JPH0453357A - Shading correction method for optical line sensor - Google Patents

Abstract

PURPOSE:To eliminate the need for a trouble of the operator for each correction by correction both shading correction information sets of transmission and reflection in the state of absence of a medium. CONSTITUTION:An optical line sensor consists of light emitting element sections 1a, 1b, light receiving sections 2a, 2b and a control section 5. The control section 5 measures shading information of a transmitted light by the light emitting element section 2a and the light receiving section 2b while no medium dp to be detected exists, calculates a characteristic change in the optical line sensor from the measured transmitted light shading information and the past transmitted light shading information and corrects the shading correction information of a reflected light through the use of the characteristic change. Since the measurement of the shading correction information of a reflected light is not required, a trouble of loading of the medium by the operator is saved.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figure 5) Means for solving the problem to be solved by the invention (Figure 1) Working example (a) 1 Description of Embodiments (Figures 2 to 4) fb) Description of Other Embodiments Effects of the Invention [Summary] In an optical line sensor that obtains both transmitted light detection output and reflected light detection output from a medium to be detected, Regarding the shading correction method for correcting light and reflected light shading correction information, the purpose is to enable correction of both transmission and reflection shading correction information without a medium, and a light emitting part that irradiates light onto the detected medium and a , a light receiving section that receives light from the detected medium, performs shading correction using transmitted light shading correction information and reflected light shading correction information, and outputs a detected output of transmitted light from the detected medium and the reflected light from the light receiving section. In an optical line sensor having a control unit that obtains a light detection output, the control unit measures shading information of transmitted light by the light emitting unit and the light receiving unit in the absence of the detected medium, The characteristic change amount of the optical line sensor is calculated from the shading information of , and the past transmitted light shading information, and the reflected light shading correction information is corrected using the characteristic change amount.

[Industrial Application Field] The present invention relates to a shading correction method for correcting transmitted light and reflected light shading correction information in an optical line sensor that obtains both transmitted light detection output and reflected light detection output from a detected medium.

An optical line sensor is used to read the pattern of a detected medium such as a banknote and to recognize the detected medium.

In such an optical line sensor, if detection output is obtained from both reflected light and transmitted light, rather than only reflected light or transmitted light, more optical information can be obtained from the detected medium and recognition accuracy will be improved. improves.

On the other hand, in optical line sensors in which light-emitting elements and light-receiving elements are arranged in a row, errors occur due to variations in the receiving and emitting elements when optical information is read out as analog quantities, so it is necessary to correct them (so-called shading correction). be.

In this shading correction, it is necessary to cause a light emitting element to emit light, a light receiving element to receive light, and to obtain shading correction information by measurement so that there is no variation between the received and emitted light.

[Conventional technology]

FIG. 5 is an explanatory diagram of the prior art.

As shown in FIG. 5(A), as an optical line sensor, the number of light emitting parts 1a, 1 for one line is on both sides of the medium dp to be detected.
b, and the same number of light receiving sections 2a and 2b are provided.

A light emission amount control section 3a, 3b is connected to each light emitting section 1a, 1b, and a received light amount amplifying section 4a, 4b is connected to each light receiving section 2a, 2b.
are connected to the control CP connected to the storage device 6.
Controlled by U5.

The control CPU 5 sequentially scans the light emitting sections 1a and 1b according to the shading correction information in the storage device 6, and scans the light receiving section 2.
The light from the medium a'p is received by a and 2b, and the light reception output for the - line is obtained.

At this time, as shown in FIG. 5(B), the light emitting part 1a and the light receiving part 2
b is operated, the transmitted light output of the path ■, the light emitting part 1b and the light receiving part 2a are operated, the transmitted light output of the path ■, the light emitting part 1a and the light receiving part 2a are operated, and the reflected light of the path O is By operating the light emitting section 1b and the light receiving section 2b, four types of 1-line detection outputs are obtained: the output, and the reflected light output of path (3).

In such an optical line sensor, the light receiving and emitting parts may deteriorate, and it is necessary to correct the shading correction information accordingly.

For this reason, conventionally, in the case of transmitted light, the transmitted light shading correction information may be corrected by the above-mentioned routes (1) and (2) without the medium ctp.

On the other hand, in the case of reflected light, if the top of the medium is blank, the medium is inserted and the reflected light shading correction information is corrected through path O1■.

[Problem to be solved by the invention]

However, the conventional technology has the following problems.

(2) Reflected light shading correction requires the insertion of a medium, which requires an operator's effort for each correction.

■ Since it is necessary to insert the medium, the device cannot automatically correct it.

Therefore, an object of the present invention is to provide a shading correction method for an optical line sensor that can correct both transmission and reflection shading correction information without a medium.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

The present invention includes a light emitting section 1a that irradiates light onto a detected medium dp, and light receiving sections 2a and 2 that receive light from the detected medium dp.
b, and perform shading correction using transmitted light shading correction information and reflected light shading correction information,
In the optical line sensor, the control section 5 includes a control section 5 that obtains a transmitted light detection output and a reflected light detection output from the detected medium dp from the light receiving sections 2a and 2b.
Measure the shading information of the transmitted light by the light emitting part 1a and the light receiving part 2b in the absence of p, and calculate the characteristic change of the optical line sensor from the measured shading information of the transmitted light and the shading information of the past transmitted light. However, the shading correction information of the reflected light is corrected using the characteristic change.

[Effect]

The present invention focuses on the fact that fluctuations in transmitted light shading correction information and fluctuations in reflected light shading correction information are proportional, and measures transmitted light shading correction information that can be done without a medium, and corrects the transmitted light shading correction information. , the rate of change or change M) corresponding to the characteristic change is determined from the current or past shading correction information of this transmitted light, and the reflected light shading correction information is corrected based on this.

This eliminates the need to measure reflected light shading correction, which saves the operator the trouble of inserting a medium, and allows the apparatus to automatically approximate reflected light shading correction information regardless of the operator's presence.

〔Example〕

(a+ Description of an Embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of an information table thereof.

In the figure, 1a and 1b are the above-mentioned light emitting parts, respectively, and the LED
64 (light emitting diodes) are provided on one line (only 4 are shown in the figure).

30a and 30b are variable current sources, which are controlled by the control CPU 5.
The current according to the shading correction information from the LED
What is supplied to a and 1b, 31a and 131b are LEDs respectively
This is a selection circuit, and the control CPU 5 selects four LEDs.
, lb is selected and the light emission is scanned.

Reference numerals 2a and 2b each represent the aforementioned light receiving section, in which 64 photodiodes are provided on one line (only 4 photodiodes are shown in the figure).

40a and 40b are multiplexers, and the controller C
PU5 selectively outputs one of the four photodiodes 2a12b in synchronization with light emission scanning; 41a, 4;
1b is an amplifier circuit, and under the control of the control CPU 5, a photodiode 2a.

The output of 2b is amplified and output as a light reception output to the control CPU 5 and an external pattern LW recognition section.

The control CPU 5 performs correction control of shading correction information in addition to light emission control based on shading correction.

As shown in FIGS. 2 and 3, the memory (storage unit) 6 stores the paths ■, ■(
Transmitted light) shading correction information table 60.65
, and shading correction information tables 63 and 68 for routes (2) and (2) (reflected light) when the device is completed are provided.

Also, in the RAM of the memory 6, there are shading correction information tables 61.66 for routes ■ and ■ during operation, and shading correction information tables 64.6 for routes @ and @ during operation.
9, and characteristic change rate tables 62 and 67 for routes ■ and ■.

FIG. 4 is a processing flow diagram of an embodiment of the present invention, and FIG. 4(A) shows shading correction information setting processing when the device is completed;
FIG. 4(B) shows the shading correction information update process during operation.

(2) When the device is completed, insert the reference medium dp into the sensor as shown in FIG.

Reflection shading correction of the front surface is performed on path O using LEDla and photodiode 2a.

For example, the CPU 5 selects the first LED 1a by the LED selection circuit 31a, and selects the first LED 1a by the multiplexer 40.
The corresponding first photodiode 2a is selected by a, and the current of the first LEDla is changed to be larger (or smaller) than a predetermined value by the variable current source 30a, and the detection output of the photodiode 2a is kept constant. The current value when the value is reached is the shading correction data R3I
It is stored in the ROM table 63 as follows.

Similarly, the second LED 1 a on one line
------First, perform for the n-th LED ln, and RO
The reflection shading correction data R3I to R3n of the table M are entered in the table 63 of the table M.

Similarly, the process for path (3) is performed and the back reflection shading correction data R3I to R3n are stored in the table 68 of the ROM.

■ Next, remove the reference medium dp from the sensor.

Then, the transmission shading correction of the path (3) is performed using the LEDlb and the photodiode 2a, and the transmission shading correction data TOI to TOn is stored in the table 65 of the ROM.
Set to .

Next, using the LEDla and the photodiode 2b, the transmission shading correction of the path (2) is performed, and the transmission shading correction data TOI to TOn are set in the table 60 of the ROM, and the initial adjustment is completed.

In this way, when the initial setting of shading correction is completed, operation begins.

When the operation starts, the ROM standard table 60, 63.65
．． 68 initial shading correction data is loaded into the RAM operation table 61.64.66.69, and the CPU
5 is based on this, each L according to the route ■, ■, O20
Controls the light emission of the ED and performs shading correction.

Then, the correction (update) process of the shading correction data shown in FIG. 4(B) is performed at a predetermined period.

(2) The CPU 5 performs transmission shading correction for routes (2) and (2) without a medium.

For example, in route (2), LEDlb is made to emit light based on the transmission shading correction values TNI to TNn in the table 66, and it is determined whether a predetermined value of received light output can be obtained from the photodiode 2a.If not, the correction value is increased. , the level of the received light output is checked, and the operation table 66 in the RAM is rewritten with correction values TNI to TNn when the received light output level reaches a predetermined value.

Similarly, regarding the route (■), LEDla
emit light, check the light reception output level of the photodiode 2b, perform shading correction, obtain correction values TNI to TNn, and rewrite the operation table 61 in the RAM.

(2) Next, the CPU 5 calculates the transmission change rate ΔT for each sensor using the following equation.

ΔT m = (T Om - T N m ) / T
Om-(11, where m=1 to n And this is the RAM characteristic change rate table 62.67
Store in.

As a result, the rate of change in characteristics ΔTm of each sensor from the time of completion of the device for routes ① and ② can be obtained.

Furthermore, the CPU 5 compares the rate of change ΔTm in table 62.67 with a certain threshold Th, and if ΔTm>Th, an abnormality flag FE indicating exclusion from statistical processing is added to table 62.67 as an effect of partial contamination. stand up.

(2) Next, the CPU 5 calculates the average ΔS (ΔSa) of the ΔTm without abnormality flags in each table 62.67.

ΔSb) is obtained from the following equation.

ΔS−ΣΔ′p m/m−(21) This gives the average characteristic change rates ΔSa, Δs, and b in each of the transmission paths (■) and (2).

(2) Then, the CPU 5 uses the average characteristic change rate ΔS of the transmission path (2) to obtain correction values R3'1 to R3'n for the reference values R31 to R3n of the table 63 from the following equations.

R3' m=R3m (1-ΔS) - (31 Store (update) this in the table 64.

Similarly, the CPU 5 determines the average characteristic change rate ΔS of the transmission path ■.
Using, for the reference values R31 to R8n of table 68,
Correction values R8'1 to R3'n are obtained from equation (3) and stored (updated) in the table 69.

Hereafter, the transmission paths ■ and ■ are measured value tables 61.66
The reflection paths (1) and (2) are subjected to shading correction using the approximate correction values of tables 64 and 69.

In this way, by utilizing the fact that the ratio of reflected light and transmitted light is constant, the statistical value ΔS based on the value TN measured on the transmission path is applied to the initial data R3 when the device is completed, and the correction value R3 is ' can be obtained, and the shading correction value of the reflected light sensor can be updated without a medium.

tb) Description of other embodiments In addition to the embodiments described above, the present invention can be modified as follows.

■ Two light-emitting parts and two light-receiving parts, ■, ■, ■, ■
Although a total of four patterns have been obtained, it is also possible to use one light emitting part or one light receiving part and obtain two patterns, for example, ■ and ■.

(2) Although shading correction is performed by controlling the amount of light emitted from the light emitting section, it may also be performed by controlling the amplification degree of the light receiving section.

■ I am looking for the rate of change in characteristics, but the amount of change in characteristics ΔT−TO
-TN, calculate the average value ΔS, and R3' -R
It may also be 3-ΔS.

(2) Update of the correction value during operation may be performed periodically or at the initial time depending on the state of the error-prone special device.

(2) Also, although the rate of change is obtained based on the data at the time of completion of the device, the rate of change may also be obtained based on the data measured one or two times before.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, the following effects are achieved.

- Since shading correction information on the reflection side can be corrected without a medium, both transmission and reflection shading correction information can be corrected without operator intervention.

■ Since there is no operator intervention, correction can be made at an appropriate time depending on the equipment's convenience, and automatic correction is possible.

FIG. 3 is an explanatory diagram of the information table of FIG. 2, FIG. 4 is a processing flow diagram of an embodiment of the present invention, and FIG. 5 is an explanatory diagram of the prior art.

In the figure, 1a, 1b 2a, 2b tp light emitting part, one light receiving section; control unit, Detected medium.

Patent applicant: Fujitsu Limited Representative Patent Attorney Akira Yamatani

[Brief explanation of drawings]

Figure 1 is a diagram of the principle of the present invention. FIG. 2 is a configuration diagram for an embodiment of the present invention, (f3) Explanatory picture of Shubinghuan Street Figure 5

Claims (1)

[Claims] A light emitting section (1a) that irradiates light to a detected medium (dp), and a light receiving section (2a) that receives light from the detected medium (dp).
, 2b), and performs shading correction using the shading correction information of the transmitted light and the shading correction information of the reflected light, and the light receiving section (2a, 2b) detects the transmitted light and the reflected light from the detected medium (dp). In an optical line sensor having a control section (5) that obtains an output, the control section (5) controls the light emitting section (1a) in the absence of the detected medium (dp).
shading information of the transmitted light is measured by the shading information of the transmitted light and the light receiving part (2b), the characteristic change of the optical line sensor is calculated from the shading information of the measured transmitted light and the shading information of past transmitted light, and the shading correction information of the reflected light is calculated. A shading correction method for an optical line sensor, characterized in that the shading correction method for an optical line sensor is corrected using the characteristic change.