JPS58156839A - Optical measuring apparatus - Google Patents

Abstract

PURPOSE:To make an apparatus simple and inexpensive, by constituting so that a light diffusion means diffusing and passing through incident light is included and this means is inserted into an optical axis of a main illuminating system crossing nearly vertically. CONSTITUTION:A diffuser for spot magnification 60 is provided between a light shading plate 40 and a condenser lens 50 and is inserted into an optical axis of a main illuminating system crossing nearly vertically as shown by an arrow mark E. On this occasion, the diffuser 60 is made of flat board sand scattered glass etc. and incident light from its one hand face is diffused and is transmitted to the other face by the diffuser 6. An auxiliary light source or lens for spot magnification for illumination of monitoring is not used for this optical measuring apparatus and construction of the apparatus is simplified by using the simple diffuser, and also the price of the apparatus is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical measuring device for measuring optical properties, such as optical density, transmittance, reflectance, etc. of samples to be measured such as materials and printed matter.

Such optical measurement devices are used, for example, in scanners, densitometers, microphotometers, etc., and generally include a light source and a light-shielding device having an aperture that defines an illuminated area of a sample to be measured whose optical properties are to be measured. It has a plate, first lens means for focusing the light beam from the light source onto the aperture of the light shielding plate, and second lens means for forming an image of the aperture of the light shielding plate onto the sample to be measured.

Accordingly, when measuring the optical characteristics of the sample to be measured, the image of the aperture formed by the light focused on the aperture of the light shielding plate is projected onto the sample to be measured by the second lens means. A region of desired area on the surface of the measurement sample is illuminated by the light source.

In order to locate the desired area of the sample to be measured or to focus the image formed on that sample,
The position and degree of focusing of this illumination spot on the sample to be measured must be observed by means of a monitoring device. However, since the diameter of the illumination spot formed on the sample is generally very small, a method is generally used in which the sample is illuminated with a monitoring spot having a larger diameter than the measurement illumination spot.

In the prior art, there is an optical measuring device that is provided with an auxiliary illumination system separate from the main illumination system for monitoring. This auxiliary lighting system includes an auxiliary light source, a condenser lens,
Mirrors, half mirrors, etc. are installed, and the half mirror is used so that it intersects with the optical axis of the main illumination system only when monitoring.
is inserted into the sample, and a large-diameter monitoring spot is projected onto the sample by an auxiliary light source through this half-1 mirror. In a conventional optical measurement apparatus that uses an auxiliary illumination system in addition to the main illumination system, the configuration of the optical system becomes extremely complicated due to the presence of the auxiliary illumination system, and the apparatus itself becomes large.

Instead of providing such an auxiliary illumination system, there is an optical measuring device that inserts a lens in the optical path of the main illumination system to enlarge the illumination spot only during monitoring. However, the lens itself is expensive, and there is also the difficulty of aligning the optical axis of the lens with the optical axis of the main illumination system when the lens is inserted for monitoring.

Another method is an optical measuring device in which the aforementioned light shielding plate is replaced with one having a different diameter for monitoring and measuring. That is, when monitoring, a light-shielding plate having an aperture with a diameter larger than the aperture used for measurement is inserted into the optical axis of the main optical system. However, this is because the diameter of the opening is large.
A condenser lens that uniformly illuminates the entire aperture must be used as the first lens means.

Therefore, it is an object of the present invention to overcome the drawbacks of the prior art and to provide an optical measurement device that is simple in structure and easy to operate.

This object is achieved by an optical measuring device according to the invention as follows. That is, this device includes a light diffusing means for diffusing and passing incident light, and the light diffusing means includes a first optical axis extending from the aperture of the light shielding plate to the second lens means.
and a second position that does not block the light from the aperture to the second lens means, and when in the first position, the light from the aperture of the light shielding plate to the second lens means is selectively selected. By diffusing the light, a relatively wide area on the sample to be measured is illuminated.

The present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram showing, as an example, a scanner to which an optical measuring device according to the present invention can be applied. In the same figure, the cylindrical surface of the rotating drum 100 drawn by the imaginary line is actually formed of a transparent material, and a sample 3, such as a photographic material or a printed matter, whose optical density, transmittance, reflectance, etc. are to be measured is placed on top of it. Set. Inside this rotating drum 10, one arm 16 of a U-shaped casing 12, also shown in phantom lines, is inserted in the axial direction of the drum, and the other arm 14 is inserted along the surface of the drum 10. is placed parallel to. As shown, one arm 1 of the housing 12
A light source 1 is arranged inside the arm 6, and a light receiver 8 such as a photodiode is arranged in the other arm 16. An optical system consisting of suitable lenses and mirrors is arranged inside the arms 16 and 14, the optical axis of which emerges from the light source 1, passes through the sample 3 of the drum 10, as indicated by the solid line 18, and enters the receiver 8. It forms a U-shape in the opposite direction to the housing 12 so as to reach the target. Thereby, light corresponding to the optical density, transmittance, and reflectance of the sample 3 is received by the light receiver 8, and such optical characteristics of the sample 3 can be measured.

As shown in the figure, a mirror 61 such as a half mirror is disposed obliquely to the optical axis of the light receiving system, and an image of the illuminated area of the sample 3'' is formed on the screen of a monitor device 62. As will be explained later with reference to FIG. 2, the monitor device 62 rotates the drum 10 to move it onto the optical axis 18 in order to search for a specific measurement area on the sample 3, and monitors the illumination system and light receiving system. This is a device that monitors the state of imaging on the sample 3 in order to adjust the focus.

Note that this example shows the case where sample 3 is optically transmissive, but when measuring an optically reflective sample, both the illumination system and the light receiving system of the optical system should be placed outside the drum. A location method is used.

FIG. 2 shows an example of a conventional optical measurement device that is applied to a scanner such as the above, and to which the present invention can be applied.

In this figure, for convenience of explanation, the light m18 in FIG. 1 is shown as a straight line, and elements similar to those shown in FIG. 1 are designated by the same reference numerals. In this conventional device, the light source 1
The light generated is focused onto the sample 3 by the condenser lenses 30 and 50 and the illumination aperture 42, and a light spot of the desired diameter is formed thereon. The part of the sample 30 illuminated by this light spot is imaged by the pickup lens 4 and the magnifying lens 5,
The image is formed on the disk 6. Focusing on the surface of the disk 6 is performed by moving the pickup lens 4 in the direction of the optical axis as shown by arrow A.

As shown in the figure, the disc 6 has a plurality of apertures 81 to S9 (nine in this example) having different diameters, and by rotating the disc 6 as shown by arrow B, a desired diameter can be obtained. Aperture can be selected. The entire disk 6 is optically opaque and blocks light, and only the apertures 81 to S9 are optically transparent. For example, in this figure, the aperture S9 is located on the optical axis, so that out of the image of the sample 3 formed on the surface of the disk 60, only the opening of the aperture S9 is focused onto the light receiver 8 by the focusing lens I. reactor. For example, the diameter of the apertures 81 to S9 is 1 to 32 mm.
If the magnification of the light receiving system from the sample 3 to the apertures 81 to S9 is 100, the diameter of the measurement area of the sample 3 is 10 to 320 μm.

As is clear from FIG. 2, in this example, the mirror 61 is disposed between the pickup lens 4 and the magnifying lens 5,
The image on the sample 3 is formed on the screen of the monitor device 62.

Also, as mentioned above, two condenser lenses 30 and 50
A light-shielding plate 40 having an illumination aperture 42 is provided between the two, and is optically opaque except for the aperture 42.

The illumination aperture 42 is, for example, a circular aperture, and the illumination aperture 42 is, for example, a circular opening.
Forms a lighting spot along the path of the temple. While observing the imaging state of the image on the sample 3 projected on the screen of the monitor device 62, the measurer moves the pickup lens 4 in the direction of arrow A to focus the light receiving system. 10 is rotated or slid in the axial direction to move the region to be measured on the sample 3 onto the optical axis of the optical system.

3 and 4 show examples of optical measuring devices according to the prior art, in which elements similar to those in FIG. 2 are designated with the same reference numerals. First, in the example shown in FIG. 3, an auxiliary illumination system is provided separately from the main illumination system extending from the light source 1 to the sample 3. and a half mirror 36. The half mirror 36 can be inserted into the optical axis of the main illumination system as shown by arrow C, or can be taken out from there. The illumination spot formed on the sample 3 by the main illumination system usually has a very small diameter and is inappropriate for observation by the monitor device 62. Therefore, when searching for a specific position on the sample 3 or when focusing the main illumination system, insert the half mirror 36 so as to intersect the optical axis of the main illumination system to direct the light from the auxiliary light source 2 to the third It leads to the main illumination system as shown by the dotted line in the figure. As a result, an image 64 of the illumination aperture 42 of the main illumination system is formed on the surface of the sample 3, and a spot 64 is superimposed on this.
A spot 66 with a larger diameter is formed. In this conventional device, the diameter of the monitoring spot 66 can be adjusted by changing the focal length of the condenser lens 32.

Instead of using such an auxiliary illumination system, in the prior art example shown in FIG. 4, a spot enlarging lens 52 is provided between the condenser lens 50 and the sample 3.
A monitor device d monitors the image of the illumination aperture 42 on the 0 surface.
When monitoring with n 62, this spot enlarging lens 52 is moved in the direction of the arrow shown in FIG. 4 (11) and inserted into the main illumination system so that it intersects with the optical axis. As a result, a monitoring spot 66 is formed on the surface of the sample 30 instead of the measurement spot 640. This spot enlarging lens 52 has a function of blurring the focus of the image of the aperture 42.

However, the conventional optical measuring devices shown in FIGS. 3 and 4 are equipped with an auxiliary illumination system (FIG. 3) in order to form a monitoring spot 66 on the surface of the sample 30. A separate lens for spot magnification is provided (Figure 4). However, such an auxiliary illumination system has a complicated configuration, and it is difficult to align the optical axis of the narrow spot enlarging lens with the optical axis of the illumination system. It is also not a good idea to use one.

FIG. 5 is a diagram conceptually showing the configuration of an embodiment of the optical measuring device according to the present invention. In this Figure, elements similar to those in Figure 2 are designated by the same reference numerals (12). In the illustrated embodiment, a spot enlarging diffuser 60 is provided between the light shielding plate 4° and the condenser lens 50.
is provided, which can be inserted into the main illumination system so as to be substantially perpendicular to the optical axis of the main illumination system, as shown by arrow E in the figure. The diffuser 60 is, for example, a flat plate of sand-glazed glass or the like, and diffuses light incident on one surface thereof and transmits the light to the other surface.

When actually performing optical measurements using the light receiver 8, the diffuser 60 is retracted to the position shown by the solid line in FIG. image at the position. In reality, the filament image of the light source 1 is formed, so the focus position is slightly shifted.

This illumination aperture image is imaged onto the sample 3 by a condenser lens 50 to form a measurement illumination spot 64 thereon.

The diameter of the measurement illumination spot 64 is usually set to about 1 threshold, for example, when a diameter of 300 μm or less is selected as the diameter of the apertures 81 to s9 on the light receiving side.

Next, in order to search for a specific area on the sample 3 or to focus the image formed on the sample, the diffuser 60 is inserted almost perpendicularly to the optical axis of the main illumination system as described above. Then, the condenser lens 50 projects the illumination spot formed on the diffuser 60 onto the surface of the sample 3 in a largely blurred form. Therefore, a monitoring spot 66 having a larger diameter than the measuring spot 64 is formed on the surface of the sample 30, and the image enlarged and projected by the monitoring device 62 can be easily monitored. The size of the image of the spot 66 projected on the screen of the monitor device 62 needs to be about 25w++ in diameter.

If the diameter of the measurement spot 64 is 1 mm and a lens with a magnification of 5 times is used as the pickup lens 4, the spot diameter on the sample will be Since the image is enlarged to about 5 (twice) and projected to a diameter of about 25 Wn on the monitor device 620, a sufficient illumination spot for image observation can be obtained.

Note that the brightness of the monitoring spot 66 is darker than the measurement spot 64 because of the diffuser 60. However, since the measurement spot 64 is normally too bright to be observed with the monitor device 62, the degree of diffusion of the diffuser 60 is adjusted so that the brightness of the spot 66 is at a level suitable for observation. Roughness can be selected. Furthermore, when the diffuser 60 is inserted into the optical axis of the main optical system, the measurement spot 6
4, the degree of roughness of the sand-glazed glass of the diffuser 60 may be reduced.

The optical measuring device according to the present invention does not use an auxiliary light source, a spot, or a magnification lens for monitoring (15) illumination.
Since a simple diffuser is used, the configuration of the device is extremely simple and the cost of the device is reduced. Additionally, since the diffuser does not require precise optical axis alignment, adjustments during manufacturing and maintenance are also very simple.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing an example of a scanner to which the optical measurement device according to the present invention can be applied, FIG. 2 is a conceptual diagram illustrating the configuration of the scanner shown in FIG. 1, and FIGS. The figure is a conceptual diagram showing an example of an optical measuring device according to the prior art, and FIG. 5 is a diagram conceptually showing the configuration of an embodiment of the optical measuring device according to the present invention. Explanation of symbols of main parts 1...Light source, 30.50...Condenser lens,
40... Light shielding plate, 42... Lighting aperture. (16) Figure 1

Claims (1)

[Scope of Claims] A light source, a light-shielding plate having an aperture that defines an illumination area of a sample to be measured whose optical properties are to be measured, and a first lens that focuses a light beam from the light source onto the aperture of the light-shielding plate. and second lens means for forming an image of the aperture of the light shielding plate onto the sample to be measured, the apparatus comprising: a light diffusing means for diffusing and passing incident light. The light diffusing means has a first position intersecting the optical axis extending from the aperture of the light shielding plate to the second lens means, and a second position extending from the aperture to the second lens means.
and a second position that does not block light reaching the lens means, and when in the first position, diffuses the light reaching the second lens means from the aperture of the light shielding plate. An optical measurement device characterized by illuminating a relatively wide area on a sample.