JPS60141071A - Information reader - Google Patents

Abstract

PURPOSE:To remove an omission of reading-out of color information and to obtain faithful concentration reproducibility by multiplexing by providing a means to correct spectral sensitivity of a photodetector between a light source for illuminating originals and a photodetector to read-out optical information from the original. CONSTITUTION:An original 1 to be read out is radiated by a light source 2, and its reflecting light image is formed on a photodetector 4 through an image- forming lens system 3 consisting of plural lenses. For a means to correct spectral sensitivity of the photodetector 4, a filter element 5 is provided between the original 1 and the image-forming lens system 3. In light of spectral reflection ratio characteristics of the original 1, a spectral energy distribution of the light source 2 and spectral sensitivity of the photodetector 4, the transmissivity characteristics of the filter element 5 is decided, thereby spreading a setting range of a slice level. When gradation control of a density by multiplexing such as ternary and quaternary operations, characteristics of a filter element are properly selected and an output of density information of originals is set below a slice level; therefore a setting range of a slice level can be freely changed in the same manner as the binary operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information reading device, and more particularly to an information reading device that uses a spectral sensitivity correction element to obtain faithful reproducibility of document density.

Conventionally, in information reading devices that use a fluorescent lamp that emits green light as a light source and a CCI as a receiver, the output of the CCI is such that it is printed as white against the white background of the original to be read. If the output for other colors is lower than the set output, one dot with a certain density is printed.

However, in order to control the gradation of printing, instead of printing with one dot as described above, one dot is printed with multiple dots ((split, that is, multi-valued) depending on the difference in the output of the CCI). In reading devices that print, the setting of the output slice level is delicate, so a problem has arisen in which the white background of the document and the cyan information are not distinguished and are read as white. Below, I will explain this problem in detail.

FIG. 1 shows the spectral energy distribution of the light source, FIG. 2 shows the spectral sensitivity distribution of the light receiving element, and FIG. 6 shows the spectral energy distribution of the original. When examining the output of the light receiver based on these three characteristics, as is clear from FIGS. 1 to 6, the output shows the maximum value for a yellow original. If the output for this yellow original is 1'', then this 51
'', the output of the red original is ``0.15'' and the output of the blue original is ``0.17'', which is a small value. If you want to convert the slice level of the receiver output into two or six values, set the maximum output.
Suppose you set it to ``0.5'', which is half of ``1''. Then, both yellow and cyan have a CCI of ``0.5'' or higher)
Since it is an output, both are printed with the same number of dots, making it impossible to distinguish them from the white background in terms of density. As described above, the conventional device has a problem in that information is not read properly.

The present invention solves the above problems and provides a 12-bit information reading device that eliminates the omission of information reading and obtains faithful density reproducibility in density gradation control using multi-value processing. purpose.

In order to achieve the second object, the information reading device of the present invention takes into consideration the spectral energy distribution of the light source, the spectral reflectance characteristics of the document, and the spectral sensitivity of the light receiver, and includes a light source for illuminating the document;
By providing a means for correcting the spectral sensitivity between a light receiver for reading optical information from the document obtained by the illumination, multi-value conversion is achieved by providing an appropriate difference in the output level of the light receiver. The information is read by

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a schematic diagram showing an embodiment of the present invention.

In this system, a document 1 to be read is irradiated with light vJJp, 2, and the reflected light image is formed on a light receiver 4 via an imaging lens system 6 made up of a plurality of lenses. .

Furthermore, in this embodiment, as means for correcting the spectral sensitivity of the light receiver 4, a filter element 5 is used between the original 1 and the imaging lens system 6.
It is placed between.

Now, the filter element 5, which is the most characteristic feature of the present invention, will be specifically explained. For example, the original 1 shown in FIG. 4 has the spectral reflectance characteristics shown in FIG. 4, the light source 2 is a fluorescent lamp that emits green light having the spectral energy distribution shown in FIG. Assume that the CCD has the spectral sensitivity shown in Figure 2. In this case, a filter element 5 having transmittance characteristics shown by curve a in FIG. 6 is used. As is clear from the figure, the filter element 5 in this case is designed to cut off radiant energy with a wavelength of 450 nm or less, and at the same time reduce radiant energy with a wavelength of 490 nm or less. Therefore, the following effects are not exerted on the output of the light receiver 4 regarding color information.

Specifically, the output of the light receiver 4 before and after the insertion of the filter element 5 is compared for each color information based on FIG. In the figure, the vertical axis represents the output of the light receiver 4, and the horizontal axis represents color information. The output before and after insertion of the filter element 5 is shown separately by the white area and the hatched area, respectively. In addition, the output devices for each color information are shown relative to each other when the output of a yellow original is "i". Then, by inserting the filter element 5, the red original remains unchanged at '0.15', the blue original changes slightly from '0.17' to '0.12', and the cyan original changes slightly from '0.17' to '0.12'. 0.15'''
It can be seen that there is a significant change from "0.36" to "0.36".

Next, one filter element 5 having a function similar to that of two is added.
The setting of the slice level when binarizing the output signal of the photoreceiver 4 will be explained with respect to the case where it is not used and the case where it is used.

1) When the filter element 5 is not used, if the slice level is set to 0.7, for example, as shown by dotted line A, all documents other than yellow will have aK information. However, when the level is slightly lowered and set to 0.5 as shown by dotted line B, the cyan original as well as the yellow original no longer has density information. Therefore, information on the cyan original is missing.

11) When using filter element 5 When the slice level is set to 0, 7 or 0, 5, only the yellow original does not have a degree information, and the other colors have density information with a margin. can have. Even if the slice level is further lowered to 0.4 as shown by dotted line C,
All documents other than yellow can have density information.

As described above, by using the filter element 5, the setting range of the slice level is expanded, and setting with a margin becomes possible, and color information can be accurately distinguished and binarized.

In the above description, the case where the filter element 5 is shown in FIG. 4 and is provided in the same position as shown in FIG. It may be provided inside the imaging lens system 6 (as an l'c filter element 56). The filter element 5C may be made by making it from an optical glass material having the same characteristics as the filter element 5C.There are no physically added elements in this combination. If one filter is used, a filter element 5d can be provided near (=J) of the light source 2.A similar effect can be obtained by providing absorption characteristics to the light source 2 itself.Furthermore, the filter element 5 Alternatively, an element provided with a dichroic film may be used.

As mentioned above, by using one filter element 5 or the like, it is possible to expand the setting range of the slice level. This means that when performing density gradation control by multi-value conversion such as six-value conversion or four-value conversion, the characteristics of the filter element (for example, curve a or curve b shown in Figure 6) must be selected appropriately. However, if the output of the density information of the document is set to be below the target slice level, it is possible to freely change the setting range of the slice level as in the case of binarization.

As explained above, the present invention is equipped with a means for correcting the spectral sensitivity of the photoreceiver, thereby making it possible to eliminate omissions in reading color information and obtain faithful density reproducibility through multilevel conversion. Moreover, since the structure is simple, the production cost can be reduced, which is an excellent effect.

[Brief explanation of drawings]

Fig. 1 shows the relative spectral energy distribution characteristics of the light source, Fig. 2 shows the relative spectral sensitivity characteristics of the receiver, Fig. 6 shows the spectral reflectance characteristics of various documents, and Fig. 4 shows a schematic diagram showing an embodiment of the present invention. figure,
FIG. 5 is a schematic diagram showing another embodiment of the present invention, FIG. 6 is a diagram showing the transmittance characteristics of the filter element, and FIG. 7 is a diagram showing the relative output of the light receiver before and after using the filter element. 1. Document to be read, 2. Light source, 6. Imaging lens system, 4. Light receiver.

Claims (2)

[Claims] (1) In an information reading device having a light source for illuminating a document to be read and a light receiver for reading optical information from the illuminated document, there is a light source between the light source and the light receiver. An information reading device comprising: a spectral sensitivity correction means. (2) The information reading device according to claim 1, wherein the supplementary IF means is a filter element having a transmittance with a predetermined frequency characteristic.