JPH03220515A - Focus position detection system - Google Patents

Abstract

PURPOSE:To facilitate focus position confirmation by providing wedgelike glass fitted with a driving part which varies the focus position of incident light between a prism and a line sensor. CONSTITUTION:Light which is split by the hatched part of the prism 2 is transmitted through the wedgelike glass 5 for focus position confirmation to form an image through the line sensor 6 for focus position detection. The formed image of this line sensor 6 corresponds to the projection drawing 13 of the sensor for detection on a picked-up body and is parallel to the moving direction 10 of a radiometer as the image pickup body, and the image is so picked up so that the same image in each image pickup cycle moves on the line sensor 6 as the radiometer moves. In such a case, the wedgelike glass driving part moves one of two wedgelike glass plates 5 gradually to vary the thickness of the wedgelike glass 5 in the optical path. Consequently, the image formation position on the line sensor 6 is set equally to the image formation position of an image pickup line sensor 4. Consequently, the focus position can accurately be detected in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focal position detection method used in an imaging device having a line sensor.

[Conventional technology]

Conventionally, regarding the focus position detection method of this type of imaging device, there are methods that maintain a stable focus position in response to environments such as temperature, and devices that adjust the focus based on previously acquired data on the amount of movement of the focus position relative to the environment. . There have also been methods in which manual adjustments are made while viewing images in real time, and methods in which the focal position is confirmed through statistical processing of image data for different targets. However, in the conventional example, the sensor for confirming the focus position and for capturing the image are commonly used.

[Problem to be solved by the invention]

The above-described conventional focus position detection method only requires correction and manual adjustment for changes in environmental conditions around the focus position detector, and therefore has the following drawbacks.

(1> Cannot be used in harsh environmental conditions or in radiometers whose focal position changes sensitively depending on the environment.

(2) Since the sensor is shared when using manual and different targets, it takes a long time to confirm the focus position, and when a shift occurs, it is unclear whether it is shifted forward or backward. It is.

[Means to solve the problem]

The focus position detection method of the present invention is a focus position detection method for an imaging device that has a line sensor that images incident light in a direction perpendicular to the moving direction of a continuously moving object. A dividing prism, a line sensor that captures an image of 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 explained with reference to the drawings.

FIG. 3 and FIG. 2 are block diagrams of one embodiment of the present invention and perspective views showing an example of operation, and FIGS. 3 and 4 are characteristic diagrams illustrating the present embodiment.

1 and 2, during normal imaging, light from an object to be imaged is collected by a concentrator 1, transmitted through a prism 2 and a flat glass 3, and focused on an imaging line sensor 4 to form an image. Here, when the radiometer, which is the imaging object, moves in the traveling direction 10, the signal photoelectrically converted by the imaging line sensor 4 is connected to the dotted line direction of the switch 8, and is input to the signal processing circuit 9 and processed. As a result, a band-shaped two-dimensional image is obtained. Note that this two-dimensional image corresponds to the projection view 12 of the imaging sensor in FIG. 2, and is a two-dimensional image perpendicular to the direction of travel 10. On the other hand, the light divided by the hatched portion of the prism 2 shown in FIG. 2 passes through the wedge glass 5 for focal position confirmation, and is imaged by the line sensor 6 for focal position detection. The image formed by the line sensor 6 corresponds to the projection diagram 13 of the detection sensor on the object to be imaged, and the moving direction 10 of the radiometer, which is the object to be imaged.
As the radiometer moves, the same image is captured moving on the line sensor 6 at each imaging cycle. When checking the focus position, switch 8 is switched to line sensor 6.
Connect to Tun+1 (solid line in the figure) and signal processing area 11@
Enter 9. Under these conditions, the wedge glass drive unit 7 gradually moves one of the two wedge glasses 5.
to change the thickness of the wedge glass 5 in the optical path. Here, the imaging position of the line sensor 6 is set to be the same as the imaging position of the imaging line sensor 4. Now, when the wedge glass 6 is moved pixel by pixel of the image obtained by the signal processing circuit, if the focal position is shifted, the output of the line sensor 6 will change to the pixel number as shown in Figure 3. It changes stepwise for each pixel. In addition, in the focused state, the output of the line sensor 6 does not change as long as the light from the imaged object changes as shown in Figure 4, but the incident light from the radiometer changes at the edge 1 of the imaged object At that point, the output changes suddenly, but after that, the output of the pixels remains the same and constant. Accurate focus adjustment becomes possible by adjusting the focus position of the condenser based on such characteristic data.

By linking the wedge glass drive unit 7 and the focus position adjustment of the condenser 1, simple and single-time focus adjustment is also possible.

〔Effect of the invention〕

As explained above, the present invention has an in-sensor parallel to the moving direction of the image that receives light split by a prism, and a function to change the focal position by moving a wedge glass, in addition to the imaging system. By performing imaging while changing the focal position, there is an effect that the focal position can be detected with high accuracy in a short time. Furthermore, by placing the line sensor parallel to the moving direction, a small object can be used as an edge, which has the effect of making it easier to select the object.

[Brief explanation of drawings]

FIG. 1 shows the i-factor of one embodiment of the present invention, FIG. 2 is a perspective view of this embodiment, and FIGS. 3 and 4 show the states of pixel signals of this embodiment, each with a shifted focus position. FIG. 3 is an explanatory diagram of a state in which the focal position is aligned. Engineering: Concentrator, 2: Prism, 3: Flat glass, 4: Imaging line sensor, 5: Wedge glass, 6: Line sensor, 7: Wedge glass drive Part, 8...Switcher, 9...Signal processing circuit, 10...
Direction of movement of the imaging system, 11...Edge of the object to be imaged, ■2...
- Projected view of the imaging line sensor, 13... Projected view of the line sensor 6.

Claims (1)

[Claims] In a focal position detection method of an imaging device having a line sensor that images incident light in a direction perpendicular to the moving direction of a continuously moving object, the object includes a prism that splits part of the light from the incident light to be imaged; a line sensor that captures an image of incident light in a direction parallel to the direction of movement of the prism; and a wedge glass with a drive unit that changes the focal position of the incident light between the prism and the line sensor. Detection method.