JPS6058507B2 - optical graph reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical graph reading device that optically reads graphs recorded on thermal paper or graphs written on graph paper with an ordinary ballpoint pen or the like.

FIG. 1 shows a schematic configuration of the optical graph reading device proposed previously, in which a sheet of paper 1 on which a graph is written is illuminated with light from a columnar light source 3 while a driving roller 2 is used to scan the sheet of paper 1. 1 in the X direction (sub-scanning direction),
The paper 1 is scanned by a photoelectric conversion element 5 such as an image sensor through a lens system 4 in the y direction (main scanning direction) perpendicular to the direction, and the output signal of the photoelectric conversion element 5 is converted into a graph data converter 6. The graph written on the paper 1 is optically read by processing and displaying the processing output on the output display section 7.

The reading performance of such an optical graph reading device is PCS (Print Contrast Signal).
l) value, that is, the ratio of the reception level difference between the graph level and the background level in the photoelectric conversion element, is an important parameter, and the ratio of the reception level difference is usually used when converting the output of the photoelectric conversion element into a binary value. 0.4 to 0.5 or more is required.

However, in the past, when the target was a graph written with a ballpoint pen or thermal paper, such as the output of an X-Y plotter, the PCS value was less than the required value, and the reason why the PCS value could not be increased is explained below. Depends on the reason. In an optical graph reader, the output spectral characteristics of the photoelectric conversion element are the product of three characteristics: the reflectance spectral characteristics of the paper background and the graph, the light source energy spectral characteristics, and the sensitivity spectral characteristics of the photoelectric conversion element. The output of the photoelectric conversion element can be defined by the magnitude of the integral value over the entire wavelength range of the product characteristic. Therefore, regarding the optical reading device shown in Fig. 1, a tungsten lamp is used as the columnar light source.
A case was investigated in which a silicon photodiode was used as a photoelectric conversion element, and thermal paper on which a graph was recorded was used as paper. For example, the reflectance spectral characteristics of the thermal paper on which the graph is recorded are as shown in the characteristic curve in Figure 2, where the wavelength λ is longer than 700r17TL and the reflectance r(λ) in the graph area a is Since it is close to that of background region b, unless the wavelength λ is about 700r17TL or less, the PCS value will be too small and it will be difficult to read the graph. In addition, the light source energy spectral characteristics of the tungsten lamp are the third
As shown in the figure, the light source energy P(λ) is large in the range where the wavelength λ is longer than 700r17n.
A large amount of light having a range longer than 0r17n is irradiated onto the surface of the paper, and the PCS value becomes small. In addition, the sensitivity spectral characteristics of the silicon photodiode are as shown in Figure 4 when the wavelength λ is 7.
Since the sensitivity R(λ) is high in a range longer than 00r1n1, the PCS value becomes even smaller. For this reason, conventionally, it has been difficult to read graphs recorded on thermal paper or graphs written on graph paper with an ordinary ballpoint pen or the like. Note that if a fluorescent lamp is used instead of a tungsten lamp, it is possible to obtain an emission spectrum that is mostly in the visible light region, so it seems possible to solve the problem in the infrared region. Since this uses an AC power source, it is not suitable for looking at received level differences, and moreover, it is difficult to obtain a compact device.

In this respect, tungsten lamps are inexpensive, easy to obtain compact ones, and can be used with direct current, so they are widely used in optical reading devices. Further, although there are various types of spectral sensitivity characteristics of photoelectric conversion elements, silicon diodes in particular are generally widely used and easily available.

An object of the present invention is to increase the PCS value so that graphs written on paper can be reliably read.

Examples will be described in detail below. FIG. 5 is an explanatory diagram of an optical graph reading device according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 1 indicate the same parts, and 10 is a long wavelength light cutoff filter. As shown in the figure, a long wavelength light blocking filter 10 is provided between the paper 1 and the photoelectric conversion element 5 in close proximity to the photoelectric conversion element 5 such as an image sensor.
As shown in the characteristic curve of FIG. 6, the transmittance t(λ) of the long-wavelength light blocking filter 10 is determined when the wavelength λ is 700 nm.
It is significantly smaller over a longer range. Therefore, even if the reflectance spectral characteristics of the background of the paper and the graph signal line, the light source energy spectral characteristics, and the photoelectric conversion element sensitivity spectral characteristics have the relationships shown in FIGS. 2 to 4,
Since the long wavelength cutoff filter 10 removes infrared rays that degrade the PCS value, the PCS value can be improved.

The optical reading device of the present invention shown in FIG. 5 uses a drive roller 2 to move the paper 1 in the X direction (sub-scanning direction) while illuminating the paper 1 on which the graph is written with a columnar light source 3 ), the photoelectric conversion element 5 scans the paper 1 in the y direction (main scanning direction) perpendicular to the x direction via the lens system 4 and the long wavelength light cutoff filter 10. The output signal is processed by the graph data conversion section 6, and the processed output is displayed on the output display section 7.

In the above explanation, the long wavelength light blocking filter 10 is provided between the paper 1 and the photoelectric conversion element 5, but the long wavelength light blocking filter 10 can be provided anywhere within the optical path. For example, the shielding performance can be improved by providing both between the light source and the paper and between the paper and the photoelectric conversion element.

Further, although the case where the columnar light source 3 suitable for uniform illumination of the paper 1 is used is illustrated, a normal tungsten lamp may be used instead of the columnar light source 3. As explained above, the optical graph reading device of the present invention illuminates the paper 1 on which a graph is written with light from a light source such as the columnar light source 3, and uses the drive roller 2 or the like in the sub-scanning direction of the paper 1 to illuminate the paper 1 on which a graph is written. The light source such as the columnar light source 3 and the photoelectric conversion element 5 are connected so that the PCS value of the photoelectric conversion element 5 is improved by driving and scanning in the main scanning direction by the photoelectric conversion element 5 when reading the graph on the paper 1. Since the long wavelength cutoff filter 10 is provided in the optical path between the two, the graph written on the paper 1 can be reliably read.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the previously proposed optical graph reading device, Figure 2 is the reflectance spectral characteristic curve of paper, Figure 3 is the energy spectral characteristic curve of the light source, and Figure 4 is the sensitivity of the photoelectric conversion element. The spectral characteristic curve, FIG. 5 is an explanatory diagram of the optical graph reader according to the embodiment of the present invention, and FIG. 6 is the transmittance characteristic curve of the infrared light blocking filter. 1 is a sheet of paper, 2 is a drive roller, 3 is a columnar light source, 4 is a lens system, 5 is a photoelectric conversion element, 6 is a graph data conversion section, 7 is an output display section, and 10 is a long wavelength light blocking filter.

Claims (1)

[Claims] 1. In an optical graph reading device that illuminates a paper on which a graph is written and reads the graph on the paper by driving the paper in the sub-scanning direction and scanning the paper in the main scanning direction with a photoelectric conversion element, the above-mentioned A long-wavelength light blocking filter is provided in an optical path between the light source and the photoelectric conversion element for light that is emitted from a light source that illuminates the paper, is reflected by the paper on which the graph is written, and reaches the photoelectric conversion element. An optical graph reading device characterized by being provided with.