JPS6354889A - Vehicle number plate reader - Google Patents

Abstract

PURPOSE:To always correctly read the number plate of a travelling vehicle by providing an image pickup reading part having a solid-state image pickup element and a clear pulse generating part and an EE lens part for adjusting an exposure in a camera part and providing a signal processing part in an information detecting part. CONSTITUTION:When the clear pulse for completely clearing a stored charge within a vertical synchronizing signal output period is supplied to the solid-state image pickup element 12 constituting the image pickup reading part 8, a shutter function can be executed and a mechanical shutter or a PLZT electronic shutter is not required. Since the solid-state image pickup element 12 is highly sensitive, the number plate can be read at a shutter speed >=1/1000 sec, respectively without an illumination from sunshine to twilight and by the illumination of about several luxes at night. Since the EE lens part 10 is provided, the quantity of the exposure is adjusted to a change in an external light, so that a constantly proper information signal output can be obtained. Thereby, the number plate of the travelling vehicle can be constantly correctly read.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vehicle license plate reading device for reading license plates of traveling vehicles.

<Prior art and its problems> Generally, in order to accurately read the license plate of a traveling vehicle, a shutter speed of 1/1o00 sec or more is required. In order to meet this demand, conventional equipment includes (
1) Image tube camera with mechanical shutter function, (i
i) A TV equipped with a solid-state image sensor, a camera equipped with a PLZT electronic shutter as an electro-optic effect element, (
! ! For the above (1) and (ii), methods using a strobe light source have been proposed.

However, each of the above devices has the following drawbacks. That is, in the case of (j), if the mechanical shutter is used frequently, failures are likely to occur and the lifespan is short. Furthermore, image pickup tubes have a short lifespan and are expensive. (If in, P
Since the LZT electronic shutter uses polarized light, the amount of transmitted light is small. Therefore, in order to obtain a shutter speed of I/1000 sec, lighting of several thousand lux is required at all times, and it cannot be used outdoors. In case (iii),
The effect depends on the brightness of the surrounding outside light, and especially during sunlight, the outside light can reach several hundred lux, so there is no point in using a strobe light source. Moreover, using a strobe at night is not desirable because it may lead to driving errors by the driver.

In addition, in the conventional device described above, in order to photograph the license plate of a moving vehicle, a vehicle detector such as an ultrasonic detector or a loop coil detector is separately installed, and the information from this vehicle detector is Since it was necessary to operate the flasher, strobe, camera, etc. in response to the sensing signal, the entire device including peripheral devices became expensive.

<Purpose of the Invention> The present invention solves the problems of the prior art, allows the license plate of a traveling vehicle to be read accurately from daylight to night, has a long service life, and can be used for a conventional vehicle. The purpose is to reduce the cost of the entire device by eliminating the need for a sensor.

<Configuration and Effects of the Invention> (Configuration) In order to achieve the above object, the present invention adopts the following configuration. That is, the vehicle license plate reading device of the present invention includes: a camera unit that is installed on the road with the vehicle viewed from above; a signal processing unit that processes information signals of still images obtained by the camera unit; The camera unit outputs a clear pulse that completely clears the charges accumulated in a frame transfer solid-state image sensor and this solid-state image sensor arranged in a state where it is constantly exposed to external light within a vertical synchronization signal output period. an imaging reading section having a pulse generating section; and an EE lens section for exposure adjustment provided at the front part on the incident side of the imaging reading section; It includes an information detection section that detects necessary license plate information from the still image information signal.

(Effect) Therefore, according to the present invention, by applying a clear pulse that clears all accumulated charges to the solid-state image sensor constituting the image reading section within the vertical synchronization signal output period, the gloss soter function can be effectively achieved. This eliminates the need for a mechanical shutter or PLZT electronic shutter. Since the solid-state image sensor is highly sensitive, it is possible to read license plates at a glossy speed of 1/1000 sec or more with no illumination from daylight to dusk and with a few hundred lux of illumination at night. can. Furthermore, since the EE lens section is provided, the exposure amount is adjusted in response to changes in external light, so that an appropriate information signal output can always be obtained. Therefore, the license plate of a traveling vehicle can be read accurately at all times, and the life of the device can be extended.

However, since a predetermined number of still images are always obtained by the imaging reading section, and the information detection section detects the necessary license plate information from among them, a vehicle detector such as an ultrasonic detector is not required. Therefore, the cost of the entire device can be reduced.

<Description of Embodiments> The present invention will now be described in detail with reference to embodiments shown in the drawings.

FIG. 1 is a block diagram showing the entire apparatus of the present invention.

The vehicle license plate reading device l of the present invention has a second
As shown in the figure, it consists of a camera 4 installed on the road with the vehicle 2 looking down, and a signal processing unit 6 that processes information signals of still images obtained by the camera unit 4. The camera section 4 includes an image reading section 8 and an EE lens section 1O for exposure adjustment provided at the front part of the image reading section 8 on the incident side.

The above-mentioned imaging reader 18 includes a frame transfer type solid-state imaging probe 12 arranged so as to be constantly exposed to external light. That is, this solid-state image sensor 12 has C
The CDCD imaging section consists of a 4CD storage unit 16 and a horizontal knot register 18. And CCDCD imaging department 4
The photoelectrically converted signal charges are accumulated according to the brightness of the incident light. The image data (signal charge) accumulated in the CCD imaging section 14 is transferred to the CCD accumulation section 16 by one horizontal line each time one first transfer pulse P1 is inputted from the timing signal generation section 22, which will be described later. Ru. The image data stored in the COD storage unit 4 is transferred to the horizontal shift register 18 by one horizontal line each time one second transfer pulse Ps is input from the timing signal generation unit 22. Further, the image data for each l horizontal line transferred to the horizontal shift renostar 5 is sequentially outputted by inputting the third transfer pulse T from the timing signal generating section 22.

Furthermore, the imaging reading section 8 applies pulses Pi to each section 14, 16, and 18 of the solid-state imaging device 12, respectively.

A driver 20 that outputs Ps and T, and a vertical synchronization signal V
D. When the timing signal generating section 22 that generates the above-mentioned pulses Pi, Ps, and T in synchronization with the horizontal synchronizing signal HD and the vertical synchronizing signal VD and the vertical synchronizing signal VD from the timing signal generating section 22 are input as a clear signal. And to you,
A presettable counter 24 that counts the horizontal synchronization signal HD, and a CCD imaging section 14 and a CCD storage section 16 in response to a coincidence signal I that is output when the count value of this counter 24 matches a preset value. A clear pulse generator 26 that outputs a clear pulse CP that clears all accumulated charges, and first and second OR circuits 28.30
It is equipped with

The above timing signal generation section 22 generates a vertical synchronization signal VD.
A predetermined number of horizontal synchronizing signals (for example, 259 pulses if one field is composed of 259 horizontal scanning lines) is output during the output period (one field period indicated by the symbol T in FIG. 3). In addition to outputting HD, vertical synchronization signal VD
The first, second and third transfer pulses P I % P synchronized with
Output S s T respectively. Further, the counter 24 is configured so that two set values can be preset, and when the count value matches the preset set value, a match signal I is outputted. and,
This set value controls the output timing of the clear pulse CP from the clear pulse generator 26, and as a result,
The amount of accumulated charge of the solid-state image sensor 12 is adjusted, and substantially,
゛It will serve as a tsuyatta speed function. In addition, 3
2 is an oscillator provided in the timing signal generating section 22.

On the other hand, the EE lens section IO includes a photographic lens 34, a condensing lens 36, an aperture blade 38, a light amount detection element 40, and each output level of a detection signal from this light amount detection element 40 and an information signal output from the solid-state image sensor 12. An EE setting circuit 42 that sets the aperture according to the EE setting circuit 42 and an aperture controller 44 that adjusts the opening degree of the aperture blades 38 according to the aperture setting signal from the EE setting circuit 42 are provided.

The signal processing section 6 includes an amplifying section 4 that amplifies the information signal transferred from the horizontal shift register I8 of the solid-state image sensor 12.
6, an A/D converter 48 for A/D converting the output of the amplifying section 46, an image memory 50 for storing the A/D converted information signal as still image data, and a still image data read from the image memory 50. A D/A converter 52 converts the still image data into D/A, a CRT 54 displays the output of the D/A converter 52 as an image, and a necessary number is obtained from the still image data stored in the image memory 50. and an information detection section 56 that detects plate information. The above information detection section 5
6 performs differential processing on the still image data in the image memory 50 to cut out the license plate pattern, performs character recognition, and outputs the detection result of the license plate along with information on the presence or absence of a vehicle. .

Next, the operation of the vehicle license plate reading device 1 of this embodiment will be explained with reference to the time chart of FIG. 3.

The incident light of the EE lens section 10 passes through the photographing lens 34, the aperture blades 38, and the condensing lens 36, and is exposed to the CCD imaging section 14 of the solid-state imaging device 12.
Signal charges corresponding to the brightness of the light are accumulated in the i-image portion I4.

Further, the light transmitted through the condenser lens 36 is transmitted to the light amount detection element 4.
0 is detected, and the detection signal is given to the EE setting section 42. The EE setting section 42 outputs an aperture setting signal according to this detection signal, and this aperture setting signal is input to the aperture controller 44. Since the diaphragm controller 44 adjusts the opening degree of the diaphragm blades 38 in accordance with this diaphragm setting signal, the diaphragm is automatically controlled in accordance with the brightness of external light.

On the other hand, in synchronization with the rising timing included in the vertical retrace period T0 of the vertical synchronization signal VD, the timing signal generator 22 outputs an eleventh second transfer pulse Pi, Psh<1 during the period T1 in FIG. The number corresponding to one field (
In this example, only 259 pulses) are output, and the first transfer pulse Pi is sent to the CC via the first OR circuit 28 and the driver 20.
A second transfer pulse Ps is also applied to the D imaging section 14 via the second OR circuit 30 and the driver 20 between the COD storage sections 6. As a result, C within the above period T1
The image data (signal charge) for 1 field accumulated in the CD imaging section 14 is transmitted between the COD storage sections 6, and new charge accumulation in the CCD imaging section 14 is started.

Then, in the period following this, the second transfer pulse Ps is sequentially output from the timing signal generator 22 in synchronization with the horizontal synchronization signal 11D, and the second transfer pulse Ps is outputted via the second OR circuit 30 and the driver 20. 6 between the COD accumulation and accumulation sections. Therefore, the image data stored in the COD storage unit 4 is transferred to the horizontal shift register 18 by one horizontal line each time one second transfer pulse Ps is input. Then, the image data for l horizontal lines set in the shift register 18 is read out and transferred to the signal processing section 6 by the third transfer pulse T from the timing signal generation section 22.

In this way, the above operation is continued until the clear pulse CP is output from the clear pulse generator 26.

On the other hand, the counter 24 is cleared by the vertical synchronizing signal VD, and counts each time the horizontal synchronizing signal HD is added. When the count value matches the smaller of the two previously set preset values, the counter 24 outputs a match signal (2), and this match signal (2) is applied to the clear pulse generator 26. The clear pulse generator 26 generates a clear pulse C in response to the coincidence signal I.
Generate P. The clear pulse CP is outputted by the number of pulses for one field (259 pulses in this example) within the period indicated by the symbol T in FIG.

Then, this clear pulse CP is the 11th second OR circuit 2.
8.30, is applied to the CCD imaging section 14 and the CCD storage section 16 via the driver 20, respectively. the result,
The image data stored up to the COD storage section I6 is discarded, and the image data for 1 field stored in the CCDCD impression 4 is newly transferred to and stored in the COD storage section I6.

Subsequently, the count value of the counter 24 is set to 2.
When a match is made with the larger of the two preset values, the counter 24 outputs a match signal I, and this match signal ■
is given to the clear pulse generator 26. therefore,
Similarly to the above, the clear pulse generating section 26 outputs the clear pulse CP as many as the number of pulses for one field (259 pulses in this example) within the period indicated by the symbol T3 in FIG. As a result, the image data that had been stored in the COD storage unit 6 is transferred, and the image data from the CCDCCD impression 4 is newly transferred to the C, CD storage unit 6, but the first clear The accumulated charge in the CCD imaging section 14 has been completely cleared by the pulse CP, and therefore,
From the first clear pulse CP to the second clear pulse C
Since the period until P is output is extremely short, the image data transferred between the COD storage sections becomes substantially non-signal data. Therefore, in step 27, where the clear pulse CP is applied twice, all signal charges accumulated in the CCDCD impression 4 and the CCD storage section 16 are cleared. This is equivalent to the shutter being closed from the rise timing of the vertical synchronization signal VD to the all-clear time. in this way,
The occurrence of blooming is suppressed by once all clearing the CCD imaging section 14 and the CCDW product section 6.

Immediately after the second all-clear, accumulation of signal charges starts in the CCD imaging section 14, and the accumulation continues until the next rise timing of the vertical synchronization signal VD. Therefore, the actual accumulation period of signal charges to be outputted as an information signal from the solid-state image sensor 12 is the period Tint from the time of all clear to the rising timing of the next vertical synchronization signal VD. Since this accumulation period T int corresponds to the shutter speed, shortening the accumulation period corresponds to increasing the shutter speed. Therefore, a shutter speed of approximately I/1000 sec can be obtained without impairing detection sensitivity. The period Ti is determined according to the traveling speed of the subject vehicle and the brightness of outside light.
nt is set.

Then, at the rising timing of the vertical synchronization signal VD, as mentioned above, the 11th second transfer pulse P1 is transmitted by the number of pulses corresponding to one field during the predetermined period T.
, Ps are output, and the signal charge accumulated in the CCD imaging section I4 during the above accumulation period T int becomes COD.
It is transferred to the storage unit I6.

Thereafter, each time the second transfer pulse PS synchronized with the 6-line synchronization signal HD on the COD storage unit is sequentially applied, l horizontal lines are transferred to the horizontal soft register 18, and further,
The image data set in the horizontal shift reno star 18 is sequentially read out by the third transfer pulse T. Therefore, when the field period is 1/60 seconds, the image reading section 8 always sends information signals of 60 still images per second to the signal processing section 6.

In this embodiment, since the clear pulse CP is applied during the transfer of image data from the CCD storage unit 16, the subsequent image data will be lost, but the loss of image data will occur when the l field is Since there are only a few to several dozen scanning lines at most out of the 259 scanning lines that make up the system, there is no problem in responding to the data processing of the still image and reading the license plate.

In this way, the information signal output from the solid-state image sensor 12 is amplified by the amplifying section 46. A part of this signal is fed back to the EE setting circuit 42, and the aperture is adjusted according to the output level of the information signal.

Further, the information signal from the amplifying section 46 is 1. The data is A/D converted by the A/D converter 48 and stored in the image memory 50 as still image data. The still image data stored in the image memory 50 is read out at a predetermined timing, and after being D/A converted by the D/A converter 52, the still image data is transferred to the CRT.
54 as a still image. Further, the still image data stored in the image memory 50 is sent to the information detection section 56.

The information detection unit 56 performs differential processing on the still image data provided from the image memory 50 to extract the license plate pattern, performs character recognition, and outputs the license plate detection results along with information on the merits and demerits of the vehicle. C
Output to RT54 or a printer not shown.

[Brief explanation of drawings]

The drawings show an embodiment of the vehicle license plate reading device of the present invention, and FIG. 1 is a block diagram showing the entire device of the present invention, FIG. 2 is an explanatory diagram showing the installation state of the camera section of the device, and FIG. Figure 3 is a time chart used to explain the operation of the device. ■...Vehicle license plate reading device, 4...Camera unit, 6...Signal processing unit, 8...Image reading unit, 1
O-EE: z section, 12 - solid-state image sensor, 26...
Clear pulse generation section, 56... information detection section.

Claims (1)

[Claims] (1) Consists of a camera unit installed on the road with a bird's-eye view of the vehicle, and a signal processing unit that processes information signals of still images obtained by this camera unit, and the camera unit is constantly exposed to external light. an imaging reading section having a frame transfer type solid-state imaging device arranged in a state where the image sensing device is configured to have a frame-transfer type solid-state imaging device, and a clear pulse generating section that outputs a clear pulse that completely clears the accumulated charge of the solid-state imaging device within a vertical synchronization signal output period; and an EE lens section for exposure adjustment provided at the front part on the incident side of the image reading section, while the signal processing section processes necessary license plate information from the information signal of the still image obtained by the image reading section. A vehicle license plate reading device comprising an information detection section that detects.