JPS603272A - Original reader - Google Patents

Abstract

PURPOSE:To read various originals different from the range in density with high picture quality by normalizing automatically a density read from the original into a density region inherent in the device. CONSTITUTION:A picture signal proportional to the reflectance of an original 2 is inputted to a density normalizing circuit 7 via an automatic level set circuit 6. The density normalizing circuit 7 consists of an automatic level control section 8, a parameter processing section 9, and a parameter converting section 10. An input device 11 inputs a density parameter DW (white parameter) and a DB (black parameter) to the normalizing circuit 7. The normalizing circuit 7 normalizes automatically the density read from the original to the density region inherent in the device within an upper and a lower limit set by the input device 11. Through the constitution above, various originals with different density range are read with excellent picture quality without troublesome operation such as manual adjustment of the gain and bias of the signal system by having only to input a proper density parameter.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a document reading device for reading images of documents, photographs, drawings, and the like.

2. Description of the Related Art Conventional Structures and Problems Generally, document reading devices have a density range (signal level range) unique to the device. In order to read a document with good image quality, it is necessary to match the density range of the document with the density range of the document.

However, with conventional document reading devices, the gain, bias, etc. of the signal system are manually adjusted at the manufacturing stage in order to match the density range of the original with the above-mentioned density range, assuming a mark-like document. It is now set. For this reason, when a document whose density range is considerably different from that of a standard document is read, problems such as blurred images and poor gradation occur.

Well, sometimes you have to intentionally manipulate the reading image quality,
With conventional equipment, the only option was to manually adjust the gain and bias of the signal system, which was practically impossible.

Purpose of the Invention The present invention solves the above-mentioned conventional problems, and makes it possible to read various originals with high image quality without the need for troublesome adjustment operations, and to change the reading image quality arbitrarily. The purpose of the present invention is to provide a document reading device that can perform the following functions.

Structure of the Invention The present invention automatically normalizes the density read from an original to a density range (image signal level range) specific to the device, and also sets the upper and lower limits of the density range of the original to be normalized as a density parameter. The above-mentioned object is achieved by configuring the document reading device so that the white parameter and the black parameter can be arbitrarily set.

That is, the document reading device according to the present invention includes means for photoelectrically scanning a document and outputting a level vxO image signal proportional to the reflectance of the document, and means for inputting density parameters Dw and DB of arbitrary values. Recording signal and the above density parameter D
W and DB are input, and the level VoutO according to the formula
The apparatus is characterized by comprising means for outputting an image signal.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram of a document reading device according to an embodiment of the present invention. In this figure, 1 is a manuscript table;
Original 2 is placed on top of it. 3 is a laser light source that illuminates the original 2, and 4 is a photo multiplier. The photomultiplier 4 outputs an image signal proportional to the reflectance of the original 2, and this image signal is amplified by a preamplifier 5 and then input to an automatic level set circuit 6.

This automatic level set circuit 6 outputs A when a white reference surface with an absolute density of 0 is photoelectrically scanned by the photomultiplier 5.
1 is a circuit that corrects the level of the image signal so that it remains at a constant level Vo over one scanning section. In other words, the automatic level setting circuit corrects image signal distortion and level fluctuations due to seven per cent variations in the amount of illumination light on the document surface and variations in sensitivity of the photo multiplier 4. Therefore, if such image signal distortion and level fluctuations can be ignored, the automatic level set circuit 6 may be omitted.

7 is a density normalization circuit, and an automatic level control section 8. Parameter processing section 9. and parameter conversion section 10
The details will be described later. 11 is a density parameter Dw (white parameter) in the normalization circuit γ,
This is a manual device that inputs Da (black parameter). As this input device 11, for example, a keyboard device is used.

Here, density normalization by the density normalization circuit 7 will be explained with reference to FIG. In this figure, Vw is the output A of the automatic level set circuit 6 when the photomultiplier 4 reads the density (Dw) specified by the white parameter Dw.
The image signal level obtained in 1, VB is the black parameter I)a
This is the image signal level when reading the specified density (DB). The concentration normalization circuit 7 adjusts Vw-LB so that Vw and VB match the upper limit level (■0) and lower limit level (0 volts) of a signal level range (concentration range) unique to the device, respectively.
The image signal at the level Vx between Di-DB and the density Dlr between
) to the level Vout.

The arithmetic expression for this normalization will be explained next.

The levels of both signals output from the photo multiplier 4 are proportional to the reflectance of the original, and the image signal 1/''<
Les V W , V B , V X and concentrations Dw, DB
, DxO have the relationship shown in equations 1 and 2.3.

vw-4010~D w , , , , 1VB=VO
-10-DB ...-2Vx=Vo-10" --
----3 Furthermore, in order to perform the above-mentioned normalization, the following equation must hold true for K.

Vw-VB Substituting equation 12, equation 22, equation 3 into equation 4, Vo-10
DB-Vx Vout=--1...5 l-1o DBDW. Concentration normalization circuit 7 performs normalization by computing Equation 5. However, as will be described later, the density normalization circuit 7 in this embodiment is configured to execute Equation 6, which is equivalent to Equation 5.

. . . 6 FIG. 3 is a detailed block diagram of the density normalization circuit 7. First, the parameter conversion unit 10 will be explained as follows: 18.1
9 is a latch circuit, 2o is a subtraction circuit, and 21.22 is a bus interface. The latch circuits 18 and 19 each latch the black parameters DB and DW inputted in 8-bit parallel from the input device 11 (FIG. 1).

The subtraction circuit 2° calculates the difference data (
DB-DW). This data (DB-DW) is sent to the parameter processing section 9 via the bus interface 22. In addition, the black parameter DB latched in the latch circuit 18 is
It is input to the parameter converter 9 via the parameter converter 9.

The parameter conversion section 9 includes a conversion ROM 23 and a latch circuit 24.
．． Consists of 25. Conversion) (0M23 works as a logarithmic converter, uses the data input from the parameter conversion unit 10 as an address, outputs data (-1o /10) to the black parameter DB, and converts the data (DB-DW)
Data (10DB-Dw,) is output for. The former data (-10/10) is latched by the latch circuit 25, and the latter data (10-1) is latched by the latch circuit 24.

Note that the parameter processing section 9 and the parameter conversion section 1Q
Internally, all data is treated as 8-bit parallel data.

The automatic level control section 8 uses the image signal inputted from the automatic level set circuit 6 (FIG. 1) and the data inputted from the parameter processing section 9 to execute the normalization calculation of the above-mentioned formula 6, and performs normalization. The output image signal is sent to the output A2, and its configuration will be described below.

26 is an operational amplifier whose non-inverting input is connected to resistor 2.
7, and is connected to the output A1 of the automatic level set circuit 6 (FIG. 1) via the d resistor 28, and coupled to the output of the operational amplifier 26 via the resistor switching circuit 29. The resistance value of the resistance switching circuit 29 is the data (-10
DB/1o), and a signal obtained by multiplying the image signal input from the automatic level set circuit 6 by (-10DB/1o) is output from the operational amplifier 26.

Reference numeral 30 denotes an operational amplifier, which is provided with negative feedback through resistors 31 and 32 so that it functions as an amplifier with a voltage amplification factor of 1. A voltage source 33 is connected to the inverting input of the operational amplifier 30.
A constant voltage vO/10 is applied, and the non-inverting side input is coupled to the output of the operational amplifier 26 at the previous stage. Therefore, the signal output from the operational amplifier 26 is given a constant voltage Vo/1o 7J[].
A signal at a level of (Vo-10''-Lx)/1o is obtained at the output of the operational amplifier 30.

34 is an operational amplifier, the non-inverting side input is grounded via a resistor 35, and the inverting side input is coupled to the output via a resistor 36. The inverting side input is connected to the output of the preceding operational amplifier 30 via a resistance switching circuit 37 whose resistance value changes stepwise according to the output data (1oDB-Dw-1) of the latch circuit 24. The output of the operational amplifier 34, that is, the output A2 of the concentration normalization circuit 7, is a signal obtained by multiplying the output signal of the operational amplifier 30 by 10/(1-10I)B-D, that is, both normalized by the above-mentioned 2〇. A signal is output.

FIG. 4 is a circuit diagram of the resistance switching circuit 29, 37. In this figure, eight resistors 40-47 are connected in series between terminal 38 and '39, and these resistors 4o-47 are connected in series between terminals 38 and '39.
Contact points 482L to 5 of relays 48 to 55 for each of 4γ
5? L are connected in parallel. 56-63 are relays 48
55, and drives the corresponding relays 48 to 55 to output contacts 48a to 55 according to the state of the corresponding bit of the 8-bit data input from the terminal 64 (output data of 25 in the latch circuit 24). By turning on/off 552L, the resistance value between terminals 38 and 39 is switched.

When reading a document using the document reading apparatus described above, the operator first inputs the density parameters 117'f)w, DB through the input device 11. The values of the density parameters DW and DB can be arbitrarily determined depending on what kind of image quality is required. For example, original Kf:
If you want to faithfully read the density of S, measure the density of the whitest part and the blackest part of the document, manually set the white parameter Dw with a value corresponding to the former density, and then manually set the white parameter Dw with a value corresponding to the latter density. Input the black parameter DB. Then, the image signal obtained by photoelectric scanning of the original is normalized by the density normalization circuit γ so that it is faithfully reproduced over the entire original density range. In this way, by appropriately determining the values of the density parameters DW and Dn depending on the document, various documents can be read with good image quality.

If you want to read a document with a slightly blurred image quality, input a black parameter DB having a value corresponding to a density lower than the density of the blackest part of the document. In this way, the image signal is normalized to be biased toward black, so that it is possible to read an image with a slightly blurred appearance.

On the other hand, if you desire an image quality with a slight blurring, you can input a white parameter Dw with a value corresponding to a higher density than the whitest part of the document and normalize the image signal.

Similarly, the read image quality can be varied in various ways by selecting the values of the white parameter DW and the black parameter DB.

Note that the concentration normalization circuit 7 of the above embodiment was configured to perform normalization by the calculation of 2〇 which is a modification of Equation 5, but Equation 6 itself is not yet capable of executing other equivalent transformations. It may be configured as follows.

In the above embodiment, the photomultiplier 4 is used to photoelectrically scan the original, but other image pickup devices such as a COD image sensor may also be used.

Furthermore, a densitometer can also be used as the input device 11.

Effects of the Invention As described above, the document reading device according to the present invention includes means for photoelectrically scanning a document and outputting an image signal at a level proportional to the reflectance of the document, and means for inputting a density parameter having an arbitrary value. Since it has means for normalizing the image signal according to the density parameter, it is possible to obtain the a-degree parameter with an acceptable value without having to perform troublesome operations such as manually adjusting the gain and bias of the signal system as in the past. By simply inputting information, various originals with different density ranges can be read with good image quality, and the read image quality can be varied in various ways.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a document reading device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of normalization, FIG. 3 is a detailed block diagram of an a degree normalization circuit, and FIG. 4 is a resistance switching circuit. FIG. 1...Document stand, 2...Document, 3...Laser light source, 4...°multiplier, 5...
・Preamplifier, 6... Automatic level set circuit,
7... Concentration normalization circuit, 11... Human powered device.

Claims (1)

[Claims] A level V proportional to the reflectance of the original is obtained by photoelectrically scanning the original.
means for outputting an image signal of x; means for inputting flexibility parameters DW and DB of arbitrary values; and an image signal having a level Vout that satisfies: A document reading device comprising means for outputting.