JPH0327045B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention irradiates a reflective surface of a prism with light and detects the reflected light from the reflective surface, thereby detecting a detected object that is in contact with the reflective surface. The present invention relates to an unevenness detection method for detecting body unevenness and an unevenness detection information input device, and is used, for example, when an uneven pattern on the surface of a finger, that is, a fingerprint, is directly collected in real time.

[Prior art]

A conventional unevenness detection method will be explained in the case of fingerprint collection. FIG. 1 is a configuration diagram showing a conventional fingerprint pattern input device, in which 1 is a light source, 1a is a parallel beam of light that is the output light of the light source 1, 2 is a prism, 2a
is a reflective surface of the prism 2, 2b is an entrance surface of the prism 2, and 3 is an object to be detected, that is, a finger. 3a is a concavo-convex portion of the object to be detected 3, that is, a fingerprint. 4 is a television camera, and 5 is a processing device.

The conventional device shown in FIG. 1 includes a light source 1, an optical device that allows a beam of light from the light source 1 to be incident on an object 3 at an angle within a certain range, and a The prism 2 and the detected object 3 are equipped with a conversion device that converts optical information into electrical signals.
Fingerprint pattern information is obtained based on total reflection light and non-total reflection light caused by contact or non-contact with the uneven portion 3a. Furthermore, in general,
At the interface between glass or other transparent materials and air, total internal reflection occurs when the incident angle θ of the light beam from the light source exceeds the critical angle θ ₀ . On the other hand, in a portion where the object to be detected is in close contact with glass or other transparent material, total reflection does not occur due to the relationship between the refractive indexes of the media, and non-totally reflected light is generated. Therefore, in FIG. 1, on the reflective surface 2a of the prism 2, there are parts that undergo total reflection corresponding to the concave portions of the fingerprint, and portions that no longer undergo total reflection due to contact with the convex portions of the fingerprint. The fingerprint pattern is photographed as a contrast image by a television camera 4, converted from an optical signal to an electrical signal, and then processed appropriately by a processing device 5.

However, in such conventional detection methods and devices, even if the finger is removed from the reflective surface 2a after the fingerprint is collected by bringing the finger in close contact with the reflective surface 2a of the prism 2, substances such as finger oil remain on the reflective surface 2a. are doing. Therefore, for example, when the reflective surface 2a is irradiated with parallel light while the fingers are separated from the reflective surface 2a, the reflective surface 2a will reflect perfectly specularly if there is no residual substance on the reflective surface 2a. If the above-mentioned residual substance remains on the reflective surface 2a, the reflective surface 2a will not be completely specularly reflective, and a non-specularly reflective part will occur in a part of the specularly reflective part, which will become an afterimage. This obstructs accurate collection of fingerprint patterns from other fingers to be obtained next.

[Summary of the invention]

This invention was made in view of the above-mentioned conventional situation, and even if there is residual material on the reflective surface of the prism due to contact with the object to be detected, the presence of this residual material makes it impossible to accurately detect the unevenness of the object to be detected. The purpose is to suppress interference, and the above purpose is achieved by irradiating diffused light onto the reflective surface of a prism that is in contact with the object to be detected.

[Embodiments of the invention]

An embodiment in which the present invention is applied to fingerprint collection will be described with reference to FIG. In Figure 2,
1 to 5 are the same as those in Figure 1, 1 is the light source,
1a is a ray bundle of parallel light that is the output light of light source 1, 2
is a prism, 2a is a reflective surface of the prism 2, 2b is an entrance surface of the prism 2, and 3 is an object to be detected, for example, a finger. Reference numeral 3a indicates an uneven portion existing on the detection surface of the detection object 3, for example, a fingerprint of a finger. Reference numeral 4 denotes a conversion device disposed at a position to receive the reflected light from the reflective surface 2a of the prism 2, which converts the reflected light, that is, optical information, into an electrical signal. Ru. 5 is a processing device that performs processing for displaying, for example, unevenness information of the detected object 3, such as finger print pattern information, on, for example, a television receiver from the output electric signal of the converting device 4;
Alternatively, it performs processing for recording unevenness information on a recording medium (not shown) such as a videotape or a video disk. Reference numeral 6 denotes an optical diffusing section made of an optical diffusing plate disposed on the optical path between the entrance surface 2b of the prism 2 and the light source 1.

In the embodiment shown in FIG. 2, by making the light beam projected onto the reflective surface 2a of the prism 2 randomly diffused light, a background in which total reflection and non-total reflection coexist over the entire reflective surface of the prism 2 can be obtained. , thereby,
The afterimage caused by the residual substance on the reflective surface 2a caused by the contact of the object 3 with the reflective surface 2a is buried in the background, thereby removing the interference pattern caused by the afterimage. More specifically, when the parallel light from the light source 1 passes through the optical diffuser 6, the light flux projected onto the reflective surface 2a of the prism 2 becomes randomly diffused light, and the reflective surface 2a of the prism 2 undergoes total reflection. This results in a state in which both non-total reflection and non-total reflection coexist. That is, the background portion where the object to be detected is not in close contact with the reflective surface 2a is observed apparently as an optically diffusing surface. As a result, the influence of afterimages remaining in the background portion is significantly improved compared to the conventional method in which parallel light is projected onto the reflective surface 2a and total reflection in the background portion is utilized. In other words, as before,
The total reflection in the background area is no longer disturbed by the residual substance, and even if the residual substance remains in the background area, the reflected light in the background area is almost the same as when there is no residual substance in the background area. Nothing has changed.

On the other hand, the portion where the object to be detected 3 is in close contact with the reflective surface 2a has almost no total reflection on the reflective surface 2a, and exhibits the same characteristics as the conventional one.

In addition, in the above embodiment, the case where the optical diffusion plate 6 is disposed between the light source 1 and the prism 2 has been described, but this optical diffusion plate 6 can be provided by other means,
It goes without saying that this can be replaced by, for example, making the entrance surface 2b of the prism 2 a diffusing surface.
Therefore, the diffused light referred to in this invention does not mean the diffused light obtained only by the diffusion means shown in the examples.

〔Effect of the invention〕

As described above, this invention irradiates the reflective surface of the prism against which the object to be detected is brought into contact with diffused light, and the reflected light reflected from the reflective surface is applied to the reflective surface of the object to be detected. Since it detects the unevenness that exists on the surface that is in contact with the light source,
a prism arranged so that a reflective surface is irradiated with diffused light generated by the light from the light source passing through an optical diffusion section, and on which an object to be detected comes into contact with the reflective surface; The converter is disposed at a position to receive the reflected light from the reflective surface of the prism and generates an electrical signal in accordance with the reflected light, so that the previously detected convex portion of the object to be detected is located on the prism. Even if a residual substance remains on the reflective surface, the unevenness of the object to be detected can be detected with high performance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional apparatus for carrying out a conventional unevenness detection method, and FIG. 2 is a block diagram showing an embodiment of an apparatus for carrying out the unevenness detection method according to the present invention. In the figure, 1 is a light source, 1a is a beam of light, 2 is a prism, 2a is a reflective surface of the prism, 2b is an entrance surface of the prism, 3 is an object to be detected, 3a is an uneven part of the object to be detected, 4 is a conversion device, 6 is an optical diffusion section.
In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. Diffuse light is irradiated onto the reflective surface of the prism on which the object to be detected comes into contact with the reflective surface, and from the reflected light reflected from the reflective surface, the reflective surface of the object to be detected is applied. An unevenness detection method characterized by detecting unevenness existing on surfaces that are in contact with each other. 2. A light source, a prism arranged so that a reflective surface is irradiated with diffused light generated by the light from the light source passing through an optical diffusion section, and a prism with which a detected object comes into contact with the reflective surface; An unevenness detection information input device including a conversion device disposed at a position to receive reflected light from the reflective surface of a prism and generate an electric signal according to the reflected light. 3. The unevenness detection information input device according to claim 2, wherein the optical diffusion section is an optical diffusion plate disposed between the prism and the light source. 4. The unevenness detection information input device according to claim 2, wherein the optical diffusing section is formed on the entrance surface of the prism.