JPH10136272A - Picture input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a picture input device with a built-in illumination device, which is difficult to be affected by disturbance, even if the semiconductor light-emitting element of a light-emitting diode is used by shutter-controlling a semiconductor light-emitting element and a solid-state image pickup element so that a light-emitting period and a light-receiving period are matched. SOLUTION: The solid-state image pickup element 1 is arranged in a position where an object image passing through a lens 2 is image-formed, and it photoelectrically converts the image and outputs an obtained image pickup signal S1 to a synchronizing signal overlap part 4 through an output buffer 3. A pair of light-emitting diodes 6a and 6b are arranged near both ends of the lens 2. LED 6a and 6b emitted/driven by a light-emitting command signal LS outputted from the control part through an LED driver 7 and they function as illumination devices illuminating the object. For preventing the device from being easily affected by disturbance light, the light-receiving period for accumulating the signal charges in the photosensor Ph of the solid-state image pickup element 1 is matched with the light-emitting period for emitting LED 6a and 6b, and light is received by the photosensor Ph only when LED emits light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device integrally provided with an illumination device for illuminating a subject.

[0002]

2. Description of the Related Art In a conventional image input apparatus, when an object is imaged using an illumination device, the illumination is always turned on and an optical image of the object is formed as a two-dimensional image on a photosensor of a solid-state image sensor. In addition, a signal charge accumulated in a photosensor is converted into a voltage signal by photoelectric conversion, and is taken out as a one-dimensional electric signal by an interline transfer method or a frame transfer method.

[0003]

In a conventional image input device, if an attempt is made to produce a small-sized and low-cost integrated image input device with illumination, it is necessary to use a semiconductor light emitting element such as a light emitting diode or a laser diode as the illumination device. There is. However, when such a semiconductor light emitting device is used,
Since the illuminance is low, the light receiving sensitivity has to be increased by increasing the aperture of the lens or increasing the sensitivity of the photo sensor.

[0004] However, when the light receiving sensitivity is increased, there arises a disadvantage that a captured image is more susceptible to disturbance such as flicker of a fluorescent lamp and a shadow of a person. Weakness to disturbance results in significant loss of reliability when performing image processing using a captured image, which is extremely inconvenient. For this reason, conventionally, a large and powerful illumination device having high illuminance had to be used, and it was difficult to reduce the size.

The present invention has been made to solve such a conventional problem. Even if a semiconductor light-emitting device such as a light-emitting diode is used as a lighting device, a small lighting-integrated type that is hardly affected by disturbance. An object is to obtain an image input device.

[0006]

According to a first aspect of the present invention, there is provided a semiconductor light emitting device such as a light emitting diode, and a solid state image pickup device for sequentially taking out signal charges accumulated in a plurality of photosensors as electric signals. A control unit for controlling a light emitting period of the semiconductor light emitting device and a light receiving period of the photo sensor, wherein the control unit is configured to control the shutter of the semiconductor light emitting device and the solid-state imaging device so that the light emitting period and the light receiving period coincide with each other. I do.

[0007] The invention according to claim 2 of the present invention is based on claim 1.
In the invention described, the control unit sets the light receiving period only for a certain period before the end of one vertical period, erases the signal charges accumulated in the photo sensor in the other periods, and electrically removes only the signal charges accumulated in the light receiving period. The solid-state imaging device is controlled so as to be extracted as a signal.

According to the present invention, the light receiving period of the solid-state image pickup device and the light emitting period of the semiconductor light emitting device are synchronized with each other, so that the disturbance resistance when a subject image is picked up is improved. In addition, since the light emitting period is determined in synchronization with the light receiving period, the semiconductor light emitting element is pulse-lighted, and the instantaneous light emission power of the semiconductor light emitting element at the time of pulse lighting is several tens of times that at the time of DC lighting. In addition, disturbance resistance is further improved.

[0009]

FIG. 1 is a block diagram showing an embodiment of an image input apparatus according to the present invention. In FIG. 1, a solid-state imaging device 1 is arranged at a position where a subject image transmitted through a lens 2 is formed, and an imaging signal S1 obtained by photoelectrically converting an image is output to a synchronization signal superimposing unit 4 via an output buffer 3. Output. The synchronizing signal superimposing unit 4 superimposes the horizontal synchronizing signal HD and the vertical synchronizing signal VD output from the control unit 5 on the imaging signal S1 and outputs the superimposed signal as a video signal S2 to the outside.

A pair of light emitting diodes (LEDs) 6a and 6b are arranged near both ends of the lens 2.
The LEDs 6a and 6b are driven to emit light by a light emission command signal LS output from the control unit 5 via the LED driver 7, and function as an illumination device for illuminating a subject.

FIG. 2 is a plan view showing the structure when the solid-state imaging device 1 is formed by an integrated circuit. In the figure, a plurality of photo sensors Ph are arranged in a matrix on a substrate 11 (in this figure, 4 columns × 6 rows), and a CCD (charge coupled device) is provided between the photo sensors Ph in each column. Vertical shift registers VR1 to VR4 are arranged.

Further, each of the vertical shift registers VR1 to VR
At the output end of No. 4, a horizontal shift register HR for one line transfer composed of a CCD is arranged, and is configured to output signal charges accumulated in each of the vertical shift registers VR1 to VR4 line by line. .

The solid-state imaging device 1 is a well-known interline transfer type solid-state imaging device. Therefore, detailed description thereof is omitted, but Vφ1 to Vφ4 are four-phase vertical driving registers for driving the vertical shift registers VR1 to VR4. Hφ1 to Hφ2 are two-phase horizontal register transfer clocks for driving the horizontal shift register HR, VOUT is a signal output, RG is a reset gate clock for converting signal charges into voltage signals, CGG is an output amplifier gate, and VDD is a register transfer clock. A circuit power supply, VL is a protection transistor bias, and SUB is a substrate voltage.

Next, referring to the waveform diagram shown in FIG.
The operation of the image input device according to the present embodiment will be described. In the figure, (a) shows a video signal S2 in one vertical period, and the video signal S2 is composed of a vertical synchronizing signal VD, a horizontal synchronizing signal HD, and an n-line imaging signal S1 (S1 (1)
.. S1 (n)).

The signal charges generated in the photosensor Ph by the light reception of the solid-state imaging device 1 are accumulated in the respective junction capacitors by a charge accumulation operation.
Vertical shift registers VR1 to VR simultaneously adjacent to all pixels
4 is transferred. This transfer is performed every time one vertical period ends. In the present embodiment, the transfer clock Vφ shown in FIG.
This is performed at time t1 when the transfer clocks Vφ1 and Vφ3 among 1 to Vφ4 become high level.

The transfer clocks Vφ1 and Vφ3 take three voltage levels, that is, low level, middle level and high level.
The transfer clocks Vφ2 and Vφ4 are low level, medium level 2
Takes one voltage level. When the transfer clocks Vφ1 and Vφ3 become high level, the signal charges accumulated in the photosensor Ph are transferred to the vertical shift registers VR1 to VR4, and thereafter, the transfer clocks Vφ1 to Vφ4 for each horizontal synchronization period HD.
, And is driven in four phases by a clock that takes a low level and a medium level, and signal charges of one bit are transferred to the horizontal shift register HR every one horizontal period.

At first, among the signal charges transferred to the registers VR1 to VR4, the signal charges in the lowermost line are transferred to the horizontal shift register HR. Horizontal shift register H
The signal charges of one line transferred to R are shifted by transfer clocks Hφ1 to Hφ2 shown in (c), and signal charges of one line are output during one horizontal period.

By repeating this operation, signal charges of all lines are converted into voltage signals by the reset gate clock RG within one vertical period, and the image signals S1 (1) to S1 ( n) is output.

The image signal S1 thus output is superimposed on the horizontal synchronizing signal HD for each horizontal period by the synchronizing signal superimposing section 4 and superimposed on the vertical synchronizing signal VD for each vertical period, and is output as a video signal S2. Is done.

In the present invention, the photo sensor P of the solid-state image pickup device 1 is provided so as to be hardly affected by disturbance light.
h, a light receiving period for accumulating signal charges in the LEDs 6a, 6b
Are matched with the light emission period of the LEDs 6a and 6b.
Is received by the photo sensor Ph only when is emitting light.

That is, in this embodiment, as shown in (d), the substrate voltage SUB is set to a voltage higher than the normal voltage every one horizontal period, and before the end of one vertical period, for example, the line S
The substrate voltage SUB is maintained at the normal voltage during the period from the start time t2 of 1 (n-1) to the time t1. Thus, the time point t2 to the time point t1 are set as the light receiving period.

This is because the solid-state imaging device 1 has a substrate voltage SUB
Is a normal voltage of about 5 to 10 volts, the signal charge photoelectrically converted by the photosensor Ph is stored.
When the substrate voltage SUB is higher than normal (for example, 22.5
(Volts), the signal charge accumulated in the photosensor Ph does not move to the vertical shift registers VR1 to VR4, but is discharged to the outside as it is.

Therefore, the substrate voltage SUB is set to a high voltage every one horizontal period to release the signal charges accumulated in the photosensor Ph, but the substrate voltage SUB is maintained at the normal voltage only during the period from time t2 to t1. I am trying to do it. Then, at the time point t2 when the substrate voltage SUB finally becomes a high voltage.
From the photosensor Ph to the vertical register VR1
Only the signal charges of the light received during the time t1 when the signal charges are transferred to the vertical registers VR1 to VR4 are transferred to the vertical registers VR1 to VR4. That is, the signal charge output in one vertical period is only light accumulated between the time points t2 and t1.

Further, the control unit 5 outputs the light emission command signal LS between the time points t3 and t4 in synchronization with the accumulation time period t2 to t1, and makes the LEDs 6a and 6b emit light only during this time. By doing so, an image only when the LEDs 6a and 6b are emitting light is photoelectrically converted and output.

In general, the LEDs are IF to IE shown in FIG.
As shown in the characteristic diagram, when the pulse lighting is performed, the instantaneous output power can be larger than that at the time of the normal DC rating, and about 30 times.
It is possible to double. In other words, the rated value is 45 mm / sr for DC lighting, but 1200 mm / sr for pulse lighting.
The instantaneous light emission power can be increased to a degree. Therefore, the resistance to the disturbance is LE compared to the conventional case where the LED is turned on DC and the shutter is not operated.
It becomes stronger by the power-up of D (about 30 times).

[0026]

According to the present invention, the solid-state imaging device 1 is LE
Since only the incident light at the time of lighting of D6a and D6b is received, a great effect can be exerted on improvement of disturbance resistance when capturing an image. Moreover, since the light emitting power of the light emitting diode is several tens times larger than that of the light emitting diode when pulse lighting is performed, even if a light emitting diode having a small DC rating is used, it is possible to exert a great effect on improvement of disturbance resistance. .

[Brief description of the drawings]

FIG. 1 is a block diagram of an image input device according to an embodiment of the present invention.

FIG. 2 is a plan view of the structure when the solid-state imaging device is configured by an integrated circuit.

3A and 3B are waveform diagrams for explaining the operation according to the present embodiment, wherein FIG. 3A shows a video signal S2, FIG. 3B shows vertical register transfer clocks Vφ1 to Vφ4, FIG. 3C shows horizontal register transfer clocks Hφ1 to Hφ2, and FIG. d) is the substrate voltage SUB,
(E) is a light emission command signal LS.

FIG. 4 is a graph showing IF to IE characteristics of a light emitting diode (LED).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid-state image sensor 2 Lens 3 Output buffer 4 Synchronization signal superposition part 5 Control part 6a, 6b Light emitting diode (LED) 7 LED driver

Claims (2)

[Claims] A semiconductor light-emitting element such as a light-emitting diode; a solid-state image pickup element for sequentially extracting signal charges accumulated in a plurality of photosensors as electric signals; and a light-emitting period of the semiconductor light-emitting element and a light-receiving period of the photosensor. An image input device, comprising: a control unit that controls the semiconductor light-emitting element and the solid-state imaging element so that the light-emitting period and the light-receiving period coincide with each other. 2. The method according to claim 1, wherein the control unit sets a light receiving period only for a certain period before the end of one vertical period, erases signal charges accumulated in the photo sensor in another period, and stores the signal charges accumulated in the light receiving period. 2. The image input device according to claim 1, wherein the solid-state imaging device is controlled so that only the electric signal is extracted as an electric signal.