JPH04324857A - Method and device for evaluating defect of photosensitive film - Google Patents

Abstract

PURPOSE:To obtain a method and device of evaluating the defect of a photosensitive film used for a hologram, etc., prior to exposure. CONSTITUTION:Laser light 3 with the wavelength in which a photosensitive film 1 is not sensitized is applied to the photosensitive film 1 so that light which passes through the photosensitive film 1 smoothly may interferes with light which passes through the photosensitive film 1 after reflection on the face and back. In reference to formed interference fringes, the defect of the film is evaluated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for evaluating defects in photosensitive films for holograms or ordinary photographs.

0002

[Prior art and its problems] Photosensitive films, especially photosensitive materials for holograms, are required to have extremely high sensitivity and resolution compared to ordinary photographic photosensitive films. If there is any unevenness in the thickness, it will have a negative effect on the formation of a hologram, so it is necessary to accurately evaluate defects.

Defects in the photosensitive film after exposure can be evaluated accurately using known optical methods under various light sources, but defects increase in the process up to the end of exposure, and this method It is not necessary to inspect only defects in the photosensitive film itself, and therefore conventionally, evaluation has been performed visually in a dark room. However, the visual method causes deviations due to differences in evaluators, observation conditions, etc.
Not only is it impossible to evaluate objectively, but it is also impossible to perform a thorough inspection because the inspection is performed using weak light.

The present invention has been made in view of the above points, and an object thereof is to provide a method and apparatus for accurately evaluating defects in a photosensitive film before exposure.

[0005]

[Means for solving the problems] The evaluation method of the present invention is as follows:
A photosensitive film is formed by irradiating a photosensitive film with laser light of a wavelength to which the film is not sensitive, causing interference between the light that passes through the photosensitive film as it is and the light that is reflected and transmitted from the front and back surfaces of the photosensitive film. It is characterized in that defects in the film are evaluated using interference fringes, and the evaluation device includes a laser light source that emits light at a wavelength to which the film is not sensitive as a means for irradiating light onto the photosensitive film. an optical element that diffuses the light from the light source, and a material that is sensitive to the light at a position where the light transmitted through the film passes;
It is characterized by being arranged respectively.

[0006]

[Function] By irradiating a photosensitive film for holograms with laser light of a wavelength to which the film is not sensitive, the film will not be exposed to light, but the laser light will pass through a convex lens.
When light that is diverged by an optical element such as a concave lens or Fresnel lens and passes through as it is (hereinafter referred to as direct transmitted light) interferes with light that is reflected and transmitted after being reflected on the front and back sides of the film (hereinafter referred to as reflected transmitted light). , there is a phase difference between the directly transmitted light and the reflected transmitted light, but if the photosensitive film is completely parallel and the refractive index is uniform, no interference fringes will occur at all points, but in reality, foreign matter may be mixed in. Since there are thickness unevenness and refractive index unevenness due to
Interference fringes occur.

The interference fringes generated at this time are recorded on a photosensitive material sensitive to light of this wavelength, such as photographic paper, or projected onto a screen, etc., to evaluate defects. , the interval between interference fringes becomes shorter, and if there is a small diameter defect such as a foreign object, protrusion, or depression, concentric interference fringes or small diameter closed interference fringes are formed, so defects can be evaluated based on the pattern of interference fringes. can do.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings. FIG. 1 is a plan view of a main part showing an apparatus for evaluating defects in a photosensitive film in an example of the present invention, and FIG. 2 is a diagram showing an example of interference fringes obtained in this example.

As shown in FIG. 1, a photosensitive film 1 in which dichromate gelatin is coated on polyethylene terephthalate is held in a holder 2, and as a means for irradiating light, light having a wavelength to which the film is not sensitive is used, for example, 632.8 nm. A He-Ne laser light source 3 that oscillates light, a shutter 4, and a microscope objective lens (convex lens) 5 as an optical element that diverges the laser light are provided. For example, photographic paper 6 is provided as a material sensitive to light of .8 nm.

Using such a defect evaluation device, when the shutter 4 is opened for about 5 minutes and light with a wavelength of 632.8 nm is irradiated onto the photosensitive film 1, the laser light emitted by the microscope objective lens 5 is directly transmitted through the photosensitive film 1. The transmitted light and the reflected and transmitted light that is reflected on the front and back sides of the film and then transmitted interfere.At this time, there is a phase difference between the directly transmitted light and the reflected and transmitted light, but the photosensitive film is completely parallel and the refractive index is uniform. If so, interference fringes will not occur at all points, but in reality there are thickness unevenness and refractive index unevenness due to foreign matter, etc., so as shown in Figure 2, interference fringes will occur and will be printed on the photographic paper. , recorded. Thereafter, a fixing process is performed to prevent exposure to light even when irradiated with light.

In FIG. 2, in the horizontal direction, a section a, a section b,
When divided into three parts c, part a is good because the interval between interference fringes is large and there is little change in the thickness of the photosensitive film, but part A is good.
Concentric circles with small distances were formed in the area, indicating that a foreign object or protrusion was present in this area, and this was confirmed by a surface roughness meter and a microscope to be a 1μ convex portion, that is, a foreign object.

[0012] In part c, the interval between interference fringes is smaller than in part a, and the change in thickness is relatively large, and in parts B, C, and D, interference fringes are small and form a closed shape, resulting in defects due to uneven thickness. can be detected. When actually confirmed using a surface roughness meter, convex portions were confirmed in portions B, C, and D.

[0013] Compared to the other parts a and c, part b has the closest interference fringes and is the part where the thickness changes the most, but small, closed-shaped fringes are formed in this part. Therefore, it is presumed that there are no small-diameter irregularities, and that there is a band-like thickness unevenness. Whether this portion is considered to be defective or normal can be determined based on the accuracy of thickness unevenness required of the photosensitive film.

Although several closed shapes are formed in portion a, there is no need to regard these portions as defects since the intervals between the interference fringes are large. Although the present invention has been described above using preferred embodiments, the present invention is not limited to these embodiments, and various applications are possible.

Regarding the photosensitive film and laser oscillator, 488.0 nm, 51
Agfa 8E sensitive to 4.5nm Ar laser
56, a He-Ne laser that emits light at 632.8 nm, a ruby laser at 690 nm, and a ruby laser at 647.1 nm for silver salt photosensitive materials such as Agfa 10E56 or general photoresists.
By irradiating light from a Kr laser, evaluation can be performed using the same method and apparatus.

Regarding materials that are sensitive to the light transmitted through the photosensitive film, photographic paper is inexpensive, easily adaptable to larger sizes, allows for precise evaluation by enlarging it, and is easy to record. Therefore, it is most preferable to project the image onto a screen for evaluation, or to take an image with a camera or a video camera and record the interference fringes for evaluation. In this case, a shutter is not required.

As for the optical element for diverging the laser beam, it is possible to use not only ordinary optical elements such as a convex lens, a concave lens, and a Fresnel lens other than the microscope objective laser, but also mirrors such as a concave mirror and a convex mirror.

[0018]

According to the present invention, defects caused by uneven thickness of a photosensitive film used for holograms and the like can be precisely detected and evaluated before exposure.

[Brief explanation of drawings]

FIG. 1 is a plan view of essential parts of a photosensitive film defect evaluation apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of interference fringes obtained in an example.

[Explanation of symbols]

1 Photosensitive film 3 Laser light source 5 Microscope objective lens 6 Photographic paper

Claims (2)

[Claims] Claim 1: A photosensitive film is irradiated with laser light of a wavelength to which the film is not sensitive, and the light that passes through the photosensitive film as it is and the light that is reflected and transmitted from the front and back surfaces of the photosensitive film are interfered with. A method for evaluating a photosensitive film, characterized in that defects in the film are evaluated based on interference fringes formed. 2. A means for irradiating light onto a photosensitive film, comprising: a laser light source that emits light at a wavelength to which the film is not sensitive; and an optical element that diverges the light from the light source.
1. A defect evaluation device for a photosensitive film, characterized in that materials sensitive to the light are disposed at positions through which the light transmitted through the film passes.