JPH0432828A - Instrument for measuring quantity of light reflected from original - Google Patents

Abstract

PURPOSE:To eliminate the need for using a D/A converter and to sharply shorten a measuring time by controlling the quantity of irradiating light so that the mean value of sample data for all picture elements in a reflected light measuring range coincides with the objective quantity of reflected light. CONSTITUTION:A halogen lamp 8 is lighted up by a lighting voltage to be a reference and a reflected light quantity measuring means 2 samples original reflecting density for all picture elements in the reflected light quantity measuring range and successively stores the sampled data in a memory. Then, information such as the maximum value, minimum value, mean value, and reflected light frequency distribution of the data is calculated from the sampled data by an objective reflected light quantity computing means 3 and the feature of an original is extracted. Since all the picture elements in the reflected light quantity measuring range are scanned only once, the succeeding scanning is executed only by plural proper points in the measuring range and the reflected light quantity data of the residual picture elements are identified by the reflected light quantity data of these points, the use of a D/A converter is eliminated and the measuring time can sharply be shortened.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an original reflected light amount measuring device used for controlling the original irradiation light amount in a document reading device, a copying machine, a facsimile machine, etc., and particularly relates to a method for adjusting the original irradiation light amount. The present invention relates to a device for measuring the amount of reflected light on a document in a manual copying machine or the like.

[Prior Art] In general, as shown in FIG. 5, for example, as shown in FIG. 5, a halogen lamp 8 or the like is used as an original irradiation light means to irradiate an original, and a predetermined amount of reflected light is controlled in a conventional digital copying apparatus. The reflected light 10 from the document within the measurement area (100 in Fig. 2) is converted into an electric signal 11 pixel by pixel by a CCD (charge-coupled device) sensor l serving as a means for measuring the amount of reflected light, and this electric signal 11 is reflected. Reflected light amount 1 by light amount calculation means 2
This reflected light amount 12 is used as an input signal to the subsequent irradiation light amount control means 4, and this control means 4 converts the reflected light amount 12
Based on this, a control voltage value 15 for controlling the lighting voltage of the halogen lamp 8 is calculated and outputted, and the lamp lighting means 7 changes the lighting voltage based on the control voltage value 15 to feed back the irradiation light amount of the halogen lamp 8. It's in control. Here, since the appropriate amount of irradiation light usually differs depending on the type and density distribution of the original, the target reflected light amount calculation means 3 calculates the target light amount 13 based on the above reflected light amount 12, and the amount of light reflected from the original 10 is calculated by the target reflected light amount calculation means 3. A control system is configured in which negative feedback is applied via the irradiation light amount control means 4 so that the irradiation light amount converges to the target light amount 13.

Normally, in a device equipped with such a control system, the control signal 15 to the lamp lighting means 7 is an analog signal, but in the circuit of the irradiation light amount control means 4 it is a digital signal, which is very expensive. It was necessary to provide a (digital/analog) converter.

Therefore, without using the /A converter, the irradiation light amount control means 4 outputs and displays a request to increase or decrease the irradiation light amount to the user of the device using the display means (not shown) on the operation panel. A conceivable configuration is that the user operates a manual control voltage setting means (not shown) to adjust the lighting voltage of the lamp 8 according to a request, thereby realizing control to increase or decrease the amount of irradiated light.

C Problems to be Solved by the Invention] However, when the lighting voltage is manually operated as described above, the following problems to be solved occur.

That is, when the above-mentioned reflected light amount measurement range is relatively wide, it takes time to scan this range with the CCD sensor 1, so it takes a long time for the irradiated light amount to converge to the target light amount. It is.

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide a document reflection light amount measuring device that does not require a D/A converter and can significantly shorten measurement time.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a storage means for storing the amount of reflected light at a first measured pixel group consisting of a plurality of pixels within a reflected light amount measurement range; a first calculation means for calculating the total amount of reflected light at a second pixel group to be measured, which is a true subset of the pixel group to be measured, and is made up of at least one pixel;
normalizing means for normalizing the amount of reflected light at all elements of the first pixel group to be measured stored in the storage means by the total;
After performing the normalization, the amount of reflected light at all elements of the first pixel group to be measured is identified using the standardized amount of reflected light and the total amount of reflected light at the second group of pixels to be measured. It is characterized by having a second calculation means.

[Function] In the present invention, all pixels within the reflected light amount measurement range are scanned once, and the obtained reflected light amount data is stored in a memory for each pixel, and subsequent scanning is performed at an appropriate point within the reflected light amount measurement range. This is done using only multiple points, and the reflected light amount data of the remaining pixels is identified using the reflected light amount data of those points.
A D/A converter is not required, and measurement time can be significantly shortened.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the circuit configuration of a document irradiation light amount control circuit according to an embodiment of the present invention. In the figure, a COD sensor 1 is composed of 128 reading pixels, and successively converts reflected light from a document into an electrical signal 11 according to a reading clock (not shown). The electric signal 11 obtained from the CCD sensor 1 is converted into reflected light amount data by the reflected light amount calculation means 2, and is converted into reflected light amount data, an, al, and an in FIG.
The reflected light amount data Van is stored in the internal memory in the order of pixels a3...amen.

Val, Va3---, Vam*n are stored (.Here, if there is a limit to the memory capacity,
Although it is possible to thin out every few pixels and store them in the memory, in the following, to simplify the explanation, pixels will not be thinned out.

Next, a procedure for controlling the amount of light irradiated on an original in this embodiment will be explained. The flowchart in FIG. 3 shows the control procedure.

First, the halogen lamp 8 is turned on at a reference lighting voltage via the lamp lighting means 7 (5TEPI), and the reflection density of the document at that time is determined by the reflection light amount calculation means 2 within the reflected light amount measurement range (as indicated by the broken line 100 in FIG. 2). All pixels within the frame are sampled (STEP 2).

Furthermore, the sample data is sequentially stored in the above-mentioned memory (STEP 3). Next, the maximum value, minimum value, and average value of the data are determined by the target reflected light amount calculating means 3 from the sample data stored in the memory.

Information such as the frequency distribution of the amount of reflected light is calculated to extract the characteristics of the document. For example, a target average amount of reflected light is set according to the characteristics of each document, such as the document being completely dark or having a wide range of density distribution (STEP 4).

As described below, the irradiation light amount is controlled so that the average value of sample data for all pixels within the reflected light amount measurement range matches the target reflected light amount.

Next, one point is selected as a specific measurement point from among all the pixels within the reflected light amount measurement range (STEP 5). As this selection criterion, for example, a pixel whose sample data has the maximum value is selected. The selected point is hereinafter referred to as r-specific measurement point 1. From now on, we will calculate the average reflected light amount by sampling all pixels within the reflected light amount measurement range (,
Calculate the average amount of reflected light only from data at specific measurement points.

The method for calculating the average amount of reflected light from the data of the specific measurement point will be described later, but first, in 5TEP6, the target amount of reflected light at the specific measurement point (hereinafter referred to as specific measurement point target amount of reflected light) is calculated.

Continued < 5 At TEP 7, the irradiation light amount control means 4 determines whether the target reflected light amount at the specific measurement point has converged to the target reflected light amount at the specific measurement point, and if it has not converged, a message indicating that the control voltage setting means 6 should be operated is displayed on the display means 5. Display (STE
P8). In accordance with this display, the user operates the manual control voltage setting means 6 to change the lighting voltage of the halogen lamp 8 via the lamp lighting means 7.
Increase or decrease the amount of light irradiated on the document. In the meantime, the processes of 5TEP7 to 5TEP9 continue to be looped until the amount of reflected light converges to the target amount of reflected light. At this time, in 5TEP9, sampling is performed only at the specific measurement point, so the cycle of display→sampling→convergence determination is shorter than when sampling is performed for all pixels within the reflected light amount measurement range.

Next, a method for calculating the average amount of reflected light from data at specific measurement points will be explained.

The relationship between the pixels within the reflected light amount measurement range obtained in 5TEP2 of FIG. 3 and the amount of reflected light is shown by the solid curve in FIG. Now, when representing the amount of reflected light Vi of each pixel (i is a pixel number from 1 to men), the average amount of reflected light E of all pixels within the reflected light amount measurement range 10a in FIG. 2 is calculated from the following equation (1). Seek.

E = (V1+V2+V3+-...+Vm umbrella n)
/men - (1) Here, if the maximum value of the amount of reflected light is Vk, then equation (22) is derived from equation (1).

E = (klVk+ to 2Vk+ to 3Vk+...-+
km * nVk)/m umbrella n (here, ki: Vi/Vk) = 5kVk/+*n - (2
) (Here, 5k=kl+, 2+, 3+-+km*n) Therefore, in 5TEP3 of FIG. 3, Sk is calculated and determined from the reflected light amount of each pixel stored in the memory.

If the documents are the same, ki will be a constant value regardless of the amount of irradiation light, and therefore Sk will be a constant. However, in order for ki to be a constant value regardless of the amount of irradiated light, it is assumed that shading correction is performed in each pixel of the CCD sensor 1.

Now, for the above reasons, once the reflected light amount of all pixels within the reflected light amount measurement range is calculated and the value of Sk is calculated for a specific measurement point (kth pixel), from then on, only the specific measurement point can be calculated. By measuring the amount of reflected light, the average amount of reflected light can be obtained.

In the above embodiment, one specific measurement point is specified, but a plurality of points may be specified. For example, consider a case where the specific measurement points are selected as the 5th, 6th, and 8th pixels.

The average amount of reflected light E in this case can be found from the following equation (3).

E” (Vl12+V3+---+■ffi umbrella n)/
rn umbrella n= (Vl umbrella (V5+V6+V8)/(V5+
V6+V8) v2 rate (V5+V6+V8)/(V5+V
6+V8)++ + 1 + -11-Fist
10V (men) * (V5+V6+V8)/
(V5+V6+V8)/men= (2+- to K1+
+K (men)) (V5+V6+V8)/m umbrella n
・−・ (3) KokoteKi = Vi/ (v5+V6
+V8) There is.

In the above equation (3), Ki is a constant. Therefore, E is (
V5+VB+V8), and as in the previous embodiment, the data of all pixels within the reflected light amount measurement range can be identified at a specific measurement point. If there is only one specific measurement point, the measurement data may not be reliable due to a defect in the CCD sensor 1, but if multiple specific measurement points are provided as in this example, reliability will be improved. do. The physical location of the specific measurement point at that time does not need to be randomly selected within the reflected light amount measurement range;
If adjacent pixels of the CD sensor 1 are selected, there is no need to move the sensor 1, and there is an advantage that the measurement can be completed in approximately the same time as when there is only one specific measurement point.

[Effects of the Invention] As explained above, according to the present invention, it is possible to obtain the effect that the measurement time can be significantly shortened.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the circuit configuration of a document irradiation light amount control circuit according to an embodiment of the present invention, Fig. 2 is a plan view showing the relationship between the original and the reflected light amount measurement range, and Fig. 3 Figure 4 is a flowchart showing the control procedure for document irradiation light amount in the embodiment of the present invention, Figure 4 is a graph showing an example of the reflected light amount of pixels within the reflected light amount measurement range of Figure 2, and Figure 5 is the original document irradiation light amount in the conventional example. FIG. 2 is a block diagram showing a circuit configuration of a control circuit. DESCRIPTION OF SYMBOLS 1... CCD sensor, 2... Reflected light amount calculation means, 3... Target reflected light amount calculation means, 4... Irradiation light amount control means, 5... Display means, 6... Control voltage setting means , 7...Lamp lighting means, 8...Halogen lamp, 9...Document. Figure 2 am+1 Figure 4 District 5

Claims (1)

[Scope of Claims] 1) Storage means for storing the amount of reflected light at a first pixel group to be measured consisting of a plurality of pixels within a measurement range for the amount of reflected light; and a true subset of the first group of pixels to be measured. , a first calculating means for calculating the total amount of reflected light at a second pixel group to be measured consisting of at least one pixel, and the amount of reflected light at all elements of the first pixel group to be measured stored in the storage means. normalizing means for normalizing the total amount of light by the total amount; and after the standardization, the first measured amount is determined by the normalized amount of reflected light and the total amount of reflected light at the second measured pixel group. 1. A document reflected light amount measuring device comprising: second calculation means for identifying the amount of reflected light at all elements of a pixel group.