JPH01143922A - Spectrophotometric device - Google Patents

Abstract

PURPOSE:To enable spectrophotometry and colorimetry with high accuracy with any light sources even if the position setting with an incident optical system is rough by combining a monochrometer and the light transmission and diffusion plate, light shielding hood and optical fiber bundle set in the size and position relation to meet the conditions of the optical system within the monochrometer. CONSTITUTION:The monochrometer 5 has an opening angle thetam from an incident slit 6 to a concave diffraction grating 7. The optical fiber bundle 3 is connected at one end to the slit 6 and is specified in diameter (d) and numerical aperture N.A. to N.A.-sin(thetam/2) or N.A.>sin(thetam/2). The milky white diffusion plate 1 having transmission and diffusion characteristics is fixed apart at the distance L of L>>d from the other end of the bundle 3 and has the diameter of D-2Ltan(thetam/2). The light shielding hood 2 shields light in the space from the diffusion plate 1 to the other end of the bundle 3. The light of a light source 8 to be measured is transmitted and diffused by the diffusion plate 1 and is projected through the bundle 3 to approximately the entire surface of the grating 7 of the meter 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a spectrophotometer for measuring the spectral distribution of a light source, the color of the light source, and the color of an object with high precision.

Conventional technology When controlling the quality of lighting light sources and CRT displays, or controlling and evaluating the color of resins, paints, and other materials, photoelectric colorimeters and color difference meters are used as simple methods, and are used as precision measurement methods. A spectrophotometer is generally used. For this purpose, the chromaticity measurement accuracy is given by the chromaticity coordinates (x, y):
In some cases, a value of about 0.001 is required, and highly accurate spectrophotometry is required.

Spectrophotometry is a comparative measurement of a standard light source and a measured light source, and it is necessary to precisely match the positional relationship between these light sources and the input optical system of the spectrophotometer, and the measurement time is long, so it is not suitable for measurements at manufacturing sites, etc. was not suitable. On the other hand, in recent years, concave diffraction gratings and photoelectric conversion element arrays have been used to make spectrometers smaller and faster. Spectrophotometers using fiber optic handles are beginning to be used. However, although conventional spectrometers with this configuration are suitable for observing spectral profiles, they do not have sufficient accuracy for colorimetry purposes.

Problems to be Solved by the Invention In the spectrophotometer with the conventional configuration shown in FIG. 2, the light from the light source to be measured is directly incident on the end face of the optical fiber, so the numerical aperture () J, A, ), sinθm≦N
, A, , , (1) Light having an incident angle θi that satisfies the condition is incident and propagates within the optical fiber. Since the incident light travels through the optical fiber through total reflection, the incident angle propagates and appears at the output end of the optical fiber. Therefore, the light distribution characteristics at the output end of the optical fiber will be, for example, a sharp beam in one direction when measuring a point light source, and within the range of the incident angle determined by equation (1) when measuring a light source with a large light emitting surface. The light distribution characteristics become wider.

On the other hand, a monochromator consists of a wavelength dispersion element such as a diffraction grating or a prism, and an optical system that forms an image of an input slit.The monochromator reconverges light of a certain wavelength that spreads at a certain solid angle from the input slit and outputs it. The structure is such that the image is formed on the surface of the slit.

Therefore, the light entering the monochromator at different angles from the entrance slit hits different points on the light-receiving surface of the wavelength dispersion element and converges after following different optical paths in the imaging system. Furthermore, there is generally spatial non-uniformity in the characteristics of wavelength dispersive elements and imaging components. Therefore, the transfer characteristic of the monochromator from the entrance slit to the exit slit is
The light becomes non-uniform depending on the direction (angle) of the light exiting the entrance slit.

Therefore, with the conventional spectrophotometer with the configuration shown in Figure 2, the alignment with respect to the input end of the optical fiber cannot be accurately reproduced even when the standard light source and the measured light source have different shapes and sizes, or even under the same conditions. In this case, the transfer characteristics of the monochromator are different in each case, resulting in a problem of large measurement errors.

The present invention solves the above-mentioned conventional problems. Even if the shape and size of the light source to be measured changes, or even if the positioning of the light source and the incident optical system is not precise, it can always perform highly accurate spectrophotometry.
The purpose of this invention is to provide a spectrophotometer that can measure color.

Means for Solving the Problems The present invention provides a monochromator whose opening angle from the entrance slit to the wavelength dispersion element is θm, and one end of which is connected to the entrance slit of the monochromator, and whose diameter is d1 and the numerical aperture N, A.
, is N,A, ~5in(θm,,/2) or N,A
, ) sin(θm/2), an optical fiber handle;
D ~2Ltan(θm,/
2) A spectrophotometer comprising a light transmitting diffuser plate having a diameter of 2), and a light shielding hood that blocks light from a space between the light transmitting diffuser plate and the end face of the optical fiber handle.

The working light transmitting diffuser plate collects light from all directions within a wide solid angle, diffuses and transmits this incident light as uniformly as possible regardless of the incident angle, and also reduces the incident angle θ to the optical fiber handle. , θ1≦Tan−′ (D/2L), and input the light into the optical fiber handle. The light-shielding hood blocks light from sources other than the light transmission diffuser plate, and the optical fiber handle guides the incident light to the input slit of the monochromator, which sweeps the wavelength and outputs spectral data of the incident light.

Due to this effect, even if the angle of incidence on the light receiving surface (the above-mentioned light transmission diffuser plate) of the spectrophotometer of the present invention changes, the light distribution characteristics of the light passing through the entrance slit of the monochromator can be kept uniform. This has the effect of eliminating measurement errors that occur when the shape or size of the light source to be measured changes or when the position settings of the light source and light receiving surface deviate, and also reduces stray light within the monochromator.

Embodiment FIG. 1 shows an embodiment of the spectrophotometer of the present invention. In FIG. 1, 1 is an opalescent diffuser plate, 2 is a light-shielding hood, 3 is an optical fiber handle, 4 is a support, 5 is a monochromator, 6 is an entrance slit in the monochromator 5, and 7
is a concave diffraction grating in the monochromator 5, and 8 is a light source to be measured. The operation of the spectrophotometer of this embodiment will be described below.

In FIG. 1, first, light from the entire light source 8 to be measured is incident on the opalescent diffuser plate 1. As shown in FIG. The opalescent diffuser plate 1 has transmission and diffusion characteristics close to those of a perfect diffuser plate, and as shown in Fig. 3,
It has nearly-like goniotransmission characteristics for incident light from all directions. The light transmitted and diffused by the opalescent diffuser plate 1 enters the fiber from the fiber end face of the optical fiber handle 3. At this time, the maximum value θ1max of the incident angle to the fiber end face is determined by the diameter of the opalescent diffuser 1 and the distance to the fiber end face, and θm max
= Tan-1(D/2L) , , , ,
It is expressed as (2). At this time, in order for all the light with the incident angle within this range to enter the optical fiber handle 3, N, A, ≧5 inches (01 m.,) , , , (
3) It is necessary to use an optical fiber handle with N, A, satisfying the following. If this condition is not met, the diffused light from the periphery of the opalescent diffuser plate 1 will not be sufficiently incident on the optical fiber handle 3, which will make it impossible to use the monochromator 5 in sufficiently bright conditions, as will be described later. , the size of the opalescent diffuser plate 1 will not be fully utilized. The light-shielding hood 2 fixes the opalescent diffuser plate 1 at a predetermined position and blocks incident light from sources other than the opalescent diffuser plate 1 to the fiber end face. If the distance is too small relative to the diameter d of the optical fiber handle 3, the range of the incident angle will expand beyond that expressed by equation (2), so the light receiving section consisting of the opalescent diffuser 1 and the light shielding hood 2 is not practical. L within the size range>>
It is necessary to choose such that d.

The light incident on the optical fiber handle 3 propagates within the optical fiber by total internal reflection, and exits from the other end face connected to the entrance slit 6 of the monochromator 5. On this end face, each optical fiber is arranged in a line according to the shape of the entrance slit 6. The outgoing angle from this end face (with respect to the central axis) is equal to the incident angle due to the propagation properties within the optical fiber, so the spread angle θf of the outgoing light is: θf=2θ1max, (4)
It is expressed as If the spread angle from the entrance slit 6 to the concave diffraction grating 7 is θm, the warp and distance of the opalescent diffuser plate gli
L is D/L~2tan(θff,/2), ,
,, (5) If you choose so that the relationship becomes (2),
From equations (4) and (5), it becomes 01 to 6 m, and the emitted light from the optical fiber handle 3 that spreads through the entrance slit 6 can be made to enter almost the entire surface of the concave diffraction grating 7.

The distribution of irradiance on the surface of the concave diffraction grating 7 at this time is:
Due to the function of the opalescent diffuser plate 1, the angle of incidence from the light source 8 to be measured to the opalescent diffuser plate 1 is almost unaffected and is always constant, so even if the size or position of the light source 8 to be measured changes, the measurement will be accurate. In addition, the opalescent diffuser plate 1 significantly reduces the amount of light incident on the optical fiber handle 3, and the sensitivity of the spectrophotometer is considerably reduced.
Since the light receiving angle is wide (the solid angle of incidence is 2π at maximum), the amount of incident light can be considerably increased by bringing the light source 8 to be measured closer to the opalescent diffuser plate 1. (At this time, care must be taken to ensure that the distribution of irradiance on the opalescent diffuser plate 1 does not become uneven.) Also, in the monochromator S, almost the entire light-receiving surface of the concave diffraction grating 7 is used. , the monochromator 5 can be used under the brightest conditions. Further, with the above configuration, since almost no light from the entrance slit 6 leaks outside the concave diffraction grating 7, stray light inside the monochromator 5 can be reduced at the same time.

Effects of the Invention As described above, the spectrophotometer of the present invention includes a monochromator, a light transmitting diffuser plate, a light-shielding hood, and an optical fiber handle whose size and positional relationship are set according to the conditions of the optical system inside the monochromator. By combining them, it is possible to eliminate errors caused by differences in the shape and size of the light source to be measured, the angle of incidence, etc., without significantly reducing the sensitivity of the spectrophotometer, and while reducing stray light inside the monochromator. It is possible to realize a spectrophotometer that can perform highly accurate spectrophotometry and colorimetry for any light source, even if the positioning with respect to the incident optical system is rough, and its practical effects are great.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a spectrophotometer according to an embodiment of the present invention, Fig. 2 is a block diagram of a spectrophotometer using an optical fiber handle in a conventional example, and Fig. 3 is a gonioreflection of a milky white diffuser plate. FIG. 3 is a diagram showing characteristics. 100. Opalescent diffuser plate, 290. Shade hood, 300. fiber optic handle, 400. Support, 508. Monochromator, 660. Entrance slit, 716. concave diffraction grating, 800. Measured light source

Claims (1)

[Claims] A monochromator whose opening angle from the entrance slit to the wavelength dispersion element is θ_m, one end of which is connected to the entrance slit of the monochromator, whose diameter is d and whose numerical aperture is N. A. is N.
A. ~sin(θ_m/2) or N. A. >sin(
an optical fiber handle of θ_m/2), and a light transmitting diffuser plate fixed at a distance L of L>>d from the other end of the optical fiber handle and having a diameter D of D~2Ltan(θ_m/2). . A spectrophotometer comprising: a light-shielding hood that shields light from a space between the light transmission diffuser plate and the end face of the optical fiber handle.