JPH0628454B2 - Back focus adjustment method for solid-state image sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the present invention will be described in the following order.

A. Industrial application fields B. SUMMARY OF THE INVENTION C. Conventional Technology D. Problems to be Solved by the Invention E. Means for Solving Problems F. Action G. Example G-1 Configuration of registration adjusting device (see FIG. 1) G-2 Configuration of test chart for registration measurement (see FIGS. 2 and 3) G-3 Procedure of adjusting operation (see FIG. 4) ) H. Effect of Invention A. The present invention relates to a charge coupled device (CCD) used as an image sensor in a solid-state imaging device.
The present invention relates to a back focus adjustment method for a solid-state image sensor, which is applied when performing so-called registration adjustment or the like in which the solid-state image sensor is placed at a predetermined position of the image pickup optical system such as e).

B. SUMMARY OF THE INVENTION The present invention has a predetermined relationship with the pixel pitch of the solid-state imaging device when performing so-called registration adjustment or the like in which the solid-state imaging device used in the solid-state imaging device is arranged at a predetermined position of the imaging optical system. Regarding the imaging output obtained by imaging a repeating pattern that repeats light and shade with a repeating pitch through the imaging lens by the solid-state imaging device, the repeating pitch of the repeating pattern corresponding to the center of the image and the pixel pitch of the solid-state imaging device. By detecting the beat component based on the difference between the solid-state image sensor and moving and fixing the solid-state image sensor so that the detected output becomes maximum, back focus adjustment of the solid-state image sensor can be performed with high accuracy by a simple operation. It was done like this.

C. 2. Description of the Related Art Generally, in a color image pickup device, image pickup light is separated into a plurality of color components by a color separation system, and a subject image of each color component is obtained by a solid-state image sensor such as CCD or an image pickup tube. A standard color television signal of the NTSC system or the like is formed and output from each image output. In a color image pickup apparatus using a plurality of image sensors, it is necessary to surely maintain a state in which subject images of respective color components picked up by the image sensors are superposed, that is, a so-called registration adjustment is accurately performed.

In a conventional so-called three-tube color video camera, a three-color separation prism of a color separation system and three image pickup tubes are mechanically attached to a housing formed by die casting or the like, and an output signal obtained by photographing a test chart or the like is used. The registration of each image pickup tube is adjusted by mechanically adjusting the position and further finely adjusting the image pickup screen position using the deflection system of the image pickup tube.

For such a three-tube color video camera, CC
In a solid-state color image pickup device that uses a solid-state image pickup device such as D as an image sensor, it is not possible to electrically adjust the image pickup screen position like an image pickup tube. Therefore, in each solid-state image sensor that picks up a subject image of each color component, A holder made of iron or the like is joined, and a holder is also joined to each light emitting part of the color separation prism of the color separation system.
For each image sensor, the adjustment direction is indicated by the arrow in Fig. 5. (1) Horizontal center (arrow ± X direction) adjustment (2) Vertical center (arrow ± Y direction) adjustment ( 3) Back focus (arrow ± Z direction) adjustment (4) Horizontal tilt (arrow ± RX direction) adjustment (5) Vertical tilt (arrow ± RY direction) adjustment (6) Rotation (arrow ± RZ direction) adjustment After adjusting the registration in the 6-axis directions, the holders are heat-welded by soldering or the like to attach and fix the solid-state image sensors to the emission surfaces of the color separation prism.

D. Problems to be Solved by the Invention In general, a solid-state image sensor such as a CCD cannot adjust the position of an electric image-pickup screen like an image pickup tube. Therefore, in a color image pickup apparatus using a plurality of solid-state image sensors, Therefore, it is necessary to maintain the registration of each image sensor with extremely high accuracy. Particularly, in the solid-state color image pickup device which adopts the so-called spatial pixel shift method to achieve high resolution, the above-mentioned ± X direction, arrow ± Y direction, ± Z direction, ± RX, ± RY direction and ± RZ It is necessary to secure a registration on the order of 1 μm in the six axial directions, and conventionally, it took a lot of time and effort to adjust the registration.

According to the method of the present invention, in performing the registration adjustment in the 6-axis direction, the registration adjustment in the Z-axis direction, that is, the back focus adjustment of the solid-state imaging device can be performed with high accuracy by a simple operation. To aim.

E. Means for Solving Problems In order to solve the above-mentioned problems, a solid-state image sensor back focus adjustment method according to the present invention adjusts the back focus of a plurality of solid-state image sensors that capture the same image. , A repeating pattern in which light and shade are repeated in the horizontal or vertical direction at least at a position corresponding to the center of the image pickup screen of the solid-state image sensor, and the repeating pitch has a predetermined relationship with the horizontal or vertical pixel pitch of the solid-state image sensor. Is captured by each solid-state image sensor through the image-capturing lens, and the difference between the pixel pitch and the repetition pitch included in each image-capture output of the repeating pattern corresponding to the central portion of the image by each solid-state image sensor. The beat component based on the above is detected, and each of the solid-state image pickup devices is moved in the optical axis direction of the image pickup lens to detect the beat component. Each of the solid-state image pickup devices is fixed at a position where the force is maximized.

F. In the method of adjusting the back focus of the solid-state image sensor according to the present invention, the solid-state image sensor has a repeating pattern in which light and shade are repeated in the horizontal or vertical direction at least at a position corresponding to the center of the imaging screen of the solid-state image sensor. An image pickup output obtained by picking up an image having a predetermined relationship with the pixel pitch in the horizontal or vertical direction of the element through the image pickup lens by the solid-state image pickup element is based on the difference between the pixel pitch and the repetition pitch. Contains beet components.
The amplitude of the beat component changes depending on the back focus of the imaging lens, that is, the registration error in the ± Z directions described above, and becomes maximum at the just focus. For each of the solid-state image pickup devices, an operation of detecting the beat component and moving and fixing the solid-state image pickup device so that the detected output becomes maximum with respect to the image pickup output of the repeating pattern corresponding to the central portion of the image. By doing
The back focus of a plurality of solid-state image pickup devices that pick up the same image is adjusted.

G. Embodiment An embodiment of the back focus adjusting method for a solid-state image sensor according to the present invention will be described in detail below with reference to the drawings.

The embodiment shown in FIGS. 1 to 4 is one in which the present invention is applied to a registration adjusting device for performing registration adjustment of a three-plate CCD color video camera.

G-1. Configuration of Registration Adjusting Device In the registration adjusting device in this embodiment, as shown schematically in FIG. 1, the master lens 20 has a registration measuring test chart 10 on which a predetermined test pattern is formed. It is arranged in front of. The registration measurement test chart 10
The image pickup light of the test pattern is guided to the color separation prism 30 of the three-plate CCD color video camera through the master lens 20, and the color separation prism 30 converts the image pickup light into three primary color lights R, G, B, that is, red. Component light R, green component light G, and blue component light B are separated into three CCs.
The D image sensors 31r, 31g, 31b are irradiated. Each CCD image sensor 31
The r, 31g, and 31b are attached to position adjusting jigs 40r, 40g, and 40b for performing six-dimensional alignment, respectively. Then, each CCD image sensor 31
r, 31g, and 31b are driven by a CCD drive circuit 51 that operates based on a reference signal provided by a reference signal generator 50, and an image, that is, a test, by the imaging light of each color component separated by the color separation prism 30. Image the pattern. Each CCD image sensor 31r, 31
The image pickup outputs obtained by g and 31b are output from the preamplifiers 41r, 41g, and 41b to the gate circuits 42r and 41r, respectively.
It is supplied to the matrix circuit 43 via 42g and 42b. Here, each of the gate circuits 42r, 42g, 42b
Is supplied with a gate pulse generated by the gate pulse generating circuit 52 that operates based on the reference signal.

The image output signal obtained by the matrix circuit 43 is
The high-resolution monitor 46 is supplied to the oscilloscope 44 for observing waves and also through the video signal processing circuit 45.
It is supplied to the microcomputer 48 via the digitizer 47.

G-2. Configuration of Registration Measurement Test Chart The above registration measurement test chart 10 comprises:
As schematically shown in FIG. 2, the CCD image sensor 3
Double the pitch 2τc for one picture element pitch τc
.Tau.p = 2.tau.c. +-.. DELTA., Which is shifted by .DELTA.p1 ...

Here, Δ is the value of the CCD image sensor 31 so that the image pickup output by the CCD image sensor 31 includes n beat components in one horizontal scanning period (1H) as shown in FIG. 3, for example. It is set to Δ = nτcτp / τo (n is an arbitrary number of 1 or more), where τo is the effective image size in the pixel array direction.

The registration measuring test chart 10 in this embodiment has a vertical striped repeating pattern PTsh in which light and shade are repeated along the horizontal center line Lsh, as the test pattern is schematically shown in FIG.
And two vertical striped repeating patterns PTah, PT which are arranged symmetrically with respect to the horizontal center line Lsh and which are parallel to each other.
bh and two horizontal striped repeating patterns PTav and PTbv which are symmetrically arranged with the center line Lsv in the vertical direction sandwiched therebetween.
What is formed is used.

Here, each of the vertical striped repeating patterns PTsh, PT
The ah and PTbh are formed so as to repeat the light and shade at the repeating pitch τph which has the relationship of the above-mentioned first equation with respect to the horizontal picture element pitch τch of the CCD image sensor 31.
In addition, the horizontal striped repeating patterns PTav, PTbv
Is the vertical pixel pitch τ of the CCD image sensor 31.
Repetition pitch τ that has the relationship of the above-mentioned first equation with respect to cv
It is formed to repeat the light and shade in pv.

In this embodiment, for the CCD image sensor of two types of picture element arrays corresponding to the CCIR and EIA standards, one test chart is shared so that registration measurement can be performed. , EIA standards are arranged in parallel.

Registration measurement test chart 1 as described above
The image pickup output obtained by the CCD image sensor 31 irradiated with the image pickup light of the test pattern by 0 is the repeating pitch τp of the repeating pattern PT and each pixel pitch τ.
A moire pattern is generated based on the difference from c, and the signal level changes as shown in FIG. 2 according to the relative position between the repeating pattern PT and each picture element S. That is, the imaging output for the horizontal repeating pattern PTh includes the fourth
As shown in the figure, one horizontal scanning period (1E) includes n beat components.

The amplitude of the beat component included in the imaging output signal obtained by imaging the repetitive pattern of the registration measuring test chart 10 by the CCD image sensor 31 has the amplitude of the back focus of the imaging optical system and the amount of tilt of the solid-state imaging device. That is, it changes depending on the registration error in the ± Z direction and the ± RX and ± RY directions described above, and the phase thereof changes in the center position and rotation of the solid-state image sensor, that is, in the ± X direction and the arrow ± Y.
Direction and ± RZ direction depending on the registration error.

G-3. Therefore, in this embodiment, in this embodiment, the CCD image sensors 31r, 31g, 31b mounted on the position adjusting jigs 40r, 40g, 40b of the registration adjusting device are mounted.
The driving state, the repeating pattern of the test chart 10 for installation measurement is imaged, and each CCD
With respect to the imaging output obtained by the image sensors 31r, 31g, 31b, each beat component is determined by the oscilloscope 4 described above.
Waveform observation by 4 or the above microcomputer 4
While performing waveform analysis with 8, position adjustment jigs 4
By operating 0r, 40g, 40b, the above Z
The registration adjustment in the direction, that is, the back focus adjustment is performed as follows.

That is, in this back focus adjustment, each CCD image sensor 31r,
With respect to the imaging output signal obtained by imaging the repetitive pattern of the registration measurement test chart 10 by 31g and 31b, vertical stripes in which light and shade are repeated along the horizontal center line Lsh schematically shown in FIG. The image output of the central portion AS of the repeating pattern PTsh is selectively taken out by each of the gate circuits 42r, 42g and 42b. That is, the image pickup output of the central portion of the image pickup screen, which is less affected by the axial aberration and the chromatic magnification aberration of the image pickup optical system, is taken out. The amplitude of the beat component included in the image output of the central portion AS changes depending on the registration error in the ± Z directions, that is, the back focus of the image pickup optical system, and the CCD image sensors 31r, 31g, 3
It becomes maximum when 1b is at the just focus position.

Therefore, while observing the waveform of the beat component included in the image output of the central portion AS with the oscilloscope 44, the position adjusting jigs 40r, 40g, 40b are operated to perform the beat shown in FIG. Each CCD image sensor 31r, 3 up to the position where the partial amplitude of the antinode of the component becomes maximum
By moving 1g and 31b, each CCD image sensor 31r, 31g and 31b can be adjusted to the position of just focus, that is, back focus adjustment.

The back focus adjustment is performed by setting the diaphragm of the image pickup optical system to an open state to reduce the depth of focus so that the CCD image sensors 31r and 31 are passed through the master lens 20.
The registration measurement test chart 10 is imaged by g and 31b.

In this embodiment, after the above-mentioned back focus adjustment, each CCD image sensor 31r, 31g, 3
1b, two vertical striped repeating patterns PT which are symmetrically arranged on both sides Ba and Bb of the vertical striped repeating pattern PTsh of the registration adjustment test chart 10 and the horizontal center line Lsh are parallel to each other.
Using the change in the amplitude of the beat component included in each image output of each of the central portions Cu and Cd of ah and PTbh, horizontal and vertical tilt adjustments are performed, and the vertical striped repeating patterns PTah and PTbh are further adjusted. The central portions D of the central portions Cu, Cd and the horizontal striped repeating patterns PTav, PTbv
Rotation adjustment and center adjustment in the horizontal and vertical directions are performed by using the change in the phase of the beat component included in each imaging output of a and Db, so that all the registration adjustments in the above six-axis directions can be performed with extremely high accuracy. Can be completed with.

H. EFFECTS OF THE INVENTION As is clear from the above description of the embodiments, in the solid-state image sensor back focus adjustment method according to the present invention, at least solid-state imaging is performed when adjusting the back focus of a plurality of solid-state image sensors that capture the same image. It is a repetitive pattern in which light and shade are repeated horizontally or vertically at a position corresponding to the center of the image pickup screen of the device, and the repetitive pitch has a predetermined relationship with the pixel pitch in the horizontal or vertical direction of the solid-state image pickup device. A beat component based on the difference between the picture element pitch and the repeating pitch included in each imaging output of the repeating pattern corresponding to the central portion of the image by each solid-state imaging device, which is captured by each solid-state imaging device through the imaging lens. Is detected, the respective solid-state image pickup elements are moved in the optical axis direction of the image pickup lens, and the detection output of the beat component is By fixing each solid-state image sensor at the position where it becomes maximum, the back focus of each solid-state image sensor can be adjusted with high accuracy by a simple operation, and the intended purpose can be sufficiently achieved. it can.

[Brief description of drawings]

1 to 4 are drawings showing an embodiment of a registration adjusting device to which the present invention is applied, and FIG. 1 is a block diagram schematically showing the configuration of the registration adjusting device of this embodiment. FIG. 2 is a schematic diagram for explaining the relationship between the test pattern of the registration measurement test chart and the pixel array of the CCD image sensor in the above embodiment, and FIG. 3 is the resist used in the above embodiment. FIG. 4 is a schematic diagram showing the configuration of a registration measurement test chart, and FIG. 4 is a waveform diagram showing a beat component included in an imaging output obtained by imaging a test pattern of the registration measurement test chart with a CCD image sensor. Is. FIG. 5 is an external perspective view of a CCD image sensor for explaining the adjustment operation direction in general registration adjustment. 10 ... Test chart 20 ... Master lens 31r, 31g, 31b ... CCD image sensor

Claims (1)

[Claims] 1. When adjusting the back focus of a plurality of solid-state image pickup devices for picking up the same image, at least a position corresponding to the center of the image pickup screen of the solid-state image pickup device is repeated in a horizontal or vertical shading pattern in a repeating pattern. Then, an image whose repeating pitch has a predetermined relationship with the horizontal or vertical picture element pitch of the solid-state image sensor is captured by each solid-state image sensor through the imaging lens, and the center of the image by each solid-state image sensor is captured. The beat component based on the difference between the picture element pitch and the repeating pitch included in each imaging output of the repeating pattern corresponding to the part is detected, and each solid-state imaging device is moved in the optical axis direction of the imaging lens, Back focus of the solid-state image sensor in which the above solid-state image sensors are fixed at positions where the detection output of the beat component becomes maximum Settling method.