JP2770521B2 - Focus position detection method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus position detection method used for an imaging device having a line sensor.

[Conventional technology]

Conventionally, as a focus position detection method of this type of imaging apparatus, there is a method of maintaining a stable focus position with respect to an environment such as a temperature, and an apparatus that performs focus adjustment based on data of a movement amount of a focus position with respect to an environment acquired in advance. . There have also been methods of manually adjusting the image while viewing the image in real time, and confirming the focal position by statistical processing of image data for different targets. However, in the conventional example, the focus position confirmation sensor and the image pickup sensor are configured to be shared.

[Problems to be solved by the invention]

In the above-described conventional focus position detection method, since only correction and manual adjustment for environmental condition changes around the focus position detector are performed, there are the following disadvantages.

(1) It cannot be used for a radiometer whose focus position fluctuates sensitively to environmental conditions or the environment.

(2) Since the sensor is shared when a manual and a different target are used, a long time is required for confirming the focal position, and when a shift occurs, it is not clear whether the shift occurs before or after. .

[Means for solving the problem]

The focus position detection method of the present invention is a focus position detection method of an imaging device having a line sensor that captures incident light in a direction perpendicular to the moving direction of a continuously moving object. A prism to be divided, a line sensor that captures incident light in a direction parallel to the moving direction of the object, and a wedge glass with a drive unit that changes the focal position of the incident light between the prism and the line sensor. Have.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

1 and 2 are a configuration diagram and an operation example perspective view of an embodiment of the present invention, and FIGS. 3 and 4 are characteristic diagrams for explaining the embodiment.

In FIG. 1 and FIG. 2, at the time of normal imaging, light from an imaged object is condensed by a condensate meter 1, passes through a prism 2, a flat glass 3, and forms an image on a line sensor 4 for imaging. Here, when the radiometer, which is an imaged object, moves in the traveling direction 10, the signal photoelectrically converted by the imaging line sensor 4 is connected in the dotted line direction of the switch 8, and is input to the signal processing circuit 9 for processing. As a result, a band-shaped two-dimensional image is obtained. Note that this two-dimensional image is a two-dimensional image perpendicular to the direction of travel 10 corresponding to the projected view 12 of the imaging sensor in FIG.
On the other hand, the light split by the hatched portion of the prism 2 shown in FIG. 2 passes through the wedge glass 5 for confirming the focal position and is imaged by the line sensor 6 for detecting the focal position. The image formed by the line sensor 6 is a projection of the detection sensor on the imaged object.
13 corresponds to the moving direction 10 of the radiometer as an object to be imaged, and the same image is picked up so as to move on the line sensor 6 in each imaging cycle with the movement of the radiometer. When checking the focal position, the switch 8 is connected to the line sensor 6 (solid line in the figure) and input to the signal processing circuit 9. Under such conditions, one of the two wedge glasses 5 is gradually moved by the wedge glass drive unit 7 to change the thickness of the wedge glass 5 in the optical path. Here the line sensor 6
Is set to be the same as the imaging position of the imaging line sensor 4. When the wedge glass 6 is moved one pixel at a time in the image obtained by the signal processing circuit 9, if the focus position is shifted, the line sensor 6 is moved.
Output changes stepwise for each pixel of the pixel number as shown in FIG. In the focused state, the output of the line sensor 6 does not change while the light from the imaged object remains constant as shown in FIG. 4, and the incident light from the radiometer changes at the edge 11 of the imaged object. However, the subsequent pixels have the same and constant output. By adjusting the focal position of the light collector based on such characteristic data, accurate focus adjustment can be performed.

The wedge glass drive unit 7 and the focus position adjustment of the concentrator 1 are performed in conjunction with each other, so that simple and single-time focus adjustment is possible.

〔The invention's effect〕

As described above, the present invention is not limited to the imaging system, and is provided with a line sensor parallel to the moving direction of the image receiving the light split by the prism, and a function of changing the focal position by moving the wedge glass. By performing imaging while changing the focal position to
There is an effect that the focal position can be detected. Further, by arranging the line sensor in parallel to the moving direction, the object that can be used as an edge can be a small object, and there is an effect that the object can be easily selected.

[Brief description of the drawings]

FIG. 1 is a structural view of an embodiment of the present invention, FIG. 2 is a perspective view of the present embodiment, and FIGS. 3 and 4 show states of pixel signals of the present embodiment. It is explanatory drawing of a state and the state where the focus position was adjusted. 1 ... concentrator, 2 ... prism, 3 ... flat glass, 4
…… Line sensor for imaging, 5… Wedge glass, 6…
Line sensor 7, wedge glass drive unit 8, switchover unit 9, signal processing circuit 10, imaging system traveling direction 11,
... Edge of the imaged object, 12... Projection of the imaging line sensor, 13... Projection of the line sensor 6.

Claims (1)

(57) [Claims] 1. A prism for dividing a part of light from incident light to be imaged in a focus position detection method of an image pickup apparatus having a line sensor for imaging incident light in a direction perpendicular to a moving direction of a continuously moving object. A line sensor that captures incident light in a direction parallel to the moving direction of the object, and a wedge glass with a drive unit that changes the focal position of the incident light between the prism and the line sensor. Characteristic focus position detection method.