JPH10134134A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save the electric power and to fastly start-up operation for resetting a stand-by mode. SOLUTION: When a switch 36 is switched to the stand-by mode, only a CCD 16 and a driver 30 are supplied with electric power and becomes low- power-consumption mode. When an AGC mode is switched off with a switch 40, switching to a capacitor C2 which gives a low time constant is performed to make the startup of the operation of an AGC circuit fast. Therefore, the operation starts up fast even when the stand-by mode is reset, so a stable image pickup signal is obtained to stabilize the signal and prolong the life of a battery by saving the electric power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus suitable for reading a two-dimensional code or the like. Specifically, a low power consumption mode for reducing the power consumption of the battery power supply is provided, and in addition to the AGC mode in which the AGC circuit can be turned on and off, the clamp circuit constant in the AGC circuit is switched in conjunction with the AGC mode. In particular, the present invention relates to a power saving type imaging apparatus that can quickly start up when a low power consumption mode is released.

[0002]

2. Description of the Related Art Among image pickup apparatuses, a dedicated image pickup means for reading a bar code or a two-dimensional code obtained by further developing the bar code is known. The imaging device is connected to a register so that an operator can read a code attached to a product by the imaging device.
Therefore, this imaging device as a code reading unit is reduced in size and weight. The driving power source employs the simplest method, and a battery (battery) is usually built in the apparatus body.

[0003] Since the battery is driven by a battery, it is necessary to take measures to extend the life of the battery. In particular, when used as code reading means, the operation of reading a code is not performed continuously, but is an extremely intermittent reading operation. Therefore, if the power is always turned on, the life of the battery is extremely shortened, and the battery must be replaced frequently.

[0004]

One way to extend battery life is to provide a standby mode, which is a low power consumption mode. If the power is turned off when the code is not read, and the power is connected only when the code is read, the life of the battery can be greatly extended.

[0005] On the other hand, such an imaging apparatus is usually provided with an AGC circuit as internal processing. Even when the signal level of the captured image varies,
An AGC circuit is provided so as to be able to output as a fixed level image signal.

The rise of the signal level when the standby mode is released largely depends on the response characteristics of the AGC circuit. Since the response characteristics of the AGC circuit are determined on the assumption that the input light amount changes greatly,
It takes several hundred milliseconds or more to obtain a stable output.

Further, when a two-dimensional sensor such as a CCD is used as an image pickup device, the rising speed of the two-dimensional sensor is also a problem, and until the standby mode is released and a stable reading output is obtained immediately. Either way, you have to wait for some time.

In view of the above, the present invention has been made to solve such a conventional problem, and proposes a power saving type imaging apparatus which can extend the battery life without lowering the rising speed.

[0009]

In order to solve the above-mentioned problems, the image pickup apparatus according to the present invention is provided with a standby mode functioning as a low power consumption mode. In the standby mode, a voltage is supplied only to a specific circuit. In addition, the AGC circuit is provided with an AGC mode switching switch for switching between the AGC mode and the fixed gain mode, so that the AGC mode is switched on and off simultaneously with the feedback loop provided in the AGC circuit. It is characterized in that the constant clamp constant can be switched.

In the present invention, a standby mode functioning as a low power consumption mode is provided. In the standby mode, the power supply voltage is supplied only to a specific circuit.
Specifically, a power supply voltage is always applied to the CCD which is a two-dimensional sensor and its driver.

The AGC circuit is provided with a switch for switching between an AGC mode and a fixed gain mode, and a switch for switching a time constant provided in a feedback loop of the AGC circuit. The switch for the fixed gain mode in which the AGC mode is turned off is provided. At times, a value smaller than that in the AGC mode is selected as the time constant.

In this way, in the imaging mode for reading a barcode or a two-dimensional code, the AGC
Switch the mode off. Since the AGC mode is off, the AGC operation is not performed and the rise of the amplifier (clamp circuit) of the AGC circuit is accelerated.

When picking up an image of a bar code, a two-dimensional code, or the like, it is often used in a place where the imaging conditions are stable and there is a sufficient amount of input light to obtain a sufficient imaging signal level. Therefore, even when the AGC mode is turned off, a stable imaging output can be obtained immediately after the standby mode in the imaging under the constant illuminance, so that the battery life can be extended without lowering the reading speed. If a light source is turned on and an illumination is turned on at the time of imaging, more stable bar code reading can be realized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a case where an embodiment of an image pickup apparatus according to the present invention is applied to a code reader such as a bar code will be described in detail with reference to the drawings.

In the imaging apparatus 10 shown in FIG. 1, a subject image 12 such as a bar code or a two-dimensional code is formed on a CCD 16 as a two-dimensional sensor via an optical system 14 and is converted into an electric signal (image signal). You.

FIG. 2 shows an example of the two-dimensional code. The example in the figure illustrates a data code among two-dimensional codes.
In this case, the L-shaped frame 52 and the rectangular frame 53 among the substantially rectangular frames are respectively used as cutout symbols, and an area 54 surrounded by these rectangular frames 52 and 53 is used as a data area. By arranging unit rectangular frames having the same shape as the rectangular frame 53 in the data area 54 in the horizontal and vertical directions, data of “1” (black area) and “0” (white area) are constructed.

Since the code is developed on a two-dimensional plane as described above, a two-dimensional sensor is used as an image sensor so that the two-dimensional code can be read. As a form of the two-dimensional code, in addition to FIG.
Codes, vericodes, CP codes and the like are known.
The present invention is applicable to reading any two-dimensional code.

The image pickup signal obtained from the CCD 16 is sampled and held by a sampling and holding circuit 18, and its output is controlled by an AGC circuit 20 so that the output level becomes constant, and then supplied to a processor 26 to perform predetermined signal processing. And output as a normal video signal.

The AGC circuit 20 is composed of an AGC amplifier 22, a clamp circuit 23 and a level detection circuit 24 disposed on its negative feedback path, as is well known.
Determines the time constant of the negative feedback path.

The signal generation circuit 28 generates various timing signals TG and synchronization signals SG. The timing signal TG is supplied to the sampling and holding circuit 18 as a sampling and holding signal, and is also supplied to a driver 30 to generate various signals (such as a transfer clock) for driving the CCD 16. The horizontal and vertical blanking signals of the synchronization signal SG are supplied to the processor 26.

In the power supply circuit 32, a battery 34 is used as an input power supply. In this example, a battery voltage of 6 volts is boosted by the power supply circuit 32, and in the example of FIG. Different voltages are formed. In the above-described circuit system, the CCD 16 has a voltage of 15 volts and-
The 9 volt voltage is used as a voltage for the transfer clock signal and the like. Similarly, the CCD driver 30 has a voltage of 15 volts.
A voltage of 9 volts is used as the driving voltage.

On the other hand, the other circuits, that is, the sampling and holding circuit 18, the AGC circuit 20, the processor 26, and the signal generating circuit 28 are all driven by a 5-volt power supply.

A standby switch 36 is provided between the power supply circuit 32 and the driving battery 34. By operating this switch 36, two types of standby mode s, which function as a normal operation mode n and a low power consumption mode, are provided. It can be switched to power mode.

When the imaging device 10 is used as a code reading device, the operation of reading a code is not always performed continuously, but is performed only intermittently. If anything, the code reading standby time is longer. Therefore, when the code reading operation is not performed, the mode is switched to the standby mode to minimize power consumption.

Therefore, in the present invention, the normal operation mode n
In this case, all three types of voltages, which will be described later, are output from the power supply circuit 32.
Only two voltages, volts and -9 volts, are output, and the supply of 5 volts is stopped.

The reason why power is always supplied to the CCD 16 and the driver 30 is that if a drive voltage is not supplied to these components, it takes a considerable time until a stable image signal is obtained from the CCD 16. This is because the entire rise is delayed.

Of course, if the 5 volt power supply system is cut off, it takes a long time to obtain a normal signal. In particular, if the AGC circuit 20 is present, it takes about 250 msec until the AGC system becomes stable, as described later. Time is needed. However, in order to save battery power, it is necessary to add a low power consumption mode function. Therefore, the following configuration is further added from the standpoint of system startup and power saving.

In the negative feedback path of the above-mentioned AGC circuit 20, A
A switch 40 for switching the GC mode is associated with the AGC mode on the terminal p side, and the AGC mode on the terminal q side.
The mode is prohibited. In other words, the mode becomes the fixed gain mode and operates as a simple fixed gain amplifier.

AGC amplifier 2 in fixed gain mode
The gain of 2 is determined by the drive voltage (5 volts) supplied to the AGC circuit 22 and the gain control signal (voltage) supplied from the terminal 25. As the gain control signal, a signal generated by a controller (not shown) that controls the entire imaging apparatus is used.

To the clamp circuit 23, two types of capacitors C1 and C2 for determining the time constant of the negative feedback path, in this example, for determining the clamp characteristics, are connected via a switch 42. The first capacitor C1 is a capacitor used in the AGC mode, and its capacitance is selected to be, for example, about 1.0 μF as shown in FIG. When a normal subject is imaged, the brightness at that time is not constant. Therefore, in order to be able to cope with fluctuations in the normal input light amount, the above-mentioned value is selected as the clamp capacitor in the AGC mode. I have.

On the other hand, the second capacitor C2 is A
A capacitor which is used when the GC mode is released and which has a value sufficiently smaller than that of the first capacitor C1 is used. In the example of FIG. 3, a value of about 1/10 (0.1 μF) is selected.

The pair of switches 40 and 42 provided in the AGC circuit 20 are configured to be switched in conjunction with each other, and the solid line is shown when the AGC mode is switched, and the broken line is shown when the fixed gain mode is switched. It is.

Here, if the clamp constant is large, it takes time until the system of the AGC circuit 20 becomes stable, and if the clamp constant is small, the time until the system becomes stable can be shortened. For example, when the numerical relationship shown in FIG. 3 is selected, when the first capacitor C1 is used, it takes approximately 250 msec until the system of the AGC circuit 20 is stabilized.

When the negative feedback path of the AGC circuit 20 is cut, the AGC operation is not performed. However, since the clamp constant at that time is small, the response characteristic to the input signal becomes faster, and in the example of FIG. .

Therefore, even in the state where the standby mode s is selected, if the AGC mode is turned off, the rise of the operation is fast. Therefore, even when switching from the standby mode s to the normal operation mode n, a stable imaging signal can be output to the processor 26 immediately after switching to the normal operation mode n.

When an image is taken under relatively stable illuminance for reading a code as described above, the standby mode s is selected and the AGC mode is preferably used in an off state.

By the way, even when the AGC mode is turned off, such a stable image pickup signal is obtained only when the CC mode is set.
This is because the imaging condition of D16 is relatively stable. That is, when reading a two-dimensional code or the like, it is almost always used in an illuminated room, that is, an image is taken under a constant illuminance. This is because there is no extreme change.

In order to secure more stable brightness, light for reading a code may be applied to the subject 12. For this purpose, a light source 46 for illuminating the subject is provided as necessary. In this example, as shown in FIG.
4 to a light source (eg, an LED) 46.

In this embodiment, the switch 44 is also switched in conjunction with the switches 40 and 42 described above.
Power is supplied only when the AGC mode is released, and the subject 12 is illuminated. This is AGC
This is because a stable image signal can be obtained by the AGC operation of the AGC circuit 20 in the AGC mode, so that no light source is required in the AGC mode.

The switch 44 is not necessarily the switches 40, 4
There is no need to link to 2. This is because an environment in which a code can be read under extremely favorable conditions is conceivable. In such a case, the light source 46 is rather used in order to save power.
It is better to turn off. Conversely, a configuration in which all the switches 36, 40, 42, and 44 are interlocked can be adopted.

FIG. 4 shows an example of the arrangement of the light sources 46. In the figure, two light sources 46, 46 are arranged on the front surface 10a side of the apparatus main body 10 on the left and right sides of the optical system 14 so that light is emitted at the position of the subject 12. Hit. The standby switch 36 is attached to a part of the device case 58, and the interlock switch 4
One of the switches 0, 42, and 44, in the figure, the switch 40 is mounted so as to be operated from the outside.

[0042]

As described above, according to the present invention, when the standby mode functioning as the low power consumption mode is selected, the voltage is supplied only to a specific circuit, thereby greatly reducing power consumption. Can be suppressed. Therefore, a longer life of the battery due to the power saving effect can be achieved.

Further, when the AGC mode is turned off, A
Since the rise of the operation is accelerated by simultaneously switching the time constant of the negative feedback path of the GC circuit, a stable imaging signal can be obtained immediately after the switching from the standby mode to the normal operation mode. As a result, the disadvantage of the AGC circuit can be overcome.

Therefore, the present invention is extremely suitable for application to an image pickup apparatus capable of picking up an image under a relatively stable light amount, such as a code reader for two-dimensional codes.

[Brief description of the drawings]

FIG. 1 is a system diagram of a main part showing an embodiment in which an imaging device according to the present invention is applied to a code reading device.

FIG. 2 is a configuration diagram of a two-dimensional code.

FIG. 3 is a characteristic diagram illustrating rising characteristics of the AGC circuit.

FIG. 4 is a plan view showing an example of the arrangement of light sources.

[Explanation of symbols]

10 ... Imaging device (code reading device), 12 ...
・ Subject, 16 ・ ・ ・ CCD, 20 ・ ・ ・ AGC circuit,
22 ... AGC amplifier, 24 ... Clamp circuit, 3
0: driver, 32: power supply circuit, 34: battery, 36: standby switch, 40, 42, 44
... AGC mode switch, 46 ... Light source

Claims (4)

[Claims] A standby mode functioning as a low power consumption mode is provided. In the standby mode, a voltage is supplied only to a specific circuit, and the AGC circuit has an AGC mode and a fixed gain mode. A switch for switching the AGC mode is provided.
An imaging apparatus, wherein a clamp constant of a time constant of a feedback loop provided in a circuit is switched. 2. A switch for turning on and off a light source for irradiating a subject with light is provided.
2. The imaging apparatus according to claim 1, wherein the C mode is controlled to be switched, and a fixed gain mode is set at the time of imaging with the light source turned on, and a small time constant is selected. 3. The image pickup apparatus according to claim 1, wherein said voltage is supplied only to the image pickup element and its driver circuit in the standby mode. 4. The imaging apparatus according to claim 1, wherein said time constant is a clamp constant of a clamp circuit provided in an AGC circuit.