JPH08247847A - Spectrophotometer - Google Patents

Abstract

PURPOSE: To set the optimum accumulating time of a CCD linear image sensor automatically, by comparing the maximum valve data of the detecting signal for one line part, and a reference value. CONSTITUTION: By a transfer pulse from a CCD driving circuit 21, the light receiving data for one line part from a CCD linear image sensor 12 is read, and it is fed to a CCD signal processing circuit 22 and a peak holding circuit 26 through an amplifier 28. The circuit 26 maintains the maximum value data Dmax from the data D of one line part. And a comparator 27 in which the upper limit value and the lower limit value to be the comparating reference are set decides whether the maximum data Dmax is within a set scope or not, and a CPU 24 controls the cycle of the shift pulse SH of the circuit 21, to settle the maximum data Dmax within the set scope of the upper limit value and the lower limit value. Consequently, the optimum light accumulating time of the sensor 12 can be set automatically in a simple operation, according to the increase and the decrease of the incident light quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrophotometer for measuring the intensity of light according to wavelength, and more specifically, to enable automatic setting of the light accumulation time of a CCD linear image sensor as a light receiving element. The present invention relates to a spectrophotometer.

[0002]

2. Description of the Related Art A spectrophotometer is widely used for colorimetric quantitative analysis of various compounds, color measurement or color matching of dyes and paints, flame photo analysis, etc., but the conventional example is shown in the schematic diagram of FIG. While explaining.

According to this method, the light to be measured (incident light) is converted into parallel light having a limited light flux width by an incident optical system (not shown), and then is incident on the dispersion prism 1, and the dispersion prism 1 produces a unique color. Dispersed in the spectrum of. The dispersed spectrum light is received by the light receiving element 2 arranged at a predetermined angle behind the dispersion prism 1.

A photodiode array or CCD linear image sensor is used for the light receiving element 2,
A detection signal corresponding to the amount of received light is output from each of the light receiving cells. The detection signal is output through the signal reading circuit 3 including, for example, an integrator, and the spectrum of the measured light is measured based on the output signal.

[0005]

By the way, when a CCD linear image sensor is used as a light receiving element, it is best to set the incident light amount to about 1/2 of the standard saturated exposure amount. The amount of incident light is obtained by the product of the illuminance on the light receiving surface and the light accumulation time (exposure time). The light accumulation time is determined by the cycle of the shift pulse supplied from the CCD drive circuit.

As described above, in the CCD linear image sensor, the light accumulation time can be arbitrarily set by changing the period of the shift pulse, and therefore a wide dynamic range can be obtained according to the increase or decrease of the incident light quantity. .

However, the problem is how to measure the increase or decrease in the amount of incident light. Generally, an exposure meter is also used, but it is troublesome to carry the exposure meter at all times. Further, even if the exposure meter is integrated, not only the cost is increased, but also the apparatus itself becomes large.

The present invention has been made in order to solve such a conventional problem, and an object thereof is to optimize the CCD linear image sensor according to the increase or decrease of the incident light amount without requiring an exposure meter or the like. Another object of the present invention is to provide a spectrophotometer capable of automatically setting various light accumulation times.

[0009]

In order to achieve the above object, the present invention provides a dispersion prism that disperses incident light whose luminous flux width is limited by an incident optical system into spectral light and receives the same spectral light. A CCD linear image sensor as a light receiving element that outputs a detection signal proportional to the amount of received light, and a CCD that gives a shift pulse for setting the light accumulation time to the CCD linear image sensor and a transfer pulse for transferring the detection signal. Same as drive circuit
In a spectrophotometer having a control unit for controlling a CD drive circuit, a peak hold circuit for holding maximum value data from a detection signal for one line output from the CCD linear image sensor according to the transfer pulse, and a peak hold circuit in advance. It is characterized in that it comprises a comparator for comparing the set reference value with the maximum value data, and the control unit determines the cycle of the shift pulse based on the comparison result of the comparator.

In this case, the comparator comprises a window comparator having an upper limit setting value and a lower limit setting value, and the control section determines the cycle of the shift pulse so that the maximum value data falls within the range of the setting value. It is preferable to do so.

Further, in the CCD signal processing circuit, the CC
The detection signal for one line output from the D linear image sensor is A / D-converted, and the individual data thereof is stored. When the maximum value data is within the set value range, It is preferable to read data from the CCD signal processing circuit, perform a predetermined calculation, and display the optical spectrum of the incident light on the display.

[0012]

According to the above structure, the maximum value data in the detection signal for one line output from the CCD linear image sensor is held by the peak hold circuit. Then, the maximum value data and the reference value are compared by the comparator, whereby the light accumulation time according to the reference value is automatically set.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Also in this spectrophotometer, the light to be measured is parallel light having a limited luminous flux width and is dispersed by the dispersion prism 1.
As shown in FIG. 1, a pair of cylindrical lenses 10a and 10b are used as the incident optical system in this embodiment.

That is, the two cylindrical lenses 1
0a and 10b are arranged so as to face each other with their convex surfaces facing the other side, and the first slit plate 11a is provided at the focal position of the two lenses, and the second slit plate 11b is also provided on the outgoing light side.
Are arranged so that the light to be measured enters the dispersion prism 1 as parallel light.

A CCD (charge coupled device) linear image sensor 12 as a light receiving element is arranged at a predetermined angle behind the dispersion prism 1 (on the right side in FIG. 1). In this embodiment, the element pitch is 14 μm
Therefore, a CCD linear image sensor having 1024 elements is used. According to this, even when the spread of the light from the dispersion prism 1 is small, a sufficient resolution can be obtained. It can be arranged closer to the prism 1.

Next, the peripheral circuit of the CCD linear image sensor 12 will be described with reference to FIG. According to this, in the present invention, the CCD drive circuit 21, CC
In addition to the D signal processing circuit 22 and the CPU (central processing unit) 24, a peak hold circuit 26 and a comparator 27 are provided.

The CCD driving circuit 21 supplies the CCD linear image sensor 12 with a shift pulse SH for controlling the light accumulation time thereof and a transfer pulse Φ for reading the received light data D from the sensor 12 (both see FIG. 3). It With this transfer pulse Φ, the received light data D for one line is read from the CCD linear image sensor 12 and supplied to the CCD signal processing circuit 22 and the peak hold circuit 26 via the amplifier 28.

The CCD signal processing circuit 22 has an A / D converter and a memory (RAM), and performs A / D conversion of the received light data D for one line by, for example, a DMA (Direct Memory Access) system. All the data is stored in the memory.

The peak hold circuit 26 holds the maximum value data Dmax from the received light data D for one line. The maximum value data Dmax is held during the one-line output period, and is released by the reset pulse RS output from the CCD drive circuit 21 immediately before the next line scan by the transfer pulse Φ is started.

In this embodiment, the comparator 27 is a window comparator in which an upper limit value and a lower limit value which are comparison criteria are set, and it is determined whether the maximum value data Dmax is within the set range. In this case, the upper limit value and the lower limit value are set so that the input level of the received light data to the A / D converter of the CCD signal processing circuit 22 is near the full scale level.

The CPU 24 monitors the determination result of the comparator 27 and controls the cycle of the shift pulse SH of the CCD drive circuit 21 so that the maximum value data Dmax falls within the set range by the upper limit value and the lower limit value. That is, when the maximum value data Dmax <lower limit value, the cycle of the shift pulse SH is lengthened, while when the maximum value data Dmax> upper limit value, the cycle of the shift pulse SH is shortened. .

When the maximum value data Dmax is within the set range, the CPU 24 reads the received light data from the memory of the CCD signal processing circuit 22 and performs a predetermined correction calculation (for example, non-linearity correction of dispersion spectrum, spectral sensitivity correction). ), The light spectrum (spectral radiant energy) of the incident light is displayed on the display 25. For reference, the above operation flowchart is shown in FIG. 4, but the exposure time and the light accumulation time in the flowchart have the same meaning.

In the above embodiment, the window comparator is used to compare the maximum value data Dmax with the upper limit value and the lower limit value. However, in some cases, for example, only the lower limit value is set and the maximum value data Dmax is set. The shift pulse SH may be controlled so as to exceed that value.

[0024]

As described above, according to the present invention,
The optimum light storage time of the CCD linear image sensor is automatically set according to the increase or decrease of the incident light amount by a simple operation of setting a predetermined reference value in the comparator without the need for a separate exposure meter. It

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a spectrophotometer according to the present invention.

FIG. 2 is a block diagram illustrating a peripheral circuit of the CCD linear image sensor in the embodiment.

FIG. 3 is a timing chart showing a shift pulse applied to the CCD linear image sensor, a transfer pulse, and a detection signal output from the sensor.

FIG. 4 is an operation flowchart of the embodiment.

FIG. 5 is a schematic diagram according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dispersion prism 10 Cylindrical lens 12 CCD linear image sensor 21 CCD drive circuit 22 CCD signal processing circuit 24 CPU 25 Display 26 Peak hold circuit 27 Comparator

Claims (3)

[Claims] 1. A dispersion prism that disperses incident light whose luminous flux width is limited by an incident optical system into spectral light, and a CCD as a light receiving element that receives the spectral light and outputs a detection signal proportional to the amount of the received light. A linear image sensor, a CCD drive circuit for giving a shift pulse for setting the light accumulation time to the CCD linear image sensor and a transfer pulse for transferring the detection signal, and the like.
In a spectrophotometer having a control unit for controlling a CD drive circuit, a peak hold circuit for holding maximum value data from a detection signal for one line output from the CCD linear image sensor according to the transfer pulse, and a peak hold circuit in advance. A spectrophotometer, comprising: a comparator that compares a set reference value with the maximum value data, wherein the control unit determines the cycle of the shift pulse based on the comparison result of the comparator. 2. The comparator comprises a window comparator having an upper limit setting value and a lower limit setting value, and the control unit determines the cycle of the shift pulse so that the maximum value data falls within the range of the setting value. The spectrophotometer according to claim 1, wherein: 3. A CCD signal processing circuit for A / D converting a detection signal for one line output from the CCD linear image sensor and storing individual data thereof, wherein the control section has the maximum value. The data according to claim 2, wherein when the data is within the range of the set value, the data is read from the CCD signal processing circuit and a predetermined calculation is performed, and the optical spectrum of the incident light is displayed on the display. Spectrophotometer.