light receiving side and a data processing section (31). First, the light projecting side is composed of a light source unit 11, a light projecting unit 12, and an optical fiber 13 for optically connecting the two. Next, on the light receiving side, the light receiving unit 21 and the control unit 2
It consists of 2. Here, the image sensor 23 and the charge amplifier 24, which constitute the light receiving unit 21 and detect the light amount, are installed close to each other by the migration tank 25 which is a detection target and the short optical fiber 26.

The control unit 22 on the light receiving side controls the image sensor 23, processes the output of the charge amplifier 24, and outputs a light amount signal to the data processing unit 31. The data processing unit 31 controls the light source unit 11 and the control unit 22 and processes the light amount signal output from the control unit 22 as follows to calculate the absorbance (OD).

Absorbance OD = log ₁₀ IR / IM IR: Reference light quantity (when there is no sample) IM: Measurement light quantity (when there is a sample) In the above formula, the measurement light quantity IM is the change in the absorption quantity due to the sample as ΔIM. Then, it can be expressed as IM = IR-ΔIM. Therefore, the absorbance OD can be expressed as OD = log ₁₀ {1 / (1-ΔIM / IR)}.

From this equation, the absorbance OD is ΔIM / IR
On the other hand, as shown in FIG. 4, it can be seen that if ΔIM / IR is increased, the absorbance OD sharply increases and the sensitivity increases.

However, considering the controllable reference light amount IR, if IR is made too small, the absolute value of the light amount decreases and the corresponding electric output becomes small, so that the electrical S Considering the / N ratio, it is necessary to set it to a certain level or higher. Therefore, normally, the reference light amount IR is set with some margin for the maximum ΔIM to be measured.

Conventionally, the reference light amount IR, that is, the light amount of the light source is fixed, and therefore the detection sensitivity is also fixed. Therefore, when measurement is required for a wide range of ΔIM, a sample having a particularly small absorbance cannot be detected, which is a problem.

[0009]

As described above, in the conventional absorbance detecting device, the light amount of the light source is fixed,
Since the detection sensitivity is also fixed, there is a problem that it is impossible to detect a sample having a wide absorbance range.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an absorbance detection device capable of detecting a sample having a wide absorbance range.

[0011]

DISCLOSURE OF THE INVENTION The present invention relates to an absorbance detection device for measuring the absorbance of a sample in a liquid or a gas, in which the light amount of a light source is automatically adjusted according to the absorbance of the sample, and in synchronization therewith. It is characterized in that means for adjusting the light receiving sensitivity in the direction opposite to the increasing / decreasing direction of the light quantity is provided, and the absorbance is measured at the maximum sensitivity according to the sample.

[0012]

According to the above construction, the light amount of the light source used for the absorbance detection is not fixed, but is automatically changed according to the absorbance of the sample, and the light receiving sensitivity is changed in synchronization with the change in the light amount. By changing the direction to the opposite direction and always keeping the relationship between the light amount and the light receiving sensitivity constant, it is possible to measure the absorbance with the maximum sensitivity according to each sample.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a configuration of a portion of an absorbance detecting device according to an embodiment of the present invention, which is directly related to the present invention.

In FIG. 1, reference numeral 1 is a control device realized by a microcomputer or the like. The control device 1 includes a light source drive amplifier 3 for driving the light source 2 (on the light projecting side), a D / A (digital / analog) converter 4
Connected through. The D / A converter 4 is provided with a digital light amount signal (hereinafter, referred to as light source gain) G2 for determining the light amount of the light source 2 from the control device 1.

The control device 1 also receives a light reception signal (light amount signal) from the light reception sensor 5 (on the light reception side) of the absorbance detection device.
The light-receiving amplifier 6 for amplifying the
It is connected via a (digital) converter 7. Between the light receiving amplifier 6 and the control device 1, the control device 1
Light receiving amplifier gain G1 (digital value) given by
There is provided a D / A converter 8 for digital-to-analog converting and supplying to the light receiving amplifier 6.

The light receiving amplifier gain G1 and the light source gain G2 are set by the control device 1 so as to satisfy the following equation: G1.multidot.G2 = k = constant.

A device for outputting data, for example, a graphic display terminal 9 is further connected to the control device 1.

In the configuration of FIG. 1, the control device 1 has a D /
By giving a digital light source gain G2 to the A converter 4, the light amount signal to the light source drive amplifier 3 is controlled via the D / A converter 4.

At the same time, the control device 1 controls the gain of the light receiving amplifier 6 via the D / A converter 8 by giving the light receiving amplifier gain G1 corresponding to the light source gain G2 to the D / A converter 8. That is, the control device 1
Is a gain (G1) corresponding to the light source light intensity determined by the light source gain G2 in the light receiving amplifier 6 (inversely proportional).
The signal amplification of the received light signal (light amount signal) is performed.

Here, the control unit 1 sets G1 and G2 so that G1.G2 = k (constant) as described above. Therefore, when the light source light amount (G2) is lowered, detection is performed as it is. The decrease in signal level is corrected by increasing the light receiving amplifier gain (G1). As a result, the reference light amount detection level is kept constant regardless of the change in the light receiving amplifier gain.

Next, the details of the absorbance detection process by the absorbance detection device of FIG. 1 will be described with reference to FIG. Note that FIG. 2 is a flowchart showing an absorbance detection processing procedure (algorithm) by the absorbance detection device of FIG.

First, the control device 1 of the absorbance detection device of FIG.
Gives the D / A converter 4 the maximum gain (initial gain) Gmax (for specifying the maximum light amount) determined by the hardware specifications as the light amount gain G2 (step S
1). At the same time, the control device 1 gives k / G2, that is, k / Gmax for designating the minimum gain, to the D / A converter 7 as the light receiving amplifier gain G1, as is clear from the relationship between G1 and G2.

Next, the controller 1 uses the maximum light source gain G2 (= Gmax), that is, the minimum light receiving amplifier gain G1.
Then, before the sample flow, the reference data (reference light amount) IR (i) (where i = 1 to n, where n is the number of data determined by the hardware specifications) when there is no sample It is acquired (step S2).

When the control device 1 obtains the reference data IR (i) in step S2, it sends a sample to the device (step S3).

After the sample flows, the control device 1 acquires the amount of light as measurement data IM (i) (i = 1 to n) (step S4). That is, the light amount when the sample is flown is detected by the light receiving sensor 5, and the light receiving signal (light amount signal) is amplified by the light receiving amplifier 6 with the gain G1.
Further, it is converted into a digital value by the A / D converter 7, and the digital value is measured data (measurement light quantity) IM (i).
Is taken into the control device 1.

The controller 1 measures the measurement data IM (i) acquired in step S4 and the reference data IR (i) acquired previously.
Based on, performs the absorbance calculation of the following equation _{OD (i) = log 10 IR} (i) / IM (i) ( step S5). Thus, the absorbance (absorbance level) OD (i) is calculated by the difference between the logarithmic conversion values of IR (i) and IM (i). That is, the light loss for the sample is calculated as the absorbance.

Next, the control unit 1 checks whether or not the maximum value maxOD (i) of the absorbance OD (i) calculated in step S5 is an appropriate level (step S6). This is the full scale FS on the hardware specification (eg
Assuming that 12 bits are assigned to the data in the control device 1, "4095" in the count value corresponds to the full scale FS), for example, whether the value is 80% to 100%, that is, 0. 8FS ≦ maxOD (i) ≦ FS.

The control device 1 executes ma in step S6.
Judging that xOD (i) is not within the above range, that is, the absorbance level is not at the appropriate level, the current light source gain G2 (the level is less than 80% of full scale) is the minimum value (minimum). If the gain is not Gmin) (step S7), G2 is decreased by a predetermined amount .DELTA.G (step S8), and at the same time, the light receiving amplifier gain G1 is increased (that is, the light receiving sensitivity is increased) so as to maintain the relationship of G1.multidot.G2 = k. .. This is because the full-scale FS is always fixed at, for example, 12 bits (the count value is "4095") due to the structure of the control device 1 (for example, a microcomputer), but the OD value for the FS always depends on the light receiving sensitivity. This is because in order to change in inverse proportion, G2 is decreased by .DELTA.G and the light receiving sensitivity is increased by that amount, so that the ratio of maxOD (i) to FS is increased and falls within the above appropriate range.

As described above, the control device 1 controls G2 by ΔG.
When the light receiving sensitivity is increased by the amount corresponding to the above, the measurement process after step S4 is repeated.

If the maximum absorbance maxOD (i) obtained by the absorbance calculation in step S5 is at an appropriate level,
Or even if it is not at the proper level, the light source gain G2 at that time
Is the minimum gain Gmin (which specifies the minimum amount of light) (hence the photoreceiver amplifier gain G1 is the maximum gain),
The controller 1 determines the gain G2 (and G1) at that time as an appropriate gain, and ends the sample flow (step S9). In step S8, the light source gain G2
As a result of the measurement process after decreasing ΔG by ΔG, maxOD
When (i) exceeds the full scale FS, the light source gain G2 before that is adopted as the appropriate gain.

After the sample flow is completed, the control device 1 again determines the reference data IR (i) at the determined appropriate gain.
Is obtained (step S10), and the absorbance is recalculated (step S11).

As described above, in the absorbance detecting device (control device 1 thereof) of FIG. 1, the reference data IR (i) is temporarily stored at the maximum light source gain G2 (maximum light amount) before the sample is flowed, and an appropriate gain is obtained. Until it is determined (find), the absorbance is calculated based on this reference data, the proper gain is determined, the sample flow is completed, and then the reference data with the determined proper gain is acquired again. .. This is because, in principle, the reference data cannot be acquired during the flow of the sample, but in data processing, the reference data IR (reference light amount) / measurement data IM
(Measured light quantity) electrical detection level (light receiving amplifier gain G
This is because the S / N ratio of the calculated absorbance is improved by matching 1).

Note that the flow chart of FIG. 2 shows a processing procedure in the case of performing only one measurement for simplification, but the present invention is not limited to this. For example, in the case of continuously acquiring data, it suffices to once set an appropriate gain according to the flowchart of FIG. 2 and then measure the gain while fixing the gain. Such controls
Control device 1 (composed of a microcomputer, etc.)
Can be easily realized.

[0034]

As described above in detail, according to the present invention, the light amount of the light source used for the absorbance detection is automatically changed according to the absorbance of the sample, and the light receiving sensitivity is synchronized with the change of the light amount. Since the light intensity is changed in the opposite direction, the absorbance can be measured with the maximum sensitivity according to each sample, so that the sample with a wide absorbance range can be detected and the sample with low absorbance can It can be detected with sensitivity.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an absorbance detection device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of an absorbance detection process by the absorbance detector.

FIG. 3 is a block configuration diagram of a conventional absorbance detection device.

FIG. 4 is a ratio Δ between the change ΔIM in the amount of absorbance and the reference light amount IR.
The figure which shows the relationship between IM / IR and light absorbency OD.

[Explanation of symbols]

1 ... Control device, 2 ... Light source, 3 ... Light source drive amplifier, 4, 8
... D / A converter, 5 ... Light receiving sensor, 6 ... Light receiving amplifier, 7 ... A / D converter.

Claims (1)

Claim: What is claimed is: 1. In an absorbance detection device for measuring the absorbance of a sample in a liquid or a gas, the light amount of a light source is automatically adjusted according to the absorbance of the sample, and light is received in synchronization with this. An absorbance detecting device, characterized in that means for adjusting the sensitivity in a direction opposite to the increasing / decreasing direction of the light amount is provided, and the absorbance is measured at the maximum sensitivity according to the sample.