JPH08125924A - Solid-state image pickup device and line sensor camera - Google Patents

Abstract

PURPOSE: To improve the gradation of a relatively dark part by changing the number of bits for A/D conversion for respective picture elements and performing output for the photographing of an object whose dynamic range is wide. CONSTITUTION: This device is provided with a lens group 101 for image-forming optical information on a prescribed image forming surface and a line sensor 103 for converting the optical information of the image forming surface 102 to electric information. A line sensor driver 104 electrically drives the line sensor 103 by the instruction of a system controller 105, a scanning means 114 lets the line sensor 103 scan within the image forming surface and the system controller 105 controls the line sensor driver 104 and the scanning means 114 and adjusts exposure time by the multiple of 2. An A/D converter 108 converts sampled and held video signals to digital images. When the number of output bits of an A/D converter bit number selection means 116 exceeds the number of upper limit bits of the A/D converter, the photographing is performed for plural times while changing the exposure time and the image data of a large number of bits are prepared.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the gradation of a solid-state image pickup device or a line sensor camera using a one-dimensional image pickup device or a solid-state image pickup device, and more particularly to expanding its dynamic range.

[0002]

2. Description of the Related Art Conventionally, as a product using a CCD or MOS type line sensor, there are a copying machine, a facsimile and a scanner. These are designed to image flat objects such as paper and film.The light from a light source built into the image pickup device that does not change with time is applied to the object, and the amount of transmitted or reflected light is read by a line sensor. Has become. Further, the mechanism is such that the entire image is two-dimensionally recognized by moving the object vertically with respect to the line sensor.

Further, the line sensor camera is used as a part of FA (Factory Automation), and may be mainly intended to provide a manager with a material for judging a non-defective product or a defective product on a production line. The feature is that a three-dimensional object is targeted, and the light source is often arranged so as to be irradiated from the outside.

FIG. 9 shows a configuration example of the line sensor camera. In the figure, 201 is a lens group for forming an image of light from an object such as a drawing or a product on a line sensor surface of a photoelectric conversion unit, which will be described later, and 202 is an electric signal representing incident light imaged by the lens group 201. It is a line sensor for converting to n. Here, it is assumed that it is composed of photodiodes in which n pieces are arranged in one row. A video amplifier 203 amplifies the video signal output from the line sensor 202 to an appropriate signal level. 204 is a sample
A hold circuit for converting the output signal pulse of each photodiode from the video amplifier 203 into a continuous output signal. Reference numeral 205 is a signal processing circuit for converting the output signal from the sample and hold circuit 204 into a standard video signal.

Reference numeral 206 denotes a timing controller for controlling the entire line sensor camera, which can be realized by a gate array or a general-purpose microprocessor. A line sensor driver 207 drives the line sensor 202. Reference numeral 208 is an exposure time selection member for selecting the exposure time for the line sensor 202, and 209 is a main switch for supplying power to each part of the line sensor camera.

Next, the operation of the line sensor camera in FIG. 9 will be described with reference to the flowchart in FIG.

First, the main switch 209 of the main body of the line sensor camera is turned on (step 301). Then, the timing controller 206 scans / detects the state of the exposure time selection member 208 and instructs the line sensor driver 207 to perform photoelectric conversion from the memory built in the timing controller 206 at the pre-specified exposure time. Set (step 302). The line sensor driver 207 is the timing controller 206 described above.
In response to the command from the line sensor 202, the line sensor 202 is driven, and the line sensor 202 converts the imaged image information into time-series electrical information and outputs it to the video amplifier 203 (step 303). The video amplifier 203 is the line sensor 20.
The weak signal from 2 is amplified (step 304).

Next, the sample and hold circuit 204
The time-sequential pulse signal output from the video amplifier 203 is sampled and held at the timing from the timing controller 206, and converted into a continuous output signal (step 305). The image information is converted into a standard video signal by the signal processing circuit 205 and guided to the TV monitor (step 306). Then, the image photographer checks the TV monitor, and when the exposure time is long and the signal level is high and whitish, or when the exposure time is short and the signal level is low and blackish, the exposure time Is reset, the process returns to step 302, and the same work is repeated again (step 307). By repeating this operation by moving the object and repeating scanning, a two-dimensional image on the screen can be obtained.

Through the above operation, in the case of product inspection during assembly work, a two-dimensional image is viewed on a TV monitor to set an optimum exposure time and confirm the correct operation of the line sensor camera body. ing.

Although the above-described line sensor camera shows an example in which the subject moves, there is also a line sensor camera in which the subject is fixed and the line sensor of the image pickup device is moved. On the other hand, high-definition images can be taken. Such a line sensor camera may be used by a designer or a cameraman as one of direct input devices to a computer.

[0011]

However, in the conventional example, the dynamic range of the image information signal is not sufficient, and the operability of the line sensor camera is inconvenient, and improvement is desired. In particular, photographing a subject having a wide dynamic range (photographing under natural light) requires an A / D converter with a large number of bits, resulting in an expensive system.

[0012]

In view of the above points, the present invention provides an A / D converter for converting an analog image signal into a digital image signal when photographing a subject having a wide dynamic range. In a line sensor camera equipped with A / D converter bit number selection means, the output (N bit) of the A / D converter bit number selection means is A / D.
When the upper limit number of bits (Mbit) of the D converter is exceeded (N
≧ M), and a line sensor camera in which data is input a predetermined number of bits (M bit) by photographing a plurality of times while changing the exposure time. In addition, the change in the exposure time to the line sensor is 2 times the exposure time at the time of the first image input.
^(MN) times, a line sensor camera characterized by comprising an area setting means for setting an area requiring multiple exposure shooting from the output of the dynamic range detection means, and shooting again only the area of the area setting means It is provided.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to the drawings. In the block diagram shown in FIG. 1, reference numeral 100 denotes a main power switch for supplying power to the present line sensor camera. Reference numeral 101 denotes a lens group for forming a subject image on the image forming surface of 102. 103 is an image plane 102
Is a line sensor of a one-dimensional image sensor arranged inside,
For example, there are a CCD line sensor and a M0S type transistor line sensor. A line sensor driver 104 electrically drives the line sensor 103 in accordance with a command from a system controller 105 described later. That is, the line sensor driver 104 causes the line sensor 103 to output image information dot by dot by the trigger of the system controller 105.

Further, 105 is a system controller, which is a microcomputer having a built-in RAM and ROM. The operation is to control the function of each block in this embodiment to obtain a two-dimensional image.
A video amplifier 106 amplifies the output of the line sensor 103 to an appropriate size. A sample and hold circuit 107 converts the pulsed output from the video amplifier 106 into a continuous smooth signal. Reference numeral 108 denotes A / D conversion means for converting the analog image signal of the sample and hold circuit 107 into a digital image signal, which is exemplified here as an A / D converter having a resolution of N = 8 bits. A memory A 109 is a storage unit for temporarily storing the digital image signal data.

A shading correction circuit 110 performs shading correction after the image data for one line is stored in the memory A109. Reference numeral 111 denotes a gamma correction circuit for performing gamma correction on image data.
Since the shading correction circuit 110 and the gamma correction circuit 111 are known techniques, detailed description thereof will be omitted. 11
2 is a shading correction circuit 110 and a gamma correction circuit 1
11 is a storage unit for temporarily storing the image data of one line after the correction, and a memory B for distinguishing from 109.
And

Reference numeral 113 denotes a communication circuit means for transferring the image data stored in the memory B112 to an external digital device or for communicating with an external digital device. For example, a SCSI circuit or RS-232C.
Circuit. Reference numeral 114 designates the line sensor 103 as the image plane 10
It is a scanning means for mechanically moving within the unit 2, and is controlled by a command of the system controller 105. That is, in this embodiment, if the line sensor 103 is arranged so as to be able to output a line along the y-axis at one time, the scanning means 114 will move the line sensor 103 along the x-axis.

The mechanism of the scanning means 114 is shown in FIG. FIG. 2 shows the appearance and a part of the inside of the line sensor camera. Reference numeral 701 denotes a stepping motor, and a housing 703 of the line sensor 102 via a gear 702.
Are moved along the guide bar 704. Since the line sensor 103 and the housing 703 are fixed by screws, the line sensor 103 moves along the guide bar 704. The scanning unit 114 also includes a driver circuit for driving the stepping motor 701 according to the driving direction from the system controller 105 and a clock signal.

Further, 115 is an end detecting means for detecting whether or not the line sensor 103 is at the scanning end,
It can be realized with a photo interrupter. Reference numeral 116 is a bit number selecting means of the A / D converter, which is a digital value input member such as a rotary encoder or a DIP switch. 117 is a release button for permitting shooting,
Shooting is started by using this release signal as a trigger.

Next, a flow chart showing the operation / action of the present invention will be described with reference to FIG. First, the main power supply of the main body of the line sensor camera is turned on (step 40
0), the system controller 105 performs hardware initialization. The system controller 105 detects the output of the edge detecting means 115 and determines whether the position of the line sensor 103 is at the scanning edge on the X axis (step 401). If the line sensor 103 is arranged at the scanning end, the process proceeds to step 403, and if not, the process proceeds to step 402. In step 402, since the line sensor 103 is not at the end, the system controller 1
Reference numeral 05 outputs one clock signal to the scanning means 114 together with the direction of the scanning end to move the line sensor (step 4).
02). Then, the process returns to step 401.

If the line sensor 103 is at the scanning end, this position is set as the reference position. Next, the system controller 105 sets shooting conditions (step 4).
03). In other words, the thinning-out degree / exposure time T of the imaging area / solid-state imaging device of the line sensor is set to
05 is stored in the built-in RAM. This may be input to the system controller 105 from an external digital device via the communication circuit 113.

Further, the system controller 105 detects the state of the bit number selection means 116 and determines the input bit number M of the A / D converter as R in the system controller 105.
Store in AM (step 404). The system controller 105 checks the state of the release button 117 (step 405) and loops from step 403 to step 405 and waits until the release button 117 is pressed.
During this period, the photographer sets the composition of the subject. If the release button 117 is pressed, the process proceeds to step 406 to start shooting.

Then, the system controller 105
Sends a command to the line sensor driver 104 to perform T-time exposure, and exposes a part of the subject image on the image plane 102 (step 406). After the T-time exposure, transfer of the subject information, which has been converted into an optical / electrical signal, as a time-series image information signal dot by dot is started from the line sensor 103 (step 407). The video amplifier 106 amplifies the image information signal from the line sensor 103 to an appropriate size for the subsequent stage (step 408). The sample and hold circuit 107 converts the pulsed signal from the line sensor 103 into a smooth image information signal (step 40).
9).

Next, the A / D conversion resolution N of the A / D converter 108 and the A / D converter bit number selection value M from the bit number selecting means 116 are compared (step 410), and N ≧
If M is true, jump to step 411, and if false, jump to step 412. If N is larger, image data is created by one exposure routine (step 41).
1). If M is larger, image data with a larger number of bits is created by a plurality of exposure routines (step 41).
2).

Next, 1 stored in the memory A 109
The shading correction circuit 110 performs shading correction on the digital image data for the line (step 413). Further, the shading correction circuit 110
In response to the result, the gamma correction circuit 111 performs gamma correction on the image data (step 414). The result of gamma correction is stored in the memory B 112 for one line (step 415).

Subsequently, the system controller 105 communicates with an external digital device to transfer one line of image data from the memory B112 to the external digital device (step 416). At this time it is in the shooting area,
At the same time, the minimum data number that satisfies the condition of the thinning degree of the image data is also transferred.

Next, after transferring all the data, the system controller 105 calculates the next image taking-in position from the data of the thinning degree of the image data, and the scanning means 114.
The line sensor is moved on the X-axis via (step 417). The system controller 105 determines whether or not the position of the line sensor 102 is out of the designated photographing area based on the result of the scanning edge detecting means 115 and the movement amount of the line sensor 103 (step 418). If it is outside the area, the process jumps to step 401. If it is not outside the area, the process proceeds to step 406 to repeat the photographing.

Since steps 411 and 412 are an important part of the present invention, they will be described with reference to the flow charts shown in FIGS. 4 and 5, respectively.

First, in FIG. 4, since N ≧ M, 1
Enter the exposure routine (step 411). Then, the resolution of the A / D converter 108 is set to M bits,
The output of the sample and hold circuit 107 is analog-to-digital converted with M bits (step 501). And
Image data digitally converted to M bits is stored in the memory A.
It is temporarily stored in 109 (step 502). When the image data for one line is stored, the process proceeds to step 413 (step 503).

The multiple exposure routine (step 412) in the case of N <M in FIG. 5 will be described. Here, in order to simplify the description, the description will be limited to two exposures. First, the resolution of the A / D converter 108 is set to N bits, and the output of the sample and hold circuit 107 is A / D converted with N bits (step 601). Then, the digitally converted image data is stored in the memory A10.
9 is temporarily stored (step 602). The system controller 105 checks whether or not the stored image data for each image data is less than $ FF * 2 ^(NM) (step 603). If the image data is small, the process proceeds to step 604. If the image data is large, the process proceeds to step 605. This is done to check if the sensor output is small and there is data that requires multiple exposures. Here, $ FF represents the maximum value of N (= 8) bits.
If the data is less than $ FF * 2 ^(NM) , the address of the pixel is temporarily stored in Add (i) (step 604).

Next, the data is multiplied by 2 ^(MN) (step 605). The new data is stored in the same address of the memory A 109 (step 606). It is determined whether steps 603 to 606 have been executed for the image data for one line (step 607). If not executed, the process returns to step 603. Step 6 if running
Go to 08. The system controller 105 issues a command for the T * 2 ^(MN) time exposure to the line sensor driver 104, and photographs data with different exposure times at the same position (step 608). Similar to step 407, the line sensor 103 outputs a time series electric signal including subject information (step 609).

Next, as in step 408, the video amplifier 106 amplifies the image data (step 61).
0). Similar to step 409, the sample and hold circuit 107 samples and holds the image data to form a smooth signal (step 611). The A / D converter 108 performs A / D conversion with N bits (step 612). The system controller 105 uses the address Ad obtained in step 604.
Only the data of d (i) is permitted to be written in the memory A 109, and the image data is rewritten (step 613).
After performing the processing for one line of data, the process proceeds to the shading correction of step 413 (step 614).

With the above flow as N = 8 and M = 12, 12
FIG. 6 is a diagram showing a process of forming bit image data. FIG. 6A shows the memory A1 in step 602.
The image data in 09 is plotted in a graph in which the horizontal axis represents the pixel position of the line sensor 103 and the vertical axis represents the image data level. Step 6 in this image data
It can be seen that there is image data of $ FF * 2 ^(NM) = $ 0F or less checked in 03. Step 60
FIG. 6B shows a state in which those addresses are stored at 4 and 605 and the image data is multiplied by 2 ^(MN) = 16. In this case, the digital value input as T * 2 ^{(M− N)} = 16T is shown in FIG. 6 (c). As a result, Add
FIG. 6D shows image data of M = 12 bits after rewriting the address of (i). Thus, it can be seen that the gradation of the rewritten portion is improved.

Further, in order to know later how many bits the image information to be photographed is, the steps 403 and 40 in FIG.
Prepare to add the shooting conditions obtained in step 4 to the image data. For example, as shown in FIG. 7A, it may be provided as a file separately from the image data, or as shown in FIG. 7B, the first few bytes of the image data are used. Alternatively, FIG.
As shown in (c), it may be recorded by using the empty bits of the image data. For example, when M = 12 bits, it becomes 2 bytes (16 bits) of data.
The fact that there is a space in the upper 4 bits is used. Further, as shown in FIG. 8, first, a declaration bit for using an empty area is provided in the first image data, and in the next image data, the number of upper bits to be used for storing the photographing condition data is written, and the next image data is written. Indicates the number of shooting condition data to be sent after this. After that, shooting conditions such as A / D conversion bit numbers N and M, first exposure time, second exposure time, number of image data, and F number are entered. The photographing condition data is recorded as described above and transmitted to the external digital device.

[0034]

As described above, by providing a system in which the number of conversion bits of the A / D converter can be set, when the number of bits is small, the gradation is short and when the number of bits is large, the gradation is excellent. Image data can be created. In particular, it is possible to obtain gradation of a relatively dark part in a subject having a wide dynamic range. When performing multiple exposures, by making the exposure time 2 ^(MN) times the initial exposure time, it is possible to easily convert multi-bit data, and it is possible to realize it in a short time because only necessary areas are converted.

Further, although the gradation of the bright part is deteriorated,
Due to the characteristics of the human eye, it does not look so discomforting, so it is possible to capture images with excellent gradation using a simple and inexpensive system. Furthermore, by adding shooting conditions to the image data, it becomes easier to handle the image data later.

[Brief description of drawings]

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

FIG. 2 is an external view of a line sensor camera according to the present invention,
It is a partial internal layout.

FIG. 3 is a flow chart showing the operation of an embodiment according to the present invention.

FIG. 4 is a flowchart of a single exposure routine according to the present invention.

FIG. 5 is a flowchart of a multiple exposure routine according to the present invention.

FIG. 6 is a diagram for creating image data of a multiple exposure routine according to the present invention.

FIG. 7 is a memory layout diagram illustrating a recording system of shooting condition data of the line sensor camera according to the present invention.

FIG. 8 is a format diagram for explaining a recording method using an empty bit of shooting condition data of the line sensor camera according to the present invention.

FIG. 9 is a block diagram showing a configuration of a conventional line sensor camera.

FIG. 10 is a flowchart illustrating an operation of a conventional line sensor camera.

[Explanation of symbols]

 100, 209 Main switch 101, 201 Lens group 103, 202 Line sensor 104, 207 Line sensor driver 105 System controller 106, 203 Video amplifier 107, 204 Sample and hold circuit 108 A / D converter 109, 112 Memory 110 Shading correction circuit 111 gamma correction circuit 206 timing controller

Claims (10)

[Claims] 1. A lens group for forming optical information on a predetermined image forming plane, a plurality of solid-state image pickup devices for converting optical information of the image forming plane into electrical information, and a plurality of solid-state image pickup devices. Exposure amount adjusting means for adjusting the exposure time, scanning means for scanning the plurality of solid-state imaging devices with respect to the image plane, and analog output signals of the plurality of solid-state imaging devices into digital data signals. A solid-state imaging device comprising: an A / D converter for conversion; and an A / D converter bit number selection means for selecting the bit number of the A / D converter. 2. The exposure when the output (N bit) of the A / D converter bit number selection means exceeds a predetermined upper limit bit number (M bit) of the A / D converter (N ≧ M). Shooting multiple times with different times, the specified number of bits (M b
The solid-state imaging device according to claim 1, wherein the image data is created by (it). 3. The solid-state imaging device according to claim 2, wherein the change of the exposure time is 2 ^(MN) times the initial exposure time. 4. The A / D converter bit number selecting means includes a dynamic range detecting means for detecting a dynamic range of the digital data signal, and an area where multiple exposure photographing is required from an output of the dynamic range detecting means. 2. The solid-state imaging device according to claim 1, further comprising: an area setting unit that sets the image capturing area, wherein only the area of the area setting unit is imaged again. 5. The solid-state imaging device according to claim 1, further comprising: a condition that the exposure time and the number of bits selected by the A / D converter are recorded together with image data of an output signal of the solid-state imaging device. A solid-state imaging device comprising means. 6. A lens group for forming optical information on a predetermined image plane, a one-dimensional image sensor for converting optical information on the image plane into electrical information, and the one-dimensional image sensor. Exposure amount adjusting means for adjusting the exposure time of the one-dimensional image sensor, scanning means for scanning the one-dimensional image sensor within the image plane, and A / D converting an analog output signal of the one-dimensional image sensor into a digital signal. A line including a conversion unit, a control unit for controlling the scanning unit with respect to the output signal of the one-dimensional image sensor to obtain a two-dimensional image of the image plane, and a communication unit for communicating with other digital equipment. A line sensor camera, comprising: an A / D converter bit number selecting means for selecting a bit number of the A / D converting means. 7. The exposure if the output (N bit) of the A / D converter bit number selection means exceeds a predetermined upper limit bit number (M bit) of the A / D conversion means (N ≧ M). Change the time and take multiple shots to get a certain number of bits (M
7. The line sensor camera according to claim 6, wherein the image data is created using a bit). 8. The line sensor camera according to claim 7, wherein the change of the exposure time is 2 ^(MN) times the initial exposure time. 9. The A / D converter bit number selecting means includes a dynamic range detecting means for detecting a dynamic range of an output signal of the one-dimensional image pickup device, and a plurality of exposure photographing operations from the output of the dynamic range detecting means. 9. The line sensor camera according to claim 8, further comprising: an area setting unit that sets an area necessary for the line sensor camera, wherein only the area of the area setting unit is imaged again. 10. The line sensor according to claim 6, wherein the conditions such as the exposure time and the number of bits selected by the A / D converter are recorded together with the image data of the output signal of the one-dimensional image sensor. A line sensor camera characterized in that