JPH06153093A - Image pickup device providing with signal processing part - Google Patents

Abstract

PURPOSE:To uniformize the output signals of respective channels with high precision and with simple configuration by removing test signal supply mechanism to the output of an image pickup device and providing a signal processing function for automatically adjusting the amplification ratio of the respective channels. CONSTITUTION:When a switch 116 is turned on, a timing pulse generating circuit 117 generates a timing pulse which is required for the operations of the output signal level detecting equipments 108-1 and 2 for the respective channels. An LED driving circuit 118 is operated for a period of time set by the timing pulse and LED 115-2 is light-emitted. Thus, the output signals of two channels obtained from the image pickup device 101 are respectively inputted to a comparator 109 through a pre-amplifier, an amplifier and the output signal level detecting equipments, a signal corresponding to signal level difference is supplied to a signal level control register 110 and the output signal contents of the register is updated whenever a register difference output is generated from the comparator. A gain adjusting circuit 111 automatically adjusts gain by the signal contents of the register 110.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus using a multi-channel read type image pickup element and provided with a signal processing section.

[0002]

2. Description of the Related Art Conventionally, a multi-channel readout type image pickup device is used, and signals obtained from a large number of output terminals of the image pickup device are individually amplified and then combined to form a video signal. In the image pickup apparatus described above, since the amplification factors of the signal processing system after the pixels of the image pickup element of each channel do not completely match between the channels, for example, in the case of 2-channel reading, as shown in FIG. In many cases, noise of amplitude ΔV is superimposed on the one-lined output signal synthesized by the changeover switch controlled by the channel changeover pulse.

Various methods have been proposed for the purpose of solving such a problem of noise. Next, a conventional example of an image pickup apparatus that reduces such noise will be described with reference to FIG. In FIG. 4, reference numeral 1 denotes a current output type solid-state image pickup device that uses CMD, AMI, etc. for converting an optical image of an object into an electric signal as pixels, and outputs signals from two channel output lines 2-1 and 2-2 at the same time. To read. Reference numerals 3-1 and 3-2 denote preamplifiers, each of which converts a current signal sent from the solid-state image pickup device 1 through the output lines 2-1 and 2-2 into a voltage signal, which includes a voltage follower type operational amplifier and a feedback resistor. The diodes 4 are respectively connected to the output lines 2-1 and 2-2 of the input stages of the preamplifiers 3-1 and 3-2.
-1, 4-2 and resistors 5-1 and 5-2 are connected to a test signal applying circuit, and the common connection point of the two resistors 5-1 and 5-2 is connected to the solid-state image sensor 1 A test signal input terminal 7 is connected via a test ON / OFF switch 6 controlled by a blanking pulse of a video signal. The diodes 4-1 and 4-2 are for reverse biasing when the test is OFF to cut the test signal system, and the resistor 5-
Reference numerals 1 and 5-2 are for converting a test voltage signal into a current signal. 9-1 and 9-2 are amplifiers for adjusting the output signals of the preamplifiers 3-1 and 3-2 to appropriate levels, and 10-1 and 10-2 are for adjusting the gain of the amplifiers 9-1 and 9-2. The reference numeral 11 is a channel changeover switch for switching and outputting the output signal of the output line of each channel to make it a single-line output, and the reference numeral 12 is an output terminal for the single-line output signal.

Next, the operation of the conventional image pickup apparatus thus constructed will be described. When the image pickup operation is started, video signals are output from the solid-state image pickup device 1 to the output lines 2-1 and 2-2 as channel 1 signals and channel 2 signals, respectively. At this time, the test ON / OFF switch 6 is switched to the test ON side during the blanking period in which the fixed pattern noise of the video signal does not occur, and the test signal is switched to the resistors 5-1 and 5-2 and the diodes 4-1 and 4. It is added to each output line 2-1 and 2-2 via -2. The composite signal of the video signal from the solid-state image pickup device 1 and the added test signal is converted from current to voltage by the preamplifiers 3-1 and 3-2 and sent to the amplifiers 9-1 and 9-2 at the next stage.

The signal of channel 1 is amplified by the amplifier 9-1 whose gain is adjusted based on the volume 10-1 and sent to the channel changeover switch 11. On the other hand, the signal of channel 2 is adjusted so that the reference level of the test signal portion of each channel output signal of each amplifier 9-1, 9-2 becomes the same.
It is amplified by the amplifier 9-2 whose gain is adjusted by -2, and is similarly sent to the channel changeover switch 11. The output signals of the respective channels whose signal output levels are input to the channel changeover switch 11 are switched and selected by the channel changeover pulse, are combined into a one-line output signal, and are sent to the output terminal 12. .

As another conventional example, as shown in FIG. 5, the amplifier 9-2 of the channel 2 of the conventional example shown in FIG. 4 is not provided with a gain adjusting volume, but instead is provided in the channel 2. Is provided with a gain adjusting circuit 21, and each channel 1 and 2 further includes a test signal level detecting circuit 22-1, which detects a reference level of a test signal portion of the output signal amplified by the amplifiers 9-1 and 9-2. 22-2 is provided, the level detection signals of these detection circuits are input to the comparator 23, and the gain adjustment circuit 21 is controlled by the output of the comparator 23.

These conventionally proposed image pickup devices are
In each case, a test signal is input to each output line of the image sensor, that is, the input stage of the preamplifier, the output signal level of the signal processing system of each channel is compared by this, and the difference is detected. The amplification factor of the channel signal processing system is manually or automatically adjusted to make the amplification factor of each channel signal processing system uniform.

[0008]

By the way, in the image pickup apparatus provided with the above-mentioned signal processing unit proposed in the related art, a test signal must be supplied to the input of the amplifier, that is, the output of the image pickup element. There is such a problem. (A) The applicable range is limited to an image pickup device having a sufficiently high output impedance (current output type), and C
It cannot be applied to a voltage output type image pickup device such as a CD. (B) When supplying a test signal to the input of the preamplifier, it is necessary to connect a large number of elements such as diodes and resistors, and it is difficult to remove noise induced from these elements. (C) Furthermore, the diode necessary for supplying the above test signal,
Variations in characteristics such as resistance are directly reflected in variations in the amplifier.

The present invention has been made in order to solve the above-mentioned problems in an image pickup apparatus having a conventional signal processing unit, and has a simple structure so that the output signals of the respective channels can be accurately and uniformly distributed. It is an object of the present invention to provide an imaging device equipped with a signal processing unit capable of automatically adjusting the amplification factor of a channel.

[0010]

In order to solve the above problems, the present invention uses a multi-channel read-out type image pickup device, and after individually amplifying multi-channel signals obtained from the image pickup device. In an image pickup apparatus including a signal processing unit configured to form a video signal by combining, a means for temporarily irradiating the light receiving surface of the image pickup element with a substantially uniform amount of light, and the temporary light Means for amplifying a signal obtained from the image pickup device for each channel at the time of irradiation, means for comparing the levels of the amplified signals of the respective channels, and based on the output signal from the comparing means, the amplification means for the respective channels The present invention is configured by providing means for automatically adjusting the substantial amplification factor to be uniform for each channel, and means for holding the adjusted state of the automatic adjusting means.

In the image pickup device constructed as described above,
First, in the preparatory stage of capturing an image of a subject, the light receiving surface of the image sensor is temporarily irradiated with a uniform amount of light, and the output signal levels of the amplification means of each channel at this time are compared, and the output signal level of each channel is compared. The amplification factor of each amplification means is automatically adjusted until the values become uniform. The holding means of the automatic adjustment means continues to control the amplification factor of the amplification means of each channel even after the automatic adjustment period of the amplification means.

Even when the imaging preparation stage is completed and the object is actually imaged, the amplification factor of the amplification means of each channel is controlled so as to have a uniform output signal level with respect to a uniform amount of light incident on the image sensor. Therefore, it is possible to correct variations including characteristic variations between channels such as photoelectric conversion characteristics, charge transfer characteristics, and capacitance characteristics inside the image pickup element, and there is a high S / N ratio without vertical stripes on the screen. A subject image can be obtained.

[0013]

EXAMPLES Next, examples will be described. FIG. 1 is a block diagram showing an embodiment of an image pickup apparatus according to the present invention. In the figure, 101 is a solid-state image sensor for converting a subject image into an electric signal or an image sensor having a similar function, and outputs signals simultaneously to the output terminals 102-1 and 102-2 of the two channels. Has become. 103-1, 1
03-2 is a preamplifier that amplifies the signals of the two channels from the image pickup device 101, and 104-1 and 104-2 are for amplifying the output signals of the preamplifiers 103-1 and 103-2 to appropriate levels. And 105 is a variable resistor for adjusting the amplification factor of the amplifier 104-1. Reference numeral 106 denotes a channel changeover switch that switches and outputs the output signal of the output line of each channel and outputs it as a single line, and 107 is an output terminal of the single line output signal. 108-1, 108-2 are amplifiers 104-1, 104-2
Is an output signal level detector for detecting the output signal level of each. 109 is the output signal level detector 108-
1 and 108-2 are comparators for comparing the signal levels detected by the comparators 109. The output signal of the comparator 109 is the register 11
It is held at 0 and the output of this register 110
A gain adjusting circuit 111 provided between 104-2 and the channel changeover switch 106 is adjusted.

Reference numeral 115 denotes an image forming optical system, which is a lens 115-1 for forming a subject image on the light receiving surface of the image pickup element 101, and irradiates the light receiving surface of the image pickup element 101 with a uniform amount of light in the image pickup preparation stage. It is composed of an LED 115-2 and the like. A switch 116 forms a trigger for starting the imaging preparation stage. 117 is a timing pulse generation circuit, which is a switch
Receiving the trigger signal formed at 116, various timing pulses necessary for the imaging preparation stage are generated. And
Image sensor 101 in which LED 115-2 irradiates a uniform amount of light
The area on the light receiving surface of, that is, a two-dimensional area in which the amount of light emitted to the pixels corresponding to each channel is highly uniform, the generation timing of the pulse generated by the timing pulse generation circuit 117 is specified, It can be selected by driving the LED 115-2 via the LED driving circuit 118. The generation timing of this pulse may be once in one frame (1/30 seconds) or may be plural times.
Each time this pulse is generated, the signal levels of the respective channels are compared with each other, and the contents of the register 110 are updated as a result.

Next, the operation of the embodiment thus configured will be described. First, switch 11 for starting the imaging preparation stage
When 6 is turned on, the timing pulse generating circuit 117 causes the dark fixed pattern noise removing means (not shown) and the output signal level detectors 108-1 and 108-2 of each channel.
Generates the timing pulse necessary for the operation of. Further, the LED drive circuit 118 operates for a period determined by the timing pulse to cause the LED 115-2 to emit light. LE
The light emitted from D115-2 illuminates the light receiving surface of the image pickup element 101 substantially uniformly. As a result, the two-channel output signals obtained from the image sensor 101 are output from the output terminals 102-1 and 102-2 via the preamplifiers 103-1 and 103-2 and the amplifiers 104-1 and 104-2, respectively, and output signal level Detector 108-1, 108-
It is supplied to 2 and generates digital signals according to the input signal level. These digital signals are the comparator
The signal is input to 109, a signal level difference is detected, and a signal corresponding to the level difference is supplied to the register 110. The signal content of the register 110 is updated by adding / subtracting the content of the comparator 109 each time a level difference output is generated from the comparator 109.

The gain adjusting circuit 111 adjusts the gain according to the signal contents of the register 110. Amplifier 104-1
If the output signal level of the output signal of 1 is equal to the output signal level of the gain adjusting circuit 111, the output of the comparator 109 becomes zero. When the output of the comparator 109 becomes zero or less than the allowable value, the operation stop signal is supplied to the timing pulse generation circuit 117,
The preparation for imaging is completed.

When the series of operations described above is completed, variations in the characteristics of the respective channels of the image sensor 101 having two-channel output, including the characteristics of the image sensor 101, are completely corrected, so that vertical stripes appear. It is possible to obtain a high-quality subject image.

In the above embodiment, the signal processing after the output signal level detectors 108-1 and 108-2 of each channel is such that the digital signal is processed, but the present invention is not limited to this. Alternatively, the signal processing can be performed by analog signal processing or a mixed analog / digital configuration.

Further, although the LED 115-2 is used as a means for temporarily irradiating the light receiving surface of the image pickup device 101 with a uniform light amount, the means is not limited to this, and for example, FIG. ), (B), a means for scattering light, for example, a diffuser plate 115-3 is disposed in a part of the imaging optical system 115, that is, in front of or behind the lens 115-1 to provide extreme defocusing. The same purpose can be achieved by setting the state.

Furthermore, in the above-mentioned embodiment, the one using a two-channel image sensor as the multi-channel image sensor is shown. However, the present invention is applicable to an image pickup apparatus using a multi-channel read type image sensor of three or more channels. Of course, this is also applicable, and in this case, the contents of the registers controlling the amplification factors of the multi-channel signal processing system are simultaneously updated by the generation of the timing pulse. .

[0021]

As described above on the basis of the embodiments,
According to the present invention, when the output signals of the image pickup devices having multi-channel outputs are combined to form a video signal, it is possible to adjust the variation of the signal processing unit including the variation of the characteristics of the image pickup devices between channels. There is no difference in signal level between them, and the image quality can be significantly improved.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of an image pickup apparatus according to the present invention.

FIG. 2 is a diagram showing another configuration example of the image forming optical system of the embodiment shown in FIG.

FIG. 3 is a diagram showing a signal output mode of a conventional multi-channel readout image sensor.

FIG. 4 is a block diagram showing a configuration example of a conventional image pickup apparatus in which amplitude noise is reduced.

FIG. 5 is a block diagram showing another example of the configuration of a conventional image pickup apparatus in which amplitude noise is reduced.

[Explanation of symbols]

 101 Image sensor 102-1, 102-2 Output terminal 103-1, 103-2 Preamplifier 104-1, 104-2 Amplifier 105 Variable resistor 106 Channel selection switch 107 Single line output signal output terminal 108-1, 108-2 Output signal level detector 109 Comparator 110 Signal level control register 111 Gain adjusting circuit 115 Imaging optical system 115-1 Lens 115-2 LED 115-3 Diffusing plate 116 Imaging preparation start switch 117 Timing pulse generating circuit 118 LED driving circuit

Claims (3)

[Claims] 1. An image pickup device using a multi-channel read-out type image pickup device, comprising a signal processing unit for individually amplifying and then combining multi-channel signals obtained from the image pickup device to form a video signal. In the apparatus, means for temporarily irradiating the light-receiving surface of the image pickup device with a substantially uniform amount of light; means for amplifying a signal obtained from the image pickup device at the time of the temporary light irradiation for each channel; Means for comparing the signal levels of the respective channels, and means for automatically adjusting the substantial amplification factor of the amplifying means of the respective channels so as to make them uniform on the basis of the output signal from the comparing means. An image pickup apparatus comprising: a means for holding the adjusted state of the automatic adjustment means. 2. The means for irradiating the light-receiving surface of the image pickup device with a substantially uniform amount of light is composed of an LED configured to irradiate the light-receiving surface of the image pickup device uniformly. The image pickup apparatus according to claim 1. 3. A light diffusing plate inserted in an optical path of an image forming optical system as a means for irradiating a light receiving surface of the image pickup device with a light having a substantially uniform light amount. Imaging device.