JPH0259501B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to an OCR (Optical Character Reader)
Regarding hand scanner.

Technical background of the invention and its problems Generally, as shown in FIG. An image is formed on a two-dimensional sensor 4 via a lens 3, and the image pattern is sent via a cable 5 to a character recognition section on the main body side and read. At this time, the area on the paper surface 1 that is photoelectrically converted by the two-dimensional sensor 4 is called a "field of view." Lamp 2 illuminates this viewing area, but what is required at this time is that the illuminance distribution within the field of view be as uniform as possible, although the scanner's inclination will vary due to manual operation, and that the illuminance distribution within the field of view be as uniform as possible. Even if the printed paper surface 1 is covered with a transparent vinyl film or has a glossy surface, direct reflected light from the lamp is difficult to enter the two-dimensional sensor.

In this regard, let's consider a conventional OCR hand scanner. First, as shown in FIG. 2, there is a device that simply illuminates directly with a lamp 2. However, there are cases where the inner wall of the scanner nose 6 is made of a reflective surface of white or the like, and the light reflected from this inner wall is utilized. In any case, in the case of this method, if, for example, a transparent vinyl film 7 exists on the paper surface 1 as shown in FIG. 3, and the scanner is tilted, the direct light from the lamp 2 will be specularly reflected and 4
There are some drawbacks that are easy to get into. Of course, the mounting angle of the lamp 2 may be increased to make it difficult for specularly reflected light to enter, but there are limitations because it is a manual operation type.
FIG. 4 shows the vertical distance in the field of view vs. photoelectric conversion output characteristic when using this method, and it can be seen that specularly reflected light is incident near the part indicated by the symbol A.

Next, as shown in FIG.
A diffuser plate 8 is installed between the two and illuminates the field of view like a surface light source. As a result, the direct light from the lamp 2 is softened by the diffuser plate 8, so that even if the specularly reflected light is incident on the two-dimensional sensor 4, it will be weaker than the direct light. However, under the situation shown in Fig. 3, the characteristics will be as shown in Fig. 6, which is the same as Fig. 4, and specular reflection light will be incident, making it unreadable. be.

Furthermore, as shown in FIG. 7, there is one in which a diffuser plate 9 is installed parallel to the optical axis φ connecting the lens 3 and the two-dimensional sensor 4. By using the diffuser plate 9 arranged in this way, the characteristics shown in FIG. 8 can be obtained even in the situation shown in FIG.
The problem of specular reflection on the glossy paper surface 1 is well improved. However, as shown in FIG. 9, there is a floating height g (3
mm), the illuminance distribution within the field of view is
As shown in Figure 0, both ends are dark and uneven. This is because the distance that the lamp light travels through the diffuser plate 9 differs depending on the position where the lamp light is incident on the diffuser plate 9.

As described above, the illumination optical system of conventionally used OCR hand scanners has various drawbacks even though it is an important part that determines the reading performance of a code reading device.

Purpose of the Invention The present invention was made in view of the above points, and it is difficult for specularly reflected light to enter even on a glossy paper surface such as a vinyl film, and the field of view is maintained even when various tilts or flying heights occur. The purpose of the present invention is to obtain an OCR hand scanner that has a nearly uniform illuminance distribution and has good reading performance.

Summary of the Invention The present invention provides a wedge-shaped diffuser plate whose tip tapers toward the paper surface, thereby making it difficult for specularly reflected light to enter the paper surface even if the paper surface is glossy due to a transparent vinyl film or the like. Even if various tilts or flying heights occur, the illuminance distribution within the field of view is nearly uniform and the reading performance is good.

Embodiment of the invention A first embodiment of the invention is shown in FIGS. 11 to 15.
This will be explained based on the diagram. In this embodiment, a diffuser plate 10 is provided which is parallel to the optical axis φ connecting the lens 3 and the two-dimensional sensor 4 and is arranged up to the opening so as to cover the lamp 2, similar to the diffuser plate 9. A wedge portion 10a in which the tip (lower end) of the diffuser plate 10 is wedge-shaped so that it tapers toward the paper surface 1.
was formed.

In this way, a wedge portion 10a is formed at the tip of the diffuser plate 10.
The presence of the lamp light can prevent the distance that the lamp light passes through the diffuser plate from varying depending on the position where it enters the diffuser plate, which is a drawback of the diffuser plate 9 method shown in FIG. 7. Thereby, even if the flying height g occurs as shown in FIG. 12, a uniform illuminance distribution can be obtained. Figure 13 shows the illuminance distribution in the field of view when g = 3 mm, and it is much improved compared to Figure 10, and even symbols and characters located at the edge of the field of view can be seen correctly. can be entered. Furthermore, even if there is a transparent vinyl film 7 or the like as shown in FIG. 14 and the scanner is tilted relative to the glossy paper surface 1, the characteristics shown in FIG. 15 can be obtained. According to the characteristics shown in Fig. 15, when compared with Figs. Even characters and symbols printed on the glossy paper surface 1, such as 1, can be input correctly. Therefore, according to this embodiment, a good illumination system can be provided in the optical system that is important for determining reading performance.

Next, a second embodiment of the present invention will be described with reference to FIG. 16. In this embodiment, the wedge portion 10a of the diffuser plate 10 has a curvature so as to bend toward the lamp 2 side. As a result, the lamp light diffuser plate 1
The incident angle to zero becomes more uniform, the reflected light on the surface of the diffuser plate 10 can be made more uniform, and as a result, the illuminance distribution in the field of view becomes more uniform.

Effects of the Invention As described above, the present invention is provided with a wedge-shaped diffuser plate whose tip tapers toward the plane of the paper, so that the distance that the lamp light passes through the diffuser plate depends on the position where the lamp light is incident on the diffuser plate. Therefore, even if the paper surface is glossy, it is difficult for specularly reflected light to enter, and even if various tilts or flying heights occur, the illuminance distribution within the field of view is nearly uniform.
This provides good reading performance.

[Brief explanation of drawings]

Figure 1 is a general side view, Figure 2 is a vertical side view showing the first conventional example, Figure 3 is a side view, Figure 4 is a characteristic diagram, and Figure 5 is the second conventional example. A vertical side view, FIG. 6 is a characteristic diagram thereof, FIG. 7 is a vertical side view showing the third conventional example, FIG. 8 is a characteristic diagram thereof, FIG. 9 is a side view, and FIG. 10 is a characteristic diagram thereof. FIG. 11 is a vertical sectional side view showing the first embodiment of the present invention, FIG. 12 is a side view, FIG. 13 is a characteristic diagram thereof, FIG. 14 is a side view, FIG. 15 is a characteristic diagram thereof, and FIG. The figure is a longitudinal sectional side view showing a second embodiment of the present invention. 1...paper surface, 2...lamp, 3...lens, 4
...Two-dimensional sensor, 10...Diffusion plate.

Claims (1)

[Scope of Claims] 1. In an OCR hand scanner equipped with a lamp for illuminating the paper surface, a condensing lens, and a two-dimensional sensor, the opening is approximately parallel to the optical axis connecting the lens and the two-dimensional sensor and covers the lamp. The invention is characterized by providing a wedge-shaped diffuser plate whose tip tapers toward the paper surface while being arranged.
OCR hand scanner. 2. The device according to claim 1, characterized in that the tip of the diffuser plate has a curvature bent toward the lamp side.
OCR hand scanner.