JP2779074B2 - Optical reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reading apparatus which performs reading scanning a plurality of times by a line sensor which receives light from a display optically recorded on a medium and converts the light into an accumulated charge amount. In particular, the present invention relates to an optical reading device improved so that the control of the light receiving sensitivity is optimized at an early stage.

[0002]

2. Description of the Related Art In an optical reading device called a touch type bar code scanner for reading a bar code attached to a bar code label or the like, a CCD sensor or a CMOS sensor is used.
A line sensor such as a sensor is used, and an analog signal whose level fluctuates when a bar of the bar code is scanned by scanning the bar code by the line sensor is obtained. This analog signal is binarized by a binarization circuit, and then supplied to a decoder to recognize a barcode.

FIG. 9 is a block diagram showing a basic structure of an example of a conventional touch type bar code scanner. Reference numeral 300 denotes a line sensor, and 301 denotes the above-mentioned binarization for binarizing an output signal of the line sensor 300. Circuit, 302 is a binarization circuit 3
01 is the above decoder for decoding the output signal of 01 and recognizing the bar code, 303 is a clock generator, 304
Is an m / n base counter.

In FIG. 1, a clock generator 303 generates a clock φ1 having a predetermined frequency. This clock φ1 is supplied to the line sensor 300, and m /
It is supplied to an n-ary counter 304. This m / n base counter 304 functions as a frequency divider, and assuming that the period of the clock φ1 is tφ, as shown in FIG.
This clock φ1 is provided for each cycle (that is, for the period of ntφ).
, A start pulse ST having a pulse width of m periods (that is, mtφ) is generated. Here, n and m are positive integers and n> m. This start pulse ST is also supplied to the line sensor 300.

The line sensor 300 has an array of photodiodes as light receiving elements arranged in a large number on a line and capacitors as power storage elements corresponding to the number of the photodiodes, and is supplied with a start pulse ST. In the pulse period, charge is accumulated in an amount corresponding to the amount of light received from a medium such as a label with a bar code by a photodiode. For example, when the line sensor 300 is a CMOS sensor, the clock φ1 is supplied. Each time the stored charge is read out from each capacitor. This allows
The line sensor 300 generates an analog signal BS corresponding to the bar code. That is, the start pulse ST sets the charge accumulation time in the line sensor 300, and the clock φ1
Is a drive pulse for sequentially reading out the accumulated electric charges.

By the way, assuming that the dividing ratio of the m / n-base counter 304 is constant, the pulse width of the start pulse ST is constant, and the charge accumulation time in the line sensor 300 is constant, the type of the bar-coded medium The amount of charge accumulated differs depending on the distance from the medium to the light receiving surface of the line sensor 300, and as a result, the amplitude of the analog signal BS output from the line sensor 300 varies.
On the other hand, the width of the bar of the bar code is not constant, and a plurality of different widths are defined. In the binarization circuit 301, the analog signal BS must be binarized so as to represent the width of the bar. For this reason, the threshold level is set so that the analog signal BS is binarized at the center level of the amplitude.

When such a line sensor 300 is used, there is a variation in the light receiving-charging characteristics within a single line sensor within a predetermined width, and there is also a variation between the line sensors, Since the illuminance distribution also varies, in order to set the light receiving sensitivity, a specific detection time must be set in an extremely limited environment. Therefore, even if there is no variation in light receiving to charging characteristics within one line sensor, if there is variation in the distance between the medium and the optical reading device or in the reflectance of the medium itself,
Since the amount of received light varies greatly, the amount of charge accumulated as a result differs. Then, if the storage charge amount to be changed in a certain detection time is saturated, the analog signal BS is also saturated, and the binarization circuit 301 is provided with a binarized circuit provided in the binarization circuit 301. Even with a general automatic threshold control circuit (ATC) that adjusts the threshold value depending on the amplitude of the analog signal BS that is the signal level, the threshold level cannot be set higher than the saturated analog signal BS. Therefore, even if the display code of the medium includes a black display, a binarized signal indicating a white state is output for the entire detection time. Similarly, if the accumulated charge amount has a large amount during a certain detection time and the number of things that should be changed becomes small, the amplitude of the analog signal BS becomes insufficient, and the binarization circuit 301
In the general automatic threshold control circuit of the binarization circuit 301, the threshold level cannot be set lower than a certain value with respect to the maximum value of the small analog signal BS due to the problem of detection sensitivity. Even in the state including the display, a binarized signal indicating a black state is output during the entire detection time.

As described above, when a fixed detection time is set between the elements of the line sensor 300, even if an automatic threshold value adjusting circuit is added to the binarizing circuit 301, the binarizing circuit 301
In the above, the binarized signal supplied to the decoder 302 is erroneously distinguished from the reflection and non-reflection of the detected bar code, which is the display code, in a reverse relationship. Even if the erroneous discrimination state of the binary signal is partial, the binary signal supplied at this time is not correctly decoded by the decoder 302, and the decoder 302 enters the error determination routine. I get judge the wrong length of bar and space.

Therefore, in the conventional touch bar code scanner, the charge accumulation time of the line sensor 300 is made variable. Hereinafter, the means for changing the charge accumulation time will be schematically described with reference to FIG.

In FIG. 1, N accumulation time setting circuits 3
_{05 1, 305 2, ......,} 305 N are provided, one of these by being selected by the switch 306, the charge accumulation time of the line sensor 300 is set. The decoder 302 recognizes the barcode by decoding the output signal of the binarization circuit 301. However, when the decoder 302 cannot recognize the barcode, a "decode error"
To control the switch 306. As a result, the switch 306 operates in a predetermined order, for example, the accumulation time setting circuit 30.
5 _1, 305 _2, when Te sequentially changing the charge accumulation time of the line sensor 300 selected in the order of ..., the decoder 3
02 searches for a charge accumulation time in which a bar code can be recognized. The next accumulation time setting circuit 305 _N will be accumulation time setting circuit 305 ₁ is selected, this selection is carried out in a ring shape.

In FIG. 9, in order to switch such a charge accumulation time, the frequency division ratio of the m / n base counter 304 may be sequentially changed. However, the division ratio here can be represented by m / n with the period of the start pulse ST in FIG. 10 being constant (that is, n = constant). Changing the division ratio changes m (Ie, changing the pulse width of the start pulse ST).

Next, a specific configuration of the above-described touch bar code scanner will be described with reference to FIGS.
In this figure, 1 is a signal latch circuit during reading, 2 is an illuminating section, 3 is an optical image forming section, 4 is a one-scan counter, 5 is a medium, 6 is a bar code, 7 is a start pulse generating circuit, 8
Is a pulse width setting circuit, 10 is a photoelectric converter, 11 and 12 are frequency divider circuits, 13 is an oscillation circuit, 14 is a binarization circuit, 15 is a scan count constant memory, 16 is a scan count counter, and 17 is a scan count comparison. , 18 is an edge detection circuit, 19 is a timer counter, 20 is a count value memory, 21 is a count value memory control unit, 211 is a margin judgment unit, 212 is a fast throw judgment unit, 213 is an address counter, 21
4 is an address decoder, 215 is a reset circuit, 22 is a bit image converter, 23 is a character code bit image memory, 24 is a stop code bit image memory, 25 is a bit image memory control unit, and 26 is a start stop determination unit. , 27 are character conversion units, 28
Is a character code coincidence comparator, 29 is an error processing circuit, 30 is a constant memory, 31 is a data coincidence counter, 32 is a data coincidence comparator, and 33 is an output data converter.

[0013] A bar code is such that characters such as letters and numbers are coded with a plurality of bars having different widths, so that character columns such as product prices and product names are represented in an array of bars. It is. A code representing a character is hereinafter referred to as a character code. The number of bars representing one character code, a thick bar,
Although the combination pattern of the thin bars differs depending on the bar code format, each format shows a margin (blank portion), a start code, and a stop code before and after a row of bars representing all character codes. Bar rows are provided.

In the following, for clarity of explanation, FIG.
2. The format of the barcode read by the barcode scanner shown in FIG. 13 is assumed to be Interleaved 2of5. This means that five black bars represent one character,
In addition, five white bars forming the interval between black bars represent one character. One bar code represents a plurality of character codes, and each character code represents one digit, and represents a plurality of character codes.

In this type of barcode display, a ground color portion of a medium having a predetermined width on the left side of the barcode display is a start margin, and a ground color portion of a medium having a predetermined width on the right side is a stop margin. The margin is used to determine that the barcode is displayed. The thin bar at the left end of the bar code display and the thin bar following it represent a start code, and the thin bar at the right end and the thick bar to the left of this represent a stop code. A character code for discriminating each display content is provided between the start code and the stop code by a combination of a predetermined number of thin bars or thick bars (black bars) and thin spaces or thick spaces (white bars). Is displayed. Here, assuming that the arrangement direction of the character codes (that is, the direction from the start code to the stop code) is the forward direction, the bar code is generally read in the forward direction, but in the reverse direction. In such a case, the start code is read as if the stop code was a start code and as if the start code was a stop code. Thus, the pattern of the stop code is different, so that the reading direction of the bar code can be determined.

In FIG. 12, an oscillation circuit 13 is always operating, and its output signal is divided by a frequency dividing circuit 11 to form a clock φ1 and a frequency dividing circuit 12 to form a clock φ2. Is done. The clock φ1 corresponds to the clock φ1 in FIG.
The clock φ 2 is supplied to the photoelectric conversion unit 10, the one-scan counter 4, and the start pulse generation circuit 7 corresponding to the m / n-ary counter 304 in FIG.

A read start signal S from a host device (not shown)
Is supplied, the reading signal latch circuit 1 is set and outputs a reading signal READ, which is supplied to the illuminating section 2 and the start pulse generating circuit 7. The illuminating section 2 has an LED as a light emitting element, and illuminates the LED according to the reading signal READ to illuminate the printing area of the barcode 6 on the medium 5. The light reflected from the printing area is applied to the light receiving surface of the line sensor, which is the photoelectric conversion unit 10, via the optical image forming unit 3, and the optical image forming unit 3 applies the bar code 6 to the light receiving surface of the line sensor. Is formed. Hereinafter, the photoelectric conversion unit 1
0 will be described as a line sensor.

The start pulse generating circuit 7 has the following four conditions: (1) the scanning end signal SED is supplied from the one-scan counter 4; and (2) the reading signal from the latch circuit 1 during reading.
(3) The pulse width setting is completed in the pulse width setting circuit 8 and the set value is sent. (4) The character conversion end signal CED is supplied from the character converter 27 (FIG. 13). When all of the above conditions are simultaneously satisfied, a start pulse ST is generated. Such a condition is hereinafter referred to as a pulse generation condition.

In the initial state, the one-scanning counter 4 sets the scanning end signal SED, the pulse width setting circuit 8 sets the initial value, and the character converter 27 (FIG. 13) sets the character conversion end signal CED. The start pulse generating circuit 7 satisfies the pulse generating condition when the reading signal READ is supplied from the reading signal latch circuit 1 and the start of the pulse width determined by the initial value of the pulse width setting circuit 8 is started. A pulse ST is generated. The start pulse ST is supplied to the one-scan counter 4 and the line sensor 10.

The line sensor 10 has a start pulse ST
, The image on the light receiving surface is changed by one every time the clock φ1 is supplied.
Reading is performed pixel by pixel, and the bar code 6 is scanned and read.
As a result, the line sensor 10 outputs an electric signal BS having different levels between the black bar and the white bar of the bar code 6. The one-scan counter 4 has a start pulse ST
As a result, the clock φ1 starts counting and the scan end signal SED is not output. When the clock φ1 for one scan of the line sensor 10 is counted, the scan end signal SED is output again. The scanning end signal SED is supplied to the start pulse generation circuit 7, the scanning number counter 16, the count value memory 20, the margin determination circuit 211, and the address counter 213.

The pulse width of the start pulse ST determines the charging time of each capacitor forming a pixel in the line sensor 10, and the line sensor 10 according to the charging time.
The magnitude of the level of the output signal is determined. The pulse width of the start pulse ST is determined by the value set by the pulse width setting circuit 8, and this value is determined by the count value NS of the scan number counter 16 for counting the scan end signal SED output from the one scan counter 4. It depends. Therefore,
The set value of the pulse width setting circuit 8 is changed every time the line sensor 10 scans, and accordingly, the pulse width of the start pulse ST changes every time the line sensor 10 scans.

When the scan end signal SED is again supplied from the one-scan counter 4 and the pulse generation condition is satisfied, the start pulse generation circuit 7 again generates a start pulse ST having a pulse width corresponding to the set value of the pulse width setting circuit 8. Then, the line sensor 10 starts scanning and the one-scan counter 4 starts counting. Thus, the line sensor 10
Scans the bar code 6 repeatedly.

The output signal BS of the line sensor 10 is shown in FIG.
After the level is binarized by the binarization circuit 14 corresponding to the binarization circuit 301, the edge detection circuit 18 detects the rising edge and the falling edge. The edge pulse EG output from the edge detection circuit 18 is supplied to a timer counter 19 and an address counter 213. The processing circuits after the edge detection circuit 18 constitute the decoder 302 in FIG.

The timer counter 19 counts the clock φ2 from the frequency dividing circuit 12 using the edge pulse EG as a reset signal. Accordingly, the count value N representing the width of each bar of the bar code 6 is output from the timer counter 19. The count value N is written to the count value memory 20 controlled by the count value memory control unit 21.

The count value memory control unit 21 includes a margin judgment unit 211, a first throw judgment unit 212, an address counter 213, an address decoder 214, and a reset circuit 215. Margin determination unit 2
Numeral 11 indicates the count value N of the timer counter 19 with respect to a blank portion (start margin, stop margin) provided before the first bar and after the last bar of the bar code 6, and the count value of the blank portion and the bar code portion. Based on the ratio, the start and end of the barcode are detected, and a start signal MST and an end signal MED are generated. Also, start margin,
When the stop margin is insufficient, a margin error signal MER is output and supplied to the reset circuit 215. 1
When the scan end signal SED is supplied from the scan counter 4, the margin determination circuit 211 does not operate. The first throw determination unit 212 detects the magnitude of the count value N output from the timer counter 19, and determines whether the interval between the edge pulses EG from the edge detection circuit 18 is too small,
When it is too wide, a fast throw error signal is output and supplied to the reset circuit 215. When the bar code 6 is printed on the medium 5 and the bar is narrowed or spread due to bleeding, scratching, dust adhesion, or the like, the fast throw determination unit 212 outputs a fast slow error signal. Output. The reset count 215 generates a reset signal when the margin error signal MER is supplied from the margin determination section 211 or when the first throw error signal is supplied from the first throw determination section 212, and counts with the address counter 213. To the value memory 20.

When the line sensor 10 starts scanning without the supply of the scan end signal SED from the one-scan counter 4, the address counter 213 sets the margin judgment section 21
The start signal MST is supplied from 1 and the edge signal EG from the edge detection circuit 18 starts counting from the initial value. The count value output from the address counter 213 is decoded by the address decoder 214 and supplied to the count value memory 20 as an address signal ADR. When the scan end signal SED is no longer supplied from the one-scan counter 4, the count value memory 20 enters the write mode, and the count value N output from the timer counter 19 is set to the address specified by the address signal ADR of the count value memory 20. Written sequentially.

When the count values N for all the bars of the bar code 6 are written to the count value memory 20 and the end signal MED is output from the margin determination unit 211, the address counter 213 stops counting and the initial value is set. Is done. Next, after one scan of the line sensor 10 is completed, 1
When the scan counter 4 outputs the scan end signal SED, the count value memory 20 enters the read mode, and the address counter 213 outputs a count value sequentially incremented by one from the initial value by the internal clock. This count value becomes the address signal ADR of the count value memory 20 by the address decoder 214. Therefore, the written count value N is read from the count value memory 20.
Are read out in the order in which they were written.

When the reset circuit 215 outputs a reset signal, the address counter 213 is reset to an initial value and the count value memory 20 is cleared. The margin judging section 211 continues to output the margin error signal MER until the next margin judgment, and the first throw judging section 212 outputs the first slow error signal until the next scanning end signal SED is supplied from the one-scan counter 4. to continue.

The count value N output from the count value memory 20 is supplied to a bit image converter 22, where it is compared with a preset threshold value and converted into a bit image BI representing the type of bar.

Next, FIG. 13 will be described. The bit image BI from the bit image conversion unit 22 is supplied to a character code bit image memory 23, a stop code bit image memory 24 and a bit image memory control unit 25. Bit image memory controller 2
Reference numeral 5 denotes whether the bit image BI forms a character code (character code bit image) or a stop image forms a stop code (stop code bit image) by determining the output order of the bit image BI. And bit image B
When I is a character code bit image,
The bit image BI is divided into five pieces each to form 1-byte data, and these data are sequentially written into the character code bit image memory 23, and the bit image BI is written.
Is a stop code bit image, this is written to the stop code bit image memory 24. In the case of the interleaved 2of5, the bit images for the black bar and the white bar are divided, and 1-byte data is formed for each, and written to the character code bit image memory 23. When the writing in the character code bit image memory 23 and the stop code bit image memory 24 is completed, the bit image memory control unit 25 sequentially reads the one-byte data CCD from the character code bit image memory 23 and reads the character CCD. The stop code bit image SCD is read from the stop code bit image memory 24 and sent to the start stop determination unit 26.

In the start stop judging section 26,
For the correct stop code used for barcodes,
Bit patterns (hereinafter referred to as registered stop code patterns) of two types of bit images obtained when the image is correctly read in the forward and reverse directions are registered in the ROM.
A bit pattern of the data SCD with one bit image (hereinafter, referred to as a detected stop code pattern) is compared with a registered stop code pattern, and it is determined which registered stop code pattern matches. When there is a registered stop code pattern that matches the detected stop code pattern, the reading direction of the bar code 6 can also be determined based on the registered stop code pattern, and data (stop code data) corresponding to the matched registered stop code pattern can be determined.
The SSC is supplied to the output data converter 33, and the conversion direction instruction signal CDD is sent to the character converter 27.

When there is no registered stop code pattern matching the detected stop code pattern SCD, the start stop judging section 26 outputs an error signal ERR 1 and supplies it to the error processing circuit 29.

In the character conversion section 27, a 1-byte bit pattern (hereinafter referred to as a registered character) containing a bit image obtained when the character code is correctly read in the forward direction is applied to all the character codes used for the bar code. Code pattern) is registered in the ROM,
The 1-byte data CCD bit pattern from the character code bit image memory 23 (hereinafter referred to as a detected character code pattern) is compared with the registered character code patterns to determine which registered character code pattern matches. You. In this case, when the bar code 6 is read in the reverse direction, the conversion direction instruction signal CDD from the start stop determination unit 26 outputs
The detected character code pattern CCD is flipped back and forth and compared with the registered character code pattern.

When the detected character code pattern CCD matches any of the registered character code patterns,
The character conversion unit 27 outputs character data CD corresponding to the registered character code pattern that matches, and sends it to the character code match comparator 28 and the output data conversion unit 33. If the detected character code pattern CCD does not match any of the registered character code patterns, the character converter 27 generates an error signal ERR2 and sends it to the error processing circuit 29. When all of the detected character code patterns CCD for one scan of the bar code 6 are converted into character data CD, the character conversion unit 27 generates a character conversion end signal CED to generate a character conversion end signal CED.
2 to the start pulse generating circuit 7. As a result, the start pulse generating circuit 7
T is generated, and the line sensor 10 (FIG. 12) scans the bar code 6 next.

The character code coincidence comparator 28 outputs the character data CD for one scan from the character converter 27.
Is compared with the character data CD supplied from the character converter 27 in the next scan.
When all character data match, a match pulse is output and supplied to the data match counter 31. The data coincidence counter 31 counts the coincidence pulse, and the count value is compared with the coincidence number set value stored in the constant memory 30 by the data coincidence number comparator 32. When the count value of the data match number counter 31 becomes equal to or greater than the set value of the number of match times, the data match number comparator 32 generates a read completion signal REND1 and outputs
Send to Character converter 27 for previous scan and current scan
If even one of the character data CDs from
The character code match comparator 28 outputs the error signal ERR3.
Is output to the error processing circuit 29, and the data match counter 31 is cleared.

The output data conversion unit 33 captures the character data CD from the character conversion unit 27 and the stop code data SSC from the start stop determination unit 26 for each scan of the bar code 6 and holds the latest data. When the read completion signal REND1 is supplied from the data match number comparator 32, the held character data CD and stop code data SSC are converted into a predetermined format and sent to a host device (not shown). . At the same time, a display instruction signal DIS for displaying the end of reading is sent to a display device (not shown) such as a lamp or a buzzer, and a reset signal RST is generated to initialize itself. The reset signal RST is supplied to the reading signal latch circuit 1 (FIG. 12) and the like, and resets them. When the reading signal latch circuit 1 is reset by the reset signal RST, it does not output the reading signal READ, and stops reading the bar code 6. The illumination unit 2 is also turned off.

In this manner, when the character data from the preceding and following scans continuously match the number of times (for example, twice) according to the set number of times in the constant memory 30, the barcode 6 is read correctly and the reading ends. If the numbers do not match continuously, the reading of the bar code 6 is repeated. However, even if the reading is repeated a certain number of times, the reading completion signal REN from the data matching number comparator 32 is returned.
If D1 is not output, further reading of the barcode 6 is prohibited.

That is, in FIG. 12, the scanning counter 16 counts up by one each time the one-scan counter 4 outputs the scanning end signal SED. The count value of the number-of-scans counter 16 indicates the number of scans of the line sensor 10.
It is compared with a constant set to 5. When the count value of the number-of-scans counter 16 becomes equal to or greater than this constant, the number-of-scans comparator 17 outputs a read end signal REND2, and FIG.
To the output data conversion unit 33.

Therefore, the output data converter 33 outputs the reset signal RST to initialize itself without sending the character data and the stop code data to the host device. As a result, the reading of the barcode 6 is stopped assuming that the reading of the barcode 6 has failed. Also,
A display instruction signal DIS indicating that reading is impossible is sent to the display device.

The error processing circuit 29 outputs the error signal ERR
Even if any one of ERR1, ERR2 and ERR3 is supplied, a character conversion reset signal CERT is output, and the count value memory control unit 21 and the bit image conversion unit 2 shown in FIG.
2 and character code bit image memory 2 of FIG.
3. Stop code bit image memory 24, bit image memory control unit 25, start stop determination unit 2
6. Initialize the character conversion unit 27 and the like. Thus, the character conversion unit 27 outputs a character conversion end signal CED.

As described above, the line sensor 10 reads and scans the bar code 6 a plurality of times, and when the character codes match continuously the number of times equal to the set value of the number of matches in the constant memory 30, the bar code 6 is correctly read. The reading operation is completed by sending this character code to the host device. During this time, the pulse width set by the pulse width setting circuit 8 is changed for each scan of the line sensor 10, and the The pulse width of the start pulse ST output from the start pulse generation circuit 7 changes.

FIG. 14 is a block diagram showing an example of the pulse width setting circuit 8 in FIG. 12. Reference numerals 81 and 82 denote constant memories, 83 denotes a multiplier, 84 denotes an adder, and 85 denotes a set value memory.

In the figure, a value (reference value) for determining a pulse width (reference pulse width) to be set first of the start pulse ST generated by the start pulse generation circuit 7 (FIG. 12) is stored in a constant memory 81. And a value (1/16 value) for a pulse width that is 1/16 times the reference pulse width is stored in the constant memory 82.

When power is supplied to the bar code scanner or when the reset signal R is output from the output data converter 33 shown in FIG.
When ST is output, the reference value of the constant memory 81 is loaded into the set value memory 85, which is read and supplied to the start pulse generating circuit 7 and the adder 84 in FIG. Therefore, the pulse width of the start pulse ST output first from the start pulse generation circuit 7 is in accordance with the reference value.

When the scanning of the line sensor 10 (FIG. 12) is completed, the one-scan counter 4 (FIG. 12) outputs the scanning end signal SED.
Is output, the multiplier 83 multiplies the 1/16 value stored in the constant memory 82 by the count value Ns of the scan number counter 16 (FIG. 12) at the timing of the previous edge of the scan end signal SED. , Adder 84 adds the output value of multiplier 83 and the set value read from set value memory 85. In the set value memory 85, the set value stored there is rewritten with the output value of the adder 84 slightly later than the previous edge of the scanning end signal SED, and this is immediately read out and the start pulse generating circuit 7 ( 12) and the adder 84.

For this reason, the set value read out from the set value memory 85 is initially equal to the reference value stored in the constant memory 81, but every time the line sensor 10 (FIG. 12) completes scanning, this reference value is set. It increases by 1/16 times the value. Accordingly, the start pulse generation circuit 7 (FIG. 12) outputs the start pulse ST having the first reference pulse width.
However, every time scanning of the line sensor 10 is repeated, the pulse width of the start pulse ST becomes 1/1 of the reference pulse width.
It will be longer by 6 times the width.

Next, the line sensor 10 in FIG. 12 will be described. FIG. 15 is a configuration diagram of the line sensor 10, in which 101 is a pixel portion, 102 is a read shift register, 103 is a sweep shift register, 104 is a sample and hold circuit, 104a is a preamplifier, 104b is a sample switch, and 104c is a sample switch. capacitor, 104d are buffer amplifier, 105 is 8 frequency divider, latch sweep is 106, 107 read latch, D ₁ -Dn photodiode by a PN _{junction, S 11 ~S 1 n, S} 21
〜S ₂ n are analog switches formed by MOSFETs. FIG. 16 is a diagram showing a timing relationship between signals of the respective units in FIG.

In FIGS. 15 and 16, one pixel is constituted by a set of one photodiode Di (where i is 1, 2,..., N) and a pair of analog switches S ₁ i and S ₂ i. In the pixel unit 101, n pixels are arranged in one column. The analog switch S ₁ i is controlled on and off by a sweep shift register 103, and the analog switch S ₂ i is controlled on and off by a read shift register 102.

Clock φ from frequency dividing circuit 11 (FIG. 12)
1 is divided by the divide-by-8 circuit 105, and the duty ratio is 1/2.
Sampling black poke phi _SP of Shifutokurotsuku phi _SH and duty ratio 1/16 is formed. Sample Sui Tutsi 104b of the sample-and-hold circuit 104 is turned on pulse duration of the sampling black poke phi _SP. The shift clock φ _SH is supplied to the read shift register 102, the sweep shift register 103, and the read latch circuit 107.

The start pulse ST supplied from the start pulse generation circuit 7 (FIG. 12) is an "L" (low level) pulse, and the read latch circuit 107 is set at the rising edge (late edge) of the start pulse ST. It is reset at the rising edge of the shift clock φ _SH immediately after the lever. The output P _RD of the read latch circuit 107 is an “L” pulse having a pulse width from the edge after the start pulse ST to the shift clock φ _SH immediately after the start pulse ST. This pulse P _RD is supplied to the read shift register 102. The sweep latch circuit 106 is set at the falling edge (previous edge) of the start pulse ST, and is reset at the rising edge (back edge) of the output pulse P _RD of the read latch circuit 107. Therefore, the output P _EX of the sweep latch circuit 106 is an “L” pulse from the edge before the start pulse ST to the edge after the output pulse P _RD of the read latch circuit 107.

When the read latch circuit 107 and the sweep latch circuit 106 are in a reset state and the "L" pulses P _RD and P _EX are not output, all outputs of the read shift register 102 and the sweep shift register 103 are output. "H" is a (high level), the analog Sui for reading Tutsi S ₂ i (where, i = 1 to n) is turned off, the analog switch S ₁ i for sweeping is oN. FIG. 17 shows such a state. As a result, a constant bias voltage + V is applied to the cathode side of each photodiode Di via the analog switch S ₁ i, and an amount of charge determined by the capacitance and the bias voltage + V is accumulated in each photodiode Di. . Such a state is a discharge state.

[0052] start pulse ST is supplied, when the previous latch 106 sweep at the timing of edge outputs a pulse P _EX of "L", sweeping shift register 103
In this case, the pulse P _EX is sequentially transferred by the shift clock φ _SH , whereby the analog switch S ₁₁ ,
S _12, ......, S ₁ n go off with a delay of one cycle of sequentially Shifutokurotsuku φ _SH. Each analog switch S ₁ i
There is the shortest period among the integral multiple of the period of output pulses P _EX of the pulse width or more and Shifutokurotsuku phi _SH of latch 106 periods sweep to off. Thus, the state is a pixel charge storage state shown in FIG. 18, analog switch S ₁ i is turned off when the analog switch S ₂ i is off, the photodiode Di, the intensity of light incident thereon A photocurrent of a magnitude corresponding to the current flows, and the electric charge of the capacitor at the PN junction is discharged.

When an "L" pulse P _RD is output from the read latch circuit 107 at an edge after the start pulse ST, the read shift register 102 outputs the pulse P _RD.
There is sequentially shifted Te Shifutokurotsuku phi _SH Niyotsu, analog switch S _21, S _22, ......, it is turned by one cycle of Shifutokurotsuku phi _SH in the order of S ₂ n. FIG. 19 shows such a state at the i-th pixel. This state is a reading state, in which the charge stored in the photodiode Di is read out via the analog switch S ₂ i, and the sample-and-hold circuit 1
04. The period during which the analog switch S ₂ i is on is one cycle of the last shift clock φ _SH of the off period of the analog switch S ₁ i.
₁ i, S ₂ i returns to the state sweep 17 off at the same time. Therefore, the amount of electric charge read out from the photodiode Di is based on the remaining amount of electric charge of the capacitor discharged in the state of FIG. 18, and is based on the light receiving intensity.

Thus, the photodiodes D ₁ ,
The pixel charges are read out at the timing of the shift clock φ _{SH in} the order of D ₂ ,.
Supplied to In the pixel where the reading has been completed, the pixel is in the sweeping state shown in FIG. 17, the bias voltage + V is applied to the cathode of the photodiode Di, and charging is performed again.

Signal B based on charges read from each pixel
S 'is amplified by the preamplifier 104a in the sample and hold circuit 104, and then the sampling clock .phi.
_{The signal} is sampled and held by the sample switch 104b driven by _SP and the capacitor 104c, and the output signal BS of the line sensor 10 via the buffer amplifier 104d.
Becomes

As described above, in the line sensor 10, the pixel charge accumulation time in each pixel is determined by the pulse width of the output pulse P _EX of the sweeping latch circuit 106,
The charge amount varies depending on the pulse width of the start pulse ST, and the amount of charge read varies depending on the pixel charge accumulation time.
Therefore, by changing the pulse width of the start pulse ST, the magnitude of the output signal BS of the line sensor 10 can be changed.

By the way, if the start pulse ST is input before the reading is completed for all the pixels, the reading is performed simultaneously in two different pixels, and the normal reading is not performed. For this reason, in FIG.
A scanning counter 4 is provided, which detects that the reading of all pixels is completed by the line sensor 10, and based on this detection, the start pulse generating circuit 7 generates the start pulse ST. I have.

[0058]

By the way, in the above-mentioned conventional bar code scanner, the pulse width of the start pulse ST is sequentially increased every time the line sensor 10 scans, and the pixel charge accumulation time in the line sensor 10 is sequentially increased. The increasing operation is repeated. According to this, the following problem occurs.

That is, after the start, the pulse width of the start pulse ST gradually increases from the reference pulse width, and becomes a pulse width that allows the bar code to be read satisfactorily. If the bar code reading error happens to occur when the start pulse ST reaches the width and decoding of the output signal BS of the line sensor 10 becomes impossible, the pulse width of the start pulse ST is increased as it is. It is necessary to wait until the start pulse ST has a pulse width such that a good bar code can be read again. That is, the reading time of the barcode becomes longer, which causes a problem in operability.

To solve this, the line sensor 1
The time required for one scan of 0 may be shortened, but for this purpose, the frequency of the output clock of the oscillation circuit 13 must be increased. However, when the clock frequency is increased, the power consumption in the oscillation circuit 13 increases, and this is a particular problem in a portable touch-type barcode scanner because a battery is built in and used as a power source. In addition, there is a problem in terms of measures against noise and sensitivity of the line sensor.

An object of the present invention is to solve such a problem and to increase the driving clock frequency of the line sensor without increasing the frequency.
An object of the present invention is to provide an optical reading device that can quickly set an appropriate pixel charge accumulation time in a line sensor.

[0062]

In order to achieve the above object, the present invention provides a level detecting means for detecting a level of an output level of a line sensor, and a pulse of a start pulse according to a detection output of the level detecting means. Pulse width setting means for increasing or decreasing the width is provided, and the amount of increase and decrease of the pulse width of the start pulse is made different.

[0063]

The output level of the line sensor is detected by the level detecting means regardless of whether the output signal of the line sensor can be decoded or not, and the start pulse is set to a pulse width corresponding to the detection result. Is done. For this reason, once the output level of the line sensor reaches an appropriate level for binarization, the output level is maintained at an appropriate level even if decoding is impossible.

Even if the output level of the line sensor deviates from the proper level at the time of starting, the output level greatly changes and approaches the proper level by the level detecting means and the pulse width setting means, and the proper level is obtained. As it approaches the level, it changes slightly and is set near the appropriate level.

[0065]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are block diagrams showing an embodiment of an optical reading apparatus according to the present invention, wherein 8 'is a pulse width setting circuit,
Reference numeral 9 denotes a level detection circuit, and portions corresponding to those in FIGS. 12 and 13 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1, the output signal BS of the line sensor 10 is also supplied to the level detection circuit 9. In this level detection circuit 9, the output signal B of the line sensor 10
A reference level V _{0, which} is the center of a level range in which S can be surely binarized by the binarization circuit 14, is set. The output signal BS of the line sensor 10 is envelope-detected, and the envelope level and the reference level V ₀ are detected. As a result, the detection signal LS becomes “L” when envelope level ≦ V ₀ and “H” when envelope level> V _0.
Is output. The detection signal LS and the margin determination unit 21
The start signal MST generated in step 1 is a pulse width setting circuit 8 '
Supplied to

The pulse width setting circuit 8 'determines the pulse width of the start pulse ST generated by the start pulse generation circuit 7, and is set in the level detection circuit 9 when the optical reading device is in the initial state. When an initial value corresponding to the reference level is read, that is, when the bar code 6 that is ideally designed is read, the envelope level of the output signal BS of the line sensor 10 is changed to the reference level V _0.
The pulse width of the start pulse ST is determined so as to coincide with the following. The initial value for generating the pulse width is set in the pulse width setting circuit 8 ', and is sent to the start pulse generation circuit 7 as the pulse width setting value _NST. . Therefore, the pulse width of the start pulse ST output first from the start pulse generation circuit 7 corresponds to this initial value.

The bar code 6 is read by the line sensor 10, and the envelope level of the output signal BS is compared with the reference level V ₀ by the level detection circuit 9, but “L” is detected when the envelope level ≦ V _0. Signal Ls
Is output from the level detection circuit 9, the pulse width setting circuit 8 ′ outputs the start signal MST from the margin determination unit 211.
In timing heretofore outputs a value greater than the value that is set as the pulse width setting value N _ST, increasing the pulse width of the next start pulse ST. On the other hand, when the detection signal Ls of “H” is output from the level detection circuit 9 when the envelope level is greater than V ₀ , the pulse width setting circuit 8 ′ similarly sets the pulse width setting value N _ST to be higher than before. And the pulse width of the start pulse ST is reduced.

[0069] Thus, the envelope level of the output signal BS of the line sensor 10 when the upper and lower with respect to the reference level V ₀ which level detection circuit 9, the pulse width setting circuit 8 ', the pulse width of the start pulse ST is increased or decreased . As a result, the envelope level of the output signal BS of the line sensor 10 fluctuates in the vicinity of the reference level V ₀ , and the output signal BS is surely binarized by the binarization circuit 14. The increment and decrement of the pulse width of the start pulse ST due to the change of the pulse width setting value N _ST of the setting circuit 8 ′ are made different. This is for the following reason.

Even if the above initial value is set in the pulse width setting circuit 8 ′ in the initial state of the optical reading apparatus, the line sensor 10 may not be used due to the contrast of the bar code 6 with respect to the medium 5 and the amount of light irradiated by the illumination unit 2. Is the reference level V of the level detection circuit 9 of the output signal BS.
_It may be significantly different from ₀ . In such a case, the pulse width setting value N _ST output by the pulse width setting circuit 8 ′ changes sequentially each time the line sensor 10 scans the bar code 6, but the envelope level reaches near the reference level V _0. in order to shorten the time to, it is better to increase the amount of change in the pulse width setting value N _ST of this case. Then, when the envelope level jumps over the reference level V ₀ ,
Although the envelope level changes toward the reference level V ₀ , the envelope level does not largely deviate from the reference level V ₀ by reducing the amount of change. Again envelope level Te cowpea thereto exceeds the reference level V _0, again exceeds the reference level V ₀ envelope level varies greatly, but also the reference level V
Come back towards ₀ . In this way, from the initial state, the output signal BS of the line sensor 10 quickly and surely reaches a level that can be binarized, and thereafter this state is maintained.

Note that the portion of FIG. 2 is the same as the portion shown in FIG. 13 of the related art, and a description thereof will be omitted.

FIG. 3 shows a change in the envelope level due to the above operation. BS (0) represents the envelope level in the initial state (first bar code scanning of the line sensor 10). In addition, the amount of increase in the envelope level is twice the amount of decrease. In this case,
When the envelope level changes from BS (0) to BS (1) and changes to BS (2), the envelope level becomes larger than the reference level V ₀ . Therefore, the envelope level decreases to BS (3), and then decreases to BS (4) when the reference level V _0.
Smaller than. Because of this, the envelope level again increases to BS (5). Hereinafter, the line sensor 10 is this operation as long as the repeated scanning and reading of the bar code 6 is repeated, the envelope level of the output signal BS of the line sensor 10 is in the vicinity of the reference level V _0.

As described above, in this embodiment, while detecting the output level of the line sensor 10 and judging whether or not the output level is good for binarization, the licensor 1
Since the output level of 0 is adjusted, even if decoding happens to be impossible in a good binarization processing state, this state is maintained as it is and decoding is performed immediately. In addition, the time from the initial state to the time when the binarization processing is surely performed can be shortened. Therefore, the bar code can be read quickly without increasing the frequency of the drive clock as in the above-described prior art, thereby improving operability and preventing an increase in power consumption.

FIG. 4 shows a pulse width setting circuit 8 'in FIG.
14 is a block diagram showing one specific example, in which reference numerals 86 and 87 denote constant memories, reference numeral 88 denotes a switch, reference numeral 89 denotes a control circuit, and portions corresponding to those in FIG.

In the figure, a constant memory 81 stores the above initial value, and a constant memory 86 stores a value which is 倍 times the initial value (hereinafter referred to as １ ／ value) in the constant memory. 87 has a value of -1/16 times the initial value (hereinafter,-
1/16 values) are stored. Control circuit 8
Reference numeral 9 denotes a start signal MS from the margin determination unit 211 (FIG. 1) according to the detection signal Ls from the level detection circuit 9 (FIG. 1).
It operates at the timing of T and controls the switch 88 to set the 1/8 value of the constant memory 86 or -1 /／ of the constant memory 87.
The 16 values are supplied to the adder 84. The adder 84 adds this to the pulse width set value N _ST from the set value memory 85, and
The pulse width setting value N _ST is updated by writing to the setting value memory 85.

In the initial state, the initial value of the constant memory 81 is written to the set value memory 85, and this initial value is used as the pulse width set value N _{ST by the} adder 84 and the start pulse generating circuit 7.
(FIG. 1).

When the detection signal Ls is "L", the control circuit 89 selects the 1/8 value of the constant memory 86 at the timing of the start signal MST. N _ST and add it to the set value memory 85, and set the pulse width set value N _ST to the initial value of 1
/ 8 times larger. When the detection signal Ls is "H", in the same manner, switch 88 selects the -1/16 value constant memory 87, adder 84 set value memory 85 are added thereto and the pulse width setting value N _ST Write to. As a result, the pulse width setting value N _ST is reduced by a value that is 1/16 times the initial value.

In the embodiment described above, the level detection circuit 9
Is provided with a reference level V ₀ to determine the output level of the line sensor 10.
It is also possible to set a level range that can be reliably binarized, and thereby determine the output level of the line sensor 10. Hereinafter, an embodiment for this will be described.

FIG. 5 shows an example of such an embodiment, wherein 7 'and 8 "are counters, 9' is an amplitude comparator, and 34 '
Is a decoder composed of a processing circuit after the edge detection circuit 18 in FIGS. 1 and 2, and 35 is a decoder.

In FIG. 5, an amplitude comparator 9 'corresponds to the level detection circuit 9 of FIG. 1, and includes a counter 8 "and a counter 7'.
Respectively correspond to the pulse width setting circuit 8 'and the start pulse generation circuit 7 in FIG.

The output signal BS of the line sensor 10 is binarized by the binarization circuit 14 and supplied to the decoder 34, and is also supplied to the amplitude comparator 9 'and binarized by the binarization circuit 14. When the “H” pulse is output, the reference values V _H and V _L (where V
_H > V _L ). These reference values V _H and V _L determine an appropriate amplitude range of the output signal BS which can decode the output signal of the line sensor 10 well.
When _VH >BS> _VL , the amplitude of the signal BS is appropriate. The threshold value V _TH of the _binarization circuit 14 satisfies V _TH < _VL .

The amplitude comparator 9 'outputs at least the output of the line sensor 10 when the signal BS has a small amplitude and no "H" output pulse is output from the binarization circuit 14, or at the timing of this "H" pulse. When the signal BS has a portion satisfying V _L ≧ BS, the up signal UP is output, the count value of the counter 8 ″ is multiplied by K ₁ (> 1), and the signal BS has a large amplitude and the binarization circuit 14 The output signal BS of the line sensor 10 at the timing of the "H" output pulse
When there is a portion where ≧ V _H , the down signal DOWN
Is output, and the count value of the counter 8 ″ is multiplied by 1 / K ₂ (however, K ₂ > 1). When V _H >BS> _VL , no signal is output, and the same count value is output to the counter 8 ″. Hold. These output signals UP, DO of the amplitude comparator 9 '
WN is cleared by the start pulse ST.

In the counter 7 ', the count value of the counter 8 "is preset, and the clock φ is calculated from the preset value.
Count one. This count value is supplied to the decoder 35. The decoder 35 outputs a signal of "L" for a period when the count value of the counter 7 'is from the preset value to the first specified value, and outputs an "H" signal when the count value exceeds the first specified value. This “L” output from the decoder 35
Is a start pulse ST. At the rising edge (late edge) of the start pulse ST, the counter 7 'loads the count value of the counter 8 "as a preset value and counts the clock φ1 to the second specified value. When the clock φ1 counts up to the second specified value, the clock φ1 is restored from the preset value. Every time the counter 7 'starts counting the clock φ1 from the preset value, a start pulse ST is output from the decoder 35, and the pulse width of the start pulse ST is set at the edge timing after the start pulse ST generated last time. This is in accordance with the count value of the counter 8 "preset in the counter 7 '.

Here, the count value of the clock φ1 from the preset value of the counter 7 ′ to the first prescribed value is m, the count value of the clock φ1 from the preset value to the second prescribed value is n, and the clock φ1 is Is T.phi., The pulse width of the start pulse ST is m.T.phi., And the period is n.T.phi., Both of which differ depending on the preset value of the counter 7 '. However, (nm) is constant, which corresponds to the number of pixels of the line sensor 10.

[0085] Now, the counter 7 'shall apply in up-counter, and the Purisetsuto value and negative value, the when the first specified value to zero, when the Purisetsuto value has decreased to ₁ × K is the start pulse ST The pulse width becomes K ₁ times,
When the preset value becomes 1 / K ₂ times, the pulse width of the start pulse ST also becomes 1 / K ₂ times.

In the initial state, the initial value is stored in the counter 8 ", and the initial value is preset in the counter 7 '. Thus, the decoder 35 starts the reference pulse width according to the initial value. A pulse ST is output, and thereafter, each time the line sensor 10 scans, the counter 8 ″
And the pulse width of the start pulse ST increases or decreases.

Here, it is assumed that K ₁ > K ₂ . Counter 8 "
Assuming that the initial value to be set to the minimum pulse width of the start pulse ST, in the first scan of the line sensor 10, the amplitude comparator 9 'outputs the up signal UP,
The count value of the counter 8 "to ₁ times K. Then, BS
> Successively ₁ times K the count value until a V _L. In this case, as the count value increases, the change amount of the count value, that is, the change amount of the pulse width of the start pulse ST increases sequentially. The count value of the counter 8 "is set to K
₁ multiplied by the result, not a V _H> BS> V _L, direct BS ≧ V
_H , the amplitude comparator 9 'outputs the down signal DO.
WN is output and the count value of the counter 8 ″ is multiplied by 1 / K _{2. In} this case, the count value obtained by multiplying by 1 / K ₂ is larger than the original count value by K ₁ immediately before. For example, the count value of the counter 8 "is now N
(0), and when this is ₁ × K, the count value K ₁ ·
N (0). This count value K ₁ · N (0) is calculated as 1 /
When K ₂ times, K ₁ / K ₂ > 1, then K ₁ · N (0) × 1 / K ₂ > N (0). That is, as a result of sequentially increasing the pulse width of the start pulse ST, if the amplitude of the output signal BS of the line sensor 10 exceeds the proper amplitude range defined by the amplitude comparator 9 ', this pulse width becomes the last increase amount. Is reduced by a smaller amount. From this, the pulse width of the start pulse ST quickly enters an appropriate range.

FIG. 6 shows a change in the preset value of the counter 9 '. The initial value N (0) is 2, and the range of the output signal BS of the line sensor 10 is determined by the reference levels _{VL to VH.} Within the preset value range of 4 to 5
K ₁ = 3 and K ₂ = 2. In this case,
N (1) = 6, N (2) = 3, N (2) = 3, N (3)
= 9, N (4) = 4.5.

FIG. 7 shows an embodiment in which FIG. 5 is modified. Only the down signal DOWN is outputted from the amplitude comparator 9 ', and the up signal UP is formed from the decode error signal of the decoder 34. It was made.
That is, when the level of the output signal BS of the line sensor 10 is low, the output signal of the amplitude comparator 9 'is "L" and the down signal DOWN is not output. The output signal of “L” becomes “H” by the inverter 36 and is output to the AND gate 37. At this time, the level of the output signal BS of the line sensor 10 is too small,
There when you disable decode the output of the binarizing circuit 14, the decoder 34 outputs the decoded error signal D _ER of "H" to the AND gate 37. Thereby, the AND gate 37
Outputs an "H" signal, which is supplied to the counter 8 "as an up signal UP.

As shown in FIG. 8, the amplitude comparator 9 '
"Is supplied to the counter 8" counter 8 only up-signal UP only is set the reference level V _L is the down signal DOWN to the as 7, the decode error signal D _ER decoder 34 outputs It may be formed.

[0091] Note that the decoding error signal D _ER in FIG. 7, FIG. 8, or the like can be used Kiyarakuta conversion reset signal CERT output by the error processing circuit 29 in FIG. 2.

The numerical values described in the above embodiments are merely examples, and the present invention is not limited by these numerical values.

[0093]

According to the present invention, the pulse width control signal is set so that the variable amount of the pulse width is different between the decrease amount and the increase amount based on the magnitude judgment of the detection level judging means, and the accumulation time is reduced. The sensitivity is adjusted by controlling, so that the time required to obtain a decodable binary signal does not become long, and the time until decoding succeeds becomes short, so that the operability is remarkably improved and the driving clock frequency is increased. Since there is no need to perform the above operation, it is possible to provide a low power consumption type and low cost optical reader.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a part of a first embodiment of an optical reading apparatus according to the present invention.

FIG. 2 is a block diagram showing the remaining portion of the first embodiment of the optical reading device according to the present invention.

FIG. 3 is a diagram showing a change in an output level of a line sensor in FIG. 1;

FIG. 4 is a block diagram showing a specific example of a pulse width setting circuit in FIG. 1;

FIG. 5 is a block diagram showing a main part of a second embodiment of the optical reading apparatus according to the present invention.

FIG. 6 is a diagram showing a change in a preset value of a counter in FIG. 5;

FIG. 7 is a block diagram showing a main part of a third embodiment of the optical reading apparatus according to the present invention.

FIG. 8 is a block diagram showing a main part of a fourth embodiment of the optical reading apparatus according to the present invention.

FIG. 9 is a block diagram showing a main part of an example of a conventional optical reading apparatus.

FIG. 10 is a timing chart showing a relationship between a clock and a start pulse in FIG. 9;

FIG. 11 is a block diagram showing a main part of another example of the conventional optical reading apparatus.

FIG. 12 is a block diagram specifically showing a part of the optical reading device shown in FIG. 11;

FIG. 13 is a block diagram specifically showing another portion of the optical reading apparatus shown in FIG. 11;

14 is a block diagram showing an example of a pulse width setting circuit in FIG.

FIG. 15 is a diagram illustrating a configuration of a line sensor in the optical reading device.

FIG. 16 is a timing chart showing signals of respective units in FIG.

FIG. 17 is a diagram showing a state in which pixels are swept out in FIG. 15;

18 is a diagram illustrating a signal charge accumulation state of a pixel in FIG.

FIG. 19 is a diagram showing a read state of a pixel in FIG. 15;

[Explanation of symbols]

 Reference Signs List 6 bar code 7 start pulse generation circuit 7 'counter 8' pulse width setting circuit 8 "counter 9 level detection circuit 9 'amplitude comparator 10 line sensor 14 binarization circuit 34 decoder

Claims (2)

(57) [Claims] 1. An optical recording medium comprising: a display unit optically recorded on a medium ;
Corresponding to s the light receiving element respectively by receiving the light amount in a plurality of light receiving elements
The charge accumulated in the electric storage element, out by reading the level of the detection signal corresponding to the <br/>-acid load volume from the people said storage element each in the order
Input, the display is scanned and read.
And Nau line sensor, the detection signal from the line sensor
And a binarizing circuit for binarizing the data.
In the optical reading device, the storage time of the storage element in the line sensor is determined.
Start pulse generating means for generating a start pulse signal having a pulse width of a predetermined width , and a read operation for designating an operation reference time of the start pulse generation means and a read reference time for sequentially reading out the detection signals from the line sensor. Operation reference signal generation means, and the level of the detection signal from the line sensor is 2
The base to be within the level range that can be binarized by the binarization circuit
It is set with a reference value, the level of the detection signal compared with the reference value, the level of the detection signal relative to the reference value
Detection level determining means for determining the magnitude of the difference , and each time the detection level determining means determines the magnitude ,
The level of the detection signal is equal to the reference value
In the following cases, it is generated by the start pulse generating means.
The pulse width of the start pulse signal is predetermined.
Value, and the level of the detection signal is
When the value is larger than the reference value, the start pulse is generated.
The pulse width of the start pulse signal generated by the
Pulse width setting means for reducing the amount by a predetermined amount , and detecting the detected value according to the determination result of the detection level determining means.
When the signal level is below the reference value, the increase
The pulse width setting means is set and controlled, and the detection signal level is controlled.
If the bell is greater than the reference value,
The pulse width setting means sets a value different from the increment
And a pulse width control means for controlling the level of the detection signal of the line sensor to the reference value.
Cut off the pulse width of the start pulse signal in the direction approaching
An optical reading apparatus, wherein the line sensor performs a plurality of reading scans of the display unit . 2. A display device according to claim 1, wherein said display unit is optically recorded on a medium.
Light is received by multiple light-receiving elements and each light-receiving element is supported
Charge is stored in the storage element that has been
The detection signal of the level corresponding to the charge
Input, the display is scanned and read.
Line sensor and the detection signal from the line sensor
And a binarizing circuit for binarizing the data.
In the optical reading device, the storage time of the storage element in the line sensor is determined.
Start pulse signal that generates a start pulse signal
When the operation generation time of the start pulse generation means is specified
In both cases, the detection signals from the line sensor are sequentially read.
Read operation reference signal generation to specify the read reference time to output
Means and good decoding of the detection signal from the line sensor
Criteria for defining an appropriate level range of the detection signal
Values V _H and V _L (where V _H > V _L ) are set.
The level of the detection signal is compared with the reference values _VH and _VL, and
Determination of the level of the detection signal with respect to the reference values _VH and _VL .
Detection level determining means for performing the determination, and each time the detection level determining means determines the magnitude,
The level of the detection signal is equal to the reference value
When the voltage is equal to or lower than _VL , the start pulse is generated by the start pulse generating means.
The pulse width of the generated start pulse signal is sequentially increased.
So, larger than the level of the detection signal is the reference value V _H
Before the start pulse is generated by the start pulse generator.
The pulse that sequentially reduces the pulse width of the start pulse signal
The detection signal according to the determination result of the detection width determination means and the detection level determination means.
When the signal level is below the reference value _{VL, the} star
To increase the pulse width of the pulse signal sequentially.
The pulse width setting means to control the level of the detection signal.
The start when Le is greater than the reference value V _H
Increase the decrease amount of pulse width of pulse signal sequentially
Controlling the pulse width setting means, the level of the detection signal;
Is within the above-mentioned level range determined by the reference values _VH and _VL.
Sometimes, the change of the pulse width of the start pulse signal is stopped.
Pulse for controlling the pulse width setting means to stop
Width control means , wherein the level of the detection signal of the line sensor is the level
The pulse width of the start pulse signal so that it falls within the range.
And switches the display unit for multiple reading scans to the line
The sensor is configured to perform
Optical reader.